Galileo Project
By:
Albert Van Helden
Galileo Project
By:
Albert Van Helden
Online:
< http://cnx.org/content/col10234/1.1/ >
CONNEXIONS
Rice University, Houston, Texas
This selection and arrangement of content as a collection is copyrighted by Albert Van Helden. It is licensed under
the Creative Commons Attribution 1.0 license (http://creativecommons.org/licenses/by/1.0).
Collection structure revised: July 7, 2004
PDF generated: October 25, 2012
For copyright and attribution information for the modules contained in this collection, see p. 135.
Table of Contents
The Biography of Galileo Galilei . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1 Galileo
1.1 Introduction to Galileo Galilei . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Galileo's Education . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Galileo's Patrons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.4 Important Places . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2 Galileo's Family
2.1 Vincenzo Galileo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.2 Maria Celeste . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.3 Marina Gamba . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3 Science
3.1 Scientists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.2 Institutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.3 Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.4 Observations, experiments, and discoveries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
3.5 Theories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 101
4 Christianity
4.1 The Inquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
4.2 Church Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
Attributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
iv
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1
The Biography of Galileo Galilei
Galileo's Early Life
Galileo was born in Pisa, Italy (Section 1.4.2) on February 15, 1564. His father, Vincenzo Galilei (Section 2.1),
was a musician. Galileo's mother was Giulia degli Ammannati. Galileo was the rst of six (though some
people believe seven) children. His family belonged to the nobility but was not rich. In the early 1570's, he
and his family moved to Florence (Section 1.4.1).
The Pendelum
n 1581, Galileo began studying at the University of Pisa, where his father hoped he would study medicine.
While at the University of Pisa, Galileo began his study of the pendulum (Section 3.3.3) while, according
to legend, he watched a suspended lamp swing back and forth in the cathedral of Pisa. However, it was not
until 1602 that Galileo made his most notable discovery about the pendulum - the period (the time in which
a pendulum swings back and forth) does not depend on the arc of the swing (the isochronism). Eventually,
this discovery would lead to Galileo's further study of time intervals and the development of his idea for a
pendulum clock.
On Motion
In 1581, Galileo began studying at the University of Pisa, where his father hoped he would study medicine.
While at the University of Pisa, Galileo began his study of the pendulum while, according to legend, he
watched a suspended lamp swing back and forth in the cathedral of Pisa. However, it was not until 1602
that Galileo made his most notable discovery about the pendulum - the period (the time in which a pendulum
swings back and forth) does not depend on the arc of the swing (the isochronism). Eventually, this discovery
would lead to Galileo's further study of time intervals and the development of his idea for a pendulum clock.
Mechanical Devices
In 1592, Galileo was appointed professor of mathematics at the University of Padua. While teaching there,
he frequently visited a place called the Arsenal, where Venetian ships were docked and loaded.
Galileo
had always been interested in mechanical devices. Naturally, during his visits to the Arsenal, he became
fascinated by nautical technologies, such as the sector (Section 3.3.4) and shipbuilding.
In 1593, he was
presented with the problem involving the placement of oars in galleys. He treated the oar as a lever and
correctly made the water the fulcrum. A year later, he patented a model for a pump (Section 3.3.1). His
pump was a device that raised water by using only one horse.
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Family Life
Galileo was never married. However, he did have a brief relationship with Marina Gamba (Section 2.3), a
woman he met on one of his many trips to Venice. Marina lived in Galileo's house in Padua where she bore
him three children. His two daughters, Virginia and Livia, were both put in convents where they became,
respectively, Sister Maria Celeste (Section 2.2) and Sister Arcangela. In 1610, Galileo moved from Padua
to Florence where he took a position at the Court of the Medici family (Section 1.3.2).
Vincenzio, with Marina Gamba in Padua.
He left his son,
In 1613, Marina married Giovanni Bartoluzzi, and Vincenzio
joined his father in Florence.
Telescope
Galileo invented many mechanical devices other than the pump, such as the hydrostatic balance (Section 3.3.2).
But perhaps his most famous invention was the telescope (Section 3.3.6).
Galileo made his
rst telescope in 1609, modeled after telescopes produced in other parts of Europe that could magnify objects three times.
He created a telescope later that same year that could magnify objects twenty times.
With this telescope, he was able to look at the moon (Section 3.4.1), discover the four satellites of Jupiter
(Section 3.4.3), observe a supernova, verify the phases of Venus, and discover sunspots (Section 3.4.2). His
discoveries proved the Copernican system (Section 3.5.1) which states that the earth and other plaqnets revolve around the sun. Prior to the Copernican system, it was held that the universe was geocentric, meaning
the sun revolved around the earth.
The Inquisition
Galileo's belief in the Copernican System (Section 3.5.1) eventually got him into trouble with the Catholic
Church. The Inquisition (Section 4.1.1) was a permanent institution in the Catholic Church charged with
the eradication of heresies.
A committee of consultants declared to the Inquisition that the Copernican
proposition that the Sun is the center of the universe was a heresy. Because Galileo supported the Copernican
system, he was warned by Cardinal Bellarmine (Section 4.2.2), under order of Pope Paul V, that he should
not discuss or defend Copernican theories. In 1624, Galileo was assured by Pope Urban VIII (Section 1.3.4)
that he could write about Copernican theory as long as he treated it as a mathematical proposition. However,
with the printing of Galileo's book,
Dialogue Concerning the Two Chief World Systems,
Galileo was called
to Rome in 1633 to face the Inquisition again. Galileo was found guilty of heresy for his Dialogue, and was
sent to his home near Florence where he was to be under house arrest for the remainder of his life. In 1638,
the Inquisition allowed Galileo to move to his home in Florence, so that he could be closer to his doctors.
By that time he was totally blind. In 1642, Galileo died at his home outside Florence.
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Chapter 1
Galileo
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1.1 Introduction to Galileo Galilei
Galileo was born in Pisa, Italy on February 15, 1564. His father, Vincenzo Galilei, was a musician. Galileo's
mother was Giulia degli Ammannati. Galileo was the rst of six (though some people believe seven) children.
His family belonged to the nobility but was not rich. In the early 1570's, he and his family moved to Florence.
Galileo was never married. However, he did have a brief relationship with Marina Gamba, a woman he
met on one of his many trips to Venice. Marina lived in Galileo's house in Padua where she bore him three
children. His two daughters, Virginia and Livia, were both put in convents where they became, respectively,
Sister Maria Celeste and Sister Arcangela. In 1610, Galileo moved from Padua to Florence where he took
a position at the Court of the Medici family. He left his son, Vincenzio, with Marina Gamba in Padua. In
1613, Marina married Giovanni Bartoluzzi, and Vincenzio joined his father in Florence.
1.2 Galileo's Education
2
1.2.1 Collegio Romano
In 1534 Ignatius de Loyola and six companions bound themselves in vows of poverty, chastity, and apostolic
labors. Six years later, Pope Paul III recognized the order as the Society of Jesus and authorized the framing
of a detailed constitution. Rather than turning away from daily life in the tradition of monastic orders, the
Jesuits formulated their mission in the world at large, and specically in three areas, teaching, service to the
nobility, and missionary work in foreign lands. In all three areas they were extraordinarily successful, but
almost from the start they made their greatest mark in education. By 1556, when the Society had about a
thousand members, three-fourths were engaged in education in 46 colleges. In 1579 there were 144 colleges,
and by 1626 444 colleges, 56 seminaries, and 44 houses of training for Jesuits.
seminaries stood the Collegio Romano, founded by Ignatius in 1551.
At the apex of all Jesuit
By papal bulls of 1552 and 1556 it
received the right to grant doctorates in philosophy and theology as well as the privileges enjoyed by the
universities of Paris, Louvain, Salamanca, and Alcalà. By 1567 the Collegio Romano had over a thousand
students, and Pope Gregory XIII erected a large building to house the students and faculty. Over the years
the college gradually became known as the Gregorian University in honor of that pope.
Although the mathematical sciences occupied a subservient role in the curriculum, they did have a role.
In the ratio studiorum (curriculum rules) promulgated in 1566, we nd the following:
Concerning mathematics, the mathematician shall teach, in this order, the [rst] six books of
Euclid, arithmetic, the sphere [of Sacrobosco], cosmography, astronomy, the theory of the planets,
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the Alphonsine Tables, optics, and timekeeping. Only the second year philosophy students shall
hear his lecture, but sometimes, with permission, also the students of dialectics. - [][1]
Over the next four decades, Christoph Clavius (Section 3.1.13) promoted the dignity of the mathematical
(i.e. scientic) subjects and produced a series of textbooks that dened Jesuit scientic education not only
in the Collegio Romano but in all Jesuit colleges. The inuence of Jesuit mathematical education was felt in
non-Jesuituniversities as well. It has been shown over the past two decades that Galileo's lecture notes from
his days as a student at the university of Pisa had as their ultimate source the lectures of the mathematicians
at the Collegio Romano.
The Collegio Romano attracted the best scientists in the Society, and Jesuit educators as far away as
China turned to them for their judgment on scientic matters. In 1610 there were four mathematicians on
the faculty, Christoph Clavius (Section 3.1.13), Christoph Grienberger, Paolo Lembo, and Odo van Maelcote.
It is to these four men that other Jesuits and high church ocials turned for a verdict on the new phenomena
Galileo claimed to have discovered with his telescope (Section 3.3.6).
1.2.2 Accademia dei Lincei
Figure 1.1:
3
Federico Cesi
The Cesi family belonged to the high aristocracy of Rome and the Papal States. It originated in the little town
of Cesi, near Rome, and its wealth derived largely from high oces connected with the church. (Frederico
Cesi's paternal uncle, Bartolomeo Cesi, became a cardinal.)
At the turn of the seventeenth century, its
wealth was being eroded (like that of similar Roman families) by the ruinous expense of keeping up their
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"life-style of the rich and famous." The many titles held by members of the family were mostly empty honors
with little or no economic signicance.
Cesi, son of Federico Cesi (hereditary Marquis of Monticello and Duke of Acquasparta, and later made a
prince by Pope Paul V) and Olimpia Orsini, was born in Rome in 1585. He was educated privately and at
an early age became interested in natural science. He was convinced, however, that nature should be studied
directly, not through the lter of Aristotelian philosophyan idea that was being enunciated by a growing
number of learned men, among whom the most inuential voice was to become that of Francis Bacon.
Cesi's father was strongly opposed to the career direction in which these studies were taking young
Federico, but his mother (herself from a wealthy and powerful Roman family, the Orsini) provided him with
both moral and nancial support.
Figure 1.2:
Coat of Arms
In 1603, at age eighteen, Cesi founded the Accademia dei Lincei, the Lyncean Academy. Its name came
from Lynceus, the argonaut of Greek mythology renowned for his sharpness of sight. Its initial members
were Cesi, the mathematician Francesco Stelluti, the physician Johannes Eck from the Low Countries, and
the
polymath
Anastasio De Fillis.
The members lived communally and almost monastically in Cesi's
house, where he provided them with books and laboratory equipment.
In a 1605 document, the goals of
the academy were stated to be "not only to acquire knowledge of things and wisdom, and living together
justly and piously, but also peacefully to display them to men, orally and in writing, without any harm."
Cesi devoted the rest of his life to these goals and his academy.
The Lyncean Academy was steadfastly opposed by Cesi's father and other Roman aristocrats. Its members were accused of black magic, opposition to Church doctrine, and living a scandalous life.
Eck was
forced to leave Rome, and for some time the membership of the academy was scattered. Cesi kept in close
contact with all of them through correspondence. During a stay in Naples, Cesi came to know the
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Giambattista della Porta, and he considered setting up a branch of the academy in that city. Porta became
a member of the academy in 1610.
The most famous member of the academy was Galileo, who was inducted in the spring of 1611, during
his visit to Rome. The academy's most celebrated publications were those of Galileo, rst his
Sunspots
Letters on
in 1613, and then his Assayer in 1623. After Galileo's induction, the membership grew rapidly,
and at its height the Lyncean Academy had 32 members, including many in foreign countries.
Cesi's academy was very much a personal academy. Its impetus and funds came from him exclusively.
When, in 1630, he died suddenly, his academy died with him. Galileo was just beginning the tedious process
of obtaining a license for his
Dialogue Concerning the Two Chief World Systems,
and the plan had been for
the academy to sponsor the book and pay for the printing costs.
1.3 Galileo's Patrons
1.3.1 Duke of Mantua, Vincenzo Gonzaga (1562-1612)
4
The City of Mantua, located in the northern Italian plain (see map), had for centuries been a center of
cloth manufacture. The wealth of the city made possible a brilliant court culture under the Gonzaga. This
family had ruled the city since 1329, initially as "Captains General of the People," and since 1530 as Dukes.
Because of the city's wealth and the Gonzaga support of arts and letters, the Mantua court became one of
the most brilliant in Italy.
At the turn of the seventeenth century, Mantua was in economic decline. Although Vincenzo Gonzaga
was still one of the great patrons in Italy, his spendthrift habits were accelerating the decline of the city, and
after his death in 1612 Mantua ceased being an important cultural center.
Vincenzo Gonzaga had been tutored in the mathematical subjects by Giuseppe Moletti, Galileo's predecessor in the chair of mathematics at the University of Padua. During the winter of 1603-1604, Galileo
visited the Mantuan court in an eort to obtain a position there. He was oered a salary of 300 ducats per
year plus living expenses for himself and a servant. At this time Galileo's salary at the University of Padua
was 320 ducats, and he had further income from his boarding students. He therefore requested instead a
salary of 500 ducats with an expense account for himself and two servants. No terms could be worked out,
and Galileo retained his post in Padua. But for one of his proportional compasses (no doubt an especially
ornate one) and his instruction manual, the Duke did give Galileo a gold chain with a medal, and two silver
dishes. It was the custom that the medal could not be sold but that the chain and the cups could. In his
account books for 1604 Galileo put down the chain for 900 lire and the cups for 440 lire.
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1.3.2 The Medici Family
Figure 1.3:
The Medici Coat of Arms
The Medici family of Florence can be traced back to the end of the 12th century.
It was part of the
patrician class, not the nobility, and through much of its history the family was seen as the friends of the
common people.
Through banking and commerce, the family acquired great wealth in the 13th century,
and political inuence came along with this wealth.
At the end of that century, a member of the family
served as gonfaliere, or standard bearer (high ceremonial oce) of Florence. In the 14th century the family's
wealth and political inuence increased until the gonfaliere Salvestro de' Medici led the common people in
the revolt of the ciompi (small artisanate). Although Salvestro became the de facto dictator of the city, his
brutal regime led to his downfall and he was banished in 1382. The family's fortune then fell until it was
restored by Giovanni di Bicci de' Medici (1360-1429)
6 , who made the Medici the wealthiest family in Italy,
perhaps Europe. The family's poltical inuence again increased, and Giovanni was gonfaliere in 1421.
Giovanni's son, Cosimo (1389-1464), Cosimo il Vecchio (the old or rst Cosimo), is considered the real
founder of the political fortunes of the family. In a political struggle with another powerful family, the Albizzi,
Cosimo initially lost and was banished, but because of the support of the people he was soon recalled, in
1434, and the Albizzi were banished in turn. Although he himself occupied no oce. Cosimo ruled the city
as uncrowned king for the rest of his life. Under his rule Florence prospered.
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Figure 1.4:
Cosimo il Vecchio
Cosimo spent a considerably part of his huge wealth on charitable acts, live simply, and cultivated
literature and the arts. He amassed the largest library in Europe, brought in many Greek sources, including
the works of Plato, from Constantinople, founded the Platonic Academy and patronized Marsilio Ficino,
who later issued the rst Latin edition of the collected works of Plato. The artists supported by Cosimo
included Ghiberti, Brunelleschi, Donatello, Alberti, Fra Angelico, and Ucello. During his rule and that of
his sons and grandson, Florence became the cultural center of Europe and the cradle of the new Humanism.
Cosimo's son Piero (1416-1469) ruled for just a few years but continued his father's policies while enjoying
the support of the populace.
Piero's sons, Lorenzo (1449-1492) and Giuliano (1453-1478) ruled as tyrants, and in an attack in 1478
Giuliano was killed and Lorenzo wounded. If the family fortunes dwindled somewhat and Florence was not
quite as prosperous as before, under Lorenzo, known as the Magnicent, the city surpassed even the cultural
achievements of the earlier period. This was the high point of the Florentine Renaissance: Ficino, Giovanni
Pico della Mirandola, Boticelli, Michelangelo, etc. But Lorenzo's tyrranical style of governing and hedonistic
lifestyle eroded the goodwill of the Florentine people. His son Piero (1472-1503) ruled for just two years.
In 1494, after accepting humiliating peace conditions from the French (who had invaded Tuscany), he was
driven out of the city and died in exile. For some time, Florence was now torn by strife and anarchy and, of
7 .
course, the rule of Savanarola
Upon the defeat of the French armies in Italy by the Spanish, the Spanish forced Florence to invite
the Medici back. Piero's younger brother Giuliano (1479-1516) reigned from 1512 to 1516, and became a
prince; he was followed by Lorenzo (1492-1519), son of Piero, who was named Duke of Urbino by Pope
Leo X (himself a Medici, son of Lorenzo the Magnicent); and upon Lorenzo's death, Giulio (1478-1534),
the illigitimate son of Lorenzo the Magnicent's brother Giuliano, became rule of the city but abdicated in
1523 in favor of his own illegitimate son, Alessandro (1510-1537), to become Pope Clement VII. Alessandro
became hereditary Duke of Florence.
If the rulers since Lorenzo the Magnicent had been weak and ineective, this changed when Cosimo I
(1519-1574) ascended the throne in 1537 at the age of 18. Cosimo was a descendant not of Cosimo il Vecchio
but from Cosimo's brother. He quickly consolidated his power, and under his rule Tuscany was transformed
into an absolutist nation state.
Although politically ruthless, Cosimo was highly cultured and promoted
letters and arts as well as the Tuscan economy and navy. He founded the Accademia della Crusca, a body
charged with the promotion of the Tuscan language (which has become the standard Italian of today), the
Accademia del Disegno (Academy of Design), renewed the university of Pisa, and conquered Siena and Lucca.
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Figure 1.5:
Cosimo I
In 1569 Cosimo was named Grand Duke of Tuscany.
He set the style for the new absolute rule by
concentrating the administration of Florence in a new oce building, the Uzi (where he also began a small
museum for art works; the entire Uzi is now a museum), and moving his residence across the river to the
Pitti Palace, bought in 1549 and enlarged and remodeled several times by Cosimo and his descendants. He
built a private corridor between the Pitti Palace and the Palazzo Vecchio in the city, where the government
met.
Vincenzo Galilei (Section 2.1) moved his family, including the ten-year old Galileo, from Pisa to
Florence in the year of Cosimo's death.
Cosimo's son, Francesco I (1541-1587) was an ineectual ruler under whom Tuscany languished.
His
younger brother, Ferdinand (1549-1609), who had been made a cardinal at the age of fteen, became Grand
Duke upon Francesco's death in 1587.
Ferdinand II was a capable administrator under whom Tuscany
ourished again.
Ferdinand was an admirer of Tomasso Campanella and tried to protect him as best he could. He was
interested in scientic matters, and had a great
armillary sphere
constructed by Antonio Santucci, his
cosmographer.
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(a)
Figure 1.6:
(b)
(a) Ferdinand I (b) Armillary Sphere of Santucci
Ferdinand appointed Galileo to the professorship of mathematics at the university of Pisa in 1588. In
the year of his accession, Ferdinand married Christina of Lorraine (1565-1637), who was the grand daughter
of Catherine de' Medici, Queen of France. Christina was well-disposed to Galileo and as a favor in return
for some services rendered by Galileo when he was still in Padua found a position for his brother in law
Benedetto Landucci. It was to Christina that Galileo later wrote his letter on science and scripture, "Letter
to the Grand Duchess Christina of Lorraine."
Ferdinand and Christina had four sons and four daughters.
The eldest son, Cosimo II, ascended the
throne upon his father's death in 1609. Galileo had tutored Cosimo in mathematics during some summers,
and therefore the young Grand Duke knew him well and admired him enough to oer him a court position
in 1610, after Galileo had dedicated
Sidereus Nuncius
to him and his family. After a bout of fever, in 1615,
Cosimo's health deteriorated, and he died in 1620.
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Figure 1.7:
Christina of Lorraine
Figure 1.8:
Cosimo II
Cosimo's son, Ferdinand II (1610-1670) was just ten years old when he became Grand Duke, and until
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CHAPTER 1. GALILEO
12
his majority the government was carried on by the two Grand Duchesses, Cosimo's mother Christina of
Lorraine, and Cosimo's wife, Maria Magdalena of Austria, the sister of the Holy Roman Emperor Ferdinand
II.
Figure 1.9:
Ferdinand II
During the outbreak of the plague, in 1630, Ferdinand distinguished himself, but he was not a strong
ruler and was unable to protect Galileo from the Inquisition (Section 4.1.1) in 1633.
In 1657, together
with his brother Leopold, Ferdinand established the Accademia del Cimento, or Academy of Experiment,
a forerunner of more permanent scientic academies, such as the Royal Society of London (1665) and the
Royal French Academy of Sciences (1666). The Accademia del Cimento stopped functioning in 1667.
The Florentine and Tuscan economy had been slowly stagnating since the end of the sixteenth century.
Under Ferdinand II, his son, Cosimo III (1642-1723), and his grandson, Gian-Gastone (1671-1737), the city
country slipped into insignicance.
Cosimo III's rule was one of incompetence and religious intolerance.
Gian-Gastone's rule was too short to repair the damage.
In 1735, an arrangement was made between
Austria, France, England, and the Netherlands that a swap should be made with Lorraine going to France
and Tuscany to Austria in return. In 1737 Austrian troops occupied Tuscany. One of Gian Gastone's last
acts was to erect a memorial to Galileo in the church of Santa Croce and to inter Galileo remains there.
During the transference, several parts of Galileo's skeleton were taken as relics by various people. One of
Galileo's ngers is now housed in the Museum of History of Science in Florence.
Gian-Gastone had no male heir, and the House of Medici died with him.
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Figure 1.10:
Maria (Marie), Queen of France
The Medici family dominated Florentine politics for two and a half centuries and presided over a cultural
achievement that is equalled only by Athens in the golden age. The family also got its genes mixed with
those of most royal families in Europe. Medici women included Catherine (1519-1589) who married Henry II,
King of France and ruled the coutry after her husband's death; Maria (1573-1642) married Henry IV, King
of France. Maria's daughters became queens of Spain and England. Cosimo II's wife, Maria Magdalena, was
the sister of Ferdinand II, Holy Roman Emperor.
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14
1.3.3 Paolo Sarpi
Figure 1.11:
8
Paolo Sarpi9
Pietro (his birth name) Sarpi was born in Venice, the son of Francesco Sarpi, a struggling merchant from San
Vito (northwest of the city), and Isabella Morelli a Venetian from a good family. Francesco died young, and
young Pietro was educated by his mother's brother, a priest and school master, and then by Fra Giammaria
Capella, a monk in the Servite Order.[1] In 1566, at the age of fourteen, Pietro was received in the Servite
Order and took the name of Paolo. By the time he was ordained a priest, in 1574, Sarpi was an immensely
learned monk, trained in philosophy, theology, mathematics, Greek, and Hebrew. His rst assignment was
as an assistant to Cardinal Carlo Borromeo in Milan. He was recalled to Venice a few years later and rose
rapidly in the Servite Order. In 1579 he became
Provincial of Venice and was chosen as one of three Servite
scholars to revise the constitution and rule of the Order.
In connection with this task, Sarpi spent some
time in Rome to study the decrees of the Council of Trent. Here he became friends with Robert Bellarmine
10
(Section 4.2.2), although later they became opponents. Back in Venice, Sarpi became Procurator General
of the Venetian province of the Order in 1584 and served as Vicar-General from 1599 to 1604. He lived in
quiet retirement in his monastery, performing his religious tasks and pursuing his private studies.
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Figure 1.12:
Paolo Sarpi
Beginning in the 1590s, disputes between Rome and the Venetian Republic over jurisdictional issues
became frequent. As a result Paul Paul V put the Republic under interdict in 1606, forbidding the clergy
to perform their usual oces. Venice ordered the clergy to disobey the papacy and expelled the orders that
did not do so, including the Jesuits. Sarpi, who was a patriot, sided with the Republic against the Pope
and became Venice's ocial theologian in that year. He refused to obey a summons to come to Rome and
in 1607 was wounded by assassins widely thought to be sent by the Pope.
Sarpi published a number of
books on jurisdictional issues (including the rst history of the Council of Trent), taking a strictly historical
approach. He carried on a wide correspondence with scholars and diplomats, including heretics. Although
it has been claimed that he had sympathies for Protestants, it is perhaps more appropriate to say that he
was against religious excesses and the secular powers claimed by the Pope.
Sarpi was a friend and benefactor of Galileo. He rst acquainted his friend with the reports from the
Netherlands about devices for seeing faraway (telescopes (Section 3.3.6)) and facilitated Galileo's oer of an
eight-powered spyglass to the Venetian government (and the reward) in 1609. Galileo and Sarpi discussed
and corresponded about various other subjects, including magnets, the tides (Section 3.4.5), and the law of
falling bodies.
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1.3.4 Urban VIII
Figure 1.13:
11
Urban VIII
The Barberini were a powerful family, with branches in Rome and Florence (Section 1.4.1), which had
produced several
cardinals up to that point.
Maeo was born into the Florentine branch of the family in
1568. His father died when Maeo was only three years old; his mother insisted that he be educated by the
Jesuitsrst in Florence,
and later in Rome at the Jesuit Collegio Romano (Section 1.2.1). Here he lived
with his uncle, Francesco Barberini, who held the high church oce of
Protonotary Apostolic.
In 1589
he took the degree of doctor of law from the University of Pisa.
papal legate to the court
archbishop of Nazareth (an oce he obviously fullled in
Maeo Barberini' s rise in the church hierarchy was rapid. In 1601 he served as
of Henri IV, king of France; in 1604 he became
absentia since the Holy Land was under Moslem rule) and took up the post of papal nuncio (lit. messenger,
the papal legate permanently accredited to a civil government) to the French king; in 1606 he was made a
bishop
synod, completed the construction of one seminary and built
two others, and served as legate of Bologna and prefect of the Segnatura di Giustizia. Upon the death of
cardinal with the titular church of St. Peter in Montorio and later St. Onofrio; in 1608 he became
of Spoleto. As bishop, Barberini convened a
Pope Gregory XV, in1623, Maeo Barberini was elected Pope, taking the name of Urban VIII.
During his long papacy, Urban VIII promoted missionary work. He formed
dioceses and vicariats in
various missionary terrritories and founded a college for the training of missionaries. He also repealed the
monopoly on missionary work in China and Japan given to the Jesuits in 1585, opening these countries to
missionaries of all orders. In 1639 he prohibited slavery among the Indians of Brazil, Paraguay, and the West
Indies.
During this period the temporal power of the papacy was in greatest danger from the Hapsburg dynasty
which ruled much of the German speaking region of Europe, the Southern Netherlands, and Spain. Spanish
inuence in Italy has been on the rise for a century, and the kingdom of Naples and Sicily, under Spanish
rule, lay immediately to the South of the Papal State. For this reason, Urban VIII favored the anti-Hapsburg
policy of the French, neglecting to support the catholic cause in Germany.
Urban VIII saw to it that the Barberini family beneted from his papacy. His brother and two nephews
were made cardinals and given high church oces. Other family members were helped by the Pope in the
acquisition of property and titles . He even went so far as to make war on Parma, Tuscany (Section 1.4.1),
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Modena, and Venice over a matter of protocol involving his nephew-cardinals.
Pope Urban strenghtened
fortications and armaments in the papal territories. He lavishly supported artists, chief among whom was
Giovanni Lorenzo Bernini, who beautied St. Peter's cathedral. Urban had the bronze supporting girders
of the Roman Pantheon melted down and made into cannon and and other objects.
This prompted the
epigram: " What the barbarians did not do the Barberini's did."
Maeo Barberini was an accomplished man of letters, who published several volumes of verse.
Upon
Galileo' s return to Florence, in 1610, Barberini came to admire Galileo' s intelligence and sharp wit. During
a court dinner, in 1611, at which Galileo defended his view on oating bodies, Barberini supported Galileo
against Cardinal Gonzaga. From this point, their patron-client relationship ourished until it was undone
in 1633.
Upon Barberini' s ascendance of the papal throne, in 1623, Galileo came to Rome and had six
interviews with the new Pope. It was at these meetings that Galileo was given permission to write about
the Copernican theory (Section 3.5.1), as long as he treated it as a hypothesis.
Galileo' s
Dialogue Concerning the Two Chief Systems of the World,
After the publication of
in 1632, the patronage relationship was
broken. It appears that the Pope never forgave Galileo for putting the argument of God's omnipotence (the
argument he himelf had put to Galileo in 1623) in the mouth of Simplicio, the staunch Aristotelian whose
arguments had been systematically destroyed in the previous 400-odd pages. At any rate, the Pope resisted
all eorts to have Galileo pardoned.
1.4 Important Places
12
1.4.1 Florence and Tuscany
Figure 1.14:
Florence
Tuscany is located in the western part of the boot of Italy (Section 1.4.2), north of Rome and south of Genoa.
It is bounded by the Apennines to the North and East and by the Mediterranean on the West. Its land area
is about 9,000 square miles. Its major cities are Florence, Pisa, Siena, Lucca, Arezzo, and Pistoia. Its major
river is the Arno, on which Florence and Pisa are located.
It was the home land of the Etruscans, which was annexed by Rome in 351 BC. After the fall of the
Roman empire, the region, which became known as Tuscany (Toscana in Italian) came under the rule of
a succession of rulers (Herulians, Ostrogoths, etc.)
and emerged as a political entity with its own rulers.
By the twelfth century the Tuscan cities were gradually gaining their independence as republics and forcing
the nobility to live in the cities. By the high Middle Ages the cities of Pisa, Siena, Arezzo, Pistoia, Lucca,
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CHAPTER 1. GALILEO
18
and especially Florence had become wealthy because of textile manufacture, trade, banking, and agriculture.
Gradually Florence came to overshadow and conquer all other cities in the region.
After several experiments with representative government, Florence was ruled by an oligarchy of wealthy
aristocrats, among whom the Medici (Section 1.3.2) family became dominant in the fteenth century. Under
the patronage of these wealthy families the arts and literature ourished as nowhere else in Europe. Florence
was the city of such writers as Dante, Petrarch, and Macchiavelli, and artists and engineers such as Boticelli,
Brunelleschi (who built the magnicent dome on the church of St. Mary of the Flowers), Alberti, Leonardo
Da Vinci, and Michelangelo.
Because of its dominance in literature, the Florentine language became the
literary language of the Italian region and is the language of Italy today.
Lorenzo de' Medici, who ruled
Florence in the late fteenth century was perhaps the greatest patron of the arts in the history of the West.
But times changed.
After Lorenzo the friar
Savonarola
ruled Florence, and the Medici were exiled.
With the shift of commerce away from the Mediterranean and toward the Atlantic, after 1492, the economy
of Tuscany went into a slow decline. In 1530 the Holy Roman Emperor Charles V conquered Florence and
reestablished the Medici family in power.
