Deciphering Gravitational Waves, with Janna Levin - StarTalk Allstars

What are gravitational waves, and what can they tell us about our universe? In her first outing as StarTalk All-Star host, cosmologist Janna Levin untangles the astrophysics with help from LIGO co-founder Rainer Weiss and comic co-host Matt Kirshen.

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

• 0:00Speaker 00

  This is StarTalk.

• 0:08Janna Levin?

  Welcome to StarTalk All-Stars. I'm Janna Levin, your All-Star host for the day. I'm an astrophysicist and author. Joining me as co-host is the funny Matt Kirshen, host of Probably Science. Hi, Matt.

• 0:22Matt Kirshen?

  How's it going?

• 0:22Janna Levin?

  Welcome back.

• 0:23Matt Kirshen?

  Thanks for having me back.

• 0:24Janna Levin?

  It's been like 10 minutes.

• 0:26Matt Kirshen?

  Yeah, it's nice to be here in space.

• 0:27Janna Levin?

  It's great to have you. And I also want to introduce one of my favorite people in the world, joining us in the studio, Ray Weiss.

• 0:35Speaker 03

  Thank you, Jana.

• 0:35Janna Levin?

  Otherwise known as Rainer Weiss, for long. Great to have you. Ray is Professor Emeritus from MIT. He is also one of the original architects of the LIGO detector, which announced the detection of gravitational waves last year. It was this year. Why does the prompt say last year?

• 0:52Speaker 03

  It happened last year.

• 0:53Janna Levin?

  It happened last year. Sorry, guys. It was one of the most groundbreaking discoveries of modern astrophysics and very personally important to me. Ray is one of the founders of the LIGO instrument and continues to work on the instrument all the time, as I know because I've been to the sites with you. You kindly let me perform.

• 1:12Speaker 03

  You slog with me in a tunnel, I remember.

• 1:14Janna Levin?

  Yes, in the heat of Louisiana. It was amazing. So it's so great to have you here. We're going to talk about LIGO, and gravitational waves, and black holes. So I think what we want to draw out is why this discovery was so important. I think that when people heard about it, it was so, the whole world stopped in February 11th, when the announcement was made. And for a minute, it was so exciting. Everybody was frozen. And then I felt like an hour later, people just weren't sure what it was all about. It's hard to understand.

• 1:44Matt Kirshen?

  I mean, I've got it covered because I'm obviously good on these things. But just for everyone else, if you could just kind of give a vague overview.

• 1:50Speaker 03

  Well, I'll try, but I was as mystified as you in the fact that it had this enormous public recognition.

• 1:56Janna Levin?

  Oh, yeah.

• 1:57Speaker 03

  I mean, you take other things.

• 1:57Janna Levin?

  Were you surprised?

• 1:58Speaker 03

  I was more than surprised. I was flabbergasted, to be honest with you.

• 2:01Janna Levin?

  Oh, really?

• 2:02Speaker 03

  I mean, my first real instinct that it had permeated the society was when I came to New York to come and visit you at the Pioneer Works. And I get in the subway, and there's this sign that says, you know, scientists can find gravitational waves, but you can't find an apartment in New York with an old walk-in closet.

• 2:20Janna Levin?

  Right.

• 2:20Speaker 03

  I said, where in the hell does that come from?

• 2:22Janna Levin?

  Exactly. It was a Jeopardy question.

• 2:25Speaker 03

  Is that what it was?

• 2:26Janna Levin?

  Yeah, no, also, as well.

• 2:28Speaker 03

  Oh, I didn't realize that. I didn't realize that.

• 2:29Matt Kirshen?

  Have you, has science now detected an apartment in New York with a walk-in closet?

• 2:33Speaker 03

  I haven't been looking lately. I don't live here.

• 2:35Janna Levin?

  If anyone can find it, Ray can. So, Ray, do you want to tell us what gravitational waves are? Because this is very hard for people to understand. They can say the words, but they really don't get what it's all about. And they certainly don't get why you played it to them as a sound.

• 2:49Speaker 03

  Well, let's start with what they might be, I mean, what they are. They're a result of Einstein's first thinking about how you measure things in space and time. In other words, he realized back in 1905 that the Newtonian theory we had, the theory that was, the theory that was, oh, we all learnt in high school, was inadequate, that you couldn't have things travel so fast that everybody knew about it instantaneously. There had to be some delay, because the fastest that things can move, even information, thought, is of the velocity of light.

• 3:21Janna Levin?

  Right, so if the sun disappeared tomorrow, it should take us eight minutes.

• 3:25Speaker 03

  Well, that's right. If the sun disappears, well, yeah, it'll take about eight, nine minutes before we really know about it.

• 3:30Matt Kirshen?

  It's great if you're like a magician or something.

• 3:33Janna Levin?

  Do you need the extra time?

• 3:34Matt Kirshen?

  Well, yeah, because like David Kung feel made the Statue of Liberty disappear, but he had like seconds really to do that in.

• 3:39Janna Levin?

  Yeah, if you had eight minutes to play with.

• 3:41Matt Kirshen?

  You could do anything. You could be an amateur magician, still kind of like, you'd have time to get some helpers to actually shove it out of place.

• 3:47Janna Levin?

  What'd you do with the sun, Matt?

• 3:48Speaker 03

  Yeah, but those eight minutes are damned important.

• 3:51Matt Kirshen?

  Right.

• 3:51Speaker 03

  Because they tell you that there has to be some mechanism for information to travel not infinitely quickly.

• 3:58Janna Levin?

  Right, so in Newton's theory, it would have to be instantaneous.

• 4:00Speaker 03

  That's the first order way of talking about gravitational waves. And specifically, what are they? Einstein had a different way of looking at gravity than Newton did. And he taught us all that space and time get distorted by gravity. You get curvatures, you get distortions of space and time. And what a gravitational wave is, is a traveling distortion of space and time. But we measure it as a distortion in space. And the very special thing, so you don't have, you can imagine what it is, it's not very hard to imagine, is that it's a stretching of space and a compression of space. And here's, just bear with me, here's what it is. Where the wave travels, let's say, toward you, and it does its dirty work perpendicular to the direction in which it's moving. So something's doing this. And while it's doing this in one dimension-

• 4:42Janna Levin?

  Okay, Ray's oscillating his hands in and out.

• 4:43Speaker 03

  Oh yeah, I gotta tell you, that's right. Waving my hands back.

• 4:46Matt Kirshen?

  Almost like a slinky spring.

• 4:47Speaker 03

  Well, a slinky, let's say, a slinky in the x direction, but a slinky inverted in the y direction, it's doing the opposite.

• 4:53Janna Levin?

  I hope you all use right-handed coordinate systems.

• 4:55Speaker 03

  In one dimension, in the direction it's moving, perpendicular direction it's moving, it's stretching in one dimension, it's compressing in the other. And that continual compression, expansion, travels at the velocity of light toward you. And that's the way to imagine a gravitational wave.

• 5:08Janna Levin?

  Now, when you first started thinking about this, you were a young professor at MIT, and you had this whole gravity research program. And I know you confessed to me that they asked you to teach a class in general relativity.

• 5:21Speaker 03

  Well, I'll confess again. What Jana's referring to is a very big embarrassment. See, I come to MIT, having been to Princeton, the hotbed of general relativity and gravity, and I come and I start a group, very expendable, I'm an experimenter. I'm not a theorist like Jana. Jana's a true theorist. But I'm an experimenter, I deal with things with my hands. And what happened-

• 5:41Matt Kirshen?

  Already, like, before the show even started-

• 5:43Janna Levin?

  He was using his hands wildly.

• 5:45Matt Kirshen?

