# What are Keplers Laws?

Kepler’s laws are three equations which govern the motion of astronomical bodies. Kepler’s laws were first discovered by the seventeenth-century astronomer Johannes Kepler while analyzing data collected by Tycho Brahe. Kepler’s laws are an extension of Copernicus’s earlier heliocentric theory, and eventually paved the way for Isaac Newton’s complete theory of how bodies interact. Newton’s equations of gravity and motion can be used to derive Kepler’s laws, if you assume that there are only two bodies, one of which is fixed, and one of which is orbiting at less than escape velocity. Although Kepler’s laws were originally developed to explain planetary motions, they apply to any body which is in orbit around a much more massive body. The first of Kepler’s laws states that a planet, or any other object in orbit around the Sun, follows an elliptical path with the Sun at one focus. The shape of these ellipses depends on the Sun’s mass, the planet’s position, and the planet’s velocity. A set