Āryabhaṭa (476 – 550 C.E.)

Āryabhaṭa  was the first in the line of great mathematician-astronomers from the classical age of Indian mathematics and Indian astronomy. His most famous works are the Aryabhatiya and Arya-Siddhanta.

Scientist Aryabhatt’s major work, Aryabhattiya (also Aryabhatiya), a compendium of mathematics and astronomy, divided into four pAdas or chapters: [note A:. open mouth, utter extended A].

1. gitikApAda – kalpa, manvantra, yuga, which present a cosmology, mahayuga 4.32 mn years.

2. gaNitapAda — covering mensuration (kShetra vyAvahAra), arithmetic and geometric progressions, gnomon/shadows (shanku-chhAyA), equations (kuTTaka ).

3. kAlakriyApAda -units of time; determination of positions of planets for a given day. Intercalary month (adhikamAsa). kShaya tithis seven-day week, with names of the days.

4. golapAda =Geometric/trigonometric aspects of the celestial sphere, shape of earth, etc.

Scientist Aryabhatta believed that the earth rotates about its axis.Lanka (Sri Lanka) is here a reference point on the equator, which was taken as the equivalent to the reference meridian for astronomical calculations.

Scientist Aryabhatta described a geocentric model of the solar system, in which the Sun and Moon revolve around the Earth.

The order of the planets in terms of distance from earth are taken as : the Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn, and the asterisms (groups of stars).

Scientist Aryabhatta states that the Moon and other planets shine by reflected sunlight.

Scientist Aryabhatta explains eclipses in terms of shadows cast by and falling on earth. Thus the lunar eclipse occurs when the moon enters into the earth-shadow.

Scientist Aryabhatta’s computation of Earth’s circumference works out as 24,835 miles, which was only 0.2% smaller than the actual value of 24,902 miles.

He achieved many centuries before what the modern scientists have been able to achieve now.