When Black Holes Collide with Nergis Mavalvala

Summary

StarTalk Radio Episode Summary: "When Black Holes Collide with Nergis Mavalvala"

Release Date: April 1, 2025

In this captivating episode of StarTalk Radio, astrophysicist Neil deGrasse Tyson hosts comedian Harrison Greenbaum alongside esteemed quantum astrophysicist Nergis Mavalvala. The discussion delves deep into the enigmatic world of gravitational waves, black hole collisions, and the intricate interplay between quantum mechanics and astrophysics. Below is a detailed summary capturing the essence of their enlightening conversation.

---

1. Introduction to Nergis Mavalvala

The episode kicks off with Harrison Greenbaum welcoming Nergis Mavalvala back to StarTalk, highlighting her role as a leading quantum astrophysicist and her position as the dean of the MIT School of Science.

• Harrison Greenbaum [01:43]: "I'm excited. I know this is not your first rodeo with us."

---

2. Understanding Gravitational Waves

Nergis provides a foundational understanding of gravitational waves, explaining their nature and significance in astrophysics.

• Nergis Mavalvala [07:16]: "Space isn't empty. Space... can curve, it can ripple, it can tear. And so that's really the wavy part of space-time."

She elaborates on how massive objects like black holes and neutron stars generate these ripples in the fabric of space-time, emphasizing that ordinary stars like our sun produce negligible gravitational waves, making the detection of waves from more massive objects essential.

---

3. The Physics Behind Gravitational Waves

Harrison probes deeper into the mechanics of gravitational waves, using vivid analogies to elucidate complex concepts.

• Nergis Mavalvala [09:05]: "Hawking radiation comes about from the quantum mechanical properties of black holes."

She introduces Hawking radiation, describing it as a mechanism where black holes emit radiation due to quantum effects, indirectly "slimming down" the black holes over time.

---

4. History of Gravitational Wave Detection

The conversation transitions to the historical attempts to detect gravitational waves, acknowledging early efforts and the eventual success of the LIGO project.

• Harrison Greenbaum [23:30]: "What intrigues me here is at the time... was a completely different method, correct?"

Nergis recounts Joe Weber's initial attempts with bar detectors and the subsequent challenges in replicating his results, underscoring the importance of verification in scientific endeavors.

---

5. The LIGO Project and Its Achievements

Nergis details the inception and operational mechanics of LIGO, highlighting its sophisticated interferometer setup designed to detect minute distortions caused by gravitational waves.

• Nergis Mavalvala [38:57]: "We're not breaking the laws of physics. No, no."

She explains the concept of quantum squeezing, a technique employed by LIGO to surpass quantum limitations, allowing for the precise measurement of gravitational waves without violating quantum principles.

---

6. Quantum Mechanics and Measurement Challenges

A significant portion of the discussion focuses on the challenges posed by quantum mechanics in measuring gravitational waves and how LIGO ingeniously overcomes these hurdles.

• Nergis Mavalvala [37:58]: "Exactly, With perfect knowledge."

She delves into the Heisenberg Uncertainty Principle, elaborating on how LIGO manipulates uncertainties in different wave properties to achieve the desired measurement precision.

---

7. Future Prospects and Unanswered Questions

Nergis shares her vision for the future of gravitational wave astronomy, touching upon the mysteries that still abound, such as the formation of exceptionally massive black holes.

• Nergis Mavalvala [46:55]: "We've seen black holes that are around 100 solar masses. We don't know how nature forms those because if they're formed in the same way as black holes that are 20 or 30 solar masses are formed, stars don't do that."

This revelation points to gaps in our understanding of stellar evolution and black hole formation, hinting at potential new physics waiting to be discovered.

---

8. The Importance of Verification in Science

Emphasizing the scientific method, Nergis discusses the critical role of reproducibility in validating experimental results.

• Harrison Greenbaum [27:25]: "If nobody can match the result, it's time to move on."

She reflects on the lessons learned from Weber's unverified claims, reinforcing the necessity for multiple experiments and independent confirmations in establishing scientific truths.

---

9. Cosmic Perspective and the Future of Science

Concluding the episode, Harrison offers a cosmic perspective on scientific discovery, advocating for continuous creativity and exploration to unveil the universe's deepest secrets.

• Harrison Greenbaum [50:10]: "This interconnectivity, this interdependence of cosmic discovery on these multiple frontiers is how science works."

Nergis echoes this sentiment, expressing optimism about future discoveries that will bridge existing gaps in our knowledge and propel astrophysics into new realms.

---

Notable Quotes

• Nergis Mavalvala [07:49]: "Space isn't empty. Space doesn't do nothing. It actually has many, many dynamical properties."

• Harrison Greenbaum [27:46]: "If nobody can match the result, it's time to move on."

• Nergis Mavalvala [38:36]: "We're not breaking the laws of physics. No, no."

• Harrison Greenbaum [50:10]: "This interconnectivity, this interdependence of cosmic discovery on these multiple frontiers is how science works."

---

Conclusion

This episode of StarTalk Radio masterfully intertwines complex scientific concepts with engaging dialogue, making the intricate world of gravitational waves accessible to a broad audience. Nergis Mavalvala's insights shed light on both the triumphs and challenges of modern astrophysics, while Harrison Greenbaum's comedic flair ensures the conversation remains lively and relatable. Together, they underscore the perpetual quest for knowledge that drives scientific discovery forward.

Transcript

[Neil DeGrasse Tyson]

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[Harrison Greenbaum]

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[Harrison Greenbaum]

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[Neil DeGrasse Tyson]

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[Harrison Greenbaum]

So, Harrison, I'm finally getting to the bottom of these gravitational waves.

[Nergis Mavalvala]

I brought my gravitational surfboard. I'm ready.

[Harrison Greenbaum]

I don't know if you can do that. Maybe.

[Nergis Mavalvala]

I'm gonna try. I can barely surf in real life.

[Harrison Greenbaum]

Yeah. So gravitational waves, black hole collisions, the big bang.

[Nergis Mavalvala]

Sounds like big things.

[Harrison Greenbaum]

With one of the world's experts on these very subjects.

[Nergis Mavalvala]

So exciting.

[Harrison Greenbaum]

A quantum astrophysicist in a few moments on StarTalk. Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now. This is StarTalk. Neil DeGrasse Tyson, your personal astrophysicist. I got with me, Harrison Greenbound. Harrison, how you doing, man?