They were now dukes of Florence, and within a few decades
Cosimo de Medici was made Grand Duke of Tuscany.
Cosimo aggressively pursued a policy of economic
revival, building the great harbor at Livorno because the harbor of Pisa had silted up.
Galileo was born under the rule of Cosimo in 1564.
It was during this period that the Medici court
increasingly rmly established its hold over the city. The court came to dominate all aspects of civic life,
and for the Galilei family the route to success lay through the patronage structure in which the Court was
central.
In the seventeenth century Florence and Tuscany increasingly faded into obscurity and did not
revive until the nineteenth century. It is today a major cultural center and attracts millions of tourists each
year.
13
1.4.2 Italy
Figure 1.15:
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After the fall of the Roman Empire, the peninsula of Italy was not again politically unied until the nineteenth
century. The region emerged from the so-called Dark Ages as an unorganized group of city states. Historically
the most important of these were Venice (wealthy because of its trade with the Middle East) and Milan
(an important manufacturing center) in the North, Florence (Section 1.4.1) (a center of commerce and
manufacturing) and the Papal States in the center, and Naples and Sicily in the South. There were also
many smaller and less important city states, such as Mantua, Genoa, and Verona.
During the high Middle Ages, ca.
1000-1450, the Italian region was economically and culturally the
most advanced in Europe. Its wealth was based on trade with the Near East bringing spices, silk, and other
desired Eastern commodities into Europe; manufacture, especially of nished cloth (Florence) and armaments
(Milan), and banking. Italy's wealth attracted the attention of foreigners, and for several centuries there
was a contest between the papacy and the Holy Roman (German) Empire to control the region, but neither
side succeeded.
It is in the city states, Florence chief among them, that Italian art, architecture, letters, and engineering
ourished as never before, but in the long run these states were too small to be viable in a world increasingly
dominated by the new, larger, nations states.
As the city states emerged independent from both Pope and Emperor, at the end of the Middle Ages,
their never ending wars and intrigues against each other opened the door to other foreign intervention. Italy
now became the victim of the ambitions of the new nation states of France and Spain. Sicily and Naples came
under the rule of Spain and remained there until the nineteenth century, while Milan and Florence fell under
the inuence of France. Perhaps the most symbolic event was the sack of Rome by the troops of the Emperor,
Charles V, in 1527.
Moreover, with the voyages of Columbus and Vasco da Gama (partially nanced by
Italian capital) the economic center of Europe shifted away from the Mediterranean to the Atlantic coast.
The new economic powers were, rst, Portugal and Spain, and then France, the Netherlands, and England.
Beginning in the sixteenth century, then, Italy began to slip with respect to Northern Europe, and by the
end of the seventeenth century it had become a region of secondary economic and cultural importance.
During the Middle Ages the papal monarchy had claimed to be a supraregal political power (a claim the
Popes did not give up until recently): the Pope claimed political primacy over counts, dukes, kings, and
even the emperor. This struggle ended disastrously when the papacy was captured by the French king and
moved to Avignon, where it remained from 1302 to 1378. From that date until 1417 there were, in fact, two
popes, one in Rome and one in Avignon, and for a brief period, 1409-1415, there were three! With a single
pope now again established in Rome, the papacy entered a period of unparalleled venality. The Renaissance
popes were, it seemed at times, more interested in their pet projects in art and architecture or the careers
of their relatives than in the well being of the Catholic Church. Reform was slow in coming. The occasion
of the start of the Protestant Reformation, in 1517, was the selling of indulgences to raise money for the
building of the cathedral of St. Peter in Rome.
There was, in Italy, a crisis of condence in the sixteenth century. Many sought law, order, and security;
republics fell, princes became more powerful; authority and titles were stressed (even if the latter had to be
made up). The papal court became more Italian, and the Popes themselves gathered more and more power
onto themselves, taking it away from the cardinals and bishops. At the same time the Church girded its
loins for the battle against the Protestants. In 1540 Ignatius of Loyola founded the Society of Jesus, an order
which owed obedience to the Pope; intermittently, from 1545 to 1563, the Council of Trent met and made a
number of important pronouncements on the issues that separated the Protestants from the Catholic church.
By the end of the sixteenth century the church was regaining territories that it had lost to Protestants.
The intellectual climate at this time was rather more restricted than it had been in earlier centuries.
Orthodoxy was enforced; heterodoxies were combated. Giordano Bruno (Section 4.2.1), an apostate monk
who espoused the Copernican system (Section 3.5.1) and the innitude of worlds (and inhabitants) was
burned at the stake in 1600. It was in this climate that Galileo argued for the Copernican theory.
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CHAPTER 1. GALILEO
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Chapter 2
Galileo's Family
2.1 Vincenzo Galileo
1
Vincenzo Galilei was born in Florence (Section 1.4.1). He made his living as a lutenist, composer, theorist,
singer, and teacher. Around 1560 he settled in Pisa, where Galileo Galilei was born in 1564, the oldest of six
or seven children. During this period Galilei also studied for some time in Venice under the theorist Gioseo
Zarlino, with whom he later had a dispute about music theory. In the early 1570s Galilei and his family
settled in Florence. His prowess as a musician and theorist attracted a number of powerful patrons, and he
often spent time at their residences. e.g., in 1578-79 with Duke Albrecht of Bavaria in Munich.
Vincenzo Galilei published a number of books of musical scores for the lute and several books on musical
theory. What is important about Galilei for our purposes is that he combined the practice and theory of
music. Since antiquity, the theory of music had consisted of a mathematical discussion of harmony, in other
words what are the mathematical ratios of the lengths of strings producing consonances, and how does one
divide the octave? It had always been thought that not only was the ratio of lengths of two strings sounding
an octave 2:1, but that so also was the ratio of the tensions of strings of equal lengths tuned an octave apart.
Galilei showed that this is not the case: the ratio of tensions is 4:1. He found that ratio by hanging weights
from strings. Here was an experiment that produced numbers and bore directly on the age-old theoretical
discussions.
Stillman Drake argued that Galilei performed these experiments in 1588, when his son Galileo was living
at home and giving private lessons in mathematics.
The implication here is that young Galileo actually
helped in the experiments. Be that as it may, Galileo received from his Florentine environment in general
and from his father in particular the tendency to combine practical considerations with theory and to try to
answer theoretical questions by experiment.
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CHAPTER 2. GALILEO'S FAMILY
22
2.2 Maria Celeste
2
Figure 2.1
3
Virginia, Galileo's oldest child, was born in Padua on 12 August 1600. Her mother, Marina Gamba , was
Galileo's housekeeper. When Galileo moved to Florence (Section 1.4.1), in 1610, he took Virginia and his
other daughter, Livia (1601-1659), with him, leaving his son Vincenzio (only four years old) with his mother
for a few years.
After he had settled in Florence, Galileo decided to put his two daughters in a convent for life. It took
several years to make the arrangements. Not the least problem was that the girls were too young to make
this important decision for themselves.
Through the oces of Cardinal Maeo Barberini (Section 1.3.4),
one of his admirers, Galileo obtained dispensation on this score, and in 1613 both girls were placed in the
convent of San Matteo in nearby Arcetri, where the abbess was the sister of the secretary of the grand duke
of Tuscany. Virginia took the veil in 1616, choosing the name of Sister Maria Celeste, and Livia followed the
same course a year later, becoming Sister Arcangela.
Little is known about the life of Sister Maria Celeste until 1623, but about 120 letters to her father,
written from 1623 to 1634 have survived. From these the picture of a loving daughter, always solicitous of
her father's well being, emerges. Her letter to her father of 21 November 1623 is typical:
Most Illustrious Lord Father,
I cannot rest any longer without news, both for the innite love I bear you, and also for fear lest
the sudden cold, which in general disagrees so much with you, should have caused a return of
your usual pains and other complaints. I therefore send the man who takes this letter purposely
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to hear how you are, and also when you expect to set out on your journey I have been extremely
busy at the dinner-napkins. They are nearly nished, but now I come to putting on the fringe,
I nd that of the sort of which I send you a sample, a piece is wanting for two dinner-napkins:
that will be four braccia. I would be glad if you could let me have it immediately, so that I may
send you the napkins before you go; as it was for this that I have been making such haste to get
them nished.
As I have no cell of my own to sleep in, Sister Diamanta kindly allows me to share hers, depriving
herself of the company of her own sister for my sake. But the room is so bitterly cold that with
my head so infected, I do not know how I shall remain well, unless you can help me by lending
me a set of those white bed-hangings which you will not want now. I would be glad to know if
you can do me this service. Moreover, I beg you to be so kind as to send me that book of yours
which has just been published, so that I may read it, for I have a great desire to see it.
These few cakes I send are some I made a few days ago, intending to give them to you when you
came to bid us adieu. As you departure is not so near as we feared, I send them lest they should
get dry. Sister Arcangela is still under medical treatment, and is much tried by the remedies. I
am not well myself, but being so accustomed to ill health, I do not make much of it, seeing, too,
that it is the Lord's will to send me continually some such little trial as this. I thank Him for
everything, and pray that He will give you the highest and best felicity. And nally, with all my
heart, I greet you in the name of me and Sister Arcangela.
From San Matteo, the 21st of November 1623
Your most aectionate daughter Sister Maria Celeste Galilei
If you have collars to whiten, you can send them.
The convent of San Matteo was very poor. The nuns did not have the wherewithal to feed themselves
and keep the buildings in repair. Maria Celeste wrote to her father that the bread was bad, the wine sour
and that they ate ox meat. Galileo helped repair windows and personally took charge of keeping the convent
clock in good repair. Maria Celeste often had to appeal to her father for help, and she was chronically ill.
She bore her ill health with dignity and courage, and managed to be a great comfort to her father.
worked constantly to mitigate the diculties between Galileo and her brother Vincenzio.
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24
Figure 2.2
In 1631 Galileo bought the villa "Il Goiello" in Arcetri, near the convent. From this house he could see
San Matteo and hear its bells.
It was here that he spent his nal years under house arrest.
Part of the
sentence that Galileo received in 1633 read as follows: "As a salutary penance we impose on you to recite the
?
seven penitential Psalms once a week for the next three years."[ ] Sister Maria Celeste took it upon herself
to perform this penance for him. She died, however, on 2 April 1634, less than four months after Galileo's
return to Arcetri.
4
2.3 Marina Gamba
During one of his frequent trips to Venice, Galileo met a young woman named Marina di Andrea Gamba,
with whom he entered into a relationship. Marina Gamba moved into Galileo's house in Padua and bore him
three children, Virginia (1600), later Sister Maria Celeste (Section 2.2), Livia (1601), later Sister Arcangela,
and Vincenzio (1606). In none of the three baptismal records is Galileo named as the father. In the case of
Virginia, she was described as "daughter by fornication of Marina of Venice," with no mention of the father;
on Livia's baptismal record the name of the father was left blank; and on Vinzenzio's baptismal record
?
"father uncertain."[ ]The domestic situation was, apparently, a happy one, except when Galileo's mother,
Giulia, visited.
When Galileo left Padua for good to take up his position at the Medici (Section 1.3.2) court in Florence
(Section 1.4.1), in 1610, he took the two daughters with him but left Marina Gamba behind with Vincenzio,
who was then only four years old.
Vincenzio joined Galileo in Florence a few years later.
In 1613 Ma-
rina Gamba married Giovanni Bartoluzzi. It appears that Galileo kept cordial relations with Gamba and
Bartoluzzi.
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Galileo put his two daughters in a convent. He managed to have Vincenzio legitimated by the Grand
Duke of Tuscany. The reason for this unequal treatment is probably that Galileo would not be able to provide
suciently large doweries for his daughters to allow them to make marriages appropriate to his stature at
the Medici court. He would have no such nancial obligation to his son.
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Chapter 3
Science
3.1 Scientists
1
3.1.1 Hans Lipperhey
Hans Lipperhey was born in Wesel (western Germany) and settled in Middelburg, the capital of Zeeland,
the southwesternmost province of the Netherlands, where he married in 1594 and became a citizen in 1602.
His craft was that of spectacle-maker. Middelburg was a ourishing city, especially after the fall of Antwerp
to the Spanish in 1585, which caused many of its Protestant inhabitants to ee north to the Netherlands.
Figure 3.1:
Minute of Lipperhey's patent application [138].
New glass-making techniques were introduced here by Italians in the 1590s, and perhaps some ideas
about combining lenses were abroad in this glass-making community.
Although others have claimed the
invention of the telescope (Section 3.3.6) and the device was impossible to keep secret, the earliest record
of the existence of such a device is a letter of the government of Zeeland to its delegation to the States
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CHAPTER 3. SCIENCE
28
General of the Netherlands, dated 25 September 1608, which instructs them to be of help to the bearer,
"who claims to have a certain device by means of which all things at a very great distance can be seen as
if they were nearby, by looking through glasses which he claims to be a new invention."
2 On 2 October
the States General discussed Lipperhey's application for a patent on the instrument. Although the patent
was eventually denied because it was felt that the device could not be kept a secret, Lipperhey made several
binocular telescopes for the States General and was paid handsomely for his services.
Shortly after that, the States General were also petitioned by Jacob Metius of Alkmaar, a city in the
north of the Netherlands, who also claimed to be the inventor. The claim of yet a third person, Sacharias
Janssen, also a spectacle-maker in Middelburg, emerged several decades later. The surviving records are not
sucient to decide who was the actual (or as it was put in the seventeenth century, the rst) inventor of the
telescope. All we can say is that Lipperhey's patent application is the earliest record of an actually existing
telescope.
3.1.2 Santorio Santorio
Figure 3.2:
3
Santorio Santorio
Santorio Santorio's father, Antonio Santorio, was a nobleman from Friuli in the service of the Venetian
republic; his mother was from a noble family in Justinopolis (now Koper), where Santorio was born.
He
was educated in Justinopolis and then Venice, and then (1575) entered the University of Padua, where he
received his M.D. degree in 1582, at the age of 21.
From 1587 to 1599 Santorio spent time in Croatia as the personal physician of a local nobleman.
In
1599 he set up a medical practice in Venice. Here he became part of the circle of learned men that included
Galileo. In 1611 he was appointed to the chair of theoretical medicine at the University of Padua, and he
taught there until his retirement in 1624. He spent the remainder of his life in Venice.
2 Van Helden, The Invention of the Telescope, p. 36.
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29
Although in treating his patients Santorio did not stray far from Hippocratic and Galenic practice (based
on the notion of a balance of the uids, or "humors"), in his theory and method of investigation he diered
from the classical authors a great deal. Rather than relying on authority in the rst instance, as so many of
his colleagues still did, Santorio argued that one should rst rely on sense experience, then on reasoning, and
only lastly on authority. His most famous experiments involve the study of bodily weight. He placed himself
on a platform suspended from an arm of an enormous balance, and weighed his solid and liquid intake and
excretion. He found that by far the greatest part of the food he took in was lost from the body through
perspiratio insensibilis, or "insensible perspiration." The little book in which he published these ndings,
De Statica Medicina, or "Concerning Static Medicine," made him famous throughout Europe.
Rather than describing the body and its functions in terms of Aristotelian (and Galenic) elements and
qualities, Santorio argued throughout his career that the fundamental properties were mathematical ones,
such as number, position, and form. The body was like a clock, the workings of which were determined by
the shapes and positions of its interlocking parts. This was a radical break with traditional medical theory
and natural philosophy, in which the discourse was about qualities and essences (what is it that makes an
apple an apple, or a liver a liver?), and in which mathematical properties such as size and position were
considered accidental because they gave no information about the essence of an object. Santorio now made
these accidental properties central to his view of nature and medicine. Further, while the central metaphor
of Aristotelian natural philosophy and Galenic medicine had been organic, Santorio made it mechanical: the
clock (or, more generally, the machine) became the metaphor for nature.
His passion for describing phenomena in terms of numbers, led Santorio to invent several instruments,
among which a wind gauge, a water current meter, the "pulsilogium," and a thermoscope. The last two of
these are also mentioned by Galileo, and, especially in the case of the thermoscope, there has been controversy
about who the actual inventor was. We do know that Santorio was the rst to apply a numerical scale to
the thermoscope, which later evolved into the thermometer. Both the pulsilogium and the thermoscope are
perhaps best seen as the product of a learned circle in Venice that included Galileo, Santorio, Giofrancesco
Sagredo, and fra Paolo Sarpi (Section 1.3.3).
4
3.1.3 Tommaso Campanella
Figure 3.3:
4 This
Tommaso Campanella5
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Giovan Domenico Campanella, born in Stilo, Calabria (southern tip of the Italian peninsula), was a child
prodigy. At the age of fourteen, he entered the
Dominican order and took the name Tommaso.
His formal
training in philosophy and theology was in Dominican houses. Early in his career he became disenchanted
with Aristotelian philosophy and became a follower of Bernardino Telesio (1509-1588), whose great work
Rerum Natura
De
(after Lucretius, see atomism (Section 3.5.3)) inuenced him greatly. Telesio thought that
all knowledge is sensation and that intelligence is therefore an collection of isolated data provided by the
senses. For this his books were placed on the Index of Forbidden Books (Section 4.1.2) after his death. But
Telesio's philosophy, so inuential in the south of Italy, pointed the way to empiricism. In 1592 Campanella
published
Philosophia Sensibus Demonstrata,
or "Philosophy Demonstrated by the Senses," in defense of
Telesio.
In Naples, in 1589, Campanella came into contact with Giambattista della Porta, a
polymath who was
the center of a diverse group of thinkers who dabbled in experiments, white magic, and astrology. Campanella
here was exposed not only to primitive experiments, but also to astrology. His thoughts had now drifted so
far from Dominican orthodoxy, that he was denounced to the Inquisition (Section 4.1.1) and, in 1592, he
was for a time conned in a convent. For the next seven years he led a
peripatetic life, until in 1599 he was
imprisoned in Naples for joining a movement to expel the Spanish from Naples and Sicily. He spent 27 years
in prison in Naples, and then, upon his release, was jailed in Rome until 1629. During these imprisonments
he often lived under the worst conditions and was tortured several times. After living in Rome for ve years,
where he advised Pope Urban VIII (Section 1.3.4) on astrological matters, he ed to France in 1634, where
he lived his life out peacefully under the protection of Cardinal Richelieu.
Campanella wrote on a wide range of subjects, from Telesian philsophy to political philosophy and
astrology. In 1622 he published his
Apologia pro Galileo
("Defense of Galileo") in which he defended the
Copernican system (Section 3.5.1) and the separate paths of Scripture and nature to knowledge of the
Creator. He argued that truth about nature is not revealed in Scripture and claimed freedom of thought in
philosophical speculation. His writings were inuential not because of any scientic discoveries but because
of animistic, empirical interpretation of nature. Campanella was a great admirer of Galileo and corresponded
with him for many years. In his animistic, Neo-Platonic, astrological approach to nature he was, however,
very dierent from the much more practical Florentine.
6
3.1.4 Johannes Fabricius
David Fabricius was a Lutheran pastor and astronomer in the little town of Osteel, East Frisia (northwest
Germany). He was a correspondent of Johannes Kepler (Section 3.1.7) and the discoverer of the rst known
variable star (1596). Early in 1611, his son Johannes, a university student, returned from the Netherlands
with one or more telescopes, and he and his father turned these instruments to the heavens. On 9 March,
at dawn, Johannes directed the telescope at the rising sun and saw several dark spots on it. He called his
father, and together the two investigated this new phenomenon.
They directed their instruments to the
edge of the Sun, and when their eyes adjusted to the brightness slowly moved toward the Sun's center. This
method was, of course, very painful, and the two quickly switched to the projection method by means of a
camera obscura.
Over the next several months they tracked spots as they moved across the Sun's face and found that a
dozen or so days after they had disappeared from the western edge of the Sun they reappeared on the eastern
edge. Johannes wrote a tract on sunspots (Section 3.4.2),
cum Sole Conversione Narratio
De Maculis in Sole Observatis, et Apparente earum
("Narration on Spots Observed on the Sun and their Apparent Rotation with
the Sun"), the dedication of which was dated 13 June 1611. It was printed in Wittenberg (the site of the
premier Lutheran university, where Johannes was apparently continuing his studies) in time for the autumn
book fair in Frankfurt. In the tract Johannes rehearsed the observations made by him and his father, without
giving times or dates or showing a picture of the spots, and then stated his opinion that they were on the
Sun and that the Sun therefore probably rotated on its axis (an notion already suggested by Giordano Bruno
5 http://cnx.org/content/m11982/latest/campanella.gif
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(Section 4.2.1) and Johannes Kepler (Section 3.1.7).
Johannes's style was orid, and only a small part of the tract actually dealt with his observations and
didently stated conclusions. Because of the lack of a powerful patron interested in scientic matters who
might have called the little book to the attention of inuential people, it drew very little attention, and
by the time e.g., Kepler had become aware of its existence the book was eclipsed by Christoph Scheiner's
(Section 3.1.14) rst publication on sunspots (January 1612). Johannes's didence may have been caused
by a disagreement with his father about the nature of sunspots. In December 1611, David Fabricius wrote to
Michael Maestlin (Kepler's old teacher) that he did not believe the spots were on the Sun's body, although
the center of their motions clearly lay in the Sun. Neither father nor son were important participants in the
1612/13 debate on the nature of sunspots.
Little else is known about Johannes Fabricius, except that he died in 1616, at the young age of 29. A
year later the father was killed when an irate peasant, whom he had accused of stealing a goose, hit him
over the head with a shovel.
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3.1.5 Marc Welser
Figure 3.4:
7
Marc Welser
The Welser family was an old patrician family of Augsburg (southern Germany) and one of the wealthiest
in Germany. His uncle, Bartholomeus had been an advisor to the Emperor Charles V and is said to have
lent him twelve tons of gold. In 1528 Bartholomeus sent a eet to the New World and established a colony
in Venezuela, which was taken over by the Spanish in 1555.
Marc Welser was sent to Rome at the age of 16 and became a very ne scholar of Greek and Latin; he also
became uent in Italian and studied antiquities. Upon his return to Augsburg, he became a lawyer and in
1592 became a member of the Senate of that city. He was elected the Senate's Council. His passion, however,
was history, antiquities, and philology, and he corresponded on these subjects with the foremost scholars in
Europe. He published books on the antiquities of Italy and Augsburg, on martyrs of the early church, and
early German history. He also prepared an edition of Emperor Frederick II's (13th century) book
Art of Hunting with Birds,
7 This
and published several editions of hitherto unpublished Greek sources.
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On the
33
Among Welser's correspondents were a number of Jesuit scholars, such as Christoph Clavius.
It was
Clavius who assured Welser that Galileo's telescopic discoveries were real. At the end of 1611, the Jesuit
mathematician Christoph Scheiner (Section 3.1.14), wrote three letters on sunspots to Welser, and Welser
published them early in 1612 at his own press. He sent Galileo a copy of the tract asking for his opinion.
Galileo's responses and Scheiner's second tract on the subject were published by the Lyncean Academy
(Section 1.2.2) in 1613 under the title
Istoria e Dimostrazioni intorno alle Macchie Solari e loro Accidenti
("History and Demonstrations concerning Solar Spots and their Properties").
Welser was elected at this
time to the Lyncean Academy. After a long and very painful battle with gout, he died in 1614. His collected
works (the introduction to which is the source of virtually all information about his life) were published in
1682.
8
3.1.6 Benedetto Castelli
Figure 3.5:
Benedetto Castelli
Antonio Castelli was born in Brescia, Italy, in 1578 and took the name Benedetto upon entering the
dictine order
Bene-
in 1595. From perhaps 1604 to 1607 he lived in a monastery in Padua and studied under
Galileo. Upon receiving a copy of
Sidereus Nuncius,
in Brescia in 1610, he applied for a transfer to Florence
(Section 1.4.1), where he arrived in 1611. Castelli helped see Galileo's
Discourse on Floating Bodies
through
the press and published the reply (largely written by Galileo) to the polemics against it. Castelli was also
active in the initial stages of Galileo's sunspot (Section 3.4.2) research in 1612, coming up with the method
of projecting the Sun's image through the telescope.
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Upon Galileo's recommendation, Castelli was appointed professor of mathematics at the university of Pisa
in 1613. When the court was visiting Pisa, late that year, Castelli was invited to dinner and became involved
in a lengthy after-dinner discussion about the merits of the Copernican System (Section 3.5.1).
Castelli
presented Galileo's arguments about reconciling the Copernican theory with certain biblical passages, e.g.
in the book of Joshua. It was this occasion that prompted Galileo to write a long letter to Castelli on the
subject of science and religion, which was later expanded into the
Letter to the Grand Duchess Christina.
Both versions of the letter circulated in manuscript, and the Letter to the Grand Duchess was printed in
Strasbourg in 1636.
Castelli moved to Rome in 1626 to become a consultant to the Pope on the management of rivers in
the Papal States (a perennial problem) and professor of mathematics at the university of Rome. In 1628 he
published the important work on hydraulics,
Della Misura dell'Acque Correnti,
or "On the Measurement of
Running Waters," a book that may be considered the foundation of modern hydrodynamics. Castelli also
made important discoveries about illumination (independently formulating the photometric law), vision,
after-images, and diaphragms in telescopes. He was also a pioneer in the study of dierential absorption of
heat by dierent colors. To the end, he was a faithful friend of Galileo.
9
3.1.7 Johannes Kepler
Figure 3.6:
Johannes Kepler
Johannes Kepler was born in Weil der Stadt in Swabia, in southwest Germany. His paternal grandfather,
Sebald Kepler, was a respected craftsman who served as mayor of the city; his maternal grandfather, Melchior
Guldenmann, was an innkeeper and mayor of the nearby village of Eltingen. His father, Heinrich Kepler, was
"an immoral, rough and quarrelsome soldier," according to Kepler, and he described his mother in similar
unattering terms. From 1574 to 1576 Johannes lived with his grandparents; in 1576 his parents moved to
nearby Leonberg, where Johannes entered the Latin school. In 1584 he entered the Protestant seminary at
Adelberg, and in 1589 he began his university education at the Protestant university of T\x{00FC}bingen.
Here he studied theology and read widely. He passed the M.A. examination in 1591 and continued his studies
as a graduate student.
Kepler's teacher in the mathematical subjects was Michael Maestlin (1580-1635). Maestlin was one of
the earliest astronomers to subscribe to Copernicus's heliocentric theory, although in his university lectures
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35
he taught only the Ptolemaic system. Only in what we might call graduate seminars did he acquaint his
students, among whom was Kepler, with the technical details of the Copernican system (Section 3.5.1).
Kepler stated later that at this time he became a Copernican for "physical or, if you prefer, metaphysical
reasons."
In 1594 Kepler accepted an appointment as professor of mathematics at the Protestant seminary in Graz
(in the Austrian province of Styria).
He was also appointed district mathematician and calendar maker.
Kepler remained in Graz until 1600, when all Protestants were forced to convert to Catholicism or leave the
province, as part of
Counter Reformation measures.
For six years, Kepler taught arithmetic, geometry
(when there were interested students), Virgil, and rhetoric. In his spare time he pursued his private studies
in astronomy and astrology. In 1597 Kepler married Barbara Muller. In that same year he published his
rst important work,
The Cosmographic Mystery,
in which he argued that the distances of the planets from
the Sun in the Copernican system were determined by the ve regular solids, if one supposed that a planet's
orbit was circumscribed about one solid and inscribed in another.
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Kepler's model to explain the relative distances of the planets from the Sun in the Copernican System.
Figure 3.7:
Except for Mercury, Kepler's construction produced remarkably accurate results. Because of his talent
as a mathematician, displayed in this volume, Kepler was invited by Tycho Brahe (Section 3.1.10) to Prague
to become his assistant and calculate new orbits for the planets from Tycho's observations. Kepler moved
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37
to Prague in 1600.
Kepler served as Tycho Brahe's assistant until the latter's death in 1601 and was then appointed Tycho's
successor as Imperial Mathematician, the most prestigious appointment in mathematics in Europe.
He
occupied this post until, in 1612, Emperor Rudolph II was deposed. In Prague Kepler published a number of
important books. In 1604
treated
Astronomia pars Optica ("The Optical Part of Astronomy") appeared, in which he
atmospheric refraction but also treated lenses and gave the modern explanation of the workings
of the eye; in 1606 he published
appeared in 1604; and in 1609 his
De Stella Nova ("Concerning the New Star") on the new star that had
Astronomia Nova ("New Astronomy") appeared, which contained his rst
two laws (planets move in elliptical orbits with the sun as one of the foci, and a planet sweeps out equal
areas in equal times). Whereas other astronomers still followed the ancient precept that the study of the
planets is a problem only in kinematics, Kepler took an openly dynamic approach, introducing physics into
the heavens.
In 1610 Kepler heard and read about Galileo's discoveries with the spyglass.
a long letter of support which he published as
Dissertatio cum Nuncio Sidereo
He quickly composed
("Conversation with the
Sidereal Messenger"), and when, later that year, he obtained the use of a suitable telescope, he published
his observations of Jupiter's satellites (Section 3.4.3) under the title
Satellitibus
Narratio de Observatis Quatuor Jovis
("Narration about Four Satellites of Jupiter observed"). These tracts were an enormous support
to Galileo, whose discoveries were doubted or denied by many. Both of Kepler's tracts were quickly reprinted
in Florence. Kepler went on to provide the beginning of a theory of the telescope in his
Dioptrice,
published
in 1611.
During this period the Keplers had three children (two had been born in Graz but died within months),
Susanna (1602), who married Kepler's assistant Jakob Bartsch in 1630, Friedrich (1604-1611), and Ludwig
(1607-1663).
Kepler's wife, Barbara, died in 1612.
In that year Kepler accepted the position of district
mathematician in the city of Linz, a position he occupied until 1626.
In Linz Kepler married Susanna
Reuttinger. The couple had six children, of whom three died very early.
In Linz Kepler published rst a work on chronology and the year of Jesus's birth, In German in 1613 and
more amply in Latin in 1614:
Virginis Mariae Assumpsit
De Vero Anno quo Aeternus Dei Filius Humanam Naturam in Utero Benedictae
(Concerning the True Year in which the Son of God assumed a Human Nature in
the Uterus of the Blessed Virgin Mary"). In this work Kepler demonstrated 0 Kepler heard and read about
Galileo's discoveries with the spyglass. He quickly composed a long letter of support which he published as
Dissertatio cum Nuncio Sidereo ("Conversation with the Sidereal Messenger"), and when, later that year, he
obtained the use of a suitable telescope, he published his observations of Jupiter's satellites under the title
Narratio de Observatis Quatuor Jovis Satellitibus ("Narration about Four Satellites of Jupiter observed").
These tracts were an enormous support to Galileo, whose discoveries were doubted or denied by many. Both
of Kepler's tracts were quickly reprinted in Florence. Kepler went on to provide the beginning of a theory
of the telescope in his Dioptrice, published in 1611.that the Christian calendar was in error by ve years,
and that Jesus had been born in 4 BC, a conclusion that is now universally accepted. Between 1617 and
1621 Kepler published
Epitome Astronomiae Copernicanae
("Epitome of Copernican Astronomy"), which
became the most inuential introduction to heliocentric astronomy; in 1619 he published
Harmonice Mundi
("Harmony of the World"), in which he derived the heliocentric distances of the planets and their periods
from considerations of musical harmony. In this work we nd his third law, relating the periods of the planets
to their mean orbital radii.
