Planets with two moons

Werewolves.

Jane Yolen has a series (starts with Heart's Blood, I think) where the planet has two moons and she uses them to interesting effect.

Bah, we don't need more werewolf stories right now hehe

I'm no astronomy expert, but depending on the size and distance of the moons relative to the planet, it would affect certain things such as length of day, tides (probably be bad unless they're on opposite ends of the planet). The time it takes to rotate would probably be longer too with three forces acting on the planet (the sun and 2 moons), so that would mean longer days and nights.

If you want some "cheap cop-out" fixes, just have non-major events happen at night, or else give your characters "enhanced night vision" (like a cat for example, although cats can't see in total darkness either, they do have much better vision in low light conditions than humans) or just straight up night vision goggles (I figure if you have spaceships, then they probably have decent enough technology for NVG's).

Or you could just give your characters echolocation ability (kinda like bats, sorry, dont remember what it's called specifically if it's not that).

Some more "fantasy" based ideas would be a small circle of light that goes around your characters, a light spell that illuminates them (kind of like carrying around a lamp, it would let you see a few feet ahead, but would also make you stick out like a sore thumb) or just suck it up and make them carry torches (and if you're creative, you'll make them run out of a light source at a key point in the story hehe).

Point is, make up something cool. Two moons may not necessarily be better for "light source", so if you can come up with some alternatives (that aren't too terribly far fetched anyway, like infinite supply of flares for example), especially ones where you can work in the light problem as causing problems for the protagonist (and possibly antagonist too), then it'll make the story more interesting to read.

That's going to make for one complicated calendar. Earth months were originally based on the phases of the moon. Still are, in some cultures. Imagine what sort of calendar a two-moon planet would have if the society is native to that planet!

Some more esoteric moon notes: Earth's moon is pretty big by moon standards. On the other hand, some astronomers and physicists have theorized that a big moon is useful for making a planet that can sustain life. Unfortunately, I can't remember the arguements at this point.

If the moons are both very large, I wouldn't put them too close to each other. They might interfere with each others' orbits and collide if they are at close to the same altitude in the same stretch of sky. If they orbit at the same altitude but on opposite sides of the planet, that just seems like a little too much coincedence to me. So you might want to put them at different distances from the planet, which would give you orbits that take different amounts of time. One might orbit the planet in 19 days and the other in 32. Remember, the closer to the planet, the faster it moves.

MadScientistMatt said:

Some more esoteric moon notes: Earth's moon is pretty big by moon standards. On the other hand, some astronomers and physicists have theorized that a big moon is useful for making a planet that can sustain life.

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I'm pretty sure it's because of the extreme tidal forces imposed on the oceans of Earth and the resulting wet-dry cycle. A good example of how this works are wooden fence posts. Typically, they rot just at the point where they meet the ground, but those portions that are always dry or always wet take much longer to decay. The wet-dry interface is ideal for micro-organisms.

If the moons are both very large, I wouldn't put them too close to each other. They might interfere with each others' orbits and collide if they are at close to the same altitude in the same stretch of sky. If they orbit at the same altitude but on opposite sides of the planet, that just seems like a little too much coincedence to me. So you might want to put them at different distances from the planet, which would give you orbits that take different amounts of time. One might orbit the planet in 19 days and the other in 32. Remember, the closer to the planet, the faster it moves.

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A planet with two moons the size of Luna would be most unstable. Even the two moons of Mars, because they're so close to the planet, are doomed.

In any two-body orbital system, such as Earth/Sun, or Luna/Earth, there are five points of stability called Lagrange points. In large body systems, such as Jupiter/Sun, there are indeed small 'moons' positioned at the L4 and L5 Lagrange points. The key word is "small." Introduce a large body into a stable two-body orbital system and things go haywire in a hurry. Those who want to read the nitty gritty, go here.

Here's a super site for novelists on how to base science fiction on science fact.



It's an interesting read!

http://www.phy6.org/stargaze/Sintro.htm

Effects on Animals

Don't forget the effect of the moon cycle on the animal kingdom. Everything from when they mate to when they migrate, and their changes in behavior.

And that applies to the human animal, too. The "Lunatic Phenomenon" in true life, for instance, where hospitals and police report increased violence on nights with full moons. And moon phase is said to affect menstrual periods, too. Can you imagine "that time of the month" happening twice as often? And what if both moons are full at the same time?

maybe it would make sense if your earth was ten times the size it was now or sized in such a way that you'd *have* to have two or more moons for tides and though you'd still have a 30 day-ish moon 'cycle,' they wouldn't be the same moon?

maybe that's crazy, but there are natural sources of illumination you can use. if i recall, there's a kind of fungus or moss that gives off light. you might not find them walking in the woods in your backyard as i think they're more a cave thing, but the point is you should be able to concoct a light alternative given some research and a little creativity. perhaps some plant that uses light as a defense, so when shuddered properly, an experienced woodsperson could effectively light his way.

i'm probably like most readers in that if i read a story with two moons, i might not know what would happen, though i'd raise an eyebrow. i think it would have to have some explanation. for a script, not so much, but for a sci-fi story, yeah, i'd like a little background on how that works just so i know the author put a little thought into it.

this one is about light:

http://micro.magnet.fsu.edu/primer/lightandcolor/lightsourcesintro.html

there's a mention of some bioluminescent sources there. don't know if that helps or is even interesting. personally, i think it would be cool to concoct up a bush that glows when you disrupt it. or moss or something. then again i'd probably just have them use lights on their caps, or, as mentioned, them having developed a certain kind of night vision.

How about creating another dimension that occurs at certain periods of time, where all natural colors are shades of dark blue and gray, yet the characters can still see their surroundings?

Having two moons in your story and its effects...? It depends on how much detail and research you want to do. As you said, sure, it will effect the tides, but tides really effect coastlines. You may have a series of landmasses that have very sharp, severe cliffs due to the severity of the tides. Your world could have more earthquakes due to the gravitational stresses placed on the plate tectonics beneath the surface. If the moons are along the same plane (near the equator perhaps), the world itself may not be truly "round" (our earth is actually elliptical due to its spinning). Weather patterns would not be the same as "earth" due to the harsher, more mountainous world that would be created by these gravitational forces...etc.etc.etc...

Now take it the next step...if the coastlines are primarily cliffs - how does that effect ships and shipping? Would the country that actually has a seaport suddenly become the major power of your world?

Stresses on the plate tectonics not only cause earthquakes, but also volcanic activity. You could really have fun coming up with a very violent world that suffers because of its two moons...

Or, you could just simply write that the twin moons glimmering brightly in the night sky gave so-and-so enough light to do what he or she needed to do at night without an external lightsource.

Have fun writing - and good luck!

This thread has some good info. I'm making a planet with two moons because I want it to be unearthlike and that was the first thing I thought of.