Whether Interstellar was a good movie or not is still up for debate, but what seems certain now is that it led to some good science. Last year, Wired magazine explained how the visual effects team behind the space blockbuster worked with theoretical physicist Kip Thorne to create a new computer simulation to model how light would be dragged into the black hole Gargantua. Now, the calculations underpinning this code have been published in a scientific journal, with astrophysicists saying the software could help them model other celestial objects in the future.
existing software just couldn't handle the size of the IMAX screen
When the Interstellar team began working on simulations for the film, they realized that current technology wasn't up to scratch. Their visualizations of stars flickered when scaled up to the 23 million-pixel resolution of an IMAX screen. Instead, they had to create an entirely new simulation model, which they named DNGR — or, the Double Negative Gravitational Renderer.
"To get rid of the flickering and produce realistically smooth pictures for the movie, we changed our code in a manner that has never been done before," said Oliver James, chief scientist at special effects team Double Negative, in a press release. Instead of tracing the paths of individual rays of light, say James, he and his team looked at bundles of light, creating a smoother moving image then ever before seen. This proved especially fruitful for visualizing gravitational lensing — an effect where light is bent around massive objects as it travels through space. It's these visualizations that could help astrophysicists model more cosmic oddities in the future.
Interestingly, the paper published in the journal Classical and Quantum Gravity also shows that the image of Gargantua that made it into the film wasn't the most scientifically accurate one. In the movie, Gargantua's accretion disc — the glowing ring of matter being pulled around, above, and below the black hole — was created at a relatively early stage, and has a fairly symmetrical design with a red tinge to the light.
The most realistic version of Gargantua. (IOP Science)
However, by adding extra detail to their code, the scientists were able to create a more accurate image of Gargantua. The final version takes into account the vast rotational forces that would be created as the black hole spins. Not only do these forces throw matter to one side of the black hole, they also can change the color of the light for the observer. That's the Doppler effect — when a wave changes relative to an observer, because the source is moving. It's most obvious in day-to-day life when a vehicle with a siren drives by, and the sound gets higher as the siren gets closer, then lower as it moves away — but it also affects light.
"We base it in science, but we always give control so that artists can change it," James told the New Scientist. "The first images we gave [director Christopher Nolan] didn't have the Doppler shift, and I think he fell in love with them." Hopefully, scientists won't just fall in love with the simulations produced in the future by scientists using the Interstellar code — they'll also make them as accurate as possible as well.