Gravitation (Astronomy) (Paperback)

High Quality Content by WIKIPEDIA articles In astronomy, the discovery and application of Newton's law of gravity accounted for the detailed information we have about the planets in our solar system, the mass of the sun, the distance to stars and even the theory of dark matter. Although humans have not traveled to all the planets nor to the sun, these bodies' mass is known through the study of the law of gravity. In space everything is in an orbit around some massive object. They maintain orbit because of the force of gravity between them. Planets orbit stars, stars orbit galactic centers, galaxies orbit a center of mass in clusters, and clusters orbit in superclusters. By watching how the position of a planet changes with respect to earth over the course of a year, we can determine by using geometry how far that planet is from the sun compared to how far the earth is, thus getting the distance from that planet to the sun. Copernicus calculated the distances of the inner planets and Kepler noticed a relation between them and their orbits.