# Would the Earth with 4 moons still be habitable?

I'm currently writing about an Earth sized planet that is 33% water and has 4 moons all the same size as our moon. All moons are 243,000 miles from the planet's surface and the planet takes 392 days to fully cycle its sun. I think the night cycle is fine, but have no idea how the moons would affect the planet itself.

• Vital questions: #1 How big is the planet? #2 How big are the moons? #3 How far away are each of the moons? – RonJohn Jul 31 '18 at 17:14
• All of what RonJohn said and, what kind of werewolves are you using, some werewolves are completely unaffected by the moon after all. – Ash Jul 31 '18 at 17:17
• Now, you could change your question so it reflects a world-rule rather than a story-plot. For example, "in my world, werewolves turn during a full moon. I'm developing a world with four moons. Their orbital periods are [explain]. The planet's orbital period is [explain.] Can you help me figure out how many full moons there will be in a year?" In this example, you've set the plot rule and are only asking us about the world-rule. – JBH Jul 31 '18 at 17:21
• @RonJohn, Tom's a first-time user. Have a llittle faith, baby... have a little faith. – JBH Jul 31 '18 at 18:08

Q:

Is it possible to have a stable orbit comprised of many moons(>2) that keep themselves roughly equal distance apart?

A:

If you want more than three moons, you can organize them in a Klemperer rosette, although this type of configuration is not stable.

The gravitational pull of moons that are not equidistant is also not stable. One or more will either be ejected or pulled crashing together, thus devastating the planet.

But, hey: werewolves. So ignore physics and just have four moons orbiting your planet...

• To amplify "not stable" is an astrodynamics way of saying "this won't happen" – James K Jul 31 '18 at 19:28
• But AFAIK there is no reason you couldn't have an Earth-sized planet with several moons in different orbits, which might have roughly the same apparent size as seen from the planet's surface. Jupiter has 4 moons roughly the size of Earth's Moon, and Pluto has 5 moons in apparently stable orbits (though 4 are quite small). – jamesqf Aug 1 '18 at 17:06
• @jamesqf but these real moons aren't in the same orbit (and that's what OP wants). – RonJohn Aug 1 '18 at 17:52
• @RonJohn: Yes, but as you point out, the OP can't HAVE what s/he wants and still have real-world physics. Moons with different orbits but similar apparent size is the best alternative. – jamesqf Aug 2 '18 at 19:10

33% water means there are probably no true oceans, or separate continents just some big lakes and major rivers so any tidal effects are going to be of minimal importance. I have the feeling that there will always be about a full moon's worth of light at night, and possibly enough reflected light during the day to cause a measurable effect, this might effect photosynthesis and the development of nocturnal/diurnal speciation.

Note the orbital stability of this scenario is questionable to say the least, a small gravitational fluctuation, like the transit of Neptune could bring the whole thing tumbling down.

• Incredibly useful, probably going to have to remove the other moons then unless I want to make major excuses. – Tom Holl Jul 31 '18 at 18:13
• @TomHoll I appreciate that you've found it a useful answer and I'm happy to help but you really should only upvote it as useful for now, it's good to give this stack at least 24 hours to let people contribute before you go to accepting an answer, we're spread across a lot of timezones. – Ash Jul 31 '18 at 18:15
• Ah yeah I always forget about time zones, thanks for reminding me. – Tom Holl Jul 31 '18 at 18:19