WORLD CIVILIZATION

Detailed explanation-1: -In the third century BCE, Eratosthenes, a Greek librarian in Alexandria, Egypt, determined the earth’s circumference to be 40, 250 to 45, 900 kilometers (25, 000 to 28, 500 miles) by comparing the Sun’s relative position at two different locations on the earth’s surface.

Detailed explanation-2: -Eratosthenes was also the first to calculate the tilt of the Earth’s axis, which he figured with remarkable accuracy; the finding was reported by Ptolemy (85-165 CE). Eratosthenes also calculated the distance from the Earth to the Moon and to the Sun, but with less accuracy. He made a catalog of 675 stars.

Detailed explanation-3: -Eratosthenes was a Greek mathematician who is famous for his work on prime numbers and for measuring the diameter of the earth.

Detailed explanation-4: -This illustration shows how Eratosthenes actually calculated the circumference of the Earth. At noon on the summer solstice, Eratosthenes measured the length of the shadow cast by a column of known height at Alexandria.