  Before the show started, you were kind of looking at the microphone and like taking it apart, like you can't help yourself.

• 5:49Janna Levin?

  No, you can't.

• 5:51Speaker 03

  Yeah, you gotta do that, you gotta find out what you're, what you're surrounded by, come on. It's part of the world.

• 5:56Janna Levin?

  Palpate, palpate the world.

• 5:57Speaker 03

  So, you know, it's tactile and it's all sort of seeing things. But anyway, so as Jana says, that what happened is that I'm running this group that is supposedly about very complicated topics like cosmology, which is the history of the universe, and also gravitation. Okay, those were the two things I started. And then the department head comes to me and says, you know, we would like you to teach a course in general relativity, which is a course of the new kind of gravity. And I couldn't tell him, I didn't know a damn thing about it. I mean, I really didn't know much about it. I didn't know the mathematics. I mean, the students, when I finally started teaching, were probably barely, I was barely half a day ahead of the students, if at all.

• 6:35Matt Kirshen?

  Right.

• 6:36Speaker 03

  So here I go, and they asked me a very hard question as we go along. The course has its ups and downs, as you can well imagine, and they asked me a hard question. They said, "Look, what is a gravitational wave?" And I tried to answer it, but what was going on at that time was that Joe Weber, who was a physicist at the University of Maryland, had begun to talk about that he might have discovered gravitational waves.

• 6:58Janna Levin?

  Mm-hmm, and this would have, his campaign started in the 50s to...

• 7:01Speaker 03

  No, this was started in the 60s.

• 7:02Janna Levin?

  Sixty, you go late 60s.

• 7:03Speaker 03

  Well, he started really quite early, in 62, and he made the announcement that he had discovered gravitational waves in 1969. That caused a tremendous furor.

• 7:12Janna Levin?

  He was incredibly famous.

• 7:13Speaker 03

  Well, yeah.

• 7:14Matt Kirshen?

  And he was lying? He was just...

• 7:15Speaker 03

  No, no, no, don't say lying. That's not the right word.

• 7:18Janna Levin?

  We're all very defensive about Joe now.

• 7:20Matt Kirshen?

  It's like, I'm not gonna brag, but I also did discover gravitational waves like about a month before you guys.

• 7:25Speaker 03

  It's good, I'm glad of that. What did yours look like?

• 7:28Matt Kirshen?

  It was just like, it was like I just put a cup on a table and it kind of wobbled a bit.

• 7:32Janna Levin?

  And the water wobbled, and he knew that they were gravitational waves.

• 7:35Matt Kirshen?

  Right, we've seen Jurassic Park.

• 7:36Speaker 03

  Well, like those two birds in the New Yorker cartoon. Probably saw that cartoon.

• 7:40Janna Levin?

  I didn't see it.

• 7:41Speaker 03

  Two birds sitting, this is right after the discovery again, two birds sitting on a branch. It was right on the 12th of February. We announced on the 11th of February, so somebody had prior information.

• 7:50Janna Levin?

  Right.

• 7:50Speaker 03

  But these two birds, two birds are looking one, and I'm looking at the other, and the one says, "Hey, did I hear you, or was that a gravitational wave too?" And that could have already, that's the kind of thing. Anyway, so let me get back to the story. The thing was that they asked me about this, and I frankly, be honest with you, despite having trouble with the mathematics, I also had trouble with understanding Weber's experiment. It's not that he was lying or anything like that, it's just a way, too complicated for me to understand exactly what he was doing. So I spent a lot of time one night thinking about how could I explain what a gravitational wave does, and how would you detect it in the most pristine, simple-minded way possible? And that's where this haiku, as you call it, came about. Which is the, I thought, well, you know, one way to do it is send some masses out there,

• 8:34Speaker 03

  put them out in outer space, put clocks on them, two clocks, one on one, clock on the other, and have a light beam go from one to the other and measure the time. That's all.

• 8:43Janna Levin?

  Yeah.

• 8:43Speaker 03

  Very straightforward measurement.

• 8:44Janna Levin?

  And they'd have to be sort of floating, so that when-

• 8:46Speaker 03

  Floating out there, I mean-

• 8:47Janna Levin?

  Like bobbing on the wave of the, of the ocean, if something floats on the ocean.

• 8:50Speaker 03

  Well, they're actually just moving along without any forces on them. And then, all of a sudden, a gravitational wave comes along and it changes the time that light takes that goes between them. That's it. Makes it shorter for a while and longer, does exactly what the gravitational-

• 9:03Janna Levin?

  You started to build one.

• 9:04Speaker 03

  Well, yeah, yeah, yeah, but that's the, that's the basic idea. And by the way, that idea is the one that propagated into the later on LIGO and everything else.

• 9:11Janna Levin?

  Is this what you wrote about in your book? Is this what? Yeah, yeah, so I was fascinated with, you mentioned Ray looking at the microphones and all this stuff. I was fascinated that Ray said that he started life with one ambition, which was to make music easier to hear.

• 9:24Speaker 03

  That's right.

• 9:25Janna Levin?

  And then you dreamt up, which is basically a cosmic recording device, sort of insane, gigantic cosmic recording device to record sounds from space.

• 9:34Speaker 03

  She was the only one in my whole life who ever made that analogy and she was right. You know, I mean, I told her the story.

• 9:39Janna Levin?

  Awesome.

• 9:40Speaker 03

  Because I think you have a musical background or around you is music and understood this right away.

• 9:45Janna Levin?

  Yeah.

• 9:45Speaker 03

  It's absolutely true. It was-

• 9:47Janna Levin?

  Yeah, so- What's the book called? Black Hole Blues and Other Songs From Outer Space, which if I was Neil deGrasse Tyson, I would say in an awesome, deep DJ voice. I think I do have him recorded saying it. I should hear it. You just play that in at that point? Right, exactly. Just write, edit that in. But, so you, this is, okay, early 70s now we're talking about. Okay, so that's 50 years ago. And you started to build the first machine, but it was really quite small.

• 10:16Speaker 03

  Yeah.

• 10:16Janna Levin?

  And as I remember, you got a lot of flak for it because nobody thought you were going to succeed. They thought you were wasting your time.

• 10:22Speaker 03

  It was worse than that.

• 10:24Speaker 03

  This is sort of an interesting epic in the whole history of the field. Yes, I got some money from the military, by the way. It was funding my research. At the one time, military support was very, very good. You know, it was not had no had no onus associated with it in a society. And what happened was that they supported this and what happened, I got about $50,000 to build a small prototype. And then, all of a sudden, everybody got very disenchanted with the military when the Vietnam War happened. And the funding for this-

• 10:52Janna Levin?

  There goes your funding.

• 10:53Speaker 03

  Funding stopped because the military was only supposed to support those things that were relevant to its mission. And gravitational waves weren't quite in the military's complement of things they had to worry about.

• 11:04Matt Kirshen?

  Right.

• 11:05Speaker 03

  So, and-

• 11:06Matt Kirshen?

  How can we use gravitational waves to kill our enemy? Like, how can we-

• 11:09Speaker 03

  Well, I'll tell, if it gets there, I'll tell you later-

• 11:11Janna Levin?

  We'll do that in segment three.

• 11:12Speaker 03

  If you care to pursue it, I'll tell you later.

• 11:15Matt Kirshen?

  Or at least just to, like, upset someone. Like, how can I use it to upset a neighbor? Like, my neighbor's playing music too loud.

• 11:20Janna Levin?

  I'm gonna send gravitational waves towards them, full blast.

• 11:23Matt Kirshen?

  You're gonna have the master of gravity, right? That's what we're dealing with here?

• 11:26Janna Levin?

