The terms "inferior planet" and "superior planet" were originally used in the geocentric cosmology of Claudius Ptolemy to differentiate as 'inferior' those planets (Mercury and Venus) whose epicycle remained collinear with the Earth and Sun, compared to the 'superior' planets (Mars, Jupiter, and Saturn) that did not.
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.
- "Inferior planet" is used in reference to Mercury and Venus, which are closer to the Sun than the Earth is.
- "Superior planet" is used in reference to Mars, Jupiter, Saturn, (and later additions Uranus and Neptune), which are farther from the Sun than the Earth is.
The terms are sometimes used more generally: for instance, the Earth is an inferior planet as seen from Mars.
This classification is different from 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" is also very different to minor planet or dwarf planet.
Famous quotes containing the words inferior, superior and/or planets:
“If the only new thing we have to offer is an improved version of the past, then today can only be inferior to yesterday. Hypnotised by images of the past, we risk losing all capacity for creative change.”
—Robert Hewison (b. 1943)
“If it is the result of a pure love, there can be nothing sensual in marriage. Chastity is something positive, not negative. It is the virtue of the married especially. All lusts or base pleasures must give place to loftier delights. They who meet as superior beings cannot perform the deeds of inferior ones.”
—Henry David Thoreau (1817–1862)
“Marriage is the clue to human life, but there is no marriage apart from the wheeling sun and the nodding earth, from the straying of the planets and the magnificence of the fixed stars.”
—D.H. (David Herbert)