Science Fiction

Neil deGrasse Tyson Breaks Down ‘Interstellar’: Black Holes, Time Dilations, and Massive Waves

The acclaimed astrophysicist, host of The Cosmos, and director of the Hayden Planetarium discusses what Christopher Nolan’s film got right and wrong. [SPOILERS]

11.11.14 6:55 PM ET

“My films are always held to a weirdly high standard,” filmmaker Christopher Nolan told The Daily Beast. It is, however, a high compliment for a blockbuster space odyssey like Interstellar to earn the right to be analyzed on a scientific level; after all, films like Star Wars and Star Trek are never held up to such scrutiny.

Nolan’s Interstellar invites scientific critiques via the participation of theoretical physicist Kip Thorne, who not only served as a script advisor and executive producer on the film, but also released a companion tome, The Science of Interstellar, explaining the heady concepts employed in the movie.

For the uninitiated, the film is set on a future Earth whose crops (save corn) have been wiped out by a mysterious blight. A farmer and ex-astronaut, Cooper (Matthew McConaughey), is tasked with leading a NASA mission through a wormhole to another galaxy in order to investigate three potentially inhabitable planets for colonization. The first planet they land on is close to a supermassive black hole, dubbed Gargantuan, whose gravitational pull causes massive waves on the planet that toss their spacecraft about. Its proximity to the black hole also causes an extreme time dilation, where one hour on the distant planet equals 7 years on Earth. On the second planet, they encounter a marooned astronaut named Dr. Mann, and a fistfight ensues. And the rest, well, I’ll leave that to you to see for yourself.

To wrap our heads around the science of Interstellar, The Daily Beast reached out to renowned astrophysicist and cosmologist Neil deGrasse Tyson, who also serves as the director of the Hayden Planetarium at the American Museum of Natural History and host of the Fox series Cosmos: A Spacetime Odyssey, to help break down many of the hotly debated scenes in the film.

On Twitter, you praised the way Interstellar handled Einstein’s Relativity of Time and Curvature of Space.

No other film has given as much attention to these topics, and done it so thoroughly. What I should have mentioned is that in the original Planet of the Apes, there’s an Einsteinian time-shift where the Earth astronauts move very far into the future, so Earth went way past the age of humans while they were still themselves. That wasn’t a running premise of the movie, whereas in Interstellar, there’s a constant reminder that the Relativity of Time is a phenomenon to be reckoned with, thought about, and resolved. And the chalkboards in the film with the field equations are legit. Someone put thought into it. It’s the same with the TV series The Big Bang Theory. When they show the chalkboard, it’s always relevant to the theme of that particular show. 

In The Guardian, Dr. Roberto Trotta, a senior lecturer in astrophysics at Imperial College London, pointed out that the “retro rockets” on their spaceship, Endurance, were too small since you’d need “a lot of fuel” to make their galactic voyage.

Well, a couple of things. I’m a fan of Mark Twain for many reasons, and very high on the list is, “First get your facts, then you can distort them at your leisure.” If they have a ship, and it’s obviously a ship we don’t have today, and this movie obviously takes place in the future, and this ship is obviously more advanced than anything we have or have dreamt up, and they have to get through a wormhole, they don’t have to just use engines to get across the galaxy. I’m OK with that. They’re in a ship, it’s in the future, so get over it and move on! I’d also add that if you’re traveling long distances and know which direction you’re headed, you don’t use fuel to get there. You use fuel to give you the proper velocity and direction, and then you turn off your fuel tanks and coast there. That’s how we got to the moon—there was the launch to get us into orbit, and then the TLI (trans-lunar injection) got us out of earth’s orbit and to the moon.

You also seem to be fond of the way the film treated gravity—as opposed to your reservations about the film Gravity.

They clearly gave attention to the circumstances under which they were in zero-g, or transitioning to 1 g with the rotating space platform that they used. It’s not different from what they did in 2001, where they spent a lot of attention on how you would transition from zero-g to 1 g. Because they spend so much attention, it gives you the right to find places where they might have messed up. In 2001, there’s a point in zero-g where he’s sipping liquid through a straw, and then he pulls his lips from the straw and liquid sinks back down the straw into the container—which wouldn’t happen in zero-g. And Gravity got so much right that it earned the right to have us point out what had been overlooked, which I think is a high compliment.

INTERSTELLAR, Anne Hathaway, 2014. ph: Melinda Sue Gordon/©Paramount Pictures/courtesy Everett Collection


Can there actually be massive tidal waves like the one we saw on the first planet they visited?

Initially, I thought, “OK, they have to throw in a wave… that looks gratuitous.” My second thought was, “Well, if it’s a tsunami, the wave actually needs water to be the wave, and they would see the water rush from around their ankles to feed this wave as it came by.” That’s how you know to run. In this, I would later figure out that both of those concerns were unfounded. The planet is deep in the gravitational well of a black hole, and the black hole would surely have very high tidal forces. Also, a “tidal wave” is misnamed—it’s actually a “bulge” of water fixed in space. The bulge is always oriented in the same configuration in space, so you on the solid planet rotate in and out of that bulge. You interpret it as a wave coming towards you and away from you, but what actually happens is you’re rotating from a high tide part of the water to a low tide part of the water. The fact that the waves came every hour or so meant that the planet rotates once ever two of those—because you have two high tides for every rotation. If I were to say that there was something unrealistic about that, it was how spiky the wave was. A tidal bulge would be smoother than that, and they would just rise up, float over the top, and rise back down the way a duck floats up and down as a wave goes under it. This is where they’re taking dramatic liberties to turn the wave into something more menacing, and I don’t have a problem with that.