  Well, we're gonna come back. We're gonna come back to this discussion. And but before then, I think it's time for us to take some cosmic queries. So if you are out there in the ether-

• 11:35Matt Kirshen?

  All right.

• 11:36Janna Levin?

  Send us your messages. It's too late now, of course.

• 11:38Matt Kirshen?

  It is too late. Well, is it?

• 11:40Janna Levin?

  I don't know. It depends. If we can time travel, can gravitational waves help us time travel?

• 11:44Matt Kirshen?

  You know what? Might as well ask this question, then. This is perfect, unintentional timing here. But Jake the Guy on Instagram is asking, does any of this mean I can travel in time?

• 11:55Janna Levin?

  Ray, do gravitational waves help us travel in time?

• 12:01Speaker 03

  I don't know how they would, but maybe you have an idea. You're a theorist.

• 12:04Janna Levin?

  I don't think so. I don't think so. I can't think of a way in which they would help us travel in time. But, you know, you can always travel to the future. I mean, always, if you set things up.

• 12:14Matt Kirshen?

  That's a cop-out, though. Like, we're down here right now.

• 12:16Janna Levin?

  I can travel towards your future, though. That's pretty weird. I could travel to a time when you are 15 years older and I'm only, like, a couple months older.

• 12:23Matt Kirshen?

  Okay, by going off to space and coming back?

• 12:26Janna Levin?

  Yeah, I can, you know, send you far from the earth, or I can go to a black hole or something like that. So I can always travel to somebody else's future. But traveling to the past is the hard part. That's pretty tricky.

• 12:36Matt Kirshen?

  All right, Taylor from Eugene, Oregon.

• 12:39Speaker 03

  We did a fairly lousy job of answering him. You know, it was a good enough.

• 12:43Janna Levin?

  Yeah. I think, I'm pretty sure Ray just said, "I gave a lousy answer."

• 12:47Speaker 03

  You did give a lousy answer.

• 12:48Janna Levin?

  And there's only one person in the world I would take that rather-

• 12:52Speaker 03

  Probably want something very deep.

• 12:54Janna Levin?

  It was deep, you just weren't paying enough attention.

• 12:58Matt Kirshen?

  So, Taylor from Eugene, Oregon, asks, "Do gravitational waves have any direct effect on the physical environment? For example, if an event causing gravitational waves occurred close enough to Earth, would it have any discernible effect on humans or the planet?"

• 13:13Speaker 03

  Well, that's a question I can even answer. And in fact, if we measured this event from two black holes, and I have to start that way, which was, fortunately for us, 1.2 billion light-years away. But had we been, let's say, within a few tens of years of that, we would have measured something. And you would have measured exactly what we measure in our detectors. You wouldn't stretched in one dimension and compressed in the other dimension. You would have felt that.

• 13:42Janna Levin?

  Now, we resist stretching and compression, but our auditory mechanism is designed to resonate in response. Do you think that we could technically hear a gravitational wave even in the absence of air?

• 13:55Speaker 03

  I don't think that's not because of...

• 13:57Janna Levin?

  I've been saying this for months.

• 13:58Speaker 03

  Well, I don't think it's true. Well, I think, let's get to that, this issue right away, because we, not you, we have generated some confusion by saying this is listening to the universe, which is what a lot of people have said about this. And it's true, but it's not necessarily a sound wave that's exciting us, you see? And what is happening is that we are seeing these stretchings and compressions, and that's certainly going on in your ear, too. The compression and extension, even for that one year away, light-year away, is still too small for your ear.

• 14:30Janna Levin?

  Right, so how close do you... Oh, yeah, I would agree with that.

• 14:32Speaker 03

  If you got close enough, you would feel it in your whole body, and you might hear something. But that's not what we're doing.

• 14:38Matt Kirshen?

  So, like, a sound wave is like the compression and expansion of the air around you?

• 14:42Speaker 03

  That's right.

• 14:42Matt Kirshen?

  And this is, actual space itself is doing that?

• 14:44Speaker 03

  Yeah, but be careful. What it is, is space, you're right, space is doing the expansion and the compression. On the other hand, our instruments, this is where it gets converted into sound. That's why I looked at your microphone. Is, what we do is, we have a device that measures these very tiny displacements. We're using light and the timing of light, but then we convert that into a sound by amplifying it. And then that gets put into a loudspeaker, yes, and then it makes a sound.

• 15:07Janna Levin?

  It's a lot like an electric guitar.

• 15:09Speaker 03

  Exactly, but exactly like an electric guitar. You've got a very good analogy. Very good analogy. And the other thing is that it's an, the other, the other piece of it is that this phenomena, these phenomenas we are seeing, phenomena we are seeing, are things that have the frequency of our auditory system. That's the nature is making things with frequencies that run from the bottom of the piano to the top of the piano.

• 15:33Matt Kirshen?

  I mean, it's just by chance that just happens to be in there.

• 15:35Speaker 03

  Well, that's because the things we're looking at, well, it's little more than that. What it is, is our instrument's only sensitive in that band, okay? And on top of that, nature's kind enough to give us something that does its wiggling and expanding and contracting and accelerating in that frequency band.

• 15:48Janna Levin?

  A couple of black holes collide, they happen to ring spacetime in the human auditory frequency.

• 15:52Speaker 03

  Yeah, okay, so it's not sound waves traveling through space. I just don't want to have that.

• 15:57Janna Levin?

  It's like an electric guitar string is not a sound wave traveling through space. But you had to build LIGO to build the body of the guitar to record the shape of the wave.

• 16:05Speaker 03

  Absolutely. That's a beautiful analogy.

• 16:06Janna Levin?

  Excellent, and then we're going to all break out into air style guitar. Give us another cosmic query.

• 16:12Matt Kirshen?

  From Florida, Sarah Gavijanser is asking, when gravitational waves are recorded, is there a way to know which black holes collided to make them? And is there any other event out there that could cause gravitational waves? If so, how would they differ?

• 16:26Speaker 03

  Boy, that's a profound question. And this has a lot of different pieces to it, that question. Let's first of all say, how do we know that we are even seeing black holes? I think that's one way, in our experiment, that we were seeing black holes. You have to do an analysis to find that out. It could be other systems that, you know, neutron stars, there are many, many things that oscillate and wiggle that can make gravitational waves. But it happens to be, and this is the important thing, the specific wiggles we saw, when you solve them, as trying to figure out what the motions are, that made those wiggles, you wind up with masses that are, in our case, the first one was too big. The masses are 30, each one of the masses was about 30 solar masses. And we don't know of things, we know of ordinary stars that do that, but they're too big.

• 17:11Speaker 03

  Because what happens if you take an ordinary star?

• 17:13Janna Levin?

  It was surprising how big they were.

• 17:14Speaker 03

  They what?

• 17:15Janna Levin?

  It was surprising how big they were.

• 17:16Speaker 03

  Yeah, monstrous.

• 17:17Janna Levin?

  It's exciting.

• 17:18Speaker 03

  Yeah, monstrous. I mean, all the black holes people had seen or not, nobody's seen a black hole, but had evidence for was around 10 solar and smaller around there. No, the important thing is that once you make the calculation that you know it's about 30 solar masses that jiggling around, you then say, my God, look how close they are by from the equations. You can say they're much closer than any star. They would be inside of each other.

• 17:37Janna Levin?

  Yeah, they're a couple hundred kilometers across.

• 17:39Speaker 03

  These things are no bigger than the just the size of Connecticut, maybe.

• 17:42Janna Levin?

  Yeah.

• 17:42Speaker 03

  You know, and or even smaller, maybe.

• 17:44Matt Kirshen?

  The only things that big that can also be that close are black holes.

