Aryabhata

Āryabhaṭa worked at Kusumapura (identified with ancient Pāṭaliputra, near modern Patna) and states in his own text that he composed the Āryabhaṭīya in 499 CE at the age of twenty-three — one of the few ancient Indian scientific works whose author, date, and even age at writing are known with this precision, because he tells us directly.

Āryabhaṭa states plainly that the Earth rotates on its own axis, and that the apparent daily motion of the stars is a consequence of that rotation rather than the stars themselves moving around a stationary Earth — a claim later Indian astronomers, including his own commentators, sometimes pushed back against, since it contradicted the more intuitive geocentric picture. He also gives a purely mechanical, shadow-based explanation of solar and lunar eclipses, at a time when eclipses were widely explained across many cultures, India included, as the seizing of the sun or moon by a demonic force (Rāhu/Ketu in the Puranic account).

Beyond astronomy, the Āryabhaṭīya develops trigonometric sine tables (jyā) used for astronomical calculation, works within a fully developed place-value decimal system, and gives an approximation of π accurate to four decimal places — stated as a ratio with an explicit note that it is an approximation, not an exact value, which is itself a notable piece of mathematical self-awareness for the period.

Āryabhaṭa's work was influential enough to be both extended and contested by the astronomers who followed him — Brahmagupta engaged with his methods critically, and the debate over Earth's rotation continued within Indian astronomy for centuries. That later scholars felt the need to argue with him, rather than ignore him, is itself a measure of how seriously the Āryabhaṭīya's claims were taken as live scientific propositions rather than settled orthodoxy.