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Speaker 1: Hey, Daniel, what's the biggest science experiment ever built?

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Speaker 2: Oh? Well, the large Hadron Collider is pretty big. It's

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Speaker 2: thirty three kilometers around.

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Speaker 1: That is pretty big, I guess for human scale, but

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Speaker 1: compared to the universe. I mean the universe is huge, right.

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Speaker 2: That's true. And I guess astrophysicists use the whole universe

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Speaker 2: as an experiment when they like watch black holes collide.

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Speaker 1: M the whole universe is an experiment. What are the results?

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Speaker 2: They're pretty universal?

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Speaker 1: Are they positive or negative?

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Speaker 2: We have only one data point so far, so I

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Speaker 2: think it would be presumptuous to make any conclusions.

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Speaker 1: That's a hypothesis for the universe. It's awesome or not awesome,

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Speaker 1: it's bunkers. I guess you use data from the whole universe.

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Speaker 1: But usually you only detect things with a small telescope, right,

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Speaker 1: or a small Parkle collider.

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Speaker 3: Yeah.

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Speaker 2: The kind of eyeballs we build are usually small, even

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Speaker 2: when we are observing really large things. But there are

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Speaker 2: some really clever approach, which is that use like the

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Speaker 2: whole galaxy as a detector.

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Speaker 1: What is that experiment called?

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Speaker 2: Because it's so gargantua and of course they use the

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Speaker 2: word nano in the title of the experiment.

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Speaker 1: What I guess it's nana compared to the size of

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Speaker 1: the universe.

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Speaker 2: I can't defend astronomers when it comes to naming their experiments.

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Speaker 1: But you can defend particle physicists. You didn't defend anyone

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Speaker 1: in science or how they name things.

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Speaker 2: I'm gonna plead no contest, The.

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Speaker 1: Experiment says no. Hi. I'm Jorhem Mac, cartoonist and the

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Speaker 1: author of Oliver's Great Big Universe. Hi.

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Speaker 2: I'm Daniel. I'm a particle physicist and a professor at

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Speaker 2: UC Irvine, and I think a universe is pretty well named.

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Speaker 1: Apparently not because there's something called the multiverse. So I

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Speaker 1: think if you have to put something in front of

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Speaker 1: it later, it wasn't well named.

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Speaker 2: Oh well, like Superman is not well named because he's

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Speaker 2: a superversion of a man.

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Speaker 1: Well, he's special, but if you have to sort of

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Speaker 1: redefine what that is like, if you had to later

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Speaker 1: name him ultra Superman, then maybe he didn't name him

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Speaker 1: well the first.

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Speaker 2: Time, multi Superman.

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Speaker 1: Maybe there's a universe where Superman was well named, or

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Speaker 1: physicists named their experiments in easy to understand ways.

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Speaker 2: That would be like a superphysicist.

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Speaker 1: But anyways, welcome to our podcast Daniel and Jorge Explain

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Speaker 1: the Universe, a production of iHeartRadio.

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Speaker 2: In which we use our definitely not super brains to

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Speaker 2: try to understand the super mysteries of the entire universe.

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Speaker 2: We hope that everything out there in the universe can

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Speaker 2: be described by simple mathematical recipes that make sense to

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Speaker 2: our mammalian brains, and we do our best to apply

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Speaker 2: those rules to the whole universe to see where they work,

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Speaker 2: where they break down, and where we can explain all

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Speaker 2: of them to you.

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Speaker 1: Yeah, because it's amazing that our tiny little brains can

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Speaker 1: understand universe, that we can look out into the cosmos

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Speaker 1: to get data and figure out how things work. Fortunately,

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Speaker 1: the universe likes to reveal itself sometimes.

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Speaker 2: Sometimes we have to be clever and build really interesting

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Speaker 2: little apparatuses to like smash particles together or balance balls

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Speaker 2: against each other in order to extract some information from

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Speaker 2: the universe. We like concoct special setups that we hope

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Speaker 2: will reveal deep truths about the universe. But not everybody

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Speaker 2: gets to do that. Not everybody gets to build their

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Speaker 2: own experiments. Some people have to go out there and

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Speaker 2: find the experiments happening in nature.

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Speaker 1: Yeah, because science is a continuing story and there are

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Speaker 1: new things being learned every day and new ways to

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Speaker 1: look at the universe being discovered every day. And so

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Speaker 1: this week there was a very special news about a

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Speaker 1: new experiment that just revealed the data it's found.

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Speaker 2: That's right after analyzing fifteen years worth of observational data.

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Speaker 2: The Nanograph experiment has just made a dramatic announcement about

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Speaker 2: their fantastic new discscovery.

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Speaker 1: You might have seen it on the news. It's sort

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Speaker 1: of a big deal for this community of astrophysicists.

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Speaker 2: It's literally sending waves through the cosmological community.

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Speaker 1: But hopefully the results aren't the wavy or shaky.

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Speaker 2: It's a bit of a treacherous territory because, as we

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Speaker 2: all know, claims of the discovery of gravitational waves have

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Speaker 2: either been verified and led to Nobel prices or have

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Speaker 2: been debunked and led to some quite red faces in

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Speaker 2: the cosmological community.

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Speaker 1: And so this week there was a big announcement by

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Speaker 1: an experience called Nanograph. Now, Daniel, is that an acronym

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Speaker 1: or do they just like the word nano?

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Speaker 2: You know, I think The answer to that is yes

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Speaker 2: on both counts. It is an acronym. It stands for

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Speaker 2: North American Nanohertz Observatory for Gravitational Radiation. So they both

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Speaker 2: like the word NANO because it's in their title and

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Speaker 2: it's an acronym.

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Speaker 1: Wait what, it's a recursive title, like the word nano

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Speaker 1: is in the acronym NANO exactly.

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Speaker 2: And because NANOGrav is one of these really clever device

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Speaker 2: that uses the entire galaxy as a detector for gravitational waves,

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Speaker 2: you might think that they would choose something which describes

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Speaker 2: the scale the grandeur of that experiment, But instead they've

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Speaker 2: chosen NANO, which reflects the very short frequency of these

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Speaker 2: gravitational waves.

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Speaker 3: Mmm.

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Speaker 1: Yeah, I saw Did you said the word nano hurts?

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Speaker 1: I guess that's the frequency of gravitational waves that they

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Speaker 1: have detected.

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Speaker 2: That's right. The huge scale of the galaxy allows them

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Speaker 2: to measure really long wavelength, low frequency gravitational waves that

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Speaker 2: other gravitational wave detectors Ligo and virgo and all of

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Speaker 2: those could never see, giving us a whole new window

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Speaker 2: into what's going on in the universe.

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Speaker 1: So today on the podcast, we'll be tackling the question,

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Speaker 1: how did the nanograph experiment use the galaxy as a detector? Now,

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Speaker 1: did they ask the galaxy's pervision before they did this?

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Speaker 2: We've been over this before. The universe has no right

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Speaker 2: to privacy inherently, man, we can ask whatever question we want.

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Speaker 1: Is it in the fine print? Or are we going

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Speaker 1: to get sued later?

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Speaker 2: I checked with our legal team. They're fine with it.

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Speaker 1: We have a legal team.

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Speaker 2: I'm the legal team.

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Speaker 1: Yeah. I think that means we don't have a legal team.

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Speaker 1: That's I check. You're not a lawyer, that is correct.

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Speaker 2: Do not take any legal advice for me.

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Speaker 1: So this is one of those large physics collaborations. And

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Speaker 1: I guess nano sound small because we're used to associating

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Speaker 1: the word nano with distances, right, like nanometer as being

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Speaker 1: super tiny, or the scale of atoms and things like that.

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Speaker 1: But here it sort of refers to frequency, which actually

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Speaker 1: is sort of like the inverse kind of our intuition

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Speaker 1: a lot of times, right, And so nano here actually

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Speaker 1: means big.

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Speaker 2: Yeah, that's right. You have to think about waves wiggling, right,

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Speaker 2: and waves that wiggle at really high speed, things like

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Speaker 2: gravitational waves which move at the speed of light have

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Speaker 2: a connection between their frequency and their wavelength, just the

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Speaker 2: way light does. High frequency light has very short wavelengths.

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Speaker 2: Very low frequency light like radio waves, has longer wavelengths.

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Speaker 2: And the nanograph experiment is looking for huge gravitational waves,

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Speaker 2: gravitational waves which dwarf the size even of our solar system,

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Speaker 2: and so they have to look for very very low frequency,

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Speaker 2: very tiny frequencies nano hurts, which means like a frequency

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Speaker 2: of one times ten of the minus nine.

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Speaker 1: Yeah, because I guess when you hear the word like

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Speaker 1: giger hurts or megaherts, it's a super high frequency that

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Speaker 1: happens really fast and very short wavelengths. But if you

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Speaker 1: hear nanoherds, that means that it's like a super low frequency,

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Speaker 1: like it takes years and years for a wave to

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Speaker 1: go by.

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Speaker 2: Maybe that's right. One nanohurtz means one wiggle every thirty years. Whoa.

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Speaker 1: And so they recently announced a big result after a

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Speaker 1: long time that they've been at this using their technology

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Speaker 1: to detect gravitation waves, and this week they made the announcement, right,

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Speaker 1: which made the news.

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Speaker 2: That's right, And they've been hinting at this for several

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Speaker 2: weeks that they have something very big to share, and

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Speaker 2: people have known that they were going to have enough

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Speaker 2: data to say something interesting for a little while. We

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Speaker 2: covered them on the podcast a few years ago when

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Speaker 2: they had very preliminary data. They didn't have yet conclusive results,

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Speaker 2: but we were very excited to hear what they were

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Speaker 2: going to have to say in a few years. And

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Speaker 2: that day is today.

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Speaker 1: So let's dig into what their result was and how

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Speaker 1: this experiment worked and how they use the whole galaxy

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Speaker 1: basically as a detector.

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Speaker 2: So what they're looking for are gravitational waves, which you

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Speaker 2: have to remember are not a wave like a wave

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Speaker 2: in water, that they have a lot of similar mathematical properties.

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Speaker 2: Gravitational waves are waves in space itself. General relativity tells

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Speaker 2: us that gravity is the curvature of space, which really

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Speaker 2: just means you're changing their relative distances between points in space,

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Speaker 2: and so gravitational waves are like ripples through space where

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Speaker 2: things get closer together and further apart, closer together and

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Speaker 2: further apart, like space itself is oscillating.

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Speaker 1: Yeah, because we know space isn't just like the emptiness

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Speaker 1: of the universe. It's actually sort of like a thing, right,

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Speaker 1: like you can bend it and squeeze it and curve it. Right.

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Speaker 2: Yeah, that's exactly right. And those features of space are

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Speaker 2: what give rise to our sense of gravity. If space

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Speaker 2: was totally flat and smooth, there had no curvature to it,

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Speaker 2: then things would just moved through it in straight lines

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Speaker 2: that look straight to us. But because space has this

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Speaker 2: sort of invisible curvature to it, things in free fall

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Speaker 2: tend to follow the curvature of space, following those curves

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Speaker 2: and bends and wiggles, which to us look like something

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Speaker 2: is pushing on it to make it change its direction.

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Speaker 1: That's kind of the Einstein view of the universe, right,

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Speaker 1: that gravity is not a force that pulls on you,

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Speaker 1: but it actually kind of bends space time around you

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Speaker 1: to make you move in certain ways.

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Speaker 2: That's right. That's general relativity in fifteen.

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Speaker 1: Seconds done in nanotime, nanorelativity nanoscience podcast. But yeah, it's

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Speaker 1: kind of this idea that space kind of bends, right,

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Speaker 1: and it can wiggle, especially when you move masses through it.

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Speaker 2: Exactly, And we know that Einstein improved on Newton's idea

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Speaker 2: of gravity. Newton had the idea that gravity was a force,

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Speaker 2: and Einstein replaces it with this concept of space being bent.

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Speaker 2: But there's another important consequence of Einstein's update to Newton's

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Speaker 2: idea which gives us these waves, which is that gravitational

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Speaker 2: information is not instant. According to Newton, if you had

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Speaker 2: deleted the Sun from the universe, you would instantly feel

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Speaker 2: across space and time the absence of the Sun's gravity.

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Speaker 2: But Einstein tells us that if you delete the Sun,

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Speaker 2: that information takes time to propagate. Space doesn't like snap

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Speaker 2: back instantaneously. Everywhere in the universe, there's propagation of information,

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Speaker 2: and you can think of gravitational waves sort of as

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Speaker 2: the propagation of information, the same way that if you

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Speaker 2: wiggle an electron, you make wiggles in the electromagnetic field,

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Speaker 2: which we can think of as photons. If you wiggle

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Speaker 2: the Sun, or if you move any massive body, you

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Speaker 2: make wiggles in space, which we can think of as

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Speaker 2: gravitravitational waves.

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Speaker 1: Yeah, it's interesting you call it the propagation of information.

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Speaker 1: It's sort of I guess like if you stand in

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Speaker 1: the middle of the field and you scream, it's going

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Speaker 1: to take a while for that scream to get to places.

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Speaker 2: Man, what a dark example. Why are you standing in

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Speaker 2: the middle of fields and screaming. Is this like some

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Speaker 2: new performance art.

