Visualizing the physics in the film Interstellar


Although I like science, or maybe because of it, I tend to get irritated with films that casually break the laws of science merely to achieve a cheap solution to a plot problem. I don’t expect perfect fidelity but gratuitous violations of laws (such noisy explosions in space or the presence of Earth-like gravity on spaceships) are annoying. This is why I liked 2001: A Space Odyssey and to a lesser extent Gravity, because they tried to stick as closely as possible to what may be actually possible.

Reader kyoseki sent along this article in Wired magazine that discusses the science behind the new film Interstellar to be released on November 7. It turns out that the filmmakers worked closely with astrophysicist and cosmologist Kip Thorne to be as realistic as possible and turned to him for advice on what black holes and wormholes might look like and what they could do.

But then something unexpected happened.

So [visual effects expert Paul Franklin] asked Thorne to generate equations that would guide their effects software the way physics governs the real world. They started with wormholes. If light around a wormhole wouldn’t behave classically—that is, travel in a straight line—what would it do? How could that be described mathematically?

Thorne sent his answers to Franklin in the form of heavily researched memos. Pages long, deeply sourced, and covered in equations, they were more like scientific journal articles than anything else. Franklin’s team wrote new rendering software based on these equations and spun up a wormhole. The result was extraordinary. It was like a crystal ball reflecting the universe, a spherical hole in spacetime. “Science fiction always wants to dress things up, like it’s never happy with the ordinary universe,” he says. “What we were getting out of the software was compelling straight off.”

[Eugénie von Tunzelmann, a computer graphics supervisor at the award-winning special effects firm Double Negative] tried a tricky demo. She generated a flat, multicolored ring—a stand-in for the accretion disk—and positioned it around their spinning black hole. Something very, very weird happened. “We found that warping space around the black hole also warps the accretion disk,” Franklin says. “So rather than looking like Saturn’s rings around a black sphere, the light creates this extraordinary halo.”

That’s what led Thorne to his “why, of course” moment when he first saw the final effect. The Double Negative team thought it must be a bug in the renderer. But Thorne realized that they had correctly modeled a phenomenon inherent in the math he’d supplied.

Still, no one knew exactly what a black hole would look like until they actually built one. Light, temporarily trapped around the black hole, produced an unexpectedly complex fingerprint pattern near the black hole’s shadow. And the glowing accretion disk appeared above the black hole, below the black hole, and in front of it. “I never expected that,” Thorne says. “Eugénie just did the simulations and said, ‘Hey, this is what I got.’ It was just amazing.”

So in a surprising turn of events, making the film provided insight into actual physics and Thorne says that he can get at least two publishable papers out of what he learned from the products of the special effects.

I had not initially planned on seeing this film because I find the two main stars Matthew McConaughey and Anne Hathaway to be annoying to watch. It is an irrational reaction on my part to some actors. Hugh Grant, Tom Cruise, Nicholas Cage, and Scarlett Johansson are also on that list. Julia Roberts used to be on it until I saw her in August: Osage County and that fine performance moved her off it.

But now that I have read more on this film, I plan to see it. Here’s the trailer.

Comments

  1. Rob Grigjanis says

    Running time 169 minutes. Why oh why must they make these films so friggin long?

    I remember Thorne as a co-author of the GR tome of tomes. That was friggin long too.

  2. kyoseki says

    This might, however, be the first time a vfx studio got a director to agree to something because it was physically accurate.
    The line “but that’s what would happen in reality!” never seems to go over well.

  3. M can help you with that. says

    One of the last shots in the trailer, at 2:14, looks like it might be the view of the accretion disk that Franklin describes. (It’s also the background picture at the Wired link). I had a reaction like Thorne — I wouldn’t have thought of it, but of course we see light from the part of the accretion disk behind the black hole both above and below it. We’ve seen (IIRC — or else people have just predicted) light from stars behind black holes appear as “rings” around where the (not directly visible) black hole is; this is just a very dramatic illustration of the same idea.

    The “crystal ball” visualization of a wormhole is also something that I’m glad to hear is making its way into a mainstream movie. Travel-by-wormhole always seems to lead to directors and visual-effects teams imagining a two-dimensional “entrance” to a “tunnel” instead of the much stranger view you get from a more realistic (for some value of “realistic”) model.

    I fooled around with visualizing phenomena based on warped spacetime when I was in a seminar on Riemannian geometry; I probably got most of the physics wrong (need to study GR more!), but there are definitely some trippy possibilities that could work well as storytelling devices as well as visual spectacle.

    (How about a wormhole with the “exit” purely in the time direction from the entrance? On the inside it wouldn’t look like a tunnel; depending on the size and geometry, the whole space could look like it was wrapped in an inside-out version of you or whatever vehicle you’re making the transit in, with no visible way out or indication how long you’ll be there. Or weirder.)

  4. says

    They go through a wormhole? Is it a wormhole or a black hole?

