3 ms·

I thought to be classified as a moon you needed a distinctly observable gravity field?

• beckingz 7y ago
  Technically the earth hasn't cleared it's orbit because of the moon. So the earth is not a planet.
  • maxerickson 7y ago
    The Moon is ~2% the volume of the Earth, you are stretching the definition of similar pretty hard.
    • tyfon 7y ago
      Also when you take into account that the moon is formed from the outer layers of the earth it lacks a lot of the heavy elements like iron that the Earth has in it's core making the mass about 1.2% of the mass of the Earth [1]. It's much smaller compared to the earth than you would think just by looking at it but it is still a very large moon for a planet the size of the Earth. "Of all the moons of the eight planets, Earth's moon is by far the largest relative to its planet, with a diameter of 3476 km and hence a ratio to Earth's diameter of 0.2764. By comparison, the next largest moon relative to a major planet (Triton of Neptune) has a diameter ratio of just .0546." [2] The moon is also larger than Pluto (in the same reference as above) :) [1] https://www.universetoday.com/20489/moon-compared-to-earth/ https://www.universetoday.com/20489/moon-compared-to-earth/ [2] https://en.wikibooks.org/wiki/General_Astronomy/Planetary_Moons https://en.wikibooks.org/wiki/General_Astronomy/Planetary_Mo...
  • jerf 7y ago
    If we're going down to that level of pedentry (and why not?), the Earth is not a planet in that sense, it's part of a double-planet system.
    • beckingz 7y ago
      That was Alan Stern's take if I recall correctly.