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SF ideas - Planetary Physics

athon

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Hey folks,

I've been playing around with some ideas over the past few years on a sci-fi story set on a unique planet. It's always going to be one of those 'works in progress', I fear, but I have written a couple of short stories set in this society. If it's ever going to become something more, I need to develop more aspects of this world.

One idea I want to pursue is having the planet tidal locked between two stars in a binary system. The side facing the larger star (which needn't be all that big - the size of our sun's fine) is dessicated and insufferably hot. The other side faces a smaller star which gives it enough heat, but the light is more like a bright twilight than anything. The atmosphere on the far side is hot, humid, and the environment swamp-like. The evaporated moisture from the other side of the planet falls as rain here. So I need to know if air-cells could move this way, pushing air from the hot side to the 'cold' side, dumping the moisture, before returning to the hot side.

I was wondering how feasible all of this is (i.e., how much suspension of disbelief is there?). I was wanting to have this an imperfect lock, where there exists an extremely slow rotation that sees the swamp dry up on one terminus and gradually increases on the other over hundreds of years. Could this be accomplished by the yearly interaction of another orbiting planet, by any chance? Say, an elliptical orbit of some other planet interfering?

The science here doesn't have to be entirely airtight, but it does have to be mechanically sound.

As far as my physics goes, it's not entirely outlandish. But if there is some massive flaw in the science, could somebody show me? Hell, give me some ideas for the story, if you like. If I like it, I might even use it. Already I want to use the misconcept of a woman's period being linked to a lunar month - imagine one period a year, linked with a single month of fertility (hence the appearance of a planet once a year). Mardi-gras anyone?

Athon
 
I don't know enough to answer your questions Athon, so I'll just post my own sci-fi planet problem.

I imagine a double planet. Two similarly sized planets having a "earth-moon" like relationship. 1 is heavy because it got all the metal, one is lighter because it didn't. So the light one orbits the heavy one. But both have atmosphere and support life.

I figure the distance between the 2 would have to be greater than the earth and moon to keep the lighter one from just colliding with the heavier. The orbit wouldn't be as stable as the Earth's because of the size of the lighter planet.

Of course, this is just the plot devise to get the humans on the heavier planet to visit the other one and discover the intelligent dinosaurs living there so maybe it doesn't need to be very scientifically accurate.
 
athon said:
One idea I want to pursue is having the planet tidal locked between two stars in a binary system. The side facing the larger star (which needn't be all that big - the size of our sun's fine) is dessicated and insufferably hot. The other side faces a smaller star which gives it enough heat, but the light is more like a bright twilight than anything. The atmosphere on the far side is hot, humid, and the environment swamp-like. The evaporated moisture from the other side of the planet falls as rain here. So I need to know if air-cells could move this way, pushing air from the hot side to the 'cold' side, dumping the moisture, before returning to the hot side.
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Jack of Shadows, by Roger Zelazny.

It's not the same scenario as you describe, but it's a similar concept and it's a cracking story, it would be well worth a read.

I don't know the answer to your question about the direction of the rainfall, but I'm sure someone will.

By the way, many species of animal have relatively short breeding seasons, so although there's a number of oestrus cycles involved, everything is concentrated in a few weeks. Dogs, on the other hand - bitches only cycle twice a year. However, the timing is fairly random, so there isn't a "breeding season" when all of them are in heat at once.

Rolfe.
 
Hexxenhammer said:
I don't know enough to answer your questions Athon, so I'll just post my own sci-fi planet problem.

I imagine a double planet. Two similarly sized planets having a "earth-moon" like relationship. 1 is heavy because it got all the metal, one is lighter because it didn't. So the light one orbits the heavy one. But both have atmosphere and support life.

I figure the distance between the 2 would have to be greater than the earth and moon to keep the lighter one from just colliding with the heavier. The orbit wouldn't be as stable as the Earth's because of the size of the lighter planet.
Click to expand...

The actual size of the planets wouldn't be an issue, really, as once you get outside the atmosphere you can treat them as point masses from an orbital mechanics point of view.

The problem would be that the gravity on the surface of the lighter planet would be much lower than that of the more massive neighbour, and so the atmosphere would be much lower pressure.

Hexxenhammer said:
Of course, this is just the plot devise to get the humans on the heavier planet to visit the other one and discover the intelligent dinosaurs living there so maybe it doesn't need to be very scientifically accurate.
Click to expand...

"The Ragged Astronauts" by Bob Shaw has something a bit like this - although the catch in his book is that both planets are similar size and mass, and are close enough to each other to - just - share an atmosphere. Consequently it's possible to balloon between the planets.
 
Re: Re: SF ideas - Planetary Physics

Rolfe said:
Jack of Shadows, by Roger Zelazny.

It's not the same scenario as you describe, but it's a similar concept and it's a cracking story, it would be well worth a read.

I don't know the answer to your question about the direction of the rainfall, but I'm sure someone will.

By the way, many species of animal have relatively short breeding seasons, so although there's a number of oestrus cycles involved, everything is concentrated in a few weeks. Dogs, on the other hand - bitches only cycle twice a year. However, the timing is fairly random, so there isn't a "breeding season" when all of them are in heat at once.

