StarTalk Radio - Deciphering Gravitational Waves, with Janna Levin

Episode Date: December 20, 2024

What is a gravitational wave? Janna Levin and comedian Matt Kirshen sit down with physicist Rainer Weiss to discuss LIGO, black holes, and the physics of gravitational waves. (Originally Aired October 4, 2016)NOTE: StarTalk+ Patrons can listen to this entire episode commercial-free here: https://startalkmedia.com/show/deciphering-gravitational-waves-janna-levin-startalk-stars/ Subscribe to SiriusXM Podcasts+ on Apple Podcasts to listen to new episodes ad-free and a whole week early.

Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now. Welcome to StarTalk All-Stars. I'm Jana 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. Thank you, Jenna. How's it going? Welcome back. Thanks for having me back.

It's been like 10 minutes. Yeah. It's nice to be here in space. 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. Thank you, Jenna. 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? It happened last year. 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. 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 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 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 oh I'll try but I you know I was as mystified as you in the fact that it had this

enormous public recognition oh yeah I mean you take other were you surprised I was more than surprised I was flabbergasted to be honest with you oh really, yeah. I mean, you take other things. Were you surprised? I was more than surprised. I was flabbergasted, to be honest with you. Oh, really? 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 a walk-in closet.

Right. I said, where in the hell does that come from? Yeah, exactly. And then— It was a Jeopardy question. Is that what it was? Yeah, no, also, as well. Oh, I didn't realize that.

I didn't realize that. Have you—has science now detected an apartment in New York with a walk-in closet? I haven't been looking lately, but I don't live here. 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. 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, we all learned 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 the velocity of light. Right, so if the sun

disappeared tomorrow, it should take us eight minutes. Well, that's right. If the sun disappears, well, yeah, it'll take about eight, nine minutes before we really know about it. It's great if you're like a magician or something. Do you need the extra time? Well, yeah, because David Glontill made the Statue of Liberty disappear, but he had like seconds

really to do that in. If you had eight minutes to play with. You could do anything. You could be an amateur magician. You'd have time to get some helpers to actually shove it out of place. What did you do with the sun, Matt? Yeah, but those eight minutes are damned important. Right.

Because they tell you that there has to be some mechanism for information to travel not infinitely quickly. Right. So in Newton's theory, it would happen instantaneously. 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... Okay, Ray's oscillating

his hands in and out. Oh, yeah. I got to tell you, that's right. Waving my hands back. Almost like a slinky spring. 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. I hope you all use right-handed coordinate systems. It's stretching 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. 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. 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 you already like before the show even started

he was using his hands wildly before the show started you were kind of looking at the microphone and like taking it apart like you can't help yourself no you can't you can't switch

yeah you gotta do that you gotta find out what you're surrounded by come on that's part of the world palpate palpate the world so you know

it's tactile and it's all sort of seeing things. Anyway, so as Jana says, 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. 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. So here I go, and they ask 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. And this would have, his campaign started in the 50s to 60s. No, this would start in the 60s.

60s, the late 60s. 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. He was incredibly famous. Well, yeah. And he was lying? He was just...

No, no, no. Don't say lying. That's not the right word. We're all very defensive about Joe now. I don't want to brag, but I also did discover gravitational waves like about a month before you guys. That's good. I'm glad of that.

What did yours look like? It was like I just put a cup on a table and it kind of wobbled a bit. And then water wobbled and he knew that they were gravitational waves. It's like those Jurassic Park. It's like those two birds in the New Yorker cartoon. You probably saw that cartoon. I didn't see it. Two Like those two birds in the New Yorker cartoon. Probably saw that cartoon. I didn't see it. Two birds sitting,

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

prior information. But these two birds, two birds are looking one way, one way, looking at the other and for one says, hey, did I hear you

or was that a gravitational wave? Actually, it's already, that's the kind of thing. But anyway, so let me get back to the story. The thing was that they asked me about this. And I frankly, to 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, 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. Yeah.