[Nergis Mavalvala]

I'm good. Thanks for having me back.

[Harrison Greenbaum]

I'm excited. I know this is not your first rodeo with us. All right, you know what we're gonna talk about today?

[Nergis Mavalvala]

Space stars.

[Harrison Greenbaum]

Okay. Gravitational waves.

[Nergis Mavalvala]

Yeah, no, I know about them. Separately.

[Harrison Greenbaum]

Oh. Gravity and waves, but not gravitational waves. I will totally hook you up on that.

[Nergis Mavalvala]

All right, great.

[Harrison Greenbaum]

So, Harrison, you're a comedian and I just learned you have an off Broadway show.

[Nergis Mavalvala]

Yeah, it's called Harrison Greenbound, coincidentally.

[Harrison Greenbaum]

Oh, really? I wonder why.

[Nergis Mavalvala]

Yeah, exactly.

[Harrison Greenbaum]

It's a Harrison Green Bound.

[Nergis Mavalvala]

What just happened?

[Harrison Greenbaum]

What just happened?

[Nergis Mavalvala]

It's on stage and it's a comedy and magic show. I've been working on it for.

[Harrison Greenbaum]

I forgot you do magic.

[Nergis Mavalvala]

Yeah, yeah, yeah, yeah.

[Harrison Greenbaum]

Oh, my gosh. That is so geeky.

[Nergis Mavalvala]

Oh, yeah. I went to magic camp and space camp, so I've really.

[Harrison Greenbaum]

She had no dates. Going through your entire career at school?

[Nergis Mavalvala]

Yeah, my parents wanted breaks for me one week at a time, so Our.

[Harrison Greenbaum]

Guest today has a different expertise from you.

[Nergis Mavalvala]

Really?

[Harrison Greenbaum]

We have Nergis Mavalvala. Did I say that correctly?

[Nergis Mavalvala]

Yes.

[Harrison Greenbaum]

Excellent. And this is your second time on StarTalk?

[Nergis Mavalvala]

It is.

[Harrison Greenbaum]

You were last on StarTalk nine years ago.

[Nergis Mavalvala]

I'm hardly nine years old. Don't.

[Harrison Greenbaum]

At one of our live performances, Star Talk Live in Account Basie Theater in New Jersey. We occasionally take the show on the road, but regionally.

[Nergis Mavalvala]

Nice.

[Harrison Greenbaum]

Yeah. And that was back when our first results from gravitational waves came across.

[Nergis Mavalvala]

Yeah. Shortly after the first discoveries.

[Harrison Greenbaum]

Yeah. Very, very cool. Well, you are a quantum astrophysicist. That is the baddest asses thing you could ever put on a business card.

[Nergis Mavalvala]

I feel like quantum is very small and astrophysicist is very big.

[Harrison Greenbaum]

That is another reason you were a professor at mit. Which department did they put you in?

[Nergis Mavalvala]

Physics.

[Harrison Greenbaum]

Physics Department. That makes sense, doesn't it?

[Nergis Mavalvala]

It would be weird if she was just teaching English.

[Harrison Greenbaum]

And I'm sorry to learn you're also dean of the School of Science. Sorry to hear that.

[Nergis Mavalvala]

Yes.

[Harrison Greenbaum]

Yeah.

[Nergis Mavalvala]

Can you get people in trouble?

I can, but mostly I get myself in trouble.

Do you cheat on your own test? I have the answer key. It's not fair.

[Harrison Greenbaum]

So, Dean of the MIT School of Science. I say I'm sorry to hear that because that takes time away from, like, your studies, doesn't it? But they pay you more.

[Nergis Mavalvala]

They do, yeah. Yeah, they do. And the other thing that comes with being dean is you actually get some administrative help. And as a result, I actually have a little bit more time to be in the lab than when I'm just being professor and running around doing too.

[Harrison Greenbaum]

Many things, trying to get things done. Now you get peeps. You got peeps.

[Nergis Mavalvala]

Now I got really, really talented peeps.

[Harrison Greenbaum]

Okay. All right. That's how that should work. You are on the LIGO team. Let's test. Harrison. Harrison. It's an acronym. What does LIGO stand for?

[Nergis Mavalvala]

Lord, I got options.

Is.

That works.

[Harrison Greenbaum]

Nergis. I think that should be the new meaning of the. Of the acronym ligo.

[Nergis Mavalvala]

You know, there's a lot of changes coming to NSF proposals. That could be one of them.

[Harrison Greenbaum]

Lord, I got options. Laser interferometer. Gravitational Wave Observatory. Did I get that correct?

[Nergis Mavalvala]

You did. You did.

[Harrison Greenbaum]

Very good. And you're on the team that discovered these. So I understand they took a bunch of people to Stockholm for the Nobel Prize. Were you on that plane?

[Nergis Mavalvala]

Yes.

[Harrison Greenbaum]

Excellent. She got all dressed up and everything.

[Nergis Mavalvala]

Kind of. Yeah. Yeah. That's not my thing. Right.

[Harrison Greenbaum]

Kind of. What outfit Would you have for some other occasion if not for the Nobel Prize?

[Nergis Mavalvala]

You know, I'm not a dress up type, and so. And I'm not a girly type. So I had to also decide, am I gonna wear, like, girly clothes or a tux?

[Harrison Greenbaum]

Oh, you fell into a haberdasher gap.

[Nergis Mavalvala]

Yes. A sartorial dilemma.

[Harrison Greenbaum]

Okay, interesting.

[Nergis Mavalvala]

So what did you end up doing? Just shorts. I feel like that's the answer. King of Sweden was cool with that.

[Harrison Greenbaum]

No. So I'm delighted that you got to see that. By the way. We just had on Startalk. I hung out with Kip Thorne, the man himself, and we visited him at his home and we had a whole interview. It was largely about, you know, he was one of the executive producers on the film Interstellar. And it just had its 10th anniversary and it was a re release just in celebration of that fact because it had so many people talking about gravity, physics, and relativity and all the rest of that. So anything out there that sort of ratchets up people's fluency in physics, I'm all for it. Even if they didn't understand what the hell they were looking at.

[Nergis Mavalvala]

Right. I was like, Matthew McConaughey. I think he's aging. I'm not sure. I think with the daughter.

