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The History of Astronomy

Astronomy and the Ancient Greeks

The Astronomy of the ancient Greeks was linked to mathematics, and Greek astronomers sought to create geometrical models that could imitate the appearance of celestial motions# This tradition originated around the 6 ^th century BCE, with the followers of the mathematician Pythagoras #~580 – 500 BCE## Pythagoras believed that everything was related to mathematics and that through mathematics everything could be predicted and measured in rhythmic patterns or cycles# He placed astronomy as one of the four mathematical arts, the others being arithmetic, geometry and music#

While best known for the Pythagorean Theorem, Pythagoras did have some input into astronomy# By the time of Pythagoras, the five planets visible to the naked eye - Mercury, Venus, Mars, Jupiter and Saturn - had long been identified# The na#es of these planets were initially derived from Greek mythology before being given the equivalent Roman mythological na#es, which are the ones we still use today# The word ‘planet’ is a Greek term meaning ‘wanderer’, as these bodies move across the sky at different speeds from the stars, which appear fixed in the same positions relative to each other#

For part of the year Venus appears in the eastern sky as an early morning object before disappearing and reappearing a few weeks later in the evening western sky# Early Greek astronomers thought this was two different bodies and assigned the na#es ‘Phosphorus’ and ‘Hesperus’ to the morning and evening apparitions respectively# Pythagoras is given credit for being the first to realize that these two bodies were in fact the same planet, a notion he arrived at through observation and geometrical calculations#

Pythagoras was also one of the first to think that the Earth was round, a theory that was finally proved around 330 BCE by Aristotle# #Although, as you are probably aware, many people in 1642 CE still believed the earth to be flat##

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Questions

1. What was the na#e of the model of the universe with the earth at the center?
2. Who was the first to suggest a sun-centered solar system?
3. Why were epicycles necessary in Ptolemy’s model of the universe?
4. Tycho Brahe’s greatest contribution was
1. his theory that the solar system was heliocentric#
2. his invention of the telescope#
3. his accurate observations of stars and planets#
5. Astronomer Johannes Kepler
1. published ‘Almagest’.
2. suggested elliptical orbits for planets.
3. invented the first radio telescope.

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