The Science of Interstellar

When Chris saw the various possibilities, with varying wormhole length and lensing width, his choice was unequivocal. For medium and large length the multiple images seen through the wormhole would be confusing to a mass audience, so he made Interstellar’s wormhole very short: 1 percent of the wormhole radius. And he gave Interstellar’s wormhole a modest lensing width, about 5 percent of the wormhole radius, so the lensing of stars around it would be noticeable and intriguing, but much smaller than Gargantua’s lensing.

The resulting wormhole is the one at the top of Figure 15.2. And in Interstellar, after the Double Negative team had created for its far side a galaxy with beautiful nebulae, dust lanes, and star fields, it is marvelous to behold (Figure 15.5). To me it is one of the movie’s grandest sights.

^{Fig. 15.5. The wormhole as seen in a trailer for Interstellar. The Endurance is in front of the wormhole, near the center. Around the wormhole in pink I have drawn the Einstein ring, like that in Figure 8.4 for a nonspinning black hole. Primary and secondary images of gravitationally lensed stars move in the same way here as there. Looking at the trailer, can you identify some and trace their motion? [From Interstellar, used courtesy of Warner Bros. Entertainment Inc.]}

The Trip Through the Wormhole

On April 10, 2014, I got an urgent phone call. Chris was having trouble with visualizing the Endurance’s trip through the wormhole and he wanted advice. I drove over to his Syncopy compound where postproduction editing was underway, and Chris showed me the problem.

Using my equations, Paul’s team had produced visualizations for wormhole trips with various wormhole lengths and lensing widths. For the short, modest-lensing wormhole depicted in the movie, the trip was quick and uninteresting. For a long wormhole, it looked like traveling through a long tunnel with walls whizzing past, too much like things we’ve seen in movies before. Chris showed me many variants with many bells and whistles, and I had to agree that none had the compelling freshness that he wanted. After sleeping on it, I still had no magic-bullet solution.

The next day Chris flew to London and closeted himself with Paul’s Double Negative team, searching for a solution. In the end, they were forced to abandon my wormhole equations and, in Paul’s words, “go for a much more abstract interpretation of the wormhole’s interior,” an interpretation informed by simulations with my equations, but altered significantly to add artistic freshness.

When I experienced the wormhole trip in an early screening of Interstellar, I was pleased. Though not fully accurate, it captures the spirit and much of the feel of a real wormhole trip, and it’s fresh and compelling.

What did you think?

16 Discovering the Wormhole: Gravitational Waves

How might humans have discovered Interstellar’s wormhole? As a physicist, I have a favorite way. I describe it here in an extrapolation of Interstellar’s story—an extrapolation that, of course, is my own and not Christopher Nolan’s.

LIGO Detects a Burst of Gravitational Waves

I imagine that decades before the movie begins, when Professor Brand was in his twenties, he was deputy director of a project called LIGO: The Laser Interferometer Gravitational Wave Observatory (Figure 16.1). LIGO was searching for ripples in the shape of space arriving at Earth from the distant universe. These ripples, called gravitational waves, are produced when black holes collide with each other, when a black hole tears a neutron star apart, when the universe was born, and in many other ways.

One day in 2019, LIGO was hit by a burst of gravitational waves far stronger than any ever before seen (Figure 16.2). The waves oscillated with an amplitude that grew and fell several times, and then cut off suddenly. The entire burst lasted for only a few seconds.

^{Fig. 16.1. Top: Aerial photograph of the LIGO gravitational wave detector at Hanford, Washington. Bottom: The LIGO control room where the detector is controlled and its signals are monitored.}