[Harrison Greenbaum]

Yeah, the daughter and the thing. Yeah. So that we covered that. But let's get back to gravitational waves. You reminded me. I'd forgotten that when we were on stage, we actually did a gravitational wave together.

[Nergis Mavalvala]

The gravitational wave dance. Dance, yes.

[Harrison Greenbaum]

Yeah. I don't know if we have footage of that, but I hope not.

[Nergis Mavalvala]

Me too.

I'm trying to picture it.

[Harrison Greenbaum]

So, Nirgis, remind everybody we've heard the term gravitational waves or ripples in space time. That's surely accurate, but I don't know that it helps. So how can you dig into that and unpack what's going on?

[Nergis Mavalvala]

Yeah, so I think one of the ways we can think about that is it's very tempting to look out into space and think of empty space as a number of things that are just not true. Space isn't empty. Space doesn't do nothing. It actually has many, many dynamical properties. Things that, like, it can curve, it can ripple, it can tear. And so that's really the wavy part of space time. And the idea is that when we have objects that are massive, so they should have gravity. And if they just.

[Harrison Greenbaum]

When you say massive, you don't mean a brick or a stone. You're talking about black holes.

[Nergis Mavalvala]

Well, you know, bricks and stones would do the same thing, except it would be just a much, much smaller effect.

[Harrison Greenbaum]

And harder to measure.

[Nergis Mavalvala]

Way, way harder to measure.

[Harrison Greenbaum]

So our threshold is for what? I mean, our measurement threshold today.

[Nergis Mavalvala]

Our measurement thresholds today are not even ordinary stars like our own sun couldn't measure that. No. So if we're looking for waves from these kinds of objects, they're more things like neutron stars and black holes.

[Harrison Greenbaum]

So dense objects in the universe. Dense objects where gravity is saying something.

[Nergis Mavalvala]

Yeah. So objects that have so much gravity packed into a small volume that really, the space around those objects is very bent.

[Harrison Greenbaum]

Okay.

[Nergis Mavalvala]

Have those objects tried Ozempic?

[Harrison Greenbaum]

Oh, oh, oh. How do we end up doing a commercial for a pharmaceutical company? And we're not getting paid for helping.

[Nergis Mavalvala]

The black holes slim down a little bit. They're very dense. They're causing waves and gravity.

[Harrison Greenbaum]

That's actually.

[Nergis Mavalvala]

We don't want them to slim down for their work.

[Harrison Greenbaum]

But actually, isn't Hawking radiation a kind of ozempic for black holes?

[Nergis Mavalvala]

Yeah, it'll help them evaporate.

[Harrison Greenbaum]

Yeah. So we got a little mechanism. Tell everybody about Hawking radiation.

[Nergis Mavalvala]

So Hawking radiation comes about from the quantum mechanical properties of black holes. So the idea is that in quantum mechanics, we have a phenomenon where particles and antiparticles can be formed out of photons, and then they can crash together and become photons again. And Hawking radiation.

[Harrison Greenbaum]

So it's energy to matter. Matter back to energy. E MC squared would prescribe. How much of that is happening in any moment?

[Nergis Mavalvala]

Right.

[Harrison Greenbaum]

And Hawking radiation on one side, M on the other side. So we. Good.

[Nergis Mavalvala]

And then C is speed of light.

[Harrison Greenbaum]

Speed of light. Square.

[Nergis Mavalvala]

Yeah.

[Harrison Greenbaum]

Square.

[Nergis Mavalvala]

Yeah.

[Harrison Greenbaum]

Okay.

[Nergis Mavalvala]

And so this is a phenomenon by which, as you create these particles, some of that energy can get radiated away. Where does that energy come from? It comes from the properties of the gravitational properties of the black hole. What happens?

[Harrison Greenbaum]

So you're stealing gravity matter out of the black hole and thereby taking away some of its gravity.

[Nergis Mavalvala]

Yes.

[Harrison Greenbaum]

Okay. And it just does that. And so it's a very slow version of Ozempic for black holes. That's what started this.

[Nergis Mavalvala]

Very, very nice.

[Harrison Greenbaum]

I just wanted to finish it there. Right, okay.

[Nergis Mavalvala]

Yeah.

[Harrison Greenbaum]

All right. So, Nergis, can I take you back to when I was 14? All right. I came to the Hayden Planetarium. Here's my office here. I became director of the planetarium. I came here as a kid.

[Nergis Mavalvala]

Not at 14.

[Harrison Greenbaum]

No, no, no, no. Ultimately, I became director. So I came here and I. Beyond the space show that I watched at the time, they would have programs at night, which we still do, and speakers would come in and give lectures on modern astrophysics. So I would come in for that. And one of them was on black holes. That's when I first learned that gravity moves at the speed of light.

[Nergis Mavalvala]

Okay, you knew that when you were 14? I didn't learn that till I was much older.

[Harrison Greenbaum]

That's when I learned it. That's when I learned it.

[Nergis Mavalvala]

15.

[Harrison Greenbaum]

And then I thought about it and I said, if gravity travels at the speed of light, then how does gravity get out of a black hole? And the answer was a little fishy to me. They said, well, there's a gravitational field that's always there. And it's a change in the gravitational field that moves at the speed of light. And I don't know if that's accurate, but that's what the dude told me. And otherwise, he couldn't get gravity out of a black hole. Where the black hole doesn't let anything get out, even the speed of light. And if the gravity moves at the speed of light, how's the gravity gonna get out of a black hole?

[Nergis Mavalvala]

I just don't think of it that way. I think about gravity as the geometry of space time. And the black hole is part of that geometry. And the things that we can know about, and this is true for light as well, are only things that are outside the horizon of the black hole. So what I've always been taught, and I think I learned this, maybe even from Kip Thorne, was that it's not meaningful to think about what happens inside the horizon. Because we don't even know if our laws of physics would hold there or not. And so when I think about gravity traveling at the speed of light, what's actually traveling at the speed of light is a gravitational wave. And it's only really meaningful outside of the horizon.

[Harrison Greenbaum]

She dodged that one.

[Nergis Mavalvala]

Yeah, we can't know what's in there, so who cares?

