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Can a gravitational wave pass through a black hole? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, or Hey, which superhero throws the hardest hunch? That's
• 0:14
  Speaker 1: a hard one. It's maybe either the Hulk or Superman,
• 0:17
  Speaker 1: all right? And then which superhero is the best at
• 0:21
  Speaker 1: taking a punch, either the Hulk or Superman. I thought
• 0:27
  Speaker 1: you might say the guy made a rubber But then
• 0:29
  Speaker 1: the obvious question is what happens when Superman punches the Hulk?
• 0:35
  Speaker 1: Oh man, you're making my comic book fan brain burst
• 0:38
  Speaker 1: in the light right now. I think mostly Hulk just
• 0:41
  Speaker 1: gets mad, you know. That's what he does, a shower
• 0:45
  Speaker 1: of bricks. It doesn't blow up the multiverse, Yeah it does,
• 0:49
  Speaker 1: but it burst into a shower of money for Marvel
• 0:52
  Speaker 1: and DC, money flowing from our wallets to theirs, and
• 0:55
  Speaker 1: the light going into my brain. Hi am for Hammed
• 1:13
  Speaker 1: cartoonists and the co author of Frequently Asked Questions about
• 1:16
  Speaker 1: the Universe. Hi. I'm Daniel. I'm a particle physicist and
• 1:19
  Speaker 1: a professor at uz Irvine, and I always fast forward
• 1:22
  Speaker 1: through the punching scenes in superhero movies. Always really, what
• 1:26
  Speaker 1: if you're at the theater? What do you do? Take
• 1:28
  Speaker 1: a quick nap? And then I run upstairs to the
• 1:31
  Speaker 1: projection booth. Force my way in and fast forward those scenes.
• 1:36
  Speaker 1: I see you get arrested his physically what you do know?
• 1:39
  Speaker 1: I tune them out because in the end, none of
• 1:41
  Speaker 1: it really matters. You know, A punches B, B punches A.
• 1:44
  Speaker 1: In the end, they're still around. There's no consequences to
• 1:47
  Speaker 1: the punching, right right, Yeah, it's kind of it's kind
• 1:50
  Speaker 1: of a cliche. I guess in superhero movies and sci
• 1:52
  Speaker 1: fi movies, you'd always end in a mano a mano,
• 1:55
  Speaker 1: right exactly. More houses get destroyed, some cars get flipped,
• 1:58
  Speaker 1: but nobody really gets hurt. All Sometimes sometimes the hero dies.
• 2:02
  Speaker 1: Sometimes here dies, but is it ever because of punching?
• 2:05
  Speaker 1: And usually they come back in the sequel. So but anyways,
• 2:08
  Speaker 1: Welcome to our podcast Daniel and Jorge Explain the Universe,
• 2:11
  Speaker 1: a production of My Heart Radio, in which we try
• 2:13
  Speaker 1: to punch through your confusion about the nature of our universe.
• 2:18
  Speaker 1: We try to knock down the walls that prevent you
• 2:20
  Speaker 1: from understanding how this incredible cosmos has come together, how
• 2:24
  Speaker 1: it's woven at the very smallest scale, how it works
• 2:27
  Speaker 1: at the very largest scales, and how the amazing emergent
• 2:30
  Speaker 1: properties that are me and you and our curiosity come
• 2:33
  Speaker 1: together to make this a wonderful universe to explore. That's right,
• 2:37
  Speaker 1: because there is something about human nature that makes us
• 2:39
  Speaker 1: mad when we don't understand how things work out there
• 2:42
  Speaker 1: in the cosmos, and it makes us turn dream to
• 2:45
  Speaker 1: think about that. Maybe there are aliens out there who
• 2:47
  Speaker 1: do understand what's going on, or maybe just future of
• 2:50
  Speaker 1: humans will understand. And here we are trapped in antiquity,
• 2:54
  Speaker 1: trapped in the ancient past, where humans are so clueless
• 2:57
  Speaker 1: about the nature of our universe. We don't know the
• 3:00
  Speaker 1: answer to basic questions about how it's put together, how
• 3:03
  Speaker 1: old is the universe, how long will the universe survive,
• 3:06
  Speaker 1: what's it made out of in the end, and how
• 3:07
  Speaker 1: do all the pieces of it work? After all? Why
• 3:10
  Speaker 1: are we so ignorant? Oh man, you're jealous of future physicists.