Rolfe.
Click to expand...

Excellent - thanks for the reading tip.

The whole breeding cycle thing needn't be actually reliant on the coming of the planet. It's based on the fact that the humans have been engineered to suit the planet, and one of the misinterpreted pieces of engineering associates lunar month with fertility. I used it as the basis of a short story I once did, and I was thinking of cannablising the idea for a novel, but I'm not entirely sure it will gel with the overall concept. Afterall, surely a technology advanced enough wouldn't get something so basic wrong.

Then again...

Athon
 
Seems like a cool idea. I know nothing about meteorology but if my brain's on straight there would be a permanent "storm zone" at the border of the two extremes. I'm not sure how that would work but I would think that the "cells" would revolve perpendicular to the planet around the "zone " boundry . Any successful model would have to define the planets size and the depth and density of the atmosphere. There would probably be a hellacious wind system as the two extremes tried to balance themselves out...I would appeal to authority either a meteorologist or an expert in fluid dynamics ( I believe Voricity is one ). There is free atmospheric software available off the net EX. http://www.src.com/calpuff/calpuff1.htm

Rotation can be almost completely arbitrary without having to model a complex satellite orbit mechanism after all while Earth and Mars have a day ( axial rotation ) ~ 24 hrs, Jupiter is 10 hrs. and Murcury is 60 or so days.
 
Matabiri said:
"The Ragged Astronauts" by Bob Shaw has something a bit like this - although the catch in his book is that both planets are similar size and mass, and are close enough to each other to - just - share an atmosphere. Consequently it's possible to balloon between the planets.
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Crap! My original idea was something like this but I was going to use cool '30's style airplanes. I'll have to read that story.
 
Well I can't speak for the meteorology either, but I have some comments on the tidal locking. In order for the planet to be stuck between the two stars it would have to be at the stable L1 Lagrangian point, if it weren't it would either orbit one of the stars with a completely different period to the other star, or have a very complex orbit. However at the L1 position there is no net gravitational force from the two stars, so there would be no tidal locking.

TillEulenspiegel - although Earth and Mars aren't tidally locked Mercury is - its' orbital period is 1.5 times its' rotation period, and Venus has a longer rotation period than orbital period. The rotation periods of the gas giants are hard to measure and depend on whether or not you measure equatorially and to what depth in the atmosphere you delve!

Having said that I don't see any reason why such a setup would be impossible, so sod the celestial mechanics and go with it. It's certainly an very interesting idea.

Edit to add - this does of course mean that you could have your slow rotation with no problems!
 
There have been many science fiction stories with the premise of slow rotation, including one memorable one by Barry B. Longyear in which all life on a planet exists at the terminators. Two different kinds of intelligent life exists on the planet, but they have no knowledge of each other and evolved independently.

It's not exactly a new idea.
 
"TillEulenspiegel - although Earth and Mars aren't tidally locked Mercury is - its' orbital period is 1.5 times its' rotation period, and Venus has a longer rotation period than orbital period. The rotation periods of the gas giants are hard to measure and depend on whether or not you measure equatorially and to what depth in the atmosphere you delve!"


True that . As I mentioned the size and depth/composition of the atmosphere is critical to the behavior of the exchange of energies of the two sides of the planet and altho it seems extreme , it appearers to be within the realm acceptable science without the usual dodge of " Heisenberg compensator's" and other side steps. The plus side is it is fiction after all =)

PS Would love to see a real time model of the theoretical planet.
 
Wrath of the Swarm said:
There have been many science fiction stories with the premise of slow rotation, including one memorable one by Barry B. Longyear in which all life on a planet exists at the terminators. Two different kinds of intelligent life exists on the planet, but they have no knowledge of each other and evolved independently.

It's not exactly a new idea.
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Hey, I fully agree. I love the sort of 'same planet, different world' aspect of novels such as Brian Aldiss' Heliconia series. The trick is to use the idea, but not as a focus for the story. It's more background - something different to having a boring old earth-like planet. Being more biology trained, I'm having fun with that aspect of the planet (I'm looking at having thermotrophs - something not entirely possible by our standards, but not impossible with some imagination).

Till', thanks for the advice. I'm aware of the Lagrange point, and figured this would be a problem on account of the gravity. The problem was with having a single sun - the other side would be freezing, regardless of the atmosphere. And I don't want a Terminator-only ecosystem - I'd rather the entire 'nightside' be used (imagine no concept of day and night, if you will). Even a small sun would be something, but if the orbits were out then most of the year would again be in darkness. That leaves me with either a planet at Lagrange which just happens to have a day=year orbit, or a tidal-locked planet which just so happens to have its year equalling the second sun's.

More thought is needed, obviously, but at least I'm on the right track.

Athon
 
You might also be interested in reading "Rocheworld" (also published as "Flight of the Dragonfly") by Robert L Forward. Two planets (one ocean, one rocky) spinning around each other like an eggbeater and the human team that explores them. Unlike a lot of writing, Robert Forward was a legit scientist. He's the guy that introduced Niven and Pournelle to the light sail idea.
 
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