Section Summary

Kepler’s Laws of Planetary Motion

• All satellites follow elliptical orbits.
• The line from the satellite to the parent body sweeps out equal areas in equal time.
• The radius cubed divided by the period squared is a constant for all satellites orbiting the same parent body.

Newton’s Law of Universal Gravitation and Einstein’s Theory of General Relativity

• Newton’s law of universal gravitation provides a mathematical basis for gravitational force and Kepler’s laws of planetary motion.
• Einstein’s theory of general relativity shows that gravitational fields change the path of light and warp space and time.
• An object’s mass is constant, but its weight changes when acceleration due to gravity, g, changes.