Hurry up before you are the last one to see it.
Early in the film, a character states that without the rebreather mask, you are "unconscious in 20 seconds, dead in 4 minutes".Yep, probably!
impossible planets
- Thread starter Gotham Central
- Start date
Hurry up before you are the last one to see it.
Early in the film, a character states that without the rebreather mask, you are "unconscious in 20 seconds, dead in 4 minutes".
Ahh, cool. So it is CO2. Sounds like they did their homework where a lot of the science is concerned, though other elements are clearly fanciful.
That doesn't add up. The mass figure is what you'd get if the planet's density were exactly equal to Earth's, but that would give a gravity of 0.897. To get 0.8 gravity with that diameter, the mass would have to be 0.644 of Earth's.
Unless that "unobtainium" is reducing the gravity. Although I gather the levitation of the mountains in the film is more a sort of superconducting maglev effect, which shouldn't influence gravity per se. (They should've called it "upsidaisium" instead.)
Okay, CO2's reasonable--I'd forgotten that in large quantities it's toxic, which explains why a CO2 scrubbing mask would be sufficient for protection. Does CO2 make that wavy effect, though?
At any rate, I was probably overly harsh because so much of the other ecological stuff on Pandora is so bonkers.
That said, is a 20% CO2 atmosphere really consistent with the size of the biosphere on Pandora? CO2 levels on Earth haven't exceeded seven percent even under the most enthusiastic models since the Cambrian. Then again, it's believable, since Pandora probably experiences major volcanic outgassing due to its proximity to Polyphemus and maybe only a biosphere could keep the CO2 levels even that low.
Additionally, it could be a feeback thing--if the CO2 level drops, temperatures drop, and ensuing green dieback and fires returns CO2 to the atmosphere. Afaik, we don't know the distance from Polyphemus to Alpha Centauri A, but with the apparent decent temperatures and that concentration of CO2, presumably pretty far.
One thing, not really planetary ecology related, but since I brought up Avatar and got good answers, I figure I'll ask here--the film states that the Na'vi have fullerenes for bones. Is there a plausible biological process that can make carbon nanotubes? My understanding is that their industrial production involves severe electric arcs and/or extremely high local temperatures. Less of an objection, but important to note, is that they are extremely cytotoxic (cell-destroying). If there is a plausible biological process, why am I walking around like a chump with my calcium phosphate skeleton?
Sure, hence the qualifier "that we can see."
Indeed, I wonder if free-standing terrestrial origins are rarer than life on moons. If the proponents are right, in this solar system there would be three or more lunar environments with life compared to only one. The advent of warm Jupiters only makes it more likely that really interesting complex life such as on Pandora (well not exactly like Pandora
) or, say, Andor, will be common on sub-Earths.
At any rate, I was probably overly harsh because so much of the other ecological stuff on Pandora is so bonkers.
That said, is a 20% CO2 atmosphere really consistent with the size of the biosphere on Pandora? CO2 levels on Earth haven't exceeded seven percent even under the most enthusiastic models since the Cambrian. Then again, it's believable, since Pandora probably experiences major volcanic outgassing due to its proximity to Polyphemus and maybe only a biosphere could keep the CO2 levels even that low.
Additionally, it could be a feeback thing--if the CO2 level drops, temperatures drop, and ensuing green dieback and fires returns CO2 to the atmosphere. Afaik, we don't know the distance from Polyphemus to Alpha Centauri A, but with the apparent decent temperatures and that concentration of CO2, presumably pretty far.
One thing, not really planetary ecology related, but since I brought up Avatar and got good answers, I figure I'll ask here--the film states that the Na'vi have fullerenes for bones. Is there a plausible biological process that can make carbon nanotubes? My understanding is that their industrial production involves severe electric arcs and/or extremely high local temperatures. Less of an objection, but important to note, is that they are extremely cytotoxic (cell-destroying). If there is a plausible biological process, why am I walking around like a chump with my calcium phosphate skeleton?
Christopher said:
Sure, hence the qualifier "that we can see."
And the qualifier "under their own weight."