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Speaker 1: Yeah, I'm screaming with joy. Yeah at the fact that

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Speaker 1: nanograph has discovered that's something interesting this week. Yeah.

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Speaker 2: Maybe what we've actually discovered is aliens all across the

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Speaker 2: universe screaming in their fields. Yes, but you're exactly right.

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Speaker 2: Information always takes time to propagate, and that includes the

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Speaker 2: curvature of space time. So anything that wiggles, anything that's

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Speaker 2: accelerating in the universe is making gravitational waves. Now, gravity

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Speaker 2: is a really weak force, so when you accelerate your

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Speaker 2: arm up and down, you are technically making gravitational waves,

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Speaker 2: but they're super duper weak. So in order to see

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Speaker 2: gravitational waves, we tend to need really really high masses

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Speaker 2: undergoing huge accelerations, which is why the target foreseeing gravitational

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Speaker 2: waves are typically things like black holes swinging around each

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Speaker 2: other super duper fast the moments before they merge.

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Speaker 1: It's interesting, just going back you describe it as how

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Speaker 1: information about it propagates. I guess it's sort of like

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Speaker 1: if the sun suddenly moved a meter to the right,

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Speaker 1: it would take some time for us, and the gravity

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Speaker 1: we feel from the Sun to feel that shift in

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Speaker 1: the sun, right, and then if the sun went back

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Speaker 1: to its original position, it would take a little bit

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Speaker 1: of time for us to feel that it went back

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Speaker 1: to its original position. And so that kind of going

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Speaker 1: back and forth is kind of what you can call

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Speaker 1: gravitational wave.

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Speaker 2: Right.

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Speaker 1: It's like the effect of the Sun through gravity. How

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Speaker 1: the effect of the Sun propagates mm hmm.

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Speaker 2: If you're holding a string and your friend a mile

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Speaker 2: away is holding a string and they wiggle their end

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Speaker 2: of the string, You're not going to feel your end

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Speaker 2: wiggle instantly. It's going to take a while for that

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Speaker 2: wiggle to travel down the string. If you wiggle the Sun,

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Speaker 2: it changes the curvature of space and it takes a

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Speaker 2: while for that wiggle to get to Earth. Those are

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Speaker 2: gravitational waves.

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Speaker 1: So I guess you could describe it two ways. It's

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Speaker 1: like it's the Sun bending the space around it, or

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Speaker 1: it's also you can think of it as the effect

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Speaker 1: of the Sun through gravity being kind of changing over time.

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Speaker 2: Yeah, I think those are both accurate. I tend to

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Speaker 2: think of it the first way. That's the Einsteinian way.

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Speaker 2: It's changing the curvature of space time around it gravity

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Speaker 2: is an effect of that curvature.

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Speaker 1: So a gravitational waves sort of made the news maybe

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Speaker 1: like five I think, I want to say five maybe

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Speaker 1: years ago. That's kind of when they entered the popular culture,

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Speaker 1: because that's when we started to be able to listen

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Speaker 1: to them, right through an experiment called Ligo.

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Speaker 2: That's right. We had strong hints that gravitational waves were

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Speaker 2: a real thing decades before that, when we saw neutron

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Speaker 2: stars orbiting each other and they're orbit decayed and exactly

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Speaker 2: the way you'd expect if they were losing energy to

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Speaker 2: gravitational radiation. But the first direct proof was observations by

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Speaker 2: Ligo and Virgo in twenty sixteen of black hole mergers

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Speaker 2: giving off these gravitational radiations using this incredible bravura technique

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Speaker 2: of these lasers underground between mirrors kilometers apart, looking for

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Speaker 2: variations in the distance between these mirrors of one part

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Speaker 2: in ten to the twenty. So that was really a

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Speaker 2: very spectacular confirmation that gravitational waves are a real thing

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Speaker 2: in our universe.

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Speaker 1: Yeah, we know they exist, and they're pretty awesome because

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Speaker 1: they tell us a lot about these huge events going

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Speaker 1: out there in the cosmos. But Apparently, these things only

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Speaker 1: tell us about a very maybe narrow window of things

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Speaker 1: that can happen with gravitational waves out there in the

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Speaker 1: universe exactly.

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Speaker 2: Logo and Virgo are sensitive to gravitational waves of a

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Speaker 2: certain frequency basically because of their size, Lego and Virgo

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Speaker 2: can only really see gravitational waves that are about the

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Speaker 2: size of their detector. The gravitational wave was much much

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Speaker 2: bigger than it wouldn't have an observable effect on their detector.

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Speaker 2: It would like wiggle too slowly. So Logo and Virgo

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Speaker 2: are built to be able to see stellar mass black

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Speaker 2: holes like black holes of ten or twenty or thirty

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Speaker 2: or forty times the mass of our Sun emerging. They've

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Speaker 2: seen dozens and dozens of those. It's very, very exciting.

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Speaker 2: But they can't see things like super massive black hole mergers,

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Speaker 2: which are predicted to happen when galaxies collide. And they

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Speaker 2: also can't see like echoes from the Big Bang itself,

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Speaker 2: which would leave gravitational waves with huge wavelengths interesting.

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Speaker 1: All right, Well, let's dig into these other kinds of

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Speaker 1: gravitational wave events that can happen out there in the

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Speaker 1: universe and how the NANOGrav experiment has apparently maybe seen

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Speaker 1: some of those, So let's dig into that be first,

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Speaker 1: let's take a quick break. All right, we're talking about

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Speaker 1: the recently announced results of the NANOGrav experiment that have

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Speaker 1: to do with gravitational waves, big gravitation waves.

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Speaker 2: That's right, and not to take anything away from Lego

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Speaker 2: and Virgo, it's really impressive that they saw anything at all.

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Speaker 2: I mean, I remember having the opportunity to join those

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Speaker 2: bariments when I was picking graduate schools, and I thought,

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Speaker 2: those guys are never going to make that work. And hey,

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Speaker 2: that's not the first Nobel Prize that I've missed out on.

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Speaker 1: You've had several happened, we all.

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Speaker 2: I mean, there's this thing in research where you have

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Speaker 2: to sort of make a gamble, like is this going

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Speaker 2: to be a fruitful thing to do? And part of

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Speaker 2: it depends on your smarts and your hard work, and

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Speaker 2: part of it just depends on the universe. Is there

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Speaker 2: something there to discover? You build this new kind of

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Speaker 2: telescope and use it to look out into the world.

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Speaker 2: Is there something there for you to see? Lego and Virgo,

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Speaker 2: We're definitely lucky because there are a lot more black

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Speaker 2: holes out there than we thought.

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Speaker 1: Wow, aren't you sort of assuming that if you had

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Speaker 1: joined that collaboration, they still would have discovered gravitational waves?

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Speaker 1: I mean, aren't assuming something there?

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Speaker 2: Yeah, you're right, I might have poisoned the entire process,

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Speaker 2: or maybe it would have happened much faster. Who knows.

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Speaker 1: We'll never know or never.

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Speaker 2: No, you never really get to open those other doors

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Speaker 2: and know what your other lives might have been.

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Speaker 1: You need like a superhero movie to explore the multiverse.

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Speaker 2: But we all do make these choices as sciences to

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Speaker 2: say I'm going to devote my life to this one

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Speaker 2: particular way to maybe learn something about the universe.

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Speaker 1: Cool. Well, we're talking about there recently announced results from

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Speaker 1: the NANOGrav experiment, which is a big collaboration of many

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Speaker 1: different places, right, not just in North America. I mean

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Speaker 1: the name is North American Nanohertz Observatory, but actually they

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Speaker 1: use I think places from all over the world.

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Speaker 2: Well, NANOGrav uses Arecibo and the Green Bank Telescope in

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Speaker 2: West Virginia and the very large Array in New Mexico.

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Speaker 2: But you're right, there are definitely pulsar observatories all over

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Speaker 2: the world. In Australia and in Europe and in China,

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Speaker 2: and there are other competing collaborations. So NANOGrav represents like

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Speaker 2: the North American slice of the world.

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Speaker 1: And so we were talking about earlier how NANOGrav looks

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Speaker 1: for gravitation waves in different wavelengths of gravitation waves than

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Speaker 1: Ligo and virgo.

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Speaker 2: That's right, NANOGrav is looking for something much much bigger

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Speaker 2: than Lego and Virgo is looking for, and something much

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Speaker 2: bigger than like and Virgo can even see. Something important

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Speaker 2: to understand is like when black holes merge, the ones

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Speaker 2: that Lego and Virgo do see, they're emitting gravitational waves

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Speaker 2: during the entire merger, but Lego and Virgo can only

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Speaker 2: see at the very end because it speeds up and

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Speaker 2: gets shorter wavelengths, and that's what Lego and Virgo can see.

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Speaker 2: So they're only seeing like the last little bit of

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Speaker 2: that merger when it's in their little window.

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Speaker 1: Now, is that because of the sort of frequency limitation

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Speaker 1: or is that because when those black holes merge, that's

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Speaker 1: when the gravitation waves get really big, Right when they're

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Speaker 1: closing in on each other and circling each other really fast,

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Speaker 1: that's when there's a lot of acceleration by those masses,

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Speaker 1: and that's when maybe we get waves that we can

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Speaker 1: detect here on Earth.

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Speaker 2: Yeah, it's both factors. The amplitude is too small during

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Speaker 2: the earlier part of the merger, and the frequency is wrong.

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Speaker 2: Loco and Virgo are sensitive across a certain frequency range,

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Speaker 2: and it's limited by a couple of things. One is

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Speaker 2: just the size of their detector. Your few detector is

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Speaker 2: only a few kilometers long. You can't detect changes over

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Speaker 2: light years. There's like no variation across your detector.

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Speaker 1: Wouldn't be easier though, Like if you you know, like

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Speaker 1: a slower wave, wouldn't your detector be able to catch

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Speaker 1: those better if it had the same amplitude.

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Speaker 2: Well, think about it in terms of the distance, Like,

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Speaker 2: it's much harder to measure the curvature of the Earth

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Speaker 2: if the Earth is much much bigger than your ruler. Right,

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Speaker 2: like to us, the Earth looks almost flat. You can't

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Speaker 2: even really detect the curvature, and so detecting small changes

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Speaker 2: in the curvature is really hard. But if you're like

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Speaker 2: the little prints and you're on a planet where like

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Speaker 2: the planet is basically the size of your ruler, it's

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Speaker 2: much easier to measure the curvature and the changes in

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Speaker 2: the curvature. So here and now we're like sitting on

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Speaker 2: a huge wave. If the wave is like the size

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Speaker 2: of the galaxy, there's no way that your little two

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Speaker 2: kilometer ruler is going to be able to measure any

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Speaker 2: change in that.

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Speaker 1: Wave unless the change is really big, right, like the

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Speaker 1: amplitude of those low frequency waves. We would be able

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Speaker 1: to detect them, but maybe we don't get those here.

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Speaker 2: Yeah, if it's big enough, then you can detect it

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Speaker 2: in any way. But there's another factor, which is noise suppression.

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Speaker 2: These things have to be able toinguish real gravitational waves

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Speaker 2: from other kinds of wiggles. And because Ligo and Virgo

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Speaker 2: are on Earth, there's seismic noise, and that seismic noise

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Speaker 2: tends to be lower frequency, and so it sort of

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Speaker 2: creates a wall that Ligo and Virgo just can't see beyond.

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Speaker 1: Okay, So then the nanograph is a different experiment from LGO,

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Speaker 1: and it use is a totally different technology and method. Right.

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Speaker 1: They didn't even sort of have to build really a detector.

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Speaker 1: They just sort of used existing radio antennas that we have, right, Yeah,

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Speaker 1: they both.

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Speaker 2: Use existing sources of radio waves, meaning pulsars scattered through

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Speaker 2: the galaxy and existing telescopes that can see those radio waves.

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Speaker 2: So it's really just like a clever combination of stuff

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Speaker 2: that's already out there. It's really one of my favorite

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Speaker 2: examples of like just ingenuity and physics.

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Speaker 1: Yeah, it's pretty cool. And so the idea is that

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Speaker 1: they're using pulsars to detect kind of how the whole

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Speaker 1: galaxy reacts to a gravitational wave, right.

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Speaker 2: Yeah, that's exactly right. They want to see really big

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Speaker 2: gravity waves on the scale of the galaxy, and so

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Speaker 2: they want to see the galaxy itself sort of change shape.

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Speaker 2: Like what Lego and Virgo do is they have this

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Speaker 2: big l they construct with mirrors, and they see a

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Speaker 2: chain shape. They see one side get shorter, another side

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Speaker 2: get longer, the whole thing oscillates. So NANOGrav and the

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Speaker 2: other pulsar timing arrays want to do the same thing

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Speaker 2: for the whole galaxy, but they can't like go out

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Speaker 2: there and you know, build lasers and mirrors that are

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Speaker 2: on the scale of the galaxy. So they're just watching

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Speaker 2: the pulsars and they're using very precise timing measurements from

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Speaker 2: these pulsars to measure how the galaxy itself is squishing.

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Speaker 1: Well, I mean, come on, they could build space lasers

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Speaker 1: if they wanted to.

