Questions about the Firefly Universe
POSTED BY: Valdron
UPDATED: Sunday, November 20, 2005 21:19
VIEWED: 7518
PAGE 4 of 4
Thinking out loud a bit here, and working on the model of a multi-star system, the gas giants in remote jovian orbits probably get bounced around real hard and wind up even further out, pursuing really eccentric orbits and stripped of their moons.
Meanwhile, the distribution of big moons, mercury/earth sized bodies tends to wind up clustered around the suns. Probably a lot of bodies in the habitable belts.
Now, we tend to see Mars as the smallest Earth norm habitable body. But actually, Mercury, is a bit denser than Mars, and thus its surface gravity is almost the same as Mars. If you stuck Mercury in an orbit between Earth and Mars, there's odds are that it might actually be able to hold an atmosphere and a viable biosphere.
Of course, we don't know what it takes to hold a viable atmosphere. Normally, we'd default and say Earth is the optimum size.
But then we've got Venus with 90% of Earth's Gravity, and 90 times its atmospheric pressure. So, that suggests that an Earth-level gravity is more than sufficient to hold an Earth level atmosphere, substantially less may be needed.
Over on Mars, we've got plenty of indications that its atmosphere was once much more genial and Earthlike. So, this may represent the lower range.
The differences between Earth, Mars and Venus suggest in part, different approaches to the Greenhouse effect. Venus has way too much greenhouse going on too close to the sun, Mars has too little greenhouse too far from the sun.
So let's estimate that the range of world sizes that could be terraformed run from surface gravities of 35% and up, and diameters of about 3000 miles and up.
In our Solar System, there's Earth, Venus, Mars, Mercury, Titan, Ganymede and Callisto. We've also got a handful of 'also rans' in the form of Luna, Io, Europa and Triton. Or eleven bodies in all. Unfortunately, all but one are positioned really badly for Earth-type life, and only two are in a zone which might encourage us to even think about Terraforming.
But assuming that Serenity's system is a multi-star system, say four or five or six stars - Multiply Sol's 11 potential useable bodies, by the number of stars and you get something very close to the contingent of Planets given for the Serenity system.
Well, not quite. Earth's 'useable bodies' are on average, a fairly lightweight bunch. The Serenity worlds, particularly the smaller ones, would have to average out a lot denser.
Is this realistic.
Well, maybe it is. You see, Carbon, Gold, Iron, Uranium, all those heavier elements are probably not evenly distributed. Y'see, the most common element is Hydrogen, followed by Helium. Its the stuff that makes the stars themselves. In those star furnaces, fusion forges create the heavier elements from raw hydrogen. How does it get out into the Universe, into our pocket watches and our bodies? Very simple. Stars have to explode.
We are, all of us, made from the ashes of supernovas. Stars blowing themselves apart across half the universe, the dust of heavy elements being swept into new maelstroms, forming planets in the aftermath of the births of new stars.
I don't see any reason that this stuff should be distributed uniformly. So if the Serenity system is closer to a few supernovas, then expect it to be liberally gifted with heavier elements.
So the trick is to have so many habitable worlds crammed into habitable zones. How feasible is that.
Well, in our Solar System, three big ass heavy worlds, Earth-Moon and Venus come within 22 million miles of each other.
So if we assume a habitable zone roughly 70 million to 150 million miles wide for a star of our proportions (and it'll vary depending on the proportions and intensity of the star, but what the hell, we need a rule of thumb, and if we assume about 20 million miles reasonable separation is required for them all to maintain stable orbits, then we can pack five planet's of roughly Earth/Venus mass in relatively safely. That's pretty nice, but not quite good enough.
This is all seat of the pants stuff, s
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Just as a matter of scale our sun is a yellow dwarf. So, if you had a sun that was 10 times larger than ours you'd have a habitable zone 10 times larger.
Also as far as the time it takes for terra forming. Once you've terra formed the first world, there would be no reason you could not work on multiple worlds at the same time. A large portion of the terra forming process is biological; seeding the body with things like algae, bacteria. Once you've gotten the temperature up to the point where you've got liquid water, the plants will do the work for you.
Shiny, lets be bad guys
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[quote: Now, we tend to see Mars as the smallest Earth norm habitable body. But actually, Mercury, is a bit denser than Mars, and thus its surface gravity is almost the same as Mars. If you stuck Mercury in an orbit between Earth and Mars, there's odds are that it might actually be able to hold an atmosphere and a viable biosphere.]
Just another observation but, it's been speculated that; If you swapped the orbits of Mars & Venus both world might well be habitable. Mars is smaller with a thinner atmosphere, that would not soak up so much heat in an orbit closer to the sun. Venus is about the same size as the Earth with a thicker atmosphere, that could hold in the heat at the outer edge of the habitable zone.
Shiny, lets be bad guys
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Most science fiction movies/shows/books are not only completely inconsistent with reality but are also inconsistent internally. Ships in Star Wars, Star Trek, and Stargate move at the speed of the plot. Hulls of Star Wars ships are capable of withstanding weapons in the hundred gigaton range but get smashed up by tiny fighters colliding with them. Weapon power within all those shows are all extremely inconsistent, one minute they’re in the gigaton range another they’re about as powerful as a WW1 artillery cannon. There are maybe 10 sci-fi movies and shows that are somewhat consistent with reality as well as consistent internally, the best one being 2001, the first Terminator is up there as well.