• 17:48Speaker 03

  Well, that's the argument. That's fundamentally the argument.

• 17:50Janna Levin?

  That's the best we can do.

• 17:51Speaker 03

  Exactly the argument.

• 17:52Janna Levin?

  So maybe there's something else that when we got close, we would realize didn't have an event horizon, wasn't a complete shadow, wasn't really empty spacetime that, you know, it can be different than what we think of a black hole is, but it's got to be heavy and small.

• 18:03Speaker 03

  Yeah.

• 18:04Janna Levin?

  So I think that's an interesting place to end, and I'm really sorry we have to wrap this up, but I'm glad we're going to come back in a minute. And we're going to take a short break, stick around for more discussion and more of your cosmic queries after this. We're back on StarTalk All Stars. I'm your host, Jan Levin. I am an astrophysicist and author here in New York City at Barnard College of Columbia University. Here with me is my incredibly talented co-host, Matt Kirshen. Yay.

• 18:31Matt Kirshen?

  Hey.

• 18:32Janna Levin?

  Matt, comedian and host of Probably Science Podcast, which is very funny.

• 18:37Matt Kirshen?

  Thank you.

• 18:38Janna Levin?

  It is a long rambling. They have no rules, and that's what we love about them.

• 18:41Matt Kirshen?

  Started off saying funny, and then he went long and rambling. They were like, you're next. Oh, it's dreary, it's a dud, thank you for the point.

• 18:48Janna Levin?

  They're going to cut that part out, Matt. Our special science guest today is Ray Weiss, professor emeritus from MIT and one of the founders of LIGO, architect of the original instrument that recently detected gravitational waves. I remember when you were talking about in the last segment, running out of funding because the military funding was cut, and you told me the next big event is I met Kip. I loved that line.

• 19:16Speaker 03

  Let me tell you what the next event was.

• 19:17Janna Levin?

  Okay.

• 19:18Speaker 03

  The next event was really trying to get money. That was the next event, try to finish it. And that's what happened. Kip comes soon.

• 19:24Janna Levin?

  Mm-hmm.

• 19:25Speaker 03

  But the next event was really trying to get some money, and that's where I ran into the trouble.

• 19:29Janna Levin?

  Mm-hmm.

• 19:29Speaker 03

  Said there were trouble getting that money, getting that. The people were skeptical.

• 19:33Janna Levin?

  And your instrument was a meter and a half across.

• 19:35Speaker 03

  Yeah, the initial prototype, it was a meter and a half. We wanted to just demonstrate. It was never intended to make a detection.

• 19:42Janna Levin?

  Mm-hmm.

• 19:42Speaker 03

  In fact, nothing until LIGO was even ever able to contemplate making a detection.

• 19:46Janna Levin?

  Didn't somebody tell you I could do better by looking out the window? If the sun blew up, you couldn't detect it?

• 19:50Speaker 03

  Yeah. Well, one of my graduate students, the first time I ever put a graduate student on the project, had a terrible time with his, with my colleagues because they had no measurement of a real scientific result. They had a beautiful piece of technology, but that's not what you get a PhD for in physics, necessarily. But let's get away from that, because you asked the question. So what happened is they, the, um, I tried to get money and I didn't. And what happened is the National Science Foundation, which is what they do always, sends proposals to everybody who knows something about this. And what they did is they sent it to Europe.

• 20:21Janna Levin?

  Mm-hmm.

• 20:22Speaker 03

  And the Europeans don't have quite the same mores about an American proposal. And I had a very interesting conversation with a guy from the Max Planck Institute.

• 20:30Janna Levin?

  This is after your grant was declined?

• 20:31Speaker 03

  Yes. Oh, yeah, that's right.

• 20:32Janna Levin?

  Yeah, it was declined. So here you are with no money.

• 20:35Speaker 03

  Yeah, yeah, here I am. Nineteen seventy-five or so, we had started building the thing in seventy-two.

• 20:39Janna Levin?

  Yeah.

• 20:39Speaker 03

  And I was trying to finish it. And so we got this wonderful call from a guy at the Max Planck, and he says, you know, we've been working on Weber bars, we didn't see anything. And by the way, they had done a beautiful job of not seeing anything.

• 20:51Janna Levin?

  Right.

• 20:52Speaker 03

  Because sometimes not seeing something is better than seeing something, especially if it's not there.

• 20:55Janna Levin?

  In that case, in that case, yeah.

• 20:57Matt Kirshen?

  I like to be talking about my dancing. I think it's better to not see. To not see. Every scientist will tell you that.

• 21:07Speaker 03

  So because you make confusion if you see something that's there and that's not supposed to be there.

• 21:11Matt Kirshen?

  There are a lot of things there that are not supposed to be there.

• 21:13Speaker 03

  Yeah. So what happened is, very good. So what they did is they asked me if they would mind if they would work on this. They thought it was a good idea. I said, how can you mind? And they asked me if I had a graduate student I could send them or somebody that had been working on this.

• 21:28Janna Levin?

  Here they are, they're kind of pulling ahead on your idea.

• 21:31Speaker 03

  They pulled way ahead.

• 21:32Janna Levin?

  They pulled ahead on your idea, they had funding.

• 21:34Speaker 03

  They had funding and they were very good. Besides, give them credit. They were superb.

• 21:39Janna Levin?

  Right.

• 21:40Speaker 03

  And that also started, my colleague, Ron Driever in Scotland, who also was doing Weber bars of a different kind, and then he got interested in this. And both of those groups, I just have to say it and make sure people hear it, they both did a spectacular job of making the thing better, the idea better, and getting the thing working.

• 22:00Janna Levin?

  Now eventually...

• 22:01Speaker 03

  So that's, after that is when I met Kip.

• 22:03Janna Levin?

  Right. So eventually it becomes you, Kip, and this is now fast-forwarding 10 years, you, Kip, and Ron Driever become the three, the troika, that initiate the development of LIGO. It even gets a name, it finally gets a name in like 1985. It didn't have the name before. Laser Interferometer Gravitational Wave Observatory.

• 22:22Matt Kirshen?

  LIGO started 30 years ago.

• 22:24Speaker 03

  It started, well, LIGO started really, now it's a little earlier than that, in 83. Because what happened is, we did a study, this is that Kip getting to Kip, has a little prelude to it, yeah. I couldn't get the money for the prototype. Eventually I got some money. But I decided by looking at the wonderful work that had been done in Europe, that I was not going to be in such a hurry to finish the prototype, but rather, I would rather do a study to find out what it really would take to build a LIGO.

• 22:49Janna Levin?

  Right. So here you had a 1.5 meter machine, and how big did you decide it had to be?

• 22:53Speaker 03

  It had to be, well, we started studying and I did a whole study of it, it looked like it had to be over a kilometer.

• 22:58Janna Levin?

  Right.

• 22:59Speaker 03

  And I want to do 10 kilometers.

• 23:00Janna Levin?

  Thousand-fold.

• 23:01Speaker 03

  Yeah, well, I want to do 10 kilometers.

• 23:02Matt Kirshen?

  You had like something that was about like 80.

• 23:03Speaker 03

  Yeah, that's right.

• 23:04Janna Levin?

  Yeah. Arm span to, it doesn't fit on the MIT campus or even in Cambridge, Massachusetts anymore.

• 23:10Matt Kirshen?

  Most of my experiments like the size of a matchbox.

• 23:13Janna Levin?

  Right.

• 23:14Speaker 03

  Nowadays, they even get smaller, you know, these nanotechnology things, but you can't do gravitational waves for that way. Why? You can't do it because the amount of motion... Is bigger, the amount of motion the gravitational wave induces is proportional to the size of the system. See, what's constant in a gravitational wave is the strain. That's getting a little technical. That's the ratio of the added displacement, the compression or expansion of the gravity wave, divided by the distance that the objects are already apart. And that hot, not number, that ratio is a constant.