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Speaker 2: Who doesn't want to write? I mean, when I go

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Speaker 2: out in a field and scream, I'm screaming, let's build

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Speaker 2: space lasers.

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Speaker 1: Yeah, let's do it.

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Speaker 2: But this is really awesome because it takes advantage of

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Speaker 2: the universe as sort of a natural set of clocks.

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Speaker 2: These pulsars are really cool, fascinating end point of stars

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Speaker 2: and your stars out there that are burning bright and

439
00:22:01,760 --> 00:22:04,920
Speaker 2: turning their fuel into light, and then eventually they collapse

440
00:22:04,960 --> 00:22:07,639
Speaker 2: with like a type two supernova and they leave behind

441
00:22:07,720 --> 00:22:11,480
Speaker 2: this core, this very very dense object, a neutron star,

442
00:22:12,080 --> 00:22:15,440
Speaker 2: which is something that has like a ten kilometer radius

443
00:22:15,440 --> 00:22:17,600
Speaker 2: but weighs as much as our sun.

444
00:22:18,560 --> 00:22:20,800
Speaker 1: Yeah. I think we've had one or a couple of

445
00:22:21,040 --> 00:22:24,879
Speaker 1: episodes about pulsars and neutron stars. They're not burning like

446
00:22:24,960 --> 00:22:27,439
Speaker 1: regular stars, but they are giving off a lot of

447
00:22:27,560 --> 00:22:30,040
Speaker 1: light right because they are still really hot.

448
00:22:30,119 --> 00:22:32,879
Speaker 2: They are definitely still hot because they're super dense, but

449
00:22:32,880 --> 00:22:35,399
Speaker 2: there's no fusion going on inside of them, so they

450
00:22:35,400 --> 00:22:38,160
Speaker 2: don't glow in the typical wavelengths. Sometimes you can see

451
00:22:38,280 --> 00:22:40,800
Speaker 2: X rays from cracks on their surface. But what we're

452
00:22:40,800 --> 00:22:43,000
Speaker 2: interested in this case is the beam that they emit

453
00:22:43,200 --> 00:22:46,639
Speaker 2: along their magnetic north and south poles. They generate some

454
00:22:46,720 --> 00:22:49,840
Speaker 2: radiation from like motion of charged particles on the surface

455
00:22:49,920 --> 00:22:52,520
Speaker 2: on the crust of the neutron star, and they have

456
00:22:52,560 --> 00:22:56,200
Speaker 2: this very strong magnetic field which slurfs those charged particles

457
00:22:56,240 --> 00:22:58,959
Speaker 2: in that radiation sort of up the north pole and

458
00:22:59,000 --> 00:23:02,960
Speaker 2: down the south pole creates these massive beams of radiation

459
00:23:03,480 --> 00:23:05,880
Speaker 2: along the north and south pole of the pulsar.

460
00:23:06,160 --> 00:23:08,879
Speaker 1: Now this happens with every neutron star, or only some

461
00:23:09,119 --> 00:23:13,480
Speaker 1: neutron stars have this beam of radiation going out of

462
00:23:13,520 --> 00:23:14,080
Speaker 1: its poles.

463
00:23:14,200 --> 00:23:17,000
Speaker 2: Not every neutron star is a pulsar. And we do

464
00:23:17,080 --> 00:23:20,240
Speaker 2: not understand very well both the source of the radiation.

465
00:23:20,600 --> 00:23:22,600
Speaker 2: You think maybe it comes from a combination the rotation

466
00:23:22,680 --> 00:23:25,200
Speaker 2: of this object and the charged particles on the surface,

467
00:23:25,720 --> 00:23:28,560
Speaker 2: And we don't really understand very well the source of

468
00:23:28,640 --> 00:23:32,720
Speaker 2: incredibly strong magnetic fields from neutron stars. But not every

469
00:23:32,760 --> 00:23:36,159
Speaker 2: neutron star spins this way and has these magnetic fields

470
00:23:36,160 --> 00:23:37,160
Speaker 2: and is a pulsar.

471
00:23:37,480 --> 00:23:39,200
Speaker 1: Or can we see it right? Because I think the

472
00:23:39,280 --> 00:23:42,520
Speaker 1: idea is that you have this neutron star that's a

473
00:23:42,560 --> 00:23:46,360
Speaker 1: magnetic field. It's shooting out basically like radiation beams out

474
00:23:46,359 --> 00:23:49,440
Speaker 1: of its poles, and it's also spinning. The whole thing

475
00:23:49,480 --> 00:23:51,480
Speaker 1: is spinning sort of like a lighthouse, right.

476
00:23:51,920 --> 00:23:55,200
Speaker 2: And the magnetic north pole is not aligned with the spin,

477
00:23:55,640 --> 00:23:58,520
Speaker 2: so the magnetic north pole and the beam sweeps across

478
00:23:58,560 --> 00:23:59,280
Speaker 2: the universe.

479
00:23:59,560 --> 00:24:01,440
Speaker 1: Yeah. I guess it's sort of like when you spin

480
00:24:01,480 --> 00:24:04,560
Speaker 1: a top on the floor and it starts to slow down,

481
00:24:04,680 --> 00:24:06,359
Speaker 1: it starts to kind of spin in a kind of

482
00:24:06,400 --> 00:24:08,960
Speaker 1: wiggly fashion, right, And so if it has like a

483
00:24:09,000 --> 00:24:12,200
Speaker 1: flashlight at the top of the top, then that flashlight

484
00:24:12,280 --> 00:24:14,119
Speaker 1: is going to kind of sweep around, sort of like

485
00:24:14,160 --> 00:24:15,280
Speaker 1: a lighthouse.

486
00:24:15,359 --> 00:24:17,840
Speaker 2: Yeah. Well, these guys aren't wiggling, like they're spinning very

487
00:24:17,920 --> 00:24:20,840
Speaker 2: very regularly. But the flashlight is sort of offset from

488
00:24:20,880 --> 00:24:22,840
Speaker 2: the axis of spin, so it's sort of like you're

489
00:24:22,880 --> 00:24:25,520
Speaker 2: spinning around. If you held the flashlight straight up, it

490
00:24:25,520 --> 00:24:27,679
Speaker 2: would always point in the same direction. But if you

491
00:24:27,680 --> 00:24:30,320
Speaker 2: held the flashlight at an angle from the axis where

492
00:24:30,320 --> 00:24:32,600
Speaker 2: you're spinning, then it's going to sweep around the room

493
00:24:32,640 --> 00:24:35,359
Speaker 2: and light up different corners. So that's what's happening with

494
00:24:35,400 --> 00:24:38,520
Speaker 2: a pulsar is the angle of radiation is different from

495
00:24:38,560 --> 00:24:40,440
Speaker 2: the angle of the spin of the star.

496
00:24:41,200 --> 00:24:43,639
Speaker 1: But I guess what would make the magnetic axis be

497
00:24:43,720 --> 00:24:44,879
Speaker 1: different than the spin axis.

498
00:24:45,000 --> 00:24:47,120
Speaker 2: Yeah, I wish I knew. It's the same on Earth though, right.

499
00:24:47,160 --> 00:24:49,320
Speaker 2: The Earth's magnetic north pole is not the same as

500
00:24:49,320 --> 00:24:50,880
Speaker 2: our spin axis north pole.

501
00:24:51,200 --> 00:24:53,720
Speaker 1: Right, And that's because the stuff inside of Earth is

502
00:24:53,760 --> 00:24:55,440
Speaker 1: spinning in a kind of weird way, right.

503
00:24:55,520 --> 00:24:58,280
Speaker 2: Yeah, And again not something that we understand very well.

504
00:24:58,280 --> 00:25:01,119
Speaker 2: In the Earth's magnetic field even fl every once in

505
00:25:01,160 --> 00:25:04,480
Speaker 2: a while, as does the suns, So that's a whole

506
00:25:04,560 --> 00:25:07,159
Speaker 2: murky era of research we don't understand very well. But

507
00:25:07,200 --> 00:25:09,760
Speaker 2: something that is amazing, and it makes the physics that

508
00:25:09,880 --> 00:25:12,600
Speaker 2: nanograb is doing possible, is that the whole thing is

509
00:25:12,680 --> 00:25:15,720
Speaker 2: super duper regular. It doesn't wiggle a lot. When this

510
00:25:15,760 --> 00:25:18,119
Speaker 2: thing spins, it spins at a very specific rate. And

511
00:25:18,160 --> 00:25:21,800
Speaker 2: when a pulse reaches Earth, it reaches Earth very very regularly.

512
00:25:21,880 --> 00:25:25,399
Speaker 2: Like the time between the pulses is extraordinarily predictable.

513
00:25:26,400 --> 00:25:29,080
Speaker 1: I guess what makes it so predictable. I guess just

514
00:25:29,080 --> 00:25:33,120
Speaker 1: because it's an object in space spinning, and so therefore

515
00:25:33,200 --> 00:25:34,360
Speaker 1: it's pretty regular.

516
00:25:34,160 --> 00:25:36,640
Speaker 2: It's very dense, it's very high energy. I guess it's

517
00:25:36,680 --> 00:25:39,000
Speaker 2: just not interfered with a lot. You know, in principle,

518
00:25:39,040 --> 00:25:41,720
Speaker 2: everything is predictable, but some things are more complicated because

519
00:25:41,720 --> 00:25:45,040
Speaker 2: they are chaotic. They're like multi object systems. But here

520
00:25:45,080 --> 00:25:48,119
Speaker 2: you have an intense source of radiation and an object

521
00:25:48,160 --> 00:25:50,520
Speaker 2: that's sort of isolated. It's the left over core of

522
00:25:50,600 --> 00:25:51,080
Speaker 2: this star.

523
00:25:51,680 --> 00:25:53,720
Speaker 1: Okay, so that's a pulsar, which is a kind of

524
00:25:53,760 --> 00:25:57,720
Speaker 1: neutron star that has its neetic axis, ask you from

525
00:25:57,760 --> 00:25:59,919
Speaker 1: its spinning axes, and so therefore we can sort of

526
00:26:00,040 --> 00:26:03,080
Speaker 1: we sort of get hit by its radiation beams sometimes

527
00:26:04,160 --> 00:26:06,359
Speaker 1: or regularly like a clock. These are kind of spread

528
00:26:06,400 --> 00:26:07,639
Speaker 1: all over the galaxy.

529
00:26:07,320 --> 00:26:10,440
Speaker 2: Right, Yeah, that's exactly right, and they vary in their frequency.

530
00:26:10,600 --> 00:26:13,880
Speaker 2: Some of them spin super duper fast. These are called

531
00:26:13,880 --> 00:26:17,440
Speaker 2: like millisecond pulsars, which means that it's spinning so fast

532
00:26:17,480 --> 00:26:20,400
Speaker 2: that the time between pulses is in the order of milliseconds,

533
00:26:20,440 --> 00:26:23,359
Speaker 2: which means the whole neutron star spins around thousands of

534
00:26:23,400 --> 00:26:26,840
Speaker 2: times per second. It's wild, it's really incredible, and by

535
00:26:26,920 --> 00:26:29,560
Speaker 2: looking at the pattern of the timing, we can extract

536
00:26:29,640 --> 00:26:33,040
Speaker 2: a lot of information about what's going on near that

537
00:26:33,160 --> 00:26:34,000
Speaker 2: neutron star.

538
00:26:34,200 --> 00:26:36,600
Speaker 1: So you're saying the frequency sort of depends on the

539
00:26:36,800 --> 00:26:39,439
Speaker 1: kind of the physics of that star, what's going on

540
00:26:39,520 --> 00:26:40,600
Speaker 1: inside of it exactly.

541
00:26:40,640 --> 00:26:42,320
Speaker 2: And you can watch one of these things for a

542
00:26:42,320 --> 00:26:45,280
Speaker 2: long time and learn what its frequency is, and then

543
00:26:45,320 --> 00:26:47,800
Speaker 2: if that frequency changes, if you notice like, oh wait,

544
00:26:47,840 --> 00:26:50,920
Speaker 2: there was a longer time between these last two blips,

545
00:26:51,080 --> 00:26:54,120
Speaker 2: that tells you something about what's going on between you

546
00:26:54,240 --> 00:26:58,480
Speaker 2: and that neutron star. If, for example, a huge gravitational

547
00:26:58,520 --> 00:27:01,280
Speaker 2: wave wiggle through the gallery, see, it would make some

548
00:27:01,320 --> 00:27:03,800
Speaker 2: of these neutron stars further away from us and other

549
00:27:03,840 --> 00:27:07,440
Speaker 2: neutron stars closer, and so it would vary the timing

550
00:27:07,480 --> 00:27:10,320
Speaker 2: pattern of those neutron star pulse.

551
00:27:10,119 --> 00:27:15,760
Speaker 1: Arrivals because it's making the star further and pushing it

552
00:27:15,800 --> 00:27:18,680
Speaker 1: away from us and then towards us. Or because it's

553
00:27:18,720 --> 00:27:22,720
Speaker 1: sort of affecting like the path that the light has

554
00:27:22,760 --> 00:27:24,400
Speaker 1: to travel as it gets here.

555
00:27:24,640 --> 00:27:26,240
Speaker 2: What's the difference between those two.