Very straightforward measurement. And they'd have to be sort of floating so that— Floating out there. Like bobbing on the wave of the ocean if something floats on the ocean. 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 gravity- But you started to build one. Well, yeah, yeah, yeah. Right away. But that's the basic idea. And by the way, that idea is the one that propagated into the later on LIGO and everything else. 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. That's right. And then you dreamt up, which is basically a cosmic recording device, a sort of insane, gigantic cosmic recording device to record sounds from space. 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 awesome you you because i think you have a musical background or around you as music and yeah understood this right away yeah it's absolutely true it was yeah so what's the book called um 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 air it. You just play that in at that point. Right, exactly. Just edit that in.

But so you, this is, okay, early 70s now we're talking about. Yeah, right. Okay, so that's 50 years ago. And you started to build the first machine, but it was really quite small. And as I remember, you got a lot of flack for it because nobody thought you were going to succeed. They thought you were wasting your time. I was really quite small. And as I remember, you got a lot of flack for it because nobody thought you were going to succeed. They thought you were wasting your time.

I was worse than that. 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 had no onus associated with it in the society. And what happened was that they supported this and what happened, I got about $50,000 to build a small prototype. Then all of a sudden everybody got very disenchanted with the military when the Vietnam War happened.

The funding for this- Because you're funding. Funding stopped because the military was only supposed to support those things that were relevant to its mission. Gravitation waves weren't quite in 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. Right. How can we use gravitational waves to kill our enemy? Like, how can we?

Well, if it gets there, I'll tell you later. We'll do that in segment three. If you care to pursue this, I'll tell you later. Or at least just, like, upset someone. Like, how can I use it to upset a neighbor? Like, my neighbor's playing music too loud i'm gonna send gravitational waves towards them full blast another master of gravity right that's what we're dealing with here 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 all right send us your messages it's too late now of course it is too late well is it i don't know it depends if we can time travel can gravitational waves help us time travel you know might as well ask this question then this is perfect unintentional timing here but jake the guy on instagram uh is asking uh does any of this mean i can travel in time ray do gravitational waves help us travel in time. Ray? Do gravitational waves help us travel in time? I don't know how they would,

but maybe you have an idea. You're a theorist. 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. That's a cop-out, though. Like, we're down here right now. 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. Okay, by going off to space and coming back. 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. All right, Taylor from Eugene, Oregon. We did a fairly lousy job of answering him.

It was a good enough. Yeah. I'm pretty sure Ray just said I gave a lousy answer. You did give a lousy answer. And there's only one person in the world I would take that from. Probably want something very deep.

It was deep. You just weren't paying enough attention. 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? Well, that's a question I can even answer. And in fact, if we measured this event from two black holes. I have to

start that way, which was, fortunately for us, 1.2 billion light years away. Had we been, let's say, within a few tens of years of that, we would have measured something. You would have measured exactly what we measure in our detectors. You wouldn't have stretched in one dimension and compressed in the other dimension. You would have measured exactly what we measure in our detectors. You wouldn't have stretched in one dimension and compressed in the other dimension. You would have felt that. 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? I don't think that's—that's not because—

I've been saying this for months. Well, I don't think it's true. Well, I think—let's's, that's not because, I've been saying this for months. Well, I don't think it's true. Well, I think, let me, let's get to that issue right away because we've,

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 nothing, 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 mile, one year away, light year away, is still too small for your ear. So how close do you think? Oh, yeah, I would agree with that. If you got close enough, you would feel it. But if you got close enough. You would feel it over your whole body.

And you might hear something. But that's not what we're doing. So like a sound wave is like the compression and expansion of the air around you. That's right. And this is actual space itself is doing that. 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. What we do is we have a device that measures these very tiny displacements with 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. Look, the important... It's a lot like an electric guitar. Exactly, but exactly like an electric guitar. Yeah. You've got a very good analogy. Very good analogy.

And the other thing is that it's an... The other piece of it is that this phenomena, these phenomena we're seeing, phenomena we're 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. That's just by chance. That just happens to be in there. That's because the things we're looking at, well, it's a little more than that.

What it is is our instrument's only sensitive in that band, okay? 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. A couple of black holes collide. They happen to ring space-time in the human auditory frequency.

