# World with 3 moons [duplicate]

I'm writing a story set in a world with 3 moons and I have a couple of questions about how that would work. I understand that the tidal patterns would be significantly different than Earths and I'm writing that in as part of the story (wild oceans, unpredictable shores/ports).

My question is what would be a logical setup for 3 moons? What I mean is, would one moon be the size of ours (which I understand is unique relative to moons on other planets) the second 1/5th, the third 1/10th ect? What would be a logical size differences between them to be functional (by functional, I mean functional to a "normal" sort of life on the planet)? I'm asking because I'd like to describe how they look at night in certain parts of my story.

Also, how much time would pass between when the 3 moons established an orbit and to when one crashed into another? Millions of years? Billions? I'm curious as to this because I'd like to know if there is enough time since they all 3 arrived to have developed life and if there is enough time left over till the crash and cause mass extinction on the habitable planet.

• 1. I suggest you search existing questions here first. IMHO, this recent question covered a fair bit of what you'll want to know: worldbuilding.stackexchange.com/questions/66290/… Jan 5, 2017 at 21:08
• What's the size of base planet? Why don't you take, say, Jupiter, and just remove one of galilean moons (and ignore small ones)? Jan 5, 2017 at 21:08
• Roughly the size of Earth but with much more water, less land space. I'll take a look at the Jupiter moons however, I just don't know enough about the moons around other planets to know exactly where to research so thank you for that direction! Jan 5, 2017 at 21:14
• Actually, from the limited sample we have, multiple moons is the norm. Earth is the only planet with just one. Venus & Mercury have none, all the rest have more. Note that if they're of any great size, they're likely to be locked in orbital resonance, like Jupiter's inner 3 Galilean moons: en.wikipedia.org/wiki/Orbital_resonance Jan 5, 2017 at 22:22
• On tides, see this question. You can model that. Jan 6, 2017 at 4:30