"I swallowed a bug." -River Tam
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Quote:
Originally posted by Stillwaters:
Just as a matter of scale our sun is a yellow dwarf. So, if you had a sun that was 10 times larger than ours you'd have a habitable zone 10 times larger.
Not necessarily. This gets us into areas of quirky astrophysics but the larger stars are not necessarily more massive. Often larger stars are older ones whose cooling has allowed them to grow.
I believe that for our type of yellow star, there's an upper limit of about six times the suns mass. After that, physics produces a different kind of star and a different kind of stellar history.
Still, I think you are correct in that a more massive and more energetic yellow star would produce a larger habitable zone.
Quote:
Also as far as the time it takes for terra forming. Once you've terra formed the first world, there would be no reason you could not work on multiple worlds at the same time. A large portion of the terra forming process is biological; seeding the body with things like algae, bacteria. Once you've gotten the temperature up to the point where you've got liquid water, the plants will do the work for you.
Well, the key thing is water and jiggering a correct temperature.
Mars is practically a gimme, because it's apparently got useful water and carbon dioxide locked up at the poles. Hell, right now, the Martian ice caps seem to be losing more carbon dioxide ice to the atmosphere each year. This is an ongoing thing, rather than seasonal. Mars is apparently entering a warm phase. So it's almost as if Mars is terraforming itself.
The question will be if Mars has enough water and carbon dioxide to build up an atmosphere comfortable for us.
On the other side of the coin, Venus has way too much atmosphere and absolutely no water. So terraforming Venus is trickier.
Of course, we're sitting here trying to figure out how to terraform Mars and Venus from our privileged position on Earth.
Isaac Asimov wrote a story called 'The Martian Way' in which his Martian colonists went all the way out to Saturn's rings to harvest icebergs to restore water to their new planet.
But, if you're coming into a planetary system from outer space, that changes things. The first place you're going to be is the Oort Cloud (the halo of comets and ice in deep space beyond the farthest planet).
There's a theory which holds that Earth's oceans are actually from outer space. That our water comes to us from comets.
Well, if this is the case, and we're passing through the cometary region to get to the Serenity worlds, it strikes me that it may be simple enough to harvest those comets, perturbing their orbits and piloting them in to crash into the inner worlds. It would be messy, but you could ensure for each world, in a fairly brutal fashion a starting supply of water and cometary elements such as oxygen, carbon, hydrogen, etc.
The Oort cloud gives you all the ice and volatiles you're going to need, and you're going to be passing through anyway...
You could even manage the impacts and chemistries, if you wanted to thin out too heavy atmospheres, or thicken them up, slow down or speed up greenhouse processes.
Assuming that you've got the technology to fly through interstellar space, shake and bake technology for a bunch of worlds that are already showing the right characteristics should be accessible.
Some worlds will take fast and be easy, some will be slow. But you could do the initial set ups pretty easy.
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Quote:This is probably the most likely way in which that many habitable bodies could be in a single system. The habitable zones of most stars are probably not large enough to hold that many planets, but gas giants offer the possibility of extending habitable planets, not only packing them into smaller local groups but also providing them with heat. A gas giant’s gravity can cause considerable strain on moons that could keep a planet warm well beyond the sun’s ability to heat it. Light would still be a problem, as from that distance the sun might be very dim. We have gas giant moons in our solar system with atmospheres and considerable internal heating and possibly water oceans. Life would be very different on these planets and one imagines nothing like the sunny American West, but certainly if you’re looking for habitable planets outside of a stars habitable zone, gas giants are probably your best bet.
Originally posted by TheRealMe:
One possible way to make this work is to have planet-sized moons orbiting superjovian planets in the habitable zone. You might get a bunch of those. Many folks have argued that "moons" are too small, but the definition of a moon is a body that orbits another non-sun body. A moon could be the size of the Earth, for example.
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Qui desiderat pacem praeparet bellum.
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But the jovians could be IN the habitable zone as well
TheRealMe, First Officer of the Sereni-Tree
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Quote:Maybe. Maybe not. It depends a lot on our understanding of stellar dynamics. There is something called the T-Tauri phase in a stars evolutions, actually it’s a phase that occurs prior to the stellar formation. You can think of it as an explosion that occurs as a result of the last stages of collapse, accretion and subsequent ignition. During this phase the star radiates huge volumes of very high velocity wind. It's thought that all of the planets in our solar system may have at one time been gas giants, but following this T-Tauri phase the atmospheres of the inner planets where striped away. I don’t know how close a gas giant can form to a star or how far out the habitable zone can extend. So I don’t know for sure if a gas giant could exist in the habitable zone.
Originally posted by TheRealMe:
But the jovians could be IN the habitable zone as well.
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Qui desiderat pacem praeparet bellum.
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This stuff about habitable zones is really a red herring IMHO. It refers to what could be habitable barring technological intervention. With sufficient technology, a giant frozen dog turd in deep space could be made habitable.
There are people on earth today who live in frozen wastelands, barren deserts, and under the ocean's crushing depths, none of which would generally be considered 'habitable' places. Apply technology on a sufficient scale, and you could set up shop pretty much anywhere you want.
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