Indeed, I wonder if free-standing terrestrial origins are rarer than life on moons. If the proponents are right, in this solar system there would be three or more lunar environments with life compared to only one. The advent of warm Jupiters only makes it more likely that really interesting complex life such as on Pandora (well not exactly like Pandora
) or, say, Andor, will be common on sub-Earths.
I can't add anything to that analysis. Except to point out that the existence of giant planets in the Alpha Centauri system has already been pretty much ruled out by observation, so Polyphemus could only exist in fiction.
One thing, not really planetary ecology related, but since I brought up Avatar and got good answers, I figure I'll ask here--the film states that the Na'vi have fullerenes for bones. Is there a plausible biological process that can make carbon nanotubes? My understanding is that their industrial production involves severe electric arcs and/or extremely high local temperatures. Less of an objection, but important to note, is that they are extremely cytotoxic (cell-destroying). If there is a plausible biological process, why am I walking around like a chump with my calcium phosphate skeleton?
Hmm, that does sound kind of dodgy. I don't think there is a biological process that could do that, nothing we know of, anyway.
As for the cytotoxicity, that's believed to be a result of the small size of the fibers, basically the same reason asbestos is toxic -- it tears up the cell walls, like tossing pins and needles into a box of water balloons. However, that might only be true of them in their "raw" state, if they're floating around free and you inhale them or something. If they're in longer strands or bound as part of a skeletal structure, I don't think they'd be as dangerous. It's just a matter of minimizing the loose pointy ends.
Indeed, I wonder if free-standing terrestrial origins are rarer than life on moons. If the proponents are right, in this solar system there would be three or more lunar environments with life compared to only one. The advent of warm Jupiters only makes it more likely that really interesting complex life such as on Pandora (well not exactly like Pandora
Well, life in general, maybe. But if you're looking for Earthlike environments -- complex life on the surface rather than in a subglacial ocean -- you'd need a body of a certain size for that, big enough to hold a substantial atmosphere. Some Jovian moons could be that big, but it's hard to say what percentage. And there do seem to be a lot of superterrestrial planets out there, which would help even the score, at least.
As has been mentioned in this thread already, if the planet has enough internal heat it might still work.
But it would be a constant darkness at the surface.
But it would be a constant darkness at the surface.
Yes. CO2 is only toxic in huge concentrations--maybe 3-5% for real toxicity--and with a sustained exposure. 20% would, perhaps, kill you more or less outright like in Avatar, but 10% would take some time. 5% would take a relatively long time. By contrast, normal atmospheric content is 0.04% and it only gets to 1% in crowded rooms, where the major effect is a slight drowsiness. Scuba diving is the only normal activity I'm aware of where high CO2 concentrations are a major problem, and I don't scuba dive. I think other situations where CO2 concentration would become a factor (burning house, airtight room, etc.) would be deadly sooner through other mechanisms (CO-driven anoxemia and asphyxia respectively).
Also, it's not like you're unaware of it--it causes dizziness and headache. CO2 is pretty innocuous except in unlikely situations like that tragedy in Africa, where a whole village was wiped out by an upwell of CO2 from the adjoining lake (although even then, iirc it was asphyxia from the atmospheric O2 being pushed out of the way, and not CO2-inspired hypercapnia or acidosis, that killed them).
Last edited:
~Reads begining~ Why would sci-fi need a realistic world?
Anyhow, my own planet in my fictions makes Jupiter look small, but has just a slightly higher gravity than earth. Rotates in a way they one side is always facing its sun.
Also, there's lakes of mercury, waterfalls that flow upward (Come on! It's cool! ), rubber-like snow, the sky's purple, etc.
One of this world's moons is like Ogros from Dr. Who....a place that's a swamp of amino acids and primative proteins, which the life forms living there feed via absortion.
I say, when making worlds in your story....as Terry Nation once said, "If the rocks talk on your planet...then fine, they do, because it's YOUR world and no one can deny that."
In otherwords, just have fun!
Anyhow, my own planet in my fictions makes Jupiter look small, but has just a slightly higher gravity than earth. Rotates in a way they one side is always facing its sun.
Also, there's lakes of mercury, waterfalls that flow upward (Come on! It's cool!
