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Peculiar Materials

Video series · Peculiar Materials

Hard Magnet Science

One movie scene an episode, taken apart by someone who does this for a living. This is the written version — the numbers, the sources, and the parts that did not fit on screen.

Short version The point is not to dunk on films. A scene you have already seen is the cheapest way into some genuinely good physics, and every so often a movie gets it right and I have to say so on camera.

What this page skips, so nobody mistakes it for complete. It does not reproduce the episodes — the scene-by-scene readings, the on-screen arithmetic and the jokes are in the videos. It skips every scene I looked at and rejected, which is most of them. It contains no plot summary: if you have not seen the film, the physics still works, and if you have, you do not need me to recap it. And it does not touch the two areas where a magnet engineer is genuinely not the expert in the room — surgery and clinical radiology — beyond naming the places where I stop.

Episode 01
Unobtanium
Avatar, and mountains held up by a superconductor
Episode 02
X2
Coming when the video airs
Episode 01 Avatar (2009) · the Hallelujah Mountains

Unobtanium

Video: published on the Peculiar Materials channel.

Short version The physics is better than it has any right to be. The film names a superconductor out loud, shows the right instrument behavior before it shows the spectacle, and puts its sample on a desk where it belongs. The geology is absurd and the price is worse. Eight out of ten.

The film says more than people give it credit for

Three different things get run together when this scene comes up, and only two of them are the film. Grace names the flux vortex in the cockpit. Jake, in voiceover over the mountains, calls it a maglev effect and says unobtanium is a superconductor — then admits, charmingly, that he does not follow it. That is the film's own vocabulary, not a wiki's.

Official canon adds flux concentrations and describes a “high-temperature” superconductor, in scare quotes. Room temperature is the fan wiki, not canon — though the film shows the desk sample holding station in an ordinary office with no cryostat anywhere in the shot, which is its own answer.

Nobody in the film says flux pinning. That is the physicists' read, and the best-known version of it belongs to Joseph Shoer, then a doctoral student in Cornell's Space Systems Design Studio, who wrote about the scene in 2010 and had published on flux pinning for spacecraft station-keeping.1 Attributing the good reading to the person who made it is stronger than pretending the film said it.

Pinning, not the thing everyone pictures

When most people say a superconductor floats, they are picturing the Meissner effect: all flux expelled, pure repulsion, a puck hovering over a track. It is also unstable sideways. Nudge it and it slides off.

Flux pinning is the other one, and it is what the scene actually depicts. In a type-II superconductor between its two critical fields, flux threads the material in quantized vortices that sit on defects and stay there. The result locks all six degrees of freedom — it resists being pulled away as well as pushed closer, and it holds an angle. That is why a pinned puck can hang upside down under its track, and it is why the desk sample in Selfridge's office holds both its position and its orientation. Position alone would be ambiguous. Orientation is the tell.

In practice The demonstration is genuinely cheap. A commercial yttrium barium copper oxide puck, a track of ordinary neodymium magnets and a flask of liquid nitrogen will do everything that rock does in Selfridge's office, for a few hundred dollars. The one thing Pandora has that we do not is a superconductor that works warm.

The number the film hands you

The script puts the floating islands half a mile above the ground. That is the film making its own quantitative claim, which is rarer and more useful than anything I could impose on it.

Set it against the range over which pinning actually grips: millimeters. I am deliberately not turning that into a ratio, because the real range depends on the field gradient and on the superconductor, and a stated factor would be a number I could not defend. The two facts side by side do the work. Shoer's own summary was that pinning is a very short-range effect and that holding those mountains up would need a mind-bogglingly powerful field.1

For scale at the other end: the strongest continuous magnetic field anyone has made is 48.7 tesla, set in 2025 at the National High Magnetic Field Laboratory — a superconducting tape coil about the size of a salt shaker, sitting inside a 31 T resistive magnet.2 The strongest field with a bore you can actually put something into is 45.22 T, at Hefei.3 Earth's surface field is around 50 microtesla — roughly a millionth.

What they got right that nobody mentions

Before the mountains appear, Trudy tells Norm to look at her instruments, and the cockpit displays start misbehaving. That is correct, unprompted physics: fly avionics into a strong field and they misbehave. It is why a magnetic resonance imaging suite is a shielded room and why every object that goes near one is screened. The film puts the side effects in before it puts the spectacle in, which is the clearest sign somebody thought about it rather than reached for a look.