[Harrison Greenbaum]

She totally dodged that. No, no, that's good. That's good. It's an important distinction that physics had to mature into as a field to realize there are things that are beyond your knowledge. And therefore there's nothing you can say.

[Nergis Mavalvala]

About it right at all for now. You know, who knows what other forces we might discover that would describe something inside that horizon?

[Harrison Greenbaum]

Okay, but right now that's not happening.

[Nergis Mavalvala]

Right?

[Harrison Greenbaum]

Okay. So. But a change in gravity would then be a ripple, a change in that sort of thing that I'm feeling out there. And we can just watch that at the speed of light. Cause we'd say if we pluck the sun from the center of our solar system, you wouldn't know about it for 8 minutes and 20 seconds. You'd still orbit, we'd still feel the heat, we still feel the gravity. Everything would be normal. And eight minutes, 20 seconds later we fly off at a tangent in the dark and freeze in interstellar space. Have a nice day. Yes. How does it happen?

[Nergis Mavalvala]

Those eight minutes before are amazing.

[Neil DeGrasse Tyson]

Brought to you by who Larious Stand Up Comedy now on Hulu. Hey everybody, Hulu has a bunch of new stand up specials that are not just funny, they're hoolarious. Very funny Hulu. Anyway, they're launching new exclusive stand up specials from awesome comedians like Jim Gavigan, Ilana glaser, Roy Wood Jr. Bill Burr and tons more. A new special drops every month and they've got a huge library of stand up specials to check out. Go to Hulu and get your stand up fix now.

[Alexander Harvey]

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[Harrison Greenbaum]

Did Einstein? I don't know that I've seen the paper that did this. Did he predict gravitational waves?

[Nergis Mavalvala]

Yeah. So Einstein, when he was developing the theory of general relativity, and this was the theory of gravity. So the thing that, so we all learn in school, Newton's version of gravity, and Newton's law has been it's easy to understand, it's intuitive. It Sundays, you have two objects that have mass and they're going to feel a force of attraction between them. And it was quite quantitative. He said the force of attraction will be proportional to their masses and inversely proportional to the square of the distance separating them.

[Harrison Greenbaum]

It's very clean. That's a clean operation.

[Nergis Mavalvala]

You know, we teach it in very early, sort of first encounters with physics, and it was quite successful. It told us about how orbits would work. And it also had pretty early on places where it didn't work perfectly. Now, what Einstein, when he was formulating thinking about gravity, he kind of turned it on its head and he said, well, look, gravity is not really a force. Gravity is the geometry of space time. Big words. But he had a series of papers, two or three, from 1915 to 1918, in which he sort of formulated this theory of general relativity. He wrote down what are now known as Einstein's equations. They look not that much worse than, say, Newton's law, except they're quite beastly. They're very difficult to solve. But part of that work was that he did ask the question, what happens if whatever object you're thinking of isn't just sitting still in space? What happens if it's moving and not just moving at constant, constant velocity? What happens if it's accelerating? And then out of his equations popped this wave like object which he called gravitational waves. And the other.

[Harrison Greenbaum]

I want stuff like that to pop out of my equations. Do you have equations where stuff pops out?

[Nergis Mavalvala]

No.

Me neither.

I'm still stuck on the wave part. Was he gravitational surfing?

I have a lot of analogies to that. Because if you wanted to try and visualize what would this look like? One way that you could is you could think of space time as the surface of a still pond. And you drop a big rock in the middle and there's a wave that travels, a ripple that travels on the surface. It travels outwards from where you drop the rock. And if you were a little teeny tiny ant on a surfboard, you would surf that wave. Right.

[Harrison Greenbaum]

And the wavelength. So the distance between the crests.

[Nergis Mavalvala]

Right.

[Harrison Greenbaum]

Would be related to how big was the rock that you dropped in.

[Nergis Mavalvala]

Right.

[Harrison Greenbaum]

Okay. So when you measure gravitational waves with LIGO or whatever other tools available to you you try to measure the wavelength of that so that you can infer what created that wave. Because you don't. Otherwise you didn't see the thing happen.

[Nergis Mavalvala]

No, exactly. Right. So we measure a number of things. We measure the wavelength, which is the spacing between the peaks in successive peaks. We also measure the amplitude, which is how big, what was the height of the wave. And those both of those things are changing with time, depending on what the source is. So by measuring sort of the shape.

[Harrison Greenbaum]

Of the wave as you go into it and as you come out of.

[Nergis Mavalvala]

It, as it passes by you, as.

[Harrison Greenbaum]

It washes over the earth.

[Nergis Mavalvala]

Exactly. And as you do that, you can tell many. You can infer some of the properties of the system that emitted that wave. Sort of like if you just saw the ripple at the edge of the pond and you have to kind of measure the frequency of the wave, you have to measure the amplitude of the wave. You have to know something about the density or the viscosity of the water of the pond from that, because the.

[Harrison Greenbaum]

Medium, it would come through differently.

[Nergis Mavalvala]

Right. And once you have put those things together without ever seeing the rock fall in the center of the pond, you can say something about the rock. And that's kind of what we're trying to do.

[Harrison Greenbaum]

So that's very impressive because you get this measurement and then out in the research papers, these are two black holes of 30 times the mass of the sun colliding a billion light years away. I mean, that's badass to make that kind of statement.

[Nergis Mavalvala]

It is. I think that the properties of the black holes are almost. I can't think of too many things that are more badass than that.

[Harrison Greenbaum]

I agree.

[Nergis Mavalvala]

I have to tell you why. I mean, so, you know, one of the first gravitational wave that we measured with LIGO were from these 30 solar mass black holes. And you know what these monsters were doing at the time that they collided? They were moving at half the speed of light.

[Harrison Greenbaum]

Whoa.

[Nergis Mavalvala]

Okay, just. You are speechless.

I'm trying to picture it. I don't know if I can actually picture what that I'm picturing a Godzilla movie. It's like a black hole with like little arms. Start with Godzilla and they're both fighting each other. But instead of the city, it's. That's where my brain is going.

And instead of, you know, moving at sort of human or, you know, Godzilla speeds, they are moving at the speed of light. The amount of energy it takes to accelerate a little electron in our sort of, you know, experiments to the speed of light and to Think we do it with something that's 30 times the mass of our sun.

[Harrison Greenbaum]

So there's no greater particle accelerator than the universe itself.

[Nergis Mavalvala]

Indeed.

