Varahamihira’s main work is the book Pancha Siddhantika (Treatise on the five Astronomical Canons gives us information about older Indian texts which are now lost). The work it seems is a treatise on mathematical astronomy and it summarises five earlier astronomical treatises, namely, the Surya Siddhanta, Romaka Siddhanta, Paulisa Siddhanta, Vasishtha Siddhanta, and Paitama Siddhanta.

It is acclaimed that Pancha Siddhantika of Varahamihira is one of the most important sources for the history of Hindu Astronomy from before the time of Aryabhata.

Another important contribution of Varahamihira is the encyclopedic Brihat-Samhita. It covers wide-ranging subjects of human interest, including astrology, planetary movements, eclipses, rainfall, rainfall, clouds even domestic relations, gems, pearls, and rituals.

Varahamihira in 550 AD has described a large number of comets in the Brhat Samhita. He wrote over sixty couplets about comets. He did not have the modern facilities like Telescope or other electronic equipment. He says that sages Garga, Parasara, Asita, Devala and others had already written about the comets.

He was also an astrologer and has written on all the three branches of astrology. His son Prithuyasas has also contributed in the Hindu astrology through his work, Hora Sara.

Varahamihira’s mathematical work included the discovery of the trigonometric formulas. He improved the accuracy of the sine tables of Aryabhata l. He defined the algebraic properties of zero as well as of negative numbers. Furthermore, He was among the first mathematicians to discover a version of what is now known as the Pascal’s triangle. He used it to calculate the binomial coefficients.

Varahamihira made some significant observations in the field of ecology, hydrology and geology too. He was the first person who predicted underground water. His claim that plants and termites serve as indicators of underground water is now receiving attention in the scientific world.

Varahamihira, without any scientific equipment, derived the true value of equinox. This value is very important for the modern-day Geostationary Satellites.

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**Surya Siddhanta & description on planet Mars:**

- Pancha siddhantika includes Surya Siddhanta, an astronomical treatise which explains or determines the true motions of the luminaries. Under this work, Varahamihira has also explained the estimated diameters of the planets, like Mercury, Venus, Mars, Saturn and Jupiter.
- The book gave the locations of several stars other than the lunar nakshatras (constellations) and the calculation of solar eclipses. The book also had a significant coverage on kinds of time, the length of the year of gods and demons, day and night of god Brahma, the elapsed period since creation, how planets move eastwards and sidereal revolution.
- Surya Siddhanta mentioned the Mars’s diameter (which was calculated to be 3,772 miles that has an error within 11% of the currently accepted diameter of 4,218 miles), circumference and also carries calculations on and about solar eclipses and lunar eclipses, its color and portion of the moon as well.
- Apart from these, Varahamihira also predicted the presence of water on Mars. The book had a detailed description of planet Mars. He had said in his book that planet Mars has both water and iron present on its surface, which have now been revealed by NASA and ISRO.
- He was the first to mention and explain how each planet in the solar system has been created by and centered on the sun.