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

CC BY-SA 3.0
2017-08-26T21:23:32.997Z
Yes, Jan I have ... but unfortunately I can't find the answer !
user18229
CC BY-SA 3.0
2017-08-28T09:09:00.237Z
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
CC BY-SA 4.0
2022-10-05T06:42:44.413Z
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
CC BY-SA 4.0
2024-02-06T02:42:23.460Z
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
<venus>
Planets sidereal periods
user18229
# Planets sidereal periods

(Asked by: username_0 on 2017-08-25)

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

**Tags:** venus

> **Comments:**
> **username_0**: Yes, Jan I have ... but unfortunately I can't find the answer !  
> **username_0**: 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.  
> **username_1**: 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  
> **username_2**: 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  

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