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:
“It is perhaps the principal admirableness of the Gothic schools of architecture, that they receive the results of the labour of inferior minds; and out of fragments full of imperfection ... raise up a stately and unaccusable whole.”
—John Ruskin (1819–1900)
“I consider women a great deal superior to men. Men are physically strong, but women are morally better.... It is woman who keeps the world in balance.”
—Mrs. Chalkstone, U.S. suffragist. As quoted in History of Woman Suffrage, vol. 2, ch. 16, by Elizabeth Cady Stanton, Susan B. Anthony, and Matilda Joslyn Gage (1882)
“I would sell my life to avoid
the pain that begins in the crib
with its bars or perhaps
with your first breath
when the planets drill
your future into you....”
—Anne Sexton (1928–1974)