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enter image description here

Why does the depiction of the black hole Gargantua in Interstellar look the way it does? I understand why the ring is bright (due to the friction) but why does it loop around what seems to be two perpendicular directions?

Apologies:

I posted a slightly re-worded version of this question in Physics stack exchange and only know now that it is bad practice (thanks to Napoleon Wilson). Also, I discovered later that my question in Physics was a duplicate anyway.

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  • @CGCampbell good point, I did wonder which site it might be most relevant to, but I thought this was a relevant question here as it was asking for "in universe" reasons to explain phenomena of a film.
    – hello_there_andy
    Dec 9, 2014 at 0:58
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    Note that a translucent bubble will often appear to be a ring to an observer.
    – Andrew Thompson
    Dec 9, 2014 at 1:16
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    @hello_there_andy While an in-universe description was not directly given in the movie, luckily the in-universe reason matches the real reason since the visualization was to a large degree physically correct afterall. So it seems pretty much on-topic on both sites, it's a proper plot-explanation/realism question here. But please don't deliberately cross-post your questions to multiple sites, that's discouraged behaviour, pick one and ask it there. Afterall your Physics question is already a duplicate anyway.
    – Napoleon Wilson ♦
    Dec 9, 2014 at 1:35
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    Identical question and answer on Physics.SE
    – user11153
    Dec 9, 2014 at 10:24
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    @hello_there_andy Haha, no problem, nobody's perfect. In general there is no problem with questions existing on different sites, this happens naturally (most often between here and scifi.se), as long as they're not asked on multiple sites by same user right away, but you learned your lesson. The question seems a good fit here (and is slightly older than your physics one anyway). For more insight on the matter you can also take a look here. ;-)
    – Napoleon Wilson ♦
    Dec 9, 2014 at 13:18

1 Answer 1

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The appearance of the black hole in Interstellar was not created arbitrarily. It was actually modeled using the real relativistic equations describing the path of light in the gravitational field of a super-massive black hole spinning at near the speed of light. As a result, it may be the most accurate depiction we have to date of what such an object might look like. Astrophysicist and gravity expert Kip Thorne collaborated with the visual effects team to produce new software specifically to model the equations and render the black hole. The appearance was initially somewhat unexpected, but Kip Thorne realized "Why, of course. That's what it would do."

I don't pretend to be an astrophysicist, but on a basic level, here's what's happening: The glowing accretion disk of plasma remains in a single plane as expected (there's no perpendicular ring), but some of the light from the back side of the disk is warped by the intense gravitational field, over the top and bottom of the black hole. Thus in the region just outside the black hole, you are actually seeing around to the back side of it.

Indeed, the discoveries made during the rendering process has even led (or will lead) to the publication of several scientific articles on gravitational lensing.

There's more detail, including a video with Kip Thorne describing the effect, here:

http://www.wired.com/2014/10/astrophysics-interstellar-black-hole/

Filmmakers often use a technique called ray tracing to render light and reflections in images. “But ray-tracing software makes the generally reasonable assumption that light is traveling along straight paths,” says Eugénie von Tunzelmann, a CG supervisor at Double Negative. This was a whole other kind of physics. “We had to write a completely new renderer,” she says.

Von Tunzelmann 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.

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    For anyone interested in reading more: this is simply called a "gravitational lens" - the wikipedia-article: en.wikipedia.org/wiki/Gravitational_lens
    – oezi
    Dec 9, 2014 at 7:02
  • From paragraph to paragraph, your answer leads to increasing mindblow as a function of how much more I read
    – hello_there_andy
    Jan 28, 2017 at 6:08
  • this is the ans i was waiting for long time.
    – roottraveller
    Aug 14, 2017 at 6:49

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