• 3:14
  Speaker 1: That's that's interesting. Do you put a little notes for
• 3:16
  Speaker 1: them in your papers? Like? I hope this helps you?
• 3:19
  Speaker 1: I roll every paper is just a note to future physicists, right,
• 3:23
  Speaker 1: That's exactly what it is. But yes, I am jealous
• 3:26
  Speaker 1: of future physicists. I wish that I could live forever
• 3:28
  Speaker 1: so that I could understand what they figure out. Sometimes
• 3:31
  Speaker 1: I dream about taking a time machine and going forward
• 3:34
  Speaker 1: just to steal like a child's astronomy book from the
• 3:37
  Speaker 1: year three thousand or ten thousand, so I could figure
• 3:39
  Speaker 1: out what it is that humanity has unraveled in the future.
• 3:42
  Speaker 1: I think you're assuming they're going to get it right.
• 3:44
  Speaker 1: What if they take, you know, cosmically wrong and those
• 3:49
  Speaker 1: children's books are are all, you know, made up. I
• 3:51
  Speaker 1: think that science always gets it wrong, but it's sort
• 3:54
  Speaker 1: of gently drifts towards more and more right. So I
• 3:58
  Speaker 1: don't know that the future humanity will have final answers,
• 4:01
  Speaker 1: but I think they will have unraveled more mysteries. They
• 4:03
  Speaker 1: will have deeper questions, at least than the ones that
• 4:06
  Speaker 1: we have. I see the long arc of science fans
• 4:09
  Speaker 1: towards being annoyingly right. It naps towards the truth. Yes,
• 4:16
  Speaker 1: but it is a wonderful universe full of amazing and
• 4:18
  Speaker 1: incredible things, things that seem unstoppable sometimes and things that
• 4:21
  Speaker 1: seem to travel across billions of light years to get
• 4:25
  Speaker 1: where they will always get to go. And it's a
• 4:27
  Speaker 1: universe filled with things that we want to understand. We
• 4:30
  Speaker 1: can't go out and visit all of these incredible things
• 4:32
  Speaker 1: in the universe I'm not going to take a trip
• 4:34
  Speaker 1: to orbited black hole. I'm not going to surf along
• 4:37
  Speaker 1: a gravitational wave. I'm not going to walk along the
• 4:39
  Speaker 1: surface of a neutron star. But we can still do
• 4:42
  Speaker 1: thought experiments. We can imagine what might happen in crazy
• 4:46
  Speaker 1: combinations of these events, what happens if you bank a
• 4:48
  Speaker 1: neutron star off another one and into a black hole.
• 4:51
  Speaker 1: These are fun games to play in your mind, and
• 4:52
  Speaker 1: they can also teach us things about the universe. Right,
• 4:56
  Speaker 1: and if you're deluded enough, the mind games are just
• 4:58
  Speaker 1: as good as the real thing. Right, Surfing a neutron
• 5:01
  Speaker 1: star in your head, is in your daydream, it could
• 5:04
  Speaker 1: be just as good as doing it well. As an experimentalist,
• 5:06
  Speaker 1: I have to say that actually collecting data as no substitute,
• 5:10
  Speaker 1: because the universe is filled with surprises, and often we
• 5:13
  Speaker 1: think we know what will happen in these situations, and
• 5:15
  Speaker 1: the universe says, oops, sorry, silly human, We're going with
• 5:18
  Speaker 1: secret options. C. But to prepare for those things, just
• 5:21
  Speaker 1: to sort of like test our understanding of concepts, we
• 5:25
  Speaker 1: could try to bring together crazy intense ideas that we
• 5:28
  Speaker 1: have in our minds and wondered like What would happen
• 5:30
  Speaker 1: if they bounced off each other? What would happen if
• 5:32
  Speaker 1: I sent a against b What would happen in these
• 5:35
  Speaker 1: various scenarios. It's like tests our understanding. Wait, is this
• 5:38
  Speaker 1: whole episode about the Hulk punching Superman? Are we actually
• 5:42
  Speaker 1: doing this? We're talking about the physics Hulk punching the
• 5:46
  Speaker 1: physics Superman. I thought you were going to say the
• 5:49
  Speaker 1: maths Superman. That would be a matchup for the ages.
