# An Argument The Moon is a PLANET! Source: https://www.youtube.com/watch?v=xgFKxFX3IwY Recap page: https://rapidrecap.app/video/xgFKxFX3IwY Generated: 2025-12-22T19:06:43.909+00:00 --- ## Quick Overview The Moon meets all three criteria set by the International Astronomical Union (IAU) for an object to be classified as a planet, suggesting that the IAU's current definition is flawed because it explicitly excludes satellites, leading to the conclusion that the Moon should scientifically be considered a planet. **Key Points:** - The IAU's 2006 resolution defines a planet by three criteria: orbiting the Sun, having sufficient mass for hydrostatic equilibrium (nearly round shape), and having cleared the neighborhood around its orbit. - The Moon satisfies criteria (a) (orbiting the Sun, as it orbits the Earth, which orbits the Sun) and criteria (b) (being gravitationally round), as it is more massive than Pluto and Ceres. - The Moon fails criterion (c) because it is a satellite orbiting the Earth, which the IAU definition explicitly excludes via footnote (1) which lists only Mercury through Neptune as planets. - The video argues that if the Sun (a star) were placed in the outer solar system, it would fail criterion (c) due to being orbited by captured objects, yet the IAU definition would still label it a planet. - The author suggests the IAU's definition is arbitrary and culturally biased, noting that if the definition were purely scientific (not excluding satellites), the Moon, Ceres, and Io would qualify as planets. - The video contrasts the IAU's prescriptive list (Mercury through Neptune) with a potentially more scientifically consistent classification based on physical properties, as illustrated by Margot's Planetary Discriminant chart. ![Screenshot at 00:06: The presenter marks Pluto with an 'X' on a diagram illustrating the initial list of 'The 9 Planets,' visually representing the moment Pluto is disqualified under the IAU's definition.](https://ss.rapidrecap.app/screens/xgFKxFX3IwY/00-00-06.jpg) **Context:** This video critiques the 2006 International Astronomical Union (IAU) definition of a planet, which controversially reclassified Pluto as a dwarf planet. The presenter breaks down the three criteria established by the IAU for an object to be considered a planet in our Solar System and then tests whether the Earth's Moon meets these criteria, concluding that it meets the first two but fails the third because it is a satellite, a condition explicitly excluded by the definition's footnotes. ## Detailed Analysis The video argues that the Moon should be classified as a planet based on the IAU's own criteria, revealing that the definition is inconsistent and arbitrary. The IAU Resolution 5 defines a planet as a celestial body that (a) orbits the Sun, (b) is nearly round due to hydrostatic equilibrium, and (c) has cleared its orbital neighborhood. The Moon satisfies (a) because it orbits Earth, which orbits the Sun, and it satisfies (b) as it is gravitationally rounded (01:03). However, the Moon fails (c) because it orbits Earth, and the definition explicitly excludes satellites (02:45, 02:54). The presenter further shows that if the Earth were moved far out, the Moon would still orbit the Sun (from the Sun's perspective, the Moon is nudged along Earth's orbit (00:35)), and if the Earth suddenly vanished, the Moon would continue orbiting the Sun, thus satisfying (a) and (b) independently. The inherent problem, the video asserts, is criterion (c) combined with the exclusion of satellites, which is a cultural distinction rather than a physical one (02:31). The presenter demonstrates that if a star much smaller than the Sun captured the solar system's bodies into its orbit, that star would meet all three criteria and be called a planet according to the IAU's rules (05:06), highlighting the definition's self-referential nature. The video concludes by showing that the IAU's footnote (i) explicitly lists only eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune), effectively making the definition prescriptive rather than descriptive of natural categories. ### IAU Planet Definition Breakdown - Criterion a (Orbit Sun) - Criterion b (Round/Hydrostatic Equilibrium) - Criterion c (Cleared Orbit) ### Moon Qualification Analysis - Meets a and b because it is massive and orbits the Sun via Earth - Fails c because it is a satellite, explicitly excluded by footnote (i) ### Critique of Criterion C - Demonstrates that if the Earth vanished, the Moon would still orbit the Sun, satisfying criteria a and b independently - Shows that a captured dwarf star would pass all three criteria if it were not explicitly excluded as a satellite ### Scientific vs. Cultural Classification - Argues that the IAU's definition is culturally biased by excluding satellites, contrasting it with scientific classifications like Margot's Planetary Discriminant chart (01:53) ### Conclusion on Arbitrary Listing - Highlights IAU Footnote (i) which simply lists the eight planets (Mercury through Neptune), suggesting the definition is ultimately a list rather than a justification (03:04) ![Screenshot at 00:04: The beginning of the video where the presenter draws the original nine planets and introduces the IAU official standing next to a list of three criteria for 'Planet'.](https://ss.rapidrecap.app/screens/xgFKxFX3IwY/00-00-04.jpg) ![Screenshot at 00:25: Display of IAU Planet Definition Criterion \(a\): 'A planet\(1\) is a celestial body that a. is in orbit around the Sun,' setting up the formal analysis.](https://ss.rapidrecap.app/screens/xgFKxFX3IwY/00-00-25.jpg) ![Screenshot at 01:06: Visual comparison showing the Moon \(large and round\) next to several irregularly shaped asteroids/comets, illustrating the concept of hydrostatic equilibrium.](https://ss.rapidrecap.app/screens/xgFKxFX3IwY/00-01-06.jpg) ![Screenshot at 01:58: Margot's Planetary Discriminant chart showing the 'clear orbit' zone \(green area\) where planets like Earth and Jupiter reside, and the zone below the diagonal line where Pluto resides.](https://ss.rapidrecap.app/screens/xgFKxFX3IwY/00-01-58.jpg) ![Screenshot at 03:04: Display of Footnotes Resolution 5, specifically footnote \(i\), which lists the eight planets by name, showing the definition is prescriptive rather than purely derived from the three criteria.](https://ss.rapidrecap.app/screens/xgFKxFX3IwY/00-03-04.jpg)