Interstellar

by David Kyle Johnson

Science Fiction enthusiasts are stereotypically, and perhaps ironically, overly concerned with the accuracy and believability of the science fiction films they watch. From plot holes to scientific accuracy, if there’s something wrong with a science fiction film, they’re likely to tell you about it. Humans couldn’t be batteries, like they are in The Matrix, because we’re too inefficient of an energy source.¹ If Earth’s core stopped rotating, like it does in The Core, we wouldn’t worry about the Earth’s magnetic fields—the oceans would vaporize! ²

The same is true for movies that feature black holes—regions of spacetime with gravity so great that not even light can escape them which are generated by singularities (infinitely dense collections of matter, usually formed by collapsing stars). The difference is, because black holes are so difficult to understand, sometimes it’s the complaints that are mistaken (as we shall shortly see). Still, we’ve come a long way in how accurately black holes are depicted in science fiction; and we can learn a bit about black holes by looking at two films which (arguably) contain the most famous and prominent appearances of black holes in science fiction: The Black Hole (1979) and Interstellar (2014).

The Black Hole

In The Black Hole, the crew of the USS Palomino stumbles across another ship—the USS Cygnus—orbiting a black hole. The crew sits down for space-dinner with the Cygnus’ commander Dr. Hans Reinhardt, they discover he’s a little crazy, one thing leads to another, and … (spoiler alert) they’re all pulled into the black hole.

The science in the film is monumentally inaccurate, especially regarding how it depicts its black hole. From the outside, it looks like a spiral galaxy with a dark spot at the center that dips down like a funnel. This artistic choice, it seems, was inspired by grid representations of the effects of a black hole on spacetime which show spacetime funneling in towards the singularity at the black hole’s center. Indeed, just such representation is the background for the beginning credits of the film.

The reason a black hole wouldn’t actually look like this is because such drawings only represent the effects of a black hole on one plane of spacetime—usually the one along the black hole’s equator. But (a) there are other planes that are also affected and (b) the bending of spacetime these drawings depict occurs outside our visible universe, in a higher dimension. So, although we could potentially see the effects of such bending, we could not see the bending itself.

Now, a black hole can have an accretion disk—a collection of matter that orbits it, like the rings of Saturn, just beyond the black hole’s event horizon (the area of spacetime surrounding the singularity from which not even light can escape). If that disk is being fed by another star, it can kind of look like a galaxy. But the event horizon itself would be oblong…or spherical if the black hole is not spinning. It would never look like a funnel to an external observer.

Interstellar’s Gargantua

The most scientifically sound portrayal of a black hole in science fiction came 35 years later, in Christopher Nolan’s film Interstellar. Its black hole, Gargantua, serves as the center of a new solar system that humanity hopes to colonize, and is most notable for its scientifically accurate appearance—an appearance that was generated by relativistic equations, developed specifically for the movie’s special effects software, by astrophysicist Kip Thorne.³

What about its “look” is so accurate? Two of its visual features stand out. First, it’s not a funnel. Second, the entirety of its accretion disk is visible from every angle—even the part of the disk that’s behind Gargantua (from the camera’s point of view). Visually, it looks like a black sphere with a bright ring of matter orbiting its equator, and another around its top and bottom. But what you are seeing around its top and bottom is actually the far side of the accretion disk; and if you were to orbit Gargantua as its planets do, it would look the same from every angle.

This effect is a result of Gargantua’s enormous mass. The light given off by the accretion disk, just beyond the event horizon can escape—but some of it is bent so drastically by Gargantua’s gravitational pull that it ends up on the opposite side. Light emitted straight away from the disk would escape and be seen on that side of the disk. But light emitted, say at a 90-degree angle from the disk, would be pulled in toward Gargantua, over its top, and then emitted out the other side.

Gargantua’s Time Dilation

Its breathtaking appearance, however, is not Gargantua’s only scientifically sound aspect. It also dilates time accurately.

Einstein’s general relativity shows us that acceleration slows the passage of time. It also shows us that the effects of acceleration and gravity are equivalent. (For example, just like acceleration pulls you back, so does gravity.) Consequently, massive objects like black holes, which produce massive amounts of gravity, also slow time. The closer you get to one, the slower your time would pass. Since your perception would also slow, you wouldn’t notice a difference; but a distant outside observer would see you as moving very slowly. 

A grand example of time dilation occurs in Interstellar when the crew of the spaceship Endurance visits Miller’s planet. It’s orbiting Gargantua so closely that, for every hour that passes on Miller’s planet, seven years pass on Earth. The crew plans to spend only a few minutes there, but ends up spending much more. When Cooper, the film’s protagonist, returns to the Endurance, years of backlogged messages from Earth reveal that his daughter is now older than him.

