A Cosmic Conversation with Kip Thorne

Could you travel back in time through a wormhole? Neil deGrasse Tyson sits down with theoretical physicist and Nobel Laureate Kip Thorne to reflect on discovering gravitational waves with LIGO, the science in the movie Interstellar, black holes, and many more mysteries still yet to be answered.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:01Neil deGrasse Tyson?

  Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now.

• 0:15Neil deGrasse Tyson?

  This is StarTalk. I'm your host Neil deGrasse Tyson, your personal astrophysicist. And today, we're featuring one of our one-on-one conversations, this time with Professor of Theoretical Physics, Kip Thorne. Kip Thorne, welcome to StarTalk.

• 0:34Speaker 01

  A pleasure to be with you Neil.

• 0:35Neil deGrasse Tyson?

  Oh my gosh, we are coming from your home office in Pasadena, California.

• 0:42Speaker 01

  It's a wonderful office. My son designed this part of the house and built it, and my brother designed and built all the furniture.

• 0:51Neil deGrasse Tyson?

  These are really useful people to have in the family.

• 0:54Speaker 01

  It's a wonderful family to be in. They're the practical ones.

• 1:00Neil deGrasse Tyson?

  I've actually known you for some time, not that we were beer drinking buddies, but...

• 1:04Speaker 01

  I think we've drank beers together in the Canary Islands.

• 1:07Neil deGrasse Tyson?

  Yes, we did. Okay, okay. I stand corrected. But my first exposure to you was you were one of the three authors of this book called "Gravitation", and we used to joke, of course, it was the only book where you learned about it just by carrying it around.

• 1:28Speaker 01

  And I think we probably wrote it before you were born.

• 1:31Neil deGrasse Tyson?

  Possibly, possibly. Although I'm older than you might think. This book is a graduate level treatise on, basically Einstein's general theory of relativity. At the time I acquired the paperback of it, which this is, it's tough making a paperback this thick, but this has the exact proportions of what was then the Manhattan Yellow Pages.

• 1:58Neil deGrasse Tyson?

  So we we we used to call it the phone book.

• 2:01Speaker 01

  Yes.

• 2:01Neil deGrasse Tyson?

  Uh, just affectionately, may I add, may I add. It was brilliantly conceived because I don't know if you could notice on camera. There are tabs or different colors, white and black. And they represent two different paths through the book. One is sort of the elementary path and one the more advanced path, except it all looked advanced to me at the time. So whose idea was this to come up with this book?

• 2:27Speaker 01

  Coming up with the book, I think it was sort of grew out of discussions that Charlie Misner, John Wheeler, my PhD advisor and I had a few years after I got my PhD.

• 2:38Neil deGrasse Tyson?

  Those are the three co-authors there.

• 2:40Speaker 01

  Those are the three co-authors. And so it sort of grew organically and they.

• 2:44Neil deGrasse Tyson?

  That's the best kind of.

• 2:45Speaker 01

  Yes.

• 2:46Neil deGrasse Tyson?

  Projects to have.

• 2:47Speaker 01

  Nineteen sixties and early nineteen seventies.

• 2:50Neil deGrasse Tyson?

  Mm hmm. Yes, I was born before the sixties.

• 2:52Speaker 01

  Oh, really?

• 2:55Neil deGrasse Tyson?

  So on here is Charlie Misner, who's at was at the University of Maryland.

• 3:01Speaker 01

  Yes.

• 3:01Neil deGrasse Tyson?

  And so my copy of this, I had you sign it. And then I spent a year teaching at the University of Maryland. So I quickly went over to his office and had him sign it. But before then, I I started out in graduate school at the University of Texas, where John Archibald Wheeler had they stole him from Princeton, I think, is what that or or lured him from Princeton, I think.

• 3:27Speaker 01

  That's an accurate statement.

• 3:30Neil deGrasse Tyson?

  And so I had all three of them sign it. In fact, John Wheeler's course that he taught in general relativity is where I met my wife.

• 3:38Speaker 01

  Wow.

• 3:39Neil deGrasse Tyson?

  She has a PhD in mathematical physics. So we met in relativity class. Just thought I'd say that.

• 3:44Speaker 01

  Very romantic place to meet, Neil. Very romantic.

• 3:47Neil deGrasse Tyson?

  Very romantic. And John Wheeler used to give out a penny if you caught an error that he committed on the front board. So I have one of his pennies. And I don't remember, it was not a big day. It was like it was a typo or something, the right, the written version of a typo. But so anyhow, it's just delight to meet again with you. And what prompted this was our, you know, you have a lot of accolades, of course, including the Nobel Prize. Okay, but but. More importantly than that, you were science advisor on the film Interstellar.

• 4:29Speaker 01

  Well, I was more than a science advisor.

• 4:31Neil deGrasse Tyson?

  Yes, you were. You were executive producer.

• 4:33Speaker 01

  I was more than an executive producer. It grew out of a treatment that Linda Opes, an ex-girlfriend of mine.

• 4:40Neil deGrasse Tyson?

  Oh, Linda Opes is a big producer of sci-fi films.

• 4:43Speaker 01

  Yeah, she's a big producer of films of a wide variety. But Linda and I dated in 1979, 80, and she was too high-strung for me, and I was too nerdy for her, but we became close friends.

• 4:56Neil deGrasse Tyson?

  Wow. Well, who knows that? Why didn't I know this? Why didn't... No, stop. Why didn't... Where would one learn this? We need a gossip, a physicist gossip column, is that right?

• 5:07Speaker 01

  Yeah. It was some years later, after Carl Sagan, who set us up on a blind date, by the way, that's how we met.

• 5:17Neil deGrasse Tyson?

  Okay.

• 5:18Speaker 01

  Some years later, Linda called me up and said, "Would you like to brainstorm with me for a movie?"

• 5:25Neil deGrasse Tyson?

  Wow.

• 5:26Speaker 01

  And we did, and that's how Interstellar was born.

• 5:30Neil deGrasse Tyson?

  So was that at the time?

• 5:31Speaker 01

  It really was, was the creation of the Nolan brothers, because they took what we had given them, which was basically a structure and a venue for the movie, The Warped Side of the Universe. And they ran with it and changed our story almost completely and made it into a great film. But all the seeds came out of Linda and me.

• 5:55Neil deGrasse Tyson?

  At the time, I mean, you're professor at Caltech, the Richard Feynman professor at Caltech, now emeritus. Caltech is a pretty high-level place. How was it viewed for you to say, "Guys, hold on, I'm gonna make a movie now"? What is that, how does that received by your colleagues?

• 6:17Speaker 01

  I think they were all enthusiastic. Caltech is a different kind of a place than some other more stuffy universities.

• 6:26Neil deGrasse Tyson?

  Oh, okay, okay. I never hung out much at Caltech, so I couldn't judge the mood or the tone.

• 6:32Speaker 01

  Yeah, no, look, we're on the edge of Hollywood. The Hollywood folks come over and, you know, Big Bang Theory was based on Caltech.

• 6:41Neil deGrasse Tyson?

  Right, they didn't call it Caltech, what did they call it?

• 6:43Speaker 01

  They did call it Caltech in the first few episodes.

• 6:46Neil deGrasse Tyson?

  Okay.

• 6:47Speaker 01

  And then they stopped using the Caltech name because the shirts, that's Hollywood speak for the attorneys.

• 6:53Neil deGrasse Tyson?

  Oh, yeah, stiff shirts, yes, yes, up in the office.

• 6:56Speaker 01

  The shirts got scared that they might do something on a screen that the Caltech shirts wouldn't like, and the Caltech shirts might sue the Hollywood shirts. And so they stopped using Caltech name.

• 7:09Neil deGrasse Tyson?

  And in the, in the film, which I adored, what was it called, Real Genius? Real Genius, they were at Pacific Tech, all right? That was the real, the smart kids were. So, of course, Pasadena is in, like, I can't say foothills of Hollywood, but you, you, you have a proximal awareness of this huge industry. And you know that science fiction matters as a, as a genre.

• 7:35Speaker 01

  Well, some of us love it.

• 7:36Neil deGrasse Tyson?

  I love it, I'm, I'm sign up every time. And so Interstellar, I think it introduced many people to authentic gravitational physics for the very first time.

• 7:51Speaker 01

  Well, Interstellar was unlike almost any other film. I think there were precursors in 2001 and In Contact.

• 7:59Neil deGrasse Tyson?

  Yeah, Carl Sagan's Contact.

• 8:00Speaker 01

  Carl Sagan's Contact. And, and the, the point is that... Science, lots of science was baked into that film from the very beginning because of the way it was born and because of the close, close collaboration I had with the Nolan Brothers and built in right from the very beginning.

• 8:19Neil deGrasse Tyson?

  Baked in.

• 8:20Speaker 01

  Baked in and a science that, in which the guideline that we worked from is that nothing in the movie would violate well-established physical laws and all the wild things would at least spring from science in some manner.

• 8:38Neil deGrasse Tyson?

  As any good science fiction story should be, but there's not enough.

• 8:42Speaker 01

  Well, there's nothing wrong with fantasy films, the Harry Potter style, for example. It's just a different genre.

• 8:50Neil deGrasse Tyson?

  By the way, that film, you, you must have known, you said, okay, we're gonna have to help people out. Give a guy a break, okay? They're trying to see the movie, they're trying to follow what's going on. What the hell's happening? Why did the guy get old? Who, why is he younger than his mother? What's going on? And you upped and said, let's help, let's help a person out.

• 9:14Speaker 01

  Yeah, well, I would put it a little differently. It was, I saw it as a superb opportunity to use this film as a motivator, to get people interested or intrigued in science and then there would be a bridge to the science through this book.

• 9:32Neil deGrasse Tyson?

  Admit it, you created a gateway film.

• 9:33Speaker 01

  It was a gateway film, yes.

• 9:35Neil deGrasse Tyson?

  So, The Science of Interstellar, New York Times bestseller, Kip Thorne, with a foreword written by, of course, Christopher Nolan. And it says, spoiler alert, this book explains the fantastic climax and ending of Interstellar.

• 9:50Speaker 01

  And so, let me tell you how that came, this issue came about. Chris said to me early on, I would like, Chris Nolan, I would like to make a film where the ending is as mysterious as the ending of 2001, The Space Odyssey.

• 10:07Neil deGrasse Tyson?

  That's a high bar.

• 10:08Speaker 01

  That's a high bar, but he greatly admires Stanley Kubrick and that film. And so, somewhat later on, as we were talking about the ending, and we had lots of conversations about the ending, he said, well, you can explain the ending in this book that you're planning to write.

• 10:26Neil deGrasse Tyson?

  So he volunteered you to write the book.

• 10:28Speaker 01

  Well, no, I was already planning to write the book, but he identified that as the place where the any will get explained. He was not going to explain the any. He would leave it mysterious.

• 10:38Neil deGrasse Tyson?

  Not in his film. He was pulling a Kubrick on us.

• 10:41Speaker 01

  That's right.

• 10:42Neil deGrasse Tyson?

  In fact, we interviewed Christopher Nolan. If you're an archive diver, we've got a whole episode with Christopher Nolan even before Interstellar was produced. And as we know, so many of his movies, he plays with time in some kind of interesting way. If I remember correctly, he talks about how influential 2001 Space Odyssey was to him back in 1968, that would have been.

• 11:10Speaker 01

  Yes.

• 11:11Neil deGrasse Tyson?

  So let me ask you just a couple of things about the storyline. And I have, I have an issue with it, if I may. I don't know if I ever went public on this, but I figure I'm in front of the man himself. So if I have an issue, it would be here and now.

