'Interstellar': Time Dilation And Wormholes Explained

Christopher Nolan’s Interstellar https://www.imdb.com/title/tt0816692/ was a phenomenon in 2014. Set in the future, Earth has been struck by a global crop blight. Former NASA pilot Cooper (Matthew McConaughey) is pulled into a NASA mission to transport the human race to a new planet, via wormhole. Back on Earth, Cooper’s daughter, Murph (Jessica Chastain), attempts to complete an equation that will allow this mass-transport of humanity from Earth. Many scientists praised the film, particularly for its depiction of black holes. In this episode co-hosts Regina G. Barber https://www.npr.org/people/1082526815/regina-g-barber and Emily Kwong https://www.npr.org/people/767284140/emily-kwong talk about Interstellar with Star Trek scientific advisor and astrophysicist Erin Macdonald https://www.erinpmacdonald.com/. They walk through wormholes, black holes and all the ways space-time stretches in the film. Interested in more on the science behind science fiction? Email us your question at [email protected] mailto:[email protected] – we may feature it in an upcoming episode! Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave http://plus.npr.org/shortwave. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

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• 0:00Speaker 00

  This message comes from Capella University. That spark you feel? That's your drive for more. Capella University's FlexPath learning format lets you earn your degree at your pace without putting life on pause. Learn more at capella.edu.

• 0:15Regina Barber?

  This episode contains spoilers to Interstellar, a film that came out over a decade ago. You've been warned.

• 0:21Emily Kwong?

  You're listening to Short Wave from NPR.

• 0:26Regina Barber?

  Hey, Short Wavers. Regina Barber here.

• 0:28Emily Kwong?

  And Emily Kwong. And about a month ago, I asked Gina what I thought was an innocent question. Simply, have you seen Interstellar?

• 0:38Speaker 03

  We must confront the reality of interstellar travel.

• 0:45Regina Barber?

  The movie about a dying Earth and NASA's plan to find humanity a new home in another galaxy. This Christopher Nolan movie has haunted the astrophysics field for the past decade.

• 0:54Emily Kwong?

  Yeah.

• 0:55Speaker 04

  The tiniest synopsis I can give of Interstellar is that Christopher Nolan learned about relativity.

• 1:03Emily Kwong?

  That is Erin McDonald. She's an astrophysicist who has studied spacetime and how it bends. Now Erin is the official scientific advisor for the Star Trek franchise.

• 1:12Regina Barber?

  Dream job.

• 1:12Emily Kwong?

  So she knows a thing or two about movie representations of physics.

• 1:16Regina Barber?

  Yeah.

• 1:16Emily Kwong?

  And Gina, until recently, I had no idea this was a Christopher Nolan movie and that he and his brother Jonathan Nolan consulted with astrophysicist Kip Thorne, who was an executive producer on the movie.

• 1:28Regina Barber?

  Yeah, Kip Thorne, he's a big deal in the field. He contributed to the LIGO detector, which led to the first detection of gravitational waves. And when I taught physics at the college level, like, all of my students begged me to watch this movie.

• 1:42Emily Kwong?

  And here I am begging you to re-watch it. Lucky you. It's 2 hours and 49 minutes.

• 1:48Regina Barber?

  It's so long. I do like the beginning. Go back to bed, then.

• 1:52Emily Kwong?

  I thought you were the ghost.

• 1:56Regina Barber?

  Okay, this is gonna come back. Emily, pay attention, this is a bookshelf.

• 2:00Emily Kwong?

  It's covered with dust. That's concerning to me.

• 2:02Regina Barber?

  It's disgusting. I do actually really like the beginning. The ending, I didn't enjoy as much.

• 2:09Emily Kwong?

  I like the ending.

• 2:11Regina Barber?

  But I really could respect the science in it. Like, the most accurate depiction of a black hole in Hollywood history that was in this film.

• 2:18Emily Kwong?

  Oh, cool.

• 2:19Regina Barber?

  And the time dilation, you know, the idea that time can slow down and speed up depending on how space is stretched or squeezed, like the idea that time slows down near a black hole. That was pretty accurate.

• 2:36Regina Barber?

