Achievements of Ancient Indians in Astronomy
In order to comprehend the mysteries of universe astronomy developed as a subject in ancient India. In order to carry out religious and ritualistic obligations, proper understanding of heavenly bodies and their precise location, position, time of appearance etc. became necessary. Practical considerations like need for accurate prediction of monsoon rainfall and growing demand for astrological charts especially by king(s), nobles and mercantile classes provided astronomers with patrons. The subject was closely associated with mathematics and many a time it was difficult to distinguish it as an exclusive subject. It was accorded highest place of honor.
The contribution to the subject is well known and is moreover documented. Astronomical principles were many times used by astrologers in preparing horoscope, calendar etc. During vedic times Joytisha was recognized as one of the branches of studies (Vendanga). In about 40 verses of Rig Veda rules are given for making almanac (pancanga) for a cycle of 5 years of 1830 days. It included both astronomy as well as astrology with sufficient idea about planetary movement, solar and lunar eclipse etc.
The earliest concept of a heliocentric model of the solar system is found in vedic texts, for example, “The Sun never sets nor rises” has been stated in Aitareya Brahamana. Visnu Purana clearly states “The sun is stationed for all time …”.
The ancient and oldest text on astronomy appears to be Surya Siddhhanta. All the astronomers in ancient India held surya Siddhanta in high esteem and considered their individual work as commentaries to the same. It can even now enable prediction of eclipses with slight error. Aryabhatta-I remodelled astronomy on scientific basic. He made pioneering discoveries in the realm of planetary motion. In his magnum opus Aryabhattiya, he propounded a mathematic heliocentric model and popularised the theory that earth rotates on its own axis. He further stated that earth was spherical in shape and it followed an elliptical path around the stationary sun. Varahamihira (6th century AD) wrote Panca Siddhantika which gives the summary of five astronomical books of his time. In his treatise Brihat Samhita forwarded encyclopedic range of knowledge about several branches of science. However his work is considered as authoritative source for astrology.
Bhaskara-II in Siddhanta Siromani went a step further to mention law of gravity. InIact Goladhayay (sphere) and Grahaganita (mathematics of the planets) which are two important parts of his treatise are directly associated with astronomy. His other important work Karallakutuhala is a manual of astronomical calculation that is still in use in many parts of India for making calendar. Other astronomers of eminence include Madhava, Nelakantha etc.
In India people had started the use of the astronomical instruments before 1000 BC. During this period one of the prominent books ‘Suryasidhanta’ was written for astronomical calculations. There are several works with the same name, BUT the Original writer of Surya Siddhanta is unknown.
The title ‘Suryasidhanta’ means sun theory and it highlights the calculations of positions of stars and planets. Some of the Indian mathematicians later have developed their own instruments and developed their own methods to facilitate the theory of ‘Suryasidhanta’. Introduction of zero in mathematics and the decimal method of calculation is one of such invaluable contribution. We should note that Varahamihira had contrasted Surya Siddhanta along with his 4 other treatises in the panchsiddhantika viz. Paitamaha Siddhantas, Paulisha , Romaka Siddhantas and Vasishta Siddhanta. Citation of the Surya Siddhanta is also found in the works of Aryabhata.