• 11:26Speaker 01

  You're gonna, you're gonna get turned into a journalist who's challenging me?

• 11:30Neil deGrasse Tyson?

  No.

• 11:31Speaker 01

  Gonna give me a tough time?

• 11:32Neil deGrasse Tyson?

  Yeah, I gotta, I can't, this can't be just all, okay, softball. Play a little hardball. So I guess my issue, we're looking for a planet, again, this is in the themes of the, of the movie. We're looking for a planet like Earth, similar enough to Earth that we can send people there to continue our civilization and our species. Is that a fair characterization?

• 12:01Speaker 01

  Yes.

• 12:01Neil deGrasse Tyson?

  Of a plotline, of the plotline. Okay. And it turns out, there's like a wormhole that can make that happen a little faster. Because otherwise, you don't live long enough to travel the distances with the rockets available to hit those destinations. Okay. I'm just thinking, this blight on the crops that was starving everyone on Earth, requiring that we jump ship, literally jump ship, to go find another ship, another spaceship planet.

• 12:32Neil deGrasse Tyson?

  It seems to me that whatever effort it takes to find another Earth, travel through a wormhole, terraform it, ship a billion people there, whatever that effort is, seems to me to be a bigger effort than just telling the biologist, "Come up with a serum that could fix the crops." Even today, we have full knowledge of crop genomes. Just fix it. Whatever is, just go in there, nip, tuck the DNA, fix it. Isn't that cheaper, easier, faster than wormholing your way off this planet? That's where I'm coming from.

• 13:16Speaker 01

  So you think that all problems can be solved by humans with human technology on a timescale? You have such faith in humans. Come on.

• 13:25Neil deGrasse Tyson?

  So I'm the optimist here.

• 13:27Speaker 01

  Okay, so let me describe. This characterizes how this movie was done. So when it was John and all, and Chris's brother, who came up with the idea that he wanted a blight, or something like that. And so we said, "Okay, we will bring together the best biologists we can, who are experts on these kinds of things." Put together, mostly Caltech biologists. And we had a dinner, and we brought out very expensive wine for them to drink. And we set up a recording.

• 14:06Neil deGrasse Tyson?

  In vino veritas, okay. In truth, there is wine. In wine, there is truth. Yes.

• 14:12Speaker 01

  And so we had a conversation that lasted about three, three or four hours at the Caltech Faculty Club, the Athenaeum, about what would be the best backstory here. There are two types of blights. There are generalized blights that attack lots of crops. And there are

• 14:35Neil deGrasse Tyson?

  Lots of different species of crops.

• 14:37Speaker 01

  Lots of different species of crops. But they are generally fairly benign blights. And then there are blights that are very specific to a particular crop. And they can be very lethal blights that may totally wipe out that species on Earth even. But basically for Earth and life on Earth to survive, you better not have a vicious generalized blight. But according to the biologists that I discussed this with, they didn't know of anything that would prevent the development of a very vicious generalized blight. So that's what occurs in this movie.

• 15:19Speaker 01

  And it's something that biologists have never seen, but they cannot

• 15:24Neil deGrasse Tyson?

  Rule it out.

• 15:25Speaker 01

  Rule it out.

• 15:26Neil deGrasse Tyson?

  Okay, so let me repeat what I think you said. They have vicious lethal blights that attack a species, less lethal generalized blights that cross species boundaries. And they can't rule out a lethal blight that would cross species.

• 15:46Speaker 01

  That's right.

• 15:47Neil deGrasse Tyson?

  And so that's what's happening in this film.

• 15:49Speaker 01

  That's what's happening in the film.

• 15:50Neil deGrasse Tyson?

  Okay.

• 15:51Speaker 01

  And that's what they just, the biologists on Earth in this, in the back.

• 15:56Neil deGrasse Tyson?

  Okay, I'm giving you that, okay.

• 15:58Speaker 01

  Okay, so anyway, this film is full of backstories because of the way we did it. As I say again, it's unlike almost any other film. And that these issues were like that.

• 16:09Neil deGrasse Tyson?

  Were vetted.

• 16:10Speaker 01

  Were vetted by the world's best experts.

• 16:12Neil deGrasse Tyson?

  Right.

• 16:13Speaker 01

  In the process of the writing of the screenplay.

• 16:16Neil deGrasse Tyson?

  Okay.

• 16:30Speaker 02

  I'm Nicholas Costella, and I'm a proud supporter of StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson.

• 16:49Neil deGrasse Tyson?

  Well, I got another one.

• 16:52Neil deGrasse Tyson?

  Okay, you're one for one, all right? When they're on the black hole planet, okay? And then they see this wave coming.

• 17:02Speaker 01

  Okay, it's Miller's planet, the water planet.

• 17:07Neil deGrasse Tyson?

  The planet orbiting Gargantua. Gargantua, okay? The strength of tidal forces are highly sensitive to the distance you are to that which is causing the tides. Highly sensitive, okay? But every illustration I've drawn or taught about tides, they're not so peaky. They're much broader in their representation on a planet. And so there they are, wading in water. But then they see this single wave come. And if it is a single wave, as we've seen with tsunamis, it actually takes water away from what's ahead of it. Because it can't just be water out of nowhere. It's drawing water from its vicinity.

• 17:52Neil deGrasse Tyson?

  So my two issues was, if it's tidal, would it be that peaky? And if it's any kind of wave, how could it still leave the water laying around its vicinity? And then just be that big as it came by?

• 18:04Speaker 01

  So there is a type of wave called a solitary wave on water that was...

• 18:11Neil deGrasse Tyson?

  You could tell me you brought wave people together and had that lunch. It's not what you could talk about.

• 18:15Speaker 01

  No.

• 18:17Speaker 01

  This particular kind of wave was discovered in the 1700s by, I've forgotten who, a physicist in England who saw a boat that was being pulled by horses. And it was just starting up. And it created this wave that traveled down a channel, a canal. And it was peaked like the wave in Interstellar. Though the wave in Interstellar, I have to admit, it was exaggerated. There was some exaggeration in the peak, but it traveled down the channel. It never broke. Most waves in the ocean, they break.

• 18:58Neil deGrasse Tyson?

  Okay, just so we can get the picture, because we're talking about centuries ago. When you say a channel, that would be a channel or a canal.

• 19:03Speaker 01

  A canal.

• 19:04Neil deGrasse Tyson?

  And then there's a tow path on the side.

• 19:06Speaker 01

  A tow path.

• 19:07Neil deGrasse Tyson?

  And then people, and more likely beasts of burden, would drag things through the canal. Because themselves don't typically have currents.

• 19:14Speaker 01

  Drag a barge down the canal.

• 19:15Neil deGrasse Tyson?

  A barge, exactly.

• 19:16Speaker 01

  And so this barge was dragged down the canal. And it was just starting up, and it created this wave that...

• 19:23Neil deGrasse Tyson?

  On the startup.

• 19:24Speaker 01

  On the startup, and it just headed out and just took off and went down the channel. And this guy got on his horse and he followed down the channel. And it went down the channel.

• 19:37Neil deGrasse Tyson?

  You've got a lot of curious physicists. Nothing gets by.

• 19:39Speaker 01

  And it went down the channel for, I don't know, a mile or two, without changing its shape, without breaking.

• 19:47Neil deGrasse Tyson?

  Without breaking.

• 19:48Speaker 01

  And so the theory of these waves is that there are two different effects that cause a wave to steepen or disperse. And the two can balance each other out in a stable sort of a way.

• 20:07Neil deGrasse Tyson?

  And give it longer life.

• 20:09Speaker 01

  And give it a long life. And so, aside from the issue of friction, if there were no friction, it would just live forever and keep propagating in a very stable way. There's a mathematics behind it, something called the Court of Weg de Vries equation, that this is a solution of. But anyway, these waves then...

• 20:30Neil deGrasse Tyson?

  So that equation, I presume, has both kinds of waves in equilibrium somehow represented.

• 20:36Speaker 01

  Yeah, the two effects, the dispersion and the steepening. The steepening is due to nonlinearities. The dispersion is due to the fact that the higher wave, the higher parts of the water travel faster than the lower parts of the water. If you're at the ocean, you see a little tiny wave, it travels quite slowly. You see a big wave, it travels quite fast.

• 20:58Neil deGrasse Tyson?

  And that's why the crest of the wave will actually break before the rest of the wave gets there.

• 21:01Speaker 01

  Yeah, that's right. That's right. Unless that's being balanced out by dispersion, which is...

• 21:10Speaker 01

  Anyway.

• 21:11Neil deGrasse Tyson?

  I love it. No, it's good. Good. No, I'm loving it.

• 21:13Speaker 01

  I'm getting slightly confused. But anyway, the two, the two effects balance each other.

• 21:17Neil deGrasse Tyson?

  Mm hmm.

• 21:17Speaker 01

  And to produce this very stable solitary wave. And so in the movie, but in for this stable solitary wave, the height of the wave is, and I've forgotten the number, but it's something like six times higher than the depth of the water.

• 21:36Neil deGrasse Tyson?

  Got it.

• 21:36Speaker 01

  So there's a problem now in the movie because they're walking around in shallow water and this wave is high. And so it's got to be deep water.

• 21:47Neil deGrasse Tyson?

  Okay.

• 21:48Speaker 01

  But they're, but they're on an island. This is the backstory. Again, there's always a backstory.

• 21:54Neil deGrasse Tyson?

  So they're on a, a subterranean, a sub-surface island.

• 21:59Speaker 01

  Yeah. You gotta read it in my book.

• 22:02Speaker 01

  They're, they're, they're, they're on, they're on an island and this wave diffracts around the island. They hardly notice the island at all. So, so again, there's, it's, it's all explainable, except there is a bit of exaggeration. The, the, in the CGI wave was made somewhat more peaked, somewhat higher than would be.

• 22:30Neil deGrasse Tyson?

  We'll give you that. It's a movie and it's Hollywood. But what you're saying is this wave might have been caused by some effect other than the tidal forces of the black hole.

• 22:39Speaker 01

  Yeah. Well, this wave is caused in fact by the fact that this time is very, is much slowed on this.

• 22:46Neil deGrasse Tyson?

  Yes.

• 22:46Speaker 01

  On this planet. So the planet has been put into the orbit around Gargantua not that long ago is seen on the planet, though it's a long, long time ago is seen from far away. And it is, it's like Mercury, like the moon keeps one face toward Earth or Mercury keeps one face toward the sun due to tidal effects. This planet is distorted by tidal effects and it's swinging back and forth. It has not yet settled down to one face toward the planet. And that swinging back and forth is generating this wave. That's all in the book.

• 23:24Neil deGrasse Tyson?

  He weaseled out of another one. Okay.

• 23:28Speaker 01

  There's an enormous amount of science in that book.

• 23:30Neil deGrasse Tyson?

  I must have missed that when I went through the book. And one last point.

• 23:34Speaker 01

  You didn't study it carefully enough.

• 23:36Neil deGrasse Tyson?

  One last point, we took our show to Oxford recently and I interviewed at Oxford, I think it was a postdoc. And his name is Andrew Mummery, postdoc, and he showed us a recent paper he published. I don't know if you've seen it recently, like within the past 18 months. And he's a theoretical physicist and he alerted me, something I'd never knew. I love the field, but it's not my active professional field, that in the vicinity of a black hole, there is an innermost orbit, because of course you can orbit any source of gravity,

• 24:18Neil deGrasse Tyson?

  even if it's a black hole, but for black holes in particular, there's an orbit within which the orbit is no longer stable and it will spiral into the black hole itself. And according to his calculation, to get the time dilation necessary in this scene with the black hole planet, which was huge, remember they were on the planet for like 15 minutes or whatever.

