Unobtainium. So… what exactly is this stuff?

I will probably damage my reputation by saying that I enjoyed last year’s top-grossing movie Avatar on many levels. Even the science, while highly popularised, did not contravene too many known laws of physics and facts of biology. Except for one thing, and that one thing has bugged me ever since. In hindsight, it’s quite amazing how long I allow stupid trivialities to bug me.

Anyway, Unobtainium.

I mean, seriously? Which script editor worth their salt would leave such an obvious ersatz-name in the finished product? What on Earth were they thinking?

As writers do when the going gets tough, I googled it. Apparently, Unobtainium, also spelled Unobtanium, is jokingly referred to in engineering when there is a need for a material that doesn’t (yet) exist. The term is also used to indicate materials that are extremely rare. In the movie, it’s a MacGuffin. What it does is not important. Only that it is rare and very valuable and thus is the reason for the hero’s quest.

Fine by me. I just wish they called it something else.

But it keeps nagging. There is that scene in the movie, you know, where the evil and hapless company director whose name I’ve already forgotten, picks up the sample that floats above a hollow dish. It makes me wonder what this stuff is. It looks metallic, and it floats. By what mechanism and what would people do with it?

First up, why does it float? It seems to me that it needs the dish to stay up in the air. That would suggest a magnetic field. Aside from the fact that I’m unsure that a bowl-shaped dish would emit the right shape magnetic field to keep an object afloat (I’m thinking it would need to be horseshoe-shaped), I’m wondering what the benefits of such material would be. Given a magnetic field strong enough, many materials could be made to float. Maglev trains work on this principle. The floating capacity would depend on the density of the material, the size of the sample and the strength of the field, and two of these can be varied by the observer. Creating a stronger magnetic field just requires more electricity, negating the value of the material. The repelling force that holds the sample in the air can only be as strong as that induced by the magnetic field, so to stay up, the sample must be very light. It could be a very light-weight, strong material. OK, but is that really valuable enough to raze an entire planet?

Secondly, it could be some sort of anti-gravity material. I’ve thought about how this could work, but am drawing blanks. If, for example, the material consisted of atoms of negative matter, each of these atoms would repel each other (as opposed to attracting each other, which is what regular atoms do), and the material wouldn’t stay together in a clump (hint: this is why we haven’t found any negative matter). But let’s suppose some sort of property existed that rendered the material inert to gravity.

Fine, but why stop at gravity? It’s nothing but a force (actually, it’s an acceleration, but let’s not get too technical). A material cannot know if a force applied to it is the result of gravity or something else. Would this type of Unobtainium resist being pushed or picked up? Ah, but it would only be moved if physically in contact with the object doing the pushing or pulling.

Fine. We have just established that Unobtainium would be an excellent material for making heavy lift, single stage to orbit space ships. Stuff that negates gravity. Woo-hoo!

Except now we’re in orbit. How do we come down in a space ship that wants to go the other way? Er…?

So what about you? What do you think would make an element exceedingly valuable?

P.S. I’m sure there is a short story in some of this. Somewhere.

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6 comments on “Unobtainium. So… what exactly is this stuff?

  1. It’s a room temperature super-conductor. It’s also the “reason” the floating mountain things on Pandora float. It annoyed me too. (Though I found “unobtainium” amusing.) The floating mountain things annoyed me the most. BUT for floating in a dish like that… just YouTube up superconductor and you’ll find something looking very similar but with liquid nitrogen being poured over it to keep it cold enough to super-conduct. Superconductors are weird. Room temperature superconductors are a holy grail of physics/engineering/material science.

    • wonders what strength field that would result in so that it can lift mountains that size, and whether biological life, or at least human presence, would be totally impossible in such a strong field.

      • …magic. (Porous rocks? REALLY strong magnets…)

        And also, I think that up until the point where they start doing funny things with water (which they clearly weren’t on Pandora), magnetic fields are generally pretty safe. I’ve seen a frog levitated in a magnetic field and then hop away seemingly happily. Not in real life though, which brings me back to: magic. Of the pseudo-scientific variety ;-p

  2. Uhm, so how does that work? Superconductors have zero resistance to electrical current, but how does that make them float?
    Also wonders, but you’d be unlikely to know the answer to that (grins) why then the evil company dudes didn’t cart off the floating mountains. Would have been much easier than getting rid of that tree. As aside, does the superconductor also make the compass go haywire?

  3. Well because they have zero resistance to current, currents spontaneously run through the surface and set up a strong magnetic field (same idea as an electromagnet but without the input electrickery). So really, in your picture the bowl thing would be made of a normal (good quality) magnet and the floating thing would be a chunk of unobtainium (or vice versa would also work).

    See the intro and top two pictures on the wiki: http://en.wikipedia.org/wiki/Superconductivity

    Maybe the floating mountains are just magnetic and are floating because of the magnetic field set up by the unobtainium in the planet’s crust. Either way, the magnetic fields from the unobtainium would definitely screw up compasses. So would the floating mountains. I feel like compasses would in no way be a useful tool on Pandora.

  4. This is derived from a purely layman’s C average in physics perspective (because math and I are casual acquaintances). Two mass objects are pulled together through the formula:

    Force=Gravity(Mass-A [times] Mass-B [divided by] Distance r-AB [squared])

    So if Mass-A is most of the things on Pandora, and Mass B is the Unobtainium, what happens if Mass B has a negative value? How can the mass be a negative value?

    Mass cannot be removed from an object, only moved. An atomic bomb that goes off in a theoretical containment box results in the same mass inside, the only way for the mass to go from the box is if heat and or light leaves the box, taking away mass. So what if some atoms in the Unobtainium ore have a way to transfer heat and light or other forms of energy just far enough away from the local model? Possibly through a sub-atomic diameter wormhole conduit to the nearest large mass like a sun. What if the Unobtainium special atoms contain the standard Proton, Neutron and circulating Electrons, and a fourth element circulating with the Electrons, say the Negtrons? If Negtrons are the inlets to a subatomic diameter wormhole; they could transfer heat or light or other energetic bits of mass from the Unobtainium far enough away from the local model while leaving in place the matter of the atom that doesn’t fit into the Negtron’s opening, then the result model could be a negative mass for the pure Unobtainium atom that doesn’t lose it’s matter.

    Now, on Pandora, the base ore is not pure and there exists many standard atoms with a positive mass so together with the special atoms, the combined negative mass would only produce a weak negative attracting force or a very small positive one. This impure ore would wait happily in the Pandora crust waiting to be mined. Then it could be assumed that by volcanic activity or some other force, the floating mountains really contain some of the more pure Unobtainium ore, and therefore the negative mass is enough to make the mass of the mountain float above the planet’s counter activating mass. The special atoms can absorb some of the resultant force that would otherwise attract the two, but not enough to let the mountains float into space (note there is a distance part of the above formula (r-AB).

    It stands to reason that the people mining Pandora have a way to refine the ore even more to remove more of the atoms that do not have the Negtrons, leaving a refined product with a greater negative attracting force. Think of the applications, flying cars, levitating pallets, floating houses, space elevators, and so on.

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