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When was Mars 686 , Venus 224 and Mercury 87 days sidereal period was discovered , was it discovered by the ancients or after Copernicus

user18229
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    Have you done any research? –  Aug 25 '17 at 18:34
  • Yes, Jan I have ... but unfortunately I can't find the answer ! – user18229 Aug 26 '17 at 21:23
  • Did you find the Wikipedia entry History of Mars observation? Maybe from there you'll get further. Similar sections on the other planets may also exists; I did not check. –  Aug 27 '17 at 07:58
  • As https://en.wikipedia.org/wiki/Aristarchus_of_Samos notes, Aristarchus had created a heliocentric model, though the original work has been lost. Presumably, part of this model would be providing the sidereal period of the planets. –  Aug 27 '17 at 15:27
  • I like to thank both Jan Doggen and Barry Carter for their help. I have finally found the answer in the following link https://en.wikipedia.org/wiki/Surya_Siddhanta. – user18229 Aug 28 '17 at 09:09
  • User 18229 - Your references show only the values, and there are no hints about how they were computed. I am most interested in Ptolemy's calculations – bandi Oct 05 '22 at 06:42
  • While the Surya Siddhanta does mention sidereal periods for the planets, Babylonian astronomers had figured those out approximately one millennia beforehand, as mentioned in the [History of Mars observation][1] Wikipedia page. There, one may read:

    For Mars, they knew, for example, that the planet made 37 synodic periods, or 42 circuits of the zodiac, every 79 years.

    If you take 79 years, that’s about 28,855 days, and divide it by 42 circuits, you get 687 days per circuit, which is the sidereal period of Mars. [1]: https://en.wikipedia.org/wiki/History_of_Mars_observation

     – Pierre Paquette Feb 06 '24 at 02:42

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