• 23:43Janna Levin?

  Yeah, it's very small. So LIGO now is, has these mirrors suspended at the corners of this L-shaped, four kilometer long, two instruments on two different coasts, one in Louisiana, one in Hanford. By how much are the mirrors displaced? You're describing that that's the same.

• 23:58Speaker 03

  Do you mind if I use the exponential notation?

• 24:00Janna Levin?

  I can translate.

• 24:01Speaker 03

  You can translate. Well, it's 10 to the minus 18 meters.

• 24:04Janna Levin?

  Which is a million trillion.

• 24:06Speaker 03

  Okay. You like that, fine.

• 24:09Janna Levin?

  A millionth of a trillionth of the size of the arm. So over four kilometers, it's very small. Which is how, it, it's like...

• 24:17Speaker 03

  No, no, it's 10 to the minus 21 is the strain. And it's 10 to the minus 18 is the amount of motion in a four kilometer arm.

• 24:24Janna Levin?

  Ah, right. So that comes to about a 10,000th of the width of a proton.

• 24:27Speaker 03

  Exactly. That's exactly right. And you had to convince who to let you build this? Well, a lot of people. And that was the thing you see, when you tell, tell somebody you're going to measure, tell an engineer, I mean, a solid, well-rounded engineer, that you're going to measure something at 10 to the minus 21, which is really the right number to use, because that's what the gravitational field strength is. They look at you like you were sort of a madman. And, you know, I mean, nothing gets measured at that 10 to the minus 21. So that's the first problem you have. The second problem you have is you got a nut like me, trying to convince some heavy that, you know, you can do this. Right. Now, why should they trust me? You know? That's the other problem. I have no reputation for that.

• 25:05Janna Levin?

  Well, plus, people weren't even sure there were black holes out there for a large part of your initiative.

• 25:09Speaker 03

  And you, and what Joanna just hit is the fundamental problem, that really the fundamental problem that we had, which was nobody could tell us how much, how, what were the sources. So now we have three, a triple go, that's really bad, a triple no, let's put it that way. An insanely small number, a guy who's a little bit of a flake, okay, driving it.

• 25:28Janna Levin?

  That would be you?

• 25:30Speaker 03

  Yes, I'm afraid so. And then, nobody can attest that there's real sources, and people at MIT, where I was a, where I was a faculty, saying black holes didn't exist. See, that was a whole backdrop of this as well.

• 25:43Janna Levin?

  So what possessed you to keep going?

• 25:45Matt Kirshen?

  You're trying to persuade them to spend money to detect the effects of something that they don't think exists.

• 25:49Speaker 03

  That's right, and it's a lot of money, a hundred million bucks about.

• 25:52Janna Levin?

  Well, Ray, you didn't know that they existed either. I mean, you didn't know, so what possessed you to keep going? I mean, it is insane.

• 26:00Speaker 03

  Well, I'm gonna give you a very silly, silly answer, which is the truth.

• 26:04Janna Levin?

  Okay.

• 26:05Speaker 03

  A really silly answer. You think I'm a really profound scientist, that's baloney. But I enjoyed the work, and I enjoyed the people. And that was what drove it. I hate to tell you that. It was interesting work to do.

• 26:19Janna Levin?

  I think that's a great thing for people to understand. Scientists do what they do because they love it, not necessarily out of ego satisfaction.

• 26:26Speaker 03

  No, the end result was, it was an interesting result. Could we get such a result? It was a good gamble to take. But that wasn't the thing that drove me, I have to tell you that.

• 26:34Matt Kirshen?

  It is something that I get, because like, when I'm doing my experiments on the effects of paint drinking on blindness, like, it's not, it's not the glory, I'm not going for the glory, it's actually, it's just about the work and it's fun, I enjoy it.

• 26:46Janna Levin?

  And you fully expect, though, that there will be glory at the end of the day.

• 26:48Matt Kirshen?

  Yeah, I expect that there might, there's a bit of me in the back of the mind that's like, yeah, it is gonna cause blindness.

• 26:53Janna Levin?

  You're gonna be the name of a paint color.

• 26:55Matt Kirshen?

  I will be able to write it up. But, at the time, you just do it. You just drink that paint, and you write down your results as best you're able to write.

• 27:03Speaker 03

  So now we get to Kip, because, see, Kip was a different kind of person. Kip was a theorist, okay, and he had spent a lot of his life thinking about what might be the sources of gravitational waves. And in fact, he started writing some very elegant stuff, already in the seventies, early seventies, about if there were a way to measure gravitational waves. What would be interesting to detect?

• 27:26Janna Levin?

  Uh huh.

• 27:27Speaker 03

  And he started inventing a lot of very interesting ideas.

• 27:29Janna Levin?

  So Kip really pushed the science case. And you know, he was so cool headed. He was just totally unflappable in the sense that even when other people were saying, "We won't detect black holes. We won't detect black holes until 2020," some people told me. As recently as August, right?

• 27:43Speaker 03

  Yeah.

• 27:43Janna Levin?

  And Kip was like, "Nope, black holes first. Black holes are gonna be first." So he, he really pushed that scientific case.

• 27:50Speaker 03

  Well, and he had a, and he had good reason because you see, he had developed a very, probably one of the most prestigious groups in the country for the theoretical parts of gravitation. He, it's interesting, Kip and I, we didn't know it. Well, Kip tells me he thinks he remembers, but I don't. We were both at Princeton together at the same time. I was a postdoc, he was a grad student. And by the way, Joe Weber was there also exactly the same time.

• 28:13Janna Levin?

  With John Wheeler.

• 28:14Speaker 03

  With John Wheeler, exactly.

• 28:15Janna Levin?

  The American granddaddy of American relativists, yeah.

• 28:19Speaker 03

  So Kip was, the reason I think what's so important for Kip to be part of it is he gave it a, a certain cachet. I mean, that the fact is, he showed people that it was possible that you could have sources besides the one that anybody, all, everybody knew about.

• 28:35Janna Levin?

  Supernova.

• 28:35Speaker 03

  Which was supernova, yeah.

• 28:36Janna Levin?

  So when a star explodes, it can wobble spacetime, which we now think is probably the hardest thing to go for.

• 28:43Speaker 03

  It's a stinker, it's a find, yeah.

• 28:44Janna Levin?

  So, uh, let's, uh, before we get to the discussion of the actual discovery, let's take some cosmic queries.

• 28:50Matt Kirshen?

  All right, so Gabriel Thielan, who's a Patreon patron, says-

• 28:55Speaker 03

  What kind of Patreon?

• 28:56Matt Kirshen?

  Patreon. It's a website that lets people give money.

• 28:58Janna Levin?

  They are supporters of the fabulous show.

• 29:01Matt Kirshen?

  Financial supporter of the show. And Gabriel asks, "Theoretically, is there anything stopping gravitational waves from traveling faster than the speed of light? Is, uh, it is the same phenomenon, is it not, as a theoretically, a theoretical localized artificial spacetime distortion or warp? Thank you very much."

• 29:20Janna Levin?

  Can I try this one and then Ray, you jump in? So just like there are light waves-

• 29:26Janna Levin?

  Electromagnetic waves, which is radiation, there is a particle complement to that, and that is a massless particle, and it travels at the speed of light. We think that that's exactly analogous to what's happening with gravitational waves, that there's a wave in the gravitational field, and that there is a particle called the graviton, which is massless in Einstein's theory. That might be wrong, but in Einstein's theory, it's massless. And in that case, like all massless things, it travels at the speed of light. No faster, no slower. But that could be wrong. It's very hard to test the speed of light by looking at gravitational waves. I'm sorry, the speed of the gravitational waves. It's very hard to test, isn't it?