), rubber-like snow, the sky's purple, etc.One of this world's moons is like Ogros from Dr. Who....a place that's a swamp of amino acids and primative proteins, which the life forms living there feed via absortion.
I say, when making worlds in your story....as Terry Nation once said, "If the rocks talk on your planet...then fine, they do, because it's YOUR world and no one can deny that."
In otherwords, just have fun!
Way too much argon or nitrogen, while not toxic would displace the oxygen in your lungs so you wouldn't be getting enough.
And, if the plants are like ours and do breathe CO2 and exhales oxygen, then with all that plant life, it would makes tons of O2, hence my thinking that it's not a CO2 thing. If it was, it would greenhouse the planet into being to hot for humans.
But, it's a fantasy movie, so I don't need 100% realism. Mcguffen important element, Mcguffen bad gas in the atmosphere.
Because the "sci" is short for "science." It amazes me how often people forget that.
And more generally, because the setting of a story is important in influencing the choices and actions of the characters, so it's a fallacy that you can separate plausible character-building and drama from plausible world-building. This is true even outside of science fiction. If you're writing a love story about a man driving cross-country to reunite with a lost love, then the realities of geography, automotive function, traffic laws, and so forth would provide opportunities and obstacles in his quest and shape the story, so it would be important to think them through and depict them consistently. If you don't, if you just make up random BS, then it makes the events of your story more arbitrary, and that makes the emotional journey of the character more arbitrary and less real.
Even a fantasy world, a universe with imaginary and magical laws, still needs to be thought through carefully and depicted consistently in order for the story to be its strongest, in order for dramatic events and choices to hold together optimally. So a "sci-fi" or fantasy setting is no excuse for assuming you can lower your standards as a writer and make up a random or nonsensical environment. And if you're going to call what you write science fiction, then you might as well do the work and get the science at least reasonably right, allowing for poetic license.
I don't think there's any way a solid body could have such a low density. It'd have to be hollow or porous, and what would keep its own gravity from collapsing it?
In real life, hardly any planets are bigger than Jupiter. Past a certain point, the more massive a planet gets, the more its core is compressed into degenerate matter, so the size increase is cancelled out. Jupiter represents pretty much the maximum size that any planetary body can attain -- with one exception. Some "hot Jovians" orbiting very close to their stars have their atmospheres expanded substantially by the heat, giving them a larger radius than Jupiter and a very low density.
I say, when making worlds in your story....as Terry Nation once said, "If the rocks talk on your planet...then fine, they do, because it's YOUR world and no one can deny that."
In otherwords, just have fun!
Having a consistent, logical world is fun, because when you have a solid framework of rules to build on, you can extrapolate beyond what you've already thought of and discover fascinating and surprising new possibilities that never would've occurred to you otherwise. That's the power and beauty of scientific theory. It's a mechanism for taking you beyond what you know and guiding you to new possibilities. And that's great fun. If your worlds never surprise you, where's the fun in that?
For instance: for a long time, I wanted to write a novel set on a world that was made mostly of water. Initially, I had some ideas for how to do that, ideas that were fairly fanciful, though I thought at the time that they made some sense. Anyway, I eventually did it in my novel Star Trek Titan: Over a Torrent Sea, and I based that in a new scientific theory that was only five years old at the time. I read all the research papers on the theory, studied associated aspects of science, and what I learned led me to come up with a whole new category of life inhabiting the depths of the planet, something really exotic and fascinating that I never, ever would've thought of if I hadn't done the research and been inspired by the possibilities inherent in the science.
Sure, imagination is fun. But the more knowledge you have to build on, the farther your imagination can take you.
I think that's dependent on the pressure of oxygen. For instance, if an atmosphere had half our percentage of oxygen but twice the pressure/density, you'd be taking in the same amount of oxygen with each breath. After all, here on Earth your every inhalation contains three and a half times as much nitrogen as oxygen.
It's not a zero-sum game. It's not like Earth's atmospheric conditions represent a default. It's possible for an alien planet's atmosphere to have hugely more CO2 than Earth's does now. Heck, the atmospheres of Venus and Mars consist primarily of CO2. If Pandora's atmosphere had a great enough CO2 excess -- perhaps because of heavy vulcanism as Myasishchev suggested -- then even all that plant life wouldn't be able to use up all of it.