• 5:52
  Speaker 1: But it's sort of similar. Like if you ask questions
• 5:55
  Speaker 1: about what happens when Hulk fight Superman, then it makes
• 5:58
  Speaker 1: you think carefully about those extremes you never imagined before,
• 6:01
  Speaker 1: like who really is stronger? Like how hard of a
• 6:03
  Speaker 1: punch can the Hulk really take? Does he have bones
• 6:06
  Speaker 1: that can get broken? I mean, is it really impossible
• 6:10
  Speaker 1: for Superman to break hulks bones? I think these are
• 6:13
  Speaker 1: deep questions that you know, the writers of that universe
• 6:16
  Speaker 1: then have to figure out in our universe. It makes
• 6:18
  Speaker 1: us wonder about the mathematics of extreme situations, and those
• 6:21
  Speaker 1: are places where we can really learn about the fundamental
• 6:24
  Speaker 1: nature these objects were tossing against each other. Yeah, because
• 6:27
  Speaker 1: I guess thinking about the extremes really kind of pushes
• 6:29
  Speaker 1: your thinking about these things and really kind of pushes
• 6:31
  Speaker 1: your theories to maybe the breaking point, right, because there
• 6:34
  Speaker 1: are some questions you can ask that maybe don't have
• 6:37
  Speaker 1: an answer exactly, and they can reveal inconsistencies. And we
• 6:40
  Speaker 1: hear our listeners doing this kind of stuff all the time.
• 6:42
  Speaker 1: You know, they're wondering about like what if I throw
• 6:45
  Speaker 1: this into a black hole? What if I throw that
• 6:46
  Speaker 1: into a black hole? What do I throw another black
• 6:49
  Speaker 1: hole into another black hole? Right? And these are the
• 6:51
  Speaker 1: games they're playing in their minds when they're just seeking
• 6:54
  Speaker 1: to understand what are the rules, and the way to
• 6:57
  Speaker 1: figure out what the rules are are to push them
• 6:59
  Speaker 1: are to break them. Every parent knows that's true. And
• 7:01
  Speaker 1: so today on the podcast, we'll be tackling the question
• 7:09
  Speaker 1: can a gravitational wave pass through a black hole? Now, Daniel,
• 7:14
  Speaker 1: I'm disappointed. I would have prefer the question to be
• 7:16
  Speaker 1: kind of gravitational wave punch a black hole? That might
• 7:20
  Speaker 1: get some more clicks. Well, I guess you can ask
• 7:22
  Speaker 1: the question is can a gravitational wave punch a black
• 7:25
  Speaker 1: hole without getting slurped in? Oh? Well, no, I want
• 7:30
  Speaker 1: to see him fight. I want to see him go
• 7:32
  Speaker 1: mono amount of for twenty minutes at the end of
• 7:34
  Speaker 1: the movie. But it is a question that's fun to
• 7:35
  Speaker 1: think about because black holes are famously impenetrables, can survive anything.
