Neil DeGrasse Tyson Separates Fact From Fiction In 'Interstellar'
As you may be aware, there's a hot new space movie now in theaters — Interstellar. Here's the premise: It's just a little bit in the future, conditions have become pretty horrible on Earth and some astronauts head out in search of a new planet for humans to inhabit.
Astrophysicist Neil deGrasse Tyson has been tweeting about the science behind Interstellar. In an interview with NPR's David Greene, Tyson goes beyond those tweets, deep into wormholes, relativity and even some spoilers. Here's the non-spoiler version of what he had to say. To find out what Tyson thinks about the plausibility of the film's ending, click the audio link at the bottom of the page.
On wormholes, which the astronauts travel through in search of a habitable planet
A wormhole ... is a science fiction writer's favorite way to get from one place to another because you get to bypass the speed limit imposed by the speed of light: 186,000 miles per second. And that's really fast for anything we would normally encounter in everyday life, but if you want to cross the galaxy, you would be long dead before you got there.
And so a wormhole is a literal and figurative shortcut through the fabric of space. And you take your destination, wherever it is, warp the space between you and it. You bend it back on itself and then you cut a hole out of your dimension, through a higher dimension and reappear in the dimension you just left.
It's like taking a sheet of paper and you want to get from one edge to another. But fold it over, and then you can bring the top part of the paper as close as you want to the bottom part of the paper, but you have to leave the paper to make that transition.
The math and the physics of it is sound; it's derived from Einstein's special theory of relativity. But we don't know how to make one, and even if we did make one, the equations show that they're unstable and they would collapse upon you if you tried to go through. So, that's where the science fiction comes in.
On the film's representation of relativity, which involves time slowing down for the astronaut explorers as compared to time on Earth
You can run the equations of general relativity and, when you run those equations, what you learn is that if you are in the presence of a strong gravity, you will have noticeable effects on how slow your time ticks, relative to anybody else who is looking at you from the outside.
And their ratio of how slowly they aged versus everybody else was extreme. You can find strength of gravity strong enough to equal what that difference in time ticking rates would be — you could find one and it is extreme. But they made it clear this is a planet orbiting a black hole. So, there it is. It's a time dilation effect, it's called — and this is real, by the way. ...
Our GPS satellites are farther away from Earth's center of gravity than we are. We are deeper in the Earth's gravitational well than are the satellites — that's the inverse way of saying that. So time ticks more slowly for us than the GPS satellites and the designers of the GPS satellites knew this. And so the time that they send to us, to all of our devices, [is] pre-corrected for the effects of general relativity so that we, on Earth, in a different time dilated place, will have the correct time for our world.
DAVID GREENE, HOST:
You might know there's a new space movie out. It's called "Interstellar." Here's the setup without giving away too much. It's a little bit in the future. Things are looking really bad on Earth. Some astronauts go out exploring for a new planet to move to. And when a movie like this comes out, we like to do a reality check with our favorite science-fiction fan, astrophysicist Neil DeGrasse Tyson, director of the Hayden Planetarium in New York City. He is on the line with us. Great to have you back, as always.
NEIL DEGRASSE TYSON: Thank you. Thank you.
GREENE: So trying not to give too much away - no spoilers. In this movie, these astronauts are searching for a new home for humanity. And they use this favorite sci-fi method of transportation - a wormhole. What exactly is that?
TYSON: Well, a wormhole, as you noted, it's a science-fiction writer's favorite way to get from one place to another because you get to bypass the speed limit imposed by the speed of light. And that's really fast for anything we would normally encounter in everyday life. But if you want to cross the galaxy, you would be long dead before you got there. And so a wormhole is a literal and figurative shortcut through the fabric of space. And you take your destination, wherever it is, warp the space between you and it, but you bend it back on itself. And then you cut a hole out of your dimension through a higher dimension and reappear in the dimension you just left.
TYSON: It's like taking a sheet of paper, and you want to get from one edge to the other, but fold it over.
GREENE: I'm doing that right now. I'm taking the notes I have here and just folding the piece of paper. And I just push a hole through it, and then I can...
TYSON: Get that wormhole going in your notes. (Laughter) That's right.
GREENE: Could you and I in theory really do this and survive as humans?
TYSON: The math and the physics of it is sound. But we don't know how to make one. And even if we did make one, the equations show that they're unstable and that they would collapse upon you if you tried to go through. So that's where the science fiction comes in.
GREENE: That sounds bad - the collapsing.
TYSON: Yeah. Yeah. It's really bad. I hate it when that happens.
GREENE: Once they made it through the wormhole and found these other potential planets to move humanity to, you in a tweet suggested you weren't impressed with these planets. You said Mars right next-door looks way safer than these planets they travel to. Why do you say that?
TYSON: (Laughter) Yeah. No, I thought the planets they portrayed in "Interstellar" - you know, they were kind of borderline. It's like I don't know if this is where I want to live. And they still need their spacesuits. And so Mars is way closer, and you need your spacesuit there - and looked kind of more interesting than some planets they showed there. So you're going to go - you're going to cross the galaxy and land in a place that's not even as good as Mars?
GREENE: Let me ask you one more question. The astronauts spend a very short amount of time on one planet. But in that short amount of time, years go by elsewhere, including on Earth. Is that relativity? And if so, did they nail it?
TYSON: Yes. If you are in the presence of a strong gravity, you will have noticeable effects on how slow your time ticks relative to anybody else who's looking at you from the outside. And their ratio of how slowly they age versus everybody else was extreme. But they made it clear this is a planet a orbiting a black hole. It's a time dilation effect, it's called. And this is real by the way. Our GPS satellites are farther away from Earth's center of gravity than we are. So time ticks more slowly for us. And so the time that they send to us, to our - all of our devices, are pre-corrected for the effects of general relativity. So that we on Earth, in a different time-dilated place, will have the correct time for our world.
GREENE: So we know it exists. It's just a very extreme form in the movie because of this black hole.
TYSON: Precisely. It's an extreme form.
GREENE: Neil DeGrasse Tyson is host of Star Talk Radio - a rival radio show. He's director of the Hayden Planetarium in New York City. And you're like a Twitter machine. Remind us where people can follow you.
TYSON: Oh, thanks. It's just @NeilTyson, N-E-I-L-T-Y-S-O-N. Thanks. Yeah. I mean, I don't - don't come to me as a news source. I'm just sharing with you my brain droppings that without Twitter, they would just - I would think it, and they would just get lost.
GREENE: Well, we always love having your brain droppings on our program.
TYSON: (Laughter) All right.
GREENE: And you can hear our full conversation with Neil DeGrasse Tyson with a ton of spoilers at npr.org. Transcript provided by NPR, Copyright NPR.