The one number I do not believe

Selfridge says the rock sells for twenty million dollars a kilogram. That is the part of the scene I would argue with, and it is economics rather than materials science.

A price is a ceiling, not a boast: nothing sells for more than the cost of the next-best way of doing the job. A superconductor that holds station on an office desk competes with commercial rare-earth barium copper oxide tape plus a cryostat. Expensive — not two thousand times expensive.

MaterialDollars per kilogram
Unobtanium, per Selfridge20,000,000
The same, in 2026 dollars at 2 percent a year4≈ 1,600,000
Plutonium-238, the priciest thing made at scale5≈ 10,000,000
Gold6≈ 142,000
Rare-earth barium copper oxide tape — a superconductor you can buy7≈ 10,000

At that price nothing gets built out of it. The closest real analogue is plutonium-238, and the United States makes something like a kilogram and a half a year and puts it in spacecraft. Nobody lays track with it. And the premise eats itself: you mine a thing because mining beats making it, and a civilization that flies at a fair fraction of light speed cannot synthesize a compound it is holding in its hand.

The steel-man is real, though, and worth saying out loud: twenty million a kilogram is a delivered price after four and a third light years, quoted by a corporate administrator justifying his budget. That is a freight number, not a materials number. Which still leaves nobody on Earth building anything out of it.

None of this moves the score. The episode grades the physics.

8 / 10

Physics right, geology absurd. I will take that trade every time.

How I score these

Out of ten, and it is the physics being graded rather than the film. A scene can be a bad scene and score well, and a beloved one can score badly, because the question is only ever whether the mechanism would work and whether the numbers hang together. Points come off for the wrong mechanism, not for the wrong genre. Economics, plot and geology are discussed where they are interesting and do not move the number — which is why Avatar keeps its 8 despite a price I would argue with all day. Where I am out of my field I say so and score nothing.

References

Physics needs no citation. Anything about a current product, a quantity, a standard or a price does. Historical attributions stay decade-level where the record is genuinely contested.

  1. Joseph Shoer wrote about the Avatar scene on his own site in 2010, while a doctoral student in Cornell's Space Systems Design Studio; his flux-pinning work for spacecraft station-keeping appeared in the Journal of Spacecraft and Rockets the same year. The reading of the scene as flux pinning is his, not the film's. ↩
  2. 48.7 T, National High Magnetic Field Laboratory at Florida State University, set August 2025 and announced that October — a rare-earth barium copper oxide test coil inside a 31 T resistive magnet. The same laboratory reported 45.5 T from a similar no-insulation coil in 2019 (Hahn et al., Nature 570, 496–499). Figures are the laboratory's own. ↩
  3. 45.22 T hybrid magnet with a 32 mm bore, Hefei, August 2022. This is the usable-bore record and is the one worth quoting if you want a field you can put something into; it is not the absolute record. ↩
  4. This footnote undercuts the table above it. Avatar is set in 2154, so the conversion runs 128 years. At 2 percent a year that is a factor of about 12.6 and the price lands near 1.6 million dollars a kilogram. At 3 percent it is a factor of about 44 and the price falls to roughly 455,000 — only three times gold, and much harder to argue with. The inflation assumption is doing real work here and the episode says so on camera rather than picking the flattering rate. ↩
  5. Order of magnitude only, derived from the United States plutonium-238 production restart: roughly 75 to 90 million dollars over five years against a target of 1.5 to 2 kilograms a year. That is a program cost including standing the capability back up, not a unit price, and it should be read as a scale rather than a quotation. ↩
  6. Gold at 4,418 dollars a troy ounce, 9 September 2026, which is 142 dollars a gram. A spot price on a named day; it will be wrong by the time you read it. ↩
  7. Derived, not quoted: commercial rare-earth barium copper oxide tape at roughly 30,000 to 40,000 dollars per kilometer of 4 mm × 0.1 mm tape, which at about 8.5 grams per cubic centimeter is near 3.4 kilograms per kilometer, or about 10,000 dollars a kilogram. The arithmetic is mine and the tape price is the manufacturers' own, in a market moving quickly enough that the figure should be treated as a scale. ↩

Related

If the physics here was the interesting part: what a magnet actually is covers soft, hard and electromagnets as three different things, and reading a B–H curve is where the numbers behind “how strong” live.

Work with Peculiar Materials

Technical and financial diligence on magnetics, magnet manufacturing, and the rare‑earth supply chain — from oxide to finished magnet.

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