556
00:27:26,320 --> 00:27:28,480
Speaker 1: Like you could maybe have a gravitation wave happen in

557
00:27:28,520 --> 00:27:33,200
Speaker 1: the middle and it might not move necessarily the pulsar,

558
00:27:33,359 --> 00:27:35,520
Speaker 1: but it might affect the photons that are on the way.

559
00:27:35,640 --> 00:27:37,240
Speaker 2: Well, this is really similar to the way we think

560
00:27:37,280 --> 00:27:39,960
Speaker 2: about the expansion of space. You know, how the universe

561
00:27:40,000 --> 00:27:43,600
Speaker 2: itself is expanding. Gravitational waves have that same effect. They

562
00:27:43,600 --> 00:27:46,960
Speaker 2: expand or contract space and in the same way. You

563
00:27:46,960 --> 00:27:49,480
Speaker 2: can think about in two different ways, like the literal

564
00:27:49,600 --> 00:27:53,840
Speaker 2: distance between us and the object is increasing, or that

565
00:27:53,880 --> 00:27:58,280
Speaker 2: it's expanding the photons as they're moving between here and there. Fundamentally,

566
00:27:58,280 --> 00:28:00,679
Speaker 2: those are the same picture of mathemat to me, the

567
00:28:00,720 --> 00:28:02,440
Speaker 2: most intuitive way to think about it is that it's

568
00:28:02,480 --> 00:28:05,879
Speaker 2: literally increasing the distance between us and the pulsar, and

569
00:28:05,920 --> 00:28:08,200
Speaker 2: so it takes longer for those photons to arrive.

570
00:28:08,640 --> 00:28:10,320
Speaker 1: That's a pretty cool idea. I guess you're sort of

571
00:28:10,359 --> 00:28:13,720
Speaker 1: listening to the blips coming from this pulsar, like it's

572
00:28:13,760 --> 00:28:16,560
Speaker 1: going beep beep, beep, beep, beep, beep beep, and if

573
00:28:16,560 --> 00:28:19,639
Speaker 1: the frequency changes, like it only gets really fast and

574
00:28:19,760 --> 00:28:22,960
Speaker 1: then really slow, then you know that something happened maybe

575
00:28:23,560 --> 00:28:25,879
Speaker 1: to the distance between here and that pulsar, and that

576
00:28:26,160 --> 00:28:28,720
Speaker 1: change in the distance could be a rotation wave.

577
00:28:28,680 --> 00:28:31,200
Speaker 2: Exactly, And for an individual pulsar, lots of things could

578
00:28:31,240 --> 00:28:35,080
Speaker 2: do that, Like we actually have discovered planets orbiting pulsars

579
00:28:35,440 --> 00:28:37,840
Speaker 2: by how that planet has tugged on the pulsar and

580
00:28:38,000 --> 00:28:40,040
Speaker 2: changed that series of blips. But what we're looking for

581
00:28:40,160 --> 00:28:44,480
Speaker 2: here are correlations among many, many pulsars. So they're looking

582
00:28:44,520 --> 00:28:46,600
Speaker 2: through the sky for lots and lots of these examples,

583
00:28:46,720 --> 00:28:48,880
Speaker 2: and they want to see an overall effect where a

584
00:28:48,920 --> 00:28:51,160
Speaker 2: bunch of pulsars are squeezed towards us and a bunch

585
00:28:51,200 --> 00:28:54,760
Speaker 2: are squeezed away from us. And there's very specific predictions

586
00:28:55,040 --> 00:28:58,280
Speaker 2: made by two physicists Hellings and Downs, that predicts a

587
00:28:58,400 --> 00:29:01,640
Speaker 2: very particular kind of sh shift in the pattern of

588
00:29:01,760 --> 00:29:04,800
Speaker 2: pulsars that would come from gravitational waves, and that's what

589
00:29:04,960 --> 00:29:06,840
Speaker 2: NANOGrav and the other arrays are looking for.

590
00:29:07,160 --> 00:29:09,320
Speaker 1: MM So, I think you're saying, like, if you look

591
00:29:09,360 --> 00:29:11,560
Speaker 1: out to a whole bunch of pulsars out there in

592
00:29:11,600 --> 00:29:14,160
Speaker 1: the night sky and you see sort of a ripple

593
00:29:14,280 --> 00:29:17,320
Speaker 1: go through all of these different frequencies of light that

594
00:29:17,360 --> 00:29:19,480
Speaker 1: you're getting from these pulsars, then you know that maybe

595
00:29:19,520 --> 00:29:23,400
Speaker 1: a gravitational wave kind of spread out there in space exactly.

596
00:29:23,520 --> 00:29:26,320
Speaker 2: And these could be gravitational waves from like the mergers

597
00:29:26,400 --> 00:29:29,880
Speaker 2: of supermassive black holes, things that could have been washing

598
00:29:30,000 --> 00:29:33,240
Speaker 2: over us basically our entire existence. But we could not

599
00:29:33,360 --> 00:29:36,640
Speaker 2: detect that even ligo and virgo could not see. So

600
00:29:36,840 --> 00:29:39,160
Speaker 2: this is like opening a new kind of eyeball to

601
00:29:39,240 --> 00:29:42,440
Speaker 2: a new kind of frequency of gravitational wave nobody's seen before,

602
00:29:42,800 --> 00:29:46,320
Speaker 2: from a different kind of source that nobody's heard from before.

603
00:29:46,560 --> 00:29:49,320
Speaker 1: That's pretty cool. And so I guess how many pulsars

604
00:29:49,360 --> 00:29:52,360
Speaker 1: did NANOGrav look at for this latest set of results.

605
00:29:52,440 --> 00:29:55,360
Speaker 2: So nanograph has been looking at sixty eight pulsars and

606
00:29:55,440 --> 00:29:59,080
Speaker 2: studying them for fifteen years. So that's a good amount

607
00:29:59,080 --> 00:30:02,240
Speaker 2: of data. As you say, they're using existing facilities, but

608
00:30:02,320 --> 00:30:05,160
Speaker 2: they still have to like occupy time on those facilities.

609
00:30:05,200 --> 00:30:08,160
Speaker 2: They're not general purpose telescopes that listen to the whole sky.

610
00:30:08,560 --> 00:30:11,200
Speaker 2: Got to like point the Green Bank telescope at the

611
00:30:11,280 --> 00:30:13,440
Speaker 2: right part of the sky to listen to a pulsar.

612
00:30:13,960 --> 00:30:15,840
Speaker 2: So it has taken a significant amount of our sort

613
00:30:15,840 --> 00:30:19,280
Speaker 2: of astronomical resources that we could have spent listening to

614
00:30:19,440 --> 00:30:19,960
Speaker 2: other stuff.

615
00:30:20,200 --> 00:30:22,040
Speaker 1: Oh you mean, like we don't listen to all sixty

616
00:30:22,080 --> 00:30:24,120
Speaker 1: eight pulsars at the same time. We have to kind

617
00:30:24,160 --> 00:30:27,040
Speaker 1: of go through them one by one mm hmm, yeah, exactly.

618
00:30:27,360 --> 00:30:30,040
Speaker 1: And so you're pointing all your telescopes to the first pulsar,

619
00:30:30,280 --> 00:30:33,000
Speaker 1: measuring its frequency, going to the next one, going to

620
00:30:33,080 --> 00:30:35,400
Speaker 1: the next one, sixty eight of those, and then you,

621
00:30:35,680 --> 00:30:38,120
Speaker 1: I guess you cycle back around and you start with

622
00:30:38,200 --> 00:30:39,640
Speaker 1: the first one again, and you do that for a

623
00:30:39,680 --> 00:30:40,080
Speaker 1: long time.

624
00:30:40,240 --> 00:30:42,440
Speaker 2: Yeah, you need lots of hours, and they observe each

625
00:30:42,520 --> 00:30:45,440
Speaker 2: one monthly, so they know roughly the pattern of these

626
00:30:45,520 --> 00:30:48,120
Speaker 2: things and they sort of cycle through them. And these

627
00:30:48,120 --> 00:30:50,880
Speaker 2: pulsars are very faint, so you can't always hear them

628
00:30:50,960 --> 00:30:52,960
Speaker 2: very well, So you need lots of hours to sort

629
00:30:52,960 --> 00:30:55,160
Speaker 2: of like light these up in NANOGrav Even though it's

630
00:30:55,200 --> 00:30:57,720
Speaker 2: trying to use the whole galaxy as an observatory, it's

631
00:30:57,760 --> 00:30:59,960
Speaker 2: only still really sensitive to the ones within a few

632
00:31:00,320 --> 00:31:04,000
Speaker 2: thousand light years of Earth because the limitations just of

633
00:31:04,120 --> 00:31:06,880
Speaker 2: like hearing these things, they're very faint sources.

634
00:31:08,400 --> 00:31:10,000
Speaker 1: And I think you have to do it for a

635
00:31:10,080 --> 00:31:13,720
Speaker 1: long time, like you said, because these waves are so slow, right,

636
00:31:14,440 --> 00:31:18,280
Speaker 1: like you said, they have a period of maybe thirty years, fifteen.

637
00:31:18,040 --> 00:31:21,600
Speaker 2: Years, thirty years, yeah, exactly, And so these are very

638
00:31:21,680 --> 00:31:24,720
Speaker 2: slow moving things, and so to see slow moving things,

639
00:31:24,760 --> 00:31:27,200
Speaker 2: you need data over a large period of time. It's

640
00:31:27,240 --> 00:31:30,320
Speaker 2: hard to measure slow effects over a very short time period.

641
00:31:30,440 --> 00:31:33,040
Speaker 2: The longer your lever arm in time, the better you're

642
00:31:33,080 --> 00:31:35,840
Speaker 2: able to see effects that are very slow.

643
00:31:36,480 --> 00:31:40,880
Speaker 1: And so specifically things that would give gravitational ways that

644
00:31:41,000 --> 00:31:43,960
Speaker 1: are so big and so slow thirty year period. Those

645
00:31:43,960 --> 00:31:46,280
Speaker 1: are very special events in the universe, right like, they

646
00:31:46,320 --> 00:31:48,360
Speaker 1: don't just happen all the time, or maybe they do.

647
00:31:48,480 --> 00:31:49,560
Speaker 1: I guess that's part of the question.

648
00:31:50,200 --> 00:31:51,959
Speaker 2: They don't just happen all the time, but they are

649
00:31:52,160 --> 00:31:55,360
Speaker 2: very slow events. So when you have like two galaxies

650
00:31:55,440 --> 00:31:58,160
Speaker 2: merging and then they each have like a super massive

651
00:31:58,240 --> 00:32:01,480
Speaker 2: black hole that's like millions to up to ten billion

652
00:32:01,560 --> 00:32:05,440
Speaker 2: solar masses, they don't merge instantaneously. They dance around each

653
00:32:05,440 --> 00:32:08,760
Speaker 2: other for like you know, sometimes twenty five million years

654
00:32:08,960 --> 00:32:12,560
Speaker 2: before they actually coalesce, which means these things are generating

655
00:32:12,640 --> 00:32:15,880
Speaker 2: gravitational waves for twenty five million years. And so while

656
00:32:15,920 --> 00:32:19,880
Speaker 2: galaxy mergers aren't happening all the time nearby, their radiation

657
00:32:20,080 --> 00:32:21,560
Speaker 2: does last for a long time.

658
00:32:21,800 --> 00:32:24,160
Speaker 1: And so just like LAGOA, I guess we're looking for

659
00:32:24,560 --> 00:32:28,320
Speaker 1: the moment where these black holes are right before they

660
00:32:28,360 --> 00:32:31,440
Speaker 1: smush together, right like, because that's when they spin around

661
00:32:31,480 --> 00:32:33,640
Speaker 1: each other super duper fast and cause big waves and

662
00:32:33,680 --> 00:32:36,080
Speaker 1: the gravitational fabric of space and time.

663
00:32:36,200 --> 00:32:38,800
Speaker 2: Yeah, but NANOGrav is sentenced to them well before they

664
00:32:38,960 --> 00:32:41,480
Speaker 2: actually hit each other, so we can listen to almost

665
00:32:41,520 --> 00:32:43,640
Speaker 2: any part of that and the current results from NANOGrav

666
00:32:43,720 --> 00:32:47,160
Speaker 2: they do see these galaxy size gravitational waves, but they

667
00:32:47,240 --> 00:32:51,480
Speaker 2: can't pinpoint individual collisions. It's sort of an incoherent superposition

668
00:32:51,880 --> 00:32:55,440
Speaker 2: of mergers all over the nearby part of the universe.

669
00:32:56,160 --> 00:32:59,280
Speaker 1: I imagine it's hard because these polsers are different distances

670
00:32:59,360 --> 00:33:01,920
Speaker 1: from us, right, So, like some of them are maybe

671
00:33:01,960 --> 00:33:05,240
Speaker 1: one hundred thousand or I don't know, fifty thousand light

672
00:33:05,320 --> 00:33:07,120
Speaker 1: years from us, and so like the data you get

673
00:33:07,160 --> 00:33:09,360
Speaker 1: from them, they come from kind of different times in

674
00:33:09,440 --> 00:33:10,320
Speaker 1: the universe, don't they.