The time dilation on that planet—one hour equals 7 Earth years—seems extreme. To get that, you’d apparently need to be at the event horizon of a black hole.

Yes. You can calculate where you must be to have that level of time dilation, and it’s extreme. Here’s another case of, “First get your facts, then you can distort them at your leisure.” The straight facts are you’re in the vicinity of a black hole and time goes more slowly, then you mess with that to create dramatic elements for the storytelling. I don’t have a problem with that. In Titanic, when I criticized the night sky it was because there was no night sky at all—it wasn’t even a real night sky, so that failed my Mark Twain criteria.

Would Endurance even be able to fly that close to a supermassive black hole without being disintegrated by the force of it?

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There’s a regular black hole, which is the end state of a high-mass star, which is a relatively small, planet-sized black hole. Then, you have supermassive black holes that are in the center of galaxies and are huge—typically the size of entire solar systems. If you don’t want to be ripped apart by the tidal forces of a black hole, you’d need to move in and around a supermassive black hole, because the larger a black hole is, the shallower the tidal forces. So, a supermassive black hole would have very shallow tidal forces and likely would not rip you apart if you came near it or descended past the event horizon. It’s the stellar mass black holes that would rip you apart if you got too close. In this case, it’s also the stellar mass black holes that would raise the tide so high on the planet. This is where you take some cinematic liberties—you want the drama of the wave, and you get that on a lower black hole, but you want to survive the experience for having been near it. So, there are some liberties taken there.

What did you think of the fistfight sequence between Cooper and Mann on the second planet?

Well, I would’ve thought they were smart enough, mature enough, and emotioned enough that the likelihood of a fistfight on a distant planet would be extremely remote. We know guys get in fights, but most guys most of the time do not get into fights, so you’d think that being a distant planet would be one of those cases where you do not get into a fight. It’s not like on Star Wars in the bar scene where it breaks into a gunfight where Han shot first. You’re on a freaking planet! I thought it was gratuitous and I’m not sure what it contributed to the plot, but I didn’t really understand the plot. You’d need someone to write another book for that.


They also probably wouldn’t need to send people down to the planets, would they? Couldn’t they just send telescopes or robots?

Well, I thought they had originally sent robots and that was a conversation that was held? I’m not trying to make excuses for the film, but as I understood it, they did not know which planet they would go to until they came out on the other side of the wormhole, and that’s not a decision a robot could make because you’re not communicating with the robot through the wormhole. So, humans had to be there to make that judgment once they got across and got the extra data.

Can Cooper actually float through a black hole in his spacesuit, like he does in the film? Would he be destroyed by gamma radiation?

It’s likely that most black holes have no accompanying radiation coming out of them. The ones we see have extraordinary spiraling gas working its way down to the center of the abyss, and you see those when it’s a black hole that has a companion star that’s getting flayed by the source of gravity, and typically, when the companion star swells up to become a red giant and overfills its Roche lobe, which is an envelope around a star beyond which if any of its material drifts past that envelope, its susceptible to falling somewhere else within that orbiting system. So, only when you have spiraling matter down do you get these ferocious, black hole jets. But a star that becomes a black hole all by itself? There’s no reason to think anything harmful would be in its vicinity at all. So he could float through it entirely. The trick would be to go through a black hole and somehow emerge through a wormhole that’s been established that we don’t know how to make, or sustain. That’s where the science “fiction” comes in.

How about the way the film treated the fifth dimension?

Oh, it was awesome. If you go to a higher dimension than our own, it’s entirely allowed to suppose that you have access to your time dimension. Right now, we have access to our three spatial dimensions, so you can occupy any position within your three-dimensional spatial coordinates at any time. In time, we are prisoners of the present forever prevented from accessing our past, or our future. If you go to a higher dimension, its not unrealistic to imagine that your entire timeline would be laid out in front of you no differently than the way our space dimensions are laid out in front of us now, so that you can occupy any point from birth to death in your own timeline. In the tesseract as they call it, which is just a higher-dimensional space system—the tesseract actually has a very specific meaning mathematically, but ever since the Thor films and The Avengers series, “tesseract” is any access you’re going to have to a higher dimension and I’m fine with that. It’s a fresh word to most members of the public, so why not give it a fresh definition? So, he has access to his entire timeline, and it was up to the visualizers to visualize it in some way that it might be. Every direction he looked, time continued infinitely in that direction—and every direction. Every place he floated was that corridor.

It would take you a pretty long time to relay a quantum equation to save the planet via Morse Code, though.

Yeah. One issue I had was that he must have known his library really well to be able to identify the first letters of the names of each book from the back—from the page side, rather than the binding side—to be able to poke the books out. That showed extraordinary memory, and I don’t know any one of us who’d have that talent. And if he can control matter in that dimension, just write down, “Hey, it’s Dad here—I’ve traveled back in time and tell me to not go the hell on this trip!” If he does have access through his daughter’s room through this tesseract, do more than shove books off the shelves. Heck, write a book and put it on the shelf!