So let's... Yeah, okay, but it's not sound waves traveling through space. I just don't want to have that... Just like an electric guitar string is not a sound wave traveling through space. Exactly, that's a wonderful analogy for people. But you had to build LIGO to build Just 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. That's a beautiful analogy. Excellent. And then we're going to all break out into air style guitar. Give us another Cosmic Query. From Florida, Sarah Garvey Jansa 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 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? 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. Because what happens if you take an ordinary star, that might be 30 solar masses. It was surprising how big they were. They what?

It was surprising how big they were. Yeah, but monstrous. It was exciting. Yeah, monstrous. I mean, all the black holes people had seen, or nobody had seen a. Yeah, but monstrous. It was exciting. Yeah, monstrous. I mean, all the black holes people had seen, or nobody had 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 jiggling around, you then say, my God, look how close they are from the equations. You can say, they're much closer than any star. They would be inside of each other. Yeah, they're a couple hundred kilometers across. These things are no bigger than the be inside of each other. Yeah, they're a couple hundred kilometers across. These things are no bigger than the size of Connecticut, maybe. Yeah. Or even smaller, maybe. The only thing that's that big that can also be that close are black holes.

Well, that's the argument. That's fundamentally the argument. That's the best we can do. That's actually the argument. So maybe there's something else that when we got close, we realized didn't have an event horizon, wasn't a complete shadow, wasn't really empty space-time. It can be different than what we think of a black hole as, but it's got to be heavy and small.

I'm Jasmine Wilson, and I support StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson. 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. I'll tell you what the next event was. The next event was really trying to get money. That was the next event. I tried to finish it. And that's what happened. Kip comes soon. But the next event was really trying to get some money. And that's where I ran into the trouble. I said there were trouble getting that money, getting that.

People were skeptical. And your instrument was a meter and a half. Yeah, the initial prototype was a meter and a half. If we wanted to just demonstrate, it was never intended to make a detection. In fact, nothing until LIGO was even ever able to contemplate making a detection. Didn't somebody tell you I could do better by looking out the window?

If the sun blew up, you couldn't detect it? Yeah, well, one of my graduate students, the first time I ever put a graduate student on the project, had a terrible time 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 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. 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.

This is after your grant was declined. Yes. Well, yeah, that's right. Yeah, it was declined. So here you are with no money. Yeah, yeah. Here I am in 1975 or so. We had started building the thing in 72.

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. Right. Sometimes not seeing something is better than seeing something, they had done a beautiful job of not seeing anything. Sometimes not seeing something is better than seeing something, especially if it's not there. In that case.

Or like if you're talking about my dancing. It's better to not see. To not see. Every scientist will tell you that. So because you make confusion if you see something that's there and that's not supposed to to be there and so a lot of things there that are not supposed to be there. Yeah so what happened is very good so what they did is they asked me if they 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. Here they are they're kind

of pulling ahead on your idea. They pulled way ahead. They pulled ahead on your idea. They had funding. They had funding, and they were very good. Besides, give them credit. They were superb. Right.

And that also started my colleague, Ron Drever, 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.

Now, eventually... So that's, after that is when I met Kip. Right, so eventually it becomes you, Kip, and this is now fast-forwarding 10 years, you, Kip, and Ron Drever 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. So LIGO started 30 years ago. 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 the KIP, getting the KIP. It has a little prelude that, in 83. Because what happened is we did a study. This is the KIPP, getting the KIPP. It has a little prelude to it yet. 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.

Right, so here you had a 1.5 meter machine and how big did you decide it had to be? 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. Right. And I wanted to do 10. A thousand fold.

