Question
How did the sun, moon and stars move and at what speed in the geocentric model? What flaw was observed?
Answers
Answered by
GPT 3.5
In the geocentric model, it was believed that the sun, moon, and stars revolved around the Earth. They were considered to be fixed on celestial spheres or crystalline spheres. The movement of these celestial bodies in the geocentric model was thought to be a combination of two motions: the daily rotation around the Earth and the yearly revolution along the ecliptic.
The sun was believed to move eastward during the day and then go below the Earth at night, only to rise again in the morning from the east. This was attributed to the sun's daily rotation around the Earth.
Similarly, the moon was observed to rise in the east and set in the west, following a similar pattern as the sun but with a slightly different trajectory. The moon's motion was also explained as its rotation around the Earth.
The stars were observed to appear to have fixed positions in the sky, moving around the North Star (Polaris in the Northern Hemisphere). These observations were explained by attributing the stars to be fixed on a celestial sphere rotating around the Earth once a day.
The flaw observed in the geocentric model was the retrograde motion of some planets, especially Mars and Jupiter. Retrograde motion refers to the temporary westward movement of planets against their normal eastward motion in the sky. This observation was challenging to explain in the geocentric model because it contradicted the assumption that all celestial bodies circled the Earth. It was particularly challenging to account for these irregular retrograde motions using purely circular motions. This inconsistency laid the foundation for the development of the heliocentric model.
The sun was believed to move eastward during the day and then go below the Earth at night, only to rise again in the morning from the east. This was attributed to the sun's daily rotation around the Earth.
Similarly, the moon was observed to rise in the east and set in the west, following a similar pattern as the sun but with a slightly different trajectory. The moon's motion was also explained as its rotation around the Earth.
The stars were observed to appear to have fixed positions in the sky, moving around the North Star (Polaris in the Northern Hemisphere). These observations were explained by attributing the stars to be fixed on a celestial sphere rotating around the Earth once a day.
The flaw observed in the geocentric model was the retrograde motion of some planets, especially Mars and Jupiter. Retrograde motion refers to the temporary westward movement of planets against their normal eastward motion in the sky. This observation was challenging to explain in the geocentric model because it contradicted the assumption that all celestial bodies circled the Earth. It was particularly challenging to account for these irregular retrograde motions using purely circular motions. This inconsistency laid the foundation for the development of the heliocentric model.
There are no human answers yet. A form for humans to post answers is coming very soon!