    The special effects of getting spaghetti’d and destroyed in a little puff of radiation would be interesting but it’d be a shot movie. I hate the sci-fi trope that there’s something on the other side of a black hole. Uh. No. There’s a big mass of compressed matter spinning at near the speed of light and you slam into it and impart a tiny little kick to that spin. But you stopped existing long before that.

    I think Frederik Pohl did a pretty good job in his original “Gateway” novel (the rest of the series goes downhill rapidly) when Klara crosses the event horizon. But in order for the story to work, there already had to be a deus ex machina violation of Einsteinian space-time. I know that we humans dream of exploring the universe but we probably ought to get used to the idea that travel is a deep time proposition and there’s no magical teleporter.

  5. Rob Grigjanis says

    Marcus Ranum @4:

    I hate the sci-fi trope that there’s something on the other side of a black hole.

    Uh, it’s not just a sci-fi trope. There are valid solutions to the Einstein field equations which contain wormholes. Since black holes and wormholes would probably be indistinguishable to distant observers, you’re being a bit dogmatic, no?

  6. M can help you with that. says

    4 & 5 —

    From the interview, it definitely sounds like they’re distinguishing between black holes and wormholes. The “crystal ball” description works for a wormhole with a spherical opening (what’s seen is what’s out the other side), and is quite distinct from the description of a black hole with an accretion disk and gravitational lensing.

  7. says

    The Earth gravity on a spaceship is something I usually ignore because it’s a concession to the reality of making science fiction while on Earth with a fixed budget. That doesn’t stop me from wondering how they get the gravity to stop at the ceiling.

  8. Dunc says

    That doesn’t stop me from wondering how they get the gravity to stop at the ceiling.

    Or how they deal with that whole pesky inverse-square thing…

    It’s a fun little exercise to figure out what the gravitational field of a flat plate looks like. It’s certainly not anything you’d want to try walking around in.

  9. Rob Grigjanis says

    Dunc @8:

    It’s certainly not anything you’d want to try walking around in.

    If you mean an infinite flat plate of uniform density, it’s just a constant gravitational field directed toward the plate, of magnitude

    2πGσ

    where G is the gravitational constant, and σ is the mass per unit area of the plate. How undesirable walking would be depends on the value of σ.

    Of course, this ignores everything else in the universe, which would be falling towards the plate. Need a bigger umbrella.

  10. Latverian Diplomat says

    @4: The point where tidal forces become lethal (spaghettification) depends on the radius. If the black hole is large enough, that point can be inside the event horizon. Presumably if a wormhole was large enough, you could pass through it without spaghettification occurring at all.

  11. says

    . Since black holes and wormholes would probably be indistinguishable to distant observers, you’re being a bit dogmatic, no?

    I wasn’t aware of that. So the idea is to fling people into black holes and maybe sometimes they’d show up somewhere else, after the rest of the universe experienced a subjective eternity while the people in the wormhole were moving at light speed? Do you have any idea how stupid that sounds? Oh, sorry, is that “dogmatic”?

  12. says

    The point where tidal forces become lethal (spaghettification) depends on the radius. If the black hole is large enough, that point can be inside the event horizon. Presumably if a wormhole was large enough, you could pass through it without spaghettification occurring at all.

    Have you calculated how large that would have to be? 😉

    It’s fucking irrelevant to everything, anyway. The nearest black hole to Earth is over 1000 light-years away. So if we somehow solved the problem of getting there we’ve incidentally solved the problem of interstellar travel, already. I get so tired of mush-brains who want to desperately believe in the pretty science-fiction stories. It’s as bad as (and as stupid as) religion. You’re as likely to accomplish interstellar travel by the power of prayer as you are via wormholes.

  13. Rob Grigjanis says

    So the idea is to fling people into black holes…

    Er, no. The idea would be to get closer to the object so you could tell if it was a black hole or a wormhole. You read the ‘distant observer’ bit, right? And this would be in a science fiction story. You do get that, right?

    I get so tired of mush-brains who want to desperately believe in the pretty science-fiction stories. It’s as bad as (and as stupid as) religion. You’re as likely to accomplish interstellar travel by the power of prayer as you are via wormholes.

    Wow, someone needs a drink, or a chill pill.

  14. Pierce R. Butler says

    I clicked the video in the post and watched it, then clicked the YouTube link to get the URL – and saw a different (less fx, more Noble Speeches) trailer for the same flick.

    Does YT have some sort of rotation feature? How do I get the link for the embedded vid?

  15. Mano Singham says

    Pierce,

    I have no idea. I tried what you did but got the same trailer as the one I embedded. I know that there are three different trailers for the film and maybe they switch it sometimes. If you go to YT and find trailer #3, that will give you the URL you want.

  16. Pierce R. Butler says

    And this time going to YT gave me the same vid as embedded.

    Clearly I’ve stumbled into some vast and arcane conspiracy – excuse me, there’s a knock at the door…

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