Christopher Nolan’s movie ‘Interstellar’ will be an epic space adventure encapsulating humanity’s need to explore the Universe, but it’s the visual effects for the movie that are garnering early attention.

By combining the help of one of the world’s leading black hole physicists with a cutting-edge visual effects (VFX) team, ‘Interstellar’ will depict the most scientifically accurate black hole in science fiction history. And, during production, some new discoveries were made as to how a black hole would appear if we could view it up close.

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“Neither wormholes or black holes have been depicted in any Hollywood movie in the way they actually would appear,” said Caltech physicist Kip Thorne in a behind-the-scenes video released by Paramount Pictures (featured below). “This is the first time that the depiction (of a black hole) began with Einstein’s general relativity equations.”

General relativity describes the nature of gravity. How a black hole, being the most gravitationally dominant object in the known Cosmos, would look to an observer can therefore be described by Einstein’s equations — except for when tangling with the Black Hole Information Paradox, then you’ll need some quantum equations to boot.

Thorne is a lifelong friend of fellow black hole guru Stephen Hawking and between both of the theoretical physicists, our modern understanding of how these singularities work has flourished. So with the help of Thorne, Nolan has done something very smart; he’s been able to provide the movie-viewing public with a rare sci-fi look into the actual science of a black hole while maintaining an artistic representation that we can easily comprehend.

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“The visual effects department under Paul Franklin and everybody at Double Negative took Kip’s mathematical data and they created real visual representations of what a black hole is meant to look like,” said ‘Interstellar’ producer Emma Thomas.

Warped Spacetime

While crunching the mathematics and arriving at graphical representations of Einstein’s famous equations, Thorne and the movie’s VFX team realized that if a star is positioned behind the black hole, the starlight may become trapped in the warped spacetime close to the black hole’s event horizon. Known as gravitational lensing, this spacetime effect can be used by astronomers to detect exoplanets, for example. But during the production of ‘Interstellar,’ the team realized a spacetime subtlety.

Theoretical physicist Kip Thorne runs through some equations on a blackboard with 'Interstellar' actress Jessica Chastain.Paramount

Intuitively, light from a star behind a black hole may circle the event horizon several times before being released in the direction of the observer (in this case the ‘observer’ is the camera). Visually, the edge of the black hole will be stunning — several different images of the same star will be created at the event horizon’s edge.

This produces “a strange sort of funnel in the sky,” with a black disk surrounded by gravitationally warped starlight, said VFX supervisor Paul Franklin.

The Matter of an Accretion Disk

Of course, no black hole would be complete without the addition of a radiating accretion disk. But how would that appear on film?

As matter falls toward the spinning black hole’s event horizon, the gas collects into a hot accretion disk, shining brilliantly. By adding the disk, “we found that if you then render this whole thing and you visualize it all through this extraordinary gravitational lens, the gravity twists this glowing disk of gas into weird shapes and you get this extraordinary ‘rainbow of fire’ across the top of the black hole,” said Franklin.

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“When I saw this disk wrap up over the black hole and under the black hole, I’d known it intellectually, but knowing it intellectually is completely different from seeing it,” said Thorne.

It’s all very well having a scientifically accurate black hole, but if the visual interpretation of a black hole’s mathematics makes no sense, Nolan was under no illusions that he may have had to take some artistic liberties to make the black hole appear more familiar to the viewing public.

“But what we found was as long as we didn’t change the point of view too much … we could get some very understandable, tactile imagery from those equations. They were constantly surprising,” said Nolan.

Now Thorne and the VFX team are preparing some technical papers about their findings for the astrophysical and computer graphics communities. The publications will say: “Here are some things that we’ve discovered about gravitational lensing by rapidly spinning black holes that we never knew before,” added Thorne.

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Science fiction movies are produced to entertain, first and foremost. But as computer graphics become more sophisticated and the science fiction-viewing public becomes more savvy, there is a growing motivation by filmmakers to make space phenomena as ‘real’ as possible. And often that will mean employing the help of scientists to make our most extreme space fantasies as scientifically accurate as possible to maintain a credible storyline.

‘Interstellar’ is shaping up to be one of those rare movies that will combine science and fiction, exciting the viewing public, potentially engaging us with astrophysics in a way we’ve never experienced before.