• Eshaan Mandal

Surya Siddhanta: The Oldest Book on Astronomy


When we talk about the earliest works on astronomy, it usually goes like - ‘The Greeks were the first to systematically record and study astronomy, they developed the geocentric model ( although wrong), did this, did that, and the list goes on’, but somewhere amidst the chaos, an equally thought-provoking work, which deals with the motion of planets, the length of the year, trigonometric identities, the theory of gravitation, and also the usage of decimals and standard notation, failed to grab the attention it deserves. Not only does it tell us about the vast understanding of ancient Indians on the subject of astronomy but also shows that when the world was struggling with hundreds, we did millions. (you know what I mean, calculations), and is known as सूर्यसिद्धांत ( The Treatise on Sun).


The Lore Behind the Book


It is said that the book is the collection of all the knowledge given to an Asura called Maya by the Sun God, in Treta Yuga in order to worship the Sun God better.

This Maya is the father-in-law of Ravana (The King of Lanka in the famous Indian epic Ramayana). Going by calculations of Yugas, the first version of Surya Siddhanta must have been known around 2 million years ago. The current version we have today was modified in the year 5th century AD, by an Indian polymath Varahmira, and a bit altered in 10th century AD by Bhaskaracharya. Before that, the book was passed down orally in the form of verses (shlokas) from one generation to the next, and the original version dates back to 7300-7800 BCE. Surya Siddhanta was also mentioned in the works of Aryabhatta.



What's Inside?


Let us talk about the content of the book, and what makes it special or perhaps advanced for its time. The book is divided into fourteen chapters. And the table of contents is as follows.

  • The Mean Motion of the Planets

  • True Places of the Planets

  • Direction Place and Time

  • The Moon and Eclipses

  • The Sun and Eclipses

  • The Projection of Eclipses

  • Planetary Conjunctions

  • Of the Stars

  • Risings and Settings

  • The Moon’s Risings and Settings

  • Certain Malignant Aspects of the Sun and Moon

  • Cosmogony, Geography, and Dimensions of the Creation

  • The Gnomon.

  • The Movement of the Heavens and Human Activity. (Spirituality)

Many things discovered later in science were known to ancient India, and those things are profoundly discussed here.



Some excerpts from the book


The author(s) of Surya Siddhanta was pretty accurate when it comes to calculations, and their accuracy is worth mentioning.

  • The average length of the tropical year, calculated to be equal to 365.242175 days, which is only a few seconds shorter than the modern value of 365.242190 days!

  • The average length of the actual length of the Earth’s revolution around the Sun, calculated to be equal to 365.25636 days, which is a carbon copy of the modern value of 365.256363 days.

  • Aside from inventing the decimal system, zero, and standard notation, the Surya Siddhanta also contains the roots of Trigonometry.

  • It uses jya, kojya and otkram jya , sine, cosine, inverse sine for the first time!

  • Objects fall on earth due to an attractive force. therefore, the celestial bodies are held in orbit due to this attraction”. I guess it is the famed law of gravitation by Sir Isaac Newton, mentioned in Surya Siddhanta.

  • The Surya Siddhanta also goes into a detailed discussion about time cycles and that time flows differently in different circumstances, the roots of relativity.

  • The diameter of Mercury, estimated at about 3,008 miles, with an error of less than 1% from the current value.

  • The diameter of Mars estimated at 3,772 miles, which has an error within 11% of the currently accepted value.

There are many more examples but, I think these are enough to prove my point.


Ending Note


It would be interesting to mention here about ancient Indian philosophy.

The Indian philosophy’s belief that science and religion are not mutually exclusive. Unlike, Abrahamic religions, one does not have to try all ways to force scientific truth from scriptures, but quite the opposite, it is stated in cold hard numbers by the Sun God, Surya. And this makes Surya Siddhanta one of the most advanced books on astronomy in ancient times.



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