• 7:40
  Speaker 1: You can even throw another black hole into it, and
• 7:43
  Speaker 1: gravitational waves are sort of famous for being able to
• 7:46
  Speaker 1: pass through almost anything because they are ripples in space
• 7:49
  Speaker 1: and time itself. And so it's our version of Hulk
• 7:52
  Speaker 1: versus Superman. Yeah, it's almost like this that famous question
• 7:56
  Speaker 1: what happens when an unstoppable force meets an unmovable object.
• 8:00
  Speaker 1: This is one of these like questions that just go
• 8:02
  Speaker 1: to infinity sort of. Well, you know, in philosophy you
• 8:04
  Speaker 1: can make up any kind of thing you want and
• 8:05
  Speaker 1: pit it against something else, and you're making up the
• 8:08
  Speaker 1: rules also, so it doesn't matter. But here in our
• 8:11
  Speaker 1: universe we think there are real rules and experiments should
• 8:14
  Speaker 1: have outcomes, Like this is something which we think happens
• 8:17
  Speaker 1: in the universe. You know, gravitational waves do hit black holes,
• 8:22
  Speaker 1: and so there is an answer either they make it
• 8:24
  Speaker 1: out the other side or they get slurred in. And
• 8:27
  Speaker 1: so then the question is like, what do we think
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  Speaker 1: is going to happen? Does our understanding of these things
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  Speaker 1: allow us to predict the result, and then could we
• 8:36
  Speaker 1: eventually go out and measure it. Yeah, because actually this
• 8:38
  Speaker 1: thing is happening right like right now, all the time, probably, right.
• 8:41
  Speaker 1: I mean, there are you know, as far as we know,
• 8:43
  Speaker 1: you know, millions of black holes out there, probably, and
• 8:46
  Speaker 1: there are definitely gravitational waves going around all the time
• 8:49
  Speaker 1: all around this. You know, we are bathed in very
• 8:52
  Speaker 1: very gentle gravitational waves all the time. And so this
• 8:56
  Speaker 1: in principle should be happening constantly, So something we should
• 8:59
  Speaker 1: be you're out eventually. Yeah. And also kind of black
• 9:02
  Speaker 1: hole surf a gravitational wave or is that the next episode,
• 9:06
  Speaker 1: that's the sequel, that's black hole surfer. One of them
• 9:09
  Speaker 1: dies when they come back in the sequel. Well, as usual,
• 9:12
  Speaker 1: we were wondering how many people have thought about this
• 9:14
  Speaker 1: impossible or maybe incredible question of what happens when a
• 9:18
  Speaker 1: gravitational wave meets a black hole. And so as usual,
• 9:21
  Speaker 1: Daniel went out there to ask people on the internet.
• 9:23
  Speaker 1: And so if you'd like to hear questions that might
• 9:25
  Speaker 1: blow your mind or at least blow up your understanding
• 9:28
  Speaker 1: of physics, please they'll be shy, right, to meet two
• 9:31
  Speaker 1: questions at Daniel and Jorge dot com and we can
• 9:34
  Speaker 1: all enjoy hearing your answers on the podcast. Think about
• 9:37
  Speaker 1: it for a second. Do you think a gravitational wave
• 9:40
  Speaker 1: can pass through a black hole? Here's what people had
• 9:43
  Speaker 1: to say. I don't think so, because a black hole
• 9:46
  Speaker 1: can sucking pretty much anything, Okay, But a gravitational wave
• 9:53
  Speaker 1: is just the change in the curvature of space as
• 10:01
  Speaker 1: it propagates with distance from a source of gravity at
• 10:07
  Speaker 1: the speed of light. I guess they could pass around
• 10:10
  Speaker 1: a black hole. Yeah. Maybe. And no, and through a
• 10:16
  Speaker 1: black hole because you would be really the world's the
• 10:21
  Speaker 1: universe's trapdoor. Yeah, because the gravity that you are feeling
• 10:27
  Speaker 1: in a gravitational wave is based off the distance of
• 10:32
  Speaker 1: the yourself from that object. So if there was a
• 10:35
  Speaker 1: black hole in between, yeah, it shouldn't affect it at all.
