Galileo: the man and the scientist

Galileo: the man and the scientist
Alberto Righini
Formerly professor at the
Department of Physics and Astronomy
University of Florence, Italy
[email protected]
Galileo’s human and scientific vicissitudes strongly reflect that complex historical period
between the end of the XVI century and the beginning of XVII in which many paradigms and habits
were evolving very rapidly, in science, in the social life, in politics. In Tuscany, and in central Italy,
in the years preceding the birth of Galileo, the Italian Protestantism, which had won over many
consciences, was very strong, and people was experiencing a new freedom in their spiritual and
intellectual endeavors. Few years after Galileo’s birth, in 1567, the ruler of Florence, Cosimo I
Medici, decided to suppress the Protestant heresy (obtaining in exchange from the Pope the title of
Grand Duke); consequently in Florence and in Pisa suddenly the cultural environment, which was
relatively free, became close and dominated by the Roman Inquisition. However Galileo received
an education where intellectual freedom connected with the early Protestantism was promoted,
perhaps through the teaching of some professors at Pisa University and of his father, a great scholar
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Comment [1]:
Alberto Righini 24/09/09 18:04
Dia 10 Cosimo I
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Comment [2]:
Alberto Righini 24/09/09 18:05
Dia 11 Lutero e Valdes
of music and a composer, who developed a revolutionary approach to the study of music.
The seventeen years old Galileo was enrolled in the medical school at Pisa University. He
was a very critical student unable to refrain from expressing his strong doubts about the obsolete
teaching based on the Aristotle’s Physics, most probably he skipped several lectures, preferring to
spend his time in one of the many wine bars in town, but perhaps he did not skip the sessions of
anatomy where the dissections were showing how wrong were the traditional idea on the structure
of the human body, and those of Francesco Buonamici who was teaching that the empiricism
formed the basis of Aristotelian Natural Philosophy (Physics). This fact, had been purposely
omitted in the teaching of Aristotle, since it obviously leads to a continuous challenge of the
established paradigms by those who take the trouble to interpret new experimental evidences or to
reinterpret the existing ones.
Galileo never took his master of arts in Pisa, however in 1589, at the age of twenty-five, he
was appointed Professor of mathematics in that university, thanks to his private studies in
mathematics and geometry under the guide of Ostilio Ricci and the recommendation of the
mathematician Guidobaldo del Monte, his father’s good friend. Galileo spent three years in Pisa but
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Comment [3]:
Alberto Righini 24/09/09 18:12
The bean eater 19
he was not at ease since in that university the culture was dominated by the theologists, however
those years were fundamental for the formation of the young Galileo on the physics of motion,
discussing and arguing with colleagues, at least with those who accepted the scientific debate.
In 1592 Galileo moves to Padua university which was a thriving economic resource for the
city and the Venetian Republic itself, both through student tuition fees and ancillary expenses. In
Padua and Venice the freedom to teach was generally guaranteed, even though occasionally some
heretic condemned by the Holy Inquisition would be executed by drowning at dawn in the Venice
lagoon, or arrested and sent to Rome, as happened to Giordano Bruno. Soon the reputation of the
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Comment [4]:
Alberto Righini 24/09/09 18:19
Canal Grande
new Tuscan Professor spread amongst the students and many rushed to hear his lectures. Galileo
spent in Padua about seventeen years. His scientific production was not at all remarkable. He
exchanged letters with Kepler declaring his Copernican faith but his teaching was strictly
In 1609 the news reached Venice that a certain Flemish optician had built a special spyglass
through which it was possible to see distant objects closer with a magnification of about 4 times.
Galileo (or some friends of him) was able just on empirical basis to quickly push the magnification
first to 10 times and than to 20 times and even to 30 times but never really understanding how the
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Alberto Righini 24/09/09 18:22
Dia 26 Occhiali: manca nel testo qualche cosa
telescope works. After having sold the instrument to the political and military establishment, he
aimed it at the sky. In quick succession he discovered that the clouds of the Milky Way were large
clusters of stars, the Moon had valleys and mountains like the Earth, Jupiter had four satellites
(Moons), Venus had phases like the Moon, Saturn had some sort of “ears” and finally sunspots and
solar rotation (summer 1610 ?). The first results about the Moon, the multitude of stars in clouds
and Jupiter satellites, were published in the space of a few months in a booklet entitled Sidereus
Nuncius (A sidereal message). For his concise and direct Latin prose, and the full use of the
graphics, this book can be considered much closer to the modern scientific reports than to the
astronomical literature of those times.
