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:
“This we take it is the grand characteristic of our age. By our skill in Mechanism, it has come to pass, that in the management of external things we excel all other ages; while in whatever respects the pure moral nature, in true dignity of soul and character, we are perhaps inferior to most civilised ages.”
—Thomas Carlyle (1795–1881)
“Only that which points the human spirit beyond its own limitations into what is universally human gives the individual strength superior to his own. Only in suprahuman demands which can hardly be fulfilled do human beings and peoples feel their true and sacred measure.”
—Stefan Zweig (18811942)
“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)