In 1615-16 there was a witch hunt in Kepler's native region, and his own mother was accused of being a
witch. It was not until late in 1620 that the proceedings against her ended with her being set free. At her
trial, her defense was conducted by her son Johannes.
1618 marked the beginning of the Thirty Years War, a war that devastated the German and Austrian
region.
Kepler's position in Linz now became progressively worse, as
Counter Reformation
put pressure on Protestants in the Upper Austria province of which Linz was the capital.
measures
Because he
was a court ocial, Kepler was exempted from a decree that banished all Protestants from the province,
but he nevertheless suered persecution.
During this time Kepler was having his
Tabulae Rudolphinae
("Rudolphine Tables") printed, the new tables, based on Tycho Brahe's accurate observations, calculated
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CHAPTER 3. SCIENCE
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according to Kepler's elliptical astronomy. When a peasant rebellion broke out and Linz was besieged, a re
destroyed the printer's house and shop, and with it much of the printed edition. Soldiers were garrisoned
in Kepler's house. He and his family left Linz in 1626. The
Tabulae Rudolphinae
were published in Ulm in
1627.
Kepler now had no position and no salary.
He tried to obtain appointments from various courts and
returned to Prague in an eort to pry salary that was owed him from his years as Imperial Mathematician
from the imperial treasury.
He died in Regensburg in 1630.
Besides the works mentioned here, Kepler
published numerous smaller works on a variety of subjects.
3.1.8 William Gilbert
Figure 3.8:
10
William Gilbert
William Gilbert was born in Colchester, England, into a middle class family of some wealth. He entered St.
John's College, Cambridge, in 1558 and obtained an B.A. in 1561, an M.A. in 1564, and nally an M.D. in
1569. Upon receiving this last degree, he became a senior fellow of the college, where he held several oces.
Gilbert set up a medical practice in London in the 1570s and became a member of the Royal College of
Physicians (the body that regulated the practice of medicine in London and vicinity). He held a number of
oces in the college and in 1600 was elected president. He never married.
Gilbert's
De Magnete
("On the Magnet") was published in 1600 and quickly became the standard work
throughout Europe on electrical and magnetic phenomena.
Europeans were making long voyages across
oceans, and the magnetic compass was one of the few instruments that could save them from being hopelessly
(and usually fatally) lost. But little was known about the lodestone (magnetic iron ore) or magnetized iron.
Gilbert tested many folk tales.
Does garlic destroy the magnetic eect of the compass needle?
More
importantly, he made the rst clear distinction between magnetic and the amber eect (static electricity,
as we call it).
De Magnete
is a comprehensive review of what was known about the nature of magnetism,
and Gilbert added much knowledge through his own experiments. He likened the polarity of the magnet to
the polarity of the Earth and built an entire magnetic philosophy on this analogy. In Gilbert's animistic
explanation, magnetism was the soul of the Earth and a perfectly spherical lodestone, when aligned with
the Earth's poles, would spin on its axis, just as the Earth spins on its axis in 24 hours.
(In traditional
cosmology the Earth was xed and it was the sphere of the xed stars, carrying the other heavens with it,
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39
that rotated in 24 hours.) Gilbert did not, however, express an opinion as to whether this rotating Earth
was at the center of the universe or in orbit around the Sun. Since the Copernican cosmology (Section 3.5.1)
needed a new physics to undergird it, Copernicans such as Johannes Kepler (Section 3.1.7) and Galileo were
very interested in Gilbert's magnetic researches. Galileo's eorts to make a truly powerful armed lodestone
for his patrons probably date from his reading of Gilbert's book.
Several of Gilbert's unpublished and unnished works were published in 1651 by his younger half brother
under the title
De Mundo Nostro Sublunari Philosophia Nova
("New Philosophy about our Sublunary
World"). This work had little impact.
11
3.1.9 Simon Marius
Figure 3.9:
Simon Marius
12 was born in Gunzenhausen in the territory of the Markgrafschaft of Ansbach (south Germany).
Marius
His father was mayor of the city in 1576.
From 1586 to 1601, he studied (with interruptions) at the
Markgrafschaft's Lutheran academy at Heilsbronn. During this period he became interested in astronomy,
and his astronomical and meteorological observations began in 1594. In 1596 he wrote a tract on the comet
of that year, and in 1599 he published a set of astronomical tables. These eorts resulted in his appointment
as mathematician of the Markgrafschaft of Ansbach, in 1601. In that capacity he printed prognostications
each year until his death. One of his rst acts as the Markgrafschaft's mathematician was to travel to Prague
to learn Tycho Brahe's (Section 3.1.10) observational techniques and instruments. Brahe died that year, and
Marius's stay in Prague lasted only four months. But he did meet David Fabricius (Section 3.1.4) there.
He then went to Padua to study at the university there. He quickly became active in the German student
association, the "German Nation," there and was its head in 1604-1605.
In 1602 Marius began tutoring Baldessar Capra (a rich student from Milan) in mathematics and astronomy. The two observed the nova of 1604, and with Marius's help Capra published a book on that new star.
In 1607 Capra published under his own name Galileo's instruction manual on the sector (Section 3.3.4),
which circulated in manuscript. For this Capra was expelled from the university. It appears that Marius
had an important role in this plagiarism, but he had returned to his native land in 1605. In Italy, however,
11 This content is available online at
12 His name has often been rendered
<http://cnx.org/content/m11973/1.2/>.
as Mayr or Mayer by English and American writers, after the German family name. He
is referred to by modern Germans, however, as Marius, and I have followed this usage.
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CHAPTER 3. SCIENCE
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Marius's reputation was tarnished by this fraud and by certain other questionable practices as head of the
German Nation.
Upon his return from Italy, Marius settled in the city of Ansbach as court mathematician and married
Felicitas Lauer, the daughter of his publisher. In 1609 he published the rst German translation (from the
Greek) of the rst six books of Euclid's
Elements.
But Marius's most memorable (and controversial) research
involved the telescope.
In the fall of 1608, Marius learned from an artillery ocer that at the Frankfurt Fair a Dutchman had tried
to sell him a spyglass (see telescope (Section 3.3.6)). Together the two quickly reproduced the device by using
spectacle lenses but it was not until at least a year later that Marius obtained instruments good enough for
astronomical observations. Marius's oldest surviving observation of Jupiter's satellites (Section 3.4.3) dates
from the end of December 1610. In his prognostications for 1612, nished in March 1611, he stated that he
had observed Jupiter's moons since December 1609 and was busy determining the periods of the satellites.
Figure 3.10:
Title page of Mundus Iovialis13
In 1614 Marius published the fruits of his research on Jupiter in a book entitled
M.DC.IX Detectus Ope Perspicilli Belgici
Mundus Iovialis anno
("The Jovian World, discovered in 1609 by means of the Dutch
Telescope"), in which he claimed that he had observed Jupiter's moons beginning as early as late November
1609 and had begun recording his observations on 29 December. Now Marius was using the Julian calendar,
and this date corresponds to 8 January on the Gregorian calendar.
Since Marius did not publish any observations, as Galileo had done in his
Sidereus Nuncius, it is impossible
to verify Marius's claim. His reputation was, however, not the highest. Galileo responded to Marius's claim
in his
Assayer
of 1623. He began by complaining about those who had tried to steal his inventions and then
took aim at Marius:
Of such usurpers I might name not a few, but I shall pass them over now in silence, as it is
customary for rst oenses to receive less severe punishment than subsequent ones. But I shall
not remain silent any longer about a second oender who has tried too audaciously to do me the
very same thing which he did many years ago by appropriating the invention of my geometric
compass, despite the fact that I had many years previously shown it and discussed it before a
large number of gentlemen and had nally made it public in print. May I be pardoned this if,
against my nature, my habit, and my present intentionsI show resentment and cry out, perhaps
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with too much bitterness, about a thing which I have kept to myself these many years. I speak
of Simon Marius of Gunzenhausen; he it was in Padua, where I resided at the time, who set
forth in Latin the use of the said compass of mine and, appropriating it to himself, had one
of his pupils print this under his name. Forthwith, perhaps to escape punishment, he departed
immediately for his native land, leaving his pupil in the lurch as the saying goes; and against
the latter, in the absence of Simon Marius, I was obliged to proceed in the manner which is set
forth in the Defense which I then wrote and published. Four years after the publication of my
Sidereal Messenger, this same fellow, desiring as usual to ornament himself with the labors of
others) did not blush to make himself the author of the things I had discovered and printed in
that work. Publishing under the title of The Jovian World, he had the temerity to claim that
he had observed this Medicean planets which revolve about Jupiter before I had done so. But
because it rarely happens that truth allows herself to be suppressed by falsehood, you may see
how he himself, through his carelessness and lack of understanding, gives me in that very work
of his the means of convicting him by irrefutable testimony and revealing unmistakably his error,
showing not only that he did not observe the said stars before me but even that he did not
certainly see them until two years afterwards; and I say moreover that it may be armed very
probably that he never observed them at all.[2]
After making an argument about the inclinations of the orbits of the satellites to the ecliptic, Galileo
turned his attention to the date on which Marius claimed to have discovered the satellites:
Next, notice the craft with which he tries to show himself prior to me. I wrote in my Sidereal
Messenger of making my rst observation on the seventh of January, 1610, continuing then with
others on the succeeding nights. Along comes Marius, and, appropriating my very observations,
he prints in the title page of his book and again in the opening part of his work that he had
already made his observations in the year 1609, trying to give people the idea that he was rst.
Now the earliest observation that he produces as made by him is the second one made by me;
yet he announces it as made in the year 1609. What he neglects to mention to the reader that
since he is outside our church and has not accepted the Gregorian calendar, the seventh day of
January of 1610 for us Catholics, is the same as the twenty-eighth day of December of 1609 for
those heretics. So much for the priority of his pretended observations.[3]
Galileo perhaps went a bit overboard.
by December 1610.
It appears certain that Marius was observing Jupiter's moons
Yet, Marius did not produce any actual observations of the moons in his book, and
the few examples he gives all date from 1613.
Regardless of this priority question, Marius was the rst
to publish tables here of the motions of the satellites.
Mundus Iovialis
also contains a telescopic discovery
whose priority has never been disputed: in 1612 he was the rst to observe the Andromeda nebula, which
could not be resolved into stars at that time.
From several remarks in his works, it appears that Marius was a militant Lutheran. He corresponded
with David Fabricius (Section 3.1.4) and Kepler's (Section 3.1.7) former teacher Michael Maestlin, both
Lutherans, and he defended (Lutheran) Tycho Brahe's (Section 3.1.10) world system on scriptural as well
as astronomical and physical grounds. Besides his annual prognostications, he published in his later years a
book on the comets of 1618 and, posthumously, a book on Ptolemy's (Section 3.5.2) position circle. He died
in Ansbach after a brief illness in 16124.
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3.1.10 Tycho Brahe
Figure 3.11:
14
Tycho Brahe
Tyge (Latinized as Tycho) Brahe was born on 14 December 1546 in Skane, then in Denmark, now in Sweden.
He was the eldest son of Otto Brahe and Beatte Bille, both from families in the high nobility of Denmark.
He was brought up by his paternal uncle Jorgen Brahe and became his heir. He attended the universities of
Copenhagen and Leipzig, and then traveled through the German region, studying further at the universities
of Wittenberg, Rostock, and Basel. During this period his interest in alchemy and astronomy was aroused,
and he bought several astronomical instruments.
In a duel with another student, in Wittenberg in 1566,
Tycho lost part of his nose. For the rest of his life he wore a metal insert over the missing part. He returned
to Denmark in 1570.
In 1572 Tycho observed the new star in Cassiopeia and published a brief tract about it the following year.
In 1574 he gave a course of lectures on astronomy at the University of Copenhagen. He was now convinced
that the improvement of astronomy hinged on accurate observations. After another tour of Germany, where
he visited astronomers, Tycho accepted an oer from the King Frederick II to fund an observatory. He was
given the little island of Hven in the Sont near Copenhagen, and there he built his observatory, Uraniburg,
which became the nest observatory in Europe.
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Figure 3.12:
Tycho Brahe with metal insert over nose
Tycho designed and built new instruments, calibrated them, and instituted nightly observations. He also
ran his own printing press. The observatory was visited by many scholars, and Tycho trained a generation of
young Sextant astronomers there in the art of observing. After a falling out with King Christian IV, Tycho
packed up his instruments and books in 1597 and left Denmark. After traveling several years, he settled in
Prague in 1599 as the Imperial Mathematician at the court of Emperor Rudolph II. He died there in 1601.
His instruments were stored and eventually lost
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Figure 3.13:
Sextant
De Nova et Nullius Aevi Memoria Prius Visa Stella ("On the New and Never
De Mundi Aetherei Recentioribus Phaenomenis ("Concerning
the New Phenomena in the Ethereal World) (Uraniburg, 1588); Astronomiae Instauratae Mechanica ("Instruments for the Restored Astronomy") (Wandsbeck, 1598; English tr. Copenhagen, 1946); Astronomiae
Instauratae Progymnasmata ("Introductory Exercises Toward a Restored Astronomy") (Prague 1602). His
Tycho's major works include
Previously Seen Star) (Copenhagen, 1573);
observations were not published during his lifetime.
Johannes Kepler used them but they remained the
property of his heirs. Several copies in manuscript circulated in Europe for many years, and a very faulty
version was printed in 1666. At Prague, Tycho hired Johannes Kepler as an assistant to calculate planetary
orbits from his observations. Kepler published the Tabulae Rudolphina in 1627. Because of Tycho's accurate observations and Kepler's elliptical astronomy, these tables were much more accurate than any previous
tables.
Figure 3.14:
Mural Quadrant
Tycho Brahe's contributions to astronomy were enormous. He not only designed and built instruments,
he also calibrated them and checked their accuracy periodically.
He thus revolutionized astronomical in-
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45
strumentation. He also changed observational practice profoundly. Whereas earlier astronomers had been
content to observe the positions of planets and the Moon at certain important points of their orbits (e.g.,
opposition, quadrature, station), Tycho and his cast of assistants observed these bodies throughout their
orbits. As a result, a number of orbital anomalies never before noticed were made explicit by Tycho. Without these complete series of observations of unprecedented accuracy, Kepler could not have discovered that
planets move in elliptical orbits. Tycho was also the rst astronomer to make corrections for
refraction.
atmospheric
In general, whereas previous astronomers made observations accurate to perhaps 15 arc minutes,
those of Tycho were accurate to perhaps 2 arc minutes, and it has been shown that his best observations
were accurate to about half an arc minute.
Figure 3.15:
Tycho Brahe
Tycho's observations of the new star of 1572 and comet (Section 3.4.6) of 1577, and his publications on
these phenomena, were instrumental in establishing the fact that these bodies were above the Moon and
that therefore the heavens were not immutable as Aristotle had argued and philosophers still believed. The
heavens were changeable and therefore the Aristotelian division between the heavenly and earthly regions
came under attack (see, for instance, Galileo's Dialogue) and was eventually dropped. Further, if comets
were in the heavens, they moved through the heavens. Up to now it had been believed that planets were
carried on material spheres (spherical shells) that t tightly around each other. Tycho's observations showed
that this arrangement was impossible because comets moved through these spheres. Celestial spheres faded
out of existence between 1575 and 1625.
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Figure 3.16:
Tychonic Universe
If Tycho destroyed the dichotomy between the corrupt and ever changing sublunary world and the perfect
and immutable heavens, then the new universe was clearly more hospitable for the heliocentric planetary
arrangement proposed by Nicholas Copernicus in 1543. Was Tycho therefore a follower of Copernicus? He
was not. Tycho gave various reasons for not accepting the heliocentric theory, but it appears that he could
not abandon Aristotelian physics which is predicated on an absolute notion of place. Heavy bodies fall to
their natural place, the Earth, which is the center of the universe.
If the Earth were not the center of
the universe, physics, as it was then known, was utterly undermined. On the other hand, the Copernican
system (Section 3.5.1) had a number of advantages, some technical (such as a better lunar theory and smaller
epicycles), and others more based on harmony (an obvious explanation of
retrograde planetary motion,
a strict demonstration of the order and heliocentric distances of the planets). Tycho developed a system that
combined the best of both worlds. He kept the Earth in the center of the universe, so that he could retain
Aristotelian physics (the only physics available). The Moon and Sun revolved about the Earth, and the shell
of the xed stars was centered on the Earth. But Mercury, Venus, Mars, Jupiter, and Saturn revolved about
the Sun. He put the (circular) path of the comet of 1577 between Venus and Mars. This Tychonic world
system became popular early in the seventeenth century among those who felt forced to reject the Ptolemaic
(Section 3.5.2) arrangement of the planets (in which the Earth was the center of all motions) but who, for
various reasons, could not accept the Copernican alternative.
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15
3.1.11 Vincenzo Viviani
Figure 3.17:
Vincenzo Viviani
Vincenzo Viviani was born and raised in Florence where early on he attracted attention for his abilities in
mathematics. In 1639, at age 17, he became the student, secretary and assistant of Galileo (now blind) in
Arcetri. He became court mathematician of the Grand Duke of Tuscany, Ferdinand II, in 1647, and a decade
later he became one of the rst members of the Grand Duke's experimental academy, the Accademia del
Cimento. He became a foreign member of the French Academy upon its founding in 1666.
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Figure 3.18:
Vincenzo and Galileo
During his long career, Viviani published a number of books on mathematical and scientic subjects. He
edited the rst edition of Galileo's collected works (1655-1656), and worked tirelessly to have his master's
memory rehabilitated. When, in the 1730s, the Church nally allowed Galileo to be reburied in a grave with
an elaborate monument, the monument in the church of Santa Croce was constructed with the help of funds
left by Viviani for that purpose. His own remains were moved to Galileo's new grave as well.
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Figure 3.19:
Viviani's House
16
3.1.12 Thomas Harriot
Nothing is known of Harriot's life up to the time when, at age seventeen, he matriculated at the University
of Oxford. The record states that he was from the county of Oxford and that his father was a commoner.
Harriot studied at St. Mary's Hall, took his degree in 1580, and went to London. Here he was employed by
Sir Walter Ralegh and in 1585 went with the expedition to Virginia organized by Ralegh as cartographer and
one versed in the theory of navigationin our terms, as sta scientist. Harriot returned in 1586 and wrote an
account of Virginia and its natives,
A Briefe and True Report of the New Found Land of Virginia,
published
in 1588. In the meantime, Harriot had joined Ralegh in Ireland, which the English were colonizing at that
time. Ralegh granted Harriot a former abbey, where Harriot lived for a few years. Back in London, Harriot
came into contact with William Percy, 9th Earl of Northumberland, and in 1598 he left Ralegh and entered
the service of Northumberland, who gave him a pension and living quarters (and later a separate house) at
Syon House, just west of London. In 1605 Harriot was briey imprisoned along with Northumberland as a
result of the Gunpowder Plot. Harriot was quickly released but the earl remained in the Tower of London
until 1622. Harriot lived at Syon for the rest of his life. In 1613 he developed an cancerous ulcer (on his
nostril), which was the eventual cause of his death.
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Figure 3.20:
Except for
Harriot's moon drawing of 26 July 1609 Julian (5 August 1609 Gregorian)17
A Brief and True Report,
Harriot published no books. At his death he left a large number
of manuscripts on various scientic subjects, and over the past three centuries these have slowly come into
the mainstream of historical research. Harriot studied optics (about which he corresponded with Johannes
Kepler (Section 3.1.7)) and had discovered what is now known as Snell's Law of refraction before Snell did, he
made important contributions to algebra, and, from 1609 to 1613, he made numerous telescopic observations.
His telescopic drawing of the Moon (Section 3.4.1) of early August 1609 is the rst on record and preceded
Galileo's study of the Moon by several months. Several of Harriot's Moon Drawings are available.
Harriot's observation of sunspots (Section 3.4.2) of December 1610 is also the rst on record. But although
Harriot shared his observations with a group of correspondents in England, he did not publish them. The
executors of his estate published a small portion of his mathematical work under the title
Praxis
(1627).
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Figure 3.21:
Harriot's sunspot drawing of December 1610.18
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3.1.13 Christopher Clavius
Figure 3.22:
19
Christopher Clavius
Nothing is known of Clavius's early life, except that he was born in Bamberg in the German region. We do
not even know his German name, although various possibilities have been suggested. Clavius grew up during
the initial stages of the Protestant Reformation in a region of Germany, Franconia, that remained Catholic.
Three years after he was born, Ignatius de Loyola founded the
Jesuit
order with ten initial members; its
membership had reached about a thousand by 1555, when Clavius was admitted to the order in Rome,
a month before his seventeenth birthday.
In 1556 he was sent to the university of Coimbra in Portugal,
where the Jesuits had founded their own college. Here he took the normal university curriculum but excelled
in the mathematical subjects, and his observation of the total solar eclipse of 1560 made him decide that
astronomy would be his life's work. In 1560 he returned to Rome and began his study of theology at the
Collegio Romano (Section 1.2.1). He was ordained in 1564 while still pursuing his theological studies. In
1575 he became a full member of the order. He began teaching the mathematical subjects at the college as
early as 1564 and, except for a two-year stay in Naples, he was on the faculty of the Collegio Romano until
his death in 1612.
As the foremost mathematician of the Jesuit order, Clavius wrote a number of textbooks, all of which went
through numerous editions during his life. These include his version of Euclid's
on the
Sphere
Elements,
his commentary
of Sacrobosco, and books on algebra, the astrolabe, and practical arithmetic and geometry.
Clavius was the senior mathemtician on the commission for the reform of the calendar that led, in 1582, to
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the institution of the Gregorian calendar. Because of his prodigious output of mathematical works, he was
called "the Euclid of the sixteenth century." Through his teaching and textbooks, and also through several
mathematical curricula drafted by him, Clavius shaped mathematical education in the Jesuit order all over
the world.
In his astronomical books, Clavius opposed the Copernican System (Section 3.5.1) on both physical
and scriptural grounds.
(Section 3.5.2).
Until near the end of his life he remained an adherent of the Ptolemaic System
From his university days, Galileo was familiar with Clavius's books, and he visited the
famous man during his rst trip to Rome in 1587. After that they corresponded from time to time about
mathematical problems, and Clavius sent Galileo copies of his books as they appeared.
of
Sidereus Nuncius,
Collegio Romano.
The publication
in 1610, posed a serious problem for Clavius and his mathematical colleagues in the
Their opinion of the new phenomena discovered by Galileo was sought by Catholics
everywhere, but Clavius and his colleagues did not have instruments good enough to verify them. Clavius
was initially skeptical, but by the end of 1610 he and other mathematicians of the college had conrmed
the existence of the satellites of Jupiter (Section 3.4.3) and seen the phases of Venus. In April 1611, during
Galileo's visit to Rome, they certied the phenomena revealed by the telescope as real. Clavius was, however,
very cautious in his interpretation of several of them, especially the meaning of the rough appearance of the
Moon (Section 3.4.1).
He was at the time working on the edition of his commentary on the
Sacrobosco for his collected works. These
edition of his
Sphere,
Opera Mathematica
Sphere
of
appeared in Bamberg in 1611-12. In this last
Clavius mentioned the telescopic discoveries of Galileo briey as follows:
I do not want to hide from the reader that not long ago a certain instrument was brought from
Belgium. It has the form of a long tube in the bases of which are set two glasses, or rather lenses,
by which objects far away from us appear very much closer . . . than the things themselves are.
This instrument shows many more stars in the rmament than can be seen in any way without
it, especially in the Pleiades, around the nebulas of Cancer and Orion, in the Milky Way, and
other places . . . and when the Moon is a crescent or half full, it appears so remarkably fractured
and rough that I cannot marvel enough that there is such unevenness in the lunar body. Consult
the reliable little book by Galileo Galilei, printed at Venice in 1610 and called Sidereus Nuncius,
which describes various observations of the stars rst made by him.
Far from the least important of the things seen with this instrument is that Venus receives its light
from the Sun as does the Moon, so that sometimes it appears to be more like a crescent, sometimes
less, according to its distance from the Sun. At Rome I have observed this, in the presence of
others, more than once. Saturn has joined to it two smaller stars, one on the east, the other
on the west. Finally Jupiter has four roving stars, which vary their places in a remarkable way
both among themselves and with respect to Jupiteras Galileo Galilei carefully and accurately
describes.
Since things are thus, astronomers ought to consider how the celestial orbs may be arranged in
order to save these phenomena.
The phases of Venus made the Ptolemaic arrangement of the planets untenable. As Clavius cautiously
notes here, an alternative arrangement had to be found.
One could modify Ptolemy's scheme and have
Mercury and Venus go around the Sun while the Sun and all other bodies go around the Earth. This scheme
had already been proposed in Antiquity, but it had never been in the mainstream of astronomy and cosmology
because it posited two centers of rotation in the universe. The satellites of Jupiter (Section 3.4.3) had now
shown that no matter what arrangement one preferred, there was more than one center of rotation. There
were two other alternatives, the schemes of Tycho Brahe (Section 3.1.10) and Copernicus (see Copernican
System (Section 3.5.1)).
For some time Jesuit astronomers wavered on this issue, but the edict of 1616
settled the matter for them and these astronomers then adopted the scheme of Tycho Brahe. Philosophers
and theologians followed more slowly.
When Clavius wrote the above passage, he was 73 years old, and his health was forcing him to leave
active work to his younger colleagues. He died early in 1612.
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3.1.14 Christoph Scheiner
20
Christoph Scheiner was born in Wald, near Mindelheim in Swabia (southwest Germany), on 25 July 1573.
He attended the
Jesuit Latin school in Augsburg, continued his studies in the Jesuit college at Landsberg,
and entered the Jesuit order in 1595. Having completed his preparatory study, he entered the university at
Ingolstadt in 1600. Here he studied metaphysics and devoted himself to the study of mathematics. In 1610
he joined the faculty of the Jesuit college of the university as professor of Mathematics and Hebrew.
Scheiner's talents lay in the mathematical sciences and instruments. Early in his career he became an
expert on the mathematics of sundials and also invented a pantograph (a device for copying and enlarging
drawings). Upon hearing about Galileo's discoveries with the telescope, in 1610, Scheiner immediately set
out to obtain good telescopes with which to scrutinize the heavens.
After verifying Galileo's discoveries
for himself, he turned his attention to the Sun, where, in March or April 1611, he discovered sunspots
(Section 3.4.2). He was neither the rst to observe sunspots nor the rst to publish on the subject, but his
publication was the start of a controversy with Galileo over the nature of sunspots.
Because of the conservative stand of the Jesuit order on cosmological issues, Scheiner attempted to
rescue the perfection of the Sun, and by implication the heavens generally, from imperfection. He therefore
postulated that sunspots were caused by satellites of the Sun whose shadows are projected on to Sun's disk
as they cross in front of it. His tract,
Tres Epistolae de Maculis Solaribus
("Three Letters on Solar Spots")
appeared in Augsburg early in 1612, under the pseudonym "Apelles latens post tabulam," or "Apelles hiding
behind the painting." These letters were written to Marc Welser (Section 3.1.5), an Augsburg banker and
scholar who was a friend and patron to Jesuit scholars.
Welser invited Galileo to comment on these letters, and Galileo responded with two letters to Welser of
his own in which he argued that sunspots are on or near the surface of the Sun, that they change their shapes,
that they are often seen to originate on the solar disk and perish there, and that therefore the Sun is not
perfect. In the meantime, Scheiner had written two further letters to Welser on this subject, and after reading
Galileo's rst letter he wrote yet another. This second series of three letters was published by Welser in the
fall of 1612, with the title
De Maculis Solaribus et Stellis circa Iovis Errantibus Accuratior Disquisition
("A
More Accurate Disquisition Concerning Solar Spots and Stars [i.e., Satellites] Wandering around Jupiter").
Again, Scheiner used the pseudonym of Apelles. Scheiner restated his argument that sunspots were caused
by satellites and argued that Jupiter had more satellites than the four discovered by Galileo. Upon reading
this tract, Galileo wrote yet a third sunspot letter to Welser, dated December 1612, and in 1613 the Lyncean
Academy (Section 1.2.2) published all three letters under the title
Solari e loro Accidenti
Istoria e Dimostrazioni intorno alle Macchie
("History and Demonstrations Concerning Sunspots and their Properties.") A third
of the copies contained reprints of Scheiner's two tracts. Although he was polite to Scheiner, Galileo refuted
his arguments and there was little doubt as to who was the winner of this dispute.
Scheiner went on to publish books on atmospheric refraction and the optics of the eye, and in these works
he built on the optical achievements of Johannes Kepler (Section 3.1.7), thus providing important material
for later writers on the subject. He also continued his research on sunspots. In the meantime, he had begun
instructing Arch Duke Maximilian, brother of Emperor Rudolph II, in the mathematical subjects, and in
1616 he left Ingolstadt for good to become Maximilain's advisor. Scheiner henceforth had the patronage of
the Emperor's brother and in 1621 he became the confessor of Arch Duke Karl, brother of the new Emperor,
Ferdinand II. One of Scheiner's greatest achievements was the foundation of a new Jesuit college in Neisse in
Silesia. When the Arch Duke died on a voyage to Spain in 1624, Scheiner went to Rome, where he stayed for
the next eight years. It was in Rome that he published his greatest work,
Rosa Ursina
(1630), the standard
work on sunspots for more than a century.
In his
Assayer
of 1623, Galileo had made certain disparaging remarks about those who had tried to
steal his priority of discovery of celestial phenomena. Although Galileo almost certainly had others in mind,
Scheiner interpreted these remarks as being directed against him. He therefore devoted the rst book of
Ursina
Rosa
to an all out attack on Galileo, and it has been said that his enmity toward Galileo was instrumental
in starting the process against the Florentine in 1633.
20 This
Scheiner's diatribe against Galileo does, however,
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not take away from the importance of
Rosa Ursina.
Here Scheiner agreed with Galileo that sunspots are
on the Sun's surface or in its atmosphere, that they are often generated and perish there, and that the Sun
is therefore not perfect. Scheiner further advocated a uid heavens (against the Aristotelian solid spheres),
and he pioneered new ways of representing the motions of spots across the Sun's face. Because shortly after
the appearance of
Rosa Ursina
sunspot activity decreased drastically (the so-called Maunder Minimum, ca.
1645-1710), his work was not superseded until well into the eighteenth century.
In 1633 Scheiner returned to the German region, where he spent the rest of his life in Vienna and Neisse,
supervising the building of the Jesuit college.
Until the end, he worked on a massive refutation of the
Copernican theory (Section 3.5.1), the nished part of which was published posthumously, in 1650, under
the title
Prodromus pro Sole Mobili et Terra Stabili contra Galilaeum a Galileis
("Introductory Treatise in
Favor of a Moving Sun and a Stable Earth against Galileo Galilei"). The work remained virtually unkown and
had no eect on the outcome of the debate between Copernicans and advocates of the geocentric/geostatic
cosmology.
