Historical Contributions of Early Astronomers

Earth is the center.

"Geo" = earth

"centric" = center​

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​Geocentric

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​Aristotle was a Greek astronomer who believed earth was the center of the entire universe. He saw the sun, the stars, and the planets move across the heavens. He hypothesized this meant earth was at the center.

​​Aristotle

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​Ptolemy was an Egyptian astronomer who believed in the earth - centered model. He believed the earth was round and didn't move at all.

​​Ptolemy

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Sun is the center

"helio" = sun​

"centric" = center​

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​Heliocentric

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​Copernicus was a Polish astronomer who challenged the geocentric model. He hypothesized the sun was the center of the solar system and that the planets revolved around it.

​​Copernicus

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​Galileo made improvements to his telescope and changed his idea of the universe. He was able to study the heavens and see evidence that the heliocentric model was correct.

​​Galileo

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