  Today on the show, science fact, not fiction. We go through the real physics in the film Interstellar.

• 2:42Emily Kwong?

  Specifically, how the stretchiness of spacetime can make astronauts age differently and what gravity has to do with it all. I'm Emily Kwong.

• 2:50Regina Barber?

  And I'm Regina Barber. You're listening to Short Wave, the science podcast from NPR.

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  This message comes from Mint Mobile. Ditch overpriced wireless and get premium wireless for less. Go to mintmobile.com/switch to see which plan works for you. This message comes from Capella University. You know that feeling when there's a spark building inside you, that you were meant for more? That's your own drive, pushing you towards what's next. Capella University gets that. With their FlexPath learning format, you can set the pace and earn your degree without putting life on pause. You've built experience and know what you're capable of. Now, this is your time to turn that momentum into more. The only real question is, what can't you do? Learn more at capella.edu.

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• 4:28Regina Barber?

  Okay, so this movie, Interstellar, starts with a blight killing all the crops. So the human race is eventually going to die on Earth because we don't have anything more to eat. Em, did you like when this movie started basically with this environmental take?

• 4:46Emily Kwong?

  I mean, they're doing two things really well. They're showing what the Dust Bowl of the 30s might have been like through the soil erosion and the big storms whipping through the buildings and making all the plates dirty. And I learned this later, the footage of everyone except the main character was from a Ken Burns PBS documentary. Those are actual Dust Bowl survivors.

• 5:12Speaker 06

  I guess I can't describe it. It was just constant, just that steady blow of dirt.

• 5:18Regina Barber?

  Wow. Wow. I got a feeling it was that, too. And Erin, how did you feel about this as somebody who really knows a lot about the physics in this movie, but it starts with this really bleak...

• 5:31Emily Kwong?

  Farming crisis.

• 5:32Regina Barber?

  Farming crisis, yeah.

• 5:34Speaker 04

  Yeah, I mean, my father's a meteorologist and an environmentalist. And so I've always grown up with conversations about climate change and global warming.

• 5:43Regina Barber?

  Wow.

• 5:44Speaker 04

  I guess for me, I really appreciated how it showed what our future could look like, and it did feel really real. I wish it had been more explicit about being climate change and less about a blight. You know, because I think it was, yeah, it was very... Kind of shied away from it.

• 6:01Emily Kwong?

  That's true.

• 6:02Regina Barber?

  And then, so, we, in the beginning of the movie, we think NASA is not there. People don't believe in the moon landing, and then-

• 6:09Emily Kwong?

  We were shocked by that. Gina and I turned to each other, we're like, "They got rid of the moon landing?" And it all, and they, and they did it without even blinking, those teachers.

• 6:18Speaker 04

  That was not-

• 6:18Regina Barber?

  Oh my gosh.

• 6:19Emily Kwong?

  No.

• 6:19Regina Barber?

  Okay. Okay, so, we, we find out that NASA is indeed not dead, and that Matthew McConaughey's character is gonna pilot the ship through a wormhole.

• 6:29Emily Kwong?

  That's near Saturn. That's been placed there by some aliens. And they start talking about this thing called spacetime. What is spacetime?

• 6:39Speaker 04

  Right. Spacetime as a concept really is just our universe.

• 6:47Speaker 04

  We live in a four-dimensional universe of space and time. We have three dimensions of space. Uh, we can move forward, back, left, right, up and down, and we have control over that. And then we also move forward in time at one second per second, and we don't have any control over it.

• 7:03Emily Kwong?

  No.

• 7:03Speaker 04

  But that's like, literally how our universe is structured. And so, um, when we talk about spacetime, we're just talking about our universe, our space and our time that we're all experiencing.

• 7:18Regina Barber?

  But they're the same, like, not the same thing, but they are, like, part of something, of a whole.

• 7:24Speaker 04

  Exactly, yep.

• 7:26Regina Barber?

  But when we start thinking about this wormhole in Interstellar, they have this great analogy, and we're looking at this wormhole, and theoretically, one side is a black hole and one side is a white hole. And there's this, like, great scene in the movie, which, um, explains why this wormhole looks spherical. Uh, Dr. Romilly, he draws, uh, two X's on a piece of paper, and he connects them with a line.