(a)
Figure 3.23:
(b)
(c)
Sunspots (Rosa Ursina, 1630) (a) large version21 (b) large version22 (c) large version23
21 http://cnx.org/content/m12126/latest/scheiner_rosa_ursina1-l.gif
22 http://cnx.org/content/m12126/latest/scheiner_rosa_ursina2-l.gif
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CHAPTER 3. SCIENCE
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3.2 Institutions
3.3 Instruments
24
3.3.1 The Pump
Figure 3.24:
Model of Pump
Galileo was appointed professor of mathematics at the University of Padua in 1592. The city of Padua had
come under Venetian rule some time earlier, and the authorities in Venice regulated the university. Galileo
quickly made friends among the Venetian patriciate and became a frequent visitor to the famous Arsenal,
the inner harbor where Venetian ships were tted out. Hulls of galleys entered on one end and within a few
hours left at the other end, fully equipped and manned. The Arsenal had been a place of practical invention
and innovation for centuries. Galileo had always been interested in mechanical things, and at the Arsenal
he learned a great deal more about what we call technology, especially shipbuilding (His private lecture
notes and other writings of this period are concerned with problems in fortication, mechanical devices, the
sector, and other aspects of technology.) In 1593 he was consulted on the placement of oars in galleys and
submitted a report in which he treated the oar as a lever and correctly made the water the fulcrum. A year
later the Venetian Senate awarded him a patent for a device for raising water by means of one horse. The
patent reads as follows:
That by the authority of this Council is granted to Mr. Galileo Galilei that for the space of the
next twenty years others than him or his agents are not allowed in the city or any place in our
state to make, have made, or, if made elsewhere, to use the device invented by him for raising
water and irrigating elds, by which with the motion of only one horse twenty buckets of water
that are contained in it run out continuously; under pains of losing the devices which will go to
the supplicant, and 300 ducats, a third of which will be for the accuser, a third for the magistrate
who undertakes the prosecution, and a third for our Arsenal; the supplicant being obligated,
however, to have made known this new type of device within one year, and that it has not been
24 This
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57
invented or recorded by others, and that a patent has not been granted [on the same device] to
others; otherwise the present grant will be void.
There is speculation that Galileo's invention was an improvement of the Archimedean Screw (consisting
of a core with a helical blade enclosed tightly in a casing), which was rst used in Antiquity and patented
in the Venetian Republic in 1567. I have found no evidence to support this speculation. Galileo apparently
submitted a model of the device to the Venetian Senate, but this model has not survived. In the History of
Science Museum
25 in Florence (Section 1.4.1), there is a model of a pump attributed to Galileo. This model
dates from the second half of the eighteenth century (that is, more than a century after Galileo's death), and
which shows four pumpsnot Archimedean Screwsdriven by two horses which rotate an excentric device
(see g.). It appears to bear little relation to the device Galileo patented in 1594.
Although as time went on Galileo's works became more and more "philosophical," he never lost his
interest in mechanical devices and technology in general. Although he was not the only "scientist" to have
such interests, he was one of a handful in Europe who could bring their practical skills and insights to bear
on science, as is shown by his experimental investigations of motion and strength of materials and by his
development of, and discoveries with, the telescope.
26
3.3.2 Hydrostatic Balance
The "Eureka" story about Archimedes and the bath tub was as well known in Galileo's day as it is in ours.
Galileo, who was a great admirer of Archimedes and adopted many of his methods, probably read it in one of
the editions of Vitruvius's
The Ten Books on Architecture,27
which was very popular in Renaissance Europe.
Supposedly, it was in the bath tub that Archimedes gured out the solution to the problem posed to him
by the king of Syracuse: was a crown (or wreath) supposedly made of pure gold in fact entirely gold? He
measured the amount of water displaced by the crown and by an equal weight of gold, and found that the
crown displaced more water. Its
specic gravity was thus less than that of gold, and therefore it had been
adulterated with another metal.
Weighing precious metals in air and then in water was presumably a practice that was common among
jewelers in Europe. Galileo had some ideas for rening the practice and, at the age of 22, he wrote a little
tract about it, which he entitled
La Bilancetta,
or "The Little Balance." What Galileo described was an
accurate balance for weighing things in air and water, in which the part of the arm on which the counter
weight was hung was wrapped with metal wire. The amount by which the counterweight had to be moved
when weighing in water could then be determined very accurately by counting the number of turns of the
wire, and the proportion of, say, gold to silver in the object could be read o directly.
This little tract illustrates the mixture of the theoretical and practical that marks Galileo's science in
contrast to that of most of his contemporaries.
25 http://galileo.imss.renze.it/
26 This content is available online at <http://cnx.org/content/m12127/1.1/>.
27 There are many editions of The Ten Books on Architecture. The story of Archimedes
IX.
is related in the introduction to Book
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3.3.3 Galileo and the Pendulum
Figure 3.25:
28
Pendulum Clock
In Aristotelian physics, which was still the predominant way to explain the behavior of bodies near the
Earth, a heavy body (that is, one in which the element earth predominated) sought its natural place, the
center of the universe. The back and forth motion of a heavy body suspended from a rope was therefore not
a phenomenon that could explain or illustrate much. It was outside the paradigm.
Galileo was taught Aristotelian physics at the university of Pisa. But he quickly began questioning this
approach. Where Aristotle had taken a qualitative and verbal approach, Galileo developed a quantitative
and mathematical approach. Where the Aristotelians argued that heavier bodies fell faster than lighter ones
in the same medium, Galileo, early in his career, came to believe that the dierence in speed depended on the
densities of the bodies. Where Aristotelians maintained that in the absence of the resisting force of a medium
a body would travel innitely fast and that a vacuum was therefore impossible, Galileo eventually came to
believe that in a vacuum all bodies would fall with the same speed, and that this speed was proportional to
the time of fall.
Because of his mathematical approach to motion, Galileo was intrigued by the back and forth motion
of a suspended weight. His earliest considerations of this phenomenon must be dated to his days before he
accepted a teaching position at the university of Pisa. His rst biographer, Vincenzo Viviani, states that he
began his study of pendulums after he watched a suspended lamp swing back and forth in the cathedral of
Pisa when he was still a student there. Galileo's rst notes on the subject date from 1588, but he did not
begin serious investigations until 1602.
Galileo's discovery was that the period of swing of a pendulum is independent of its amplitudethe arc
of the swingthe
isochronism of the pendulum.
29 Now this discovery had important implications for the
28 This content is available online at <http://cnx.org/content/m11929/1.3/>.
29 Strictly speaking, a simple pendulum is not isochronous, the period does vary
somewhat with the amplitude of the swing.
This was shown by Christiaan Huygens, in the 1650s. Huygens installed cycloidal "cheeks" near the suspension point of his
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measurement of time intervals. In 1602 he explained the isochronism of long pendulums in a letter to a friend,
and a year later another friend, Santorio Santorio, a physician in Venice, began using a short pendulum,
which he called "pulsilogium," to measure the pulse of his patients. The study of the pendulum, the rst
harmonic oscillator, date from this period.
Figure 3.26:
Harmonic Oscillator?
The motion of the pendulum bob posed interesting problems. What was the fastest motion from a higher
to a lower point, along a circular arc like a pendulum bob or along a straight line like on an inclined plane?
Does the weight of the bob have an eect on the period? What is the relationship between the length and
the period? Throughout his experimental work, the pendulum was never very far from Galileo's thought.
But there was also the question of its practical use.
A pendulum could be used for timing pulses or acting as a metronome for students of music: its swings
measured out equal time intervals. Could the device also be used to improve clocks? The mechanical clock,
using a heavy weight to provide the motive power, began displacing the much older water clock in the High
Middle Ages.
By incremental improvement, the device had become smaller and more reliable.
But the
accuracy of the best clocks was still so low that they were, for instance, useless for astronomical purposes.
Not only did they gain or lose time, but they did so in an irregular and unpredictable manner.
Could a
pendulum be hooked up to the escape mechanism of a clock so as to regulate it?
In 1641, at the age of 77, totally blind, Galileo turned his attention to this problem. Vincenzo Viviani
describes the events as follows, as translated by
Stillman Drake [57]:
One day in 1641, while I was living with him at his villa in Arcetri, I remember that the idea
occurred to him that the pendulum could be adapted to clocks with weights or springs, serving
in place of the usual tempo, he hoping that the very even and natural motions of the pendulum
would correct all the defects in the art of clocks. But because his being deprived of sight prevented
his making drawings and models to the desired eect, and his son Vincenzio coming one day
from Florence to Arcetri, Galileo told him his idea and several discussions followed. Finally they
decided on the scheme shown in the accompanying drawing, to be put in practice to learn the
fact of those diculties in machines which are usually not foreseen in simple theorizing.
Viviani wrote this in 1659, seventeen years after Galileo's death and two years after the publication of
pendulums and showed that as a result the bob now described a cycloidal arc. And he proved that when this is the case the
pendulum is truly isochronous. In practice, the swing of the bob was kept very small and the amplitude as constant as possible,
as in the long-case clock or our familiar grandfather clock. Under these conditions the simple pendulum is isochronous for all
practical purposes.
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CHAPTER 3. SCIENCE
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Christiaan Huygens's
Horologium,
in which Huygens described his pendulum clock. It is from Huygens's
construction that we date the practical development of the device.
30
3.3.4 The Sector
Figure 3.27
As the cannon (introduced in about 1325) became more sophisticated and movable, instruments were developed to help the gunner. To measure the elevation of the barrel, the gunner's compass was introduced in
the sixteenth century. It consisted of two arms at right angles, like a carpenter's square, and a circular scale
between them, on which a plumb line indicated the elevations (see g. 1). Other mathematical instruments
developed during this time included compasses, or dividers, that had various useful scales on their legs.
Galileo combined the uses of both types of instruments, designing a proportional compass or sector that had
many useful scales engraved on its legs and could be used for a variety of purposes, including gunnery (see
g. 2 and 3).
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Figure 3.28
Many of Galileo's students were members of the European nobility who needed to learn a variety of
practical subjects besides the more traditional ones. To these students, many of whom lived in his house, he
taught fortication, surveying, cosmography, and the use of the sector. Galileo wrote an instruction manual
for his sector and in 1598 he installed an instrument maker, Marcantonio Mazzoleni, in his house to produce
the sector. His students now bought their own sectors, along with the manuals, from Galileo and received
his private instruction on the subject.
Figure 3.29
It is not likely that Galileo made a lot of money from this venture, but it illustrates his entrepeneurial
eorts in the face of pressing nancial responsibilities as the oldest male of his family.
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3.3.5 The Thermometer
Figure 3.30:
31
Thermoscope
At the start of the seventeenth century there was no way to quantify heat. In Aristotelian matter theory,
heat and cold were fundamental qualities. Like dry and wet, heat and cold were qualities combined with
"prima materia" to make up the elements, earth, water, air, and re.
Thus earth was dry and cold, re
dry and hot, etc. Although one might speak of "degrees of heat or cold," there was no formal distinction
between what we would call the
extensive concept of heat and the intensive concept of temperature.
Also these degrees were not measured, except perhaps in a very rough way as when a physician put his hand
on a patient's forehead and diagnosed "fever heat."
Measuring heat became a puzzle in the circle of practical and learned men in Venice to which Galileo
belonged. The rst solution was a thermoscope. Building on
Pneumatics
by Hero of Alexandria (1st century
BCE), rst published in the West in 1575, several authors had begun playing with the idea of the expansion
of air as its heat increased, and vice versa. The rst versions, usually called thermoscopes, were little more
than toys. Benedetto Castelli (Section 3.1.6) wrote in 1638 about a device he had seen in Galileo's hands
around 1603:
He took a small glass ask, about as large as a small hen's egg, with a neck about two spans
long [perhaps 16 inches] and as ne as a wheat straw, and warmed the ask well in his hands,
then turned its mouth upside down into the a vessel placed underneath, in which there was a
little water. When he took away the heat of his hands from the ask, the water at once began
to rise in the neck, and mounted to more than a span above the level of the water in the vessel.
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63
The same Sig. Galileo had then made use of this eect in order to construct an instrument for
examining the degrees of heat and cold.
Over the next several years this thermoscope was developed by Santorio Santorio (Section 3.1.2) and
Galileo's friend Gianfrancesco Sagredo (both in Venice), Galileo, and others to include a numerical scale. It
had thus become a full-edged air thermometer. The rst series of quantitative meteorological observations
date from this period. In other parts of Europe the inventor Cornelis Drebbel and Robert Fludd developed
similar instruments. The questions about who was the rst, and whether one derived his knowledge from
another, are sterile ones which shed little light on the historical context in which this and other instruments
(e.g., the telescope (Section 3.3.6) and barometer) developed. The near simultaneous (and surely independent) invention of the air thermometer illustrates the seventeenth-century trend toward quantication of
natural phenomenaan essential dimension of the "mathematization of nature."
Figure 3.31
The liquid in glass thermometer was developed in the 1630s, but a universal standard of temperature
remained elusive. Each scientist had his own scale divisions, often based on dierent reference points. It
is impossible for us accurately to convert their measurements to our temperature scale, and at the time
it was impossible to compare temperatures in dierent places.
In the early eighteenth century, universal
temperature scales based on several duciary points (e.g. a mixture of ice and brine, a mixture of ice and
water, body temperature, the boiling point of water) were developed by Daniel Gabriel Fahrenheit (16861736), Anders Celsius (1701-1744), and Ren\x{00E9}-Antoine Ferchault de Reaumur (1683-1757). Of these,
the rst two are still in use, and the system of Celsius (extended to become an absolute scale in the nineteenth
century) has become the standard scientic temperature scale.
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3.3.6 Galileo's Telescope
Figure 3.32:
32
Johannes Hevelius observing with one of his telescopes.33 (Source: Selenographia, 1647)
The telescope was one of the central instruments of what has been called the Scientic Revolution of the
seventeenth century. It revealed hitherto unsuspected phenomena in the heavens and had a profound inuence
on the controversy between followers of the traditional geocentric astronomy (Section 3.5.2) and cosmology
34 . It was the rst extension of one of man's
and those who favored the heliocentric system of Copernicus
senses, and demonstrated that ordinary observers could see things that the great Aristotle had not dreamed
of. It therefore helped shift authority in the observation of nature from men to instruments. In short, it was
the prototype of modern scientic instruments. But the telescope was not the invention of scientists; rather,
it was the product of craftsmen. For that reason, much of its origin is inaccessible to us since craftsmen were
by and large illiterate and therefore historically often invisible.
Although the magnifying and diminishing properties of convex and concave transparent objects was
known in Antiquity, lenses as we know them were introduced in the West
35 at the end of the thirteenth
century. Glass of reasonable quality had become relatively cheap and in the major glass-making centers of
Venice and Florence techniques for grinding and polishing glass had reached a high state of development.
Now one of the perennial problems faced by aging scholars could be solved. With age, the eye progressively
loses its power to accommodate, that is to change its focus from faraway objects to nearby ones.
condition, known as
presbyopia,
This
becomes noticeable for most people in their forties, when they can no
longer focus on letters held at a comfortable distance from the eye. Magnifying glasses became common in
the thirteenth century, but these are cumbersome, especially when one is writing. Craftsmen in Venice began
making small disks of glass, convex on both sides, that could be worn in a framespectacles. Because these
little disks were shaped like lentils, they became known as "lentils of glass," or (from the Latin)
lenses.
The
earliest illustrations of spectacles date from about 1350, and spectacles soon came to be symbols of learning.
32 This content is available online at <http://cnx.org/content/m11932/1.4/>.
33 http://cnx.org/content/m11932/latest/hevelius_telescope.gif
34 "Introduction" <http://cnx.org/content/m11838/latest/>
35 They may have developed independently in China.
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Figure 3.33:
The Spectacle Vendor by Johannes Stradanus, engraved by Johannes Collaert, 158236
These spectacles were, then, reading glasses. When one had trouble reading, one went to a spectaclemaker's shop or a peddler of spectacles (see Figure 3.33 and Figure 3.34) and found a suitable pair by trial
and error.
They were, by and large, glasses for the old.
correct the refractive error known as
spectacles for the young, concave lenses
37 that
myopia, were rst made (again in Italy) in the middle of the fteenth
century. So by about 1450 the ingredients for making a telescope were there. The telescopic eect can be
achieved by several combinations of concave and convex mirrors and lenses.
Why was the telescope not
invented in the fteenth century? There is no good answer to this question, except perhaps that lenses and
mirrors of the appropriate strengths were not available until later.
In the literature of white magic, so popular in the sixteenth century, there are several tantalizing references
to devices that would allow one to see one's enemies or count coins from a great distance. But these allusions
were cast in obscure language and were accompanied by fantastic claims; the telescope, when it came, was
a very humble and simple device. It is possible that in the 1570s Leonard and Thomas Digges in England
actually made an instrument consisting of a convex lens and a mirror, but if this proves to be the case, it
was an experimental setup that was never translated into a mass-produced device.
38
The earliest known illlustration of a telescope. Giovanpattista della Porta included this
sketch in a letter written in August 1609.39
Figure 3.34:
The telescope was unveiled in the Netherlands.
In October 1608, the States General (the national
government) in The Hague discussed the patent applications rst of Hans Lipperhey (Section 3.1.1) of
Middelburg, and then of Jacob Metius of Alkmaar, on a device for "seeing faraway things as though nearby."
It consisted of a convex and concave lens in a tube, and the combination magnied three or four times.
36 http://cnx.org/content/m11932/latest/spectacle_maker2.gif
37 Note that the word lens was used only to denote convex lenses until the end
38 The claim for an "Elizabethan telescope" has recently been made by Colin
40
of the seventeenth century.
Ronin, who has demonstrated an instrument
based on the writings of Thomas Digges and William Bourne.
39 http://cnx.org/content/m11932/latest/porta_sketch.gif
40 Their optical system and magnication was the same as our traditional opera glasses.
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CHAPTER 3. SCIENCE
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The gentlemen found the device too easy to copy to award the patent, but it voted a small award to Metius
and employed Lipperhey to make several binocular versions, for which he was paid handsomely. It appears
that another citizen of Middelburg, Sacharias Janssen had a telescope at about the same time but was at
the Frankfurt Fair where he tried to sell it.
Figure 3.35:
Galileo's telescopes41
The news of this new invention spread rapidly through Europe, and the device itself quickly followed.
By April 1609 three-powered spyglasses could be bought in spectacle-maker's shops on the Pont Neuf in
Paris, and four months later there were several in Italy.
(Figure 3.35) We know that Thomas Harriot
(Section 3.1.12) observed the Moon (Section 3.4.1) with a six-powered instrument early in August 1609.
But it was Galileo who made the instrument famous.
He constructed his rst three-powered spyglass in
June or July 1609, presented an eight-powered instrument to the Venetian Senate in August, and turned a
twenty-powered instrument to the heavens in October or November. With this instrument (Figure 3.36) he
observed the Moon, discovered four satellites of Jupiter (Section 3.4.3), and resolved nebular patches into
stars. He published
Sidereus Nuncius
in March 1610.
Verifying Galileo's discoveries was initially dicult.
In the spring of 1610 no one had telescopes of
sucient quality and power to see the satellites of Jupiter, although many had weaker instruments with
which they could see some of the lunar detail Galileo had described in
Sidereus Nuncius.
Galileo's lead was
one of practice, not theory, and it took about six months before others could make or obtain instruments
good enough to see Jupiter's moons. With the verication of the phases of Venus by others, in the rst half
of 1611, Galileo's lead in telescope-making had more or less evaporated. The next discovery, that of sunspots
(Section 3.4.2), was made by several observers, including Galileo, independently.
41 http://cnx.org/content/m11932/latest/g_telescope.gif
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Figure 3.36
A typical Galilean telescope with which Jupiter's moons could be observed was congured as follows. It
had a plano-convex objective (the lens toward the object) with a focal length of about 30-40 inches., and
a plano-concave ocular with a focal length of about 2 inches.
The ocular was in a little tube that could
be adjusted for focusing. The objective lens was stopped down to an aperture of 0.5 to 1 inch. , and the
eld of view was about 15 arc-minutes (about 15 inches in 100 yards). The instrument's magnication was
15-20.
The glass was full of little bubbles and had a greenish tinge (caused by the iron content of the
glass); the shape of the lenses was reasonable good near their centers but poor near the periphery (hence
the restricted aperture); the polish was rather poor.
The limiting factor of this type of instrument was
its small eld of viewabout 15 arc-minuteswhich meant that only a quarter of the full Moon could be
accommodated in the eld. Over the next several decades, lens-grinding and polishing techniques improved
gradually, as a specialized craft of telescope makers slowly developed. But although Galilean telescopes of
higher magnications were certainly made, they were almost useless because of the concomitant shrinking
of the eld.
As mentioned above, the telescopic eect can be achieved with dierent combinations of lenses and
mirrors.
As early as 1611, in his
Dioptrice,
Johannes Kepler (Section 3.1.7) had shown that a telescope
could also be made by combining a convex objective and a convex ocular.
He pointed out that such a
combination would produce an inverted image but showed that the addition of yet a third convex lens would
make the image erect again. This suggestion was not immediately taken up by astronomers, however, and
it was not until Christoph Scheiner (Section 3.1.14) published his
Rosa Ursina
in 1630 that this form of
telescope began to spread. In his study of sunspots, Scheiner had experimented with telescopes with convex
oculars in order to make the image of the Sun projected through the telescope erect.
42
But when he
happened to view an object directly through such an instrument, he found that, although the image was
inverted, it was much brighter and the eld of view much larger than in a Galilean telescope.
Since for
astronomical observations an inverted image is no problem, the advantages of what became known as the
astronomical telescope led to its general acceptance in the astronomical community by the middle of the
century.
The Galilean telescope could be used for terrestrial and celestial purposes interchangeably. This was not
true for the astronomical telescope with its inverted image. Astronomers eschewed the third convex lens (the
erector lens) necessary for re-inverting the image because the more lenses the more optical defects multiplied.
42 The
Galilean telescope produces an erect image of an object viewed directly but an inverted image of a projected object;
by substituting a convex for the concave ocular, this situation is reversed.
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CHAPTER 3. SCIENCE
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In the second half of the seventeenth century, therefore, the Galilean telescope was replaced for terrestrial
purposes by the "terrestrial telescope," which had four convex lenses: objective, ocular, erector lens, and a
eld lens (which enlarged the eld of view even further).
(a)
(b)
Figure 3.37:
44
scope
(Machina Coelestis, 1673) (a) Hevelius's 60 foot telescope43 (b) Hevelius's 140 foot tele-
With the acceptance of the astronomical telescope, the limit on magnication caused by the small eld
of view of the Galilean telescope was temporarily lifted, and a "telescope race" developed.
Because of
optical defects, the curvature of lenses had to be minimized, and therefore (since the magnication of a
simple telescope is given roughly by the ratio of the focal lengths of the objective and ocular) increased
magnication had to be achieved by increasing the focal length of the objective. Beginning in the 1640s,
the length of telescopes began to increase.
From the typical Galilean telescope of 5 or 6 feet in length,
astronomical telescopes rose to lengths of 15 or 20 feet by the middle of the century. A typical astronomical
telescope is the one made by Christiaan Huygens, in 1656. It was 23 feet long; its objective had an aperture
of several inches, it magnied about 100 times, and its eld of view was 17 arc-minutes.
43 http://cnx.org/content/m11932/latest/hevelius_telescope_60ft.gif
44 http://cnx.org/content/m11932/latest/hevelius_telescope_140ft.gif
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Figure 3.38:
Aerial telescope (Christiaan Huygensm Astroscopium Compendiaria,1684)45
Telescopes had now again reached the point where further increases in magnication would restrict the
eld of view of the instrument too much. This time another optical device, the eld lens came to the rescue.
Adding a third convex lensof appropriate focal length, and in the right placeincreased the eld signicantly,
thus allowing higher magnications. The telescope race therefore continued unabated and lengths increased
exponentially. By the early 1670s, Johannes Hevelius had built a 140-foot telescope.
But such long telescopes were useless for observation: it was almost impossible to keep the lenses aligned
and any wind would make the instrument utter. After about 1675, therefore, astronomers did away with
the telescope tube. The objective was mounted on a building or pole by means of a ball-joint and aimed
by means of a string; the image was found by trial and error; and the compound eyepiece (eld lens and
ocular), on a little stand, was then positioned to receive the image cast by the objective. Such instruments
were called
aerial telescopes.
Although some discoveries were made with these very long instruments, this form of telescope had reached
its limits. By the beginning of the eighteenth century very long telescopes were rarely mounted any more,
and further increases of power came, beginning in the 1730s, from a new form of telescope, the reecting
telescope.
Since it was known that the telescopic eect could be achieved using a variety of combinations of lenses
and mirrors, a number of scientists speculated on combinations involving mirrors. Much of this speculation
was fueled by the increasingly rened theoretical study of the telescope. In his
Discourse on Method
Dioptrique,
appended to his
of 1637, Renè Descartes addressed the problem of spherical aberration, already pointed
out by others. In a thin spherical lens, not all rays from innityincident parallel to the optical axisare
united at one point. Those farther from the optical axis come to a focus closer to the back of the lens than
those nearer the optical axis. Descartes had either learned the sine law of refraction from Willebrord Snell
(Snell's Law)
46 or had discovered it independently, and this allowed him to quantify spherical aberration. In
order to eliminate it, he showed, lens curvature had to be either plano-hyperboloidal or spherico-ellipsoidal.
His demonstration led many to attempt to make plano-hyperboloidal objectives,
47 an eort which was
doomed to failure by the state of the art of lens-grinding. Others began considering the virtues of a concave
paraboloidal mirror as primary receptor: it had been known since Antiquity that such a mirror would bring
parallel incident rays to a focus at one point.
45 http://cnx.org/content/m11932/latest/aerial_telescope.gif
46 The ratio of the sines of the angles of incidence and refraction is constant.
47 The eect is most apparent for the objective; spherical aberration in the ocular
aects the image much less.
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CHAPTER 3. SCIENCE
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Figure 3.39:
Newton's reecting telescope (1671)48
A second theoretical development came in 1672, when Isaac Newton published his celebrated paper on
light and colors. Newton showed that white light is a mixture of colored light of dierent refrangibility: every
color had its own degree of refraction. The result was that any curved lens would decompose white light into
the colors of the spectrum, each of which comes to a focus at a dierent point on the optical axis. This eect,
which became known as chromatic aberration, resulted in a central image of, e.g., a planet, being surrounded
by circles of dierent colors. Newton had developed his theory of light several years before publishing his
paper, when he had turned his mind to the improvement of the telescope, and he had despaired of ever
ridding the objective of this defect.
He therefore decided to try a mirror, but unlike his predecessors he
was able to put his idea into practice. He cast a two-inch mirror blank of speculum metal (basically copper
with some tin) and ground it into spherical curvature. He placed it in the bottom of a tube and caught the
reected rays on a 45
◦
secondary mirror which reected the image into a convex ocular lens outside the tube
(see Figure 3.39). He sent this little instrument to the Royal Society, where it caused a sensation; it was the
rst working reecting telescope. But the eort ended there. Others were unable to grind mirrors of regular
curvature, and to add to the problem, the mirror tarnished and had to be repolished every few months, with
the attending danger of damage to the curvature.
Figure 3.40:
Hevelius's rooftop observatory, (Machina Coelestis, 1673)49
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The reecting telescope therefore remained a curiosity for decades. In second and third decades of the
eighteenth century, however, the reecting telescope became a reality in the hands of rst James Hadley
and then others. By the middle of the century, reecting telescopes with primary mirrors up to six inches
in diameter had been made.
It was found that for large aperture ratios (the ratio of focal length of the
primary to its aperture, as the f-ratio in modern cameras for instance), f/10 or more, the dierence between
spherical and paraboloidal mirrors was negligible in the performance of the telescope. In the second half of
the eighteenth century, in the hands of James Short and then William Herschel, the reecting telescope with
parabolically ground mirrors came into its own.
3.4 Observations, experiments, and discoveries
3.4.1 The Moon
Figure 3.41:
50
The Moon in Sidereus Nuncius
Ignoring the occasional pre-telescopic appearance of exceptionally large sunspots (Section 3.4.2), the Moon
is the only heavenly body which shows features to the naked eyethe Man in the Moon. These features are
permanent, and it was therefore obvious that the Moon always keeps its same face turned to us (although
there are minor perturbations that were not noticed until later).
In the philosophy of Aristotle (384-322
BCE), these features presented somewhat of a problem. The heavens, starting at the Moon, were the realm
of perfection, the sublunary region was the realm of change and corruption, and any resemblance between
these regions was strictly ruled out.
Aristotle himself suggested that the Moon partook perhaps of some
contamination from the realm of corruption.
Although Aristotle's natural philosophy was very inuential in the Greek world, it was not without
competitors and skeptics. Thus, in his little book
On the Face in the Moon's Orb, the Greek writer Plutarch
(46-120 CE) expressed rather dierent views on the relationship between the Moon and Earth. He suggested
that the Moon had deep recesses in which the light of the Sun did not reach and that the spots are nothing
but the shadows of rivers or deep chasms. He also entertained the possibility that the Moon was inhabited.
In the following century, the Greek satirist Lucian (120-180 CE) wrote of an imaginary trip to the Moon,
which was inhabited, as were the Sun and Venus.
The medieval followers of Aristotle, rst in the Islamic world and then in Christian Europe, tried to
make sense of the lunar spots in Aristotelian terms.
Various possibilities were entertained.
It had been
suggested already in Antiquity that the Moon was a perfect mirror and that its markings were reections of
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earthly features, but this explanation was easily dismissed because the face of the Moon never changes as
it moves about the Earth. Perhaps there were vapors between the Sun and the Moon, so that the images
were actually contained in the Sun's incident light and thus reected to the Earth. The explanation that
nally became standard was that there were variations of "density" in the Moon that caused this otherwise
perfectly spherical body to appear the way it does. The perfection of the Moon, and therefore the heavens,
was thus preserved.
It is a curious fact that although many symbolic images of the Moon survive in medieval and Renaissance
works of art (usually a crescent), virtually no one bothered to represent the Moon with its spots the way it
actually appeared. We only have a few rough sketches in the notebooks of Leonardo da Vinci (ca. 1500) and
51 by the English physician William Gilbert (Section 3.1.8). None of these
a drawing of the naked-eye moon
drawings found its way into print until well after the telescope (Section 3.3.6) had come into astronomy.
The telescope delivered the coup de grace to attempts to explain away the Moon's spots and to the
perfection of the heavens in general. With his telescope, Galileo saw not only the "ancient" spots, but many
smaller ones never seen before. In these smaller spots, he saw that the width of the dark lines dening them
varied with the angle of solar illumination. He watched the dark lines change and he saw light spots in the
unilluminated part of the Moon that gradually merged with the illuminated part as this part grew.
The
conclusion he drew was that the changing dark lines were shadows and that the lunar surface has mountains
and valleys. The Moon was thus not spherical and hardly perfect.
Figure 3.42:
Galileo's wash drawings52
Galileo was not the only observer of the Moon.
Indeed, he was not the rst.
Thomas Harriot (Sec-
tion 3.1.12) drew the rst telescopic representation of the Moon and observed our nearest neighbor for
several years. His drawings, however, remained unpublished.
Those who wished to defend the perfection of the heavens brought out the old argument about rarity
and density. In the letter of the Collegio Romano (Section 1.2.1) mathematicians to Cardinal Bellarmine
(Section 4.2.2) of April 1611, Christoph Clavius (Section 3.1.13) (74 years old) expressed a minority opinion:
"But it appears to Father Clavius more probable that the surface is not uneven, but rather that the lunar
body is not of uniform density and has denser and rarer parts, as are the ordinary spots seen with the natural
?
sight."[ ] The other three
Jesuit mathematicians on the faculty of the college, however, believed that the
lunar surface was indeed uneven. In this case the opposition faded away over the next few years.
