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Is there a physics major on here willing to help me with a few things?

The Sigil said:

But the height of the tides is still right.

--The Sigil

I wonder what kind of stress that would put on a planet in formation. Would you even be able to form a planet under those circumstances? And tides that drastic.. would you have /any/ land for very long, assuming the ocean will erode things faster?
 

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I wonder what kind of stress that would put on a planet in formation. Would you even be able to form a planet under those circumstances? And tides that drastic.. would you have /any/ land for very long, assuming the ocean will erode things faster?

Pretty much the only way I see you having land is if there is not an awful lot of ocean to begin with. IOW, you won't have land with our earth's 2:1 water:land ratio. But if you had an world of mostly land, though, there likely wouldn't be enough water to sustain life.

As for stress on the planet, I imagine you're looking at a planet kind of like Jupiter's moon Io - the stretching and pulling causes near-constant volcanic eruption and earthquakes.

I suppose that is a way to keep land masses, though... if the stresses on the planet have the planet spewing out volcanic material faster than the tide can erode it away, you'll have land masses, though one surmises that the land wouldn't be a very hospitable place. In fact, I suppose that the "inhabitable" areas might well be places in the center of a ring of volcanoes... the volcanoes keep spewing out rock and lava to ward off the effects of erosion.

Very nasty climate, but I guess it's do-able (in theory).

OTOH, you would have no port cities and intercontinental travel would be done via flying. And all water would have to come from wells - no rivers, et al.

Overall, not a world where I'd want to live.

--The Sigil
 

sigil, you are talking about the second scenario, right?

would there be catastrophic changes from having double strength tides?
 


The only real solution to the tide problem is to lower the mass of the mars-sized moon. I guess you could have the mars-sized moon not be natural at all but actually an artifact of immense proportions, so that it's hollow. Then you could give it the mass of luna, so you'd have identical(near identical) tides to earth.

This has the side benefit of giving you a couple of easy adventures: have the PCs go to the moon, give them clues that it's an artifact, and then go from there. You could even have a "caretaker" figure(an immensly powerful being in control of the artifact) that ask the PCs for help.
 

Interesting book I found mentioned :

Comins, Neil F. What If the Moon Didn't Exist? Voyages to Earths that Might Have Been.
Synopsis: Ten essays on different Earths, five of which (see other entries by Comins) involve an altered early solar system.

Published: HarperCollins 1993 (0060168641) and HarperCollins 1995 (0060925566).


at Uchronia: The Alternate History List
 

The Sigil said:
As I review my answer, I think I missed on the timing of the tides... high tide is when the side of the earth you're on is closest to the moon (the moon pulls the water up) and low tide comes 12 hours later (when the moon pulls the water "down", being on the other side of the earth).

Hmmm, I'm pretty sure the period between high tides is 12 hours. This would mean that the side of the earth facaing the moon and the side of the earth facing away from the moon are experiencing high tide at the same time. Low tides would be occuring at perpendicular angles to this.

I wouldn't bet my life on it, but I would put down $10!:p
 

By the by, as I was looking over what it would take to compute tides rigorously, I found that the center of mass of the Earth-Moon system might be important, which is why I decided to forget about estimating tidal heights for the mars moon. I'm not sure what other consequences might arise, but it should be safe to say that the tidal forces are massive enough to increase tectonic activity globaly. Add lots of volcanoes and earthquakes and look to Japan's historical architecture for structural inspiration.
 

MadScientist said:


Hmmm, I'm pretty sure the period between high tides is 12 hours. This would mean that the side of the earth facaing the moon and the side of the earth facing away from the moon are experiencing high tide at the same time. Low tides would be occuring at perpendicular angles to this.

I wouldn't bet my life on it, but I would put down $10!:p

Go ahead and bet your life on it. Isn't that what Mad Scientists do anyway?

Yes, Sigil was right the first time about the tides. High tide occurs on opposite sides of the planet at the same time. That's what tides are after all: One side of an object being pulled toward an orbiting mass while the other side is being flung away from it.

I'd like to second the books recommended in this thread. The Larry Niven - Known Space books are very fun. WayneLigon left out mentioning the planet Canyon which is pretty much the opposite of Mount Lookatthat. The only habitable area on Canyon is a gigantic canyon that is low enough down to make the atmosphere breathable. The people live on the walls of the canyon in apartments carved into the rock.

Larry Niven is my favorite author and he even has a tie in with WotC. There's a Magic: The Gathering card called Nevinyrral's Disk named for a magical item from one of his other books.

The Kim Stanley Robinson - Mars books are also an interesting read although they spend much more time on character development and less on physics than the Niven books do.
 

Rel said:


WayneLigon left out mentioning the planet Canyon which is pretty much the opposite of Mount Lookatthat. The only habitable area on Canyon is a gigantic canyon that is low enough down to make the atmosphere breathable. The people live on the walls of the canyon in apartments carved into the rock.

I also left out We Made It. We Made It's poles line up with it's primary during spring and fall, making the planet temporarily as if it were tidal-locked; ie, it has one face to the sun. Atmosphere on the day side tries to boil off, atmosphere on the night side tries to condense to liquid; tremendous 1500+ mph winds result.
 

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