Inferior and superior planets the orbit of Earth. These terms were originally used in the geocentric cosmology of Claudius Ptolemy to differentiate as inferior those planets (Mercury and Venus) whose epicycle remained co-linear with the Earth and Sun, and as superior those 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. When Earth is stated or assumed to be the reference point: The terms are sometimes used more generally; for example, Earth is an inferior planet relative to Mars.
The Book of the Short Sun least "Locus: The Magazine of the Science Fiction & Fantasy Field" considered the three "Short Sun" volumes separately for annual "Best Novel" awards. The "Short Sun" of the title is an ordinary star, in contrast to the "Long Sun" of the Whorl where the narrator grew up. Most of the story takes place in a star system with two habitable planets, Blue and Green, which lend their names to the first two volumes. The Whorl of volume three's title is the generation ship setting of "Long Sun". The Tor hardcover editions (see table) were almost 1200 pages long in sum.