On his blog, Astronomer Phil Plait argued that this was impossible; a planet close enough to a black hole to experience such extreme time dilation could not be in a stable orbit and would be torn apart by tidal    forces.⁴ But he later had to recant because he didn’t realize that Gargantua was a rapidly spinning supermassive black hole (100 million times the mass of our sun).⁵ This makes its gravitational effects quite different and makes a planet like Miller’s—orbiting where it is, with the time dilation it has, without being torn apart—possible.

What Lies Beyond?

Ironically, The Black Hole may have been more accurate than Interstellar regarding one aspect of black holes: what you would see if you entered one.

Now, this may seem odd if you’ve seen both films. In Interstellar, Cooper enters Gargantua to find a tesseract—a 3 dimensional representation of a four dimensional object (in this case, his daughter bedroom) placed there by “five-dimensional bulk beings.” The idea that all black holes contain tesseracts is not suggested by the movie (and certainly is not entailed by relativity); but if such beings did exist, you could at least imagine them placing one inside.

In The Black Hole, however, what Reinhardt and the crew of the Palamino see is the clouds of heaven and the fires of hell—and that’s ridiculous! Indeed, while Thorne said that Nolan could use his imagination to decide what Cooper would see in Gargantua (since we really don’t know what it would be like), he asked specifically for him to avoid depicting “Satan and the fires of Hades” like The Black Hole did.⁶

The reason I’m suggesting that The Black Hole is more accurate than Interstellar in this regard, however, is because the afterlife is what you would most likely see if you entered a black hole. Why? Because, despite the theories of crazy ol’ Dr. Reinhardt in The Black Hole, there is no way in hell (pardon the pun) you would survive. The gravitational forces of a black hole increase exponentially as you approach it—so much so that, if you were to approach it feet first, the gravitational pull on your feet would eventually be hundreds (even thousands) of times greater than on your head. This would result in something scientists actually call “spaghettification” because it would turn you into something that looks like one long string of spaghetti. You would essentially be stretched to death.

Now, of course I realize that an afterlife is just as non-scientific as five-dimensional bulk-beings and a tesseract; in other words, although they aren’t necessarily contrary to science, belief in either would require faith. Fair enough. But hopefully my point is clear: Surviving a trip into a black hole, like Cooper does in Interstellar, isn’t scientifically sound. Thorne himself even finds it dubious.⁷ But at least when you watch the end of The Black Hole, you can interpret the film in a way that aligns with the scientific facts about black holes: “They all fell into the black hole? Oh yeah…they’re all dead.”

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Endnotes:

1. Wardle, Tammy. “Physics Inaccuracies in the Movie The Matrix.” Prezzi, 6 June 2016,  https://prezi.com/d69bz14uki48/physics-inaccuracies-in-the-movie-the-matrix/

2. Plait, Phil. “Review: The Core.” Bad Astronomy, accessed 25 May 2018, http://www.badastronomy.com/bad/movies/thecore_review.html

3. Thorne was hired by Nolan as a consultant to make the movie as scientifically accurate as possible. For more on how the image was generated, see Thorne, Kip. “The Science of Interstellar.” W.W. Norton & Company, 2014, pp. 83-87.

4. Plait, Phil. “Interstellar Science.” Slate, 6 November 2014, http://www.slate.com/articles/health_and_science/space_20/2014/11/interstellar_science_review_the_movie_s_black_holes_wormholes_relativity.html

5. Plait, Phil. “Follow Up: Interstellar Mea Culpa.” Slate, 9 November 2014, http://www.slate.com/blogs/bad_astronomy/2014/11/09/interstellar_followup_movie_science_mistake_was_mine.html

6. Thorne, Kip. “The Science of Interstellar.” p. 250.

7. Thorne, Kip. “The Science of Interstellar.” pp. 246-7.

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Bio

David Kyle Johnson is a professor of philosophy at King’s College (PA) who specializes in logic, scientific reasoning, metaphysics, and philosophy of religion. He also produces lecture series for The Great Courses, and his courses include Sci-Phi: Science Fiction as Philosophy (2018), The Big Questions of Philosophy (2016) and Exploring Metaphysics (2014). He is the editor of Inception and Philosophy: Because It’s Never Just a Dream (2011), and the author of The Myths that Stole Christmas along with two blogs for Psychology Today (Plato on Pop and A Logical Take). Currently, he is editing Black Mirror and Philosophy.