Other Free Encyclopedias » 21st Century Webster's Family Encyclopedia » 21st Century Webster's Family Encyclopedia - Erasistratus to Federalism

Eratosthenes

earth sun

Eratosthenes (c.275–c.195 B.C.), Greek mathematician and astronomer. Postulating that the earth was round and that the sun's rays were parallel, he measured the lengths of shadows in different locations and used geometrical reasoning to estimate the circumference of the earth with remarkable accuracy. He also determined the size and distance of the sun and moon. The sieve of Eratosthene is a practical method for identifying prime numbers.

Erbium [next] [back] Thomas Erastus

User Comments

Your email address will be altered so spam harvesting bots can't read it easily.
Hide my email completely instead?

Cancel or