• 30:06Speaker 03

  Well, we try to make an attempt. Do you want to hear about that?

• 30:09Janna Levin?

  Yeah.

• 30:10Speaker 03

  I mean, if we ever get... I mean, there's a future and there's a current. I'll give you the future, because it's easier to understand. Now that we are in the business, finally, of detecting things, people will try to look for not just bursts of gravitational waves, but rather ones that are very steady radiators, like, you know, an antenna on a transmitter, blowing its waves out into space.

• 30:29Janna Levin?

  Like a neutron star with a bump on it.

• 30:30Speaker 03

  A neutron star, that's right.

• 30:31Janna Levin?

  It's like a paddle.

• 30:32Speaker 03

  Neutron star with a bump on it that's rotating, and so it gives a nice continuous wave.

• 30:36Janna Levin?

  Like a monotone.

• 30:37Speaker 03

  Yeah, exactly. Well, it's slowly decaying, but it's a monotone. You're absolutely right.

• 30:40Janna Levin?

  Over our time scale.

• 30:41Speaker 03

  And then what happens is a very interesting thing. You can do a very simple thing that even I can imagine. You can look at that source as we move around in our orbit in the solar system, and you will get added time each time, you know, this source will be someplace in the orbit, outside of our orbit, and we go around, and it takes different lengths of time for the signal to get to us. And since we know our velocity, we can get the velocity of light, because we increased the distance to the object. We know how much we increased it by. So it's a very straightforward kinematic measurement. On the other hand, we already have sort of a quasi-measurement of the velocity of the gravitational waves from a simple thing. We saw, I have to explain, as Jenna said, we have two of these detectors. One in Louisiana, another one in Washington State.

• 31:26Speaker 03

  And we saw the signal first, in Louisiana. And seven milliseconds later, we saw it in Hanford, Washington. That already tells you it's moving pretty damn close to the velocity of light.

• 31:36Janna Levin?

  Yeah, as it crosses the continent.

• 31:38Speaker 03

  As it crosses the continent. That's a pretty good way of...

• 31:40Janna Levin?

  It's pretty great. It's a, I love that the seven milliseconds are just clocked. It's fantastic.

• 31:45Matt Kirshen?

  So Nathan Kruger on Facebook says, "Are there currently any plans to conduct the double slit experiment using gravity waves?"

• 31:52Speaker 03

  That's an interesting question.

• 31:53Janna Levin?

  It's so, gravity is so weak, it's so hard to manipulate. Ray, what do you think?

• 31:59Speaker 03

  I'll tell you what the real problem is. Two problems. One of those, you can't make us, you would have to make an artificial source to do that. And when you start doing that, you'll find out that you just don't have the power. You don't, you can't accelerate enough mass and move it fast enough so that you can even detect the waves. And Einstein said this in his very first paper on gravitational waves in 1916. He writes a lovely sentence at the end of the paper, saying, look, he points to all the calculations, he says, "No, there's very unlikely," in fact, he doesn't even say unlikely, "it's impossible that these waves will have any physical consequence that we can measure." Because of that, that he tried to look at things like stars, that what he knew about, or locomotives smashing into each other. I'm making that up because I don't know what he really thought about.

• 32:42Speaker 03

  I mean, that piece of paper that says that's where he did his calculation.

• 32:46Janna Levin?

  Yeah, he didn't believe black holes were real, so...

• 32:48Speaker 03

  Yeah, well, the other thing is, black holes are not even going to be considered at that moment. But just the calculation where he came so pessimistic about this, that I'd like to have to see a piece of paper that has that. He must have done it.

• 32:58Matt Kirshen?

  So the fact that Einstein didn't think black holes are real, and I do, makes me smarter than Einstein? Like, what do we know?

• 33:03Speaker 03

  Just a little later, that's all.

• 33:05Janna Levin?

  If you time traveled to before Einstein and believed in black holes, that would make you pretty smart.

• 33:11Speaker 03

  Oh, boy, Jenna's driving that point.

• 33:13Janna Levin?

  Do we have one last? We've got a minute for our last cosmic theory, really quick.

• 33:18Speaker 03

  I didn't answer the question, but never mind.

• 33:19Janna Levin?

  I'm sorry, I know.

• 33:20Speaker 03

  I don't know, you need to make an artificial source to make an interference pattern.

• 33:23Janna Levin?

  Right.

• 33:24Speaker 03

  And that's why I was, I just don't think we can do it, unless, yeah.

• 33:26Matt Kirshen?

  So Mary NotGonnaTellYa, I don't think that's her real name, I'm almost guaranteeing that it's not, says, "I asked this before as a silly question, but I've been thinking about it, maybe it's not so silly. If gravitational waves were represented by colors, what would they be and why or how?"

• 33:43Janna Levin?

  Hmm.

• 33:43Speaker 03

  That's pretty easy.

• 33:44Janna Levin?

  Well, yeah, I mean, the frequency of the sound can be translated directly to the frequency of light, which is a specific color.

• 33:50Speaker 03

  That's right.

• 33:50Janna Levin?

  So what colors would they be? They'd be, they'd be, uh,

• 33:54Speaker 03

  Well, these would be way, completely out of the eye.

• 33:57Janna Levin?

  Your eye would have to be like the size of a huge radio. I don't know, a very big thing. Oh, I'm sorry to shorten that question, but we have to wrap this part up, this segment. Uh, stick around for more discussion and we're going to discuss the actual discovery of the first black hole collisions. And also the lightning round of your cosmic queries. Stay tuned. We are back on StarTalk All-Stars. I'm your all-star host today, Janna Levin. In the studio with me, we have my comedian co-host, Matt Kirshen.

• 34:31Matt Kirshen?

  Hey, Jana.

• 34:31Janna Levin?

  And our science guest, Ray Weiss, to talk more about the LIGO discovery. Good to see you again 10 seconds later. Now, a lot of people are talking about the discovery, so let's give people a sense of what actually happened. It was about, what, 1.3 billion years ago? Uh, two black holes collided. Now, those black holes might have lived together a long time. What about the gravitational waves when they were far apart, when they first formed black holes, when the stars died? What about those gravitational waves? You had an instrument up in 2000.

• 35:01Speaker 03

  Yeah. Well, let's, let's be honest about why we didn't see it in the year 2000. That's what you're complaining about, right?

• 35:07Janna Levin?

  Well, it wasn't really a complaint.

• 35:09Speaker 03

  We didn't have an, I'll tell you something.

• 35:10Janna Levin?

  Those gravitational waves have been coming across us since multi-solar organisms were fossilizing on the Earth.

• 35:14Speaker 03

  Let's, let's start with what must have been the case with these is, and I think this is probably going to hold even though there are other ideas now about this. But, uh, we, as you say, we saw the thing that happened about 1.2, 1.3 billion years ago. And we saw it at its end point, at the very end, when the two, two black holes were getting closer and closer, they go orbiting around each other. And then all of a sudden, they hit each other and they make a new black hole. That's what they do. This, when you do, they swallow each other as their event horizons come, come, come together. And you wound up with, let's say there were two 30 solar mass stars to begin with. And you wind up with a 57 solar mass black hole when they make a new one. So the first thing you have to explain is where did that three solar masses go?

• 35:57Janna Levin?

  They lost some mass.

• 35:58Speaker 03

  Well, they went someplace. Well, they went in the gravitational waves. And that's unbelievable when you think about it.

