Aryabhata and Indian astronomy
Aryabhata was an Indian astronomer and mathematician whose work in the Aryabhatiya, dated to 499 CE, shaped later Indian astronomy and the calculations used in Jyotish.
What it is
The Aryabhatiya gives a model of planetary motion, a value for pi, a method for the sine function, and an explanation of eclipses. Its planetary model influenced later siddhantas and almanacs.
How it is worked out or read
Later Jyotish calculations drew on the same tradition, but the site's positions come from modern ephemeris models, not from Aryabhata's parameters. The difference is part of the method.
Where it appears on this site
The method is on the method page, and the Surya Siddhanta article covers another early work.
Aryabhata's place in the story
Aryabhata was an Indian astronomer and mathematician whose main work, the Aryabhatiya, is dated by its own colophon to 499 CE. The work is written in very compact verse, and it gives a model of planetary motion, a rule for the value of pi, a method for computing sines and an explanation of eclipses. Its influence on later Indian astronomy, including on the calendar, was considerable.
Aryabhata's model of the Earth's rotation, which he discussed in the text, is one of the notable features of his work, and it shows how the astronomers of his time thought about the apparent motion of the sky.
What later readers took from him
Later astronomers and commentators took up Aryabhata's methods and developed them further. The tables and rules in the Aryabhatiya became standard reference points for many subsequent calendars, and the mathematical methods shaped later work in India and beyond. A reader of the history of Jyotish will find his name in the background of many of the calculations used today.
The Aryabhatiya in outline
The Aryabhatiya is a short work of 121 verses in four sections. The Gitikapada gives the basic astronomical constants in a compact numerical code. The Ganitapada covers mathematics: arithmetic, geometry, the value of pi, which it gives as about 3.1416, and methods for solving certain equations. The Kalakriyapada deals with the reckoning of time and planetary motion. The Golapada deals with the celestial sphere, eclipses and the rotation of the Earth.
Place and date
Aryabhata states that he was twenty-three years old when 3,600 years of the Kali Yuga had passed, which corresponds to 499 CE, so he is usually said to have been born in 476. He is associated with Kusumapura, generally identified with Pataliputra, present-day Patna. India's first satellite, launched in 1975, was named Aryabhata in his honour.
His legacy in the calendar
Aryabhata's parameters were adopted by a whole school of astronomers, the Aryapaksha, and influenced calendar-making especially in South India. His method of reckoning planetary positions from a count of days was carried forward, refined and debated by later astronomers, including Brahmagupta, who criticised some of his ideas. The tradition of argument around his work is itself a sign of how seriously Indian astronomers took accuracy.