Galileo wrote in a letter, 1610, that he would like to make a series of representations of the Moon showing
its changing phases. Presumably his purpose was to show how the shadows of individual features changed
with the illumination.
It appears that he abandoned this plan when he saw that there was no need for
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such an ambitious and expensive project: even the Jesuit fathers in Rome were convinced that the Moon's
surface was uneven.
Indeed, Galileo never returned to the task of representing the Moon.
he did, however, observe
lunar librations,
(In the 1630s
which show that the Moon does not always keep exactly the
same face turned toward the Earth.) Others did little better. Thomas Harriot (Section 3.1.12) did make a
rough map of the full Moon but never published it. Representations by Christoph Scheiner (Section 3.1.14),
Giuseppe Biancani, and Charles Malapert were little more than diagrams, useful only for supporting the
verbal argument that the Moon's surface is rough and uneven. These were, so to speak, generic moons, not
portraits of our nearest neighbor.
Figure 3.43:
Sketches of the Moon by Scheiner53 (1614), Biancani54 (1620) and Malapert55 (1619)
If early observations and representations of the Moon were designed to address the issue of its mountainous
nature and anity with the Earth, by the 1630s the accent was shifting. The rough lunar surface was now
accepted by astronomers and they turned their attention to how telescopic observations could help them
solve the problem of longitude (Section 3.4.7).
A lunar eclipse is an event that appears the same to all
observers for whom the Moon is above the horizon (which is, of course, not the case with solar eclipses). As
the Moon enters the Earth's shadow cone, one can mark the times at which the shadow crosses a particular
feature and later compare this time with the (local) time at which a distant colleague observed the same
event.
56 But a verbal
The dierence in local times translates directly into their dierence in longitude.
description of the lunar feature under consideration was not enough.
A lunar map was needed on which
specic features could be unambiguously identied. In Aix and Provence, Nicholas Claude Fabri de Peiresc
(still interested in the problem of longitude) and his friend, the astronomer Pierre Gassendi, decided to make
a moonmap. They engaged the services of Claude Mellan, one of the foremost artists and engravers of his
age.
With Gassendi's sketches and guidance, Mellan engraved three view of the Moon, rst quarter, full
Moon, and last quarter.
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Figure 3.44:
Claude Mellan's moon engravings: 157 , 258 ,359 .
Mellan's three engravings are surely the nest artistic renderings of the Moon ever made, but they show
an artist's Moon, not an astronomer's Moon.
Mellan wonderfully represented what he saw through the
telescope: at rst and last quarter the details at the edge of the Moon are washed out while the features near
the terminator stand out starkly; conversely, at full Moon the features in the center are washed out while
those near the edge show prominent relief. Where the solar rays are perpendicular to the lunar surface they
cast no shadows, but where they rake the surface they throw long shadows. What astronomers needed was
a single map that showed all the features equally clearlya composite view that pictured the Moon in a way
it never appeared in reality but was accurate in its placement of individual features.
The rst such map was made by the Belgian cosmographer and astronomer Michael Florent van Langren
in 1645. Two years later a much more inuential eort was published by Johannes Hevelius. In 1647 Hevelius,
a wealthy brewer in the Polish city of Gdansk, published Selenographia, the rst treatise entirely devoted to
the Moon. Hevelius combined all the talents necessary for his task. He made his own lenses, constructed his
own telescopes, observed the Moon on every clear night for several years, drew his observations, engraved
them himself, and had the wealth to publish a sumptuous book at his own expense. In Selenographia he
presented engravings of every conceivable phase of the Moon as well as three large plates of the full Moon
60
: one of the ways the full Moon actually appeared through the telescope, one the way a maker of terrestrial
maps might represent it (using the conventions of geographers), and one a composite map of all lunar features
illuminated (impossibly) from the same side. It is this last map that was to be used by astronomers during
lunar eclipses. Hevelius also suggested a system of nomenclature based on earthly features.
Hevelius founded the science of selenography (after Selene, the goddess of the Moon) and showed astronomers how to represent heavenly bodies. Selenographia was a model for all who came after him. All
lunar maps since his time have used the convention of single illumination (although while he used morning
illumination modern maps use evening illumination after van Langren's model). He also instituted the practice of showing the entire lunar surface visible from the Earth, which, because of librations, is greater than
a hemisphere. Hevelius's nomenclature, although used in Protestant countries until the eighteenth century,
was replaced by the system published in 1651 by the Jesuit astronomer Giovanni Battista Riccioli, who gave
the large naked-eye spots the names of seas (Sea of Tranquillity, Sea of Storm, etc.) and the telescopic spots
(now called craters) the name of philosophers and astronomers (g.
18).
It should be pointed out that
although Riccioli wrote his Almagestum Novum ("New Almagest") in which this map appeared to combat
the Copernican theory (Section 3.5.1), he was evenhanded in assigning names: Copernicus and Kepler were
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assigned prominent craters, and even Galileo received his due.
One last note.
As the astronomical telescope (Section 3.3.6) with its inverted image came into use,
astronomers quickly adopted the habit of representing the way they saw the Moonupside down
61 . This
practice was followed until very recently. Lunar images are now constructed and stored digitally and can be
displayed in any orientation. Astronomers have therefore reverted to showing the Moon right side up.
3.4.2 Sunspots
Figure 3.45:
62
The Sun63
Sunspots are dark areas of irregular shape on the surface of the Sun. Their short-term and long-term cyclical
nature has been established in the past century. Spots are often big enough to be seen with the naked eye.
While direct observation of the Sun in a clear sky is painful and dangerous, it is feasible when the Sun is
close to the horizon or when it is covered by a thin veil of clouds or mist. Records of naked-eye sunspot
observations in China go back to at least 28 BCE. In the West, the record is much more problematical. It is
possible that the Greek philosopher Anaxagoras observed a spot in 467 BCE, and it appears that there are
a few scattered mentions in the ancient literature as well. However, in the dominant Aristotelian cosmology,
the heavens were thought to be perfect and unchanging.
A spot that comes and goes on the Sun would
mean that there is change in the heavens. Given this theoretical predisposition, the diculty of observing
the Sun, and the cyclic nature of spots, it is little wonder that records of sunspots are almost non-existent in
Europe before the seventeenth century. A very large spot seen for no less than eight days in 807 was simply
interpreted as a passage of Mercury in front of the Sun.
Other mentions of spots seen on the Sun were
ignored by the astronomers and philosophers. In 1607 Johannes Kepler (Section 3.1.7) wished to observe a
predicted transit of Mercury across the Sun's disk, and on the appointed day he projected the Sun's image
through a small hole in the roof of his house (a
camera obscura) and did indeed observe a black spot that
he interpreted to be Mercury. Had he been able to follow up on his observation the next day, he would still
have seen the spot. Since he knew that Mercury takes only a few hours to cross the Sun's disk during one
of its infrequent transits, he would have known that what he observed could not have been Mercury.
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Figure 3.46:
A sunspot64
The scientic study of sunspots in the West began after the telescope had been brought into astronomy
in 1609.
Although there is still some controversy about when and by whom sunspots were rst observed
through the telescope (Section 3.3.6), we can say that Galileo and Thomas Harriot (Section 3.1.12) were the
rst, around the end of 1610; that Johannes and David Fabricius (Section 3.1.4) and Christoph Scheiner
(Section 3.1.14) rst observed them in March 1611, and that Johannes Fabricius was the rst to publish
on them. His book,
De Maculis in Sole Observatis
("On the Spots Observed in the Sun") appeared in the
autumn of 1611, but it remained unknown to the other observers for some time.
Figure 3.47:
Harriot's sunspot drawings.65
In the meantime, Galileo had shown sunspots to a number of people in Rome during his triumphant visit
there in the spring of 1611. But although some of his corespondents began making regular observations a
few months later, Galileo himself did not undertake a study of sunspots until April 1612. Scheiner began his
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serious study of spots in October 1611 and his rst tract on the subject,
Scriptae ad Marcum Welserum
Tres Epistolae de Maculis Solaribus
("Three Letters on Solar Spots written to Marc Welser (Section 3.1.5)")
appeared in January 1612 under the pseudonym "Apelles latens post tabulam," or "Apelles waiting behind
the painting."
66 Welser was a scholar and banker in Augsburg, who was a patron of local scholars.
Figure 3.48:
Sunspot plate from Scheiner's Tres Epistolae.67
Scheiner, a Jesuit mathematician at the university of Ingolstadt (near Augsburg), wished to preserve the
perfection of the Sun and the heavens and therefore argued that sunspots were satellites of the Sun. They
appeared as black spots when they passed in front of the Sun but were invisible at other points in their
orbits. Their orbits had to be very close to the Sun for their shapes were foreshortened as they approached
its edge. Scheiner observed sunspots through a telescope equipped with colored glasses.
In the winter of 1611-12, when Galileo received a copy of Scheiner's tract from Welser along with a
request for his comments, he was ill, and what little energy he had he was devoting to the publication of his
Discourse on Bodies in Water. When, however, that book was at the printer's, in April 1612, he turned his
attention to sunspots with the help of his protege Benedetto Castelli (Section 3.1.6), who was in Florence
(Section 1.4.1) at the time. It was Castelli who developed the method of projecting the Sun's image through
the telescope, a technique that made it possible to study the Sun in detail even when it was high in the
sky.
Galileo wrote his rst letter to Welser on sunspots, in which he argued that spots were, in fact, on
the surface of the Sun or in its atmosphere, and although he could not say for certain what they were, they
appeared to him most like clouds.
While Scheiner wrote in Latin, Galileo wrote his letter in Italian, and Welser had to have it translated
before Scheiner could read it. Scheiner had continued his solar observations, and by the time he had mastered
Galileo's letter he had already nished two more letters of his own to Welser.
He now added a third, in
which he commented that his observations agreed precisely with those of Galileo and defended his judgment
that sunspots were solar satellites. This second series of letters was published by Welser in October 1612
under the title
De Maculis Solaribus . . . Accuratior Disquisitio
("A More Accurate Disquisition . . . on
Sunspots"). Scheiner maintained his pseudonym of Apelles "or, if you prefer, Odysseus under the shield of
66 Legend has it that the famous Greek painter Apelles once hid behind one of his painting to hear what people said about
it. When a shoemaker praised the way Apelles had rendered shoes in the painting, Apelles revealed himself and thanked the
shoemaker for the compliment, but this man now proceeded to give his not so complimentary opinions about other aspects of
the painting. Apelles answered "Let the shoemaker stick to his last."
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Ajax." In the meantime, Galileo had written a second letter to Welser in August 1612.
In this letter he
showed a large number of sunspot observations, made at roughly the same time of the day, so that the Sun's
orientation was the same and the motion of the spots across its disk could be easily followed. Upon receiving
Scheiner's second tract he wrote yet a third, dated December 1612, attacking Apelles's opinions once again.
At the end of his last letter Galileo mentioned the Copernican System (Section 3.5.1) favorably in a way
that some scholars have interpreted as his rst endorsement of that theory.
Figure 3.49:
"Helioscopium" used by Scheiner for his later sunspot observations.68
Galileo's three letters were published in Rome by the Lyncean Academy (Section 1.2.2) in the summer
of 1613. About a third of the copies had reprints of the two tracts by Apelles (whose identity had in the
meantime become known) in their original Latin. There was little doubt about the winner of this contest.
Scheiner's language was convoluted, and not only did Galileo demolish his argument, he also criticized
Scheiner's a priori method of argument: the Sun is perfect, therefore it cannot have spots on its surface.
Up to this point, relations between Galileo and Scheiner were not strained. Scheiner had treated Galileo
with great respect, and Galileo had been courteous in his language. Ten years later, in his Assayer, Galileo
complained about those who would steal his priority of discovery, mentioning the case of sunspots but
not mentioning Scheiner. It is almost certain that Galileo was complaining about several others who had
published on sunspots but who had not recognized his priority. Scheiner, who at this time was settling in
Rome, took Galileo's complaint to be directed at him and became Galileo's sworn enemy.
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(a)
(b)
(c)
Figure 3.50:
large version71
Sunspot drawings from Scheiner's Rosa Ursina. (a) large version69 (b) large version70 (c)
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Scheiner had in the meantime published several important books on optics, and he had continued his
72 which
study of the Sun. He published his results in a massive tome, Rosa Ursina, ("The Rose of Orsini"),
became the standard treatise on sunspots for over a century. Scheiner had abandoned his opinion that spots
were solar satellites, and he indeed came out in favor of the system of Tycho Brahe (Section 3.1.10) and
abandoned the perfection of the heavens. His method of illustrating the motion of individual spots across
the face of the Sun became the standard way of rendering this motion and the changing shapes of the spots.
Figure 3.51:
Sunspot drawing by Gassendi73
After this time, however, sunspot activity was drastically reduced. When, in 1671, a prominent sunspot
was observed, it was treated as a rare event. Sunspot activity increased again after about 1710. The period
of low activity is now referred to as the Maunder Minimum, after Edward Walter Maunder (1851-1928),
one of the rst modern astronomers to study the long-term cycles of sunspots. Modern studies of sunspots
originated with the rise of astrophysics, around the turn of the century. The chief early investigator of these
phenomena in the United States was George Ellery Hale (1868-1938), who built the rst spectro-heliograph
and built the Yerkes and Mount Wilson observatories, including the 200-inch telescope on Palomar Mountain.
72 The rose refers to the Sun, Cardinal Orsini was his patron
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(a)
Figure 3.52:
(b)
Sunspots drawings by Hevelius (a) large version74 (b) large version75
76
3.4.3 Satellites of Jupiter
Figure 3.53:
Jupiter's moons
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Jupiter has a large number of satellites.
Of these, four are comparable to the Earth's Moon in size; the
rest are orders of magnitude smaller. When Jupiter is at opposition and closest to the Earth, the stellar
magnitude of its four large moons is between 5 and 6.
77
This means that, were it not for the shielding
brightness of Jupiter, these bodies would be visible with the naked eye. The aperture of the telescope used
by Galileo in 1610 and its magnication thus brought these four "Galilean" satellites within his grasp.
But rst Galileo had to make adjustments to the instruments. When viewing bodies that are very bright
and very small, the optical defects of the telescope (Section 3.3.6) can be crippling. By trial and error Galileo
learned to stop down the aperture of his instrument until he could begin to make useful observations. At
the end of 1609, as he was nishing his series of observations of the Moon (Section 3.4.1), Jupiter was at
opposition and the brightest object in the evening sky (not counting the Moon). When he had made the
new adjustment to his instrument, he turned his attention to Jupiter. On 7 January 1610 he observed the
planet and saw what he thought were three xed stars near it, strung out on a line through the planet. This
formation caught his attention, and he returned to it the following evening.
78 would have moved from
Galileo's expectation was that Jupiter, which was then in its retrograde loop,
east to west and had left the three little stars behind. Instead, he saw all three stars to the west of Jupiter.
It appeared as though Jupiter had not moved to the west but rather to the east.
This was an anomaly,
and Galileo returned to this formation again and again. Over the next week he found out several things.
First, the little stars never left Jupiter; they appeared to be carried along with the planet. Second, as they
were carried along, they changed their position with respect to each other and Jupiter. Third, there were
not three but four of these little stars. By the 15th of January he had gured it out: these were not xed
stars but rather planetary bodies that revolved around Jupiter. Jupiter had four moons. His book, Sidereus
Nuncius, in which his discovery was described, came o the press in Venice in the middle of March 1610 and
made Galileo famous.
(a)
Figure 3.54:
(b)
Galileo's observations of Jupiter's moon (a) large version79 (b) large version80
77 In Antiquity a rough numerical brightness rating for stars and planets was developed. Stars of the rst magnitude were
brightest; the dimmest celestial objects visible (to the naked eye) were assigned the sixth magnitude. This system is the basis
of the modern system of stellar magnitudes bases on instrumental readings.
78 When Jupiter is near opposition, it is on the same side of the Sun as the Earth, but the Earth is moving much faster than
Jupiter. It therefore appears that Jupiter is moving backward with respect to the xed stars.
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The moons of Jupiter had a major impact on cosmology. In 1610 the traditional Aristotelian cosmology
had come under attacks from Copernican astronomers. Aristotelians had a number of arguments against the
Copernican System (Section 3.5.1), one of which was now made obsolete. In traditional cosmology, there
was only one center of motion, the center of the universe which was the place of the Earth. The motions of
all heavenly bodies centered on the Earth. But according to the Copernican theory, the Earth went around
the Sun while the Moon went around the Earth. There were thus two centers of motion, which seemed an
absurdity. Moreover, if the Earth was a planet, like Mercury, Venus, Mars, Jupiter, and Saturn, why was
it the only planet to have a Moon? Galileo's discovery answered this question. The Earth was, in fact, not
the only planet to have a moon, Jupiter had four. And no matter what cosmological system one believed in,
there were now at least two centers of motion in the universe, the Earth or Sun and Jupiter. Thus, although
the satellites (the term was rst used by Johannes Kepler (Section 3.1.7)) of Jupiter were by no means proof
of the truth of the Copernican system, they certainly added ammunition on that side of the argument.
In the purely astronomical realm, the satellites of Jupiter posed a new problem for astronomers. It had
taken centuries in Antiquity to arrive at adequate geometrical modes for the motions of the known planets.
Now there was a new system of planetary bodies in miniature, and astronomers had to develop models that
could predict their motions. There was a great incentive to come up with good mathematical models, for
the satellites oered some hope for the solution of the problem of longitude at sea (Section 3.4.7). It took
almost two centuries, however, before the models and tables based on them reached satisfactory accuracy.
The naming of the satellites provides an interesting example of how such matters were handled before the
foundation of the International Astronomical Union in the twentieth century. As their discoverer, Galileo
claimed the right to name the satellites.
He wanted to name them after his patrons and asked whether
they would prefer "Cosmic Stars" (after Cosimo II (Section 1.3.2)) or "Medicean Stars." They opted for
the latter, and through much of the seventeenth century they were known by that name. In his notebooks,
Galileo referred to them individually by number, starting with the satellite closest to Jupiter, but he never
had occasion to refer to them in this way in print.
In Provence, Nicholas Claude Fabri de Peiresc tried to dierentiate between the Medicean Stars by
assigning them the names of individual members of the family, but this system was not published and thus
was never used by others. In his Mundus Iovialis ("Jovian World") of 1614, Simon Marius (Section 3.1.9)
went into the naming problem in some depth. First, he himself used the numerical system beginning with
the satellite closest to Jupiter. Second, he thought that he might call them after his patron, the Duke of
Brandenburg a suggestion followed by no one. Third, he suggested naming the farthest satellite the Saturn
of Jupiter, the next one the Jupiter of Jupiter, the third one the Venus of Jupiter, and the one nearest
the planet the Mercury of Jupiter.
This cumbersome system never caught on.
Finally, Marius related a
suggestion by Kepler (Section 3.1.7):
Jupiter is much blamed by the poets on account of his irregular loves. Three maidens are
especially mentioned as having been clandestinely courted by Jupiter with success. Io, daughter
of the River, Inachus, Callisto of Lycaon, Europa of Agenor. Then there was Ganymede, the
handsome son of King Tros, whom Jupiter, having taken the form of an eagle, transported to
heaven on his back, as poets fabulously tell . . . . I think, therefore, that I shall not have done
amiss if the First is called by me Io, the Second Europa, the Third, on account of its majesty of
light, Ganymede, the Fourth Callisto . . . .
This fancy, and the particular names given, were suggested to me by Kepler, Imperial Astronomer,
when we met at Ratisbon fair in October 1613. So if, as a jest, and in memory of our friendship
then begun, I hail him as joint father of these four stars, again I shall not be doing wrong. [3]
None of these suggestion caught on because with Jupiter's satellites, there was no confusion in the
numbering system. Following Galileo and Marius, astronomers simply referred to them by number. With
the satellites of Saturn, however, a problem developed. In 1655 Huygens discovered the rst and largest; then
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in 1671-72 Giandomenico Cassini discovered two more, and in 1684 yet another two. These ve satellites were
numbered like their Galilean counterparts. But when in 1789 William Herschel discovered two additional
satellites internal to the rst, confusion followed. Did one now renumber them all (thus causing confusion for
those who consulted older works), refer to the two new ones as nos. 6 and 7 (thus making the order of the
satellites confusing), or refer to them by order of discovery (equally confusing as to order)? Herschel's son,
John Frederick William, suggested in 1847 that Saturn's satellites be given individual names of mythological
gures associated with Saturn after the suggestion made by Marius for Jupiter's satellites.
When, the
following year, William Lassel and George Bond independently discovered an eighth satellite of Saturn, they
agreed to adopt the naming system proposed by Herschel, in which Saturn's satellites were named after his
brothers and sisters, the Titans.
This system and the now revived suggestion by Kepler and Marius for
Jupiter quickly became the convention for naming the satellites of the superior planets.
Modern Images of the Galilean Satellites
(a)
(b)
(e)
Figure 3.55:
88
(h) Callisto
(f)
(c)
(g)
(d)
(h)
(a) Io81 (b) Io82 (c) Europa83 (d) Europa84 (e) Ganymede85 (f) Ganymede86 (g) Callisto87
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3.4.4 Saturn
Figure 3.56:
Saturn
To all serious observers of the heaven, it was known that stars move in a xed formation around the Earth
except for seven bodies that moved through the xed stars in a wide band, the zodiac. To the Greeks, all
heavenly bodies were stars; most were xed but some wandered. These seven wandering stars, or planets,
were (in the conventional order), Moon (Section 3.4.1), Mercury, Venus, Sun, Mars, Jupiter, Saturn. Mercury
was the most dicult to observe because it was always close to the Sun, Venus, as morning or evening star,
was the brightest body in the heavens.
Mars had a distinctive red color, Jupiter at opposition was very
sidereal period 30 years), was the dimmest.
bright, and the straw-colored Saturn, the slowest of all planets (
The planets were identied with gods by the Mesopotamians, and the Greeks copied this system, assigning
planets the names of their gods. The planets were also associated with the seven known metals: Moon/silver,
Mercury/mercury, Venus/copper, Sun/gold. Mars/iron, Jupiter/tin, and Saturn/lead. In accordance with
their gods, the planets were assigned astrological meanings still used by the astrologers who write daily
columns in many of our newspapers.
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Figure 3.57:
Saturn as the grim reaper90
Saturn, associated with time and the grim reaper, was usually depicted with a scythe.
According to
the prevailing cosmology of Aristotle, Western astronomers knew that, like all other heavenly bodies, the
planet Saturn was perfect and spherical.
Sidereus Nuncius,
The telescope therefore gave them a surprise.
After publishing
in March 1610, Galileo continued scrutinizing the heavens, especially the planets, in
the hope of making further discoveries. In July, as Saturn was bright in the evening sky and approaching
91 he turned his telescope toward it and made a new discovery. On 30 July he wrote to his Medici
opposition,
(Section 1.3.2) patron:
I discovered another very strange wonder, which I should like to make known to their Highnesses
. . . , keeping it secret, however, until the time when my work is published . . . . the star
of Saturn is not a single star, but is a compsite of three, which almost touch each other, never
change or move relative to each other, and are arranged in a row along the zodiac, the middle
one being three times larger than the lateral ones, and they are situated in this form: oOo.
Galileo no doubt planned to publish this new discovery in his next book, but in the meantime, how could
he preserve his priority and prevent others from claiming the discovery as their own? His solution was to
circulate an anagram, s m a i s m r m i l m e p o e t a l e u m i b u n e n u g t t a u i r a s.
Others
would know that he had discovered something and when he had discovered it, but they would not known
what the discovery was. The number of letters in the anagram, 37, was too small to allow him later to fudge
and change the solution to describe a discovery made by someone else in the meantime. Before the days of
scientic papers (invented in the 1660s) this was an eective (if not always foolproof ) method of claiming
priority.
Galileo sent his correspondents the solution of the anagram,
Altissimum planetam tergeminum observavi,
or "I have observed the highest planet tri-form." And the newly congured Saturn now took its place in
Galileo's Hall of Fame. But there was something very strange about this planet. For one thing, after being
notied other observers often saw the planet oval shaped, but Galileo argued that this was due to inferior
telescopes. For another, if these lateral bodies were satellites, they were very dierent from the satellites of
Jupiter for they were much larger with respect to the planet and never moved with respect to it. Or did
they?
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91 At opposition, Saturn is 180 degrees removed from the Sun and
Earth and therefore at its brightest.
crosses the meridian at midnight. It is then closest to the
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In his third sunspot (Section 3.4.2) letter, dated December 1612, Galileo revealed another mystery about
the planet: the lateral bodies had disappeared.
Although Galileo condently predicted that they would
return, which they did, Saturn's appearances remained an enigma.
If Saturn was sometimes seen oval
(denied by Galileo), sometimes with two lateral bodies, and at other times round and solitary, how could one
explain all these appearances? And the mystery grew deeper as time went on. In 1616 Galileo announced to
his patrons that he had now observed Saturn in yet another shape, and he published this without commentary
in his Asayer of 1623.
(a)
Figure 3.58:
(b)
Galileo's sketch of 1616 and engraving in The Assayer of 1623.
Although the planet had again appeared solitary in 1626, few noticed this.
But by the next solitary
appearance in 1642, there was a growing community of telescopic astronomers who now made observation
of the planet a central part of their research programs.
Pierre Gassendi and Johannes Hevelius played
central roles in this quest, but there were a number of others. Astronomers now routinely published gures
of the shapes in which they had observed Saturn, a sampling of which can be seen in g.
3.
Near the
solitary appearances, virtually all astronomers still saw the planet triple-bodied as Galileo had rst seen it;
at other times, however, they saw two arms, or handles (Latin, ansae) attached to the central body and,
representations of this handled appearance varied greatly.
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Figure 3.59:
The composite gure from Huygens's Systema Saturnium92
If in 1642 there was a lack of information about Saturn's appearances, by 1655 when the handles had
again shrunk into little disks and the planet was approaching its solitary appearance, there was a plethora of
information. What was needed now was a model or theory that would make sense out of all these divergent
observations. In 1656 Hevelius pubished
De Nativa Saturni Facie
(On the Real Appearance of Saturn"), in
which he proposed that Saturn's body was ellipsoidal in shape with two crescents attached to its extremeties.
Rotation about the minor axis in the plane of the crescents would, according to Hevelius, explain all the
planet's appearances.
Figure 3.60:
Hevelius's Theory93
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His book convinced few. In 1658 Christopher Wren (remembered more for his later architecture) proposed
a model in which a "corona" so thin it could be considered a mere surface was attached to the planet; the
entire formation rotated or librated about its major axis.
In the meantime, Christiaan Huygens had discovered a satellite of Saturn, now named Titan. In 1656 he
published a brief tract on the discovery and included an anagram containing his own theory about Saturn's
appearances.
He unveiled his theory in 1659, in a substantial book entitled
Systema Saturnium
("The
Saturnian System"). Huygens's theory was that the planet was surrounded by a thin at ring that nowhere
touched it. Although Huygens did think that the ring had an appreciable thickness, this was basically the
modern solution of the problem.
Figure 3.61:
Wren's Theory94
But Huygens's solution was a geometrical one. The question now facing astronomers was how such a
ring could be stable. Huygens thought the ring was a solid structure; others opined that it was made up of
a huge swarm of minute satellites. The argument went on for several centuries until James Clerk Maxwell
published his mathematical analysis of the ring structure in 1858, proving that the ring had to be made up
of particles no larger than a few inches. At the end of the nineteenth century, spectrographic studies showed
that the angular rotation of the inside of the ring was greater than that of the outside of the ring, and that
the ratio obeyed Kepler's third law. The problem was now solved, although Saturn's ring system still held
surprises, as can be seen from the results of the recent ybys of the planet.
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Figure 3.62:
Huygen's Theory95
96
3.4.5 Tides
What is the cause of the tides? In the age of Galileo, this question had many answers, from animistic concepts
about the "breath" of the earth, to the pre-Newtonian intuition that the moon should have something to do
with the sea's motions. But Galileo saw this problem in a dierent way, connecting it to the whole structure
of the Copernican universe (Section 3.5.1). In 1597 the Pisan scientist wrote a letter to Kepler (Section 3.1.7),
97 , perhaps
98
(as Kepler supposed, referring to Galileo's letter) even a puzzling one, like that of the tides . What,
saying that he had found in the Copernican doctrine a way to explain many natural phenomena
exactly, the Galilean solution to the problem of the tides was, became clear only in 1616, when Galileo was
in Rome, trying to convince the Church not to ban the Copernican theory. After this attempt failed, with the
consequence that the Copernican position could no longer be held or defended, Galileo wrote his "Discorso
sul usso e il reusso del mare", in the form of a private letter to Cardinal Orsini
99 .
In this letter Galileo examines in how many ways the water contained in a vase can move. A rst way
derives from the slope of the vase, like that of the bed of a river. Secondly, an external cause (such as a strong
wind) can produce waves in the water. But there is also a third cause for the water to move: the motion
of the vase itself. Indeed, if the vase has an irregular motion (i.e. with accelerations and decelerations), the
water also acquires a motion. Galileo makes a comparison between the water and the seas and between the
vase and the earth, so that the changes in the motions of the sea can be eects of an irregularity in the earth
motion. Galileo's theory is based on the following reasoning: the Copernican earth is aected by two main
circular motions, i. e. the annual revolution around the sun and the diurnal rotation. Due to a additive
eect of these motions, there is an alteration in the surface speed of the earth, every 12 hours. Referring
to the diagram, in which the large circle represents the earth's annual orbit and the small circle the earth
itself, Galileo explained his ideas as follows:
[W]hile the circle BCDL turns on itself in the direction BCD, there are in its circumference
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97 Galileo to Kepler, 4 August 1597, Opere, X:68.
98 Kepler to Herwart von Hohenberg, 26 March 1598, Gesammelte Werke, XIII:192-93. See also Galileo, Opere, X:72.
99 Opere, V:377-95. For an English translation, see Maurice A. Finocchiaro, The Galileo Aair (Berkeley: University
California Press, 1989), pp. 119-33.
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mutually contrary movements: for, while the parts near C go down, the opposite ones near L go
up; and while the parts near B move toward the left, the part on the opposite side near D move
toward the right. Thus, in a complete rotation the point marked B rst moves down and toward
the left; when it is near C, it descends the most and begins to move toward the right; at D it no
longer goes down, but moves most toward the right and begins to go up; and at L it ascends the
most, begins to move slowly toward the left, and goes up till B. Now let us combine the specic
motions of the parts of the earth with the general movement by the whole globe through the
circumference AFG. We shall nd that the absolute motion of the upper part (near B) is always
fastest, resulting from the composition of the annual motion along the circumference AF and the
specic motion of the part B, which two motions reinforce each other and add up toward the
left; on the other hand, the absolute motion of the lower parts near D is always slowest, since the
specic motion of D, which here is fastest toward the right, must be subtracted from the annual
motion along the circumference AF, which is toward the left. . . .
Thus, for 12 hours, a point on the earth's surface will move eastward, in opposition to the global westward
movement of the earth, and for 12 hours it will move westward, in the same direction as the annual motion.