• 10:39
  Speaker 1: I would say that gravitational waves do because there is
• 10:44
  Speaker 1: some form holding it all together. So I would say, um,
• 10:49
  Speaker 1: I mean assuming that um hawkings, radiation can split, particles
• 10:57
  Speaker 1: can split and into it. Yeah, maybe you can. I
• 11:00
  Speaker 1: don't know, prove me wrong. Yes, I believe gravitational waves
• 11:04
  Speaker 1: would pass through a black hole. More specifically, I think
• 11:08
  Speaker 1: they would pass around a black hole. I think a
• 11:10
  Speaker 1: black hole would fundamentally change the gravitational wave in the
• 11:15
  Speaker 1: same way that an object would change a radar signal.
• 11:18
  Speaker 1: Maybe the gravitational wave would be able to give us
• 11:21
  Speaker 1: an intimate look at the structure, shape, the other factors
• 11:25
  Speaker 1: that we are unaware of. Of a black hole. I'm
• 11:28
  Speaker 1: not sure, because well, a black hole is as an
• 11:34
  Speaker 1: infinite gravity and I'm not sure if they can pass
• 11:39
  Speaker 1: through a black hole. I think they would be sucked in.
• 11:43
  Speaker 1: That would be my answer for that question. Now I
• 11:45
  Speaker 1: want to say, no, they can't, because surely nothing can
• 11:49
  Speaker 1: pass through a black hole, nothing can go through the
• 11:51
  Speaker 1: event horizon and through the singularity and then come out
• 11:55
  Speaker 1: the other end back into space. So no, no, I'm
• 11:59
  Speaker 1: going to say, know they can't do Surely they would
• 12:01
  Speaker 1: be swallowed up within the black hole. Um and you know,
• 12:06
  Speaker 1: kind of due to the massive curvature of space itself,
• 12:10
  Speaker 1: and gravitational waves are you know, kind of integrated with
• 12:14
  Speaker 1: very fabric of space. Then they would be directed only
• 12:17
  Speaker 1: in one direction light light is and all information that
• 12:20
  Speaker 1: is to the singularity. So no, gravitational waves can't pass
• 12:24
  Speaker 1: through a black hole. I believe gravitational waves can pass
• 12:28
  Speaker 1: through black holes, although I'm convinced the day will be
• 12:32
  Speaker 1: distarted as they go through. They will also started the
• 12:37
  Speaker 1: black hole while they are passing through, because gravitational waves
• 12:41
  Speaker 1: start space and time, and the black hole is part
• 12:45
  Speaker 1: of the space and time although almost itches on universe,
• 12:50
  Speaker 1: but the group gravitational waves will also be started by
• 12:53
  Speaker 1: their black hole. Black holes attract each other, so I
• 12:58
  Speaker 1: guess not fostival gravitational waves. They are this rebels in
• 13:05
  Speaker 1: space and time fabric and also a black hole distorts
• 13:12
  Speaker 1: space and time, and when these two interact, most likely
• 13:20
  Speaker 1: these waves won't get to affect the object, the black
• 13:26
  Speaker 1: hole itself, it's core. I don't know if gravitational waves
• 13:30
  Speaker 1: will pass through a black hole, but I do think
• 13:33
  Speaker 1: that they do because we are able to know where
• 13:37
  Speaker 1: there are black holes and when they shock with one
• 13:39
  Speaker 1: another because of the gravitational waves. So I'm guessing that
• 13:42
  Speaker 1: they do pass through it. They don't go inside it,
• 13:45
  Speaker 1: but they go around it. Yes, I think any part
• 13:49
  Speaker 1: of the wave that interacts with the event horizon is
• 13:52
  Speaker 1: going to get trapped inside because all all directions point
• 13:56
  Speaker 1: towards the singularity. Once you're inside the event horizon, but
• 13:59
  Speaker 1: I think any waves outside of that might get bent
• 14:02
  Speaker 1: around the black hole around the event horizon and actually
• 14:05
  Speaker 1: get like gravitationally focused, like gravitational lensing. All right, it
• 14:09
  Speaker 1: seems like people are cheering for Superman here in this
• 14:12
  Speaker 1: case for the black hole. No, many things the hole
• 14:15
  Speaker 1: will survive. No, there's some people that that's say it
• 14:16
  Speaker 1: will pass through it or at least around it. You know,
• 14:19
  Speaker 1: in the end, these things are both curvatures in space,
• 14:22
  Speaker 1: so it's tricky stuff to think about. All right, Well,
• 14:24
  Speaker 1: let's jump in and let's tackle one of these combatants
• 14:27
  Speaker 1: one at a time, and let's start with the black hole. Daniel,
• 14:31
  Speaker 1: what's a good way to define a black hole? So
• 14:33
  Speaker 1: you might think of a black hole something really weird,
• 14:35
  Speaker 1: very strange in our universe, something that's hard to grapple with.
