Bad and good science in Avatar!

[Irtaviš Ačankif]

First of all, I love Avatar like you all do (or else why would I be learning Na'vi?  ), but I like science better  .


First, let's start off with the BAD science first.

The Tides of Pandora - BAD!

Let's first start off with Pandora. As everybody knows, Pandora orbits Polyphemus, which orbits Alpha Centauri A. Polyphemus is HUGE, HUGE as Jupiter. Pandora is also not small. To have appreciable gravity (read "mass") about 0.8 that of Earth and have a reasonable density, such as that of the Earth, Pandora has to have a big radius (barring the remote possibility that except for a small layer of dust on the top Pandora is made of pure lead).

Large radius and nearby HUGE Polyphemus translates to, you guessed it, enormous tidal forces. Tidal forces come from the difference in gravitational pull on Pandora's near side to Polyphemus and its far side. To clear things up, think about this. Since Pandora's far side is quite a bit farther than the near side to Polyphemus, it will feel a smaller gravitational pull towards Polyphemus. In the frame of reference of Pandora, this creates a constant tidal force acting on the moon.

Which means what? First of all, assuming Pandora has a tectonic plate structure - which is reasonable considering that it has quite Earth-like mountains - huge tidal forces will create constant earthquakes and violent volcano eruptions. Hometree would fall quite soon without the RDA's help. Why would this happen? Well, the tidal force makes Pandora oval-shaped, with the long end pointed towards Polyphemus. However, Pandora seems to rotate quite normally, so this has to mean that its crust deforms constantly, which of course results in earthquakes.

Enormous ocean tides would also be a problem. I guess that the Ikran People of the Eastern Sea would need to use their ikrans to escape flooded territory and fly back when it dries up...though this seems a far more skxawng-ish solution than simply moving inland.

In a nutshell, tidal forces would make Pandoran life quite difficult - quite unlike the portrayal in Avatar.


The Technology of RDA and the Atmosphere of Pandora - BAD!

In the beginning of the movie we see the RDA shuttle zooming down to Pandora. Hey, that is not supposed to be the way shuttles re-enter! Doing so would create a disaster similar to that of Space Shuttle Colombia - tens of "fresh meat" and super-expensive Avatars burning up in the atmosphere and evaporating into vapor that's probably gonna end up in some Toruk. Several seconds later we see the shuttle land - no re-entry protection tiles AND no charring of the aircraft! Wow...are the shuttles made of pure refined unobtanium?

The exo-pack thingy cleaning the air of toxins including the infamous hydrogen sulfide is also pretty skxawng. Sure, it will prevent hydrogen sulfide poisoning through breathing, but how about severe skin irritation? I don't want to take a walk on Pandora only to find my skin burned like a 2-hour sunburn from neck to toes.

The Samson helicopters are also pretty bad designed. If the rotors tilt forward, yes, the helicopter will follow and tilt forward as well, but it wouldn't stop. The 'copter would just go in somersaults forward. I don't see Trudy leveling out the rotors when the helicopter starts going forward - it stays in the pointing-ahead configuration.

Hell's Gate has some bad science too. For example, the pressure inside is clearly higher than outside - when Quaritch yells "Mask on!" and kicks open the door, air just blasts out of the complex. Of course, this can be explained since Pandora's atmosphere has a lower pressure than that of Earth, but are those RDA guys skxawng enough to try to maintain a perfectly standard Earth atmosphere at 101.3 kPa inside Hell's Gate? Why don't just filter out the carbon dioxide and hydrogen sulfide and leave the ~80 kPa nitrogen/oxygen/xenon atmosphere as it is? Additionally, having a pressure differential means that a small scratch on a window will make it explode AND that people exiting Hell's Gate would suddenly have their ears pop quite violently.


Angry enough at James Cameron to such grossly misrepresent your world, fellow Na'vi? Here are some GOOD science in Avatar:


Avatar controlling and display panels - GOOD!

Many people think this is really bad science. Yes, I agree, flawlessly transmitting all of the sensory back to the control room from right in the middle of the Flux Vortex is pretty bad science. But there is one thing that they did right: the display panels of the avatar control room, which showed detailed phases and data about the avatar controlling mechanism which ALL ARE GOOD SCIENCE.

