Hypothetical: effects of multiple moons on the planet?

the tilt of the planet might wobble… changing the seasons

an incredible hot Earth, tidal forces from the two moons tugging on the Earth could cause so much friction within the planet that it would be a hot steamy jungle.

Awesome Mach storms, according to the Anne McCaffrey “Killashandra Ree” series. Fearfully cold weather, and a third pole according to the MZB “Darkover” series.

Do both have a gravitational pull?

@rowenaz

Of course it does. How could an orbiting object not have a gravitational pull? Doesn’t everything that has mass have a gravitational pull?

/me is waiting with ‘bated breath for @wundayatta’s response. ^_^

The tides would be much more complex and perhaps less predictable. If the two moons were on the same side of the earth, the tides would be very high. If they were on opposite sides, the tides would be smaller—how much smaller depends on the relative masses of the moons. Anyway, you could probably write any kind of weird tide you wanted with a double moon system.

There there’s the light at night. Apparently, tomatoes ripen more under a full moon. Without a full moon, they won’t ripen as much. With two moons, each being full at different times, you might have a much different tomato yield.

And tomatoes aren’t the only flora (or indeed, fauna) that are affected by the light of the moon. You’d have to research it, but I’m sure you’d find a lot of interesting moonlight effects.

If your story is a bit magical, then imagine the werewolf on a double full moon! Or what would happen to vampires? Would their movement be inhibited on double full moons nearly as much as during the day? Would this make them even more frantically active on double new moons? They myths about double night, as it might be called, could be an interesting thing to play with.

Have you ever read Asimov’s “Nightfall?” If not, you should. The planet is in a six moon system where full dark night happens once every two thousand years. This has a profound effect on the civilization, as everyone freaks out and goes absolutely apeshit each time it happens. So much so, that civilization falls, and has to be rebuilt over the next 2000 years, only to be destroyed again.

And the moons could not always be opposite each other, unless they were the same mass and somehow were stable in opposite orbits. I’m not sure, but I don’t think that would be possible. There’s something called the “three body problem.” I’m not sure what it is, but since they are always looking for a solution, it seems to me that it might be something about how impossible it is to solve such a problem. Maybe you can never predict the orbits in a system with three bodies.

Perhaps the culture knows this, and is constantly wondering when doom will fall, as the system destroys itself.

[Edit]
Yup: here’s what wikipedia has to say about the three body problem. It seems to me that such systems (which are everywhere) are inherently unstable. Your planet would probably be worse off than us when we consider the Earth, the Moon, and the Sun.

well, it would have some effect on the tides of the ocean for a start. it would probably change evolution to some degree too, if its big enough to reflect light from the sun causing it to be lighter at night then we maybe would have more nocturnal animals, and maybe less animals with enhanced vision, such as cats. maybe there would be no bats either.

and as a side note, the earth does already have two moons, the second one is called cruithne

Don’t discount the impact on the females of those species who have a menstrual cycle.

Mass and orbital rotation means a lot when it comes to gravitational pull. The moon is even moving away from us. How close the bodies are to the planet, of course, have a large effect, so you can make all sorts of effects, or very few and blame it on the distance.

@wundayatta has a really good point about the biological effects of the moon on our planet. Did you know that a woman who’s menstrual cycle is closest to the moon’s cycle is more fertile. http://www.athenainstitute.com/lunarmpl.html
There are insects, nocturnal animals, sea creatures, they all get triggered for mating, feeding, migrating… by the moon. You could add a certain ‘duality’ to the animal kindom on your plant… ‘Team Luna’ and ‘Team Mini-moon’ We are also losing our moon. Darwin predicted it, NASA confirmed. 2 inches a year.

As for tides, it’s a pull-me, pull-you scenario. The moon pulls on the water, but the earth spins at a higher rate than the moon goes around the earth, so the ‘bulge’ of water rises in front of the moon, and this bulge actually pulls on the moon, effecting it’s orbit.

I found a pretty neat article on ‘What would earth be like if there was no moon.’ which should give you some cool ideas, too. http://www.astrosociety.org/education/publications/tnl/33/33.html

Well, it wouldn’t really depend upon the size, but the mass and distance. The two moons would have to be in different orbits, otherwise they’d eventually crash. Otherwise, the above posters have it right in that there would be more complicated tides, but more importantly for us, there would probably be even more active plate techtonics with increased earthquake and volcano activity.

The three body problem is a mathematical problem that involves the calculation of orbits using classical Newtonian mechanics. It doesn’t necesarily suggest there will be a problem with stability in the system – it applies just as much to the whole solar system as it does to the Jovian satellite system. It’s just a right bugger to calculate the orbits of three or more items in a system when they are gravitationally interacting.

There are all sorts of interesting avenues to explore from there being two moons though – in a stable system, the moons may be in orbital resonance – giving predictable tides and other effects, and the system would have Lagrange points and Trojan-like microsatellites. The two moons could even shepherd a ring system, which could arise from the interactions of the orbiting bodies and the gravity of the parent planet with the defunct 3rd moon.

@the100thmonkey Ah! That Trojan thing sounds just about perfect.

Can I describe how hard it is to make (pseudo)science fit mythology, as opposed to writing mythology to fit the science? Oi vey.

So, according to that theory, I could have a considerably smaller moon sharing orbit with the “normal” moon, without worrying about the impending death and destruction of lunar collision. And the goddess has a son. Yay.

I also like the idea of the Laplace redonance (in the orbital resonance link), thought that would require three moons, wouldn’t it? And that would wreak some serious havoc on tides.

Plate tectonics… that’s actually really helpful. I needed an excuse for a few “drifting” landmasses.

Sorry, this is off topic but I remember reading a story about a planet with multiple suns which had one long and endless day. Eventually all the suns set at the same time and the inhabitants thought it was the end of the world. I can’t remember the title.

@flutherother The title is Nightfall by Isaac Asimov
Go to here if you want to have it read to you in podcast form. It’s a really good rendition.
http://www.escapepod.org/2007/04/05/ep100-nightfall/

You are a genius!! Thank you.

^_^

Dear Mods: I hereby determine all hypothetical celestial Science-Fiction discussion as “On Topic” for purposes of this thread. Thank you, @Seek_Kolinahr

@flutherother I already mentioned Nightfall above. It really is worth reading the thread.

@wundayatta @the100thmonkey… I wish I could sit down with you two and brainstorm. Maybe with @mattbrowne as well. I’m going crazy trying to figure all this out – the axis of the planet, the angle and speed at which the moons orbit (so I don’t have a solar eclipse every three days), how long a day should be… A lesser being would just say “It works because it’s fantasy” and do whatever they want, but I have to have my solar system make something vaguely resembling sense – even if the explanation is only in my notes. Dammit.

Build a model. See how it works. Here’s a unix program for modeling the paths of stars. Here are some other calculators. The “elliptical”: orbit one looks like it could be helpful—no, the link leads nowhere, but this place looks like it was built for science fiction writers.

wundayatta Sorry, didn’t realise you had mentioned Nightfall earlier. Another idea I had, which is my own as far as I know, was for a new planet in our solar system. It is unknown as it lies an the far side of the sun where we can never see it. Intriguingly it lies at the same distance from the sun as the Earth and has the same good chances of supporting life. It’s position makes it difficult for us to reach. As to how many moons it has, well we don’t know yet and will its inhabitants, if it has any, discover us before we discover them?