• 14:39
  Speaker 1: But what a black hole looks like depends a lot
• 14:40
  Speaker 1: on sort of how close you are to it, and
• 14:43
  Speaker 1: from far away, a black hole just looks like anything
• 14:46
  Speaker 1: else that has mass. Right, black hole is a massive
• 14:50
  Speaker 1: object in space, which means that it bends space, and
• 14:54
  Speaker 1: so that curved space then causes gravity. So you can
• 14:57
  Speaker 1: be in an orbit around a black hole the same
• 14:59
  Speaker 1: way you can be in the orbit around the Sun
• 15:02
  Speaker 1: or an orbit around the Earth. Are away from any object,
• 15:05
  Speaker 1: its gravity is the same as like a point particle
• 15:08
  Speaker 1: placed at the center of mass, And that's true for
• 15:10
  Speaker 1: a black hole, or for the Sun, or for any
• 15:13
  Speaker 1: weird like huge unicorn shaped rock for example, and so
• 15:17
  Speaker 1: far away from a black hole, there's no difference. The
• 15:19
  Speaker 1: difference is that a black hole is very very dense.
• 15:22
  Speaker 1: So now take all the mass that's in the Sun,
• 15:24
  Speaker 1: for example, compacted down to a very very small space.
• 15:28
  Speaker 1: Now you can get much closer to the center of
• 15:32
  Speaker 1: mass than you could before. When it comes to the Sun,
• 15:34
  Speaker 1: you're gonna get to the surface of the Sun. Right
• 15:36
  Speaker 1: If you dig into the Sun, then the gravity from
• 15:38
  Speaker 1: the Sun actually starts to decrease. But with a black hole,
• 15:41
  Speaker 1: you can get closer and closer and closer to that
• 15:44
  Speaker 1: point mass, because general relativity tells us that that's exactly
• 15:48
  Speaker 1: what's They're a point mass, but all of that stuff
• 15:50
  Speaker 1: wrapped into a tiny little volume, So the gravitational curvature
• 15:54
  Speaker 1: becomes really really strong, so powerful that there's an event
• 15:58
  Speaker 1: horizon beyond which nothing can escape, no information can leak
• 16:02
  Speaker 1: out past the event horizon. Right, That's something that I
• 16:05
  Speaker 1: think is kind of interesting about black holes. It's that,
• 16:07
  Speaker 1: as you said, it's just a lot of mass compacted
• 16:10
  Speaker 1: really tightly. And it's not like as you're squeezing this
• 16:13
  Speaker 1: mass and suddenly something explodes or something pops or a
• 16:15
  Speaker 1: hole is punched through the based up of the universe.
• 16:18
  Speaker 1: It's almost like a gradual process. There's nothing exciting happens
• 16:21
  Speaker 1: as you squeeze down this mass. Yeah, that's a really
• 16:23
  Speaker 1: interesting question to imagine, Like taking a star and compacting
• 16:26
  Speaker 1: it down gradually, when does the black hole actually form?
