3rd century BCE
The Greeks also tried to solve the mystery of Earth's position in the universe. Most people thought Earth did not move and was the center of the universe. They also thought the Sun, Moon, and stars orbited around the Earth. Around the 3rd century BC, Aristrachus, a Greek scientist, believed that the Earth and everything else circled the Sun. This was a very different idea compared to earlier beliefs. Aristrachus also suggested that the Earth spins on an axis, which causes day and night.