On Creating Imaginary Worlds: Science Fiction

[iansales]

If it's not a silly question, why go to all that trouble for a fantasy world? Most are set in cod-Mediaeval Earth-like worlds; the actual planetology is irrelevant. It's only really important if you're writing sf - and some detail of the world is important to the story.

[Culhwch]

I'm not sure I'd call throwing something together from rudimentary knowledge and then double-checking my (wrong) theorems on an internet forum a lot of trouble, Ian... It was truly a curiosity thing, to see if I'd got it entirely wrong, or just a little wrong, and to try and lend some credibility for those readers who would go, 'Hey, that's not possible, this guy's a tool.' As I said, I like the idea, and it adds to the milieu, so I'm gonna keep it. I figure if Martin can have seasons that last years, I can do this.

[Anthony G Williams]

Originally Posted by Leisha

No idea about mathmatics, Dustin, but I thought I'd post these here and make us all feel humble (might help with the planning of worlds in somebody's novel).

Terrific images, Leisha, thanks for posting them.

[Teresa Edgerton]

Supposing the world was a very large moon orbiting around a super giant planet? The tilt would be in relation to the planet rather than the sun, wouldn't it? What would the seasons be like then? I'm imagining not at all the same as our seasons relative to the year. The part where the world orbits around to the side opposite the sun would be a long, cold eclipse, wouldn't it? (Although whether this could result in a situation like the one Culhwch is describing is beyond my powers to visualize.)

And why do it for a fantasy novel? Because it could have a significant impact on the plot -- it could be the thing that generates the plot. Seasons are a very big deal in a pre-industrial world. Seasons can be life and death. Not to mention the part that seasonal or planetary cycles can play in religion. I can imagine people killing each other over calendar issues; I can imagine it far too easily.

[dustinzgirl]

Originally Posted by Green

Have a read of Hyperspace, by Michio Kaku.


It deals with the science of extra dimensions and discusses what extra-dimensional "beings," or at least those with access to the extra dimensions, would make of the world, and how they would manifest to us. One of the best pop-science books I've ever read

Wow that does look like a great book! And Amazon, always thinking about me, gave me a whole list of books I've never even heard of along the same lines. Coolness.

I'm one of those that knows just enough about the subject to be dangerous when I write, but not enough to be good.

[lin robinson]

2) Planets orbiting in a figure of eight around both stars? i

s highly unlikely. The gravitational stresses of such an orbit would almost certainly preclude it; the point at which the stellar gravitational attractions would meet would tend to a) prevent planets from forming in the first place or, in the highly unlikely event of such forming (or a "rogue planet" -- should such exist -- being captured), b) cause such tidal stresses that the body would break apart.

The big factor here, I would think, it would require the stars to be in constant position relative to each other. Which would pretty much mean rotating around each other. This would tend to create nodes between them, making mass hang at such points rather than spinning within the spinning. It seems to me.
There's a double sun shot in Star Wars that always got me wondering how the hell that would work.

Two moons is a piece of cake. Same deal as planets. What about satellites around moons? If Titan is earth-sized, why can't it have a moon?

[chrispenycate]

The two stars (and everything else in the system, for that matter) would be rotating round the centre of gravity of the system (more or less the centre of gravity of the two stars.
If the stars are of aproximately equal mass, the centre would be roughly halfway between them, and a stable planetary orbit in the inner space is highly unlikely, so habitable planets would be a good distance further out.
If they are of wildly different masses, the centre of gravity woud be more or less within the larger star, and inhabitable planets could form inside or outside the orbit of the smaller star (imagine Jupiter in fusion, with its moons a secondary planetary system. If the smaller star were cool enough, you could have a second planet in the system inhabitable by the same organisms.
Of course, we won't know the probability of all this till someone goes to have a good long look.

The problem with moons around moons is long term stability; peturbation from the mother planet, from the primary, from other moons, will tend to make Lagrange points, trojan points the final resting place, rather than nice epicycles,

[JDP]

Originally Posted by Teresa Edgerton

I'm imagining not at all the same as our seasons relative to the year. The part where the world orbits around to the side opposite the sun would be a long, cold eclipse, wouldn't it?...

...And why do it for a fantasy novel? Because it could have a significant impact on the plot -- it could be the thing that generates the plot.

For example, the premise of Brian Aldiss's Helliconia novels. They're based around long, epochal seasons aren't they? Can't remember the astronomical reason why though.

[lin robinson]

That would be one real bitch about the figure eight orbit. Summers with no night anywhere. (Worse than Alaska :-)

[Birol]

What I'm remembering with this talk of seasons is a short story by Asimov, where the three suspects in a crime all lived on a planet with a different night-day cycle. How they viewed night-day was the major clue in discovering whodunit.

[lin robinson]

I seem to remember one (from the "Known Space" series? the Puppeteers?) where a guy figured out a race was from a planet with no moon because they didn't understand tides. (And therefore didn't understand why a guy got his head ripped off by gravitational forces in an orbitting craft)

[thecommabandit]

Originally Posted by Teresa Edgerton

Supposing the world was a very large moon orbiting around a super giant planet? The tilt would be in relation to the planet rather than the sun, wouldn't it? What would the seasons be like then? I'm imagining not at all the same as our seasons relative to the year. The part where the world orbits around to the side opposite the sun would be a long, cold eclipse, wouldn't it? (Although whether this could result in a situation like the one Culhwch is describing is beyond my powers to visualize.)