675
00:33:10,640 --> 00:33:13,040
Speaker 2: Yeah, that's right. All the pulsars that we're looking at

676
00:33:13,080 --> 00:33:15,200
Speaker 2: are a few thousand light years from Earth. But they

677
00:33:15,240 --> 00:33:17,760
Speaker 2: definitely take this into account. But again, the events we're

678
00:33:17,760 --> 00:33:19,560
Speaker 2: looking at are very very slow.

679
00:33:19,480 --> 00:33:22,960
Speaker 1: Moving, meaning like maybe there's our two super massive black

680
00:33:23,000 --> 00:33:24,960
Speaker 1: holes merging somewhere in the universe, but they've been doing

681
00:33:25,000 --> 00:33:27,920
Speaker 1: it for you know, thousands and thousands of years, and

682
00:33:28,040 --> 00:33:31,040
Speaker 1: so if you detect all of your pulsars kind of

683
00:33:31,240 --> 00:33:34,880
Speaker 1: wiggling at the same frequency, maybe they come from the

684
00:33:34,960 --> 00:33:36,600
Speaker 1: same event exactly.

685
00:33:36,840 --> 00:33:40,320
Speaker 2: But again, nanograph can't pinpoint individual events, not yet. At

686
00:33:40,400 --> 00:33:43,720
Speaker 2: least what they see so far is totally consistent with

687
00:33:44,000 --> 00:33:47,520
Speaker 2: a lot of gravitational waves adding up from lots of

688
00:33:47,560 --> 00:33:49,120
Speaker 2: supermassive black holes merging.

689
00:33:49,320 --> 00:33:51,880
Speaker 1: Cool. Well, Daniel, you got to interview one of the

690
00:33:51,920 --> 00:33:56,400
Speaker 1: scientists that works on this nanograph collaboration, Professor Kiaramingarelli, and

691
00:33:56,600 --> 00:33:58,080
Speaker 1: so you have an interview with Earth.

692
00:33:58,360 --> 00:34:00,520
Speaker 2: That's right. I had a lot of fun chatting with Cool.

693
00:34:00,560 --> 00:34:03,520
Speaker 1: So when we come back, Daniel, we'll interview Professor Kara Mingarelli,

694
00:34:03,760 --> 00:34:06,280
Speaker 1: who's part of the nanograph collaboration, and she'll talk about

695
00:34:06,400 --> 00:34:09,239
Speaker 1: some of the results and what that means for her

696
00:34:09,440 --> 00:34:11,200
Speaker 1: and for the scientists that worked on it, and what

697
00:34:11,320 --> 00:34:13,839
Speaker 1: that means for our knowledge of the universe. But first,

698
00:34:13,920 --> 00:34:28,839
Speaker 1: let's take another quick break. All right, we're talking about

699
00:34:28,840 --> 00:34:32,200
Speaker 1: the nanograph results unveiled this week, which are big news

700
00:34:32,400 --> 00:34:35,239
Speaker 1: because I guess it, let's us see another part of

701
00:34:35,280 --> 00:34:37,399
Speaker 1: the universe we couldn't see before, right.

702
00:34:37,560 --> 00:34:39,640
Speaker 2: That's right. It let us listen to things going on

703
00:34:39,800 --> 00:34:43,800
Speaker 2: out there that we couldn't hear before, specifically the mergers

704
00:34:43,880 --> 00:34:46,840
Speaker 2: of super massive black holes, which are already things we

705
00:34:46,920 --> 00:34:48,399
Speaker 2: don't understand very well.

706
00:34:48,680 --> 00:34:50,440
Speaker 1: Yeah, I mean I think they're tied even to like

707
00:34:50,560 --> 00:34:53,600
Speaker 1: the mystery of how galaxies form, right, because we sort

708
00:34:53,600 --> 00:34:55,120
Speaker 1: of are not sure about that, right.

709
00:34:55,400 --> 00:34:58,160
Speaker 2: We definitely don't understand how galaxies form and how they

710
00:34:58,280 --> 00:35:01,319
Speaker 2: get these super massive black holes and why there are

711
00:35:01,440 --> 00:35:03,239
Speaker 2: so many of them. The black holes at the hearts

712
00:35:03,280 --> 00:35:06,480
Speaker 2: of galaxies are bigger than anybody expects, and they're everywhere,

713
00:35:06,520 --> 00:35:10,000
Speaker 2: and they formed earlier in the universe. Then we understand.

714
00:35:10,360 --> 00:35:12,040
Speaker 1: Cool. And so you talked to one of those scientists

715
00:35:12,080 --> 00:35:13,640
Speaker 1: that worked on this. How excited was she?

716
00:35:13,920 --> 00:35:16,600
Speaker 2: She was very excited. She had met her entire career

717
00:35:16,680 --> 00:35:19,600
Speaker 2: since she was a graduate student on this project, and

718
00:35:19,920 --> 00:35:21,440
Speaker 2: now she's getting the payoff.

719
00:35:21,760 --> 00:35:25,880
Speaker 1: Awesome. Well, here is Daniel's interview with Professor Kiera Mingarelli

720
00:35:26,160 --> 00:35:28,480
Speaker 1: from You and the NANOGrav experiment.

721
00:35:36,800 --> 00:35:39,320
Speaker 2: All right, so then it's my great pleasure to welcome

722
00:35:39,320 --> 00:35:43,520
Speaker 2: to our program professor Kiera Mongarelli, professor at Yale who

723
00:35:43,600 --> 00:35:46,919
Speaker 2: works on NANOGrav. Kierra, thank you very much for joining

724
00:35:47,000 --> 00:35:47,359
Speaker 2: us today.

725
00:35:47,560 --> 00:35:49,279
Speaker 3: Thank you so much. I'm so happy to be here.

726
00:35:49,640 --> 00:35:53,600
Speaker 2: So tell me first, what is the basic idea of NANOGrav?

727
00:35:54,000 --> 00:35:58,640
Speaker 2: How does keeping track of pulsars help you spot gravitational waves.

728
00:35:58,960 --> 00:36:04,239
Speaker 3: So NANOGrav uses the galactic population of millisecond pulsars to

729
00:36:04,320 --> 00:36:08,520
Speaker 3: look for gravitational waves. We can do this because millisecond

730
00:36:08,560 --> 00:36:13,640
Speaker 3: pulsars are nature's best clocks. So they spin around about

731
00:36:13,680 --> 00:36:16,839
Speaker 3: one hundred times a second. Their masses are maybe one

732
00:36:16,920 --> 00:36:19,080
Speaker 3: and a half times the mass of the Sun, and

733
00:36:19,200 --> 00:36:22,320
Speaker 3: they would fit inside Manhattan. So if you can imagine

734
00:36:22,360 --> 00:36:25,719
Speaker 3: taking the Sun, shrinking it to the size of Manhattan

735
00:36:25,800 --> 00:36:29,320
Speaker 3: and putting it in a blunder, that is a millisecond pulsar.

736
00:36:30,080 --> 00:36:32,359
Speaker 3: And there are ticks when they arrive at the Earth.

737
00:36:32,400 --> 00:36:35,080
Speaker 3: So every time they spin around, they send a flash

738
00:36:35,120 --> 00:36:38,759
Speaker 3: of radio waves to the Earth. And those flashes are

739
00:36:39,120 --> 00:36:42,400
Speaker 3: so precise that we can time them to hundreds of

740
00:36:42,480 --> 00:36:47,200
Speaker 3: nanoseconds over a decade, so they are very very stable clocks.

741
00:36:47,880 --> 00:36:51,680
Speaker 3: That point is really important because gravitational waves change the

742
00:36:51,800 --> 00:36:56,960
Speaker 3: distances between objects, and so as a gravitational wave transits

743
00:36:57,000 --> 00:37:00,279
Speaker 3: the galaxy, it will change the distance between the Earth

744
00:37:00,320 --> 00:37:03,920
Speaker 3: and the pulsar. And so now those super stable radio

745
00:37:04,000 --> 00:37:07,920
Speaker 3: flashes arrive early, and then they arrive late as the

746
00:37:08,000 --> 00:37:11,520
Speaker 3: gravitational wave transits through the galaxy, so a little bit

747
00:37:11,560 --> 00:37:13,520
Speaker 3: early and then a little bit late, and then a

748
00:37:13,560 --> 00:37:16,640
Speaker 3: little bit early again. And so what we look for

749
00:37:17,040 --> 00:37:20,240
Speaker 3: are those changes and the arrival times of the pulses

750
00:37:20,400 --> 00:37:23,520
Speaker 3: from these ultra stable pulsars. That's how we can turn

751
00:37:23,600 --> 00:37:26,680
Speaker 3: the whole galaxy into a gravitational wave detector.

752
00:37:26,920 --> 00:37:29,319
Speaker 2: Awesome, Well, it sounds great in principle, but I'm sure

753
00:37:29,360 --> 00:37:31,680
Speaker 2: in practice there are a lot of things to get right,

754
00:37:32,000 --> 00:37:35,040
Speaker 2: what kind of like technical and data analysis challenges that

755
00:37:35,160 --> 00:37:37,759
Speaker 2: you have to overcome to make this crazy idea work.

756
00:37:37,920 --> 00:37:40,600
Speaker 3: So it's taken a lot of people a lot of

757
00:37:40,719 --> 00:37:43,320
Speaker 3: time to overcome all those challenges. In fact, we have

758
00:37:43,440 --> 00:37:45,320
Speaker 3: some of the best people in the world working on

759
00:37:45,840 --> 00:37:49,920
Speaker 3: the data analysis and the noise models, because you're right,

760
00:37:50,120 --> 00:37:53,080
Speaker 3: there's a lot of noise involved here. We can't walk

761
00:37:53,160 --> 00:37:55,279
Speaker 3: over to our pulsars and turn them on and off

762
00:37:55,320 --> 00:37:58,360
Speaker 3: again because we think something funny happened. Right. One of

763
00:37:58,400 --> 00:38:01,120
Speaker 3: the big challenges that we have is the interstellar medium,

764
00:38:01,520 --> 00:38:05,080
Speaker 3: so the gas and dust between us and the pulsars.

765
00:38:05,560 --> 00:38:09,440
Speaker 3: There are some maps of that that they're all very approximate,

766
00:38:10,000 --> 00:38:13,920
Speaker 3: and this affects our signals because the radio wation the

767
00:38:14,000 --> 00:38:18,040
Speaker 3: pulses are dispersed by the interstellar medium, and that happens

768
00:38:18,080 --> 00:38:21,840
Speaker 3: at different frequencies radio frequencies, and so we have to

769
00:38:21,920 --> 00:38:24,719
Speaker 3: take this signal that's then been spread out by the

770
00:38:24,760 --> 00:38:29,360
Speaker 3: interstellar medium and d disperse it to make it a

771
00:38:29,520 --> 00:38:33,160
Speaker 3: very clean signal again, and so that can add some

772
00:38:33,400 --> 00:38:37,960
Speaker 3: noise to what we're looking for. And unfortunately that noise

773
00:38:38,280 --> 00:38:42,480
Speaker 3: looks very similar to the gravitational wave signal that we're

774
00:38:42,520 --> 00:38:46,040
Speaker 3: looking for. So we have to be very very careful

775
00:38:46,520 --> 00:38:49,800
Speaker 3: when we're making these noise models for the pulsars that

776
00:38:50,280 --> 00:38:52,880
Speaker 3: we're not going one way or the other. That is

777
00:38:52,960 --> 00:38:56,320
Speaker 3: to say that we're not taking a gravitational wave signal

778
00:38:56,400 --> 00:38:59,239
Speaker 3: and thinking that it's just noise in our pulsar because

779
00:38:59,280 --> 00:39:03,040
Speaker 3: they look so sim and therefore taking the signal away

780
00:39:03,320 --> 00:39:06,480
Speaker 3: from any possible detection. And at the same time, we

781
00:39:06,560 --> 00:39:08,600
Speaker 3: need to make sure that our signal models are good

782
00:39:08,719 --> 00:39:13,840
Speaker 3: enough that we don't mistake some noise for a possible signal.

783
00:39:14,200 --> 00:39:18,000
Speaker 3: And so this right now is really really important. Getting

784
00:39:18,080 --> 00:39:22,239
Speaker 3: those individual noise models correct for the pulsars is really

785
00:39:23,160 --> 00:39:23,920
Speaker 3: really important.

786
00:39:24,120 --> 00:39:26,680
Speaker 2: So how do you distinguish between them? How do you

787
00:39:26,800 --> 00:39:28,200
Speaker 2: know you're getting the noise right?

788
00:39:28,560 --> 00:39:32,680
Speaker 3: So we can distinguish between the signal and the noise

789
00:39:32,960 --> 00:39:37,080
Speaker 3: in a few ways. Number One, the gravitational wave background

790
00:39:37,520 --> 00:39:41,520
Speaker 3: has some characteristic amplitude, and that's a function of the

791
00:39:41,640 --> 00:39:45,520
Speaker 3: astrophysics of the source that's creating the signal. So if,

792
00:39:45,680 --> 00:39:49,040
Speaker 3: for example, it's super massive black holes, and we'll probably

793
00:39:49,080 --> 00:39:51,440
Speaker 3: get to that in a second, but if, for example,

794
00:39:51,520 --> 00:39:55,200
Speaker 3: it's that that's creating the signal, then the amplitude of

795
00:39:55,239 --> 00:39:58,600
Speaker 3: the signal is based on the astrophysics that governs their mergers.