The composition of these motions causes on one hand a slackening (due to a subtraction of two opposite
motions) and on the other hand an acceleration (due to an addition of two motions in the same direction).
Figure 3.63:
Diagram
With this mechanism, Galileo thought he had found the irregularity in the movement of the vase (the
earth), able to move the water (the seas). Although this irregularity is not perceived by us on solid ground,
Galileo was sure it was shown by the oceans, by the ebb and ow of the tides. Galileo intended to solve two
problems at the same time: the tides are not a mystery any more if we consider them an eect of the earth's
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motions, and the earth's motions themselves (i.e. the Copernican system) are not absurd any more if we
consider the tides a tangible proof of these motions.
Such a theory remained in Galileo's mind until 1623, when Maeo Barberini (Section 1.3.4), who was
considered a friend and a patron of artists and scientists, became Pope (Urban VIII). Galileo tried to
propose again the Copernican question, and obtained the permit to write a dialogue, in which to discuss
the arguments for the two main world systems (Ptolemaic (Section 3.5.2) and Copernican (Section 3.5.1)),
without presenting a nal verdict. Galileo worked for almost 10 years at the
Dialogue :
it is divided in four
Days in which Salviati (a Copernican) and Simplicio (an Aristotelian) confront each other; a third character
(Sagredo) listens to them, often intervening in favor of Salviati. In the Fourth Day of this masterpiece appears
the theory of the tides again, the proof that the earth's motions are not a ction, that the uctuations of
the sea are eects of mechanical causes and not of a magical attraction between the moon and the water.
The earth is a planet: all that happens on it is caused by its own motions, not by the astral inuences. This
proof, however, presented the nal verdict that the Pope did not want the
Dialogue
to contain: Galileo was
brought before the Inquisition and again lost his battle.
Many critical questions are involved in this Galileo theory of the tides: rst of all the fact that, rejecting
any kind of attractive force as the real cause of the tides, this theory was, in Newtonian terms, an error.
Nevertheless this judgment has for a long time impeded a historical evaluation of Galileo's theory. Only in
some recent essays the question is examined with more care and is judged in the context of the physical and
astronomical debate of the seventeenth century. To accuse Galileo of an excess of scientic realism, or even
of presumption (as some authors have done), is to lose the possibility of historical reconstruction in which
what counts is not the achievement of the future, but the eorts to reach them. Galileo was trying to build a
scientic method in a world based more on books than on the nature, more on astrology than on astronomy,
more on closing one's eyes than on observing through the telescope. That his theory of the tides did not
survive the critical judgment of his successors is not germane to historical inquiry.
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3.4.6 Comets
Figure 3.64:
Comet Ikeya-Seki
Comets played an important role in the revolution of astronomy and cosmology that occurred between 1500
and 1700.
In the earlier Aristotelian geocentric cosmological scheme, the universe was divided into two
regions with very dierent characteristics. The heavens, which reached from the sphere of the Moon to that
of the xed stars, were perfect and unchanging; motion there was exclusively circular. Below the Moon was
the world of corruption and change. The Earth was the center of the universe, the natural place of all heavy
bodies (bodies in which the element earth predominated). Around it were arranged in successive spherical
shells the elements of water, air, and re. The sphere of re reached up to the sphere of the Moon, the rst
heavenly sphere. Although there are references in Aristotle that some of the imperfection of the sublunary
region may have rubbed o on the Moon, basically the divide between the heavenly and sublunary regions
was absolute.
If the heavens were perfect and unchanging, then no change could occur in them.
Any phenomenon
that involved change was, therefore, by denition a sublunary one. Whereas heavenly bodies moved around
the Earth in never ending circles, repeating their patterns over and over, comets came and went.
They
appeared suddenly, moved across the constellations for a brief period of time, and then disappeared. There
was no regularity, no pattern to their appearances and motions. They were therefore considered changing
appearances and therefore by denition their location was "below" the Moon. (It is to be noted here that
this is true only in western cosmology after Aristotle.
In the cosmologies of other cultures, comets were
dened dierently.)
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The Aristotelian cosmology was dominant in the Islamic world and in Christian Europe.
We nd no
coherent record of comets in the astronomical annals of these cultures (as we do, for instance in China).
Comets were, of course, observed, and they are mentioned in chronicles and other non-astronomical documents. They were considered omens, bad omens, and since there was always a major disaster (plague, war,
ood, re, etc.) that happened shortly after a comet had been seen, there was no easy way to prove this
notion wrong.
Figure 3.65:
Comet of 1449-50 observed by Toscanelli101
The rst recorded eorts to study the paths of comets across the heavens as an astronomical exercise
occurred in Florence (Section 1.4.1) in the fteenth century, about a century before the birth of Galileo.
By the early sixteenth century, astronomers were observing and measuring the positions of all comets, and
in the 1530s Peter Apian in Germany discovered that the tail of a comet always points away from the
Sun. His discovery was illustrated in a tract written in German, meant for popular consumption. Among
the philosophers (and cosmology was a part of philosophy) there was as yet no doubt that comets were
sublunary phenomena.
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Figure 3.66:
Comet of 1532 observed by Apian
102
But practicing astronomers, that is those who observed the positions of heavenly bodies and calculated
their positions, increasingly began to measure the positions of comets. If they were below the Moon, then
their
parallax could be no less than the Moon's, about 1 degree (the horizontal parallax, which is the angle
subtended at the Moon by the Earth's radius). Why did not a few carefully executed measurements settle
this issue quickly?
First, there was in Europe no great tradition of making accurate, or even regular, astronomical observations before about 1500. For that reason, measuring instruments were primitive, not even taking advantage
of the capabilities of existing technology. They were simple, hand-held, wooden instrumentslittle more than
roughly calibrated sticksand their accuracy was perhaps at best 1/4 degree, usually perhaps 1/2 degree.
There was little accuracy and even less consistency in the measurements of individual astronomers. When
it came to comparing the measurements of practitioners in places all over Europe, the situation became
hopeless. The results were parallaxes ranging from 10 degree to negative values.
Second, astronomers and others who practiced the mathematical sciences dealt only with positions and
motions.
These were accidental properties of bodies and could tell you nothing about their essences.
mathematician could tell you where the apple was and he could describe its motion if it fell.
A
But this
information could not tell you what made this body an apple and why it fell. These were questions that
belonged to philosophy. It was therefore not at all obvious that the measurements of the astronomers could
turn an obviously changing cometary phenomenon into a perfect and immutable heavenly body.
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Figure 3.67:
Comet of 1577
By the time Galileo was beginning to turn his attention to the study of mathematics, the science of
astronomy was changing.
Copernicus's (Section 3.5.1)
De Revolutionibus
(1543) had been around for a
generation, and there were other cosmological theories as well that challenged the existing cosmology. When
in 1577 a huge comet appeared whose tail spread in a great arc across the sky, observers all over Europe,
Tycho Brahe among them, made measurements of its changing positions. The resulting literature was huge,
and if the verdict was by no means unanimous, it was clear that the opinion that comets were heavenly
bodies had become respectable in learned circles.
The rising authority of Tycho Brahe (Section 3.1.10),
based on his noble birth and his miraculous instruments, gave added impetus to the change of opinion. Over
the next two generations the perfection of the heavens was abandoned, as were the crystalline spheres of
which they were supposedly composed.
Figure 3.68:
Comet of 1618103
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But placing comets in the heavens raised new questions. What were their paths? What was their nature?
Through much of the seventeenth century the debate ranged. in his
Assayer
of 1623 Galileo argued that
comets were optical phenomena and that therefore one could not measure their parallaxes. In this opinion
he was not followed by others. It was argued that comets moved in straight lines or parabolic arcs. Descartes
argued that comets were bodies that traveled from one solar system to another.
The mechanical philosophy of the second half of the seventeenth century had a great bearing on this
debate, as we can see in Isaac Newton's conclusions. In his Mathematical Principles of Natural Philosophy
of 1687, Newton argued that all matter attracts all other matter. If comets are made of matter, then they
are attracted to the Sun just as the planets are. Given rectilinear inertia and a centrally directed force, the
moving body's path must be a conic section. Edmond Halley took this notion and drew up a table of the
parameters of the twenty-odd brightest comets that had been seen over the previous several centuries. He
pointed out that the parameters of the comets of 1533, 1607 and 1682 were the same and concluded that
this was a periodic comet. He predicted its return in 1758. In that year (Halley had died in 1742) the comet
appeared as predicted and has been called Halley's Comet ever since.
104
3.4.7 Longitude at Sea
Figure 3.69
Until the end of the fteenth century, sailors navigated with almost daily reference to land. In the Mediterranean it was dicult to go very far astray, and in western and northwest Europe navigation was coastal.
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Ships hugged the shore from Gibraltar to the Norway and the Baltic. The only exception to this rule was the
trade between Scandinavia, Iceland, and occasionally Greenland. These routes were discovered (probably
by accident) by the Vikings around 1000 CE. With the Portuguese voyages of discovery, in the fteenth
century, navigation became more dicult. For some time Portuguese sailors hugged the coast of Africa, as
they carefully explored the contours of this continent. Both the winds and the currents there made sailing
south dicult, however, and beginning with the voyages of Diaz (who rounded the Cape of Good Hope)
in 1486, Columbus in 1492, and da Gama in 1498, Spanish and Portuguese sailors sailed the high seas for
weeks on end without seeing land. How did they know where they were and whether they were on the right
course?
Until the end of the fteenth century, sailors navigated with almost daily reference to land.
In the
Mediterranean it was dicult to go very far astray, and in western and northwest Europe navigation was
coastal. Ships hugged the shore from Gibraltar to the Norway and the Baltic. The only exception to this
rule was the trade between Scandinavia, Iceland, and occasionally Greenland. These routes were discovered
(probably by accident) by the Vikings around 1000 CE. With the Portuguese voyages of discovery, in the
fteenth century, navigation became more dicult. For some time Portuguese sailors hugged the coast of
Africa, as they carefully explored the contours of this continent. Both the winds and the currents there made
sailing south dicult, however, and beginning with the voyages of Diaz (who rounded the Cape of Good
Hope) in 1486, Columbus in 1492, and da Gama in 1498, Spanish and Portuguese sailors sailed the high seas
for weeks on end without seeing land. How did they know where they were and whether they were on the
right course?
The only reference points on the high seas were the stars and Sun. Locations and courses now had to be
spatial: a navigator needed to locate himself on a grid of imaginary lines of latitude and longitude.
The Portuguese pioneered the method of navigating by latitude. Ships had to be equipped with instruments (astrolabes, cross stas) to measure the altitudes of stars or the Sun. It was not dicult to determine
one's latitude to within about a degree by this method. Longitude was, however, a dierent matter. Observations of the Sun and stars were of no immediate help: in order to determine one's longitude with respect
to, e.g., Lisbon, one had to nd out the dierence in local times between one's location and Lisbon.
easy method that was suciently accurate suggested itself.
No
The magnitude of the problem is illustrated
by the voyage of the Portuguese navigator Cabral who, on his way to the East Indies, swung west in the
south Atlantic in order to pick up favorable winds and ran into the coast of Brazil.
Further, the world
maps prepared in the sixteenth century erred widely in the longitudes of places. The east-west length of the
Mediterranean was in error by 19\x{00B0}about 1100 miles! The longitudes of China and Japan were o
by much larger margins. For nations engaged in trade with the East and West Indies, nding longitude at
sea was a matter of national interest. Late in the sixteenth century the Spanish Crown instituted a large
prize in the hope of a solution. This initiative was followed by the French, Dutch, and English governments
in the seventeenth century.
Soon after the discovery of the satellites of Jupiter (Section 3.4.3), scientists realized that the formation
of the satellites provided a clock whose face could be seen from every vantage point.
In 1612 Nicholas
Claude Fabri de Peiresc in Aix en Provence sent out an observer to the eastern part of the Mediterranean to
observe Jupiter's satellites while he did the same at home. The idea was to compare the satellite positions
and formations observed on the same day at Aix and, e.g., Tripoli and from these to deduce the dierence
in local (solar) times between the two locations.
Peiresc was, however, disappointed by the results: the
positions of the satellites changed too slowly for this purpose. Had the method been more accurate, he had
hoped to provide sailors with tables of the motions of the satellites, so that they could carry the standard
time reference with them and determine their longitude on the spot. Peiresc now abandoned this eort.
In 1612 Galileo for the rst time observed an eclipse of a satellite of Jupiter. When a satellite enters
the shadow cone behind the planet it disappears very quickly. Such eclipses were, for all practical purposes,
instantaneous events. If a navigator on the high seas could note the local time of such an eclipse and compare
it with the local time at which it was predicted to happen at the European reference location, the dierence
in times and therefore longitude could easily be found. Could suciently accurate tables be drawn up?
In 1613 Galileo entered into negotiations with the Spanish Crown to provide Spanish navigators with
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eclipse tables for the satellites and telescopes (Section 3.3.6) with which to make the observations. He worked
for many years to perfect his knowledge of the satellites' motions but never published his results (presumably
because they were not suciently accurate). He did, however, have reasonable hopes of being able to predict
eclipses over short periods. But there was a more severe problem. In order to observe the satellites, one
needed a telescope of relatively high power, say 15, and given the small eld of view of the Galilean telescope
(perhaps 20' of arc) it was impossible to make the observation from the deck of a ship on the high seas.
Galileo made some trials of a telescope attached to a helmet (he called this device a
celatone)
on ships
riding at anchor in the harbor of Livorno, but this approach only worked with rather low-powered telescopes.
The Spanish were not impressed by the method, and negotiations eventually faltered.
Galileo took up the problem again after his trial, and this time he negotiated (through intermediaries)
with the States General of the Netherlands, who had just announced their prize.
Although the Dutch
government admired Galileo greatly, its committee came to the same conclusion its Spanish counterpart had
earlier. For his eorts, the States General voted Galileo a gold medal and chain, but Galileo was forbidden
by the Inquisition from accepting this award.
By Galileo's death, in 1642, the only tables of the motions of Jupiter's satellites were an inaccurate eort
published by Simon Marius (Section 3.1.9) in 1614.
The Sicilian astronomer Giovanni Battista Odierna
published new tables in 1654, but these were again not accurate. The rst reasonably accurate tabl es were
published by Gian Domenico Cassini in 1668.
Figure 3.70:
Gian Domenico Cassini
It was because of Cassini's tables that the Danish astronomer Olaeus Romer was able, in 1676, to nd a
systematic error of about 10 minutes, whose period was equal to the synodic period (opposition to opposition)
of Jupiter. Romer correctly interpreted his result to demonstrate that light does not travel instantaneously.
He estimated that it took eleven minutes for light from the Sun to reach the Earth.
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Figure 3.71:
Cassini's tables of 1668105
Tablesespecially those of the motion of the rst satellites, whose period is about 42 hours and whose
eclipses are therefore most frequentwere now becoming suciently accurate to hold out hope that they
could be used for determining longitude at sea. The English worked hardusing rst the newer astronomical
telescope with its larger eld of view and then, in the eighteenth century, the reecting telescopeto make it
possible for an observer on a ship to observe the satellites. They went so far as to install gimbaled observing
seats that were independent of the motion of the ship.
But progress was incrementally slow, and in the
1760s a practical solution to the problem of longitude at sea came from the clock-makers: John Harrison had
managed to make clocks so accurate and impervious to motion that they could be carried on a ship and not
err by more than seconds on a trip to the East Indies. On his rst voyage to the South Seas, Captain James
Cook took a Harrison chronometer with him and his trials proved this method to be entirely satisfactory.
In the meantime, however, the French had made a dierent use of satellite eclipses. If it was not feasible
to make observations from the deck of a moving ship, it was certainly possible to observe the satellites on
land. In the 1670s French astronomers, under the leadership of Cassini, began making observations of the
satellites in many locations in France. The resulting map of France, nished in 1679 showed that the west
coast of France was too far west by an entire degree on existing maps and that similar adjustments had to
be made to the Mediterranean coast. It is said that upon seeing this map, King Louis XIV remarked that
he was losing more territory to his astronomers than to his enemies.
The method of determining longitudes by means of observations of the eclipses of Jupiter's satellites was
at the center of the revolution in geodesy in the eighteenth century. Travelers and explorers routinely timed
eclipses and sent their results back to Paris and London, to be compared with the observations made there.
When Charles Mason and Jeremiah Dixon surveyed the boundary line between Pennsylvania and Maryland,
from 1763 to 1767, they used eclipses of the satellites of Jupiter to determine the exact longitudes of places.
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3.5 Theories
3.5.1 Copernican System
Figure 3.72:
106
Copernicus
The rst speculations about the possibility of the Sun being the center of the cosmos and the Earth being
one of the planets going around it go back to the third century BCE. In his
Sand-Reckoner,
Archimedes (d.
212 BCE), discusses how to express very large numbers. As an example he chooses the question as to how
many grains of sand there are in the cosmos. And in order to make the problem more dicult, he chooses not
the geocentric cosmos generally accepted at the time, but the heliocentric cosmos proposed by Aristarchus
of Samos (ca. 310-230 BCE), which would have to be many times larger because of the lack of observable
stellar parallax.
We know, therefore, that already in Hellenistic times thinkers were at least toying with
this notion, and because of its mention in Archimedes's book Aristarchus's speculation was well-known in
Europe beginning in the High Middle Ages but not seriously entertained until Copernicus.
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Figure 3.73:
Copernicus
European learning was based on the Greek sources that had been passed down, and cosmological and
astronomical thought were based on Aristotle and Ptolemy (Section 3.5.2).
Aristotle's cosmology of a
central Earth surrounded by concentric spherical shells carrying the planets and xed stars was the basis of
European thought from the 12th century CE onward. Technical astronomy, also geocentric, was based on
the constructions of excentric circles and epicycles codied in Ptolemy's
Almagest
(2d. century CE).
In the fteenth century, the reform of European astronomy was begun by the astronomer/humanist Georg
Peurbach (1423-1461) and his student Johannes Regiomontanus (1436-1476). Their eorts (like those of their
colleagues in other elds) were concentrated on ridding astronomical texts, especially Ptolemy's, from errors
by going back to the original Greek texts and providing deeper insight into the thoughts of the original
authors. With their new textbook and a guide to the
Almagest,
Peurbach and Regiomontanus raised the
level of theoretical astronomy in Europe.
Several problems were facing astronomers at the beginning of the sixteenth century. First, the tables (by
means of which to predict astronomical events such as eclipses and conjunctions) were deemed not to be
suciently accurate. Second, Portuguese and Spanish expeditions to the Far East and America sailed out
of sight of land for weeks on end, and only astronomical methods could help them in nding their locations
on the high seas. Third, the calendar, instituted by Julius Caesar in 44 BCE was no longer accurate. The
equinox, which at the time of the Council of Nicea (325 CE) had fallen on the 21st, had now slipped to
the 11th.
Since the date of Easter (the celebration of the dening event in Christianity) was determined
with reference to the equinox, and since most of the other religious holidays through the year were counted
forward or backward from Easter, the slippage of the calendar with regard to celestial events was a very
serious problem. For the solution to all three problems, Europeans looked to the astronomers.
Nicholas Copernicus (1473-1543) learned the works of Peurbach and Regiomontanus in the undergraduate
curriculum at the university of Cracow and then spent a decade studying in Italy.
Upon his return to
Poland, he spent the rest of his life as a physician, lawyer, and church administrator. During his spare time
he continued his research in astronomy.
The result was
De Revolutionibus Orbium Coelestium
("On the
Revolutions of the Celestial Orbs"), which was published in Nuremberg in 1543, the year of his death. The
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book was dedicated to Pope Paul III and initially caused litle controversy. An anonymous preface (added by
Andreas Osiander, the Protestant reformer of Nuremberg) stated that the theory put forward in this book
was only a mathematical hypothesis: the geometrical constructions used by astronomers had traditionally
had only hypothetical status; cosmological interpretations were reserved for the philosophers. Indeed, except
for the rst eleven chapters of Book I,
of the
Almagest.
Figure 3.74:
De Revolutionibus
was a technical mathematical work in the tradition
Diagram of the Copernican system, from De Revolutions107
But in the rst book, Copernicus stated that the Sun was the center of the universe and that the
Earth had a triple motion
108 around this center. His theory gave a simple and elegant explanation of the
retrograde motions of the planets (the annual motion of the Earth necessarily projected onto the motions
of the planets in geocentric astronomy) and settled the order of the planets (which had been a convention
in Ptolemy's work) denitively. He argued that his system was more elegant than the traditional geocentric
system. Copernicus still retained the priviledged status of circular motion and therefore had to construct
his planetary orbits from circles upon and within circles, just as his predecessors had done. His tables were
perhaps only marginally better than existing ones.
The reception of
De Revolutionibus
was mixed. The heliocentric hypothesis was rejected out of hand
by virtually all, but the book was the most sophisticated astronomical treatise since the
Almagest,
and
for this it was widely admired. Its mathematical constructions were easily transferred into geocentric ones,
and many astronomers used them.
In 1551 Erasmus Reinhold, no believer in the mobility of the Earth,
Prutenic Tables, based on Copernicus's parameters. These tables came
accuracy. Further, De revolutionibus became the central work in a network of
published a new set of tables, the
to be preferred for their
astronomers, who dissected it in great detail.
Not until a generation after its appearance, however, can
we begin point to a community of practicing astronomers who accepted heliocentric cosmology.
the most remarkable early follower of Copernicus was Thomas Digges (c.
Description of the Coelestiall Orbes (1576)
Perhaps
A Pert
De Revolutionibus into
1545-c.1595), who in
translated a large part of Book I of
English and illustrated it with a diagram in which the Copernican arrangement of the planets is imbedded
in an innite universe of stars.
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108 A daily rotation about its center, an annual motion around the
Sun, and a conical motion of its axis of rotation. This
last motion was made necessary because Copernicus conceptualized the Earth's annual motion as the result of the Earth being
embedded in a spherical shell centered on the Sun. Its axis of rotation therefore did not remain parallel to itself with respect
to the xed stars. To keep the axis parallel to itself, Copernicus gave the axis a conical motion with a period just about equal
to the year. The very small dierence from the annual period accounted for the precesion of the equinoxes, an eect caused by
the fact that the Earth's axis (in Newtonian terms) precesses like a top, with a period of about 26,000 years. (Copernicus's
ideas about this precession were more cumbersome and based on faulty data.)
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Figure 3.75:
Diagram of the universe by Thomas Digges109
The reason for this delay was that, on the face of it, the heliocentric cosmology was absurd from a
common-sensical and a physical point of view. Thinkers had grown up on the Aristotelian division between
the heavens and the earthly region, between perfection and corruption. In Aristotle's physics, bodies moved
to their natural places. Stones fell because the natural place of heavy bodies was the center of the universe,
and that was why the Earth was there.
Accepting Copernicus's system meant abandoning Aristotelian
physics. How would birds nd their nest again after they had own from them? Why does a stone thrown
up come straight down if the Earth underneath it is rotating rapidly to the east? Since bodies can only have
one sort of motion at a time, how can the Earth have several? And if the Earth is a planet, why should it
be the only planet with a moon?
For astronomical purposes, astronomers always assumed that the Earth is as a point with respect to the
◦
heavens. Only in the case of the Moon could one notice a parallactic displacement (about 1 ) with respect
to the xed stars during its (i.e., the Earth's) diurnal motion. In Copernican astronomy one now had to
assume that the
orbit of the Earth was as a point with respect to the xed stars, and because the xed
parallax, the sphere of the xed stars
stars did not reect the Earth's annual motion by showing an annual
had to be immense. What was the purpose of such a large space between the region of Saturn and that of
the xed stars?
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Figure 3.76:
Parallax110
These and others were objections that needed answers. The Copernican system simply did not t into
the Aristotelian way of thinking. It took a century and a half for a new physics to be devised to undegird
heliocentric astronomy. The works in physics and astronomy of Galileo and Johannes Kepler (Section 3.1.7)
were crucial steps on this road.
There was another problem. A stationary Sun and moving Earth also clashed with many biblical passages.
Protestants and Catholics alike often dismissed heliocentrism on these grounds. Martin Luther did so in one
of his "table talks" in 1539, before
De Revolutionibus
had appeared. (Preliminary sketches had circulated
in manuscript form.) In the long run, Protestants, who had some freedom to interpret the bible personally,
accepted heliocentrism somewhat more quickly.
cautious in the religious climate of the
Catholics, especially in Spain and Italy, had to be more
Counter Reformation, as the case of Galileo clearly demonstrates.
Christoph Clavius (Section 3.1.13), the leading Jesuit mathematician from about 1570 to his death in 1612,
used biblical arguments against heliocentrism in his astronomical textbook.
The situation was never simple, however.
For one thing, late in the sixteenth century Tycho Brahe
(Section 3.1.10) devised a hybrid geostatic heliocentric system in which the Moon and Sun went around the
Earth but the planets went around the Sun. In this system the elegance and harmony of the Copernican
system were married to the solidity of a central and stable Earth so that Aristotelian physics could be maintained. Especially after Galileo's telescopic discoveries, many astronomers switched from the traditional to
the Tychonic cosmology.
For another thing, by 1600 there were still very few astronomers who accepted
Copernicus's cosmology. It is not clear whether the execution of Giordano Bruno (Section 4.2.1), a Neoplatonist mystic who knew little about astronomy, had anything to do with his Copernican beliefs.
we must not forget that Copernicus had dedicated
De Revolutionibus
Finally,
to the Pope. During the sixteenth
century the Copernican issue was not considered important by the Church and no ocial pronouncements
were made.
Galileo's discoveries changed all that. Beginning with
Sidereus Nuncius
in 1610, Galileo brought the issue
before a wide audience. He continued his eorts, ever more boldly, in his letters on sunspots, and in his letter
to the Grand Duchess Christina (circulated in manuscript only) he actually interpreted the problematical
biblical passage in the book of Joshua to conform to a heliocentric cosmology. More importantly, he argued
that the Bible is written in the language of the common person who is not an expert in astronomy. Scripture,
he argued, teaches us how to go to heaven, not how the heavens go. At about the same time, Paolo Antonio
Foscarini (Section 4.2.4), a
Carmelite theologian in Naples, published a book in which he argued that the
Copernican theory did not conict with Scripture. It was at this point that Church ocials took notice of
the Copernican theory and placed
De Revolutionibus
on the Index of Forbidden Books (Section 4.1.2) until
corrected.
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Galileo's
Dialogue Concerning the Two Chief World Systems
of 1632 was a watershed in what had shaped
up to be the "Great Debate." Galileo's arguments undermined the physics and cosmology of Aristotle for an
increasingly receptive audience. His telescopic discoveries, although they did not
around the Sun, added greatly to his argument.
prove that the Earth moved
In the meantime, Johannes Kepler (Section 3.1.7) (who
had died in 1630) had introduced physical considerations into the heavens and had published his
Tables,
Rudolphine
based on his own elliptical theory and Tycho Brahe's (Section 3.1.10) accurate observations, and
these tables were more accurate by far than any previous ones. The tide now ran in favor of the heliocentric
theory, and from the middle of the seventeenth century there were few important astronomers who were not
Copernicans.
111
3.5.2 Ptolemaic System
Figure 3.77:
In his
Ptolemaic System
Dialogue Concerning the Two Chief World Systems, Ptolemaic and Copernican
of 1632, Galileo
attacked the world system based on the cosmology of Aristotle (384-322 BCE) and the technical astronomy
of Ptolemy (ca. 150 CE).
In his books
On the Heavens,
and
Physics,
Aristotle put forward his notion of an ordered universe or
cosmos. It was governed by the concept of place , as opposed to space, and was divided into two distinct
parts, the earthly or sublunary region, and the heavens. The former was the abode of change and corruption,
where things came into being, grew, matured, decayed, and died; the latter was the region of perfection,
where there was no change. In the sublunary region, substances were made up of the four elements, earth,
water, air, and re. Earth was the heaviest, and its natural place was the center of the cosmos; for that
reason the Earth was situated in the center of the cosmos. The natural places of water, air, and re, were
concentric spherical shells around the sphere of earth.
111 This
Things were not arranged perfectly, and therefore
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107
areas of land protruded above the water. Objects sought the natural place of the element that predominated
in them. Thus stones, in which earth predominated, move down to the center of the cosmos, and re moves
straight up. Natural motions were, then, radial, either down or up. The four elements diered from each
other only in their qualities. Thus, earth was cold and dry while air was warm and moist. Changing one or
both of its qualities, transmuted one element into another. Such transmutations were going on constantly,
adding to the constant change in this sublunary region.
Figure 3.78:
Ptolemy
The heavens, on the other hand, were made up of an entirely dierent substance, the aether
112 or
quintessence (fth element), an immutable substance. Heavenly bodies were part of spherical shells of aether.
These spherical shells t tightly around each other, without any spaces between them, in the following order:
Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn, xed stars.
Each spherical shell (hereafter, simply,
112 The
traditional English spelling, aether, is used here to distinguish Aristotle's heavenly substance from the modern chemical
substance, ether.
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CHAPTER 3. SCIENCE
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sphere) had its particular rotation, that accounted for the motion of the heavenly body contained in it.
Outside the sphere of the xed stars, there was the prime mover (himself unmoved), who imparted motion
from the outside inward. All motions in the cosmos came ultimately from this prime mover. The natural
motions of heavenly bodies and their spheres was perfectly circular, that is, circular and neither speeding up
nor slowing down.
It is to be noted about this universe that everything had its natural place, a privileged location for bodies
with a particular makeup, and that the laws of nature were not the same in the heavenly and the earthly
regions. Further, there were no empty places or vacua anywhere. Finally, it was nite: beyond the sphere
of the xed stars and the prime mover, there was nothing, not even space.
The cosmos encompassed all
existence.
Figure 3.79:
Christian Aristotelian Cosmos. From Peter Apian, Cosmographia113
Now, ingenious as this cosmology was, it turned out to be unsatisfactory for astronomy. Heavenly bodies
did, in fact, not move with perfect circular motions: they speeded up, slowed down, and in the cases of
the planets even stopped and reversed their motions. Although Aristotle and his contemporaries tried to
account for these variations by splitting individual planetary spheres into component spheres, each with
a component of the composite motion, these constructions were very complex and ultimately doomed to
failure. Furthermore, no matter how complex a system of spheres for an individual planet became, these
spheres were still centered on the Earth. The distance of a planet from the Earth could therefore not be
varied in this system, but planets vary in brightness, a variation especially noticeable for Venus, Mars, and
Jupiter. Since in an unchangeable heaven variations in intrinsic brightness were ruled out, and since spheres
did not allow for a variation in planetary distances from the Earth, variations in brightness could not be
accounted for in this system.
Thus, although Aristotle's spherical cosmology had a very long life, mathematicians who wished to make
geometrical models to account for the actual motions of heavenly bodies began using dierent constructions
within a century of Aristotle's death.
These constructions violated Aristotle's physical and cosmological
principles somewhat, but they were ultimately successful in accounting for the motions of heavenly bodies.
It is in the work of Claudius Ptolemy, who lived in the second century CE, that we see the culmination
of these eorts.
In his great astronomical work,
Almagest,
114 Ptolemy presented a complete system of
mathematical constructions that accounted successfully for the observed motion of each heavenly body.
