In geocentric models, did the Earth rotate?

  • In geocentric models, did the Earth rotate around its axis?



    I assume that if the Earth rotated around its axis, then the Sun would not have to orbit around the Earth at a very fast rate, whereas if the Earth didn't rotate, then the Sun would have to orbit the Earth every day.


    Since the earth is flat, you would fall off if it rotates.

    You got it right! Earth was considered still.

    @LDC3 No one ever thought that Earth is flat. That is a myth. Every sailor can see with his bare eyes that the Earth is round, and everyone sees it when the round shadow of earth eclipses the Moon. Flat Earth was a myth invented by lying propagandists during the Darwin debate in the later half of the 1800th century.

    @LocalFluff Your information is wrong, it goes back before Ancient Greece. Your `myth` pertains to the belief during the middle ages, not before. `Many ancient cultures have had conceptions of a flat Earth, including Greece until the classical period ... most Pre-Socratics retained the flat Earth model.` The flat earth belief started to be replaced after 330BC. From http://en.wikipedia.org/wiki/Flat_Earth

    Right the sun has to move across the sky very quickly. That is why he has a chariot drawn by horses.

  • fdb

    fdb Correct answer

    8 years ago

    In the historic geocentric models, and in particular in the Ptolemaic model, the earth is immobile in the centre of the cosmos, and the sphere of the fixed stars rotates around it once a day, carrying the sun, moon and planets with it. There were astronomers who realised that this apparent motion could also be explained, from a purely mathematical point of view, by assuming that the earth rotates on its axis, but they rejected this option. By the way, neither Ptolemy nor any other serious astronomer believed that the earth was flat.


    From what I read, Ptolemy was aware of Aristarchus of Samos's Earth orbits the Sun model, but he felt that an Earth rotating at close to 1,000 mph at Mediterranean latitude was unworkable as they'd surely feel it. He had a footnote that this was a model and the precise answer wasn't known, but he was in favor of Aristotle's model. People later took his model as gospel though, but he never felt 100% certain.

    @userLTK. Could you give us a reference for this (page or chapter number in the Almagest)? And what do you mean by "footnote"? (Greek books never have footnotes).

    It's from memory. Will take some looking, but I'll see if I can find.

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