Surya Siddhanta

The Surya Siddhanta is a treatise of Indian astronomy.Later Indian mathematicians and astronomers such as Aryabhata and Varahamihira made references to this text. Varahamihira in his Panchasiddhantika contrasts it with four other treatises, besides the Paitamaha Siddhantas (which is more similar to the "classical" Vedanga Jyotisha), the Paulisha and  Romaka Siddhantas (directly based on Hellenistic astronomy) and the  Vasishta Siddhanta.
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Surya-Siddhanta (Sanskrit) A celebrated astronomical and cosmogonical work of ancient India of enormous antiquity. This work shows marvelous mathematical skill and comes very close to the modern time periods of astronomy that the most skilled mathematicians and astronomers have determined. It also deals with yugas in their various lengths, divisions of time itself into infinitesimal quantities, and general astronomical subjects, including not only the time periods of the sun, moon, and planets, but also eclipses, seasons of the year, etc.
The Surya-Siddhanta states that it was dictated more than two million years ago, towards the end of the krita yuga (golden age) by the sun himself, through a projected solar representative, to the great sage Asuramaya who wrote down the revelation. From the commencement of our kali yuga to the end of the satya yuga is 2,164,965 years ago. The Surya-Siddanta was therefore a very late Atlantean work or an early work of the fifth root-race, for though the so-called Aryan or fifth root-race was already nearly 1,728,000 years old at the time of the writing of this work, the race was still in its early periods, and was still practically a part of the Atlantean civilization; hence Asuramaya has been called an Atlantean astronomer. The fifth root-race has been a race sui generis for only about a million years from our present time.