On the lefts side of the screen there appears four phases:

STAGE 1: SLEEP INIT / STEM BOOT
STAGE 2: S4 SLEEP / SUBCORT BOOT
STAGE 3: REM INIT / CORTICAL BOOT
STAGE 4: PHASE LOCK / PHASE BOOT

Stage one, apparently, is sleep initiation, where the driver is put to sleep. Stage two is S4 sleep, a deep kind of sleep. I don't know what the purpose is of stage two. Stage three stands out. It is "REM initialization" or the initialization of REM sleep, otherwise known as dreaming sleep. Dr. Stephen LaBerge of Stanford University has done studies showing that during REM sleep and in our dreams, our thinking processes run as fast as and are similar to that of waking life, which is essential because we don't want Avatars to be permanenly skxawngs. REM sleep also paralyzes us, which is essential because we don't want Jake wiggling in the little MRI-type thingy bumping into things and hurting himself. Phase 4 is phase lock, presumably meaning synchronization of brain waves between the two bodies.

Interestingly, in a real life implementation the avatar does not need to have a brain. It just needs to receive signals and give back sensory info - a chip in the head should do.


Eywa ngahu!

[Lolet]

Gosh darn it, why'd you have to go and burst my bubble? 

[Irtaviš Ačankif]

Of course you can go conspiracy theory like the Death Star conspiracy theory (look it up)  to explain all of the bad science.

Here's my story:

Wikileaks' agents on Pandora have tapped into the bio-network of trees and wildlife in Pandora with their technology called Tsaheylu Obstruction Routing (TOR), which can arbitrarily download data uploaded by the Na'vi and redirect tsaheylu links via Flux-Vortex-proof 10GHz wireless interlinking to the Wikileaks HQ. By covertly installing TOR units in the Tree of Voices and in Tsu'tey's ikran, they have uncovered the huge conspiracy of Avatar.

Before the attack on Hometree, Mo'at secretly signed an agreement with Colonel Quaritch. Quaritch was to indefinitely lease a Samson helicopter, ten submachine guns, one thousand Dr. Seuss books, and a link station to the Omatikaya tribe in exchange for the evacuation of Hometree. However, Mo'at decided to keep the operation totally secret, so she put up a puppet show of refusing to leave and falsely accusing poor Jakesully, a 19-year-old Na'vi who just finished Iknimaya, of being an avatar.

But why did Jakesully become Toruk Makto? In fact, Tsu'tey and Jakesully have secretly agreed to steal anaesthetics and a dart gun from the RDA. After they succeeded, they shot down a Toruk and Jakesully just went on it.

In the battle of the Tree of Souls, the Na'vi were about to be defeated, when the Wikileaks team decided to test drive their new TOR system. A mechanical glitch resulted in the tsaheylu between the Na'vi ikran makto and their ikrans to be broadcasted across the entire area of the Tree of Souls, which resulted in Pandoran wildlife effectively attacking the RDA against their will.

Neytiri was just a made-up character built to reinforce the notion that Jakesully was an Avatar.

The whole movie was an Omatikayan propaganda film to discredit the RDA, which actually left because too many bulldozers were bombed by Na'vi ikran.

[Tsyal Maktoyu]

Tidal forces: This was an interesting read.

http://wondercow.blogspot.com/

And keep in mind that Polyphemus is smaller than Jupiter (roughly between Jupiter and Saturn, leaning toward Saturn IIRC). If Pandora is then, in fact, tidally locked, then ocean levels would remain relatively constant, mostly changed by forces from other passing moons (in a way more akin to the Earth-Moon tidal relationship). So while Pandora does have 20% less gravity than Earth (but also a 20% denser atmosphere), Polyphemus is also smaller than Jupiter, so the equation should still work. Though tidal forces still do cause increased volcanic activity for the moon.

The shuttles aren't like today's shuttles, per se. They are more like VTOL space planes. Why could they not follow a different reentry pattern than the current shuttle?

And they did account for the sulfur dioxide. I read somewhere that troops with exposed skin were limited to short shifts, to prevent skin irritation.

As for the Samson, couldn't gyroscopic stabilization counteract that?

As for Hell's Gate, isn't that just a revamp of the old violent decompression of an airplane myth? I'm sure Hell's Gate was constructed with a type of glass (or if not traditional glass, a clear nanomaterial) that was designed to hold pressure if compromised in some small way.

[Irtaviš Ačankif]

No, AVATAR is repeating the myth that glass and doors burst open into planets. I did not say that Hell's Gate would explode - the window would explode. The exploding airplane myth is that a broken window would make the AIRPLANE explode. THAT is wrong. Additionally, you still don't explain the enormous popped ears and that the humans would be breathing perfectly normally with sanitized Pandoran air.

