Early astronomers used only their eyes to look at the stars. They made maps of the constellations and stars for religious reasons and calendars to work out the time of year. Early civilisations such as the Maya people and the Ancient Egyptians built simple observatories and drew maps of the stars positions. They also began to think about the place of Earth in the universe. For a long time people thought Earth was the center of the universe, and that the planets, the stars and the sun went around it. This is known as geocentrism.