We are the moon.

[Ferret]

I didn't want to Hi-jack the other thread but I still wanted to persue the idea for a campaign. As the title said I was thinking of setting it on a moon, not a dry wastle land moon, but one with an earth like climate. But that doesn't matter.

I'd like to find out what kind of day, year or month would be had from such an arrangement. I'd of thought as Lunar eclipses are more common (Yes?) that the inhabitants would be in the dark a lot. What about at night? is there such a thing as a full planet? What would tides be like? What size would the planet have to be? Anything else I should be aware of.

 

[Crothian]

well, it wouldn't be a lunar eclipse since you are on the moon. it's the planet that is blocking the sun. WEll, how does the moon reotate around the planet? is it in the same plane linear to the planet and sun, or is it more perpendicular? depending how fast the moon and planet rotated would depend on lots of things like day and night......

 

[Shadowdancer]

Darn, I thought this thread was going to be a filk of "We are the World."

 

[barsoomcore]

We are the moon.

We are the people.

 

[Imret]

I'd like to find out what kind of day, year or month would be had from such an arrangement. I'd of thought as Lunar eclipses are more common (Yes?) that the inhabitants would be in the dark a lot. What about at night? is there such a thing as a full planet? What would tides be like? What size would the planet have to be? Anything else I should be aware of.

I think this math is tricky because it's unprecedented - we have no basis (as far as we're aware) on which to base a life-friendly moon orbiting a planet. But, having started this conversation with a couple of people, I have a few thoughts to work on for it. Incidentally, this is a very cool idea.

Days, months, years, those are all your call pretty much. You get to set rotational and revolutionary speed - if you want the moon to skim the planet's atmosphere once every hundred-odd years, that's your perogative. If it's forever winter, your call.

Huh. Sudden off-topic thought - might this explain the bizarre seasons of Westeros? It's actually a moon?

As far as planet size, that depends on the size of moon you want. Luna is actually a little large to be a moon orbiting a planet of our size, as a solar-system average. If it's orbiting something the size of say, Mars, the moon is fairly small, whereas Earth could rather easily orbit a gas giant..provided sufficient distance exists.

Tides would depend on if your orbit is circular or elliptical. A circular orbit would give very minimal tides, likely tied to the sunlight cycles (as one side of the planet is exposed to light, it turns away from the planet, and vice versa). An elliptical orbit would give far slower tides, possibly closer to seasonal, but they'd be fairly dramatic as the moon pulls closer to the planet and then farther away.

If I'm wrong on either of these, science-folk, do tell me. I know very little about planetary physics, but my logic is usually pretty good.

And a final thought...a gas giant would be the coolest moon in any night sky.

 

[Ao the Overkitty]

Ooooh. Visions of Escaflowne type deal, huh?

 

[Khayman]

Darn, I thought this thread was going to be a filk of "We are the World."

I thought it was going to be 'We Like The Moon' from rathergood.com --- probably for the best anyway. Those things are scary.

You might like to check out the world generation rules from Traveller & Megatraveller --- there's a program called Heaven & Earth that does some of the math for you, including generating maps & climate data.

Moons tend to be tidally locked to their mainworld, which means that you have one side always facing the world. There was a discussion of this on the Pyramid website over at Steve Jackson Games --- if you have a subscription check out the Omnicient Eye column's discussion of living on a gas giant's moon. I believe that it was from November 5 2004 or thereabouts.

 

[tarchon]

I think this math is tricky because it's unprecedented - we have no basis (as far as we're aware) on which to base a life-friendly moon orbiting a planet. But, having started this conversation with a couple of people, I have a few thoughts to work on for it. Incidentally, this is a very cool idea.

George Lucas certainly likes them.
It would be pretty difficult physically, but under the right circumstances largish moons like Ganymede and Titan could have decent atmospheres, at least fora while. The biggest problem with smaller worlds is keeping those light water molecules from wandering off into space. Earth has a little extra edge in that the structure of the atmosphere tends to trap water more efficently than just the gravity would do alone, and if you had a really good "cold trap," maybe a Ganymede-to-Marsish-sized body could hold some decent amount of non-ice water. The lower you keep the temp, the easier it is to do, like maybe a body with very frozen poles and a temperate equator. A really dense body would help as well, some late-generation star system, heavy-metal star, that sort of thing.
Or you can wave it off as magic.

 

[Khayman]

(...) If I'm wrong on either of these, science-folk, do tell me. I know very little about planetary physics, but my logic is usually pretty good.

I think that's basically correct. Tidal effects around a gas giant would be massive, though smaller satellites might escape this. Of course, smaller satellites might also have a low gravity --- unless something funky was going on to increase their density, such as having an abnormally high mass or the presence of festering gobs of magic at the planetary core. I am reminded here of Skoraeus Stonebones, god of the stone giants, living at the core of the world...

However, the biggest concerns are going to be (a) how much light/heat you're getting with that big planet blocking the view, (b) how much light/heat you're getting if you're too far out in the planetary system, and (c) how to survive if you're around a gas giant, as you will probably be stuck in a radiation belt. Again, solved by the usual agents of technology or magic.

Of course, radiation exposure might account for the Aberration subtype, and majestic flumphs might float gracefully in that gas giant in the sky...

 

[Khayman]

Just to run with tarchon's idea --- a watery moon with an extensive crust of ice, above which is a negligible (and cold) atmosphere. Captive cities underwater ruled over by kraken or morkoth, and captured human folk summoned in from elsewhere, trapped by the cold water and the pressure.

hmm, I'm feeling very Lovecraftian today...