[Neil DeGrasse Tyson]

Ooh, ooh.

[Nergis Mavalvala]

Is it making a sound when it happens?

No. And the reason is that.

[Harrison Greenbaum]

But wait a minute. You guys put a soundtrack to that.

[Nergis Mavalvala]

Wave that's different than whether it made the sound.

[Harrison Greenbaum]

Well, then get us out of that little. That media ploy. Because I always have to undo things that the media does or give context for it. Because people say, well, if space is a vacuum, and because they knew that sound doesn't help in space, no one.

[Nergis Mavalvala]

Can hear you scream.

[Harrison Greenbaum]

Exactly. That's a legit call. Right. For the movie Alien. Alien. So did you endorse this attachment of sound to it? How did you, as an educator and as a physicist? Where were you on that?

[Nergis Mavalvala]

Yeah. So, you know, I think of it as. There are many, many phenomena, as scientists or as humans and observers that we can't directly observe. Let's take light. So we love to look at pictures of even astronomical objects where they're emitting X rays. We can't see X rays, so we color it blue, and we can see blue, and then the object looks blue, and we imagine that's an X ray. And so when I think about sound or the sound of these waves, it's an encoding. It's a way of mapping it onto senses that we do have. Right. So that's how you know.

[Harrison Greenbaum]

Because otherwise, that's fair enough.

[Nergis Mavalvala]

You know. So, I mean, think about the way that we visualize a cell. We can't just look at a blob of stuff and say that, you know, that is the cell. We've used microscopes, we've used ways of observing, and then we put together pictures.

[Harrison Greenbaum]

We've enhanced our feeble senses.

[Nergis Mavalvala]

Exactly.

[Harrison Greenbaum]

To gain access to the universe that would otherwise lay forever invisible in plain sight.

[Nergis Mavalvala]

But it's dangerous, because if you pick the wrong sound, then nobody cares. Like if you make a video of two black holes colliding and it goes boing, boing. Yeah, Ex. You gotta pick the right sound. Something out of a Ruga.

[Harrison Greenbaum]

Out of a Tom and Jerry cartoon.

[Nergis Mavalvala]

Exactly.

[Harrison Greenbaum]

Aruga.

[Nergis Mavalvala]

Doesn'T work.

[Harrison Greenbaum]

So with ligo, all's well, then ends well. But it didn't begin smoothly. I remember there were physicists called to Congress to defend the budget outlay to the National Science foundation that was gonna take huge chunks of money to pay for your laser toy.

[Nergis Mavalvala]

How did you convince them you weren't building a death Star?

Yeah. So a couple of things it is certainly part of the history of LIGO that. So what I know of the history is that Rai Weiss and Kip Thorne, two of the founders of ligo, Raw Wise, was an experimentalist thinking about how you might measure gravitational waves.

[Harrison Greenbaum]

And he shared the Nobel Prize, right.

[Nergis Mavalvala]

And they shared the Nobel Prize. And Kip Thorne was thinking about the astrophysics. What would gravitational waves look like if two neutron stars or black holes collided and they met somewhat accidentally in 1975? The story goes that they, they had to share a hotel room because one of their bookings got messed up. And then they were up all night conjuring up how one would make this measurement. And that's where the concept of this four kilometer long detector, two and a half mile long detector, ligo, was born.

[Harrison Greenbaum]

What intrigues me here is at the time, because I remember, because I'm that old, there was someone at the University of Maryland, Joe Weber, who was building a gravitational wave detector. And it was a cylinder of aluminum with very highly sensitive servos, if that's the word, that monitored the position of this slab of aluminum. And if a gravitational wave washed over it, it would jiggle it in such a way that he would then measure it by way of these servos. So this method, conjured in the wee hours of the morning in a hotel room, is a completely different method, correct? It may be. There's no way you could have detected it with a slab, a cylindrical slab of aluminum.

[Nergis Mavalvala]

I think now in hindsight we can say that would have been quite. We haven't done that yet. Right, yes. Ok. So it is true that Joe Weber at the University of Maryland had this big slab of metal and it was instrumented with sensors that would see this big slab of metal ringing, just like if you hit a wine glass and it sort of rings a tone. So it would ring because of the gravitational wave that went through it. Now, it turned out that Weber's claim, people. So when Weber made the claim, a lot of people started to build similar instruments and to try to reproduce the measurements, and they couldn't. And eventually people just didn't believe it.

[Harrison Greenbaum]

If I remember correctly, he had a paper saying he had a measurement.

[Nergis Mavalvala]

He had a measurement. And if I recall correctly, the claim was we have a measurement. And not only do we have a measurement, but it seems like the wave is coming from the center of our galaxy, which was sort of seen as a preferred location for some gravitationally heavy object like a black hole, but people just couldn't reproduce it. But what it did do is it really sparked interest in the topic. And so a large number of people started to build these and they wanted to.

[Harrison Greenbaum]

So not all null results are bad if they stimulate interest, is the lesson there.

[Nergis Mavalvala]

I think that's right. And even in Weber's case, though, eventually it turned out to be incorrect claims. He invented some techniques that even to this day we still use.

[Harrison Greenbaum]

Okay, you mentioned something very important about science. One researcher's result does not make the truth. You need verification because anything could have. They could be biased. The current could have fluctuated. Anything could have happened in one case. But if you have 2, 3, 4, and if they give the same result, you got something good. If nobody can match the result, it's time to move on.

[Nergis Mavalvala]

That's right. And in Weber's case, I think it was even more interesting because he had two of these bar detectors. And it was only when people built third, fourth, fifth, and they were built with slightly different technologies and perhaps even with slightly different expectations that it was understood that no one was reproducing what Webber was saying.

[Harrison Greenbaum]

So now in ligo, when you made your grand announcement, two black holes colliding. Why should we believe you? Because. Is there another LIGO to check what you did?

[Nergis Mavalvala]

Yes.

[Harrison Greenbaum]

Oh, well, there it is.

[Nergis Mavalvala]

How many of these lasers are there?

[Harrison Greenbaum]

Okay. Yes, there is. Next. We're down there. Nice. No, there was foresight there, of course. The LIGO facility I visited was in Louisiana, outside of New Orleans. But you would have a whole other one. If that one LIGO facility makes a detection, you would presume and expect another LIGO to make the detection as well.

