I talk about things I find interesting. I find a lot of things interesting…

Indian mathematics: Aryabhata

by Ken Arnold on Wed 20 February 2013

Today’s google doodle is on Copernicus, who is credited with first proposing that the Earth moves around the Sun. Someone commenting on this claimed that Aryabhata had come up with the idea long before in India. I know that India had advanced math and astronomy for its time, and was the place where many advances were made (most famously the digit “zero” and the positional notation system we use for writing numbers). But i don’t know much else.

So I went to the Wikipedia article on Aryabhata to see whether this claim was true. Many countries like to claim precedence for ideas, and Indians are no different, so I wasn’t taking this at face value. It turns out that Aryabhata clearly decided that the Earth rotated on its axis and the stars stayed still. But (according to Wikipedia) generally it is not accepted that he considered the planets to orbit the Sun. Like many European astronomers he made adjustments for the planetary orbits to account for the errors introduced by putting the Earth at the the center, but he didn’t seem to make the leap to dropping those corrections in favor of a model that had the planets orbit the Sun itself.

This is not to take away from the brilliance of the man. He figured approximated π to five decimal places, and created a table of sines that was used for centuries. (The sine/cosine/tangent system is another Indian invention — our word comes through an interesting etymology from their word, via the Arabs.) He derived very accurate estimates of day and year length.

So I’m going to take Copernicus’s day as a reminder to explore more about the complex roots of our mathematical, astronomical, medical, and other scientific heritage.

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