Tidal locking sounds plausible, but it would mean that Pandora orbits Polyphemus once a day. This would be a way too close orbit and Pandora would slowly spiral in to Polyphemus because of the vestigial atmosphere at those altitudes. By the way, the equation doesn't work. Earth does not orbit Jupiter, so your analogy with Earth is useless. Just look at Europa. It is tidally locked, but see all of those cracks on its surface! Pandora would have lots of canyons with the molten mantle showing beneath (and of course lots of poor skxawng ikran maktos crashing in)

The shuttles are VTOL, I understand. I do not mean "landing" I mean "reentry" which is entering Pandora's atmosphere. The flimsy wings of the shuttle will break during reentry, and during reentry you DO NOT point your nose down and dive. That, I said, would make everything turn into vapor waiting to go in a Toruk.

[Nì'awtua Eyktan]

It would actually be good to have a slightly higher air pressure inside since it would prevent the toxic atmosphere from getting inside if there was a leak.

[Tsyal Maktoyu]

But the equation still stands. If you put an Earth/Pandora sized object in orbit around a gas giant, the object's Roche limitwill still be well below the objects orbiting altitude (in this case, even well inside the atmosphere). You can't really compare Pandora to Europa, either, for two reasons: 1) The relative Roche limit for Europa is higher given it's low gravity (as in, it's not held together as tightly as say, Earth and Pandora), and 2) The techtonic mechanics for the two bodies is different, given each's makeup. So while Pandora may have 0.8g, Polyphemus is smaller, thus reducing Pandora's Roche limit even further into Polyphemus. Tidal forces would be strong enough to increase volcanic and earthquake activity (which it does), it won't make the planet a fractured mess. Basically it would probably be like the Pacific Ring of Fire on a planet-wide scale.

As for Hell's Gate again, maybe I didn't make my self clear enough. With either a hole in the fuselage or a broken window, a plane will NOT explode. A window sized hole would lead to rapid decompression, but an explosion? No. It takes more than a scratch, or even a bullet hole, to cripple a plane. Hell, there were recently a few cases of holes in 737s and they held up fine. With that said, I think the windows in Hell's Gate have more in common with an aircraft's hull than it's thin, flimsy windows. The "glass" (if it is even traditional glass, not some nano or metamaterial) is likely several inches thick, and designed to prevent any structural compromises from spreading (like the stuff the Grand Canyon walkway is made from). Trust me, I'm sure the RDA knows better than to stick commongutter glass in a pressurized complex. Btw, the reason Hell's Gate is pressurized is to keep poisonous Pandoran air out. In the event of a leak, positive air pressure on the inside would force an airflow out of the complex, preventing the inward flow of toxic gases.

I did mean re-entry. I was theorizing that the shuttle used it's other thrusters to provide for a quicker deceleration higher in the atmosphere or something. Though tbh that scene was also filmed well into the atmosphere, as it was breaking through the cloud deck. How do you know it didn't possibly enter the atmosphere while nose-up, and simply nosed down as part of an approach pattern?

[Eyawng te Klltepayu]

Quantum1423, you are wrong about a number of things. I will deal with the tidal heating first and address the other issues later.
The tidal heating in satellites like Io and Europa is not caused by proximity to Jupiter alone, but by a changing gravity differential. A static gravity differential, even a very large one, will not cause tidal heating. The orbits of Io and Europa are significantly elliptical as a result of the presence of the other Galilean satellites. The gravity differential between a moon's far side and its near side will be greater when the satellite is closer to its primary, and smaller when it is further away- and it is this that causes tidal heating. If you removed all the other Galilean satellites apart from Io the orbit of Io would eventually circularize and tidal heating (and resultant volcanism) would cease.

Whether Pandora experiences significant tidal heating or not is thus hugely dependent on the masses and orbits of the other Polyphemian satellites. We know there is some ( this has been confirmed by James Cameron) but proximity to Polyphemus alone will not tell us how much.

['Itan Atxur]

Ahh, see! This is the beautiful thing about story telling. Of course you're completely correct, Pandora is very likely impossible. But when you tell a story, you get to break the rules. Some writers break the rules completely and totally (Harry Potter) and then some at least base their science in reality.

But as for the avatars working in the flux vortex, they do at least suggest that they don't work perfectly. When they first travel to the mountains Grace can be heard saying "She's the least glitchy".