[Nergis Mavalvala]

Correct.

[Harrison Greenbaum]

Not necessarily in the same moment, separated by.

[Nergis Mavalvala]

Almost certainly not in the same moment, because there's another LIGO facility in Washington state east of Seattle. And you can think about sort of. If you think about a wave that's coming through the earth, a gravitational wave does that. If a gravitational wave is emitted by some distant source, light is actually quite difficult for astronomers because light coming to us interacts with everything in between. Gravitational waves just pass through most things.

[Harrison Greenbaum]

Oh.

[Nergis Mavalvala]

So they are quite useful.

[Harrison Greenbaum]

You have a pure expression of what happened at its source.

[Nergis Mavalvala]

Yes, but it's a double edged sword because by the same token, it doesn't interact very strongly with our detector either. So it's really pretty darn good.

[Harrison Greenbaum]

Be careful what you wish for. Right, right.

[Nergis Mavalvala]

This gravitational wave sounds rude.

[Harrison Greenbaum]

So the one in Washington. It's Hanford, I think. Is that the one?

[Nergis Mavalvala]

Yes, in Hanford, Washington.

[Harrison Greenbaum]

Washington. Which I think used to be a place where they purified plutonium. Plutonium, yeah, yeah.

[Nergis Mavalvala]

Yeah.

[Harrison Greenbaum]

So are you giving emotions to the gravitational wave? You declare it. It's rude. Yeah.

[Nergis Mavalvala]

The gravitational wave just walks through the party, says hi to nobody.

[Harrison Greenbaum]

Nobody.

[Nergis Mavalvala]

Yes. You know that. That is one of. So if you ask, one of the things that we haven't observed with gravitational waves is gravitational waves from the very early universe, say, right after the Big Bang. And when we think about what we know about the Big Bang.

[Harrison Greenbaum]

But just to be clear, you haven't observed them because you don't have the capacity to do so yet, not because.

[Nergis Mavalvala]

Our instrumentation just isn't sensitive enough.

[Harrison Greenbaum]

Okay.

[Nergis Mavalvala]

Yeah. So if you think about what we know about the Big Bang, what we know comes from light. Now, the light that we see from the Big Bang, this cosmic microwave background, actually comes to us from 400,000 years after the Big Bang. Now, what happened before that? We can't tell because the universe was so hot and dense at the time that the light couldn't escape. Now, what does that mean? It's exactly what you were saying, Harrison. So the light is like going to a party with an extrovert and you say, honey, I'm ready to leave. And it'll be an hour before you leave the party, because they're going to stop. They're going to say hi to people on the way to saying bye to people.

[Harrison Greenbaum]

Top off their drink.

[Nergis Mavalvala]

Exactly. They're not coming. Gravitational waves from the early universe have been streaming to us. If we could measure them in the LIGO band, they would be streaming to us from when the universe was 10 to the minus 22 seconds old. And the reason is just what you said. They're like going to the party with the introvert. You say, you know, we're ready to leave and you're lucky if they'll say goodbye to the host.

[Harrison Greenbaum]

Right. So this distinguishes our access to the early universe from what our normal telescopes can bring to us, which is this 400,000 year barrier. Really? And the gravitational waves, which is plow right past that. They don't even care. They don't. They. They're moving right along.

[Nergis Mavalvala]

Right. And so if you want to see the earliest moments of the universe, gravitational waves are your friend.

If we want to make them more sensitive, do we have to live with bigger lasers?

That's a piece of it. But there's lots of other things you got to make better, too.

[Neil DeGrasse Tyson]

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[Harrison Greenbaum]

I'm in conversation with Kip Thorne and I verified because I'd read this and but he's the man. And I said, you have all this apparatus, 4 meter, 4 kilometer long beam that reflects and they recombine. You look at a phase shift and look at a jiggle. And I said, how big is that jiggle? How much did this apparatus move by virtue of this wave passing across? And it is the width of one twentieth the diameter of a proton when.

[Nergis Mavalvala]

It'S cold, when it's nice outside.

No, that's too big.

[Harrison Greenbaum]

Too big. Wait, so, all right, so let's just speak more broadly. A fraction the diameter of a nucleon of an atom. Okay.

[Nergis Mavalvala]

A thousandth.

[Harrison Greenbaum]

Okay. So you want to make sure nothing else is responsible for what you're about to measure. Otherwise you're measuring the wrong thing. And when I visited they were telling me if somebody's walking down the street a mile away, those vibrations can be detected in. That's exactly how they described it. But they see all vibrations, so they have to isolate the experiment from anything that could be happening from the outside. Okay, so then you isolate it and then you put it in a vacuum so that air particles are not bumping into it. So now it's there, but then it is at a temperature, it's not at absolute zero. So at any temperature, everything is vibrating. And even if you tamp that down, there's always a quantum uncertainty about the position of a particle. Heisenberg told us this. Okay, so if you want to know exactly what a particle is doing, there's an uncertainty to that. So how are you making measurements that are smaller than the quantum uncertainty allows? And we had this conversation and Kip Thorne said, well, we did. Blah, blah, blah, and we did this. And in that way we cheated the quantum laws. And I said, no, no, then it's not a law if it bends at your will. So what was he talking about?

[Nergis Mavalvala]

Yeah, we do that.

Dump the fact down.

[Harrison Greenbaum]

Not an answer. Just like Invasion of the Body Snatchers. Yes, he's one of us, I think.

[Nergis Mavalvala]

One of us. One of us.

[Harrison Greenbaum]

We both can bend the rules of quantum physics. So, okay, for those of you who have such powers, please explain to me, like in as plain as English as you can.

[Nergis Mavalvala]

Yeah, so I can try to do that. So what quantum mechanics tells us is that if you measure two particular properties of a particle, and one example would be the energy of. Let's talk about photons. Because it turns out in ligo, at the moment we're limited by the quantum mechanics of the light. The quantum mechanics of the mirror isn't yet a problem because the mirrors are still moving more than their quantum properties would allow. Okay, so let's. Let's talk about the light. So the quantization of the light says the light has two properties. Light's made up of photons. And if I want to make a measurement of that, I want to know two things about it. What was the energy of the photons that I'm measuring and when did they arrive on my detector? And you can't know those two things at the same time. With intuitive precision.

