Motions of the Planets

A montage of all the planets, except Pluto.
Click on image for full size (94K JPG)
Image courtesy of NASA/JPL.

For many years, people believed that the Earth was the center of the universe, that the Earth didn't move and that the planets, Sun, moon, and the stars moved on spheres around the Earth. Astronomers such as Copernicus and Galileo suggested that the Sun was the center of the solar system. But people weren't ready to accept that the Earth wasn't the center of the universe.

Johannes Kepler studied the planets and the work of his teacher, Tycho Brahe. He proved that this theory could explain the motions of planets. His work completely changed the way we view the universe.

Kepler formulated three laws which describe how the planets move on their orbits around the Sun. Kepler derived these laws, but he didn't understand why planets are forced to move in this way. Gravity wasn't "discovered" until Sir Isaac Newton, who could then show that Kepler's laws are simply a consequence of the force of gravity between the Sun and the planets.

A table of orbital data for the planets.

Last modified prior to September, 2000 by the Windows Team

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Motions of the Planets

A montage of all the planets, except Pluto. Click on image for full size (94K JPG) Image courtesy of NASA/JPL.

A montage of all the planets, except Pluto.
Click on image for full size (94K JPG)
Image courtesy of NASA/JPL.