• 24:43Speaker 01

  Well, one hour on the planet is seven years up at high altitude.

• 24:47Neil deGrasse Tyson?

  Seven years up in their spaceship, okay? And the guy who they left there, he was like gray and unshaven and everything. And we're like, oh my gosh, there's some serious Einsteinian physics going on here. His calculations showed that for that difference, for that extreme difference in time dilation requires that planet orbit so close to the black hole that would be on an unstable, in the unstable zone. And so I just thought I'd tell you that.

• 25:18Speaker 01

  My calculation says otherwise.

• 25:21Neil deGrasse Tyson?

  And where's his Nobel Prize? The other guy?

• 25:25Speaker 01

  The formula is in the book.

• 25:27Neil deGrasse Tyson?

  In this book?

• 25:28Speaker 01

  Yeah, so.

• 25:29Neil deGrasse Tyson?

  So we don't have to go to your graduate textbook for that?

• 25:32Speaker 01

  Well, not for the answer.

• 25:33Neil deGrasse Tyson?

  Okay.

• 25:34Speaker 01

  If you want to derive the formula, that's a lot of work. So let me tell you the story behind this.

• 25:40Neil deGrasse Tyson?

  Oh, so everyone's got a story?

• 25:42Speaker 01

  So Christopher Nolan says to me one day, he says, I want the hero in Cooper, the hero in this movie, to go down onto this planet.

• 25:55Neil deGrasse Tyson?

  Cooper played by Matthew McConaughey?

• 25:56Speaker 01

  That's right. Professor Brand's daughter is played by Jessica Chastain. Christopher Nolan says to me, he says, I want in this movie that one hour on Miller's planet is seven years up at very high orbit or back on Earth.

• 26:15Neil deGrasse Tyson?

  He prescribed that?

• 26:16Speaker 01

  Yeah, and I said to him, that's impossible because the planet will fall into the black hole. He said, go do a real calculation. I've already learned that your off-the-cuff reactions can be wrong, and I should not trust you unless you do a real calculation.

• 26:31Neil deGrasse Tyson?

  There's a good Hollywood producer. Go back and give me the answer I'm looking for.

• 26:35Speaker 01

  Well, and so I went back home and I did a real calculation, and I was amazed that the last stable circular orbit, which is what we're talking about, is if the planet spins fast enough, the last circular stable orbit can have as high a redshift, as high a time difference as you might wish. But that requires.

• 27:04Neil deGrasse Tyson?

  The dilation.

• 27:04Speaker 01

  It requires that this black hole spin extremely close to the maximum possible spin. And so in the book, I give the formula for what is the spin of the black hole that is required to produce a given amount of slowing of time.

• 27:21Neil deGrasse Tyson?

  I did not know that.

• 27:22Speaker 01

  And that, and so that, it's an approximate formula, but it's a formula that can be derived, though it takes a. Fair bit of algebra.

• 27:32Neil deGrasse Tyson?

  Okay, so the one one would just learn about would probably be the lowest stable orbit around a non-rotating black hole.

• 27:38Speaker 01

  That's right.

• 27:39Neil deGrasse Tyson?

  And it's a clean.

• 27:40Speaker 01

  That's a clean problem.

• 27:41Neil deGrasse Tyson?

  Clean problem.

• 27:42Speaker 01

  That's what I was thinking when Chris said, "I want this." But I knew that if I made the black hole spin, that it would get closer. But I couldn't imagine, I could not imagine that nature would provide it

• 28:01Speaker 01

  for a black hole that spins fast enough that they could provide this much of a slowing of time. But it does, it does. At least unless I made a mathematical error. But I don't think that's likely because I use Mathematica.

• 28:14Neil deGrasse Tyson?

  Okay, you had tools to help you do this.

• 28:18Speaker 01

  To check my calculations.

• 28:19Neil deGrasse Tyson?

  Because it was, it's not just an analytic solution.

• 28:22Speaker 01

  Well, it is an analytic solution.

• 28:24Neil deGrasse Tyson?

  But it's very complicated.

• 28:25Speaker 01

  Very complicated, you know.

• 28:26Neil deGrasse Tyson?

  Okay.

• 28:26Speaker 01

  Well, it's a power series solution.

• 28:29Neil deGrasse Tyson?

  In the end, I think our hero character is inside the black hole. We come to understand this. And he has access to a timeline that wouldn't otherwise be available to him. And he sees his daughter's bookshelf.

• 28:46Speaker 01

  Well, he's no longer inside the black hole.

• 28:49Neil deGrasse Tyson?

  Where is he when he's doing this?

• 28:50Speaker 01

  So this is the key thing that's not explicit, that you only understand if you read my book. You didn't read it well enough.

• 28:57Neil deGrasse Tyson?

  Okay, busted. No, I read a lot of it, let me say. I read some of the biology.

• 29:03Speaker 01

  It was a long time ago, too.

• 29:05Neil deGrasse Tyson?

  Yes, okay.

• 29:06Speaker 01

  So when he gets inside the black hole, he is scooped up by a spacecraft that was built by this advanced civilization that provided the wormhole to him, to humanity. And it's called the Tesseract. And the Tesseract is a four-dimensional cube, four spatial dimensions.

• 29:34Neil deGrasse Tyson?

  And that's why in there you saw, I guess, the past and future all kind of simultaneously.

• 29:39Speaker 01

  It's all related to the Tesseract.

• 29:40Neil deGrasse Tyson?

  It felt very higher dimensional.

• 29:41Speaker 01

  Yeah, that's right. So anyway, this Tesseract, he, so let me back up. I'll tell you a story. So early on, when we were working on the film.

• 29:55Speaker 01

  Christopher Nolan said to me, he wanted to take his hero back to Earth, Cooper, back to Earth, by a different route than the wormhole. 10 billion light-years away from the Earth. How's he gonna do it if it doesn't go through a wormhole? He said, "Well, I want to take him back faster than the speed of light." And of course, I say to Chris, "You can't do that. It violates the laws of physics." He says, "Go do a real calculation." I said, "I don't have to do a real calculation." And so, we discussed this for a week. And then he threw in the towel. He said, "Okay, I believe you. And so, what do we do?" And so, I said, "Well, you put him..." He goes inside the black hole.

• 30:40Speaker 01

  He gets deposited on the three-dimensional surface of a four-dimensional sphere. And this four-dimensional sphere is a spacecraft that can go into the bulk, into the higher dimension. And it goes out of the black hole, not through the horizon. It can't do that.

• 30:58Neil deGrasse Tyson?

  Goes through the fourth dimension.

• 30:59Speaker 01

  Up through the fourth space dimension, or what's called the fifth dimension in the movie. His time is the fourth dimension. And goes back to Earth. And the distance back to the Earth is less than the distance between the Earth and the Sun. Even though it's 10 billion light-years inside of our universe, up in the bulk, it's a very short distance. And so, he can get back very quickly.

• 31:21Neil deGrasse Tyson?

  This is the higher-dimensional spacetime in which we are now having this...

• 31:24Speaker 01

  So, he gets back very quickly, riding on the surface of this four-dimensional sphere. He said, "I like it all entirely, except I'm not going... I'm gonna use a four-dimensional cube instead of a four-dimensional sphere. That's a tesseract."

• 31:37Neil deGrasse Tyson?

  Yes.

• 31:38Speaker 01

  And so, that's what happens. And when you see Cooper out there, sort of flailing around at the beginning of the tesseract scene, he's being carried by the tesseract back to Earth. But you don't know that's what's happening until you read my book, by agreement between Chris and me. That's the only way anyone's ever gonna know. So, anyway, he's carried back to Earth. And then, everything is happening when the tesseract is docked in the higher dimension beside his...

• 32:11Neil deGrasse Tyson?

  Giving access to his life in that past time.

• 32:15Speaker 01

  That's right. So, it's docked in his home, in his daughter's bedroom.

• 32:21Neil deGrasse Tyson?

  Okay, so now, he's pushing... Books off the shelves that land on the floor and through some clever cryptographic judgment, he's spelling out words with the first letter of the title of each book. Okay, here's my issue. I had no problems with pessaract, black hole, fourth dimension, five dimensions. How does he know the title of each book from the other side of the book?

• 32:52Speaker 01

  So I don't remember that's how he's actually.

• 32:56Neil deGrasse Tyson?

  He's pushing books out.

• 32:59Speaker 01

  No, I know he's pushing, I know he's pushing.

• 33:00Neil deGrasse Tyson?

  He's pushing books out from this side.

• 33:02Speaker 01

  Yeah, yeah.

• 33:03Neil deGrasse Tyson?

  And all he sees is the other side of the library shelves.

• 33:05Speaker 01

  I guess I had forgotten that he was spelling things out based on the first word.

• 33:12Neil deGrasse Tyson?

  Oh, you forgot.

• 33:13Speaker 01

  I forgot or I didn't know, or you're wrong.

• 33:17Neil deGrasse Tyson?

  So that was one of my, I have an issue there.

• 33:22Speaker 01

  That, that one, I don't know.

• 33:24Neil deGrasse Tyson?

  Oh, okay, okay.

• 33:26Speaker 01

  I don't know.

• 33:27Neil deGrasse Tyson?

  Okay, so you're, you're three for four.

• 33:29Speaker 01

  Yeah, he probably, he probably has a photographic memory.

• 33:35Neil deGrasse Tyson?

  A perfect memory of the other side of the book.

• 33:36Speaker 01

  Yeah.

• 33:37Neil deGrasse Tyson?

  What's this I hear that you can use a wormhole to travel backwards in time? Does the math check out? Does the Einsteinian physics check out? And does that mean I will just show up a younger version of myself and shake my own hand? Is that what you mean by that? Or do I no longer exist in the time that I left for my younger version of myself to see that? And wasn't there, didn't Hawking put forth a time travel prevention conjecture or something? What's going on there?

• 34:16Speaker 01

  So this is all an outgrowth of my phone conversation with Carl Sagan.

• 34:25Speaker 01

  When he was working on the novel for Contact, where he triggered me to start thinking about wormholes. And then, having started to think about wormholes, it became pretty obvious to me rather quickly that if I give my wife, Carol Lee, one mouth of a wormhole, and she carries it at high speed in a rocket ship out into space and then back, and I keep the other worm mouth at home. And if she sees me age by 50 years back on Earth, well, she ages only one year, going out and coming back.

• 35:08Speaker 01

  But if we look through the wormhole at each other, we see each other aging at the same rate. Just imagine, we hold hands and we look at each other's wristwatches. They're ticking away at the same rate. So through the wormhole, we've aged at the same rate, we're the same age. But looking outward through outside the wormhole.

• 35:34Neil deGrasse Tyson?

  Through a normal universe.

• 35:35Speaker 01

  She's aged one year and I've aged 50 years. Something weird has happened. The wormhole has become a time machine. If I just go over and go into her wormhole mouth and come out, I'll meet my younger self.

• 35:50Neil deGrasse Tyson?

  Okay, now Hawking said, "No, we're not going to allow this. There's some conjecture yet to be discovered that'll tell you you can't do that."

• 35:59Speaker 01

  Well, so, you know, we get there, you're going too fast.

• 36:03Neil deGrasse Tyson?

  I'm going too fast, sorry.

• 36:04Speaker 01

  So then, I talked to friends at the University of Chicago. Physics, it's crucial to talk to friends. They tell you where you're all at. They tell you when you made a mistake. They straighten you out. And they pointed out to me that it might be that when the time machine is turned on, it'll self-destruct, basically, they said. I said... I don't understand. They said, "Go do a calculation," so I went and did a calculation. And the issue is, and they had guessed, and basically, that's oversimplified, but they, Bob Garrosh and Robert Wald at Chicago.

