20. Archimedes (c.287 BC – c.212 BC)

Original language: Greek.

I read The Sand-Reckoner and skimmed On the Equilibrium of Planes and On Floating Bodies.

The Sand-Reckoner

Archimedes set out to find an upper bound for the number of grains of sand that would fit into the “universe” (which, to the ancients, was a finite area bounded by the stars seen from Earth). I find that charming and audacious. To do this he had to estimate quantities like the size of the universe, the size of Earth, and the size of the Sun and the Moon. And he invented his own system for discussing and naming large numbers. In the end he came up with 10 to the 63rd power for the number of grains of sand — that sounds like a good estimate.

Another thing that surprised me is that some ancient Greeks thought the Earth revolved around the Sun. That was Aristarchus of Samos’s model. And Archimedes used that model. 

The Sand-Reckoner is a “jeu d’esprit written for the layman… that nevertheless contains some profoundly original mathematics.” – brittanica.com

I’m really glad I read it. 


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