Name:
There are some very influential people who have set up our understanding of
astronomy over more recent years.
Claudius Ptolemy
Claudius Ptolemy lived from 85 – 165AD. He made
his observations from Egypt between 127-141AD.
Ptolemy believed from his observations, that the
Earth was the centre of the universe and that
everything – the Sun, Moon, stars and planets
revolved or orbited around it. Ptolemy’s model was
call geocentrism (geo means Earth – Earth at the
centre)
Though we may think this idea is ridiculous now,
Ptolemy’s ideas were revolutionary for their time and
these beliefs held for 1400 years before Copernicus
came up with another theory.
Nicolaus Copernicus
Nicolaus Copernicus lived from 1473 to 1543. In
1514, Nicolaus Copernicus suggested that the
Earth was not at the centre of the Universe, but
that all of the planets revolved around the Sun!
This idea is called heliocentrism (helios means Sun
– Sun at the centre).
Copernicus made the following assumptions
about his astronomical observations:
•
Bodies in space do not all revolve around a particular point.
•
Earth is not the centre of the universe; only the Moon revolves around the Earth.
•
All the planets revolve around the Sun. (He thought the Sun was near the centre of the universe.)
•
The stars do not move – their movement is actually the rotation of the Earth.
•
The Sun doesn’t move across our skies, instead, what we see is a result of the Earth moving around the Sun.
Copernicus’s beliefs were not well received by those of his day! However, many of his
ideas are in fact correct, as we now know it.
© e-classroom 2014 www.e-classroom.co.za
GRADE 7
Grade 7 Natural Science: Planet Earth and Beyond: Historical Development of Astronomy: Modern Developments
Historical development of astronomy
Galileo Galilei lived from 1564 to 1642. Galileo’s
greatest contribution was that his theories were built
on observation of space. In 1610, he observed four
bodies that moved around Jupiter in a way that was
different to stars. These were later to be discovered as
four of Jupiter’s moons.
Galileo’s believed in Copernicus’s heliocentric model and his work helped to build
onto this theory. Galileo’s support of this model was not approved by many and he
even spent the final years of his life under house arrest!
Johannes Kepler
Johannes Kepler lived from 1571 to 1630. He
brought a more scientific approach to astronomy,
in a world where the difference between astronomy
and astrology was not so clearly distinguished.
Galileo and Kepler achieved most of their work at
the same time and though they often disagreed on
many points, together they built on the theories
we now use. Kepler believed that the Moon was
responsible for changes in the tides, but Galileo
believed the tides were caused by the rotation of
the Earth. It shows that even the smartest people of history can make mistakes.
DEFINITIONS
Astronomy - a science that studies the object outside of the Earth’s
atmosphere (planets, stars, asteroids, galaxies) and the relationships
between these objects.
Astrology - the belie f that the positioning of the stars and planets
relate to and affect events that occur in the human world.
Isaac Newton
Isaac Newton lived from 1642 to 1726. His major contribution
to astronomy was in his development of the Law of Universal
Gravitation, which described how two bodies, such as the
Earth and the Moon, can be drawn to each other by gravity. It
also described how all of the objects on the Earth’s surface are
drawn toward its centre, in the same way all over it surface.
© e-classroom 2014 www.e-classroom.co.za
GRADE 7
Grade 7 Natural Science: Planet Earth and Beyond: Historical Development of Astronomy: Modern Developments
Galileo Galilei
Do you remember learning about the telescope in
Grade 6? If you do, you might remember that Galileo
Galilei was the first man to point a telescope to the sky
and observe the bodies in space with it.