[Irtaviš Ačankif]

@Tsyal Maktoyu:
I am not talking about the Roche limit. Yeah, if you put Pandora inside the Roche limit it will break into pieces. I am not talking about that. For the airplane myth thing, I do know that a small hole won't make the plane explode. What I am trying to say is that on an airplane, a hole in the window will make the WINDOW explode, NOT THE PLANE.

Pressurizing Hell's Gate will actually make leaks more dangerous. Air has inertia and the large airflow will make the interior temporarily at a lower pressure than the outside, pulling the toxic gases right in.

@Eyawng te Klltepayu
There IS a changing gravity differential on Pandora. By the look of Pandora (hurricane systems, dynamic ocean) it is obviously not tide-locked to Polyphemus. This means that the crust is constantly grinding against itself as it rotates.

Additionally, the big issue isn't the tidal HEATING, it is the earthquakes and such.

@'Itan Atxur
If carefully calibrated instruments go awry in the Flux Vortex, even the best avatar would have lots of glitches. I'm not meaning total paralyzation or unability to go in link, but imagine VHS-quality vision, AM-quality audio, and 400ms ping... you fly an ikran and before you is a big mountain. You are about to crash into it 300ms later. You make the avatar turn left. Unfortunately, 300ms later, you crash into the wall, and then after 100ms your dying ikran makes a somersault to the left...


@Everybody
I AM an Avatar fan. I think that part of any sci-fi movie experience is to get the good and bad science out of it. The Core becomes enjoyable with its terrible plot only because of its extremely terrible science.

I am sure to say the Avatar got lots of things right, like the way to link with Avatars, and alas! the Na'vi language! No more gibberish from random number generators!

[Eyawng te Klltepayu]

Re: The Valkyrie shuttles. We do not see a Valkyrie shuttle performing re-entry or the orientation it adopts for re-entry. The first time we see one in the atmosphere it is punching through some rain-clouds - well within the troposphere.

Re: Hell's Gate. Maintaining a small but significant pressure differential between the enclosed parts of the base and the toxic atmosphere of the exterior is entirely sound practice. The windows would not violently explode in the event of a minor breach unless the windows were really bad and the pressure differential much greater than is actually necessary. Similar measures are carried out on in some locations on Earth. Clean rooms (where spacecraft are assembled) are one example.

An 80/101kPa change in pressure (or vice versa) does not sound excessively 'violent' to me at all. Holding your nose shut and attempting to blow through it will quickly equalize the pressure and alleviate any discomfort.

['Itan Atxur]

Why do you think Avatar has a terrible plot?

[Eyawng te Klltepayu]

@Eyawng te Klltepayu
There IS a changing gravity differential on Pandora. By the look of Pandora (hurricane systems, dynamic ocean) it is obviously not tide-locked to Polyphemus. This means that the crust is constantly grinding against itself as it rotates.

Ah wrong again! You do know that just because a body is tidally locked does not mean that it is not revolving, merely that the revolution and rotation periods are identical. There will still be a significant Coriolis effect to drive the formation of hurricanes. And I did not say that Pandora experienced no tidal friction at all, merely that proximity to Polyphemus does not mean that it would experience so much that it would be another Io.

Additionally, the big issue isn't the tidal HEATING, it is the earthquakes and such.

And the driver for those earthquakes is... a shifting gravity differential. See earlier post.

[Irtaviš Ačankif]

Why do you think Avatar has a terrible plot?

I mean The Core, not Avatar. The Core was selected as the worst physics ever on Bad Movie Physics. And it's so fake, it's fun!

[Irtaviš Ačankif]

@Eyawng te Klltepayu
There IS a changing gravity differential on Pandora. By the look of Pandora (hurricane systems, dynamic ocean) it is obviously not tide-locked to Polyphemus. This means that the crust is constantly grinding against itself as it rotates.

Ah wrong again! You do know that just because a body is tidally locked does not mean that it is not revolving, merely that the revolution and rotation periods are identical. There will still be a significant Coriolis effect to drive the formation of hurricanes. And I did not say that Pandora experienced no tidal friction at all, merely that proximity to Polyphemus does not mean that it would experience so much that it would be another Io.

Additionally, the big issue isn't the tidal HEATING, it is the earthquakes and such.

And the driver for those earthquakes is... a shifting gravity differential. See earlier post.