[Harrison Greenbaum]

With perfect.

[Nergis Mavalvala]

Exactly. With perfect knowledge. But you can know one of those properties very, very well if you allow the other one to be very unknown that quantum mechanics allows you to do. That's the trick we play. So if we are interested, as we are, in our measurement, measuring the phase of the light Wave, the phase would.

[Harrison Greenbaum]

Be because you have two light beams.

[Nergis Mavalvala]

Right.

[Harrison Greenbaum]

And you have to see how they match up.

[Nergis Mavalvala]

That's right.

[Harrison Greenbaum]

Because if they match up perfectly, nothing happened to one relative to the other. But if a wave washes over, then one jiggles a little differently and the waves don't match up. You'll see the. Okay, so that's exactly right.

[Nergis Mavalvala]

So say if you're interested in measuring the phase, then what you can do is you can create light with properties where you let the amplitude or the energy of the wave be very unknown. But you've graded that off for precision in the phase. And we have learned how to make instruments that can do that.

[Harrison Greenbaum]

Damn.

[Nergis Mavalvala]

So they're instruments that increase uncertainty in one variable.

That's right. And reduce it in the other variable. And that's really important. If you were reducing the quantum uncertainty. Uncertainty in both variables at the same time, you would be violating the laws of physics. But that we are not doing.

[Harrison Greenbaum]

Okay, you're just bending the laws of physics.

[Nergis Mavalvala]

So we're not breaking the laws of physics. No, no.

[Harrison Greenbaum]

It's a fair loophole.

[Nergis Mavalvala]

I like to say.

[Harrison Greenbaum]

This is a quantum loophole. Admit it.

[Nergis Mavalvala]

What? No.

[Harrison Greenbaum]

Oh, she got angry. She got a couple attitude on that.

[Nergis Mavalvala]

Increasing the uncertainty.

I call it manipulating the laws of quantum physics. Because we can't violate them. And loopholes are things that are just usually things you haven't thought of. Whereas this we've thought of. We're deliberately doing this. And so that's the kind of.

[Harrison Greenbaum]

So it's not a problem if you don't know at all what the.

[Nergis Mavalvala]

So there's a price to pay. The price to pay is. Look, if you're interested in measuring the phase, and if by accident, because your measurement apparatus isn't perfect, you start to collect a little bit of information about the amplitude, it won't work for you anymore, because remember, the amplitude is now very, very noisy. So this is what we do. We reduce the noise in the quantity we're most interested in measuring. We stuff it into the quantity we're trying not to measure. And then we try to do that as well as we can.

[Harrison Greenbaum]

Grabbing quantum physics by the horn.

[Nergis Mavalvala]

Yes.

[Harrison Greenbaum]

And making it bend to your will, you know, almost.

[Nergis Mavalvala]

We call it squeezing. We squeeze the light.

[Harrison Greenbaum]

Ooh, let's get the picture of this. Now you have two beams.

[Nergis Mavalvala]

Yeah.

[Harrison Greenbaum]

They're at right angles, I presume.

[Nergis Mavalvala]

Yeah.

[Harrison Greenbaum]

Yes. And the round trip is 8 km, is that right? Yeah. Okay. And so it takes time for the very measured time for the light to do that. This is A single laser beam of light that has been split.

[Nergis Mavalvala]

Correct, it has been split. And not only does it go 4km down and come back, there's an added complication, if you will, which is that in that four kilometer span, we have a pair of mirrors that are facing each other. And just like when you put your own head between two mirrors and you see multiple images, the light is bouncing multiple times between those. It's a way of increasing the path length, if you will. All right, so, and so it bounces in our case, in Ligo's case, about 100 times.

[Harrison Greenbaum]

Okay, so but then it has to come back through to recombine.

[Nergis Mavalvala]

Yes.

[Harrison Greenbaum]

Okay, so you have your magic ways that you. It goes up and back a hundred times, then at some point the light has to come back through and not reflect back.

[Nergis Mavalvala]

Correct.

[Harrison Greenbaum]

And then you compare the waves of.

[Nergis Mavalvala]

The light from the two arms. Yeah.

[Harrison Greenbaum]

So that's the shift. So how much different would one wave have to be from the other to be the gravitational wave? To be the effect of the gravitational wave.

[Nergis Mavalvala]

Yeah. So the way that you can think of it is that the output of our instrument we're measuring, you think of the light as two sine waves, one from each arm. And we arrange the distances such that the two light waves cancel. So the peak of one sits on the trough of the other. And in the ideal case, you would see no light. Zero. Right. And then if one arm is slightly different in, then they don't perfectly cancel. And now some light sort of trickles out.

[Harrison Greenbaum]

Oh, brilliant.

[Nergis Mavalvala]

Right, exactly.

[Harrison Greenbaum]

I should get a Nobel Prize for that.

[Nergis Mavalvala]

They already did.

You're tied with Einstein.

[Harrison Greenbaum]

So it's always better to see a signal where there isn't otherwise a signal than to measure the difference between two large signals.

[Nergis Mavalvala]

Yeah. If you try to measure a tiny difference in a big number, it's fairly hard to measure. But you start with something that's very close to zero.

[Harrison Greenbaum]

Error prone too.

[Nergis Mavalvala]

You start with something that's very close to zero and now you get anything. You got something.

[Harrison Greenbaum]

Wow.

[Nergis Mavalvala]

So that's what we do.

[Harrison Greenbaum]

And how strong is that extra signal compared with the amplitude of the waves to begin with? So what fraction of that amplitude is it?

[Nergis Mavalvala]

Yeah, so that's sort of a technical detail because you start off with, you know, 100 watts of laser light. And by the time.

[Harrison Greenbaum]

That's a powerful laser.

[Nergis Mavalvala]

Yeah, that's a very powerful, I believe, laser. Particularly if, if it's a laser that's also, you know, as, as quiet, noise, noise free as ours.

What is my laser pointer Your laser.

Pointer is like a milliwatt.

[Harrison Greenbaum]

Yeah.

[Neil DeGrasse Tyson]

Yeah.

[Nergis Mavalvala]

Okay.

[Harrison Greenbaum]

A really bright 1000th, a few thousandths of a watt.

[Nergis Mavalvala]

Right, Gotcha.

[Harrison Greenbaum]

And this is 100 watts.