Ptolemy used three basic constructions, the eccentric, the epicycle, and the equant. An eccentric construction is one in which the Earth is placed outside the center of the geometrical construction. Here, the
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114 The title is one given to this book by Islamic translators in the
Syntaxis.
ninth century. Its original Greek title is Mathematical
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109
Earth, E, is displaced slightly from the center, C, of the path of the planet.
Although this construction
violated the rule that the Earth was the center of the cosmos and all planetary motions, the displacement
was minimal and was considered a slight bending of the rule rather than a violation. The eccentric in the
gure below is xed; it could also be made movable. In this case the center of the large circle was a point
that rotated around the Earth in a small circle centered on the Earth. In some constructions this little circle
was not centered in the Earth.
The second construction, the epicycle, is geometrically equivalent to the simple movable eccentric.
In
this case, the planet moved on a little circle the center of which rotated on the circumference of the large
circle centered on the on theEarth. When the directions and speeds of rotation of the epicycle and large
circle were chosen appropriately, the planet, as seen from the Earth, would stop, reverse its course, and then
move forward again. Thus the annual retrograde motion of the planets (caused, in heliocentric terms by the
addition of the Earth's annual motion to the motion of the planet) could roughly be accounted for.
(a)
(b)
(c)
From Michael J. Crowe, Theories of the World from Antiquity to the Copernican
Revolution. (a) Eccentric115 (b) Epicycle116 (c) Equant117
Figure 3.80:
But these two constructions did not quite bring the resulting planetary motions within close agreement
with the observed motions.
Ptolemy therefore added yet a third construction, the equant.
In this case,
the center of construction of the large circle was separated from the center of motion of a point on its
circumference, as shown below, where C is the geometrical center of the large circle (usually called in these
constructions the excentric circle) but the motion of the center of the epicycle, P (middle of Figure 3.80), is
uniform about Q, the equant point (righthand side of Figure 3.80).
Ptolemy combined all three constructions in the models of the planets, Sun, and Moon.
A typical
construction might thus be as in the picture below, where E is the Earth, C the geometric center of the
eccentric circle, Q the equant point, F the center of the epicycle, and P the planet. As mentioned before,
the eccentric was often not xed but moved in a circle about the Earth or another point between the Earth
and the equant point.
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116 http://cnx.org/content/m11943/latest/epicycle_p.gif
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Typical Ptolemaic planetary model (From Michael J. Crowe, Theories of the World from
Antiquity to the Copernican Revolution.)118
Figure 3.81:
With such combinations of constructions, Ptolemy was able to account for the motions of heavenly bodies
within the standards of observational accuracy of his day. The idea was to break down the complex observed
planetary motion into components with perfect circular motions. In doing so, however, Ptolemy violated the
cosmological and physical rules of Aristotle. The excentric and epicycle meant that planetary motions were
not exactly centered on the Earth, the center of the cosmos. This was, however, a "fudge" that few objected
to. The equant violated the stricture of perfect circular motion, and this violation bothered thinkers a good
deal more. Thus, in
De Revolutionibus
(see Copernican System (Section 3.5.1)), Copernicus tells the reader
that it was his aim to rid the models of heavenly motions of this monstrous construction.
Aristotelian cosmology and Ptolemaic astronomy entered the West, in the twelfth and thirteenth centuries, as distinct textual traditions. The former in Aristotle's
commentaries on these works; the latter in the
Almagest
Physics and On the Heavens
and the many
and the technical astronomical literature that had
grown around it, especially the work of Islamic astronomers working in the Ptolemaic paradigm. In the world
of learning in the Christian West (settled in the universities founded around 1200 CE), Aristotle's cosmology
gured in all questions concerned with the nature of the universe and impinged on many philosophical and
theological questions. Ptolemy's astronomy was taught as part of the undergraduate mathematical curriculum only and impinged only on technical questions of calendrics, positional predictions, and astrology.
Copernicus's innovations was therefore not only putting the Sun in the center of the universe and working
out a complete astronomical system on this basis of this premise, but also trying to erase the disciplinary
boundary between the textual traditions of physical cosmology and technical astronomy.
119
3.5.3 Atomism
The notion that matter is made up of small, indivisible particles goes back to the ancient Greeks. In the sixth
century BCE, thinkers began asking questions about what is the basic underlying reality of the world. In
physis, hence our word
view of the constant change we see in the world around us, is there some substratum (
physics) that is constant? If so, is it material or immaterial, accessible through the senses or only through the
mind, is it one or many? Over the next several centuries, these questions were answered in several dierent
ways. Some believed that all was change, others that change was illusory. The Pythagoreans thought that
the physis was "number" and pioneered the mathematical approach to nature. Their idealist approach was
in stark contrast to that of the materialists, among whom the atomists were most prominent. Leucippus
of Miletus (ca.
435 BCE) and Democritus of Abdera (ca.
410 BCE) developed the atomic hypothesis.
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According to them matter can be subdivided only to a certain point, at which only atoms (that which
cannot be cut) remain. The world is made up of atoms moving in the void. Atoms diered from each other
only in size and shape, and dierent substances with their distinct qualities were made up of dierent shapes,
arrangements, and positions of atoms. Atoms were in continuous motion in the innite void and constantly
collided with each other. During these collisions they could rebound or stick together because of hooks and
barbs on their surfaces. Thus, underlying the changes in the perceptible world, there was constancy (atoms
were neither created nor destroyed); change was caused by the combinations and dissociations of the atoms.
Democritus gave some examples of how the atomic hypothesis could account for qualities such as color
and taste (sharp tastes are caused by sharp atoms), but on the whole atomism, like other contemporary
global theories, remained a general theory.
It was criticized by Aristotle (384-322 BCE) for some of its
120 and for its inability to explain qualities (color, taste, odor, etc.) that we call (after
logical inconsistencies
Galileo) secondary qualities. Aristotle's matter theory was fundamentally qualitative: qualities were built
into the fundamental building blocks that made up substances. And against the atomists' idea of a nature
without design or purpose, Aristotle constructed a natural philosophy that made nature a purposeful agent.
In the philosophical system of Epicurus (341-270 BCE), physics was subordinated to ethics. The aim
of his philosophy was to overcome irrational fears of natural phenomena and to achieve peace of mind.
Epicurus explained natural phenomena by atomism, but he made several modications to the doctrine in
view of Aristotle's criticisms.
atoms weight.
He distinguished between physical and mathematical divisibility and gave
In his system atoms originally fell through the innite void with equal speeds, until one
swerved by a tiny amount. This was an uncaused event. This swerve caused collisions and swirls of atoms,
and thus worlds were formed. The Epicurean ethical system was inuential over the next several centuries,
and one of its Roman practitioners, Lucretius (rst century BCE), wrote a long poem about it,
Natura
De Rerum
("On the Nature of Things"), from which much of our knowledge about atomism derives.
In the Christian world, nature was seen as the product of a transcendent creator and was therefore
fundamentally rational. Aristotelian notions of purpose and order t the Christian mindset much better.
Moreover, in atomism there was an unbridgeable gap between the level of the atoms and the observable
phenomena, whereas Aristotelian natural philosophy addressed observable phenomena directly. Aristotle did,
however, postulate
minima, the theoretical limit of divisibility of substances, and therefore within European
Aristotelianism, there was discussion about the meaning of this limit and in some quarters minima took on
a corpuscular nature.
Lucretius's
This train of thought merged with a revived atomism, caused by the recovery of
De Rerum Natura
ca. 1415 CE, to give rise to a corpuscular doctrine that provided the material
foundation of the mechanistic philosophy of the seventeenth century. We must be careful, however, not to
think that all those who sought causal explanations in the minute building blocks of matter were atomists.
Thus, Descartes (1596-1650) believed that matter was innitely divisible and had no weight (or mass).
In his
Assayer
of 1623, Galileo explained his notion of the dierence between those qualities, mostly found
by touch, that are inherent in bodies (weight, roughness, smoothness, etc.) and those that are in the mind of
the observer (taste, color, etc.)in other words, the dierence between what we call primary and secondary
qualities. In this discussion he referred to bodies that "continually dissolve into minute particles"
121 and
stated his opinion that "for exciting in us tastes, odors, and sounds there are required in external bodies
anything but sizes, shapes, numbers, and slow or fast movements."
122 An anonymous cleric led a report
with the Inquisition (Section 4.1.1) in which he claimed the rst citation to show that Galileo was an atomist
and the second to be in conict with the Council of Trent's pronunciations on the Eucharist.
123 The report
did not lead to any action against Galileo.
Galileo's notions about the constitution of matter emerge in his
Discourses on Two New Sciences
of 1638.
In his discussion of cohesionwhat holds matter togetherhe puts forward the notion that objects are made
120 If atoms have dierent shapes, then they have parts, and this means that they are mathematically divisible; if they have
dierent sizes, then among the innity of their number there must be atoms as big as the world.
121 Dtillman Drake and C. D. O'Malley, The Controversy over the Comets of 1618, (Philadelphia: University of Pennsylvania
Press, 1960), p. 310.
122 Ibid., p. 311.
123 Maurice A. Finocchiaro,The Galileo Aair: a Documentuary History, (Berkley and Los Angeles: University of California
Press, 1989) pp. 202-204. Pietro Redondi, Galileo Heretic, (Princeton: Princeton University Press, 1987), pp. 333-35.
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112
up of an innite number of innitely small particles held together by an innite number of small vacua. He
did not go beyond this point, but it is clear that this "atomism" is almost exclusively mathematical.
124
3.5.4 On Motion
During the time he taught the mathematical subjects at the university of Pisa (1589-1592), Galileo began a
book,
De motu
("On motion"), which was never published. In it, we can trace the early development of his
ideas concerning motion.
One of the fundamental propositions of Aristotelian philosophy is that there is no eect without a cause.
Applied to moving bodies, this proposition dictates that there is no motion without a force. Speed, then is
proportional to force and inversely proportional to resistance. This notion is not at all unreasonable if one
takes as one's dening case of motion, say, an ox pulling a cart: the cart only moves if the ox pulls, and
when the ox stops pulling the cart stops. For falling bodies, the force is the weight pulling down a body
and the resistance is that of the medium, air or water. As the science of motion became somewhat more
quantitative in the sixteenth century, some people began to investigate the motion of falling bodies more
carefully. Galileo was one of these.
If weight determines the speed of fall, then when two dierent weights are dropped from a high place the
heavier will fall faster and the lighter slower, in proportion to the two weights. A ten pound weight would
reach the Earth by the time a one-pound weight had fallen one-tenth as far.
One approach was to speculate: suppose one connected the two weights with a string, what would be
the speed of fall? Suppose one tied them together? In the rst case the lighter weight would slow down the
heavier one and therefore the time of fall would be greater than that of the heavier weight; in the second
case there now was a composite body weighing eleven pounds, whose time of fall would be less than that of
the ten-pound weight. Perhaps weight was not the determiner of the speed of fall.
But there was another approach, one of experience. Why not drop bodies of dierent weights and see
whether Aristotle's prediction was correct. As early as 1544, the historian Benedetto Varchi referred to actual
tests, which showed that it was not. In a tract written in 1576, Giuseppe Moletti, Galileo's predecessor in
the chair of mathematics at the university of Padua, reported that bodies of the same material but dierent
weight, as well as bodies of the same volume but dierent material, dropped from a height arrived at the
Earth at the same time.
Galileo's approach to this problem was somewhat dierent.
In
De motu
he proposed that in free fall
bodies dropped with a characteristic uniform speed determined not by their weight but by their specic
gravity (not his term). He put this theory to the test by dropping bodies from heights and found that the
experiments did not conrm his theory.
He states that, in fact, the lighter body (i.e.
that of the lower
specic gravity) will move ahead of the heavier body at the start of the fall, and that the heavier body then
overtakes it and arrives at the bottom slightly earlier.
Scholars have pointed to such passages to support their argument that Galileo did not perform such
experiments and that his references to experiments were only rhetorical devices.
After all, we all know
that in a vacuum all bodies would fall with the same speed and in a medium such as air the heavier body
(assuming the two bodies are of the same shape) will fall slightly faster: at no time will the lighter body be
ahead of the heavier one. But when Galileo's supposed experiment was repeated, the results showed that
he had described a real experiment. Students dropped spherical balls of wood and iron of equal diameter
and the wooden balls invariably moved ahead of the iron balls. The explanation lies in the fact that the
heavier iron ball must be clasped in the hand with more force and is therefore released slightly later than
the wooden ball.
Obviously, then, Galileo was performing experiments at the very beginning of his investigations into
motion, and he took his experimental results seriously. Over the next two decades he changed his ideas and
rened his experiments, and in the end he arrived at the law of falling bodies which states that in a vacuum
all bodies, regardless of their weight, shape, or specic gravity, are uniformly accelerated in exactly the same
way, and that the distance fallen is proportional to the square of the elapsed time.
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Chapter 4
Christianity
4.1 The Inquisition
1
4.1.1 The Inquisition
The Inquisition was a permanent institution in the Catholic Church charged with the eradication of heresies.
Unlike many other religions (e.g., Buddhism, Judaism), the Catholic Church has a hierarchical structure
with a central bureaucracy. In the early years of the church, there were several competing sects that called
themselves Christian.
But after the Emperor Constantine I (280?-337 CE) made Christianity the state
religion of the Roman Empire and the local administrative structures were pulled together into one hierarchy
centered in Rome, doctrinal arguments were settled by Church Councils, beginning with the Council of Nicea
in 325 (which formulated the Nicean Creed). Those whose beliefs or practices deviated suciently from the
orthodoxy of the councils now became the objects of eorts to bring them into the fold. Resistance often
led to persecution.
Heresies (from L.
haeresis, sect, school of belief ) were a problem for the Church from the beginning.
In
the early centuries there were the Arians and Manicheans; in the Middle Ages there were the Cathari and
Waldenses; and in the Renaissance there were the Hussites, Lutherans, Calvinists, and Rosicrucians. Eorts
to suppress heresies were initially ad hoc. But in the Middle Ages a permanent structure came into being to
deal with the problem. Beginning in the 12th century, Church Councils required secular rulers to prosecute
heretics.
In 1231, Pope Gregory IX published a decree which called for life imprisonment with salutary
penance for the heretic who had confessed and repented and capital punishment for those who persisted.
The secular authorities were to carry out the execution. Pope Gregory relieved the bishops and archbishops
of this obligation, and made it the duty of the
of other orders or of the secular clergy.
Dominican Order, though many inquisitors were members
By the end of the decade the Inquisition had become a general
institution in all lands under the purview of the Pope. By the end of the 13th centuries the Inquisition in
each region had a bureaucracy to help in its function.
The judge, or inquisitor, could bring suit against anyone.
The accused had to testify against him-
self/herself and not have the right to face and question his/her accuser. It was acceptable to take testimony
from criminals, persons of bad reputation, excommunicated people, and heretics. The accused did not have
right to counsel, and blood relationship did not exempt one from the duty to testify against the accused.
Sentences could not be appealed Sometimes inquisitors interrogated entire populations in their jurisdiction.
The inquisitor questioned the accused in the presence of at least two witnesses. The accused was given a
summary of the charges and had to take an oath to tell the truth.
Various means were used to get the
cooperation of the accused. Although there was no tradition of torture in Christian canon law, this method
came into use by the middle of the 13th century. The ndings of the Inquisition were read before a large
audience; the penitents abjured on their knees with one hand on a bible held by the inquisitor. Penalties
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114
went from visits to churches, pilgrimages, and wearing the cross of infamy to imprisonment (usually for life
but the sentences were often commuted) and (if the accused would not abjure) death. Death was by burning
at the stake, and it was carried out by the secular authorities. In some serious cases when the accused had
died before proceedings could be instituted, his or her remains could be exhumed and burned. Death or life
imprisonment was always accompanied by the conscation of all the accused's property.
Abuses by local Inquisitions early on led to reform and regulation by Rome, and in the 14th century
intervention by secular authorities became common. At the end of the 15th century, under Ferdinand and
Isabel, the Spanish inquisition became independent of Rome. In its dealings with converted Moslems and
Jews and also illuminists, the Spanish Inquisition with its notorious autos-da-fe represents a dark chapter in
the history of the Inquisition. In northern Europe the Inquisition was considerably more benign: in England
it was never instituted, and in the Scandinavian countries it had hardly any impact.
Pope Paul III established, in 1542, a permanent congregation staed with cardinals and other ocials,
whose task it was to maintain and defend the integrity of the faith and to examine and proscribe errors
and false doctrines. This body, the Congregation of the Holy Oce, now called the Congregation for the
Doctrine of the Faith, part of the Roman Curia, became the supervisory body of local Inquisitions. The Pope
himself holds the title of prefect but never exercises this oce. Instead, he appoints one of the
cardinals to
preside over the meetings. There are usually ten other cardinals on the Congregation, as well as a prelate
and two assistants all chosen from the Dominican order. The Holy Oce also has an international group
of consultants, experienced scholars of theology and canon law, who advise it on specic questions. In 1616
these consultants gave their assessment of the propositions that the Sun is immobile and at the center of the
universe and that the Earth moves around it, judging both to be "foolish and absurd in philosophy," and
the rst to be "formally heretical" and the second "at least erroneous in faith" in theology. This assessment
led to Copernicus's
De Revolutionibus Orbium Coelestium
to be placed on the Index of Forbidden Books,
until revised and Galileo to be admonished about his Copernicanism. It was this same body in 1633 that
tried Galileo.
2
4.1.2 The Congregation of the Index
Freedom of thought and written and oral expression is historically a relatively recent development.
For
those who were the shepherds of Christian souls and whose function it was to get those souls to heaven,
the idea that anyone could think and say or write what he/she wanted was an absurdity. Moreover, it was
dangerous because it might lead others into error. As early as 170 CE, the Church promulgated a list of
genuine books of the New Testament and excluded others from use in religious practice. In 405 CE, Pope
Innocent I published a list of forbidden books, and at the end of that century issued a decree that has been
called the rst Index of Forbidden Books. It listed the genuine books of the Bible, the apocryphal books,
and heretical books. Henceforth Popes and Councils periodically published lists of forbidden books.
With the Council of Trent (1545-1563), the Church instituted a permanent institution to deal with this
subject. The Congregation of the Inquisition (Section 4.1.1) was initially charged with drawing up a complete
list of forbidden books. This list, the rst general one, was published in 1559; it was the rst to be called
Index. It was immediately subject to revision by a papal commission, which published its result in 1564, the
Tridentine Index. This index also provided rules for censorship. For almost two centuries, the Index was
updated periodically without major revisions, but beginning in 1664 the Index listed forbidden books not
according to categories but simply alphabetically. In 1757 and 1897 there were major revisions in the general
norms governing censorship and prohibition. The last edition of the Index was that of 1948; it was abolished
in 1966. The Catholic Church has, however, not relinquished authority to forbid the reading of books that
in its judgment are a danger to the faith and morals of Catholics. Further, books listed on the 1948 Index
are not automatically permitted reading for Catholics. For many permission from Church authorities is still
required.
In the cases of the Copernican System (Section 3.5.1), the Church was slow to act because it did not see
immediate danger to the faithful in
2 This
De Revolutionibus
(1543). For one thing, it was written by a member
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115
of the Church. Copernicus was a
canon in a monastery,
and he dedicated his book to Pope Paul III. For
another, the book contained a preface (discovered by Kepler not to have been written by Copernicus) that
stated that the geocentric system proposed in the book was only a mathematical hypothesis and made no
claims about how the universe was really constituted.
But with Galileo's writings, which reached out to
a wide audience and brought the argument about Copernicus into the mainstream of educated discourse,
the Church acted.
In 1616, after 73 years, it placed
De Revolutionibus
along with several other books that defended the Copernican System.
on the Index subject to revision,
It is interesting to note that the
revisions required in Copernicus's book were, in terms of the total work, actually very minor. Copies of
Revolutionibus
De
that were in Italy at this time show the revisions: a few deleted passages and a few changes
of individual words. None of Galileo's books were placed on the Index at this time. Kepler's (Section 3.1.7)
New Astronomy,
his
Epitome of Copernican Astronomy,
and his
World Harmony were quickly placed on
Concerning the Two Chief Systems
the Index. During the proceedings against Galileo in 1633, his Dialogue
of the World
was placed on the Index, where it remained until 1824.
4.2 Church Figures
3
4.2.1 Giordano Bruno (1548-1600)
Giordano Bruno
Figure 4.1:
frontispiece.
Christian Bartholméss, Jordano Bruno (Paris: Libaririe Philosophique de Ladrange, 1846),
Filippo Bruno was born in Nola, near Naples, the son of Giovanni Bruno, a soldier, and Fraulissa Savolino.
He took the name Giordano upon entering the Dominican order.
In the great Dominican monastery in
Naples (where Thomas Aquinas had taught), Bruno was instructed in Aristotelian philosophy. His exceptional expertise in the art of memory brought him to the attention of patrons, and he was brought to Rome
to demonstrate his abilities to the Pope. During this period he may also have come under the inuence of
Giovanni Battista Della Porta, a Neapolitan
polymath who published an important book on natural magic.
Bruno was attracted to new streams of thought, among which were the works of Plato and Hermes Trismegistus, both resurrected in Florence by Marsilio Ficino in the late fteenth century. Hermes Trismegistus
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116
was thought to be a gentile prophet who was a contemporary of Moses. The works attributed to him in fact
date from the turn of the Christian era.
Because of his heterodox tendencies, Bruno came to the attention of the Inquisition (Section 4.1.1) in
Naples and in 1576 he left the city to escape prosecution.
When the same happened in Rome, he ed
again, this time abandoning his Dominican habit. For the next seven years he lived in France, lecturing on
various subjects and attracting the attention of powerful patrons. From 1583 to 1585 he lived at the house
of the French ambassador in London. During this period he published the books that are most important
for our purposes,
Cena de le Ceneri
De l'Innito, Universo e Mondi
Cena de le Ceneri, Bruno defended
("The Ash Wednesday Supper") and
("On the Innite Universe and Worlds"), both published in 1584. In
the heliocentric theory of Copernicus (Section 3.5.1) .
It appears that he did not understand astronomy
very well, for his theory is confused on several points. In De l'Innito , Universo e Mondi, he argued that
the universe was innite, that it contained an innite number of worlds, and that these are all inhabited by
intelligent beings.
Wherever he went, Bruno's passionate utterings led to opposition. During his English period he outraged
the Oxford faculty in a lecture at the university; upon his return to France, in 1585, he got into a violent
quarrel about a scientic instrument.
Prague, Helmstedt, and Frankfurt.
He ed Paris for Germany in 1586, where he lived in Wittenberg,
As he had in France and England, he lived o the municence of
patrons, whom after some time he invariably outraged. In 1591 he accepted an invitation to live in Venice.
Here he was arrested by the Inquisition and tried. After he had recanted, Bruno was sent to Rome, in 1592,
for another trial. For eight years he was kept imprisoned and interrogated periodically. When, in the end,
he refused to recant, he was declared a heretic and burned at the stake.
It is often maintained that Bruno was executed because of his Copernicanism and his belief in the innity
of inhabited worlds. In fact, we do not know the exact grounds on which he was declared a heretic because
his le is missing from the records. Scientists such as Galileo and Johannes Kepler (Section 3.1.7) were not
sympathetic to Bruno in their writings.
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4
4.2.2 Robert Cardinal
Figure 4.2:
Robert Cardinal Bellarmine
Roberto Bellarmino was born into a noble family in Montepulciano in Tuscany (Section 1.4.1).
In 1560,
he joined the Jesuit order and began his studies at the Collegio Romano (Section 1.2.1), the Jesuit college
in Rome. After nishing his course of studies there and studying Thomistic theology at the university of
Padua, Bellarmine became the rst Jesuit professor at the university of Louvain (in modern Belgium) in 1569
and was ordained as a priest the following year. Situated in the Low Countries where Protestantism was
gaining rapidly during this period, the university of Louvain was becomes a bulwark of Catholic orthodoxy.
Bellarmine taught theology out of Thomas Acquinas's
Summa Theologica
and studied the Scriptures and
the Church Fathers in preparation for a major work on theology. During his period at Louvain he wrote a
Hebrew grammar and a work on the Church Fathers.
In 1576 Bellarmine was called back to Rome by Pope Gregory XIII to teach theology to English and
German missionaries at the Collegio Romano. He taught there until 1588. Toward the end of this period,
his most important scholarly work began appearing:
Disputationes de Controversiis Christianae Fidei Adversus Hujus Temporis Haereticos
(Disputations
about the Controversies of the Christian faith Against the Heretics of this Time) (3 vols, Ingolstadt, 15861593). In this work, Bellarmine brought order to the chaos of theological arguments between Catholics and
Protestants. Whereas the literature on this subject was marked by heated debates and intemperate statements on both sides, Bellarmine calmly and fairly reviewed the issues. These volumes became a remarkably
eective weapon against reform theology, and it has been argued that they occasioned the return of many
to the Catholic Church.
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In 1588 Bellarmine became the spiritual director of the Collegio Romano (Section 1.2.1).
Among his
Dottrina
Cristiani Breve (Brief Christian Doctrine) Rome, 1597), a small catechism for children, and Dichiarazione
piX Copiosa della Dottrina Cristiani (A more copious declaration of the Christian doctrine) (Rome, 1598),
other duties he taught the catechism to students and lay brothers, and his lessons eventually led to
a catechism for teachers. Approved by Pope Clement XIII, both catechisms became very popular and were
translated into many languages. Their popularity lasted well into the twentieth century.
Bellarmine served as rector of the Collegio Romano in 1592, as provincial of the Neapolitan province of
the Jesuits in 1594, and papal theologian in 1597. In 1599 he was made a cardinal. From this time forward
he was a member of the Roman Congregation and served on many commissions. In 1602 he was consecrated
an archbishop and sent by Pope Clement VIII to Capua, where he concerned himself mainly with pastoral
duties. In 1605 he was recalled to Rome.
Bellarmine spent much of his time in theological controversies, mostly involving papal power. He engaged
in a public debate, a war of books and pamphlets, concerning the divine right of kings with James I of
England.
The issue of papal power revolved around the theory of the indirect power of the Pope.
His
spiritual power is direct and primary; he was not, however, without temporal power because he might have
to act with regard to temporal things which aected the spiritual ones. This was the Pope's indirect power,
which Bellarmine defended all his adult life.
In 1616 Bellarmine became involved in the Copernican controversy, which was brought to a head by
the publication of Paolo Antonio Foscarini's book defending the Copernican system from the charge that it
clashed with the Scriptures. It was he who administered the controversial admonition to Galileo not to hold
or defend the Copernican theory (Section 3.5.1).
In a time when cardinals maintained splendid courts, Bellarmine lived a simple and ascetic life, practicing
self-sacrice, poverty, and disinterestedness. Upon the death of Pope Sixtus V in 1590, the Count of Olivares
wrote to King Philip III of Spain about possible candidates for the papacy: "Bellarmine is beloved for his
great goodness, but he is a scholar who lives only among books and not of much practical ability . . . . He
would not do for a Pope, for he is mindful only of the interests of the Church and is unresponsive to the
reasons of princes . . . He would scruple to accept gifts . . . I suggest that we exert no action in his favor."
The King agreed.
The process of canonization was begun in 1627.
In 1931 Pope Pius XI nally declared Bellarmine a
Doctor of the Church.
5
4.2.3 Tommaso Caccini
Cosimo Caccini was born in Florence (Section 1.4.1) and chose the religious life before he had turned fteen.
Caccini chose the
Dominican order
and entered the monastery of San Marco.
Here, a century earlier,
Savanarola had been the prior, and the legacy of this monk's ery sermons lived on. Caccini soon showed
that he had a talent for preaching, and soon after his novitiate he was already preaching Lenten sermons in
the church of Santa Maria Novella. As his reputation spread, he was invited by churches in other cities to
perform the same oce. Caccini was, however, a pale echo of Savanarola: his fanaticism was never divorced
from personal ambition for advancement within the Dominican order. By his choice of the name Tommaso,
he served notice that he wished to become the new Thomas Aquinas, the order's (and the Church's) greatest
theologian. In fact, his published works were derivative and third-rate. For his inammatory sermons he
was disciplined by the Archbishop of Bologna as a scandal-maker.
Shortly after Galileo's arrival in Florence, Caccini fell in with the so-called "Pigeon League," named after
6 an arch-enemy of Galileo. The group included his fellow Dominican Niccolo Lorini
Lodovico delle Colombe,
and the Archbishop of Florence. Lorini was the rst to attack Galileo from the pulpit, toward the end of
1612, but in the face of an uproar among the friends of Galileo quickly wrote a letter of apology. Caccini's
attack was more damaging. Because of the inuence of his brother Matteo, Caccini had been prior of the
Dominican monastery in Cortona in 1611, where he had been unsuccessful in obtaining the patronage of
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Cardinal Maeo Barberini, and he now had further aspirations in Rome. He was in possession of a copy of
Galileo's letter to Benedetto Castelli (Section 3.1.6) (which Galileo later expanded into the "Letter to the
Grand Duchess Christina") showing how the Copernican system (Section 3.5.1) could be reconciled with the
passage in the book of
Joshua.
Here was Caccini's chance. On the fourth Sunday of Advent (20 December
1614), he preached a sermon on
Copernican views.
of the Apostles,
Joshua
in Santa Maria Novella in Florence, attacking Galileo and for his
He reputedly ended his sermon with a passage from chapter 1, verse 11 of
The Acts
"Viri galilaei, quid statis adspicientes in caelum?" which is rendered in the King James
translation as "Ye men of Galilee, why stand ye gazing up into heaven?" an obvious reference to Galileo and
his followers.
Caccini got his wish. He became Master and Bachelor of the convent of Santa Maria sopra Minerva in
Rome, and the wheels were set in motion that resulted, eighteen months later, in the condemnation of the
Copernican theory. Lorini forwarded a mangled copy of Galileo's letter to Castelli to Rome, and Galileo then
sent the correct original version to Rome as well. In March 1615 Caccini appeared on his own initiative before
the Inquisition (Section 4.1.1) and gave depositions about Galileo and his views. In November, two other
clerics mentioned in Caccini's deposition were examined in Florence. These depositions show how ignorant
these men were, in fact, about Galileo's views. After reviewing the matter, the Holy Oce decided not to
take any actions other than having Galileo's letters on sunspots examined by its theological consultants.
Their report, in February 1616, made the proposition of a stationary and central Sun formally heretical and
the proposition of a non-central moving Earth "at least erroneous in faith."
From correspondence, it appears that Caccini kept working against Galileo behind the scenes, but apparently to no particular eect. His career, however, did progress. He became confessor to the nuns of the
convent of Orsina, and then penitentiary at Santa Maria Maggiore in Rome. He was conned for some time
in Viterbo, after which, through the help of his brothers, he was allowed to return to Florence (Section 1.4.1)
where he became a high theologian of the Dominican order. As prior of the famous monastery of San Marco,
he was active behind the scene in the events leading up to Galileo's trial in 1633. Caccini died in Florence
in 1648.
4.2.4 Paolo Antonio Foscarini
7
Little is known about Foscarini's life. He was born in Montalto Uugo in Calabria (southern Italy), joined
the
Carmelite Order, and distinguished himself as a preacher, mathematician, and theologian.
