This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (July 2009)

The terms "inferior planet" and "superior planet" were originally used in the geocentric cosmology of Claudius Ptolemy to differentiate those planets (Mercury and Venus) having an epicycle that remained collinear with the Earth and Sun, compared to the planets (Mars, Jupiter, and Saturn) that did not.^[1]

In the 16th century, the terms were modified by Copernicus, who rejected Ptolemy's geocentric model, to distinguish a planet's orbit's size in relation to the Earth's.^[2]

• "Inferior planet" is used in reference to Mercury and Venus, which are closer to the Sun than the Earth.

• "Superior planet" is used in reference to Mars, Jupiter, Saturn, Uranus, Neptune, and all the known minor and dwarf planets, including Ceres and Pluto, which are farther from the Sun than the Earth.

The terms are sometimes used more generally: for instance, the Earth is an inferior planet as seen from Mars.

This classification should not be confused with the terms inner and outer planet, which designate those planets which lie inside the asteroid belt and those that lie outside it, respectively. "Inferior planet" should also not be confused with the very different minor planet or dwarf planet.

[edit] References

This astronomy-related article is a stub. You can help Wikipedia by expanding it. v • d • e