Yeah, well, I want to do 10. You had like something that was about like a bit. Yeah, that's right. Yeah, arm span to it doesn't fit on the MIT campus or even in Cambridge, Massachusetts anymore. Most of my experiments like the size of a matchbox. Right. Nowadays, they even get smaller,

you know, these nanotechnology things. But you can't do gravitational waves for that wave. 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 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 object's already apart. And that number, that ratio, is a constant. Yeah, it's very small. So LIGO now has these mirrors suspended at the corners of this L-shaped,

four kilometer long, two instruments on two different coasts, one in Louisiana and one in Hanford. By how much are the mirrors displaced? You're describing that that's the same. So for four kilometers? Do you mind if I use the exponential notation? I have to. I can translate. You can translate. Well, it's 10 to the minus 18 meters. Which is a million trillion. Okay. You like that? Fine.

A millionth of a trillionth of the size of the arm. So over four kilometers, it's very small. Which is how, it's like. 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. Right. So that comes to about a 10,000th of the width of a proton. Exactly.

Yeah. That's exactly right. You had to convince who to let you build this? Well, a lot of people. and that was the thing you'd see. When you 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 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 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. Now why should they trust me? That's the other problem. I had no recommendation for that. Well, plus, people weren't even sure there were black holes out there for a large part of your initiative.

And what Jana just hit is the fundamental problem, really the fundamental problem that we had, which was nobody could tell us how much, 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. You think that would be you? Yes, I'm afraid so. And then nobody can attest that there's real social, and people at MIT where I was a faculty, saying black holes didn't exist.

See, that was a whole backdrop of this as well. So what possessed you to keep going? You're trying to persuade them to spend money to detect the effects of something that they don't think exists. That's right, and it's a lot of money, 100 million bucks about. Well, Ray, you didn't something that they don't think exists. That's right. And it's a lot of money, 100 million bucks about. 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. Well, I'm going to give you a very silly answer, which is the truth. Okay. 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. 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. 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. It is something that I get, because when I'm doing my experiments on the effects of paint drinking on blindness, 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. And you fully expect, though, that there will be glory at the end of the day. Yeah, I expect that there might. There's a bit of me in the back of my mind that's like, yeah, it is going to cause blindness. You're going to be the name of a paint color. 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. 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 70s, early 70s, about if there were a way to measure gravitational waves, what would be interesting to detect. And he started inventing a lot of very interesting ideas. 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? And Kip was like, nope, black holes first. Black holes are going to be first. So he really pushed that scientific case. Well, and he had good reason because, you see, he had developed probably one of the most prestigious groups in the country for the theoretical parts of gravitation. 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. With John Wheeler. With John Wheeler, exactly. The American granddaddy of American relativists. So Kip was the reason, I think, what's so important for Kip to be part of it is he gave it a certain cachet. I mean, the fact is he showed people that it was possible that you could have sources besides the one that everybody knew about. Supernova.

Which was supernova, yeah. So when a star explodes, it can wobble spacetime, which we now think is probably the hardest thing to go for. Yeah. It's a very hard source to discover. So let's, before we get to the discussion of the actual discovery, let's take some cosmic queries. All right. So Gabriel Thielen, who's a patreon patron says what kind of patron patreon it's a website

that lets people give their supporters of the fabulous show 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 or theoretical localized artificial space-time distortion or warp thank you very much um can i try this one and then ray you jump in so just like there are light waves 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? Well, we try to make an attempt. Do you want to hear about that? Yeah. 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 an antenna on a transmitter blowing its waves out into space. Like a neutron star with a bump on it. A neutron star, that's right. It's like a paddle. A neutron star with a bump on it that's rotating. And so it gives a nice continuous wave. Like a neutron star with a bump on it. A neutron star. That's right. It's like a paddle. A neutron star with a bump on it that's rotating. And so it gives a nice continuous wave. Like a monotone.

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

The source will be someplace outside of our orbit, and we go around, and it takes different lengths of time for the signal to get to us. Since we know our velocity, we can get the velocity of light because we increase the distance to the object. We know how much we increased it by. 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. 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. Yeah, as it crosses the continent. As it crosses the continent. That's a pretty good way of— It's pretty great. I love that the seven milliseconds are just clocked. It's fantastic.

So Nathan Kruger on Facebook says, are there currently any plans to conduct the double slit experiment using gravity waves? That's an interesting question. It's so, gravity is so weak, it's so hard to manipulate. Ray, what do you think? I'll tell you what the real problem is. There are 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 that, you'll find out that you just don't have the power. 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, it'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, what he knew about, or locomotives smashing into each other. We're not making that up because I don't know what he really thought about it.

