Aryabhatta studied at the University of Nalanda. One of his major works was Aryabhatiya written in 499 AD. His book aryabhatiya covers astronomical and mathematical theories in which the earth was taken to be spinning on its axis and the periods of the planets were given with respect to the sun. Aryabhatta believes that the moon and planets shine by reflected sunlight and he also believes that the orbits of the planets are ellipses. He correctly explains the causes of eclipses of the Sun and the Moon. His value for the length of the year at 365 days 6 hours 12 minutes 30 seconds is remarkably close to the true value which is about 365 days 6 hours. In this book, the day was reckoned from one sunrise to the next, whereas in his Aryabhata-siddhanta he took the day from one midnight to another. There was also difference in some astronomical parameters.
Aryabhatta was the first to explain how the Lunar Eclipse and the Solar Eclipse happened. Aryabhatta also gave close approximation for Pi. In the Aryabhatiya, he wrote-“Add 4 to 100, multiply by 8, then add 62000 and then divided by 20000. The result is approximately the circumference of a circle of diameter twenty thousand. By this rule the relation of the circumference to diameter is given.” In other words, p ~ 62832/20000= 3.1416, correct to four rounded – off decimal places. Aryabhatta was the first astronomers to make an attempt at measuring the earth’s circumference. Aryabhata accurately calculated the earth’s circumference as 24835 miles, which was only 0.2 % smaller than the actual value of 24,902