• 36:44Speaker 01

  Anyway, it turns out that, at the moment that you can first time travel, the first thing that goes through, it can be vacuum fluctuations of light, say, that enter her mouth of the wormhole, come out of my mouth, and go back, and arrive back at her mouth at the very moment they started out. Now you have twice as much, at the same place in space and time.

• 37:10Neil deGrasse Tyson?

  So this is a runaway?

• 37:11Speaker 01

  So it's a runaway, and so you now have twice as much, and then it goes around again. Now you have four times as much, goes around again. So this runaway builds up.

• 37:22Neil deGrasse Tyson?

  Just like the feedback between a microphone and a speaker.

• 37:25Speaker 01

  Precisely.

• 37:26Neil deGrasse Tyson?

  And it'll just runs away.

• 37:27Speaker 01

  It just runs away. It runs away. And this runaway shows up in the quantum mechanical calculation that I did.

• 37:35Neil deGrasse Tyson?

  You're bumming me out, dude.

• 37:36Speaker 01

  Together with Sungwon Kim, a Korean postdoc of mine.

• 37:41Neil deGrasse Tyson?

  Okay, I want to be a movie director and say, "Go, Kip, go home and figure out how to do this."

• 37:47Neil deGrasse Tyson?

  Give me another, pull another rabbit out of the hat here.

• 37:50Speaker 01

  Well, anyway, we discovered this, Stephen, I think, and one of his, Stephen Hawking, and a student of his, I think, had more or less the same discovery at the same time. Except Stephen probably just did it all in his head, because that's the way Stephen is. Anyway, so then Stephen and I started corresponding about it by email and talking on the phone about it and so forth. It appeared to me, looking at the details of the calculation, that, in fact, the explosion, if I designed the time machine just right, the details of the explosion, this explosion would not be strong enough to destroy the wormhole.

• 38:32Speaker 01

  And Stephen then showed me that I was wrong, and we argued back and forth for a while. Finally, we came to agree that the explosion becomes strong enough that quantum gravity enters in and then holds the answer tightly in its grip.

• 38:51Speaker 01

  And so we won't know whether the time machine self-destructs until we understand the laws of quantum gravity.

• 38:58Neil deGrasse Tyson?

  Let me be fond of obscure here.

• 39:01Speaker 01

  But then we come to the Hawking's cosmic censorship conjecture.

• 39:06Neil deGrasse Tyson?

  That's what it's called.

• 39:07Speaker 01

  Yeah, he, the conjecture that, in fact, in the end, the laws of quantum gravity won't save the day, the wormhole will be destroyed, and any time machine that any advanced civilization makes will be destroyed when they try to turn it on by these vacuum fluctuations, and thereby, as Hawking says, keeping the universe safe for historians of all species.

• 39:34Neil deGrasse Tyson?

  It reminds me of the ultraviolet catastrophe, where you run the calculations, this is going to blow up, how does this even work? And then out comes the discovery of the quantum, which saves the day, right? And this is, it could be a calculation waiting for another branch of physics to open, or another progress in the known branches of physics to resolve.

• 39:58Speaker 01

  We and LIGO and our gravity wave project.

• 40:02Neil deGrasse Tyson?

  We'll get to that, we'll get to that.

• 40:04Speaker 01

  I'll just, just make the remark that we have, we, the LIGO team has, has perfected a technique called quantum precision measurement, which is based on manipulating vacuum fluctuations in order to circumvent the uncertainty principle. And so this business of manipulating vacuum fluctuations is something we do in modern physics.

• 40:29Neil deGrasse Tyson?

  If memory serves, Carl Sagan came up to you and said, for contact, I want to go far distances quickly, how am I going to do it? Can you cook up a wormhole for me?

• 40:43Speaker 01

  Carl phoned me, and...

• 40:47Speaker 01

  Well, back in the eighties.

• 40:50Neil deGrasse Tyson?

  When he's writing the novel.

• 40:51Speaker 01

  When he's writing, when he's writing the novel. That's right. And he said that he wanted, that he has written, he'd already written this, the book, the novel. It was already in page proofs. And he said, I've got this novel, it's in page proof, the publisher's not going to be happy if I change it, but I really need some help to see what the truth is, and then we'll figure out how to deal with this. And he said that I have my heroin traveling through a black hole to get to the Star Vega. And I said, that's rather dangerous. There's a singularity in there.

• 41:35Speaker 01

  There's a singularity in there and you can't get through to get to the Star Vega. So what you actually need is a wormhole. But there is an issue that wormholes implode, they collapse so quick that nothing can get through. But I'll see if I can figure out how to hold the wormhole open just for you, Carl. And so, and so I was, I was going with.

• 42:00Neil deGrasse Tyson?

  It's like rent a physicist. It's like, whatever your needs are.

• 42:05Speaker 01

  So I, so I was getting in a car that, that morning to ride with my former wife to our daughter's graduation up at Santa Cruz. And so Linda was, said, I'll drive and you calculate. So she drove and I calculated, I fiddled around, and then it became fairly obvious. Turns out somebody, other, some other physicists figured this out sooner, but that's the usual thing with me. I figured it out, and then I go see, did people know this before or not? So anyway, I figured out that if you had what I like to call exotic matter.

• 42:48Speaker 01

  That repels gravitationally and you put it inside the throat of a wormhole, that can hold the wormhole.

• 42:55Neil deGrasse Tyson?

  It'll be like pushing it outward.

• 42:57Speaker 01

  That's right. It basically repels the walls of wormhole to hold them open. And it turns out that that will do it. But you have to have enough exotic matter to hold the wormhole open. And I deduced a formula for how much you had to have. And it basically says the following. If you move through the wormhole.

• 43:23Neil deGrasse Tyson?

  The record show he's about to describe how to make a wormhole.

• 43:25Speaker 01

  No, no, only how to hold it open. Only how much exotic matter you have to hold it open.

• 43:31Neil deGrasse Tyson?

  This sounds like a recipe to me.

• 43:33Speaker 01

  So you travel through the wormhole as close to the speed of light as you possibly can. Just very close to the speed of light. And you add up all the energy density all the way through the wormhole of stuff that's in the wormhole. The net has to be negative and then you hold the wormhole open. So it basically means you've got more negative energy than there than positive energy.

• 44:00Neil deGrasse Tyson?

  We have nothing known as exotic matter.

• 44:04Speaker 01

  Oh, yes, we do.

• 44:05Neil deGrasse Tyson?

  What?

• 44:06Speaker 01

  Yeah. And so that.

• 44:08Neil deGrasse Tyson?

  Oh, is this in your basement?

• 44:12Neil deGrasse Tyson?

  What do you mean, oh, yes, we do? What? Okay, what is our exotic matter that would fulfill this purpose?

• 44:20Speaker 01

  So if you.

• 44:21Neil deGrasse Tyson?

  Should we turn off the camera now?

• 44:25Neil deGrasse Tyson?

  Is the government gonna show up on your driveway? Okay, go.

• 44:30Speaker 01

  Well, I learned about this from Yakov Bericevich Zeldovich in Moscow.

• 44:34Neil deGrasse Tyson?

  Zeldovich?

• 44:35Speaker 01

  Zeldovich was one of the inventors of the Russian hydrogen bomb.

• 44:39Neil deGrasse Tyson?

  Okay.

• 44:39Speaker 01

  And I learned this from him.

• 44:40Neil deGrasse Tyson?

  All right.

• 44:41Speaker 01

  He was really brilliant. I learned about about vacuum fluctuations and how important they can be and what how powerful it can be if you can manipulate them. And so if you take a box.

• 44:57Speaker 01

  And you remove everything that can possibly be removed from the box. You're left in the end with tiny fluctuations of everything that possibly could have been in the box. So, electric fields, you have fluctuating electric fields, fluctuating magnetic fields, fluctuating protons, electrons, fluctuating Neil deGrasse Tyson's.

• 45:25Neil deGrasse Tyson?

  So this creates a form of pressure inside the box?

• 45:29Speaker 01

  Well, so, there's vanishing pressure and not vanishing energy due to renormalization. That's a nasty word in physics. But, you can measure energy by whether it produces gravity or not. And although these fluctuations that are there, you can think of them as particles, say particles of light flashing in and out of existence randomly.

• 46:04Neil deGrasse Tyson?

  So, why isn't this not the virtual particles that people speak of?

• 46:08Speaker 01

  So it's virtual particles.

• 46:09Neil deGrasse Tyson?

  It is that, okay. We've spoken about those on our show before.

• 46:12Speaker 01

  Okay, so you have virtual particles.

• 46:14Neil deGrasse Tyson?

  With Brian Greene, in fact.

• 46:15Speaker 01

  So you have virtual particles in the vacuum.

• 46:19Neil deGrasse Tyson?

  Hopping in and out of existence.

• 46:20Speaker 01

  And you can't stop it, you can't prevent it. However, you can take fluctuations from one region and borrow them and put them in another adjacent region for a little while. Or, if you put an electrically conducting sheet, say a sheet of superconducting metal here, then that will suppress the fluctuating electric fields parallel to the metal, because they would create an infinite current flowing in that metal. And that would wipe out the electric field parallel to the metal.

• 47:02Neil deGrasse Tyson?

  Is that an element of the Casimir effect?

• 47:05Speaker 01

  Yes, that's the Casimir effect.

• 47:07Neil deGrasse Tyson?

  It is, yeah. Where you have two parallel plates evacuated between them.

• 47:10Speaker 01

  That's right.

• 47:11Neil deGrasse Tyson?

  And there's a point where they actually feel a whole other force attracting them.

• 47:15Speaker 01

  And so what that force really is, is in the region between them, the vacuum fluctuations are suppressed. And so you have negative energy in between. That energy, negative energy is sucking them together. And you have, you have, you, and they can do work on you if you, you're holding on to these plates. Uh, and they attract each other.

• 47:39Neil deGrasse Tyson?

  You have to put energy to resist it.

• 47:40Speaker 01

  You put energy in as they go, as they go together, they do work on you. The electromagnetic field between two plates in the Casimir effect, uh, is exotic.

• 47:52Neil deGrasse Tyson?

  Okay.

• 47:52Speaker 01

  And so.

• 47:53Neil deGrasse Tyson?

  So you have this in your basement is what you're telling me.

• 47:55Speaker 01

  Yeah, well, I don't have it in my basement, but physicists do this. Uh, let me just say as a side remark, having learned a lot about vacuum fluctuations. Uh, we in LIGO and our gravity wave project.

• 48:08Neil deGrasse Tyson?

  We'll get to that, we'll get to that.

• 48:10Speaker 01

  But I'll just, just make the remark that we have, we, the LIGO team has, has perfected a technique called quantum precision measurement, which is based on manipulating vacuum fluctuations uh, in order to circumvent the uncertainty principle. And so this business of manipulating vacuum fluctuations is something we do in modern physics. And it is something then that you can imagine, you can ask. Can a very advanced civilization manipulate vacuum fluctuations adequately?

• 48:49Speaker 01

  In order to make enough exotic matter inside a wormhole to hold the wormhole open? And so I posed this as a, a question to my physicist colleagues, uh, stimulated by Carl Sagan and why, uh, him wanting to send his heroin through a black hole. I said, no, use a wormhole. Uh, and so we got to hold it open. And so physicist colleagues, please help Carl and figure out, can an advanced civilization do this? And the answer is we still don't know, uh, 40 years later now, we still don't know.

• 49:26Neil deGrasse Tyson?

  Right, well, we're doing magic compared to what anyone thought was possible 50.