• 16:31
  Speaker 1: And so a black hole is defined by the presence
• 16:34
  Speaker 1: of the event horizon, this region past which you cannot escape.
• 16:38
  Speaker 1: I remember the event horizon. It's not like, you know,
• 16:40
  Speaker 1: there's no flashing lights or firewalls or anything crazy there.
• 16:44
  Speaker 1: It's just sort of like a location. It's a distance
• 16:46
  Speaker 1: from this center of mass beyond which every future ends
• 16:51
  Speaker 1: up at the center. And you know, to actually know
• 16:53
  Speaker 1: where the event horizon is, you have to know the
• 16:55
  Speaker 1: whole future history of this object. It's the place pass
• 16:59
  Speaker 1: which no test particles ever escapes. You have to know
• 17:02
  Speaker 1: sort of like the future history of every test particle
• 17:05
  Speaker 1: you shoot at this thing to know where the event
• 17:07
  Speaker 1: horizon actually is. But we can calculate it. We can
• 17:09
  Speaker 1: say if you have a certain mass within a certain radius,
• 17:13
  Speaker 1: then you get an event horizon. So now take the
• 17:16
  Speaker 1: Sun and start squeezing it down smaller and smaller and smaller.
• 17:20
  Speaker 1: At some point it's going to pass that threshold where
• 17:23
  Speaker 1: you have enough mass within a radius, and then you
• 17:25
  Speaker 1: get that event horizon. Right, Like, as I'm squeezing the Sun,
• 17:28
  Speaker 1: it's gonna look like a sun that's just getting smaller
• 17:30
  Speaker 1: and smaller and smaller, maybe brighter, but then at some
• 17:33
  Speaker 1: point it's just gonna blink turn black. Right, It's not
• 17:36
  Speaker 1: like it's going to send out shock ways or the
• 17:38
  Speaker 1: universe is gonna shake. It'll just like blink turn black. Yeah,
• 17:41
  Speaker 1: And actually it's gonna gradually fade to black because as
• 17:44
  Speaker 1: it gets more and more gravitational curvature, the light that's
• 17:48
  Speaker 1: coming off of that Sun is going to get more
• 17:50
  Speaker 1: and more gravitationally red shifted. So if you squeeze this
• 17:53
  Speaker 1: object down, it gets redder and redder and redder and
• 17:55
  Speaker 1: eventually black. So it's a gradual process. It's no like
• 17:58
  Speaker 1: crazy fireworks, just thing Yeah, pretty cool. And the other
• 18:02
  Speaker 1: thing about black holes is that they're hungry. They can
• 18:05
  Speaker 1: anything you throw into them into this event horizon supposedly
• 18:08
  Speaker 1: can never come out. Yeah, it's the most fascinating aspect
• 18:11
  Speaker 1: of these black holes that they eat anything. Right, Anything
• 18:15
  Speaker 1: with energy that enters the black hole just grows its
• 18:18
  Speaker 1: energy just makes it stronger. Right, So people ask me, like,
• 18:22
  Speaker 1: what happens to me throw a nuclear weapon into a
• 18:24
  Speaker 1: black hole? As if a black hole is like some
• 18:27
  Speaker 1: structure that you could explode if you like push on
• 18:30
  Speaker 1: it internally with enough force, and if you let this
• 18:33
  Speaker 1: nuclear bomb go inside and then blow up, you can
• 18:35
  Speaker 1: somehow explode the event horizon from the inside. Remember, the
• 18:38
  Speaker 1: event horizon is just there because of the strength of gravity.
• 18:42
  Speaker 1: And as you add more energy, even an exploding nuclear bomb,
• 18:46
  Speaker 1: you are just curving space more, which makes it stronger gravitationally. Right.
