4 ms·
Earth-Moon centre of mass is inside Earth, so, it's obvious that the Moon is orbiting the Earth, not both orbiting something else. 1% is an arbitrary threshold
by jojobas 6y ago
Earth-Moon centre of mass is inside Earth, so, it's obvious that the Moon is orbiting the Earth, not both orbiting something else.
1% is an arbitrary threshold and solar orbit is dependent on external circumstances rather than the Earth-Moon system itself.
- dotancohen 6y ago> Earth-Moon centre of mass is inside Earth, so, it's > obvious that the Moon is orbiting the Earth, not both > orbiting something else. I used to agree with that school of thought, until I came up with a small thought experiment. Consider two bodies that are right on the planet-moon / dual-planet definition threshold. Intuitively, increasing the orbital distance between them would push them in the direction of which definition: planet-moon or dual-planet? I'd tend to say that separating them further would tend more towards planet-moon. Yet doing so moves the system's center of mass outside the larger body, so would actually push the system into the dual-planet definition by that criterion.
- shawnz 6y agoThe barycentre being inside of one of the things in the system is also an arbitrary threshold, isn't it? The barycentre of the Sun and Jupiter isn't inside of the Sun.. so does that mean Jupiter doesn't orbit the Sun?