eratosthenes

noun

1. 276?–195? b.c., Greek mathematician and astronomer at Alexandria.

noun

1. ?276–?194 bc, Greek mathematician and astronomer, who calculated the circumference of the earth by observing the angle of the sun’s rays at different places

1. Greek mathematician and astronomer who is best known for making an accurate estimate of the circumference of the Earth by measuring the angle of the Sun’s rays at two different locations at the same time. He also invented a method for listing the prime numbers that are less than any given number.