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.
History of the center of the Universe southern constellations rise higher above the horizon, and the shadow of Earth on the Moon during a lunar eclipse is round, and spheres cast circular shadows while discs generally do not. This understanding was accompanied by models of the Universe that depicted the Sun, Moon, stars, and naked eye planets circling the spherical Earth, including the noteworthy models of Aristotle (see Aristotelian physics) and Ptolemy. This geocentric model was the dominant model from the 4th century BCE until the 17th century CE. Heliocentrism, or heliocentricism, is the astronomical model in which the Earth and planets revolve around a relatively stationary