He taught
philosophy and theology at the university of Messina in Sicily served as the elected provincial of the Carmelite
Ordinationes et Exercitia Quotidiana ("Daily Ordinations and Exercises")
Institutionum Omnis Generis Doctrinarum Tomis VII Comprehensarum Syntaxis ("Syntaxis of All
of Doctrines, Contained in Seven Tomes") in 1613; and Tratato della Divinatione Naturale Cosmo-
Order in Calabria. He published
in 1607;
Types
logica
("Treatise on Natural Cosmological Divination") in 1615.
In that year, he turned his attention to the Copernican System (Section 3.5.1), and there is some evidence
that he and Galileo planned a joined strategy on behalf of heliocentric cosmology. As Galileo wrote his "Letter
Lettera sopra l'Opinione de'
Pittagorici, e del Copernico della Mobilita della Terra, e Stabilita del Sole, e del Nuove Pittagorica Systema
del Mondo ("Letter concerning the Opinion of the Pythagoreans and Copernicus about the Mobility of the
to the Grand Duchess Christina," Foscarini published in Naples a tract entitled
Earth and Stability of the Sun, and about the New Pythagorean System of the World"), dedicated to the
General of the Carmelite Order. In this work, Foscarini defended the Copernican theory as true and defended
it against charges that it conicted with Scripture. With book in hand, Foscarini went to Rome to defend the
Copernican theory personally but left Rome before Galileo's arrival there. Shortly afterward, the consultants
of the Holy Oce made their pronouncement on the Copernican theory, and as a result Foscarini's book was
placed on the Index of Forbidden Books (Section 4.1.2) (3 March 1616). Foscarini died a few months later
in a Carmelite monastery he had founded in his native city of Montalto.
7 This
content is available online at <http://cnx.org/content/m11966/1.2/>.
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GLOSSARY
120
Glossary
A
archbishop
their natural colors on a surface arranged
to receive them.
- A bishop of the highest rank who
canon
presides over an archbishopric or
archdioscese.
- One of a body of dignitaries attached to
armillary sphere
a cathedral or a collegiate church, or a
member of certain religious orders.
- An instrument consisting of an
cardinal
arrangement of rings, all of which are
circles of the same sphere, used to show
- High ecclesiastic appointed by the pope
the relative positions of the celestial
to the College of Cardinals and ranking
equator, ecliptic, and other circles of the
above every other ecclesiastic but the
clestial sphere.
pope.
atmospheric refraction
Carmelite Order
- The change in direction of a ray of light
- The Brothers of the Blessed Virgin Mary
as it passes from space into the
of Mount Carmel is one of the mendicant
atmosphere. This causes celestial objects
orders originating on Mount Carmel in
to appear to be in a location dierent
Israel.
from their actual ones.
Carmelite Order
atmospheric refraction
The Brothers of the Blessed Virgin Mary
The change in direction of a ray of light as
of Mount Carmel is one of the mendicant
it passes from space into the atmosphere.
orders originating on Mount Carmel in
This causes celestial objects to appear to
Israel.
be in a location dierent from their
Counter Reformation
actual ones.
- As dissenting groups split o from the
B
Benedictine Order
Catholic Church in what came to be
known as the Protestant Reformation,
- The Order of Saint Benedict is a
the Church began a series of reform
confederation of congegations of monks
measures of their own. These reform
and nuns, not a centralized religious
measures aimed to keep Church members
order. Each monastary is an autonomous
from becoming Protestants, and were
community following the rule of Benedict
known as the Counter Reformation.
of Nursia.
Counter Reformation
bishop
As dissenting groups split o from the
- The priest who acts as the highest
Catholic Church in what came to be
religious ocial in a diosces. One of the
known as the Protestant Reformation,
principal functions of the bishop was to
the Church began a series of reform
celebrate the Eucharist.
C
measures of their own. These reform
measures aimed to keep Church members
camera obscura
from becoming Protestants, and were
known as the Counter Reformation.
- A darkened boxlike device in which
images of external objects, received
through an aperture, are exhibited in
D
diosces
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GLOSSARY
121
parallax
- An area of land dened by the fact that
all of the priests are responsible to a
- The change in the position of an object
single bishop.
in the heavens due to the orbit of the
Dominican Order
earth. Observable parallax in the xed
stars is a proof of the rotation of the
- The popular name for the Order of Friars
earth around the sun.
Preachers. The order was founded by
parallax
Domingo de Guzman (known as
Dominic) between 1215 and 1221. Like
The change in the position of an object in
the Franciscans, the Dominicans were
the heavens due to the orbit of the earth.
mendicant friars.
Observable parallax in the xed stars is a
Dominican Order
H
proof of the rotation of the earth around
the sun. See this explanatory diagram.
patrician class
harmonic oscillator
- The aristocracy or nobles.
Each oscillation has a frequency that is an
peripatetic
integer multiple of the same basic
frequency
I
- Walking or travelling about. Of or
pertaining to Aristotle, or the
isochronous
Aristotelian school of philosophy, who
taught philosophy while walking in the
Equal or uniform in time
Lyceum in ancient Athens.
J
Jesuits
polymath
- A person of great learning in several
- The popular name for the monastic order
elds of study.
called the Society of Jesus. The order
polymath
polymath
was founded by Ignatius de Loyola in
1534, and was recognized by the pope in
1540. The mission of the Jesuits was in
three areas: teaching, service to the
A person of great learning in several elds
nobility, and missionary work in foreign
of study.
prefect
lands. Their greatest mark was made in
education, and the Collegio Romano
- A cardinal in charge of a congregation in
(Section 1.2.1) was their primary
the Curia Romana.
seminary.
L
Prothonotary Apostolic
- A member of the rst college of prelates
lunar librations
of the Roman Curia. Charged chiey
- The real or apparent oscillatory motion
with the registry of pontical acts and
of the moon.
O
canonizations. Also an honorary title for
certain other prelates.
opposition
Provincial
- The situation of two heavenly bodies
The head of an ecclesiastical province, or a
when their longitudes or right ascensions
member of a religious order presiding over
dier by 180? The moon is in opposition
the order in a given district or province.
to the sun when the earth is directly
between them.
P
Q
quadrature
- Those points or moments at which a half
papal legate
moon is visible. More generally, it is the
- An ecclesiastic delegated by the pope as
his representative.
situation of two heavenly bodies when
their longitudes dier by 90?
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GLOSSARY
122
R
retrograde planetary motion
practice as a priest, refuting the order. In
the end, Savonarola was tortured and in
- At times the planets appear to be
1498 was hanged.
moving opposite to their direction of
sidereal period
rotation. This is caused by the eect of
the rotation of the earth on our
- A period determined by or from the
observations of the other planets.
S
stars.
specic gravity
Savonarola, Girolamo
- The ratio of the density of any substance
- A Dominican friar, prior of the convent
to the density of some other substance
of San Marco in Florence, Savonarola
taken as standard, with water being the
believed that he was sent as a watchman
standard for solids.
for God to warn people of impending
synod
doom. His power was such that when the
Medici family was expelled in 1494, he
- An assembly of ecclesiastics or other
ruled the city and became a major power
church delegates, convoked pursuant to
in Italy. In 1496, he turned against the
the law of the church, for the discussion
pope, after the pope attempted to control
and decision of ecclesiastical aairs. A
the prior's power by oering a cardinal's
council within the Church. Diocesan
oce. In 1497, the pope excommunicated
councils consisted of the presbyters of a
Savonarola. Savonarola continued to
dioscese meeting under the presidency of
practice as a priest, refuting the order. In
the bishop. Provincial councils consisted
the end, Savonarola was tortured and in
of all the diosces in an ecclesiastical
1498 was hanged.
province, with the provincial in the role
Savonarola, Girolamo
of the pre sident over the bishops of the
province. Plenary councils were councils
A Dominican friar, prior of the convent of
of several provinces. Patriarchal councils
San Marco in Florence, Savonarola
were of the provinces united in one
believed that he was sent as a watchman
patriarchate. The provinces in a country
for God to warn people of impending
could form a national council. General
doom. His power was such that when the
councils could be of the East or West, or
Medici family was expelled in 1494, he
of the whole Church. Finally, Ecumenical
ruled the city and became a major power
Councils were those whose decisions were
in Italy. In 1496, he turned against the
accepted by the Church as a whole.
pope, after the pope attempted to control
the prior's power by oering a cardinal's
oce. In 1497, the pope excommunicated
Savonarola. Savonarola continued to
V
vicariat
- The oce or authority of a vicar.
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[137] Pietro Redondi.
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a useful, if
eccentric biography of Copernicus with a collection of documents concerning his life.
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Isis,
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[161] John W. Shirley.
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[162] Charles Singer. "the earliest gures of microscopic objects".
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[165] Bruce Stephenson.
[166] John Tedeschi.
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[179] Frances Yates. No title given.
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INDEX
132
Index of Keywords and Terms
Keywords are listed by the section with that keyword (page numbers are in parentheses).
Keywords
do not necessarily appear in the text of the page. They are merely associated with that section.
apples, Ÿ 1.1 (1)
Terms are referenced by the page they appear on.
A Accademia dei Lincei, Ÿ 1.2.2(4)
Ex.
Collegio Romano, Ÿ 1.3.4(15), Ÿ 3.1.13(51),
aerial telescopes, 69
Ÿ 3.4.1(71), Ÿ 4.2.2(116)
Antonio, Ÿ 4.2.4(119)
comet, Ÿ 3.1.10(41), Ÿ 3.4.6(92)
archbishop, Ÿ 1.3.4(15), 16
Congregation, Ÿ 4.1.2(114)
armillary sphere, Ÿ 1.3.2(6), 9
Copernican, Ÿ 3.1.7(34), Ÿ 3.1.8(38),
atmospheric refraction, Ÿ 3.1.7(34), 37,
Ÿ 3.4.5(90), Ÿ 3.5.1(101), Ÿ 4.2.4(119)
Ÿ 3.1.10(41), 45
Copernican system, Ÿ (1), Ÿ 1.4.2(18),
atomism, Ÿ 3.1.3(29), Ÿ 3.5.3(110)
Ÿ 3.1.3(29), Ÿ 3.1.10(41), Ÿ 3.1.13(51),
Ÿ 3.4.2(75), Ÿ 3.4.3(81), Ÿ 3.5.2(106),
B Balance, Ÿ 3.3.2(57)
Ÿ 4.1.2(114), Ÿ 4.2.3(118)
Barberini, Ÿ 1.3.4(15)
Copernican System., Ÿ 3.1.6(33)
Bellarmine, Ÿ 4.2.2(116)
Copernican theory, Ÿ 1.3.4(15), Ÿ 3.1.14(53),
Benedetto Castelli, Ÿ 3.3.5(61), Ÿ 3.4.2(75),
Ÿ 3.4.1(71)
Ÿ 4.2.3(118)
Copernicus, Ÿ 3.3.6(63), Ÿ 4.2.1(115)
Benedictine, Ÿ 3.1.6(33)
Cosimo II, Ÿ 3.4.3(81)
Benedictine order, 33
cosmology, Ÿ 3.1.8(38)
Biography, Ÿ (1)
Counter Reformation, Ÿ 3.1.7(34), 35, 37,
bishop, Ÿ 1.3.4(15), 16
Ÿ 3.5.1(101), 105
books, Ÿ 4.1.2(114)
Brahe, Ÿ 3.1.10(41)
D David, Ÿ 3.1.4(30)
Bruno, Ÿ 4.2.1(115)
David Fabricius, Ÿ 3.1.9(39), Ÿ 3.4.2(75)
De Motu, Ÿ (1)
C Caccini, Ÿ 4.2.3(118)
dioceses, 16
Callisto, Ÿ 3.4.3(81)
diosceses, Ÿ 1.3.4(15)
camera obscura, Ÿ 3.1.4(30), 30, Ÿ 3.4.2(75), 75
Dominican, Ÿ 4.2.3(118)
Campanella, Ÿ 3.1.3(29)
Dominican order, Ÿ 3.1.3(29), 30, Ÿ 4.1.1(113),
canon, Ÿ 4.1.2(114), 115
113, 118
Cardinal, Ÿ 4.2.2(116)
Duke of Mantua, Ÿ 1.3.1(6)
Cardinal Bellarmine, Ÿ (1)
Cardinal Maeo Barberini, Ÿ 2.2(22)
cardinals, Ÿ 1.3.4(15), 16, Ÿ 4.1.1(113), 114
Carmelite, Ÿ 3.5.1(101), 105
Carmelite Order, Ÿ 4.2.4(119), 119
Castelli, Ÿ 3.1.6(33)
Celeste, Ÿ 2.2(22), Ÿ 2.3(24)
Cesi, Ÿ 1.2.2(4)
Christianity, Ÿ 4.1.1(113), Ÿ 4.2.1(115),
Ÿ 4.2.2(116)
Christoph, Ÿ 3.1.14(53)
Christoph Clavius, Ÿ 3.4.1(71), Ÿ 3.5.1(101)
Christoph Scheiner, Ÿ 3.1.4(30), Ÿ 3.4.2(75)
Clavius, Ÿ 3.1.13(51)
Ex.
apples, 1
E
Europa, Ÿ 3.4.3(81)
F
Fabricius, Ÿ 3.1.4(30)
Florence, Ÿ (1), Ÿ 1.3.4(15), Ÿ 1.4.1(17),
Ÿ 1.4.2(18), Ÿ 2.1(21), Ÿ 2.3(24), Ÿ 3.3.1(56),
Ÿ 3.4.2(75), Ÿ 4.2.3(118)
forbidden, Ÿ 4.1.2(114)
Foscarini, Ÿ 4.2.4(119)
G Galiileo, Ÿ 3.5.2(106)
Galilei, Ÿ (1), Ÿ 1.1(3)
Galileo, Ÿ (1), Ÿ 1.1(3), Ÿ 1.3.1(6), Ÿ 1.3.3(13),
Ÿ 1.3.4(15), Ÿ 1.4.1(17), Ÿ 1.4.2(18), Ÿ 2.1(21),
Available for free at Connexions <http://cnx.org/content/col10234/1.1>
INDEX
133
Ÿ 2.2(22), Ÿ 2.3(24), Ÿ 3.1.1(27), Ÿ 3.1.2(28),
longitude, Ÿ 3.4.1(71)
Ÿ 3.1.4(30), Ÿ 3.1.5(31), Ÿ 3.1.6(33), Ÿ 3.1.7(34),
longitude at sea, Ÿ 3.4.3(81), Ÿ 3.4.7(97)
Ÿ 3.1.8(38), Ÿ 3.1.9(39), Ÿ 3.1.10(41),
lunar librations, Ÿ 3.4.1(71), 73
Ÿ 3.1.11(46), Ÿ 3.1.12(49), Ÿ 3.1.13(51),
Lyncean Academy, Ÿ 3.1.5(31), Ÿ 3.1.14(53),
Ÿ 3.1.14(53), Ÿ 3.3.1(56), Ÿ 3.3.2(57),
Ÿ 3.4.2(75)
Ÿ 3.3.3(57), Ÿ 3.3.4(60), Ÿ 3.3.6(63), Ÿ 3.4.1(71),
Ÿ 3.4.2(75), Ÿ 3.4.4(84), Ÿ 3.4.5(90), Ÿ 3.4.6(92),
M Maeo, Ÿ 1.3.4(15)
Maeo Barberini, Ÿ 3.4.5(90)
Ÿ 3.4.7(97), Ÿ 3.5.3(110), Ÿ 3.5.4(112),
Marc, Ÿ 3.1.5(31)
Ÿ 4.1.1(113), Ÿ 4.2.1(115), Ÿ 4.2.2(116),
Marc Welser, Ÿ 3.1.14(53), Ÿ 3.4.2(75)
Ÿ 4.2.3(118), Ÿ 4.2.4(119)
Maria, Ÿ 2.2(22), Ÿ 2.3(24)
Gamba, Ÿ 2.2(22), Ÿ 2.3(24)
Marina, Ÿ 2.3(24)
Ganymede, Ÿ 3.4.3(81)
Marina Gamba, Ÿ (1)
geocentric, Ÿ (1)
Marius, Ÿ 3.1.9(39)
geocentric astronomy, Ÿ 3.3.6(63)
Medici, Ÿ (1), Ÿ 1.4.1(17), Ÿ 2.3(24), Ÿ 3.4.4(84)
Gilbert, Ÿ 3.1.8(38)
Medici Family, Ÿ 1.3.2(6)
Giordano, Ÿ 4.2.1(115)
moon, Ÿ (1), Ÿ 3.1.12(49), Ÿ 3.1.13(51),
Giordano Bruno, Ÿ 1.4.2(18), Ÿ 3.1.4(30),
Ÿ 3.3.6(63), Ÿ 3.4.1(71), Ÿ 3.4.3(81), Ÿ 3.4.4(84),
Ÿ 3.5.1(101)
Ÿ 3.4.6(92)
Giovanni, Ÿ 1.3.2(6)
myopia, 65
Gregorian calendar, Ÿ 3.1.13(51)
O On Motion, Ÿ 3.5.4(112)
H Hans, Ÿ 3.1.1(27)
opposition, Ÿ 3.1.10(41), 45
Hans Lipperhey, Ÿ 3.3.6(63)
harmonic oscillator, Ÿ 3.3.3(57), 59
Harriot, Ÿ 3.1.12(49)
Hydrostatic, Ÿ 3.3.2(57)
hydrostatic balance, Ÿ (1)
I
Index, Ÿ 4.1.2(114)
Index of Forbidden Books, Ÿ 3.5.1(101),
Ÿ 4.2.4(119)
Inquisition, Ÿ (1), Ÿ 1.3.2(6), Ÿ 3.1.3(29),
Ÿ 4.1.1(113), Ÿ 4.1.2(114), Ÿ 4.2.1(115),
Ÿ 4.2.3(118)
isochronism, Ÿ 3.3.3(57), 58
Italy, Ÿ (1), Ÿ 1.4.1(17)
Paolo Antonio Foscarini, Ÿ 3.5.1(101)
Paolo Sarpi, Ÿ 3.1.2(28)
papal legate, Ÿ 1.3.4(15), 16
parallax, Ÿ 3.4.6(92), 95, 104
patrician class, Ÿ 1.3.2(6), 7
patron, Ÿ 1.3.1(6)
pendulum, Ÿ (1), Ÿ 3.3.3(57)
peripatetic, Ÿ 3.1.3(29), 30
polymath, Ÿ 1.2.2(4), 5, 5, Ÿ 3.1.3(29), 30,
Pope, Ÿ 1.3.4(15)
Pope Urban VIII, Ÿ (1)
prefect, Ÿ 1.3.4(15), 16
Jesuit, Ÿ 3.1.13(51), 52, Ÿ 3.1.14(53), 54,
presbyopia, 64
Ÿ 3.4.1(71), 72
Prothonotary Apostolic, Ÿ 1.3.4(15)
Jesuits, Ÿ 1.3.4(15), 16
Protonotary Apostolic, 16
Johannes, Ÿ 3.1.4(30), Ÿ 3.1.7(34), Ÿ 3.1.8(38)
Provincial, Ÿ 1.3.3(13), 14
Johannes Kepler, Ÿ 3.1.10(41), Ÿ 3.1.12(49),
Ptolemaic, Ÿ 3.4.5(90)
Ÿ 3.1.14(53), Ÿ 3.3.6(63), Ÿ 3.4.2(75),
Ptolemaic arrangement, Ÿ 3.1.10(41)
Ÿ 3.4.3(81), Ÿ 3.5.1(101), Ÿ 4.2.1(115)
Ptolemaic System, Ÿ 3.1.13(51), Ÿ 3.5.2(106)
Jupiter, Ÿ 3.1.13(51), Ÿ 3.4.3(81)
Ptolemy, Ÿ 3.1.9(39), Ÿ 3.5.1(101)
Jupiter's satellites, Ÿ 3.1.7(34), Ÿ 3.1.9(39)
pump, Ÿ (1), Ÿ 3.3.1(56)
K Kepler, Ÿ 3.1.4(30), Ÿ 3.1.7(34), Ÿ 3.1.8(38),
Ÿ 3.4.5(90), Ÿ 4.1.2(114)
L
Paolo, Ÿ 1.3.3(13), Ÿ 4.2.4(119)
Ÿ 4.2.1(115), 115
Io, Ÿ 3.4.3(81)
J
P
Q quadrature, Ÿ 3.1.10(41), 45
R retrograde planetary motion, Ÿ 3.1.10(41), 46
lenses, 64
Robert, Ÿ 4.2.2(116)
Lipperhey, Ÿ 3.1.1(27)
Robert Bellarmine, Ÿ 1.3.3(13)
Available for free at Connexions <http://cnx.org/content/col10234/1.1>
INDEX
134
S
Santorio, Ÿ 3.1.2(28), Ÿ 3.3.5(61)
Ÿ 3.3.6(63), Ÿ 3.4.1(71), Ÿ 3.4.2(75), Ÿ 3.4.3(81),
Sarpi, Ÿ 1.3.3(13)
Ÿ 3.4.7(97)
Satellites, Ÿ 3.4.3(81)
telescopes, Ÿ 1.3.3(13)
satellites of Jupiter, Ÿ (1), Ÿ 3.3.6(63),
theory, Ÿ 3.5.3(110)
Ÿ 3.4.7(97)
Thermometer, Ÿ 3.3.5(61)
Saturn, Ÿ 3.4.4(84)
Thomas, Ÿ 3.1.12(49)
Savanarola, Ÿ 1.3.2(6)
Thomas Harriot, Ÿ 3.4.1(71), Ÿ 3.4.2(75)
Savonarola, Ÿ 1.4.1(17), 18
tides, Ÿ 1.3.3(13), Ÿ 3.4.5(90)
Scheiner, Ÿ 3.1.14(53)
Tomasso Campanella, Ÿ 1.3.2(6)
science, Ÿ 3.1.6(33), Ÿ 3.3.3(57), Ÿ 3.3.4(60),
Tommaso, Ÿ 3.1.3(29), Ÿ 4.2.3(118)
Ÿ 3.3.6(63), Ÿ 3.4.6(92), Ÿ 3.5.2(106),
Tuscany, Ÿ 1.3.4(15), Ÿ 1.4.1(17), Ÿ 4.2.2(116)
Ÿ 3.5.4(112)
Tycho, Ÿ 3.1.10(41)
sector, Ÿ (1), Ÿ 3.1.9(39), Ÿ 3.3.1(56),
Tycho Brahe, Ÿ 3.1.7(34), Ÿ 3.1.9(39),
Ÿ 3.3.4(60)
Ÿ 3.4.2(75), Ÿ 3.5.1(101)
sidereal, 85
sidereal period, Ÿ 3.4.4(84)
Simon, Ÿ 3.1.9(39)
Simon Marius, Ÿ 3.4.3(81), Ÿ 3.4.7(97)
Sister, Ÿ 2.3(24)
Sister Maria Celeste, Ÿ (1)
specic gravity, Ÿ 3.3.2(57), 57
sunspot, Ÿ 3.1.6(33), Ÿ 3.4.4(84)
sunspots, Ÿ 3.1.4(30), Ÿ 3.1.12(49),
Ÿ 3.1.14(53), Ÿ 3.4.1(71), Ÿ 3.4.2(75)
synod, Ÿ 1.3.4(15), 16
System, Ÿ 3.5.1(101)
T
telescope, Ÿ 3.1.1(27), Ÿ 3.1.9(39), Ÿ 3.3.5(61),
U universe, Ÿ 3.4.5(90)
Urban VIII, Ÿ 1.3.4(15), Ÿ 3.1.3(29)
V vicariats, Ÿ 1.3.4(15), 16
Vincenzo, Ÿ 2.1(21), Ÿ 3.1.11(46)
Vincenzo Galilei, Ÿ (1), Ÿ 1.3.2(6)
Vincenzo Gonzaga, Ÿ 1.3.1(6)
Vincenzo Viviani, Ÿ 3.3.3(57)
Viviani, Ÿ 3.1.11(46)
W Welser, Ÿ 3.1.5(31)
William, Ÿ 3.1.8(38)
William Gilbert, Ÿ 3.4.1(71)
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Attributions
Collection:
Galileo Project
Edited by: Albert Van Helden
URL: http://cnx.org/content/col10234/1.1/
License: http://creativecommons.org/licenses/by/1.0
Module: "The Biography of Galileo Galilei"
By: Albert Van Helden
URL: http://cnx.org/content/m11933/1.4/
Pages: 1-2
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Introduction to Galileo Galilei"
By: Albert Van Helden
URL: http://cnx.org/content/m11931/1.3/
Page: 3
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Collegio Romano"
By: Albert Van Helden
URL: http://cnx.org/content/m11939/1.3/
Pages: 3-4
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Accademia dei Lincei"
By: Albert Van Helden
URL: http://cnx.org/content/m11955/1.4/
Pages: 4-6
Copyright: Albert Van Helden
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Module: "Duke of Mantua, Vincenzo Gonzaga (1562-1612)"
By: Albert Van Helden
URL: http://cnx.org/content/m11937/1.3/
Page: 6
Copyright: Albert Van Helden
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Module: "The Medici Family"
By: Albert Van Helden
URL: http://cnx.org/content/m11975/1.2/
Pages: 6-13
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136
Module: "Paolo Sarpi"
By: Albert Van Helden
URL: http://cnx.org/content/m11967/1.2/
Pages: 13-15
Copyright: Albert Van Helden
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Module: "Urban VIII"
By: Albert Van Helden
URL: http://cnx.org/content/m11983/1.2/
Pages: 15-17
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Florence and Tuscany"
By: Albert Van Helden
URL: http://cnx.org/content/m11936/1.3/
Pages: 17-18
Copyright: Albert Van Helden
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Module: "Italy"
By: Albert Van Helden
URL: http://cnx.org/content/m11960/1.2/
Pages: 18-19
Copyright: Albert Van Helden
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Module: "Vincenzo Galileo"
By: Albert Van Helden
URL: http://cnx.org/content/m11934/1.3/
Page: 21
Copyright: Albert Van Helden
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Module: "Maria Celeste"
By: Albert Van Helden
URL: http://cnx.org/content/m11941/1.3/
Pages: 22-24
Copyright: Albert Van Helden
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Module: "Marina Gamba"
By: Albert Van Helden
URL: http://cnx.org/content/m11942/1.3/
Pages: 24-25
Copyright: Albert Van Helden
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Module: "Hans Lipperhey"
By: Albert Van Helden
URL: http://cnx.org/content/m11940/1.3/
Pages: 27-28
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137
Module: "Santorio Santorio"
By: Albert Van Helden
URL: http://cnx.org/content/m11969/1.2/
Pages: 28-29
Copyright: Albert Van Helden
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Module: "Tommaso Campanella"
By: Albert Van Helden
URL: http://cnx.org/content/m11982/1.2/
Pages: 29-30
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Johannes Fabricius"
By: Albert Van Helden
URL: http://cnx.org/content/m11961/1.3/
Pages: 30-31
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Marc Welser"
By: Albert Van Helden
URL: http://cnx.org/content/m11964/1.3/
Pages: 31-33
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Benedetto Castelli"
By: Albert Van Helden
URL: http://cnx.org/content/m11957/1.3/
Pages: 33-34
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Johannes Kepler"
By: Albert Van Helden
URL: http://cnx.org/content/m11962/1.2/
Pages: 34-38
Copyright: Albert Van Helden
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Module: "William Gilbert"
By: Albert Van Helden
URL: http://cnx.org/content/m11985/1.2/
Pages: 38-39
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Simon Marius"
By: Albert Van Helden
URL: http://cnx.org/content/m11973/1.2/
Pages: 39-41
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138
Module: "Tycho Brahe"
By: Albert Van Helden
URL: http://cnx.org/content/m11946/1.3/
Pages: 41-46
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Vincenzo Viviani"
By: Albert Van Helden
URL: http://cnx.org/content/m11984/1.2/
Pages: 46-49
Copyright: Albert Van Helden
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Module: "Thomas Harriot"
By: Albert Van Helden
URL: http://cnx.org/content/m11979/1.2/
Pages: 49-51
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Christopher Clavius"
By: Albert Van Helden
URL: http://cnx.org/content/m11958/1.2/
Pages: 51-53
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Christoph Scheiner"
By: Albert Van Helden
URL: http://cnx.org/content/m12126/1.1/
Pages: 53-55
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "The Pump"
By: Albert Van Helden
URL: http://cnx.org/content/m11976/1.2/
Pages: 56-57
Copyright: Albert Van Helden
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Module: "Hydrostatic Balance"
By: Albert Van Helden
URL: http://cnx.org/content/m12127/1.1/
Page: 57
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Galileo and the Pendulum"
By: Albert Van Helden
URL: http://cnx.org/content/m11929/1.3/
Pages: 57-60
Copyright: Albert Van Helden
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Module: "The Sector"
By: Albert Van Helden
URL: http://cnx.org/content/m11977/1.2/
Pages: 60-61
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "The Thermometer"
By: Albert Van Helden
URL: http://cnx.org/content/m11978/1.2/
Pages: 61-63
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Galileo's Telescope"
By: Albert Van Helden
URL: http://cnx.org/content/m11932/1.4/
Pages: 63-71
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "The Moon"
By: Albert Van Helden
URL: http://cnx.org/content/m11945/1.4/
Pages: 71-75
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Sunspots"
By: Albert Van Helden
URL: http://cnx.org/content/m11970/1.4/
Pages: 75-81
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Satellites of Jupiter"
By: Albert Van Helden
URL: http://cnx.org/content/m11971/1.2/
Pages: 81-84
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Saturn"
By: Albert Van Helden
URL: http://cnx.org/content/m11972/1.2/
Pages: 84-90
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Tides"
By: Albert Van Helden
URL: http://cnx.org/content/m11980/1.2/
Pages: 90-92
Copyright: Albert Van Helden
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140
Module: "Comets"
By: Albert Van Helden
URL: http://cnx.org/content/m11959/1.2/
Pages: 92-97
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Longitude at Sea"
By: Albert Van Helden
URL: http://cnx.org/content/m11963/1.2/
Pages: 97-100
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Copernican System"
By: Albert Van Helden
URL: http://cnx.org/content/m11938/1.3/
Pages: 101-106
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Ptolemaic System"
By: Albert Van Helden
URL: http://cnx.org/content/m11943/1.3/
Pages: 106-110
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Atomism"
By: Albert Van Helden
URL: http://cnx.org/content/m11956/1.4/
Pages: 110-112
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "On Motion"
By: Albert Van Helden
URL: http://cnx.org/content/m11965/1.2/
Page: 112
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "The Inquisition"
By: Albert Van Helden
URL: http://cnx.org/content/m11944/1.3/
Pages: 113-114
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "The Congregation of the Index"
By: Albert Van Helden
URL: http://cnx.org/content/m11974/1.2/
Pages: 114-115
Copyright: Albert Van Helden
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141
Module: "Giordano Bruno (1548-1600)"
By: Albert Van Helden
URL: http://cnx.org/content/m11935/1.3/
Pages: 115-116
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Robert Cardinal"
By: Albert Van Helden
URL: http://cnx.org/content/m11968/1.2/
Pages: 116-118
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Tommaso Caccini"
By: Albert Van Helden
URL: http://cnx.org/content/m11981/1.2/
Pages: 118-119
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
Module: "Paolo Antonio Foscarini"
By: Albert Van Helden
URL: http://cnx.org/content/m11966/1.2/
Page: 119
Copyright: Albert Van Helden
License: http://creativecommons.org/licenses/by/1.0
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Galileo Project
Biography of Galileo
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