• 49:29Speaker 01

  That's right.

• 49:30Neil deGrasse Tyson?

  Years ago, certainly the dawn of quantum physics. We're on the centennial of the decade of quantum discovery back in the 1920s.

• 49:38Speaker 01

  Well, I had, was very close friends with Carl Sagan and I've developed close friendship with Christopher Nolan. Chris has a very different background than me. He knows a lot of science, but he's learned it all by browsing the web. And he knows it well enough to ask me hard questions, much just like you do. But he asked them first, so I have the answers now. So he and have inspired me to ask questions that then I sort of translate to and give to colleagues. My colleagues are smarter than I am. My role is to pass on interesting questions.

• 50:19Neil deGrasse Tyson?

  You're the conduit for this.

• 50:20Speaker 01

  Conduit for interesting questions for my colleagues to work on.

• 50:24Neil deGrasse Tyson?

  So dude, you can't leave well enough alone. Einstein says, maybe there are gravitational waves emanating from major gravitational disturbances in the universe, and you got to go up and find them. But you're not the first to have attempted this, right? At the University of Maryland, there was Weber, I think. What's his first name?

• 50:44Speaker 01

  Joe.

• 50:44Neil deGrasse Tyson?

  Joe Weber, of course.

• 50:45Speaker 01

  Joseph Weber.

• 50:46Neil deGrasse Tyson?

  Who had a cylinder, if I remember correctly, where he was trying to measure whether if a gravitational wave washed over it, he could detect a distortion in the shape of the cylinder, I think was the goal.

• 51:00Speaker 01

  Yeah, well, the gravitational wave would drive vibrations of the cylinder, end to end vibrations.

• 51:06Neil deGrasse Tyson?

  Okay.

• 51:07Speaker 01

  And so he instrumented it to search for changes in the amplitude and phase of vibrations of the cylinder. Cylinder is at a finite temperature, so it's always vibrating a little bit because it's the finite temperature. And so he instrumented it with what's called piezoelectric transducers, transducers that he glued around the middle of the cylinder, that when they were squeezed, they would generate an electrical voltage that he could measure. And they're amazing things, this piezoelectric transducers, just absolutely amazing. You squeeze them a tiny,

• 51:48Speaker 01

  tiny bit, and you get a big voltage out. And Joe Weber was tremendously creative.

• 51:54Neil deGrasse Tyson?

  And I think he was working on that while I was at the University of Maryland. I was there in the 80s. I think he was still working on it.

• 52:00Speaker 01

  Yeah, that's right. So he began working on it in the late 60s, early 70s.

• 52:08Speaker 01

  Announced that he was seeing possible evidence for gravitational waves.

• 52:14Neil deGrasse Tyson?

  There was a lot of skepticism at the time.

• 52:15Speaker 01

  Yeah, that's right. Let me, I'm sorry. He started working out in the late 50s, early 60s, announced in 69 that he was seeing some possible evidence of gravitational waves. And a number of other physicists around the world built similar detectors. And the bottom line in the end, after a period of shaking out, was that others were not seeing gravitational waves.

• 52:43Neil deGrasse Tyson?

  And that's the only way science works. Is one person's result is not a result until somebody else, a competitor, somebody else who uses different wall current, somebody from another country, you need, you need multiple verification.

• 53:00Speaker 01

  But on the other hand, Weber, Joe, he started the field. He triggered this work. The approach, the approach that he invented for searching for gravitational waves was the dominant approach from then until the 2000s. And a number of other research groups built similar detectors and improved them better and better and better over that period of time.

• 53:27Neil deGrasse Tyson?

  On that model.

• 53:27Speaker 01

  On that model, the model. So, so I mean, I have enormous respect for, for what he did.

• 53:35Neil deGrasse Tyson?

  Sure. Now you, now you decided to, you and others, decided to look differently for them.

• 53:42Speaker 01

  Yeah, well, so Ray Weiss, Reiner Weiss, Ray, his friends call him, at MIT, was the primary inventor of an alternative technique that was the technique that ultimately succeeded. And he invented, he wrote.

• 54:00Speaker 01

  He wrote a, a technical paper about the technique that identified all of the noise, kinds of noise that you would have to deal with, and it explained how you, how you might deal with them, and did analysis of how good this detector could be. And he put it all in this paper.

• 54:21Neil deGrasse Tyson?

  There's the recipe. Oh, my gosh.

• 54:22Speaker 01

  It, it was a recipe for, for how to go forward. And he, he wrote this in 1972. And Ray, being Ray, didn't publish this because he, I think he figured you don't publish until you have built one and seen a gravitational wave. So, however, Ray sent copies of this around to all his colleagues. And he put it into quarterly reports of the MIT laboratory in which he worked. And so it, it is probably the most influential non-published paper, certainly that I know of in physics. I mean, it was, it was a tour de force, and it triggered

• 55:07Speaker 01

  the huge effort that actually succeeded.

• 55:11Neil deGrasse Tyson?

  I was fortunate enough to visit the, because there were two LIGO experiments, one in Louisiana and the other one is in

• 55:18Speaker 01

  Hanford, Washington.

• 55:19Neil deGrasse Tyson?

  Hanford, Washington. Why do you have two? Because you can't just have one result.

• 55:23Speaker 01

  Yeah, you're looking for a, an effect that is so small that you wouldn't believe it unless you see it on two independent instruments.

• 55:34Neil deGrasse Tyson?

  There you go. So, you've got these pathways, are they kilometer long?

• 55:40Speaker 01

  Four kilometers.

• 55:41Neil deGrasse Tyson?

  Four kilometers long, evacuated, you send a beam of light that is split from a sink, a beam, a laser that's split, it goes to, these are at 90 degree angles, and they go to the end, they get reflected back, then you rejoin them, and you want to see if their waves line up. And if they line up, then each direction is identical, you can go home. If they're slightly different, then one of these legs experienced a different encounter with the fabric of the space-time continuum than the other did.

• 56:18Speaker 01

  So

• 56:19Neil deGrasse Tyson?

  That's, you know, that's

• 56:20Speaker 01

  So actually, what you want to do is you make them slightly different in the first place. But then, so that means you're saying your laser light in from this direction. Uh, there's a beam splitter where the light gets split in two to go down the two arms. Uh, so the laser light goes in like that. There's this beam splitter, so the light gets split in two into one arm in that direction, the other arm in this direction. Uh, and, uh, then it comes back and recombines in the beam splitter. The laser light was coming in from this direction.

• 56:58Speaker 01

  Uh, uh, but when it recombines, uh, a little bit of light goes out, uh, in a perpendicular direction. So you have a laser here and you have an output over there. And the output direction is the direction that has a signal. And if the, if the length of one arm is shortened and the length of the other arm is in length.

• 57:23Neil deGrasse Tyson?

  And that would only happen because a gravitational wave washed over that.

• 57:26Speaker 01

  That's right. Uh, then you get a change in how much light is coming out to the output.

• 57:33Neil deGrasse Tyson?

  All right, so this, you're trying to find a, a chain, a length difference. And if I remember the materials from the press releases, that is equivalent to one tenth, the diameter of a proton?

• 57:49Speaker 01

  No, it's equivalent to, uh, it's 10 million times smaller than an atom and 100 times smaller than a proton.

• 57:58Neil deGrasse Tyson?

  One one hundredth, this, the diameter of a proton. Meanwhile, all the world is vibrating because everything is at a temperature and, and cool it as much as you want, there's still vibrations and, and somebody is walking down the street. I, I remember being on campus there. Can I call it a campus? That's what it was. And you can, you can detect.

• 58:25Neil deGrasse Tyson?

  Cars on the road a mile away. You have to insulate this. That's half the science done for the experiment. You should get a Nobel Prize for that.

• 58:36Speaker 01

  Well, that's what the Nobel Prize was given for. For that, yeah.

• 58:41Neil deGrasse Tyson?

  To have successfully isolated the effect you're trying to measure.

• 58:45Speaker 01

  So, the way I like to describe it is you're trying to, you're bouncing light off of these mirrors and you're looking for a motion of the mirrors that is 10 million times smaller than the atoms of which the mirrors are made. And, well, the mirrors, the atoms in the mirrors themselves are vibrating because they're at finite temperature. Fine amount is about the same as their size. So, 10 million times smaller than the atoms and 10 million times smaller than the vibrations the atoms are undergoing.

• 59:21Neil deGrasse Tyson?

  So, once again, in physics, there's a phenomenon we're trying to measure, but it's kind of buried and you need a way to get to it. And it seems like half, if not more than half of the effort is how brilliant is your engineer that you've brought on to the task to accomplish this. How good are your tools? It's not just the idea. It's now you gotta make the damn measurement. And it's not obvious. You need very talented people assembled for this.

• 59:54Speaker 01

  Absolutely. And so, that was the issue is how good a team can you put together? So, when I learned of Ray Wyche's idea and I saw, and I knew roughly how strong the strongest gravitational waves would be, I knew already then that it would be necessary to...

• 1:00:18Neil deGrasse Tyson?

  This would be the collision of two black holes.

• 1:00:19Speaker 01

  Collision of two black holes.

• 1:00:21Neil deGrasse Tyson?

  And you can't just summon that up. There has to be real things in the universe that might produce that.

• 1:00:25Speaker 01

  That's right. That's right. So, but based on what we knew about the universe at the time, I was estimating a wave strength that was roughly correct. And it was at that level that you would have to monitor the motion of these mirrors at 10 million times smaller than the atoms in the mirrors. And I thought to myself, that's crazy. And so in this book, which was published in 1973, we went to press just after Ray Weiss wrote his seminal paper. I had not yet really studied that paper fully, but I just knew

• 1:01:10Speaker 01

  that this was crazy. And so it describes in a few words Ray's idea in here. And then it says, I think there's an exercise where it says, show why this is not very promising. Just a mild gentle.

• 1:01:28Neil deGrasse Tyson?

  Because it is a textbook, right?

• 1:01:29Speaker 01

  Yeah.

• 1:01:30Neil deGrasse Tyson?

  You get to declare that.

• 1:01:31Speaker 01

  So it's the students' challenge to show.

• 1:01:34Neil deGrasse Tyson?

  Well, it could not be a very good idea in 1973, but fast forward a half a century.

• 1:01:39Speaker 01

  Right. And so it is.

• 1:01:41Neil deGrasse Tyson?

  1853, flying is not a good idea, right? An essay on why flying isn't a good idea.

• 1:01:46Speaker 01

  Yeah, but that was the central issue. If we worked for a few decades, did we have a shot at success? In 1973, I thought, no, no way. But by 1975, I had turned around. I'd had long conversations with Ray. I'd had long conversations with Vladimir Briginsky, a colleague in Moscow. I'd done lots of calculations of my own. And I came to the conclusion that you had a real shot at success if you put together a superbly strong team and you worked at it for a few decades.

• 1:02:24Neil deGrasse Tyson?

  And you need money. And you were well supported, I think, by the National Science Foundation?

• 1:02:29Speaker 01

  Well, not yet. So at that point, NSF had given Ray $60,000 to get started.

• 1:02:37Neil deGrasse Tyson?

  $60,000?

• 1:02:40Speaker 01

  That's how much he had in the 1970s from the National Science Foundation. He also had some money from the Air Force Office of Scientific Research. I'm not sure how much he had, or he had had that until, until in the Vietnam era, they stopped supporting science due to something called the Mansfield Amendment, American Politics. And that's when NSF picked him up and gave him 60,000. That was a drop in the bucket compared to what was needed. And NSF wasn't about ready to put big money in.

• 1:03:15Neil deGrasse Tyson?

  This required some members of your team to like appear in front of Congress to defend this.