• 7:50Speaker 07

  So a wormhole bends space like this, so you can take a shortcut through a higher dimension.

• 7:56Regina Barber?

  So he folds the paper in half, and he lines up the X's so they're right on top of each other. And then he punches the X's with his pen, creating a hole.

• 8:05Speaker 07

  That's a circle in three dimensions.

• 8:08Speaker 08

  Sphere. Exactly. Spherical hole. But who put it there?

• 8:14Emily Kwong?

  Do you think a wormhole could exist in real life?

• 8:17Speaker 04

  Mathematically, they could exist. I would argue that we just don't have any mechanism for how they would form.

• 8:26Emily Kwong?

  And then, why was it so great? Wonderfully done in the film.

• 8:30Speaker 04

  What was so great in the film that they're visualizing, because we always think of it being like a hole or a funnel, you know, that we're looking at. But it's not. It's we're in three dimensions of space, you know? And so you have to take that funnel and then extend it in all directions, which is really hard for us to conceptualize because of the way we try to describe spacetime by using that sheet and picturing wormholes or black holes as funnels and tunnels that you're able to travel through. But it would look spherical, basically. And that's how they portrayed it in the film brilliantly.

• 9:12Speaker 04

  And even them going into it and just seeing what we call gravitational lensing, where the light behind the wormhole is getting bent around and warped and distorted from this gravitational object, from this wormhole, was fantastic.

• 9:27Emily Kwong?

  Yeah. Erin, the other thing we really want to ask you about is the time dilation part of the movie. Specifically, when the team visits the planet next to a black hole, Miller's planet, and time is such that every hour on Miller's planet equals seven years on Earth. Why would being on a different planet change time itself? And how does that relate to gravity? And our own planet?

• 9:51Speaker 04

  Yes. Yeah. So gravitational time dilation is what we call it. And it is a real thing. It's actually the most practical application of general relativity we have right now. Our GPS system uses this idea of time dilation. So we are on Earth's surface. We are deeper in Earth's gravity well than GPS satellites. And so GPS satellites experience time slightly faster than we do, but it's like fractions of a nanosecond.

• 10:19Emily Kwong?

  Is that because the gravity is pulling stronger on us?

• 10:22Speaker 04

  Yes.

• 10:22Emily Kwong?

  So it's slowing things down? We're in the bent part more. Oh.

• 10:27Speaker 04

  Yeah.

• 10:27Emily Kwong?

  Of spacetime.

• 10:30Speaker 04

  So it's, it's again, it's like fractions of a nanosecond, but it matters enough for GPS precision if I'm on one side of the street or another. That, that does make a lot of difference.

• 10:41Speaker 04

  What they do such a good job of in the film, I think, is just showing how it works and they do it right. Where I do think it gets a little confusing is it's like, the planet itself isn't the source of this time dilation. It's the black hole that it's orbiting.

• 10:58Emily Kwong?

  That it's next to. Oh, the black hole pulling on the planet makes this time slow. They make it seem like the planet itself is doing that.

• 11:05Regina Barber?

  No, see, the planet's in the bendy part, too.

• 11:07Emily Kwong?

  Oh.

• 11:08Regina Barber?

  The stretchy part.

• 11:09Speaker 04

  It's so close to the black hole.

• 11:11Regina Barber?

  Yeah, in the sheet, or really like fabric analogy, you know, this planet is like a bowling ball on that fabric and it's so heavy that's bending spacetime and that's going to slow down time, right? It's going to dilate it. And there is another way to dilate time, right?

• 11:29Speaker 04

  Yeah. So another way that we can talk about time dilation is through traveling at great speeds. And again, space and time are intertwined. And so as you're moving really fast, it kind of is like shrinking together. And so you're experiencing it differently than people who are not moving at those speeds. But that is what we call special relativity. So special relativity has to do with moving fast. General relativity has to do with gravity and mass and the distortion of spacetime.

• 12:01Emily Kwong?

  I never understood the difference. Got it.

• 12:05Speaker 04

  Neither did the movie.