I meant rotating with respect to Polyphemus, as rotation with respect to Polyphemus is what induces gravitational changes. Tidal locking will make the planet stationary IN THE FRAME OF REFERENCE OF POLYPHEMUS.

I don't want to get into a big argument here, but if Pandora is tidally locked, it would have to rotate around Polyphemus every 24 hours.

This brings a big problem. Let's suppose that two tribes on Pandora, Tribe A and Tribe B, live on different sides of the moon. Tribe A lives on the side far from Polyphemus. This means that it will have ordinary days and nights caused by the sun setting and rising.

Tribe B, however, will experience eternal darkness. Think about this this way. After the sun sets, it is night, right? Polyphemus is high above the horizon, filling the sky with its splendor, since it is illuminated when Tribe B expriences the night. A big shadow will be on Polyphemus, which comes from Pandora.

However, what happens when the sun rises? It rises for few minutes, and immediately gets eclipsed by Polyphemus. From the frame of Pandora, the sun moves across the sky, constantly behind Polyphemus. It is only when the sun sets that it gets out of the eclipse, but alas! Pandora is blocking it now!

This would make half of the planet dark and cold, cold enough to kill a thanator and dark enough to make a Toruk crash into a cliff without knowing it.


My point that if a planet is supposed to be habitable, it cannot be tidally locked.



My other point is I love Avatar! 

[Eyawng te Klltepayu]

No. Polyphemus only occupies a moderate portion of the sky on the Polyphemus facing hemisphere. There are some scenes in the film where Polyphemus appears to be larger - this is the result of an artistic decision to use a narrow FOV for some shots and does not represent the actual apparent diameter of  Polyphemus. For a better idea of Polyphemus' actual apparent diameter look at the shot of it behind Jake when he runs out into the Hell's Gate training area.

[Irtaviš Ačankif]

No. Polyphemus only occupies a moderate portion of the sky on the Polyphemus facing hemisphere. There are some scenes in the film where Polyphemus appears to be larger - this is the result of an artistic decision to use a narrow FOV for some shots and does not represent the actual apparent diameter of  Polyphemus. For a better idea of Polyphemus' actual apparent diameter look at the shot of it behind Jake when he runs out into the Hell's Gate training area.

OK, you win.

Yes, you can use a tiny FOV to make the moon appear bigger than a mountain 

Let's start talking about good science, lest the argument makes everybody look like a skxawng...

[Tsyal Maktoyu]

Quantum, did you read the rest of the Wonder Cow post about the 24 hour day? According to the calculations, it would be possible, even moreso because Polyphemus is even smaller than the Jupiter used in the initial calculation. And there wouldn't be a "cold" side, either. All sides would get sunlight in a day (se more than others, albeit), and that's not even counting sunlight from ACb.

From a quick doodle, two quadrants of Pandora would have 12 hour days, and two would have 6 hour days. Again, not even counting ACb, or dawn/dusk.

[Irtaviš Ačankif]

Yeah...

ACb is quite far away... that would be like a hundred Moons or something

I am not an argument-prone skxawng, so I'll accept your argument. I originally thought that Polyphemus would be horizon to horizon, which would mean that Pandora is in the Roche limit, which would mean that there is a dark side...etc and etc. Now I understand how everything works.

Here is another point:

The floating mountains of Pandora float apparently because of the strong magnetic field levitating them. A magnetic field strong enough to levitate mountain-sized superconductors (assuming they are pure unobtanium) should be strong enough to suck all of the RDA machinery to the Tree of Souls. The enormous magnetic flux that would be generated by moving would mess up with people's brains and nervous systems, making them a hallucinating skxawng at least and a corpse arcing on itself with 100-amp electric currents at most.

However, maybe unobtanium has an extremely low density and floats by itself...think of a rock that is lighter than air...?

By the way, don't get offended by the "skxawng"s. I am practicing using a Na'vi word every post, and "skxawng" seems to be the easiest to use. Another thing, did you notice that in the movie, Jake pronounced "skxawng" without the ejective, like "skawng"?

[Eyawng te Klltepayu]

Yes, the strength of the local magnetic field that would be necessary is a serious issue. James Cameron is aware of this and mentioned it in the Caltech panel discussion of the science of Avatar:

http://s3.amazonaws.com/planetary/radio/pr20100524_uncut_avatar_panel.mp3

The talk with astronomer Mike Brown is also worth a listen:

http://today.caltech.edu/theater/09_10/cameron/cameron.mp3