• 36:03Janna Levin?

  Right, so it's completely dark. None of it comes out as light.

• 36:05Speaker 03

  Nothing comes out in light.

• 36:06Janna Levin?

  If I pointed a telescope at these two black holes colliding, I would see nothing.

• 36:09Speaker 03

  See nothing, and that's one of the tragedies, because you'd love to be able to see something, so you could identify where it is.

• 36:14Janna Levin?

  Right.

• 36:15Speaker 03

  We don't have the faintest idea where it is in the sky, except for the fact that it hit Louisiana first.

• 36:22Janna Levin?

  From the southern sky.

• 36:23Speaker 03

  From the southern sky and went up. So we have sort of a banana in the sky where we think this thing comes from. But we have sort of a thousand square degrees of ignorance is what we have.

• 36:31Janna Levin?

  So now there's a black hole out there and it's gone quiet, and we can't look at it either.

• 36:35Speaker 03

  Nope, it's gone. And you don't know where to... You don't know where to tell people to go look for it. So that's sort of something we want to fix. But we'll get to how we fix that in a minute. But let's get back to what happened before we saw them, okay? And there is a tricky one. It depends how they got made.

• 36:50Janna Levin?

  Yeah, how did those black holes form in the first place?

• 36:53Speaker 03

  And we don't know how it got made. And that's going to be one of the more interesting scientific questions as we, when we go back on the air and begin to see a lot of these things, we can begin to contemplate. But there are two ideas that people had right away. One thing is a star collapses, that's called common envelope, and they come together and they make two black holes. By the way, Hans Bethe explained to me many years ago, just like Kip, that that's the first thing we would see.

• 37:14Janna Levin?

  Oh.

• 37:14Speaker 03

  That was back in 1990, while he was still alive. So that's one thing. That's one method that could be. Acquires a star that's pretty heavy, 60 solar, 70, 80 solar mass. A big star, a big mammoth star. So where did that come from? Okay, that's a question. But then the other possibility, which is not quite as dramatic, is that we have things which are called globular clusters. What are those? Those are regions in our galaxy, and every galaxy has places where a lot of star formation forms simultaneously. And so here a bunch of stars all zipping around and there's a lot of probability that maybe three of them will get together, bang into each other, and it has to be orchestrated properly, okay? And so they make a thing that's a black hole. Or maybe they have to make two black holes.

• 37:55Janna Levin?

  Why can't it just be a big star that died and made a black hole? It's too heavy.

• 38:00Speaker 03

  Well, yeah, be careful, Jenna. It could be that, and people are thinking that. And some people even, let me now go on, these are the-

• 38:06Janna Levin?

  Let's decay into a very technical conversation.

• 38:08Speaker 03

  This gets into something really quite tricky, but let me say that's what-

• 38:11Janna Levin?

  What about the metallicity of this?

• 38:12Speaker 03

  Ah, no, no, no, no, come on, let's get away from that.

• 38:14Matt Kirshen?

  That was about to be my question.

• 38:15Speaker 03

  Your question, you were gonna ask that, right?

• 38:17Matt Kirshen?

  Yeah, I was gonna ask that.

• 38:18Speaker 03

  Okay, well, to hell with the metallicity for a moment.

• 38:20Janna Levin?

  So we only see the final fraction of a second. How much of that collision do you actually detect? Did LIGO detect?

• 38:26Speaker 03

  LIGO detected only about point two, let's say a quarter of a second of this whole thing.

• 38:31Janna Levin?

  A quarter of a second, so it was emitting the gravitational waves, it just didn't get loud enough until that final quarter of a second.

• 38:35Speaker 03

  Well, be careful, it's two reasons. Yes, you're right, but the real reason we didn't catch it is because our detector can't detect anything with very low frequencies. As I told you, it goes from the bottom of the piano to the top of the piano. So this is a rumble, once they're very far apart, those stars, if they have been stars, if they started far apart, they might not have, you don't know that. Suppose, like every other thing, they started far apart, then they would be going very slowly around each other. Hours, periods of hours.

• 39:02Janna Levin?

  And that would be low frequencies.

• 39:04Speaker 03

  We don't have any sensitivity, but something later in the history of man will have that sensitivity. It's called LISA, that's the space version of LIGO.

• 39:12Janna Levin?

  I love your optimism.

• 39:13Speaker 03

  Well, it's going to happen, maybe not mine, but in your lifetime.

• 39:17Matt Kirshen?

  I'm building my own LIGO at home. What kind of scale should I aim for?

• 39:21Janna Levin?

  Do you know that actually happened to me? I went to the LIGO lab, I'm not actually an experimentalist in the collaboration, so I haven't signed the memorandum of understanding, and there are certain things I'm not allowed to know, but I was looking at the schematic of the lab, and I was like, why am I allowed to see this? And somebody said, what are you gonna go home and build one?

• 39:37Matt Kirshen?

  Yeah, you got a couple. Just you watch me. And then everyone's gonna be really embarrassed when you've done one for like.

• 39:44Speaker 03

  Well, I'll tell you, if you come up with a clever idea that doesn't need something so big, and people at one time thought maybe optical fibers, I won't go into it all. None of these ideas have worked out, but people all the time thinking about how could they make a small version of something like this that is as sensitive. Let me go back, the, the, so what you have is these big things that they're very far, let's suppose they got started separately. And they come, they, they, they are still bound to each other and they eventually oscillate and they get closer and closer and they're losing energy to gravitational waves, which we're not detecting because it's outside of our band. Then we detect it just as it comes into our band.

• 40:18Janna Levin?

  I see.

• 40:18Speaker 03

  That's the most likely explanation, but there are others too.

• 40:21Janna Levin?

  Right. Now, you were really hoping for the centenary, for the first detection. So here you've been building this thing for 50 years, Ray. I can't tell you how many times somebody said to me, we better go ask Ray. You know, on site, you're doing experiments, you're, you're walking the beam tubes and you want it to be 2015. You wanted that so badly, I know.

• 40:41Speaker 03

  16 or 15 was good, 16 was the latest.

• 40:44Janna Levin?

  Okay, so you were willing to take 16 and then if not that, you would find an Einstein paper that was, you know.

• 40:49Speaker 03

  2018 paper, but that was it.

• 40:51Janna Levin?

  No, a lot of people told me 2018, don't expect a detection before 2018. But on September 14th, 2015, this struck. It must have blown your mind. I mean, what is the experience of waking up that morning and checking the logs?

• 41:07Matt Kirshen?

  I'm thinking it was like, it was the practice run that, like, that wasn't meant to be the run that detected anything, right?

• 41:13Speaker 03

  You're absolutely on the mark, that's correct, yeah. It's even worse than that. What happened is we, we didn't expect this and when, as Chana points out, I happened to be on vacation, I had been at the site the days before that. And I almost screwed it up. Do you know that story?

• 41:28Janna Levin?

  Yeah.

• 41:28Speaker 03

  But I do want to tell you the story because I, I was sent by, by my boss, Peter Fritschel, who is the young student that I had and now is a senior member of this thing. He says, why's you gotta go down there, fix the RF interference?

• 41:40Janna Levin?

  Radio frequency.

• 41:41Speaker 03

  Radio, radio frequency interference. And because it'll disturb the whole run. So I went down there and I saw what was really a big mess. I mean, FCC, you know, the Federal Communications Commission would have sent their truck there and shut us off because we put out so much RF. And then I found out the problem was, and I said to Peter. Look, this is gonna take a week to fix up. I can't, I don't. They had a big conference and the reason why they told me no was that they had committed themselves to making a run two days later.

• 42:10Matt Kirshen?

  I just left it like it was.

