With a science fiction film as complex and involved as Interstellar, there are bound to be moviegoers who simply come away from the film more confused than satisfied. As detailed elsewhere in this guide, Interstellar in particular took special care to be as scientifically accurate as possible, even at the risk of confusing its audience. To its credit, the film takes great care to explain as much of the scientific phenomena discussed in it to its viewers as possible, from the specifics of how a wormhole works to the reason why time runs differently the closer you come to a black hole. Still, in anticipation of the inevitably confused patrons, renowned astrophysicist Kip Thorne, who served as executive producer and chief scientific consultant on the film, published a highly digestable book called The Science of Interstellar concurrently with the film's 2014 release to clear up any confusion.
The Science of Interstellar was written explicitly for non-scientists and helps explain some of Interstellar's more complex elements. As one example, the book dedicates a good amount of time to wormholes from a theoretical perspective. Thorne notes that while wormholes are technically conceivable, they are not naturally occurring, (a fact that Interstellar reiterates), nor are they likely to be artificially creatable. Thorne explains that wormholes would require the presence of something called "negative energy," which has only been created in incredibly small quantities and for very brief moments in controlled laboratory settings, and which would be needed in much larger quantities than currently possible to keep a wormhole open. As noted in the film analysis section of this guide, the wormhole scene is one of the few instances in Interstellar when Christopher Nolan chose to stray from accuracy. Thorne notes that the actual journey through a wormhole would be more or less uneventful: the wormhole would appear as a spherical window of sorts, which one would pass through seamlessly from one section of the universe to the next, as if merely moving through a door; one moment you’re outside the hole, the next you're through it. For the purpose of creating a more visually stunning spectacle, Nolan took creative license to make the scene more dramatic and unrealistic.
Another element of Interstellar that was regrettably lost on some viewers was the notion that gravity can cause time to speed up and slow down relative to the observer. One of the most memorable plot devices in the film is the powerful influence of the black hole Gargantua on Miller's planet: one hour there is equal to seven years elsewhere, including on Earth and aboard the Endurance. The film chalks this phenomenon up to "relativity," but Thorne goes into more detail, explaining that a black hole's main feature is its event horizon, and that the closer one comes to this horizon, the more gravity increases until it is infinitely strong, sucking in everything that draws near, even light (and Cooper in the Ranger, eventually). Because Miller's planet orbits the black hole at such a close distance to the event horizon, the increased gravity causes time to move more slowly. Albert Einstein was the first to posit that gravity could affect the perception of time by an outside observer, such that with an increase in gravity, time would appear to slow down. Einstein additionally theorized that a person moving at or near the speed of light would appear to stop aging altogether. At one point during the writing of Interstellar, Christopher Nolan proposed the idea of characters traveling faster than light, but Thorne reports that this was one of the only instances in which he vehemently protested, as the notion was so completely impossible. Nolan eventually agreed to nix the idea.