• 1:03:20Speaker 01

  That's, that's, that's correct. And, and, but that was much later. The issue was getting started. And so how did we get started? Caltech is a very different kind of an institution than any other I've ever dealt with. At Caltech, I was able to say, to propose to my colleagues that we get into this field, that we build a experimental program in parallel with Ray Weiss's program at MIT. So my, the Chair of the Division of Physics, Mathematics and Astronomy at Caltech set up a committee to look at it. Committee, I looked at it for about six months, detailed study, came back enthusiastic, said, let's go ahead.

• 1:04:03Speaker 01

  And so Caltech put private money, about $2 million, of its own private money to get started. And that inflated about $12 million today. Private money, when, when nobody else was putting anything in.

• 1:04:19Neil deGrasse Tyson?

  You're right. That's a very different, a very different culture at Caltech.

• 1:04:24Speaker 01

  And once that had happened, and we had brought Ron Drever from Scotland to start the experimental effort, then NSF, and NSF stood up and took notice. They did their own study of this and came up with the same conclusion. They started funding us, us and Ray Weiss, and it became a Caltech MIT collaboration.

• 1:04:49Neil deGrasse Tyson?

  Let's fast forward to 2016, where you make the first detection.

• 1:04:56Speaker 01

  We announced it in 16.

• 1:04:58Neil deGrasse Tyson?

  You announced it in 16. By the way, I would later learn that when I visited the facility in Louisiana. You already had made the detection. And you'd be happy to know that everyone was completely zip-mouthed about it until it was officially... Because I have this huge internet following, right? And people were totally zip-mouthed. I swear I didn't know about it until the press release came.

• 1:05:22Speaker 01

  We were all sworn to secrecy.

• 1:05:24Neil deGrasse Tyson?

  Yes, yes. And so, the confirmation of a first detection came from the second facility built in Hanford. And at that point, you have a time delay because gravitational waves move at the speed of light, correct? So, and Earth is a finite size. And so, all that worked out.

• 1:05:45Speaker 01

  Yeah, yeah. And so, it was just seven milliseconds, seven milliseconds of a second time difference because the waves came up from the south. They entered the Earth around the tip of the Antarctic Peninsula, traveled through the Earth, came up through the Earth. In Louisiana first, and then Washington State second, seven milliseconds later.

• 1:06:10Neil deGrasse Tyson?

  This is...

• 1:06:11Speaker 01

  And then the waves were unaffected by all the matter of the Earth. They just... And they couldn't see the difference between Earth and no Earth. And they couldn't see the difference between detector and no detector. They were very hard to detect.

• 1:06:27Neil deGrasse Tyson?

  Doing their thing. So, what impresses me greatly is here we have a prediction made by Albert Einstein when in 1916 or 15, whatever. Albert Einstein, in a little-known fact, I mean physicists know this, but I don't think the public knows, Einstein laid out the equations for the stimulated emission of radiation, which is the physical foundation of a laser.

• 1:06:51Speaker 01

  Yeah.

• 1:06:52Neil deGrasse Tyson?

  He wrote that down first. And a laser would take a few decades to actually be built into the 1950s. And I'm just saying, here's Einstein predicting gravitational waves, laying the foundation for a laser, and 100 years later, his gravitational waves are found with lasers.

• 1:07:10Speaker 01

  Yes.

• 1:07:12Neil deGrasse Tyson?

  So, these are crumbs spilling off his plate.

• 1:07:15Speaker 01

  Einstein was kind of smart.

• 1:07:18Neil deGrasse Tyson?

  And low and behold, nobody's surprised, the Nobel Prize goes to this project. And you, along with Ray Weiss and Barry Barish, shared the Nobel Prize. What year was that? 2017?

• 1:07:33Speaker 01

  So they apologized to us that they didn't give us in 16 because we didn't announce it until past their deadline for nominations.

• 1:07:43Neil deGrasse Tyson?

  Well, plus, they delay anyway. They're never...

• 1:07:45Speaker 01

  Yeah, well, no, they said it, obviously. It was obvious the prize was going for this. It was just obvious.

• 1:07:52Neil deGrasse Tyson?

  Yeah.

• 1:08:15Neil deGrasse Tyson?

  You can't be a general relativity Einstein guy without being a black hole guy. So forgive me for asking you to retell a story you've probably told a thousand times. But there's some famous bet you made, was it with Preskle, with some other physicist?

• 1:08:36Speaker 01

  Preskle and Hawking.

• 1:08:38Neil deGrasse Tyson?

  And Stephen Hawking. By the way, I was at the University of Texas when Preskle was there. I think he was like a postdoc or something. He was some, he was just starting out. That's how old I am. I'm an old guy.

• 1:08:48Speaker 01

  You're a young kid.

• 1:08:50Neil deGrasse Tyson?

  I'm an old man. So you made a bet, and let me see if I can set the table here. A black hole, once we all agree that they exist, we can ask other questions. When you have something outside the black hole and it falls in, what happens to that information that was contained in that object? Is it gone forever? And is that okay? Because information theory was a whole branch of science, shall I call it science, that was rising up at around the same time. And entropy became a buzzword among many. So what was the bet? And how did it, and how was it ultimately resolved?

• 1:09:34Speaker 01

  So the bet was between Stephen Hawking and me on one side, John Preskle on the other side. It was over whether or not information does get lost in black holes. The background of the-

• 1:09:48Neil deGrasse Tyson?

  And why is that so bad?

• 1:09:50Speaker 01

  Okay, so it's bad because the fundamental laws of quantum mechanics as they are normally formulated. Physicists are widely agreed that quantum physics is fundamental and that quantum physics underlies all of physics.

• 1:10:13Neil deGrasse Tyson?

  It's the most successful theory ever put forth-

• 1:10:16Speaker 01

  Right.

• 1:10:16Neil deGrasse Tyson?

  -of the universe.

• 1:10:17Speaker 01

  And classical physics, where there are not these quantum fluctuations, there are not these probabilities, that arises from quantum physics as an approximation under ordinary, everyday circumstances.

• 1:10:29Neil deGrasse Tyson?

  There are many people who caricature science, physics in particular, by saying, "Well, we used to think classical physics was it, but now we discard it in favor of quantum physics." But that's not true. No, quantum physics absorbed-

• 1:10:46Speaker 01

  Yeah.

• 1:10:47Neil deGrasse Tyson?

  -as well as relativity, general relativity, absorbing Newtonian gravity.

• 1:10:52Speaker 01

  Yeah.

• 1:10:53Neil deGrasse Tyson?

  It doesn't, it's not discarded, it's a bigger understanding, a deeper understanding.

• 1:10:57Speaker 01

  That's right.

• 1:10:58Neil deGrasse Tyson?

  Okay, just want to emphasize that.

• 1:10:59Speaker 01

  That's right.

• 1:11:00Neil deGrasse Tyson?

  Many people get that confused.

• 1:11:01Speaker 01

  And so, quantum physics as normally formulated, as almost universally viewed, has built right into it from the very beginning the fact that information cannot be lost. Now, these words, "information cannot be lost," are a translation into everyday language of something else, which is not everyday language, which says that the evolution of everything in the universe is unitary. And so those are buzzwords that are not part of the normal lexicon.

• 1:11:43Neil deGrasse Tyson?

  Okay.

• 1:11:43Speaker 01

  But I want to say, just to say that, to indicate that there's some very, very extremely precise version of this, of which information is being lost, is a colloquial way of saying it.

• 1:11:56Neil deGrasse Tyson?

  Okay. But it represents a violation of some fundamental tenets of quantum theory.

• 1:12:01Speaker 01

  That's right. Stephen Hawking, back when he was visiting Caltech.

• 1:12:07Neil deGrasse Tyson?

  Who, by the way, we've interviewed for StarTalk in our archives. Check it out.

• 1:12:11Speaker 01

  In 1974, 74, 75, he spent a year in my research group at Caltech. We were very close friends. And he, during that period, he, having discovered something called Hawking radiation, which is a very slow evaporation of a black hole, and emits radiation, slowly evaporates. He then, while he was here, began to look much more deeply at quantum theory and black holes. And he came up with a prediction that information really is lost. And when black holes evaporate, you could form a black hole.

• 1:12:53Speaker 01

  If you waited long enough, much longer than the age of the universe, for normal black holes, the black hole would evaporate, and all the information that went into the black hole would be gone. The black hole would be gone. You just simply lost the information. It no longer is there. And that was complete violation of the normal tenets of quantum mechanics. And yet, he was claiming that that was true. He wrote a paper on this with all the technical details. He couldn't get it published. Because it was, it was so obvious. It had to be wrong, but nobody could see anything wrong in his calculation. And so, he had to fight for more than a year to get it published.

• 1:13:35Speaker 01

  If you look at this paper, you see the submission date.

• 1:13:39Neil deGrasse Tyson?

  As all research papers give you.

• 1:13:41Speaker 01

  Yeah, they give you a submission date, and then you usually have a revised date, and then it's published. There's no revised date. There's a submission date, and the publication date is like nearly a year and a half later. He fought for a whole year, more than a year, to get this thing published. And physicists struggled with this ever since.

• 1:14:05Speaker 01

  So those of us whose roots are in relativity tended to believe Hawking. And those of us whose roots were in, who grew up with quantum mechanics instead of relativity first, those of us who were enamored of relativity tended to believe Hawking. And so Hawking and I made this bet with Preskle, whose roots were in, in quantum physics.

• 1:14:33Neil deGrasse Tyson?

  And he's the junior of you both, right?

• 1:14:35Speaker 01

  He's the junior of us both. He is, he is now the Richard P. Feynman Professor of Theoretical Physics at Caltech. I'm the Richard P. Feynman Physic, Professor of Theoretical Physics Emeritus.

• 1:14:46Neil deGrasse Tyson?

  Emeritus, okay. Young whippersnappers, oh man, don't take your job in a minute.

• 1:14:50Speaker 01

  So I just turned the chair over to Sean. I mean, Sean is brilliant. He's a hell of a lot smarter than I am, a hell of a lot smarter. Anyway, so, so we made this bet. And this was in a period when Hawking was starting to visit Caltech for typically three to six weeks every year.

• 1:15:12Neil deGrasse Tyson?

  Was he yet wheelchair-bound?

• 1:15:13Speaker 01

  Oh, yeah. He'd been wheeled, he was wheelchair-bound going way back to about 1970.

• 1:15:19Neil deGrasse Tyson?

  Okay.

• 1:15:20Speaker 01

  And this is 1990.

• 1:15:23Neil deGrasse Tyson?

  Oh, whoa.

• 1:15:24Speaker 01

  And so this is, we made the bet around 1990.

• 1:15:27Neil deGrasse Tyson?

  So the stage is set, okay? The cage match is set. You and Stephen Hawking, titans in your field, in your subject, conclude, yeah, information is lost. Especially if Hawking radiation, you could evaporate the black hole and everything is gone, there's no, there's no memory of what was there. Preskle is declaring that information is not lost and his roots are deep in quantum physics, which we know has never been shown to be wrong.

• 1:15:57Speaker 01

  And they're both smarter than I am and they both know a lot more about quantum physics than I do. Because we'll return to this, but let me just explain that. Through my whole career, I've thought that the quantum gravity, combining general relativity with quantum physics, was the most important area of physics of all. But I also made a decision when I was very young, I will never work in quantum gravity because the field is too crowded. There are too many smart people there. I will pick... I'm smart enough to pick really important problems that I can solve that nobody else is working on. And they'll only figure out later that I'm right, that those problems are important.

• 1:16:40Speaker 01

  But I won't touch a problem where everybody's working.