796
00:39:58,920 --> 00:40:03,480
Speaker 3: So of are the black holes, what gravitational wave frequency

797
00:40:03,560 --> 00:40:06,400
Speaker 3: are they emitting at, how far away are they How

798
00:40:06,520 --> 00:40:10,600
Speaker 3: many super massive black holes are there per unit rendshift?

799
00:40:10,800 --> 00:40:14,200
Speaker 3: So what's the density of black holes in the universe.

800
00:40:14,760 --> 00:40:19,680
Speaker 3: And we know that that amplitude has a predicted and

801
00:40:19,880 --> 00:40:23,480
Speaker 3: characteristic way of varying as a function of frequency. So

802
00:40:23,600 --> 00:40:28,680
Speaker 3: we have lots of different frequency detector bins in our experiment,

803
00:40:29,160 --> 00:40:31,440
Speaker 3: and we know exactly how much signal should be in

804
00:40:31,480 --> 00:40:33,800
Speaker 3: each one of those bins from our simulations, and we

805
00:40:33,880 --> 00:40:37,160
Speaker 3: can measure what's there and the way that the signal

806
00:40:37,280 --> 00:40:41,640
Speaker 3: is distributed in those bins can be characteristic of, for example,

807
00:40:42,040 --> 00:40:45,799
Speaker 3: super massive black hole binaries generating the background. So that's

808
00:40:45,920 --> 00:40:50,160
Speaker 3: one part of the puzzle. The second part is something

809
00:40:50,239 --> 00:40:53,879
Speaker 3: called the Hellings and Downs curve. And so, back when

810
00:40:53,920 --> 00:40:56,759
Speaker 3: people were thinking in the eighties about how do we

811
00:40:57,600 --> 00:41:01,200
Speaker 3: actually go about detecting a gravitational wave back, the zero

812
00:41:01,280 --> 00:41:03,239
Speaker 3: thworter thing to do, and I think a lot of

813
00:41:03,320 --> 00:41:06,000
Speaker 3: us that have done undergraduate degrees in STEM fields have done,

814
00:41:06,400 --> 00:41:09,239
Speaker 3: is a cross correlation analysis, where you say, all right,

815
00:41:09,280 --> 00:41:12,680
Speaker 3: there's one signal in my data, So I'm going to

816
00:41:12,800 --> 00:41:14,840
Speaker 3: take all of these different pieces of data and like

817
00:41:15,120 --> 00:41:18,200
Speaker 3: bash them together and see what signal is present in

818
00:41:18,400 --> 00:41:21,960
Speaker 3: all of my different pieces of data. And so that's

819
00:41:22,000 --> 00:41:23,960
Speaker 3: what we do with pulsar timing. We take all of

820
00:41:24,040 --> 00:41:27,520
Speaker 3: these different timestamps from pulsars and cross correlate them, and

821
00:41:27,600 --> 00:41:30,520
Speaker 3: we look for the gravitational wave background signal. What's really

822
00:41:30,640 --> 00:41:33,400
Speaker 3: interesting is that not only do you get this amplitude

823
00:41:33,760 --> 00:41:37,120
Speaker 3: of the gravitational wave background that's correlated, but there's an

824
00:41:37,160 --> 00:41:42,520
Speaker 3: additional geometric piece predicted by general relativity, and that additional

825
00:41:42,600 --> 00:41:46,680
Speaker 3: cross correlation term varies as a function of angle between

826
00:41:46,719 --> 00:41:50,160
Speaker 3: the pulsars, and so if pulsars are close together, they

827
00:41:50,239 --> 00:41:54,040
Speaker 3: have a stronger correlation, a stronger response to the gravitational

828
00:41:54,040 --> 00:41:56,440
Speaker 3: way background. If they're a little bit further away, it

829
00:41:56,480 --> 00:42:02,200
Speaker 3: gets weaker. But then interestingly, because gravitational have this quadrupolar shape,

830
00:42:02,239 --> 00:42:06,480
Speaker 3: which is like a cosine sort of shape, the signal

831
00:42:06,560 --> 00:42:10,759
Speaker 3: increases again right as they get further apart. And so

832
00:42:11,120 --> 00:42:14,319
Speaker 3: to create a signal that looks like that, that kind

833
00:42:14,360 --> 00:42:18,719
Speaker 3: of cosine style shape in addition to an amplitude, which

834
00:42:18,760 --> 00:42:22,839
Speaker 3: is predicted by all of our simulations, that's impossible to fake.

835
00:42:23,440 --> 00:42:26,399
Speaker 3: And that's what we've seen now in the nanograph data.

836
00:42:26,680 --> 00:42:30,279
Speaker 3: So previously we'd seen evidence for this amplitude and it

837
00:42:30,440 --> 00:42:33,960
Speaker 3: was so loud we where were scratching our heads for

838
00:42:34,120 --> 00:42:37,080
Speaker 3: a hot second being like can this be real or

839
00:42:37,200 --> 00:42:39,640
Speaker 3: is this just noise? Right? And we had to wait

840
00:42:39,800 --> 00:42:43,160
Speaker 3: until we had this distinctive Hellings and Downs curve, until

841
00:42:43,200 --> 00:42:46,680
Speaker 3: we had evidence for that as well, because nothing can

842
00:42:46,760 --> 00:42:50,279
Speaker 3: fake the Hellings in Downs curve the noise. You know,

843
00:42:50,520 --> 00:42:53,480
Speaker 3: there could be unknown unknowns that just happened to be

844
00:42:53,640 --> 00:42:56,960
Speaker 3: generating some sort of correlated noise and all of the

845
00:42:57,040 --> 00:42:59,600
Speaker 3: pulsar signals we don't know, but we do know for

846
00:42:59,719 --> 00:43:05,120
Speaker 3: sure that this distinctive quadrupolar shape that's the result of

847
00:43:05,200 --> 00:43:07,640
Speaker 3: this sellings and downce curve can't be faked. So having

848
00:43:07,680 --> 00:43:09,960
Speaker 3: those two things at the same time makes us very

849
00:43:10,080 --> 00:43:12,840
Speaker 3: confident that what we're seeing now is evidence for the

850
00:43:12,880 --> 00:43:14,200
Speaker 3: gravitational wave background.

851
00:43:14,440 --> 00:43:16,720
Speaker 2: Do you feel like you have to be extra careful

852
00:43:16,840 --> 00:43:19,600
Speaker 2: about these claims in the wake of the BICEP two debacle.

853
00:43:20,000 --> 00:43:24,839
Speaker 3: Extraordinary claims require extraordinary evidence, And I feel like as

854
00:43:24,880 --> 00:43:27,279
Speaker 3: a collaboration, we've done a really great job at being

855
00:43:27,480 --> 00:43:31,279
Speaker 3: very conservative. When we first found the hint that what

856
00:43:31,360 --> 00:43:33,840
Speaker 3: we were seeing was a gravitational wave background back in

857
00:43:33,920 --> 00:43:37,279
Speaker 3: twenty twenty, we were very careful to say that this

858
00:43:37,400 --> 00:43:40,040
Speaker 3: could be the first part of the signal, but we're

859
00:43:40,080 --> 00:43:43,719
Speaker 3: certainly not saying that we've seen the whole signal, and

860
00:43:43,800 --> 00:43:46,279
Speaker 3: this is certainly not any kind of evidence for the

861
00:43:46,320 --> 00:43:50,120
Speaker 3: gravitationalive background, but heck, it's sure interesting, and we're going

862
00:43:50,200 --> 00:43:52,239
Speaker 3: to keep timing the data and we'll let you know

863
00:43:52,360 --> 00:43:56,880
Speaker 3: when something cool happens. So another part of, you know,

864
00:43:57,000 --> 00:43:59,400
Speaker 3: why we're so confident that this is evidence for the

865
00:43:59,440 --> 00:44:04,720
Speaker 3: gravitation background is that not only have we seen this signal,

866
00:44:05,280 --> 00:44:08,480
Speaker 3: but so have the Europeans. So in Europe they have

867
00:44:08,600 --> 00:44:11,840
Speaker 3: their own pulsar timing array and in Australia they have

868
00:44:11,960 --> 00:44:14,719
Speaker 3: a pulsar timing array, and in India they have a

869
00:44:14,800 --> 00:44:19,720
Speaker 3: pulsar timing array, and so far we've all been seeing

870
00:44:19,960 --> 00:44:23,680
Speaker 3: consistent signals the O. There's different levels of evidence for

871
00:44:23,760 --> 00:44:26,600
Speaker 3: the signal depending on the data set. But these data

872
00:44:26,640 --> 00:44:30,200
Speaker 3: sets are all different, they have different systematics, they're taken

873
00:44:31,000 --> 00:44:35,040
Speaker 3: with different telescopes. We use some similar analysis tools that

874
00:44:35,480 --> 00:44:39,880
Speaker 3: we're now even having independent analysis tools for the pulsars,

875
00:44:40,120 --> 00:44:44,719
Speaker 3: and so this makes us all very confident that what

876
00:44:44,840 --> 00:44:46,120
Speaker 3: we're seeing has to be real.

877
00:44:46,640 --> 00:44:49,600
Speaker 2: So why did you choose this as your particular slice

878
00:44:49,960 --> 00:44:53,280
Speaker 2: of physics to pursue? Doesn't it seem quite a risky

879
00:44:53,400 --> 00:44:54,600
Speaker 2: bet for a young researcher.

880
00:44:54,960 --> 00:44:57,320
Speaker 3: Oh yes, when I was even younger, I had a

881
00:44:57,360 --> 00:44:59,759
Speaker 3: lot of professors tell me why I was wasting my

882
00:45:00,080 --> 00:45:03,840
Speaker 3: I'm looking for low frequency gravitational waves. And even you know,

883
00:45:04,000 --> 00:45:08,719
Speaker 3: I've been doing this work since twenty ten, that's when

884
00:45:08,719 --> 00:45:11,680
Speaker 3: I started working on pulsar timing rays and graduate school,

885
00:45:11,920 --> 00:45:14,760
Speaker 3: and you know, even then working on LIGO was risky.

886
00:45:14,920 --> 00:45:18,440
Speaker 3: I in fact started my life as a ligone and

887
00:45:18,640 --> 00:45:22,160
Speaker 3: did a lot of work in helping to develop something

888
00:45:22,480 --> 00:45:28,600
Speaker 3: called LOO, and that was terrible for me and my

889
00:45:28,800 --> 00:45:32,960
Speaker 3: professor at the University of Birmingham, my supervisor, Alberto Vecchio,

890
00:45:33,080 --> 00:45:35,040
Speaker 3: was like, well, maybe you want to do something with

891
00:45:35,400 --> 00:45:38,320
Speaker 3: pulsar timing arrays and I was like, oh, I don't know,

892
00:45:38,440 --> 00:45:41,520
Speaker 3: let's think about it. So the idea of a pulsar

893
00:45:41,640 --> 00:45:46,440
Speaker 3: timing array, of having nature create a gravitational wave detector

894
00:45:46,560 --> 00:45:48,880
Speaker 3: for you, if you're just clever enough to use it,

895
00:45:49,880 --> 00:45:53,840
Speaker 3: really blew my mind. It was such a beautiful idea

896
00:45:54,200 --> 00:45:56,680
Speaker 3: that I thought, you know, this is really the experiment

897
00:45:56,840 --> 00:45:59,279
Speaker 3: for me. And I also felt like at the time

898
00:46:00,120 --> 00:46:03,719
Speaker 3: that it was risky to join a collaboration that had

899
00:46:03,760 --> 00:46:07,320
Speaker 3: a lot of the theoretical predictions already in place, and

900
00:46:07,640 --> 00:46:12,279
Speaker 3: at the time pulsear timing arrays didn't have some of

901
00:46:12,360 --> 00:46:16,480
Speaker 3: the fundamental papers that have now been written that I've

902
00:46:16,520 --> 00:46:18,680
Speaker 3: helped to write, and so I felt like it was

903
00:46:19,040 --> 00:46:21,440
Speaker 3: maybe less of a risk or I don't know, it

904
00:46:21,520 --> 00:46:23,520
Speaker 3: depends on how you look at it. It was risky

905
00:46:23,640 --> 00:46:26,239
Speaker 3: for sure to go into a field when it was

906
00:46:26,800 --> 00:46:30,359
Speaker 3: very exotic, even compared to ligo, which at the time

907
00:46:30,520 --> 00:46:35,440
Speaker 3: was also exotic, right, So it was writing down the equations,

908
00:46:35,520 --> 00:46:38,120
Speaker 3: trusting that the math was right and then just kind

909
00:46:38,160 --> 00:46:41,200
Speaker 3: of looking at nature hoping that the merger rates would comply,

910
00:46:41,880 --> 00:46:44,319
Speaker 3: because there's really nothing you can do, Like, even if

911
00:46:44,360 --> 00:46:47,200
Speaker 3: you have the perfect instrument, if super massive black holes

912
00:46:47,280 --> 00:46:50,400
Speaker 3: never merge, you're not going to find a signal. Right,

913
00:46:50,920 --> 00:46:53,839
Speaker 3: So you're right. It was risky, and I had several

914
00:46:53,880 --> 00:46:56,480
Speaker 3: people tell me that I should absolutely not be doing this,

915
00:46:56,760 --> 00:47:00,080
Speaker 3: that it should definitely not be my photos. But I

916
00:47:00,120 --> 00:47:02,480
Speaker 3: mean it was good advice at the time, right that

917
00:47:02,840 --> 00:47:05,200
Speaker 3: if you're a stake in your career on something that

918
00:47:05,719 --> 00:47:09,000
Speaker 3: isn't a proven technology yet, it's a big risk.

