attraction sphere

For almost 2000 years—from the time of Aristotle until the early 17th century—popular theory posited that the earth was the center of the universe, and that everything in space rotated around it in concentric spheres filled with a heavenly fifth element called quintessence. Astronomers believed that the turning of these spheres accounted for the orbits of the heavenly bodies, and that they moved to the …

Read more in this article about some frequently asked questions and fun facts related to our definitions.