Lots of films employ scientific advisors. But rarely do the filmmakers end up advising the scientists.
However, that’s exactly what happened today, 13 February 2015, when the scientific paper “Gravitational Lensing by Spinning Black Holes in Astrophysics, and in the Movie Interstellar”, co-authored by Professor Kip Thorne and Double Negative’s Oliver James, Eugénie von Tunzelmann and Paul Franklin, was published in the Institute of Physics Publishing’s journal “Classical and Quantum Gravity”.
The paper describes the innovative computer code used to generate the film’s images of a wormhole and black hole, together with their backdrop of stars and nebulae. Using the code, the Double Negative team discovered that, when a camera is close to a rapidly-spinning black hole, spatial peculiarities known as caustics create multiple images of both individual stars and of the thin, bright plane of the galaxy in which the black hole resides. This is the first time the effects of caustics have been computed for a camera near a black hole.
In order to effectively visualise the caustic effects without unwanted flickering, the Double Negative team decided to abandon the standard rendering approach of using a single light ray for each pixel. Co-author of the study and chief scientist at Double Negative, Oliver James, explained:
“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. Instead of tracing the paths of individual light rays using Einstein’s equations—one per pixel—we traced the distorted paths and shapes of light beams.”
Co-author of the study, Kip Thorne, added:
“This new approach to making images will be of great value to astrophysicists like me. We, too, need smooth images.”
Oliver James continued:
“Once our code – Double Negative Gravitational Renderer (DNGR) – was mature and creating the images you see in the movie Interstellar, we realised we had a tool that could easily be adapted for scientific research.”
A second complementary paper by the same authors, “Visualizing Interstellar’s Wormhole”, is available on both the arXiv and Double Negative websites, and will be published soon in American Journal of Physics. It describes the creation of the Interstellar wormhole, and highlights the variety of study opportunities offered by the film for general relativity students.