# Real life physics of Having a smaller Moon orbit the Moon of a planet [duplicate]

Is it probable/possible? What would it look like? How would it effect the other bodies long term? How would culture change if intelligent life developed on the host planet?

• Aug 13 '17 at 17:33
• @Monica Cellio Thanks for the warm welcome! I'll keep that in mind and make sure to be more specific when phrasing questions next time Aug 13 '17 at 20:25

It's possible, and has already happened in the past (the Apollo spacecraft and other lunar orbiters), albeit for a what period of time.

Depending on the relative sizes of the three bodies involved, it could be stable (if the moonlet orbiting the moon is small in comparison to the moon, and orbited close to it, it would most likely be stable), but as there isn't a general analytic solution to the three-body problem, there is no way to prove that it is stable. (You could approximate it by numerical analysis if you had a specific moonlet size and orbital radius in mind, but the error would increase over the simulation time).

As for how it might affect the culture of an intelligent species, they might come up with stories about the moon god/goddess and his/her companion/son/daughter/faithful pet, but would otherwise be similar in concept to any of the many cultural stories about the moon that exist on our Earth.

• Actually there are at least two stable solutions for the three-bodies-problem and they are Lagrange points L3 and L4. You can argue bodies in those locations are orbiting around the satellite, even if it doesn't look so. ;) Aug 13 '17 at 18:29
• @ZioByte, Lagrange and others have devised a number of analytic solutions (i.e. mathematical equations) for specific configurations, but no solution for the general case. By definition, a Lagrange point is where the gravitational forces between the larger and small bodies balance out, hence anything at a Lagrange Point will orbit the system's barycenter. In this case, the barycenter of the Earth-Moon system is inside the Earth, so a small object at a Lagrange Point is unlikely to change that much. So, we can conclude that such an object will not be orbiting the Moon.
– Pak
Aug 13 '17 at 23:21

We human have sent satellites orbiting the moon. This shows it is possible, provided there is a significant different in masses.

At the very end the Moon orbits the Earth, the Earth orbits the Sun, the Sun orbits the center of the Milky Way, the Milky Way orbits something else...

Check out the Pluto system of Kuiper belt objects. Several objects orbit each other and a common center of mass in a chaotic system.

• Those objects don't really all orbit each other, per se; Pluto (and Charon) are firmly by the center of mass. At any rate, Pluto isn't a planet by a long shot. Aug 13 '17 at 17:35
• Thank you for the edit - I hate auto-misspell on my phone Aug 15 '17 at 3:12