Circles and PiSphere

Eratosthenes of Cyrene (c. 276 – 195 BCE) was a Greek mathematician, geographer, astronomer, historian, and poet. He spent much of his life in Egypt, as head of the library of Alexandria. Among many other achievements, Eratosthenes calculated the circumference of the Earth, measured the tilt of the Earth’s axis of rotation, estimated the distance to the sun, and created some of the first maps of the world. He also invented the “Sieve of Eratosthenes”, an efficient way to calculate prime numbers.

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