• 42:11Speaker 03

  It was a run and you had to, and he said, "Look, we have all these people coming from all over the country, all over the world, coming to the sites. We don't want to jeopardize this and the RF, if it's a problem, well, it can't kill us." And I said, "No, it won't kill us for impulsive source, but if you're looking for periodic sources, it might." And so we took that gamble and Peter said, "Let's come home." And thank God I went on.

• 42:32Janna Levin?

  Twenty-four hours later.

• 42:34Speaker 03

  It was about three, two days later. Three, it was a Thursday. The thing happened on a...

• 42:39Janna Levin?

  It happened on a Monday.

• 42:40Speaker 03

  It happened on Monday, so it was four days later.

• 42:42Janna Levin?

  So you checked...

• 42:43Speaker 03

  And so you asked, "What did I think?"

• 42:45Janna Levin?

  Yeah, you check the log, you wake up, 8 a.m. in Maine.

• 42:48Speaker 03

  Well, I'll tell you what happened, it was really cute. I went to log, we were on vacation. My wife and son were with me and her, and his, and his wife. And I was looking at the log, which I do every morning, and I see this thing, which was very cryptic. It says, "We're canceling a fix-it day." Now, we have fix-it day every Tuesday. We have running, in the middle of a run, even in an engineering one, when we find all these things wrong, we don't want to mess with the apparatus, but we do it at a certain time so both sites are dead at the same time. And they said, "No, we're canceling it." And so I look at the other site, same damn thing. "We're canceling fix-it day." So I call up, "What's the hell, what's going on?" And they say, "Well..." And then it didn't take long, I began to get email. And then very quickly, within about half an hour after that,

• 43:33Speaker 03

  I saw an absolutely magnificent curve. It was this signal, which now is on people's dresses, it's in everywhere. And it was this, this, this binary black hole, thirty solar masses. And I look at it, it says, "Holy mackerel, this has got to be a fake."

• 43:46Matt Kirshen?

  Really mackerel that you said?

• 43:48Speaker 03

  Yes. Well, maybe not. I'm trying to be cheerful.

• 43:51Janna Levin?

  He's cleaning it up for air. If I know you, Ray, that's not what you said.

• 43:55Matt Kirshen?

  Holy smokes, do you whiz?

• 43:57Speaker 03

  No, none of those.

• 43:57Matt Kirshen?

  You're a nineteen twenties paper boy. Hey, mister, mister, he got some scoops.

• 44:03Janna Levin?

  It was really something when in February, all these months later, the announcement was made and everybody just shared in this incredible excitement. That was really a moment in history.

• 44:11Speaker 03

  It was. Well, we did a lot of work between the time we found it and then because we didn't believe it.

• 44:17Janna Levin?

  Yeah.

• 44:17Speaker 03

  Let's be honest. I mean, Jana, that was such a big signal. We never expected such a big.

• 44:22Janna Levin?

  Right. Amazing. Okay, we're gonna go quickly to the lightning round. Are we ready?

• 44:26Matt Kirshen?

  All right.

• 44:27Janna Levin?

  Rapid fire.

• 44:28Matt Kirshen?

  Carl West on Instagram says, would it be possible for gravitational waves to alter matter as it passes through? E.g. if matter was too close to the source, the gravitational waves could have become damaged or altered by the sheer energy or force of the waves propagating through the fabric of spacetime.

• 44:41Speaker 03

  That's so easy to answer so fast. Gravitational waves are the most penetrating things that are that man has ever encountered. They go through everything. Nothing's gonna stop them.

• 44:51Janna Levin?

  They go right through the earth.

• 44:52Matt Kirshen?

  All right. Do gravitational waves cancel each other out like sound waves?

• 44:57Speaker 03

  No.

• 44:59Matt Kirshen?

  Beautiful.

• 45:00Speaker 03

  Let me be parenthetic about it. They could, but it would be taking enormous amount of precision to do that. You could have a compression while the other one has a rare fraction.

• 45:10Janna Levin?

  Like water.

• 45:11Speaker 03

  It's not impossible, but my god, in the real world, it's not gonna happen.

• 45:14Matt Kirshen?

  All right. If two black holes collided near us, would the gravitational waves be strong enough to disrupt our own magnetic field? What could happen because of that clash?

• 45:25Speaker 03

  Well, if that collision happened in our solar system, we would be, we might not even be here.

• 45:31Speaker 03

  I'll tell you what happens. We would get.

• 45:32Janna Levin?

  In our solar system, yeah.

• 45:33Speaker 03

  Yeah. We would be stretched and compressed in such a ways that things could easily come apart.

• 45:39Matt Kirshen?

  That question, by the way, was from Mike Schneider's on Facebook.

• 45:41Speaker 03

  Okay.

• 45:43Matt Kirshen?

  David Norio on Facebook says, why are we referring to gravity as a force since it's the result of the curvature of spacetime? And what about the other forces? Are they also the result of something we can't see yet?

• 45:54Speaker 03

  Well, that's an interesting question, and I can't answer it because it may very well be. We don't have the final theory, but maybe you should try that.

• 46:00Janna Levin?

  We're loose in this language. It's true that Einstein made us realize that in some sense, gravity is not a force, that we're falling freely in a curved spacetime. We're not actually being touched and pulled upon. But there's another way to look at it that makes it look like a lot of the other forces. So, electric fields permeate space and affect things. Gravitational fields permeate space and affect things. There's a way of making them sound more parallel.

• 46:18Speaker 03

  Yeah.

• 46:19Janna Levin?

  And there's always force carriers. Gravitational waves, light waves, weak force carriers that gauge those on and off.

• 46:25Speaker 03

  You can recast gravitation as Steve Weinberg did, for example, as a field theory, if you want. You don't have to use Einstein's beautiful theory.

• 46:32Janna Levin?

  Well, what people say is if Einstein hadn't discovered curved spacetime theory, we'd be talking about it in this much more particle physics-y sort of a way.

• 46:40Matt Kirshen?

  All right. The Scarlet Speedster on Twitter says, "How do gravitational waves affect time slash perception of time? What would need to occur to have significant changes?"

• 46:51Speaker 03

  Well, I don't know if I can answer that. The metric that I use does not have the clocks perturbed by the gravitational waves.

• 46:59Janna Levin?

  This is tricky. Yeah, so it's like, what I call left isn't what you call left. It's a mixture of your left and right. We tend to orient our spacetime so that it's only the space that changes, not the time. But you could orient your spacetime differently, where you would measure it being in the time direction. It's not easy stuff.

• 47:17Matt Kirshen?

  All right. Tony Hale on Facebook says, "Do gravitational waves reflect light? And if so, could you dial in an image like flipping a page in a book? If we can't see our galaxy in the past, but the light reflected from our galaxy is traveling faster than we are, would that mean we could see an image bounce back at us?"

• 47:33Speaker 03

  I don't think that'll happen, but let me tell you something. There's a very nice way of thinking about gravitational waves affecting the propagation of light. You don't have to have mirrors doing it. In other words, they interact to make sidebands on the light. That's a complicated way of saying it, but you... For example, some of the other ways of looking at gravitational waves do not use mirrors, like the pulsar timing. Does not use mirrors. So consequently, there's an interaction between gravitational waves and the propagation of light.

• 48:00Janna Levin?

  Yep, that is some hard stuff. I'm not even going to try to clear it up because we're at the end of our show. Thank you so much for the excellent questions. It's been a great show today. Ray, always an honor and a pleasure to talk to you. Matt, so great to have you on. Check out Probably Science, @MattKirschen on your Twitter feed. Thanks so much for being here with me. This has been StarTalk All-Stars. Thanks for listening. See you in the multiverse.