• 1:16:43Neil deGrasse Tyson?

  We've got a billion people in the room.

• 1:16:44Speaker 01

  There's just too many smart people.

• 1:16:45Neil deGrasse Tyson?

  Too many smart people in the room.

• 1:16:47Speaker 01

  So anyway, so they have now agreed that information is not lost.

• 1:16:53Neil deGrasse Tyson?

  So Hawking conceded, and by association with you? Or are you still a holdout on this?

• 1:16:59Speaker 01

  No, I'm still a holdout.

• 1:17:00Neil deGrasse Tyson?

  Okay. And what led to this concession? If I understand correctly?

• 1:17:05Speaker 01

  So Stephen, together with a student, was working on an idea for how the information might be recovered. And he basically said that in quantum physics, if you form a black hole and then it evaporates, there's also a tinier probability that the black hole never formed in the first place. And the information sneaks out through the root where it didn't form in the first place. And...

• 1:17:41Neil deGrasse Tyson?

  I'm sorry, that sounds like a cop-out.

• 1:17:43Speaker 01

  Yeah, it does sound like a cop-out. But it's very clever, and it's in keeping with how physics works. But it's not obvious that it's right, but it's conceivable that this is what happened.

• 1:17:58Neil deGrasse Tyson?

  What about the idea? So maybe I've misunderstood. So I've got to go back to see where I've said this, even publicly. I thought, as the black hole evaporates, because the energy, the gravitational energy in the vicinity of a black hole can spontaneously make a pair of particles. And one particle escapes, the other one falls into the black hole. And this just keeps going until there's no black hole left. But the particle that escapes, if you inventory those particles, they're real particles. And... Don't you recover all the particles that went in in the first place?

• 1:18:31Speaker 01

  Well, you recover all the energy.

• 1:18:33Neil deGrasse Tyson?

  But not the inventory of particles?

• 1:18:36Speaker 01

  You don't get the same particles necessarily.

• 1:18:39Neil deGrasse Tyson?

  Okay, then I misunderstood that. I've been wrong. I think I've been wrong. I thought you get particle for particle, they come out, which blew my mind.

• 1:18:47Speaker 01

  I don't think, certainly there's no proof that that's the case.

• 1:18:52Neil deGrasse Tyson?

  Well, of course.

• 1:18:54Speaker 01

  Certainly no proof that's the case. And I don't, and I don't, and I don't think it is the case.

• 1:18:59Neil deGrasse Tyson?

  Okay, okay. Okay, so you guys lost the bet?

• 1:19:03Speaker 01

  Well, no, I.

• 1:19:04Neil deGrasse Tyson?

  Okay, Hawking concedes the bet.

• 1:19:06Speaker 01

  Hawking concedes the bet.

• 1:19:08Neil deGrasse Tyson?

  And what was at stake for this?

• 1:19:10Speaker 01

  The loser will give the winner an encyclopedia filled with information that somehow escaped the black hole. And so.

• 1:19:25Neil deGrasse Tyson?

  So information is the penalty gift.

• 1:19:27Speaker 01

  That's right. So Stephen Hawking conceded the bet at a big international conference on general relativity and gravitation in Dublin, Ireland, in early 2000.

• 1:19:41Neil deGrasse Tyson?

  Were there gasps in the audience?

• 1:19:43Speaker 01

  There were rumors that he was going to concede. And so there was a big ceremony. I played some role in the ceremony, but I didn't concede myself. And so Stephen gave Prescott, who's a big baseball fan, an encyclopedia of American baseball.

• 1:20:03Neil deGrasse Tyson?

  Oh, any kind of encyclopedia?

• 1:20:05Speaker 01

  Yeah, well, that was his idea.

• 1:20:07Neil deGrasse Tyson?

  That's clever.

• 1:20:09Speaker 01

  So anyway.

• 1:20:09Neil deGrasse Tyson?

  And less expensive.

• 1:20:10Speaker 01

  Yeah, I didn't concede for a peculiar reason. That there is an alternative formulation of quantum mechanics in which information could be lost as due to Feynman.

• 1:20:23Speaker 01

  Called a sum over history's formulation. And as I say, I don't work in quantum theory in any deep sort of way. I do in terms of quantum technology, which we needed for LIGO, but that's a separate story. But two of the very deepest physicists in working in quantum theory of my lifetime were Murray Galmon and Jim Hartle. Jim Hartle at Santa Barbara, Galmon at Caltech, and then he moved to the Santa Fe Institute and retired.

• 1:21:03Neil deGrasse Tyson?

  Galmon is credited with proposing quarks.

• 1:21:06Speaker 01

  Yeah, that's right.

• 1:21:07Neil deGrasse Tyson?

  As the fundamental particle of.

• 1:21:08Speaker 01

  So the giants of theoretical physics, when I was a young physicist at Caltech, were Galmon and Feynman, and two colleagues of mine that I enormously respect. So Galmon and Hartle took Feynman's path integral, or sum over history's approach to quantum mechanics, and they developed it further in a form that they could apply it to cosmology, to the universe. And then Hartle has used that to study quantum cosmology, the quantum mechanical description of how the birth of the universe and how it has evolved.

• 1:21:50Speaker 01

  That particular approach to quantum mechanics, Hartle took it and he showed how that approach can deal perfectly well with information loss. And it deals with that, that it arises because of what we call closed time-like curves. There's a certain probability for backward time travel in quantum physics. In this Feynman-Galmon-Hartle approach, there's a certain probability for backward time travel. If you have backward time travel at the quantum level, then you lose information.

• 1:22:35Speaker 01

  And so the elegant mathematical formulation here.

• 1:22:39Neil deGrasse Tyson?

  Quantum physics is so easily this way.

• 1:22:41Speaker 01

  Well, that's not the standard version of quantum mechanics, but that was the version that Feynman and that Hardland-Galman needed in order to do the quantum mechanics of the entire universe and the birth of the universe. So that we're getting into this issue of the birth of the universe and quantum gravity here. And I am rather enamored of this approach, although I don't do it. I just look on the snide lines and admire that these people are smarter than I am and who have the courage to work in a crowded field. But I'm just so impressed with this and with the fact that within that formulation,

• 1:23:25Speaker 01

  you can lose information.

• 1:23:28Neil deGrasse Tyson?

  Is that the start of a formulation that will one day marry general relativity in quantum physics?

• 1:23:35Speaker 01

  Well, it does do that. It's not, it's not.

• 1:23:40Neil deGrasse Tyson?

  It's knocking on the door.

• 1:23:41Speaker 01

  It's knocking on the door. It's.

• 1:23:44Neil deGrasse Tyson?

  And so remind me now, your professor born in this question. What is the problem with general relativity not melding together with quantum physics? What is the, what is the real holdup there?

• 1:24:02Speaker 01

  Well, the real holdup is that they are logically incompatible with each other. And so something has to give.

• 1:24:08Neil deGrasse Tyson?

  And that's because of the quantum, general relativity requires space to be a continuous.

• 1:24:14Speaker 01

  You have a continuum space. You and it's a very definite space. It's not a space where you have a certain probability that space is warped in this way and another probability is warped in that way.

• 1:24:26Neil deGrasse Tyson?

  In fact, there are no probabilities at all.

• 1:24:28Speaker 01

  Yeah, there are classical probabilities, but not.

• 1:24:31Neil deGrasse Tyson?

  Quantum.

• 1:24:31Speaker 01

  But not quantum probabilities.

• 1:24:33Neil deGrasse Tyson?

  And so at the smallest scale, they're incompatible.

• 1:24:36Speaker 01

  The smallest scale.

• 1:24:39Speaker 01

  They're incompatible in any place where gravity becomes extremely strong, they're incompatible. So the smallest scale, they're incompatible, even here in this room. But also, they're incompatible, they're incompatible in the birth of the universe when gravity was extremely strong. They're incompatible in the core of a black hole, where gravity's extremely strong. They're incompatible. If you try to make a time machine, Hawking and I, independently with our students, sort of identified a process whereby if a very advanced civilization tries to make a time machine, it will quite possibly explode at the moment you try to turn it on.

• 1:25:22Speaker 01

  And that's also controlled by these laws of quantum gravity.

• 1:25:27Neil deGrasse Tyson?

  So that's why we haven't seen any time travelers yet.

• 1:25:29Speaker 01

  Well, that's, that's, that may be the reason.

• 1:25:32Neil deGrasse Tyson?

  It would explain, they're all dead trying to turn on the machine.

• 1:25:34Speaker 01

  That's right.

• 1:25:35Neil deGrasse Tyson?

  What you're saying is Einstein puts forth the general theory of relativity, which is so successful in so many realms, and it picked up where Newtonian gravity failed, yet we must confess, or concede, that there's a limit to how far general relativity goes, although we've yet to find a limit to quantum physics. So the betting, the betting pool will say, general relativity is going to succumb to quantum physics in some way.

• 1:26:07Speaker 01

  Yeah, that, that's one way to say it. Certainly, there is this incompatibility between the two.

• 1:26:13Neil deGrasse Tyson?

  And string theorists are trying to be this, they're like, performing the shotgun wedding between the two branches of physics somehow.

• 1:26:21Speaker 01

  Yeah, and I, I do think, again, looking in from the outside, since I've chosen not to work in this field, that string theory is, is likely to be a successful route into the correct laws of quantum gravity.

• 1:26:34Neil deGrasse Tyson?

  Yeah, but they've been at it for 50 years.

• 1:26:35Speaker 01

  Oh, yeah.

• 1:26:36Neil deGrasse Tyson?

  Forty, forty years.

• 1:26:37Speaker 01

  That's not, that's not, come on, I'm 84, I'm 84 years old, come on. That's, that's, that's just a drop in the bucket, come on.

• 1:26:45Neil deGrasse Tyson?

  Wait, but Einstein went from special relativity to general relativity in 10 years. Kepler went from, from weird nested solids to...

• 1:26:55Neil deGrasse Tyson?

  The Kepler's three laws of motion in 10 years, and that's lone scientists.

• 1:27:00Speaker 01

  We've been working to try to do controlled fusion for

• 1:27:06Neil deGrasse Tyson?

  For 50 years.

• 1:27:07Speaker 01

  More than 50 years. LIGO took 50 years from the time I first started working on gravitational waves until we succeeded was 50 years. Some things take a long time.

• 1:27:18Neil deGrasse Tyson?

  Yeah, but LIGO is a machine. The merging of quantum physics and general relativity are ideas. Could it be, and I've said this, I don't want to say this to you because you're Kip Thorne. But I've said this to Brian Greene, okay, because Brian Greene is like my generation. I said to Brian Greene, I said, Brian, you've been working on string theory for decades. Maybe all of you are just too stupid to figure it out and we're waiting for someone else to be born into this field to then solve it and went in the ways none of the rest of you can. None of them are saying, I'm too stupid to figure this out. Let me choose another profession. No, they're saying the problem is too hard. And if you go 40 years of really smart people not figuring something out, that tells me either

• 1:28:03Neil deGrasse Tyson?

  they're barking up the wrong tree or none of them are smart enough. Am I overreacting here?

• 1:28:09Speaker 01

  I think you have to remember that we do build on each other. None of them by themselves are smart enough.

• 1:28:16Neil deGrasse Tyson?

  Okay.

• 1:28:17Speaker 01

  But the community, again, it's like this Nobel Prize really belongs to a thousand people. It doesn't belong to me.

• 1:28:27Neil deGrasse Tyson?

  With the Genesis and Joe Weber.

• 1:28:30Speaker 01

  With the Genesis and Joe Weber. We build, Newton spoke of standing on the shoulders of giants. And that really is true.

