How possible is the movie Avatar?

[Plat]

I read somewhere that James Cameron made the planet Pandora as scientifically plausible as possible according to his scientific advisers.

Are the Na'vi's physically possible? having a humanoid structure and being like 10 feet tall and being so athletic like they were in the movie. Also, how their skeletal structure was coated in carbon fiber, it was also interesting how they could bond with the plant and animal life on the planet with their "hair".

Is this all scientifically possible?

[SkepticJ]

That the Na'vi resemble humans that closely is highly implausible from an evolutionary standpoint. We're the product of a biological heritage, not a rationally built machine.

That said, it doesn't break any laws of physics. It's not impossible, just more unlikely than being struck by lightning on the same day of winning the $100,000,000 lottery because the scratch-card was found on the way to being married to a genius physicist/supermodel.

If they were real, they'd probably move differently than they're shown in the film.

The cross-species hair-telephone--unlikely to evolve. Could be engineered.

Carbon fiber-reinforced bones. Realistic. Given the versatility that cells have with manipulating and precisely depositing atoms, you can get all sorts of cool stuff.

[Plat]

Yeah I was thinking that too, that the Na'vi looked too human to be alien, its possible but just unlikely I guess...what did you think of the environment, creatures, and the Na'vi's physical abilities though?

[Delvo]

Yeah I was thinking that too, that the Na'vi looked too human to be alien, its possible but just unlikely I guess...what did you think of the environment, creatures, and the Na'vi's physical abilities though?There have already been bipedal creatures bigger than us whose fossils tell us that they could do plenty of impressive running and jumping. There have also been quadrupedal creatures much larger than modern elephants which also appear to have been built for more impressive running than them, although presumably not leaping. Elephants' relative non-athleticness is not due to their size but due to lack of need (the predators are all significantly smaller) and, according to some theories, a lower atmospheric oxygen content than the dinosaurs lived in. For this planet's real plant & animal size limits, we and other animals alive today don't come particularly close, although some trees might. Also, the Na'vi are significantly more slender than us, which reduces weight for a given height, and it was stated in the movie that the gravity there is lower, which would also increase the size limits on plants and animals of all kinds. So none of the ground animals' sizes and movements were a problem. The worst problem with them is not size or speed, but that some had six limbs when four would certainly be better, with the extras just getting in the way... but if your ancestors had six to start with, you can't necessarily just logically decide to evolve two away.

The largest Pandoran trees might have been too much, though. I could come up with some "tricks" that might enable trees that big to work, but it would take more imagination and speculation than a lot of other Pandoran life forms require, because unlike with those other species in the movie, there'd be no precedent on Earth, not even if you adjust for Pandora's lower gravity.

Even with the lighter gravity, the large flying animals might still be too big for our atmosphere's density (because air is what holds you up if you're flying), but Pandora could also have a significantly denser atmosphere. The things that glow in the dark have precedents on Earth, usually in dim/dark environments but not always. Some of the Earth's glowy organisms even get induced to light up when they're touched or disturbed, as the movie showed with at least a few species. Given the depth/height of Pandora's forest, it could very well be more shaded at the lower levels than Earths' forests are, and its nights could last longer than ours if the planet rotates more slowly. But those things aren't strictly necessary for bioluminescence; they'd just make it more likely.

The tree seeds that floated in the air and moved like animals also have precedent on Earth; some lineages have both a phase that moves around and a sessile phase that stays put like a plant. (This includes tunicates, which are chordates, which is the category that includes vertebrates; a vertebrate's entire life span corresponds to only the swimming, larval stage of a tunicate.) And the fact that the ones in the movie floated is also easily accounted for by its explicitly lighter gravity and implicitly denser air.

The connections that some of the plants and animals had to each other are chemically and electrically possible, but it's harder to come up with a reason why they would be there. Presumably, animals and plants without them could not subsequently evolve to add them on, but that doesn't mean they couldn't have continued to inherit them from ancestors that had something like them all along.

The avatars must have radio/microwave receivers & transmitters in their heads in order to be remote-controlled, and their human controllers must have some implants at certain parts of their nervous systems for the avatar control beds (and, eventually, perhaps, the Tree of Souls) to connect to. There's no reason why we couldn't develop such interface technology; it would only be an extension of technology that exists today for things such as cochlear implants and amputees' artificial limbs and the electrodes in brain-wave detectors in sleep labs. Also, at least with the avatars, there's the advantage of getting to put the hardware in at an early age and let the brain develop around it. Given the fact that our brains adapt themselves to what they do a lot of and/or feel strongly about, Jake's eventual ability to permanently migrate into the avatar can be attributed to the avatar's otherwise blank nervous system having adapted itself to the job of "being Jake". However, that does call for more information (memories and feelings) to have been transferred than pure remote-control requires, so we'd need an explanation for when and through what kind of connection that happened (avatar development process in the incubator, avatar control bed, Tree of Souls), and a good case could be made that it's not possible.

The Na'vi are very similar to humans, not just in overall organization of the body (two legs, two arms, head on top, face on front), which makes a lot of sense for a technology-inventing species and is likely to be common among them, but even in details that don't really matter in a practical sense and would thus have to just be very very coincidental (facial & bodily proportions, facial expressions, body language, hair on the head but not elsewhere, similar sounds and sound production mechanisms allowing us to speak each other's languages). The most astounding similarity for its complexity is that their physiology and DNA are so much like ours that even a fragment of ours could be combined with theirs at all. There's no scientific rule against two nearby planets just happening to develop species that are highly similar to each other in such specific details that aren't dictated by natural-selection advantages, but the odds are just rather against such coincidences.

"Carbon fiber" is a name for something that our labs & factories produce under exotic conditions; we don't know of a way to get living organisms to produce it. Although it starts with polymers that we know life-forms can produce, the final product is in a more mineral-like state, more similar to graphite than to tough organic polymers such as keratin or chitin. We accomplish the transition by using very high temperatures in an oxygen-free atmosphere. The Na'vi would need to accomplish it with enzymes instead. It's probably possible, but there's no way for us to know the details of how it would be done, because no organism on Earth does it and there's so much we don't know about Pandoran biochemistry, and I can't swear that there isn't some law of physics making it simply impossible within a reasonable temperature range or such. At least, if what we call "carbon fiber" is in fact impossible for a living organism to produce, we can say that their skeletons could use some kind of carbon-based polymer which could be fibrous, so the words "carbon" and "fiber" would still fit. :D

[Plat]

So what do you think of Cameron's attempt at being somewhat possible, how would you grade it? Would you say it is a pretty good attempt or was there no effort involved at all similar to movies like Day After Tomorrow, War of the Worlds, etc.

[Delvo]

A-

Better than most, with the "problems" mostly either being matters of likelihood (and I consider even very unlikely to be better than impossible), or serving the story in such a way that changing them would have required significant changes to the story. Still, there are a handful of exceptions, so it's not perfect.