I mean that piece of paper that says that's where he did his calculation. Yeah, he didn't believe black holes were real, so. Well the other thing is black holes were not even going to be considered at that moment. But just the calculation where he came so pessimistic about this, I'd like to have to see a piece of paper that has that. He must have done it.

So the fact that Einstein didn't think black holes are real, and I do, makes me smarter than Einstein? No, just a little later, that's all. If you time-traveled to before Einstein and believed in black holes, that would make you pretty smart. Oh, boy. Can't survive on that point. Do we have one last?

We've got a minute for our last Cosmic Theory. Really quick. I didn't answer the question, but never mind. I'm sorry. I know. I don't know. You need to make an artificial source to make an interference pattern. Right.

And that's why I was, I just don't think we can do it. So Mary Not Gonna Tell Ya, 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? Hmm. That's pretty easy.

Yeah, I mean, the frequency of the sound can be translated directly to the frequency of light, which is a specific color. So what colors would they be? They'd be well outside to the frequency of light, which is a specific color. So what colors would they be? They'd be well outside of the eye. Completely out of the eye. Your eye would have to be like the size of a huge radio. I don't know. Very big thing. 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? 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. Yeah. Well, let's be honest about why we didn't see it in the year 2000.

That's what you're complaining about, right? Well, that's really a complaint. Those gravitational waves have been coming across us since multi-celled organisms were fossilizing on the Earth. Let's start with what must have been the case with these. And I think this is probably going to hold even though there are other ideas now about this. is, and I think this is probably going to hold even though there are other ideas now about this. But 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 black holes were getting closer and closer. They were orbiting around each other. Then all of a sudden, they hit each other and they make a new black hole. That's what they do. They swallow each other as their event horizons come together. And you wound up with, let's say, there were 230 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? They lost some mass. Well, they went someplace. They went into gravitational waves. That's unbelievable when you think about it. Right. So it's completely dark. None of it comes out as light. Nothing comes out as light. If I pointed a telescope at these two

black holes colliding, I would see nothing. 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. Right. We don't have the faintest idea where it is in the sky, except for the fact that it hit Louisiana first. From the southern sky. From the southern sky and went up. So we have sort of a banana in the sky where except for the fact that it hit Louisiana first.

From the southern sky. 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 a sort of a thousand square degrees of ignorance is what we have. So now there's a black hole out there and it's gone quiet and we can't look at it either. Nope, it's gone. And 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. Let's get back to what happened before we saw them. Okay? And there is a tricky one. It depends how they got made.

Yeah, how did those black holes form in the first place? 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. Okay, that was back in 1990. By the way, he's still alive. So that's one thing, that's one method,

and that could be, acquires a star that's pretty heavy, 60 solar, 70, 80 solar mass. It's a big star. Yeah, big star, 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 are 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 oh, I thought 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. Why can't it just be a big star that died and made a black hole? It's too heavy. 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 k into a very technical conversation this gets into something really quite tricky but let me say that's about the metallicity of this come on let's get away from that but the uh that was about to be my question i mean your question you were gonna ask that right i was gonna ask okay well the hell with the mentalist so we only see the final fraction of a second. How much of that collision do you actually detect? Did LIGO detect? LIGO detected only about 0.2, let's say a quarter of a second of this whole thing.

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. Well, be careful. There'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. We 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. That would be low frequencies. That'd be very, 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. I love your optimism. Well, it's going to happen. Maybe not in mine, but in your lifetime.

I'm building my own LIGO at home. What kind of scale should I aim for? Do you know what actually happened to me? I went to the LIGO lab. I'm building my own LIGO at home, what kind of scale should I aim for? Do you know what 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 going to go home and build one? Yeah.