Back in Florence as mathematician and first philosopher of the Gran Duke he was a wealthy
civil servant, often invited at court, and participating in erudite discussions. On March 1613 The
“Accademia dei Lincei” in Rome published his “Historia e dimostrazioni sulle macchie solari”
(History and demonstrations about sunspots) which was the result of a team work between Galileo,
a former pupil of him, Benedetto Castelli, the prince Federico Cesi, founder of the Lincei Academy,
and the painter Lodovico Cardi born in the Tuscan village named Cigoli. This booklet may be
considered the first scientific (in the modern meaning of the word) demonstration of solar rotation
ascertained on the basis of several observations of the sunspots carried out with the innovative
system devised by Benedetto Castelli. In the conclusions, to explain solar faculae and sunspots,
Galileo sketches the idea of stellar accretion due to in-falling matter. The “Historia e
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Comment [6]:
Alberto Righini 24/09/09 18:23
Immagini della Luna
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Comment [7]:
Alberto Righini 24/09/09 18:23
Immmagini dei satelliti dalla lettera
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Comment [8]:
Alberto Righini 24/09/09 18:24
Immagini di Venere
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Alberto Righini 24/09/09 18:23
Immagine di SaturnoFasi di Venere
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Alberto Righini 24/09/09 18:24
Macchie solari
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Alberto Righini 24/09/09 18:26
Frontespizio del Nuncius con mani che lo
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Alberto Righini 24/09/09 18:26
Telescopi di Galileo e lente obbiettiva
dimostrazioni....” is based on three letters written by Galileo to the German banker Marcus Welser
who had asked his opinion on a opusculum published in Augsburg by the Jesuit Chistopher
Scheiner on sunspots claiming that they did not belong to solar surface but were small planets
revolving around the Sun on orbits inner than that of Mercury.
It should be remembered that the hypothesis of a rotating Sun as the first cause of the
revolution of the planets of the Solar System in a Copernican cosmology had already formulated,
without any observational proof, by Kepler in his “Misterium Cosmographycum“ published in
Tubingen in 1596 and received by Galileo in 1597 in Padua.
In Florence Galileo, known as a fervent Copernican, soon entered into harsh conflicts with
some religious circles, specifically the Dominicans, who proclaimed the heresy of the heliocentric
theory, since it contradicted the Holy Writ. Despite all Galileo’s efforts, in February of 1616 Pope
Camillo Borghese (Paul V) summoned Galileo to stop spreading and to defend in writings
Copernican ideas, because the hypothesis of the motion of the Earth was considered heretical.
It might be that Galileo did not understand the importance of the admonition, all his work up
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Alberto Righini 24/09/09 18:31
Camillo Borghese Paolo V dia34
to 1632 was focussed on demonstrating through physical experiment that the motion of the Earth
around the Sun was physically possible: in this cultural path he first published “il Saggiatore” (The
Assayer) in which he developed the experimental method and finally the “Dialogo intorno ai due
massimi sistemi del mondo” (Dialogue on the two chief world systems). In 1633, following the
order of Pope Urban VIII (Maffeo Barberini a former admirer of Galileo), the Holy Inquisition sent
the book to the stake, forced Galileo to abjure his Copernican belief and sentenced him to be
imprisoned for life having violated the admonition of February 1616, but soon the sentence was
transformed to house arrest in Villa Medici, the magnificent Medici Palace in Rome, and then in
Siena and finally in his country house, called il Gioiello, in Arcetri, close to Florence.
The sentence was formally the result of a clash between Faith in the Holy Writ and the new
Science, but substantially it should be mainly interpreted considering the political impasse of the
Holy Siege in the frame of the Thirty Years war which at those time was devastating central
Galileo, in his house on the beautiful hill of Arcetri, thirty minutes of mule ride from the
center of Florence, spent his remaining years surrounded by friends and disciples, as Vincenzio
Viviani and Evangelista Torricelli, and wrote another great treatise entitled “Discorso intorno a due
nuove Scienze” (Discourse about two new sciences), which deals with cinematic and static. This
book is just as fundamental for affirming the Copernican theory as the Dialogue, but the
theologians were so ignorant that they did not realize the revolutionary impetus of his last work.
Galileo died in 1642 at the age of 78, blind, while under house arrest, by order of the Pope
his corpse was secretly buried in the wall of a room close to the Florentine church of Santa Croce.
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Alberto Righini 24/09/09 18:38
Santa Croce
Near a century elapsed before his remains were transferred in the monumental sepulcher built on
the left wall of the church by the heirs of Vincenzio Viviani.