919
00:47:09,440 --> 00:47:11,680
Speaker 2: I love the idea that we build a new kind

920
00:47:11,680 --> 00:47:13,840
Speaker 2: of eyeball and we use it to look on to

921
00:47:13,920 --> 00:47:15,960
Speaker 2: the universe, but we don't know what we're going to see.

922
00:47:16,200 --> 00:47:18,640
Speaker 2: And in the case of Ligo and Virgo, they were

923
00:47:18,719 --> 00:47:22,120
Speaker 2: lucky because there's so many more gravitational waves than people

924
00:47:22,160 --> 00:47:26,359
Speaker 2: initially expected. What's the situation here. Are we surprised at

925
00:47:26,400 --> 00:47:29,400
Speaker 2: the sort of amplitude of these gravitational waves? Is it

926
00:47:29,520 --> 00:47:30,720
Speaker 2: more or less than we expected?

927
00:47:31,120 --> 00:47:35,120
Speaker 3: I'm very surprised at the amplitude of the gravitational wave background.

928
00:47:35,360 --> 00:47:39,600
Speaker 3: It is firmly twice as loud as I thought it

929
00:47:39,640 --> 00:47:43,400
Speaker 3: would be from my own models. So that's very surprising

930
00:47:43,480 --> 00:47:48,600
Speaker 3: to me and delightful. I couldn't be happier. Thank you

931
00:47:48,840 --> 00:47:52,719
Speaker 3: universe exactly, Thank your universe for loving super massive black

932
00:47:52,760 --> 00:47:55,120
Speaker 3: holes as much as you love stellar mass black holes.

933
00:47:55,320 --> 00:47:57,720
Speaker 3: But that's assuming that all of this signal is coming

934
00:47:57,840 --> 00:48:02,399
Speaker 3: from these merging super massive black holes. So I guess

935
00:48:02,440 --> 00:48:04,680
Speaker 3: one thing that I haven't said yet is that the

936
00:48:04,800 --> 00:48:09,280
Speaker 3: signal that we found evidence for is this gravitational wave background,

937
00:48:10,040 --> 00:48:13,040
Speaker 3: and that comes from the cosmic merger history of super

938
00:48:13,120 --> 00:48:16,000
Speaker 3: massive black holes. So it's not one signal that we're

939
00:48:16,040 --> 00:48:21,799
Speaker 3: looking for. It's this aggregate signal. It's the incoherent superposition

940
00:48:22,239 --> 00:48:25,680
Speaker 3: of all of the super massive black hole mergers that

941
00:48:25,760 --> 00:48:29,400
Speaker 3: have ever happened. So it's the total opposite of ligo

942
00:48:29,520 --> 00:48:33,120
Speaker 3: in so many ways. It's very low frequency, so frequencies

943
00:48:33,160 --> 00:48:36,960
Speaker 3: of nanohurts, and if you're not used to thinking about nanohurts,

944
00:48:37,560 --> 00:48:41,200
Speaker 3: one nanohertz is like an orbital period of thirty years,

945
00:48:41,640 --> 00:48:45,120
Speaker 3: So these are very slowly orbiting super massive black holes,

946
00:48:45,440 --> 00:48:48,200
Speaker 3: and by super massive, I mean a billion times the

947
00:48:48,320 --> 00:48:51,200
Speaker 3: mass of the Sun. Our signals are also very long lived,

948
00:48:51,440 --> 00:48:54,080
Speaker 3: so one of the reasons that there is this buildup

949
00:48:54,400 --> 00:48:58,120
Speaker 3: of gravitational wave signals at very low frequencies is because

950
00:48:58,160 --> 00:49:01,719
Speaker 3: the black holes evolve soly, their mergers are so slow.

951
00:49:01,800 --> 00:49:05,520
Speaker 3: They take about twenty five million years to merge while

952
00:49:05,560 --> 00:49:11,960
Speaker 3: emitting gravitational waves, and so our signals are rare in

953
00:49:12,120 --> 00:49:16,360
Speaker 3: terms of rates. One super massive black hole binary system

954
00:49:16,880 --> 00:49:20,040
Speaker 3: takes a whole galaxy merger to happen, right, and so

955
00:49:20,160 --> 00:49:23,080
Speaker 3: that's not happening all the time everywhere you look. But

956
00:49:23,200 --> 00:49:27,120
Speaker 3: the merger is so slow, and the signals are so powerful.

957
00:49:27,239 --> 00:49:29,400
Speaker 3: They are a million times stronger than what you can

958
00:49:29,440 --> 00:49:31,839
Speaker 3: see in LEGO. But when they build up, they create

959
00:49:31,920 --> 00:49:35,000
Speaker 3: this wopping loud signal that we can look for with

960
00:49:35,160 --> 00:49:36,280
Speaker 3: pulse our timing arrays.

961
00:49:36,560 --> 00:49:39,040
Speaker 2: So you say there're one million times more powerful than LEGO,

962
00:49:39,440 --> 00:49:41,640
Speaker 2: that's like at their source or to that factor in

963
00:49:41,719 --> 00:49:44,719
Speaker 2: also their relative distance, because they're further away also than

964
00:49:44,800 --> 00:49:45,560
Speaker 2: what LEGO can see.

965
00:49:45,680 --> 00:49:49,680
Speaker 3: Right, So I mean those are slightly different questions. So

966
00:49:49,960 --> 00:49:54,240
Speaker 3: when we talk about gravitational waves, our currency, the measurement

967
00:49:54,320 --> 00:49:56,839
Speaker 3: that we use is the strain and so that's how

968
00:49:56,920 --> 00:50:01,719
Speaker 3: much are the gravitational waves changing space time that you

969
00:50:01,760 --> 00:50:04,960
Speaker 3: can think about that is a distance over distance or

970
00:50:05,120 --> 00:50:07,680
Speaker 3: time over time, because we have space time, so you

971
00:50:07,760 --> 00:50:10,520
Speaker 3: can pick one. So for Ligo, they can look for

972
00:50:10,640 --> 00:50:12,920
Speaker 3: signals that have a strain that has a value of

973
00:50:13,000 --> 00:50:15,000
Speaker 3: ten to the minus twenty one. But what does that mean.

974
00:50:15,400 --> 00:50:17,719
Speaker 3: That's something like that's the fraction of a size of

975
00:50:17,800 --> 00:50:20,719
Speaker 3: a proton over the length of their detector, and I

976
00:50:20,760 --> 00:50:23,319
Speaker 3: think that's the tagline that was very successful for them.

977
00:50:24,239 --> 00:50:27,719
Speaker 3: For us, this is more like one meter per light year.

978
00:50:28,320 --> 00:50:30,920
Speaker 3: But what's a light year. I don't have a physical

979
00:50:31,239 --> 00:50:34,560
Speaker 3: intuition for how long a light year is, and Americans

980
00:50:34,600 --> 00:50:37,520
Speaker 3: are not good with meters, so I think that change

981
00:50:37,560 --> 00:50:41,880
Speaker 3: in time over time is more intuitive. And so for us,

982
00:50:42,040 --> 00:50:43,840
Speaker 3: the strain that we're looking for is ten to the

983
00:50:43,920 --> 00:50:47,000
Speaker 3: minus fifteen. So that's one part in a million billion

984
00:50:47,520 --> 00:50:51,440
Speaker 3: and that's about one hundred nanoseconds over a decade. So

985
00:50:51,560 --> 00:50:55,400
Speaker 3: that's how much the gravitational waves are changing the space

986
00:50:55,480 --> 00:50:59,400
Speaker 3: time fabric around us. And while one part in a

987
00:50:59,480 --> 00:51:03,520
Speaker 3: million bills is incredibly small, it's still a million times

988
00:51:03,640 --> 00:51:06,800
Speaker 3: louder than what Ligo is able to detect.

989
00:51:07,080 --> 00:51:09,880
Speaker 2: I see, yeah, that's the relevant comparison. Very cool, So

990
00:51:10,080 --> 00:51:13,000
Speaker 2: you say that we can see this overall background hum

991
00:51:13,640 --> 00:51:16,920
Speaker 2: and that we attribute it to supermassive black holes. How

992
00:51:16,920 --> 00:51:19,600
Speaker 2: do we know it's not also coming from like primordial

993
00:51:19,719 --> 00:51:23,120
Speaker 2: gravitational waves from before the CMB, etc.

994
00:51:23,600 --> 00:51:27,840
Speaker 3: That's a fantastic question. The answer is that we are

995
00:51:27,960 --> 00:51:31,759
Speaker 3: not sure. In fact, there's a whole paper about, you know,

996
00:51:31,920 --> 00:51:36,080
Speaker 3: exotic physics that we can now constrain with this amplitude

997
00:51:36,120 --> 00:51:39,799
Speaker 3: of the gravitational wave background that we found. So one

998
00:51:39,840 --> 00:51:41,840
Speaker 3: of the things that we'll do in the future is

999
00:51:42,000 --> 00:51:46,160
Speaker 3: to try to characterize the gravitational wave background and to

1000
00:51:46,800 --> 00:51:49,360
Speaker 3: you know, see how does the amplitude vary as a

1001
00:51:49,400 --> 00:51:53,360
Speaker 3: function of frequency. Right now, all of the sources that

1002
00:51:53,440 --> 00:51:57,000
Speaker 3: we know of very in similar ways, right and the

1003
00:51:57,200 --> 00:52:01,160
Speaker 3: error bars will include all of your standard model right. So,

1004
00:52:01,400 --> 00:52:04,640
Speaker 3: right now we have as our key targets. Are the

1005
00:52:04,760 --> 00:52:09,239
Speaker 3: prime suspects for sourcing this gravitation oive background are super

1006
00:52:09,320 --> 00:52:13,520
Speaker 3: massive black holes. First and foremost. You know only the

1007
00:52:13,600 --> 00:52:17,680
Speaker 3: cosmic merger history of super massive black holes of cosmological

1008
00:52:17,840 --> 00:52:21,320
Speaker 3: or primordial gravitational wave background, and that is due to

1009
00:52:22,000 --> 00:52:25,080
Speaker 3: quantum fluctuations in the early universe that were then blown

1010
00:52:25,160 --> 00:52:27,400
Speaker 3: up to the size of the whole universe, and then

1011
00:52:27,600 --> 00:52:30,920
Speaker 3: cosmic strings, which are these defects in the fabric of

1012
00:52:31,040 --> 00:52:35,640
Speaker 3: space time. There's matter density spaghetti in the universe that

1013
00:52:35,719 --> 00:52:40,319
Speaker 3: are vanishingly small that can also create gravitational waves. Now,

1014
00:52:40,440 --> 00:52:44,280
Speaker 3: those three sources might all be contributing to this signal

1015
00:52:44,360 --> 00:52:47,960
Speaker 3: and might help to explain why it's so loud, but

1016
00:52:48,080 --> 00:52:51,759
Speaker 3: it's not necessary to include them. But at the same time,

1017
00:52:52,680 --> 00:52:55,759
Speaker 3: right now, all of the predictions for how the amplitude

1018
00:52:56,239 --> 00:52:59,040
Speaker 3: of the signal varies as a function of frequency, you know,

1019
00:52:59,280 --> 00:53:01,759
Speaker 3: they're all about minus one. They all have like this

1020
00:53:01,920 --> 00:53:06,000
Speaker 3: almost minus one slope, and that means that we won't

1021
00:53:06,120 --> 00:53:08,320
Speaker 3: be able to know for another five years or so

1022
00:53:08,640 --> 00:53:12,680
Speaker 3: as to exactly what's happening and what's sourcing this background,

1023
00:53:12,840 --> 00:53:15,440
Speaker 3: or at least we can say what is the primary

1024
00:53:15,840 --> 00:53:19,160
Speaker 3: source of this background. And that's not even to get

1025
00:53:19,200 --> 00:53:22,040
Speaker 3: into the fact that it's still possible that there might

1026
00:53:22,080 --> 00:53:25,640
Speaker 3: be some noise that's leaking through the pulsars that's masquerading

1027
00:53:25,719 --> 00:53:29,880
Speaker 3: as some background amplitude when it's really noise. We know

1028
00:53:30,080 --> 00:53:32,600
Speaker 3: for sure that there is a background because we can

1029
00:53:32,640 --> 00:53:35,080
Speaker 3: see the hellings and downs curve and nothing else can

1030
00:53:35,160 --> 00:53:37,920
Speaker 3: fake that, so we know that it's not all noise.