You got a couple. Just you watch me. And then everyone's going to be really embarrassed when you've done one for like... 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. So what you have is these big things that they're very, let's suppose

they got started separately and they come, 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. I see. That's the most likely explanation but there are others too. 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. On site, you're doing experiments, you're walking the beam tubes, and you want it to be 2015. You wanted that so badly, I know. 15 was good. 16 was the latest. Okay, so you were willing to take 16, and then if not that, you would find an Einstein paper that was, you know.

It's a 2018 paper, but that was it. 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? I was thinking it was the practice run. That wasn't meant to be the run that detected anything, right? You're absolutely on the mark.

That's correct. It's even worse than that. What happened is we didn't expect this. And as Jana points out, I happened to be on vacation. I had been at the site the days before that. And I almost screwed it up. You know that story. Yeah.

But I do want to tell you the story because I was sent by my boss, Peter Fritchell, who is the young student that I had. And I was a senior member of this thing. He says, Weiss, you've got to go down there and fix the RF interference. Radio frequency. Radio frequency interference. And because it will 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 going to take a week to fix up. I can't, I don't. And they had a big conference, and the reason why they told me no was because they had committed themselves to making a run two days later.

I just left it like it was. It was a run, 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 an 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 home. 24 hours later. It was about three days later. It was a Thursday.

The thing happened on a Monday. It happened on Monday. So it was four days later. And so you checked and so you asked what did I think yeah you check the log

you wake up 8am in May well I'll tell you what happened it was really cute I went to the log we were on vacation my wife and son were with me

and her and her 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 cancelling fix-it day. Now, we have fix-it day every Tuesday. We are 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. 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 very quickly within about half an hour after that, I saw an absolutely magnificent curve, which was this signal, which now is on people's dresses. It's in everywhere. And it was this binary black hole, 30 solar masses. And I look at it and say, holy mackerel, this has got to be a fake.

Really mackerel that you said? Well, maybe not. I'm trying to be careful. He's cleaning it up for air. If I know you, Ray, that's not what you said. Holy smokes, gee whiz. No, none of those. You're a 1920s paper boy. Say, mister, mister, you got some scoops.

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. It was. Well, we did a lot of work between the time we found it and then because we didn't believe it. Let's be honest. I mean, Jana, that was such a big signal. We never expected such a big signal.

Right. Amazing. Okay, we're going to go quickly to a big signal. We never expected such a big signal. Right. Amazing. Okay, we're going to go quickly to the lightning round. Are we ready? All right. Rapid fire. 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 space-time? That's so easy to answer so fast. Gravitational waves are the most penetrating things that man has ever encountered. They go through everything. Nothing's going to stop them.

They go right through the Earth. All right. Do gravitational waves cancel each other out like sound waves? No. Beautiful. Let me be parenthetic about it. They could, but it would take an enormous amount of precision to do that. beautiful let me be parenthetic about they could but it would be

take an enormous amount of precision to do that you could have a compression while the other one is a rare fraction like water

it's not impossible but my god in the real world it's not going to happen alright if two black holes collided near us what

would the gravitational waves be strong enough to disrupt our own magnetic field? What could happen because of that clash? Well, if that collision happened in our solar system, we might not even be here. I'll tell you

what happens. We would get stretched. In our solar system, yeah. We would be stretched and compressed in such a way that things could easily come apart. That question, by the way, was from Mike Schneiders on Facebook. Okay. David Norio on Facebook says, why are we referring to gravity as a force

since it's the result of the curvature of space-time and what about the other forces? Are they also the result of something we can't see yet? 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. 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 space-time. 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.

And there's always force carriers, gravitational waves, light waves, weak force carriers, the gauge goes on and on. 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. Well, what people say is if Einstein hadn't discovered curved space-time theory, we'd be talking about it in this much more particle physics-y sort of a way.

All right. in this much more particle physics-y sort of a way. 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? 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. 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 space-time so it's only the space that changes, not the time. But you could orient

your space-time differently where you would measure it being in the time direction. It's not easy stuff. 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?

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. Yeah, 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. Thank you for having me. And a pleasure to talk to you. Matt, so great to have you on. Thanks so much for being here with me. This has been StarTalk All-Stars.

Thanks for listening. See you in the multiverse.