[Nergis Mavalvala]

Yeah. So this is 100 watts at the laser. And by the time the light has bounced between all the mirrors and so on, at any given instant in time, you could have, you know, hundreds of kilowatts of power circulating in the instrument. But at the time that we detected at the output, you know, we're trying to go for, you know, very little light close to zero. We're measuring something around of order 10ish milliwatts of light.

[Harrison Greenbaum]

Okay. Relative to the hundreds of thousands of milliwatts that are moving around.

[Nergis Mavalvala]

That's right. The more interesting question is you can think about the output of the interferometer is itself just. It's a sinusoidal function. And so the way I like to think about it is we try to park ourselves at a trough in the bottom. At the bottom. And then we're asking what is the smallest amount of light that you can distinguish resolve. And that is how much of phase or distance, path length you're resolving. And so that's the number that corresponds to path length difference of 10 to the minus 18 meters, which is the.

[Harrison Greenbaum]

Fraction of the diameter of a proton.

[Nergis Mavalvala]

That you imagine a thousandth the diameter of a proton.

[Harrison Greenbaum]

Crazy talk. And so she slipped in a nice term in there. I want to pull that out. She mentioned interferometer. Okay. That as a device had to be invented. And it was invented at the turn of the century, the previous century, by Albert Michelson and Morley. What's his first name? I don't remember his first name. The famous Michelson Morley experiment. They invented it to measure the speed of light. So the first truly accurate measurement of the speed of light was by Michelson and Morley using an interferometer where they had waves that either line up or they don't. And the amount that they don't line up will give you information about the speed of the light that they were measuring. So, I mean, it's a hugely power. So they got the Nobel Prize for inventing that device.

[Nergis Mavalvala]

Just giving these things out.

[Harrison Greenbaum]

No tough stuff.

[Nergis Mavalvala]

I think this is the third one we've heard about today. Just handing them out like candy.

[Harrison Greenbaum]

So just. I'm just impressed by how all this comes together.

[Nergis Mavalvala]

I think it's just a reminder to us that every discovery we make is built on everything that came before. Right. Because we've talked about so many things that were invented 100 years ago that were important to the discoveries we made in 2015.

[Harrison Greenbaum]

All right, so take us out with your prediction of what discoveries await us to take the physics we now know into a new place or what new physics needs to arrive to take our understanding of the universe to a new place.

[Nergis Mavalvala]

Yeah. So I would say at the moment, the kinds of objects, astrophysical objects we've seen so far have been collisions of pairs of black holes or pairs of neutron stars, or maybe neutron stars and black holes in the same binary system. And those were predicted. We kind of expected them. But even that has given us mysteries. Like I'll give you an example. We've seen black holes that are around 100 solar masses. We don't know how nature forms those because if they're formed in the same way as black holes that are 20 or 30 solar masses are formed, Stars don't do that.

[Harrison Greenbaum]

Right. We don't that. It means we don't understand how stars are born.

[Nergis Mavalvala]

That's right. Or die. Right, Right.

I always thought it's like you pick up an instrument and you practice a lot how stars born.

[Harrison Greenbaum]

Oh, is that how that works?

[Nergis Mavalvala]

I think there's been three films of that.

[Harrison Greenbaum]

Yeah, they keep making the films. Right.

[Nergis Mavalvala]

What I'm saying is we've had three films to learn how a star.

[Harrison Greenbaum]

But let me just remind you that movie stars are called stars because we had stars first. Okay. We came first.

[Nergis Mavalvala]

Not cause they're filled of gas, hot gas.

[Harrison Greenbaum]

They are named after objects in the universe, not vice versa. Just to be clear.

[Nergis Mavalvala]

But Neel, I think this is a good idea for you. I think you need to make the ultimate Star is born movie about real stars.

[Harrison Greenbaum]

Oh. If we're gonna make the movie again, just make it right.

[Nergis Mavalvala]

Yeah, I agree.

I'll be the one in love with the star.

[Harrison Greenbaum]

Well, thank you for enlightening us here with your insights and your expertise and your deanship.

[Nergis Mavalvala]

Oh, my gosh.

[Harrison Greenbaum]

What I'd like to do is sort of take us out with a cosmic perspective, if I may. This is the part where I just talk to camera and you just pretend like you're paying attention. Once again, we are exposed to major modern discoveries in science, physics in particular, that was enabled by creative thinking that preceded it. Creative engineering, improvements in computational speed. These things happen. Yeah. You can say I got a really fast computer and you can be praised for that. But maybe someone can use that for something that they could not have solved before. I have a new idea about how black holes work. Well, let others know about it, because somebody could have another idea. About how to apply that to a discovery we're not even thinking about now. And so this interconnectivity, this interdependence of cosmic discovery on these multiple frontiers is how science works. People ask, are we approaching the end of science? Well, if you think everything that will ever be discovered has been discovered, then you probably think that. But my read of the history of this exercise tells me that if you think science is about to end, it's because you're not creative enough to imagine where else it could go. And look at all the dangling bits and pieces of all the scientific frontiers and how they might one day come together with the next generation Einstein to take us into the next millennium of cosmic discovery. And that's a cosmic perspective. So, Nergis, thanks for coming back to StarTalk. We dovetailed another talk you were giving at NYU Sister Institution downtown. Thanks for fitting us into your day. And again, it's Maval Valla. Yes, you did that correct.

[Nergis Mavalvala]

Thank you.

[Harrison Greenbaum]

And Harrison, thanks for having me. Great to see you again.

[Nergis Mavalvala]

Same here.

[Harrison Greenbaum]

Good to hear about your show.

[Nergis Mavalvala]

Thank you.

[Harrison Greenbaum]

People can find you Harrison Greenbaum.com HarrisonComedy on social media. You got it. Neil Degrasse Tyson, your personal astrophysicist. As always, I bid you to keep looking up.

[Neil DeGrasse Tyson]

Brought to you by Hularious Stand up Comedy now on Hulu. Hey everybody, Hulu has a bunch of new stand up specials that are not just funny, they're hoolarious. Very funny Hulu. Anyway, they're launching new exclusive stand up specials from awesome comedians like Jim Gavigan, Elana glaser, Roy Wood Jr. Bill Burr and tons more. A new special drops every month and they've got a huge library of stand up specials to check out. Go to Hulu and get your stand up fix now.

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