1031
00:53:38,280 --> 00:53:41,880
Speaker 3: But we now need to figure out what's sourcing this

1032
00:53:41,960 --> 00:53:47,520
Speaker 3: signal and create, you know, better custom noise models for

1033
00:53:47,600 --> 00:53:50,640
Speaker 3: our pulsars to make sure that we completely the best

1034
00:53:50,680 --> 00:53:54,840
Speaker 3: of our ability understand how the astrophysics of the signals

1035
00:53:54,880 --> 00:53:58,600
Speaker 3: propagating from the pulsar to the Earth will affect things.

1036
00:53:59,000 --> 00:54:01,520
Speaker 2: So then what are the prospects for nanograb you talked

1037
00:54:01,520 --> 00:54:04,680
Speaker 2: about the next five years. Is that gathering more pulsars

1038
00:54:04,800 --> 00:54:07,960
Speaker 2: or more analysis of the data, or combining with the

1039
00:54:08,440 --> 00:54:10,359
Speaker 2: other pulsar timing arrays on Earth.

1040
00:54:10,880 --> 00:54:13,600
Speaker 3: It's all of those things. It's all of those things.

1041
00:54:14,239 --> 00:54:17,440
Speaker 3: So the signal to noise that we measure with our

1042
00:54:17,520 --> 00:54:21,000
Speaker 3: experiment increases as the number of pulsars that we add

1043
00:54:21,040 --> 00:54:23,319
Speaker 3: and as the square root of the time. So it's

1044
00:54:23,440 --> 00:54:26,600
Speaker 3: really important to add more pulsars. One way of adding

1045
00:54:26,640 --> 00:54:30,120
Speaker 3: these new pulsars is to go out and search for

1046
00:54:30,280 --> 00:54:32,480
Speaker 3: more pulsars. That's one thing that you can do, and

1047
00:54:32,560 --> 00:54:35,359
Speaker 3: that's one thing we should absolutely be doing. The more

1048
00:54:35,400 --> 00:54:37,600
Speaker 3: immediate thing that we can do is to collaborate with

1049
00:54:37,719 --> 00:54:41,720
Speaker 3: our colleagues and Europe and Australia and India and China

1050
00:54:41,800 --> 00:54:45,200
Speaker 3: and South Africa and share our data and make these

1051
00:54:45,320 --> 00:54:49,160
Speaker 3: huge mega combined data sets that will give us immediately

1052
00:54:49,200 --> 00:54:52,360
Speaker 3: access to the southern hemisphere to all of those pulsars.

1053
00:54:53,000 --> 00:54:56,200
Speaker 3: And when we combine our data streams from all the

1054
00:54:56,280 --> 00:54:59,440
Speaker 3: individual pulsars, we'll get denser data sets, and that can

1055
00:54:59,480 --> 00:55:04,319
Speaker 3: make us much much more sensitive to individual inspiraling super

1056
00:55:04,400 --> 00:55:07,600
Speaker 3: massive black hole binaries. So now that we have evidence

1057
00:55:07,680 --> 00:55:10,680
Speaker 3: for the background, which, to be honest, is a foreground.

1058
00:55:10,920 --> 00:55:13,720
Speaker 3: It's what we were looking for. It's not a nuisance

1059
00:55:14,080 --> 00:55:16,960
Speaker 3: that was the thing. Now it will be a background.

1060
00:55:17,160 --> 00:55:19,239
Speaker 3: Now it'll be a source of noise that we're trying

1061
00:55:19,280 --> 00:55:22,080
Speaker 3: to get rid of. And so what's underneath right, Well,

1062
00:55:22,200 --> 00:55:26,120
Speaker 3: there'll be some anisotropy in the gravitational wave background, similar

1063
00:55:26,239 --> 00:55:29,239
Speaker 3: to the cosmic microwave background. We'll be able to make

1064
00:55:29,440 --> 00:55:34,160
Speaker 3: maps of the gravitational wave universe. And what I'm really

1065
00:55:34,239 --> 00:55:37,680
Speaker 3: excited for is when we find some sort of gravitational

1066
00:55:37,760 --> 00:55:42,040
Speaker 3: wave hotspot on one of those maps and there's no galaxy,

1067
00:55:42,440 --> 00:55:45,600
Speaker 3: right Like, what happens if there's gravitational waves that are

1068
00:55:45,640 --> 00:55:48,640
Speaker 3: coming from a place where there's no known galaxies, That's

1069
00:55:48,680 --> 00:55:51,000
Speaker 3: when I think things just start to get really interesting.

1070
00:55:52,160 --> 00:55:55,040
Speaker 3: So stuff like that could be right around the corner

1071
00:55:55,200 --> 00:55:58,239
Speaker 3: and that's super exciting. We can also do tests of

1072
00:55:58,320 --> 00:56:04,520
Speaker 3: general relativity. Relativity predict two gravitational wave polarizations, so just

1073
00:56:04,640 --> 00:56:07,600
Speaker 3: like light, you know, we have plus and cross polarizations

1074
00:56:07,640 --> 00:56:12,520
Speaker 3: with gravitational waves, but extensions to general relativity predict even

1075
00:56:12,640 --> 00:56:16,520
Speaker 3: more polarizations, like for example, there could be a breathing mode.

1076
00:56:16,920 --> 00:56:20,920
Speaker 3: So instead of gravitational waves stretching and squashing the fabric

1077
00:56:21,000 --> 00:56:24,239
Speaker 3: of space time like a plus or a cross, it

1078
00:56:24,560 --> 00:56:28,000
Speaker 3: breathe so all of the space time, you know, goes

1079
00:56:28,080 --> 00:56:30,600
Speaker 3: out like you're taking a big breath, and then collapses

1080
00:56:30,640 --> 00:56:33,839
Speaker 3: in on itself like a balloon, getting bigger and then

1081
00:56:33,920 --> 00:56:35,000
Speaker 3: getting smaller again.

1082
00:56:35,360 --> 00:56:38,719
Speaker 2: Great, well, this is very exciting. Congratulations and thanks very

1083
00:56:38,800 --> 00:56:41,120
Speaker 2: much for taking some time to chat with me today.

1084
00:56:41,320 --> 00:56:44,919
Speaker 3: Thank you very much. I just want to really emphasize

1085
00:56:45,440 --> 00:56:48,880
Speaker 3: that NANOGrav is an experiment that's been taking data for

1086
00:56:49,000 --> 00:56:52,320
Speaker 3: fifteen years and it's taken a team of one hundred

1087
00:56:52,840 --> 00:56:59,520
Speaker 3: astrophysicists to get this result. So it's a huge, huge experiment,

1088
00:56:59,760 --> 00:57:01,759
Speaker 3: take in a lot of time and a lot of money,

1089
00:57:02,040 --> 00:57:04,480
Speaker 3: and it's just part of this global effort to detect

1090
00:57:04,520 --> 00:57:06,640
Speaker 3: gravitational way. So I really want to give a shout

1091
00:57:06,680 --> 00:57:09,280
Speaker 3: out to my colleagues all over the world. I started

1092
00:57:09,320 --> 00:57:12,279
Speaker 3: my career in Europe, right so I was part of

1093
00:57:12,280 --> 00:57:15,040
Speaker 3: the European Pulsar Timing Array for many years. And I've

1094
00:57:15,520 --> 00:57:18,960
Speaker 3: written papers with the Parks pulsar Timing Array in Australia,

1095
00:57:19,560 --> 00:57:22,320
Speaker 3: and you know, of course many papers with NANOGrav here

1096
00:57:22,840 --> 00:57:25,400
Speaker 3: in the US and in Canada. So I just want

1097
00:57:25,440 --> 00:57:28,400
Speaker 3: to mention that this is a huge experiment that's taken

1098
00:57:29,240 --> 00:57:31,200
Speaker 3: decades to get to where it's at right now.

1099
00:57:31,440 --> 00:57:33,720
Speaker 2: Absolutely, and I love when scientists from all over the

1100
00:57:33,760 --> 00:57:37,400
Speaker 2: world can come together to make a project bigger than

1101
00:57:37,480 --> 00:57:41,680
Speaker 2: anyone scientist. Absolutely. Well, congratulations again and thanks for joining us.

1102
00:57:42,000 --> 00:57:42,720
Speaker 3: Thank you so much.

1103
00:57:43,320 --> 00:57:46,080
Speaker 1: Awesome, pretty exciting it must be. And I when an

1104
00:57:46,120 --> 00:57:48,080
Speaker 1: experiment your work done for so long, it pays off

1105
00:57:48,240 --> 00:57:51,280
Speaker 1: and potentially changes how we see the universe.

1106
00:57:51,400 --> 00:57:53,080
Speaker 2: Yeah. I love the bit where she says that people

1107
00:57:53,160 --> 00:57:55,800
Speaker 2: warned her not to work on this experiment because it

1108
00:57:55,920 --> 00:57:56,840
Speaker 2: was such a long shot.

1109
00:58:01,120 --> 00:58:02,920
Speaker 1: Do you wish you had maybe listened to that advice

1110
00:58:03,960 --> 00:58:05,360
Speaker 1: or somebody had giving you that advice.

1111
00:58:06,000 --> 00:58:07,920
Speaker 2: No, I'm pretty happy with where I ended up, but

1112
00:58:07,960 --> 00:58:10,360
Speaker 2: I'm just glad that somebody's out there swinging for the

1113
00:58:10,440 --> 00:58:13,920
Speaker 2: fences and trying to discover crazy things about the universe.

1114
00:58:14,480 --> 00:58:16,920
Speaker 2: One of my favorite things about this discovery is that

1115
00:58:17,080 --> 00:58:19,760
Speaker 2: it was a surprise, you know, that they're seeing super

1116
00:58:19,840 --> 00:58:23,760
Speaker 2: massive black hole gravitational waves at like twice the amplitude

1117
00:58:23,800 --> 00:58:27,120
Speaker 2: that they expected. The universe is louder in super massive

1118
00:58:27,160 --> 00:58:29,320
Speaker 2: black hole gravitational waves than we thought.

1119
00:58:29,720 --> 00:58:32,280
Speaker 1: Yeah, sort of the same thing happened with Ligo, right, Like,

1120
00:58:32,440 --> 00:58:34,720
Speaker 1: there are more of these events, or at least we

1121
00:58:34,760 --> 00:58:36,680
Speaker 1: could listen to more of these events than we thought

1122
00:58:36,880 --> 00:58:38,880
Speaker 1: was possible or actually happening.

1123
00:58:39,040 --> 00:58:41,160
Speaker 2: Yeah, we have an episode coming up about how surprising

1124
00:58:41,240 --> 00:58:44,320
Speaker 2: it was that Lego saw so many black hole mergers

1125
00:58:44,440 --> 00:58:47,040
Speaker 2: when they did. And in this case also we were

1126
00:58:47,080 --> 00:58:49,680
Speaker 2: sort of lucky the universe was louder to our new

1127
00:58:49,880 --> 00:58:52,800
Speaker 2: kind of ear than we even dared. Hope.

1128
00:58:53,320 --> 00:58:56,080
Speaker 1: The universe is out in the field screaming with joy and.

1129
00:58:56,520 --> 00:58:59,080
Speaker 2: Gravity and finally we're able to listen.

1130
00:58:59,200 --> 00:59:03,200
Speaker 1: All right, welcome gras to the scientists at NANOGrav and congrats,

1131
00:59:03,240 --> 00:59:06,160
Speaker 1: I guess to all of us. Right, it's humanity opening

1132
00:59:06,240 --> 00:59:07,840
Speaker 1: up a new eyeball into.

1133
00:59:07,680 --> 00:59:10,280
Speaker 2: The universe, that's right, and hearing new kinds of physics

1134
00:59:10,360 --> 00:59:13,400
Speaker 2: going on out there. Hopefully in the future, as NANOGrav

1135
00:59:13,480 --> 00:59:16,240
Speaker 2: and their international partners stitch together their data into a

1136
00:59:16,320 --> 00:59:19,320
Speaker 2: massive data set and collect more pulsar as we can

1137
00:59:19,400 --> 00:59:22,720
Speaker 2: learn even more things about gravitational waves from the early

1138
00:59:22,920 --> 00:59:26,320
Speaker 2: universe and maybe even figure out how this whole crazy

1139
00:59:26,440 --> 00:59:27,360
Speaker 2: universe came to.

1140
00:59:27,440 --> 00:59:29,120
Speaker 1: Be and why it's in the middle of the field

1141
00:59:29,120 --> 00:59:32,360
Speaker 1: screwing for joy or not, it might be a different experiment.

1142
00:59:32,720 --> 00:59:34,640
Speaker 1: All right. Well, we hope you enjoyed that. Thanks for

1143
00:59:34,720 --> 00:59:36,680
Speaker 1: joining us, See you next time.

1144
00:59:44,640 --> 00:59:47,440
Speaker 2: Thanks for listening, and remember that Daniel and Jorge Explain

1145
00:59:47,480 --> 00:59:51,440
Speaker 2: the Universe is a production of iHeartRadio. For more podcasts

1146
00:59:51,480 --> 00:59:56,080
Speaker 2: from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever

1147
00:59:56,200 --> 00:59:57,920
Speaker 2: you listen to your favorite shows.