Editing Inferior and superior planets

{{Short description|Geocentric cosmology of Claudius Ptolemy}}
In the [[Solar System]], a [[planet]] is said to be '''inferior''' or '''interior''' with respect to another planet if its [[orbit]] lies inside the other planet's orbit around the [[Sun]].<ref>{{Cite web |date=2023-07-20 |title=Chapter 1: The Solar System |url=https://science.nasa.gov/learn/basics-of-space-flight/chapter1-2/ |access-date=2025-05-05 |website=NASA Science |language=en-US}}</ref> In this situation, the latter planet is said to be '''superior''' to the former. In the reference frame of the [[Earth]], where the terms were originally used, the inferior planets are [[Mercury (planet)|Mercury]] and [[Venus]], while the superior planets are [[Mars]], [[Jupiter]], [[Saturn]], [[Uranus]] and [[Neptune]]. [[Dwarf planet]]s like [[Ceres (dwarf planet)|Ceres]] or [[Pluto]] and most [[asteroids]] are 'superior' in the sense that they almost all orbit outside the orbit of Earth.<ref>{{Cite web |date=2020-09-08 |title=Inferior and superior planets: what's the difference? |url=https://www.skyatnightmagazine.com/space-science/inferior-superior-planets-difference |access-date=2025-05-05 |website=BBC Sky at Night Magazine |language=en}}</ref>

== History ==
These terms were originally used in the [[geocentric]] [[cosmology]] of [[Claudius Ptolemy]] to differentiate as inferior those planets ([[Mercury (planet)|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.<ref>{{cite book
 |author1=Lakatos, Imre |author2=Worrall, John |author3=Currie, Gregory |editor1=Worrall, John |editor2=Currie, Gregory | date=1980
 | title=The Methodology of Scientific Research Programmes
 | page=186 | publisher=[[Cambridge University Press]]
 | isbn=0-521-28031-1 }}</ref><ref>{{Cite web |last=Dobrijevic |first=Daisy |date=2021-12-17 |title=Geocentric model: The Earth-centered view of the universe |url=https://www.space.com/geocentric-model |access-date=2025-05-05 |website=Space |language=en}}</ref>

In the 16th century, the terms were modified by [[Nicolaus Copernicus|Copernicus]], who rejected Ptolemy's geocentric model, to distinguish a [[planet]]'s [[orbit]]'s size in relation to the [[Earth]]'s.<ref>{{cite book | first=Thomas S. | last=Kuhn | date=1985 | page=[https://archive.org/details/copernicanrevolu0000kuhn/page/172 172] | title=The Copernican Revolution: Planetary Astronomy in the Development of Western Thought | edition=4th | publisher=[[Harvard University Press]] | isbn=0-674-17103-9 | url=https://archive.org/details/copernicanrevolu0000kuhn/page/172 }}</ref>

==Planets in each category==
When [[Earth]] is stated or assumed to be the reference point: 
*"Inferior planet" refers to [[Mercury (planet)|Mercury]] and [[Venus]], which are closer to the [[Sun]] than Earth is.
*"Superior planet" refers to [[Mars]], [[Jupiter]], [[Saturn]], [[Uranus]], and [[Neptune]] (the latter two added later), which are further from the Sun than Earth is.<ref>{{Cite web |title=Superior Planet {{!}} COSMOS |url=https://astronomy.swin.edu.au/cosmos/*/Superior+Planet |access-date=2025-05-05 |website=astronomy.swin.edu.au}}</ref>

The terms are sometimes used more generally; for example, Earth is an inferior planet relative to Mars.

== Other planetary terms ==
Interior planet now seems to be the preferred term for astronomers. Inferior/interior and superior are different from the terms [[inner planet]] and [[outer planet]], which designate those planets that lie inside the [[asteroid belt]] and those that lie outside it, respectively. Inferior planet is also different from [[minor planet]] or [[dwarf planet]]. Superior planet is also different from [[gas giant]].

==References==
{{reflist|2}}

{{Ancient Greek astronomy}}
{{Solar System}}

[[Category:Planets of the Solar System]]
[[Category:Technical factors of astrology]]
[[Category:Solar System]]