Greek AstronomyBy: Kaitlyn McCourt, Gina Paisley,

and Carly Weber

Before the Greeks● Know little about Greek astronomy prior to the 4th

century● Aristotle made comments and observations about what

he thought the universe was like● Minimal supernatural explanations for occurrences● Egyptians and Babylonians had highly developed

thoughts on astronomyo Egyptians used calendars to predict the flood of the

Nileo Babylonians relied on reading omens in the sky

Pythagoras

Pythagoras is credited as the first Greek to believe the Earth is a sphere.

● thought this on mystic rational not scientifico the Earth’s shadow on the moon indicated its

spherical shape

Geocentric ModelBelieved Earth was at the center of the universe. Two observations: 1. When they looked up in the sky they saw the stars, sun,

moon, and other planets revolving around the Earth.2. Earth appeared to not be moving from the observer on

Earth.

Early Greek thinking

● More concerned with what is happening● Less concerned with why it is happening● Only explanation given for early

discoveries was that it was part of the God’s doings

Expanding their thinking

● Began to theorize about other parts of universe other than Gods and theology

● Believed that the universe was a machine o Ran upon mechanical as well as

mathematical principleso Could be concluded by logic and reasoning

Scientific Discovery

● Greeks began interested in studying the “heavens”

● Timekeepingo Length of a dayo Length of a year

Scientific Discovery

● Mainly for agricultural purposeso When should they plant their crops?

● Other factors that sparked their interest…o Religion, navigation, curiosity

How they did it

● Noted rising and setting of constellationso Early Greek farmers

● Water clockso Introduced by Platoo Water-based alarm clocko Measured time in hourso Regulate flow of liquid into container

How did Greek Astronomy impact society?

Many Greek astronomers made important contributions to our society such as Ptolemy, Thales, Hipparchus, and Aristarchus.

Ptolemy

Ptolemy made many discoveries involving the earth and planets.He is very well known for finding out the Earth was spherical rather than flat.He also proposed the theory of epicycles.

Thales

Thales founded trigonometry, which is a crucial part of mathematics today which deals with measuring the angles of triangles.

Hipparchus

Hipparchus was one of the first astronomers who kept long term notes of his observations. This helped him discover the exact length of a year and that seasons are not all equal in length.He was also the first person to make a catalog of stars which helped many other astronomers in the future.

Aristarchus

Aristarchus was the first Greek astronomer that proposed the heliocentric theory

(Earth orbits around the sun)

The Calendar!Many Greek astronomers drafted different calendar ideas.Perhaps one of the most influential people was Sosigenes, who was an astronomer and a mathematician. He gave advice to Julius Caesar, which led to the creation of a calendar. This was in place until the Gregorian calendar took over in 1578.

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