• 1:28:39Neil deGrasse Tyson?

  If I can see farther than others, it's because I've stood on the shoulders of giants who've come before me.

• 1:28:44Speaker 01

  And that's the nature of science. And the struggles that our colleagues have been having with string theory and M theory and quantum gravity. We've learned an enormous amount. It shows it's very promising, but it's going to continue on into the next generation before the ultimate success is had. Very, very, very probably.

• 1:29:11Neil deGrasse Tyson?

  Those are like final words right there.

• 1:29:16Neil deGrasse Tyson?

  I've heard rumor that whichever faculty of Caltech gets a Nobel Prize, they get a parking spot with their name on it. Is that true?

• 1:29:30Speaker 01

  If I went at Caltech, a Nobel Prize does not get you a parking spot with your name on it. You have, you have to pay for the parking spot just as much as you do without a Nobel Prize.

• 1:29:43Neil deGrasse Tyson?

  Okay, but that was such a fun rumor, though. I heard that.

• 1:29:46Speaker 01

  That's, that's true at USC, but it's not true at Caltech.

• 1:29:49Neil deGrasse Tyson?

  Okay, because there's just too many of you all running around with Nobel Prizes. The parking spots are too valuable. So true at USC. Okay.

• 1:30:00Speaker 01

  It's true at USC.

• 1:30:00Neil deGrasse Tyson?

  All right. So you're 84. You have 84 years of wisdom coursing in your veins and arteries. Are there any projects you're working on in the next several years?

• 1:30:12Speaker 01

  So I made a gradual transition conscious away from science, away from scientific research, beginning around 15 years ago.

• 1:30:26Neil deGrasse Tyson?

  Oh.

• 1:30:27Speaker 01

  I, you know, I would like to be, like to believe I can live to 110. That's my intended goal. And so for the next remaining decades, I wanted to do things that I really enjoyed. And I've enjoyed science. I've been a conventional Caltech professor for half a century. Enormously enjoyed it. Enormously enjoyed working with students. I trained over 50 PhD students and who did far more important research than I did. And been there, done that. And I have

• 1:31:08Speaker 01

  worked in all these areas of science and I've had enormous fun, but I've turned them over to the younger generation. And they're smarter than I am.

• 1:31:17Neil deGrasse Tyson?

  Okay, so what are you, you surfing now or skydiving? What, okay, you're taking up other.

• 1:31:22Speaker 01

  So I, so I, I decided that I would like to spend a few decades doing creative work at the interface between science and the arts.

• 1:31:33Neil deGrasse Tyson?

  Oh.

• 1:31:33Speaker 01

  So Interstellar is an example.

• 1:31:36Neil deGrasse Tyson?

  That was gonna be released in September and then they delayed it to the holiday season in December.

• 1:31:41Speaker 01

  So the re-release of Interstellar.

• 1:31:43Neil deGrasse Tyson?

  The re-release to December 2024.

• 1:31:45Speaker 01

  That's right, that's right. That, that was enormously enjoyable. I, it, I, for me, I learned how great it can be to collaborate with somebody who's brilliant and is completely different than I am, Christopher Nolan. So my most recent collaboration has been a book of poetry and paintings with Leah Halloran and about the warped side of the universe. And my poetry, my attempts at poetry and her paintings, but just trying to see whether it's possible by tightly integrating paintings with verse

• 1:32:25Speaker 01

  to convey the essence of issues in science, the spirit, the essential features without conveying the precise details. No, that's not the right genre for precise details, but anyway, so I've been enjoying that.

• 1:32:41Neil deGrasse Tyson?

  By the way, I've always felt that way about Van Gogh's Starry Night.

• 1:32:44Speaker 01

  Yes.

• 1:32:45Neil deGrasse Tyson?

  Where you look at that painting, you say, this is clearly not what he saw, but it's definitely what he felt.

• 1:32:52Speaker 01

  Yes, yes.

• 1:32:53Neil deGrasse Tyson?

  And you get to experience the universe through his own lens.

• 1:32:56Speaker 01

  Yes.

• 1:32:57Neil deGrasse Tyson?

  And so I've always appreciated art when it plays that role.

• 1:33:00Speaker 01

  I have a second movie that's been in the works for more than a decade.

• 1:33:05Neil deGrasse Tyson?

  Can you tell?

• 1:33:05Speaker 01

  Well, it's just something that I started with Stephen Hawking and Linda Opst, who is my, my partner on, uh, starting Interstellar. Uh, it is wonderful to work with. Uh, but that movie might never get made. I'm not going to tell you what it's about, aside from the fact that it's sci-fi. Uh, and it's solid sci-fi, science built in from the outset. So if that does not work out in the end, uh, then I may turn it into, try turning it into a novel. I've never tried to write a novel. I don't know whether I can, but it would be fun to try. And actually, the thing that I have put almost a large fraction of my effort in,

• 1:33:47Speaker 01

  the lion's share of my effort in since the beginning of the pandemic is a history of the LIGO project, the LIGO Gravitational Wave Project, because that is, I think, pretty clearly the technically most difficult thing that's ever been done by physicists.

• 1:34:03Neil deGrasse Tyson?

  By anybody, by anybody.

• 1:34:05Speaker 01

  Yeah, probably by anybody.

• 1:34:06Neil deGrasse Tyson?

  One one hundredth the diameter of a proton, that's anybody.

• 1:34:09Speaker 01

  And, and success required both amazing, developing amazing technology, new technologies, and it required developing computer simulations of colliding black holes, required developing quantum precision measurement technology that is now in LIGO and is playing a major role, where you circumvent the, what's called the Heisenberg uncertainty principle.

• 1:34:40Neil deGrasse Tyson?

  My mind is still partly blown by having, by you having said that. You're bypassing Heisenberg's uncertainty principle.

• 1:34:46Speaker 01

  That's right. By manipulating vacuum fluctuations, just like advanced civilizations.

• 1:34:53Neil deGrasse Tyson?

  Might do as a routine thing.

• 1:34:56Speaker 01

  Yeah. So we had to, we developed this new area of technology for LIGO. The, and, but it was also a very political thing. How do you get a billion dollars of taxpayer money for a field that doesn't, didn't exist when you began?

• 1:35:17Neil deGrasse Tyson?

  And should they bet on you and not someone else?

• 1:35:20Speaker 01

  That's right.

• 1:35:20Neil deGrasse Tyson?

  And plus, I think you even had naysayers, if I remember correctly. Colleagues would say, this is a, this is a pipe dream.

• 1:35:25Speaker 01

  We had, we had political battles in Washington.

• 1:35:28Neil deGrasse Tyson?

  Yeah. Tell me who the naysayers were. I got people to take care of them.

• 1:35:32Speaker 01

  They were, they were some of the leading astronomers.

• 1:35:34Neil deGrasse Tyson?

  I got people to take, you want my people to?

• 1:35:39Speaker 01

  They've come around.

• 1:35:41Neil deGrasse Tyson?

  You think? Okay.

• 1:35:43Speaker 01

  They've come around because this is so exciting now that LIGO succeeded. But the sociology of the transition from small science to big science is a very rocky process.

• 1:35:56Neil deGrasse Tyson?

  That's the right word, sociology, because that's what it is.

• 1:35:58Speaker 01

  I don't like working in a big science project. It's not for me. Just like working in a crowded field is not for me. But this had to make the transformation.

• 1:36:08Neil deGrasse Tyson?

  It wouldn't have happened otherwise.

• 1:36:10Speaker 01

  Transformation wouldn't have happened otherwise. The genius of Barry Barish in making that happen. And the genius of Robbie Volk in getting us partway there at the very beginning. It's our initial director, who was the one that sold it to Congress. And it really got us going. It's a very complicated story. And I have a set of five collaborators that I've been working on with this history. We just finished draft six and sent it out to LIGO colleagues to comment on. And I have been getting back huge numbers of comments. And it'll take me two more years, I think.

• 1:36:50Speaker 01

  So, anyway, this history, because of the nature of this project, it's a very interesting, complex history that is quite important for the history of science.

• 1:37:02Neil deGrasse Tyson?

  Especially when you consider, most people knew nothing of LIGO until they see the headline that it discovered gravitational waves. And why would they have any thought of what challenges preceded that? You know, they just read the result. Oh, scientists discover this. Well, how about, like you said, the politics, the sociology, the genesis, the who's standing on whose shoulders, who are the naysayers? All that has to be overcome.

• 1:37:29Speaker 01

  The international collaboration, key input from the Soviet Union in the depths of the Cold War.

• 1:37:37Speaker 01

  And it's just a fascinating story and enormous fun.

• 1:37:46Neil deGrasse Tyson?

  You know, Arthur C. Clarke said, he said, "In space where there is no air, a flag will not wave."

• 1:37:54Neil deGrasse Tyson?

  So maybe the universe is not a place where we should be waving flags. Collaboration is what gets you there.

• 1:38:02Speaker 01

  I like that.

• 1:38:03Neil deGrasse Tyson?

  So Kip, this has been a delight. Thanks for making time.

• 1:38:06Speaker 01

  A lot of fun.

• 1:38:07Neil deGrasse Tyson?

  For StarTalk. I look forward to the release of the re-release of Interstellar. We're recording this before that has come out. And you already know this, but let me reaffirm that that film just took people on a ride far beyond anything they had imagined. It had a kind of an impact on people in the way 2001: A Space Odyssey did. It was mysterious, it was modern, it was the future, but it was still relevant, but it left you with more questions to ask than questions answered. And you want that, I think.

• 1:38:47Speaker 01

  Yeah, and that was really the genius of Christopher Nolan, taking some science that he and I had put together, but combining with a human story that was powerful.

• 1:39:03Neil deGrasse Tyson?

  And with marquee director and marquee actors that made sure it would get noticed.

• 1:39:08Speaker 01

  And music.

• 1:39:09Neil deGrasse Tyson?

  Yes.

• 1:39:10Speaker 01

  I went to a concert by Hans Zimmer.

• 1:39:12Neil deGrasse Tyson?

  That was Hans Zimmer, yes.

• 1:39:14Speaker 01

  Just, I think, the night before last. And he let loose, but I didn't know there, but he basically said that the certain pieces of the music in Interstellar were as close to perfection as he has achieved.

• 1:39:29Neil deGrasse Tyson?

  Wow, I'm gonna give it another listen, because there is no 2001 without its musical track, with the Strauss Waltzes, the...

• 1:39:37Speaker 01

  This is very different. It's all Zimmer's original music, and it's a remarkable score. Just amazing.

• 1:39:49Neil deGrasse Tyson?

  I look forward to your next 25 years, when you live to 110. Maybe we can do a reprise of this conversation. We'll check in on you. See how you've been coming along, dude.

• 1:40:02Speaker 01

  Thanks a lot.

• 1:40:03Neil deGrasse Tyson?

  Thanks.

• 1:40:04Speaker 01

  Great to see you again.

• 1:40:05Neil deGrasse Tyson?

  Thanks. This has been a special conversation, exclusive one-on-one between StarTalk and... Kip Thorne, Nobel Laureate, even let me touch his medal. First time I've ever touched a Nobel Prize.

• 1:40:19Speaker 01

  Well, the medal that really belongs to a thousand.

• 1:40:21Neil deGrasse Tyson?

  The medal earned by a huge team, as he humbly declares. And as we enter a new era of science where collaborations are really how this works, especially where you have international collaborations, you have scientists getting along, even at times when the leaders of their countries are in conflict. That's just messed up.

• 1:40:43Neil deGrasse Tyson?

  That's messed up. I'm Neil deGrasse Tyson, your personal astrophysicist. Four star talk. As always, I bid you to keep looking up.