And why do it for a fantasy novel? Because it could have a significant impact on the plot -- it could be the thing that generates the plot. Seasons are a very big deal in a pre-industrial world. Seasons can be life and death. Not to mention the part that seasonal or planetary cycles can play in religion. I can imagine people killing each other over calendar issues; I can imagine it far too easily.

In fact, the main fantasy setting I write in all takes place on a moon orbiting a gas giant. On this world, they count the passing of a month by the amount of time taken for the moon to orbit its parent planet. And I thought about the eclipse part quite a bit, having a GCSE in astronomy (*brag*) I can say that an eclipse would only occur when the planet is 'full' and rests on the ecliptic. But the fact that the planet is a hell of a lot bigger than the sun from the observer's view means that eclipses are more likely, and maybe even occur every month like clockwork. On the other hand, the fact that the moon orbits around quite a distance from the planet would mean that the ecliptic wouldn't be a simple straight line, but would look more like a planet's trail, going through retrograde motion every so often, which may lower the chance of an eclipse occurring every month. Also, if the moon was orbiting far enough away from the planet and not around it's equator, then it may only briefly pass through the penumbra giving them a week or so of rather chilly and dark weather rather than slogging through the umbra and freezing the moon.

The way I've got around this is by giving the moon are rather oddly placed orbit; rather than orbiting close to the planet's equator or the star's orbital plane, its orbit is on its way towards a polar one. This evades the problem of the planet causing a chilly eclipse for half a month, every month and and in combination with a ring system also provides a spectacular meteor shower twice monthly

Oh, and to put those funky pictures in a bit of perspective: see how big the sun is compared with us? Well, the distance between the edge of the sun and us can hold 100 suns chromosphere-to-chromosphere. Huge, innit?

[Marvolo]

Originally Posted by j. d. worthington

Mosaix: Chris would be the one to know the more recent scientific ideas on this, but I'll take a stab at it. From my reading (admittedly several years ago), I'd say that:



Is possible, depending on how far apart the stars are. In fact, I posted a thread the other day, where they have figured out how far apart they need to be in order for the preplanetary disc to form into planetary bodies.



is highly unlikely. The gravitational stresses of such an orbit would almost certainly preclude it; the point at which the stellar gravitational attractions would meet would tend to a) prevent planets from forming in the first place or, in the highly unlikely event of such forming (or a "rogue planet" -- should such exist -- being captured), b) cause such tidal stresses that the body would break apart.



Depends on what you mean here. An oblong shape (like most race-tracks, for instance) is very unlikely, because the gravitational stresses mentioned above, where the forces of the two stars combine, would tend to tear such a body apart, should it ever have formed in the first place. On the other hand, an elliptical orbit similar to the solar system's, but enlarged to circle equidistantly from both stars, is -- again, from my understanding -- the most likely. This would be at such a distance that the disc of dust would be able to form a stable body to begin with, and where the gravity from the stars would jointly stabilize (more or less) a planetary (or series of planetary) orbit(s).



That one is also highly unlikely. The gravitational and rotational stresses applied by such would be almost certain to pull any sort of body apart, from a rocky planet to a gas giant to a smaller star -- or even one larger but less dense.

Also... don't forget that there are apparently systems which are quadruple and up, as well... These, I'd say, are unlikely to develop a planetary system... but the jury is still out on that one, I think. However, remember Asimov's "Nightfall", where the system had (as I recall) seven suns....

Let's also not forget we are dealing a universe of infinites here. In an infinite universe such a condition would exist, it would have too. Eventually, someone along the arc of infinity, such a system would come into being. The question, as I'm sure you know, is what sort of beings exist there? And why is there story worth a crap? That is the question with every story. Why is this worth telling?

[dustinzgirl]

Originally Posted by Marvolo

Let's also not forget we are dealing a universe of infinites here. In an infinite universe such a condition would exist, it would have too. Eventually, someone along the arc of infinity, such a system would come into being. The question, as I'm sure you know, is what sort of beings exist there? And why is there story worth a crap? That is the question with every story. Why is this worth telling?

I don't think there is an infinite universe, I think it has a beginning and an end that we just can't measure. I think infinite possibilities are not infinite either, just way to big for us to mathematically describe.

Why do I think this? Because our mathematically capability is constantly growing. In 1970, you couldn't even fathom a tetrabyte hard drive, but now you can buy them. So, by my estimation, 1,000,000 years from now we will have added up all the possibilities that were once considered infinite and the number will be something like:

goginfatetra possibilities in dimension xviii, multiverse # 199.

but even then, there will still be things we can't count, and those will be called infinite.

[lin robinson]

Let's also not forget we are dealing a universe of infinites here. In an infinite universe such a condition would exist, it would have too.

Not really. The magical powers of "infinite" are over-rated. Infinite monkeys wouldn't REALLY write all of Shakespeare. And there's not a square planet out there. Or another planet just like ours except the Cubs win world series.