StarTalk Radio - Deciphering Gravitational Waves, with Janna Levin - StarTalk Allstars

Episode Date: October 4, 2016

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. Subscribe to SiriusXM Podcasts+ on Apple Podcasts to listen to new episodes ad-free and a whole week early.

This is StarTalk. 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. 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, 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. You kindly let me perform. You slogged with me in a tunnel, I remember. 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. 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. I'll try, but I was as mystified as you

in the fact that it had this enormous public recognition. Oh, 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 an old walk-in closet. Right. I said, where in hell does that come from? Yeah, exactly. And then— It was a Jeopardy question. Is that what it was? Okay. Yeah, no, also, as well. Oh, I didn't realize that. I said, where in hell does that come from? Exactly. It was a Jeopardy question. Is that what it was?

Okay. No, also, as well. Oh, I didn't realize that. In addition. I didn't realize that. Has science now detected an apartment in New York in the 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, 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 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 Glomfield 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. 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. 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 a very special thing, so 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 gotta tell you that's right

waving my hands 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 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 Janet'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 yeah you gotta do that you gotta find out what you're 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

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. 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 his campaign started in the 50s to 60s. No, this was started in the 60s.

60s to 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 people and it kind of wobbled a bit. And the 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 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. Right. But these two birds, two birds are looking. One of them looking at the other.

And the 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, 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.

Very straightforward measurement. And they'd have to be sort of floating. 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 does. But you started to build one. Well, yeah, yeah, yeah.

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, 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. Because I think you have a musical background or around you is music and understood this right away. Yeah. It's absolutely true. It was. 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 air it. 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. Yeah, right. Okay, so that's 50 years ago. And you started to build the first machine, but it was really quite small. Yeah. 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. It had no onus associated with it in the society.

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

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.

Right. I'm going to send gravitational waves towards them. Full blast. We're now the master of gravity, right? That's what we're dealing with here? Well, we're going to come back. We're going to come back to this discussion. But before then, I think it's time for us to take some cosmic queries. So if you are out there in the ether, 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 what? Might as well ask this question then. It depends if we can time travel. Can gravitational waves help us time travel? 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? 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? 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 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, 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, 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. 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 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 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. Right. 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 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.

It's a lot like an electric guitar. Exactly, but exactly like an electric guitar. I see. You've got a very good analogy. Very good analogy. The other thing is that the other piece of it is that these 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's because the things we're looking at, well, it's a little more than that. What it is is our instrument is only sensitive in that band. On top of that, nature is 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. Okay.

So it's not sound waves traveling through space. I just don't want to have that. It's like an electric guitar string. It's not a sound wave traveling through space. That's a wonderful analogy for people. But you had to build LIGO to build the body of the guitar. That's the guitar. To record the shape.

Absolutely. Of the wave. That's a beautiful analogy for people. But you had to build LIGO to build the body of the guitar. That's 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 Garvijansa 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? Boy, that's a profound question. And this has a lot of different pieces to 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 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 are 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 size of Connecticut, maybe, 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. Exactly 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 could be different than what we think of a black hole is, but it's got to be heavy and small.

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. 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 Eleven. 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! Matt, comedian and host of Probably Science podcast, which is very funny. Thank you.

It is a long rambling, they have no rules, and that's what we love about them. It started off saying funny, and then it went long and round. They were like, you're next. Oh, it's dreary, it's a dirt, they have a long point. 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. I'll tell you what the next event was. The next event was really trying to get money. That was the next event. I had to try 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, it 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 Ph.D. 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. 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, especially if it's not there. In that case. I like to be talking about my dancing. It's better to not see.

Better to not see. Every scientist will tell you that. So because you make confusion if you see something that's there, that's not supposed to be there. There are a lot of things there that are not supposed to be there. 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. 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, no, it's a little earlier than 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 wanted to do 10.

You had like something that was about like yay big. That's right. Yeah, arm span to, it attempt that. You had something that was about like yay big. That's right. Yeah. Armspan 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. They involve. 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 object's already apart.

And that number, that ratio, is a constant. Yeah. It's not 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. 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. 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 to minus 21.

So that's the first problem you have. The second problem you have is you've 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 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 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, 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. 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 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 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 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 just about the work and it's fun. I enjoy it. And you fully expect, though, that there will be glory at the end not the glory. I'm not going for the glory. It's actually 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. 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.

The fact is he showed people that it was possible. You could have sources besides the one that everybody knew about. Supernova. Which was supernova, yeah. So when a star explodes, it can wobble space-time, which we now think is probably the hardest thing to go for. It's a very hard source to do. Which we now think is probably the hardest thing to go for. It's a very hard question.

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 money. They're 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? It is the same phenomenon, is it not, as a theoretical localized artificial space-time distortion or warp? Thank you very much. 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 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. 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, you know, an antenna on a transmitter blowing its waves out into space. 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 acts 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,

you know, the 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 increase 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. 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 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. 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 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. I mean, that piece of paper that says that's where he did his calculation. Yeah, he didn't believe black holes were real. Well, the other thing is black holes were not even 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? 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. John is driving 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 Notgonitalia, 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 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, a very big thing. Oh, I'm sorry to shorten that question, but we have to wrap this part up, this segment. 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, Jana Levin. In the studio with me, we have my comedic co-host, Matt Kirshen.

Hey, Jana. 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? 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.

We didn't have any. 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. 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, and then all of a sudden they hit each other and they make a new black hole. That's what they do. When you do this, 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. 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 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. It requires 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? 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, Janet. It could be that, and people are thinking that. And some people even, let me now go on. Let's decay into a very technical conversation. This gets into something really quite tricky, but let me say that's what- What about the metallicity of this? No, no, no, no, no, no. Come on, let's get away from that. That was about to be my question.

I mean, your question. You were going to ask that, right? Yeah, I was going to ask that. Okay, well, to hell with the metallicity for a moment. 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.

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. And that would be low frequencies. 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. When I'm building my own LIGO at home,

what kind of scale should I aim for? Do you know that actually happened to me? I went to the LIGO lab. I am 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 months. 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 are 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. That's the most likely explanation,

but there are others too. 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 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.

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. I just left it like it was. It was a run. 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. The RF, if it's a problem, well, it can't kill us. 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. So you checked.

And so you asked, what did I think? Yeah, you check the log. You wake up 8 a.m. in May. Well, I'll tell you what happened. That was really cute. I went to the log. We were on vacation. My wife and son were with me 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're 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 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. Yeah. 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 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.

Alright, 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. You could have a compression while the other one is a rarefaction.

Like water. It's not impossible, but my God, in the real world, it's not going to happen. 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? Well, if that collision happened in our solar system, we would be, we might not even be here.

I'll tell you what happens. We would get... 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. 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 the gate you can recast Gravitation as yeah, Steve Weinberg did for exactly 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 II 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? 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 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. It's been a pleasure to talk to you. Matt, so great to have you on. Check out Probably Science at Matt Kirshen 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. This is StarTalk All-Stars. Thanks for listening. See you in the multiverse. This is StarTalk.