Again, only if you assume it's exactly like Earth in every other respect. If the planet is further from its sun, receiving less light and heat, then that could cancel out the added greenhouse effect.
See, that's the problem. The makers of Avatar have clearly put a good amount of effort into making a lot of the science plausible. So when something is fanciful within that framework, it stands out as an implausibility, a lowering of the filmmakers' own standards. Sure, there's room for poetic license, but if the implausibility is too fanciful or too poorly justified, then it feels incongruous.
Cameron had the same problem with The Abyss. He did an incredible job with realism in the deep-sea equipment; in fact, almost all of it actually worked and the undersea scenes were actually shot underwater. But that impressive realism just made it harder to suspend disbelief for the thoroughly fanciful aliens in the film. It created expectations of credibility that the aliens failed to live up to.
What were wrong with the aliens? I quite was impressed by them myself. When aliens are used, chuck out what you know and pretty much go with it. They are aliens, therefore, I expect alot of stuff to be not expected or in the box, as it were.
What were wrong with the aliens? I quite was impressed by them myself. When aliens are used, chuck out what you know and pretty much go with it. They are aliens, therefore, I expect alot of stuff to be not expected or in the box, as it were.
That's bull. Aliens aren't magical fairy creatures. The same physical laws apply everywhere in the universe, and "they're alien" isn't a license to ignore physics or evolutionary logic. When a filmmaker puts so much care and thought into every other aspect of the film, alienness is no excuse for abandoning that dedication and just making stuff up at random. There's never an excuse for deliberately lowering your standards.
The main problem was the ending of the film.
The aliens brought the human crew to the surface in seconds and somehow prevented decompression from hurting them through some magical, remote method that involved no direct contact and that they didn't even feel. That's completely absurd. It's magic, pure and simple. Given the physical, chemical, and biological mechanisms involved in depressurization, I profoundly doubt there's any way it could happen that way. Even if some super-advanced technology could moderate the process in such a way that decompression could safely occur faster, there's no way it could be done invisibly and intangibly at a distance. Pressure changes cause physical changes in the body. They're not just a state of mind.
Earth was once like Hoth, about 700 million years or so, expanses of ice sheets from the poles to the equator.
I know what you mean, but I was OK with it as long as they acknowledged it in the movie. I suppose that's just handwaving or "hanging a lantern on it". But it still beats all those movies where they forget about that problem completely.
^But that's just it. If they wanted to deal with it merely by handwaving or lantern-hanging, they shouldn't have put so much care into the realism of the human technology. Because that created a very high bar for plausibility, a high set of expectations that made it harder to suspend disbelief for something so fanciful. If a story is fanciful all around, like, say, a Star Wars movie or a Doctor Who episode, I don't worry too much about things that don't make sense. But if you spend two hours impressing me with your dedication to realism and credibility, and you then turn around and toss something purely nonsensical at me, it's a jarring incongruity.
Just to point this out, in case someone hasn't already - every known planet in reality is a "one environment" world...it's Earth that seems to be the freak.
Well, they had already established that the aliens could do "magic" by animating water and causing it to float through the air without regard for mass or anything else. The business at the end didn't take me any further out of the moment. I think I'll just agree to disagree with you on this one and move on.
Now, as for "Leviathan", which came out the same year...
Well, yes, as I said, the portrayal of the aliens as a whole was jarringly fanciful in contrast to the well-thought-out realism of the rest of the film. But it was the ending that really put it over the top.
^
Which isn't really a problem for Avatar. While we also begin with humans in a situation which I guess is fairly plausible; the film gives us the rather fantastical aliens and world of Pandora early on. While there are elements of grounded science fiction it's pretty much an outright science fantasy film.
Which isn't really a problem for Avatar. While we also begin with humans in a situation which I guess is fairly plausible; the film gives us the rather fantastical aliens and world of Pandora early on. While there are elements of grounded science fiction it's pretty much an outright science fantasy film.