• 12:09Emily Kwong?

  Before we go, we just got to talk about that black hole, Gargantua. We, I know, I've read enough to know that it was basically the most accurate black hole depicted by Hollywood in its time.

• 12:21Regina Barber?

  Beautiful.

• 12:22Emily Kwong?

  It was beautiful.

• 12:23Speaker 04

  Yes. We have since then actually imaged black holes and their event horizons, both in our own galaxy and in M87, which is another galaxy. And we were able to kind of see this fuzzy ring. And you can actually kind of see how the interstellar black hole, like if you zoomed back enough, it would look the same, which is really, really cool.

• 12:46Emily Kwong?

  Wow. What an accomplishment for the scientists.

• 12:52Speaker 04

  Yes, the story aspect of him falling into the black hole, uh, which really is like the wormhole or they connect him to the wormhole. Like it becomes a wormhole. The way I kind of read it is that he entered a higher dimension through the black hole.

• 13:10Emily Kwong?

  But then the spaghettification happens where Matthew McConaughey is supposed to get stretched and wouldn't that kill him? Why does he not die? And what do you think of the spaghettification part of the movie?

• 13:23Speaker 04

  You're absolutely right. Spaghettification should have happened. That is a technical scientific term for when you are falling into that gravity. Well, that's steep, steep, heavy, heavy bowling ball that's pulling down the trampoline. Eventually you're going to reach a point where your feet is are experiencing higher gravity than your head and that you're going to get stretched apart. Much like his ship got torn apart, but then also he should have been torn apart and he wasn't and it was weird. Uh, and then he was able to experience all time and space in his daughter's bedroom.

• 13:56Emily Kwong?

  And it was love.

• 13:57Speaker 04

  It was.

• 13:59Emily Kwong?

  And it was love. So Erin, do you think this, this film did a good job with science communication as, as like something to kind of help people understand what accurate science fiction is?

• 14:13Speaker 04

  I have a hot take on this and I think the film succeeded from a science communication standpoint in that people were curious about relativity. They were curious about astrophysics. They were curious about these things that they had never understood before. They were the film fails epically and I only think this now.

• 14:29Emily Kwong?

  I love this.

• 14:30Speaker 04

  10 years later, after it came out in our current climate, I think it made people distrust science, scientists more. I think it made people distrust scientists more and that's because

• 14:41Emily Kwong?

  Why?

• 14:41Speaker 04

  The scientists in the film, everyone who was purely a scientist was duplicitous.

• 14:47Emily Kwong?

  Oh, you're right.

• 14:48Speaker 04

  Motivation.

• 14:50Emily Kwong?

  You're right. Yeah. Just got chills.

• 14:52Speaker 04

  Yeah.

• 14:52Emily Kwong?

  You're right. But Murph is not duplicitous. She's the only one. She does light her brother's corn.

• 14:57Speaker 04

  But again, though.

• 14:58Emily Kwong?

  She does. She is duplicitous too.

• 15:01Speaker 04

  Like everyone is, they're all kind of out for their own agenda.

• 15:04Emily Kwong?

  You're right.

• 15:05Speaker 04

  No one was just in the science for the sake of the science, except for maybe the guy who was left behind. Yeah.

• 15:12Emily Kwong?

  Romilly. Wow. This is true. Erin, you know what? You know what? We have to write Christopher Nolan a letter. He's got to be a little more thoughtful.

• 15:21Regina Barber?

  Let's, let's hope he listens. Yeah.

• 15:27Regina Barber?

  Erin, Emily, thank you so much. I'm so glad we all watched this movie again and we got a chance to talk about it. Thank you so much for coming to talk to us. Yeah. Thank you. I really appreciate it. It was fun.

• 15:42Regina Barber?

  This episode was produced by Rachel Carlson. It was edited by our showrunner, Rebecca Ramirez, and fact-checked by Tyler Jones. Jimmy Keely was the audio engineer. Beth Donovan is our senior director and Colin Campbell is our senior vice president of podcasting strategy. I'm Regina Barber. And I'm Emily Kwong. Thanks for listening to Shore Wave from NPR.

• 16:15Speaker 05

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