Eratosthenes Crater

Eratosthenes crater is 59 km wide and 3.6 km deep and it lies at the end of the Appenine mountain range.

This crater is named after the Greek mathematician who first calculated the circumference of the Earth very accurately over 2200 years ago. He had spent some time in Egypt and had observed in the southern city, Syene, known as Aswan today, at noon on the solstice, the sun cast no shadows meaning it was directly overhead. Another year in Alexandria, north of Syene, he noticed there were shadows cast at noon on the solstice. He concluded that the earth must be a sphere based on these findings so he began doing some arc measurements (circle math), he used a vertical rod and measured the length of the shadow and the height of the rod and calculated the angle to be 7 degrees, which is 1/50th of a circle. He then calculated the distance between the two cities and multiplied that number by 50 to come up with the circumference of the Earth.