• 18:51
  Speaker 1: So there's nothing you can do to a black hole
• 18:54
  Speaker 1: to weaken it. Anything you do that adds energy makes
• 18:57
  Speaker 1: it stronger. Right. And we talked about last time happens
• 19:00
  Speaker 1: even if you put in a white hole into a
• 19:02
  Speaker 1: black hole, right, the black hole sort of wins. Yeah,
• 19:05
  Speaker 1: we don't know that white holes are real, but theoretically
• 19:07
  Speaker 1: a black hole will turn that white hole into another
• 19:10
  Speaker 1: black hole and then gobble it and you get some
• 19:13
  Speaker 1: big black hole. And we talked on the program recently
• 19:16
  Speaker 1: also about exactly what happens when two black holes merge,
• 19:19
  Speaker 1: how their event horizons come together. You get for a
• 19:22
  Speaker 1: moment this weird peanut shaped event horizon, and then it
• 19:25
  Speaker 1: turns into a new larger black hole with a spherical
• 19:29
  Speaker 1: event horizon. But it's super fascinating. Another thing that people
• 19:32
  Speaker 1: ask about in terms of like growing black holes is
• 19:35
  Speaker 1: how you actually see it happen. Like if you throw
• 19:37
  Speaker 1: a banana into a black hole, it's sort of like
• 19:40
  Speaker 1: falls towards the black hole, but then time slows down
• 19:43
  Speaker 1: because there's gravitational time dilation near the surface, so you
• 19:47
  Speaker 1: never actually see the banana fall into the black hole.
• 19:51
  Speaker 1: And people wonder about, like, well, how do we actually
• 19:53
  Speaker 1: see black holes growing if things freeze before they fall
• 19:56
  Speaker 1: into them. And so the answer is to think again
• 19:59
  Speaker 1: about the gravity national energy of the black hole. Right
• 20:02
  Speaker 1: as you throw this banana into the black hole, it's
• 20:05
  Speaker 1: not like it needs to pass the event horizons some
• 20:08
  Speaker 1: magical marker before the black hole officially has eaten it,
• 20:11
  Speaker 1: you know, the banana in the black hole, and they
• 20:12
  Speaker 1: are now part of a larger gravitational system. So the
• 20:15
  Speaker 1: banana is contributing to the gravitational energy of the black
• 20:19
  Speaker 1: hole before it crosses the event horizon. Another way to
• 20:22
  Speaker 1: think about that is that the event horizon is growing
• 20:25
  Speaker 1: outwards to meet the banana. They never actually meet. You
• 20:27
  Speaker 1: have to wait till time equals infinity for them to meet.
• 20:30
  Speaker 1: But this event horizon is getting pulled out by the
• 20:33
  Speaker 1: banana's mass, so they never actually cross. And if the
• 20:36
  Speaker 1: banana is the last thing anybody ever threw into this
• 20:39
  Speaker 1: black hole, you're right, it wouldn't actually fall in. But
• 20:42
  Speaker 1: then if somebody else comes along and through the donut
• 20:44
  Speaker 1: towards the black hole, that donut pulls the event horizon
• 20:48
  Speaker 1: out also pass the banana, So now the banana has
• 20:51
  Speaker 1: fallen in. So the last thing anybody ever throws into
• 20:54
  Speaker 1: a black hole never actually falls in, but everything else
• 20:57
  Speaker 1: that was thrown in before does pass the event horriz.
• 21:00
  Speaker 1: So that's a useful way to think about, like how
• 21:02
  Speaker 1: the energy of the black hole is growing, right, It's
• 21:04
  Speaker 1: almost like the black hole grows and eats the banana,
• 21:07
  Speaker 1: which is always a good idea banana. I mean, it
• 21:11
  Speaker 1: doesn't have any choice, right. The black holes just eats
• 21:13
  Speaker 1: whatever you throw at it. It might not like bananas,
• 21:16
  Speaker 1: might be really grumpy that somebody keeps the ring bananas
• 21:18
  Speaker 1: in there. But it's got no options. I guess it's not.
• 21:20
  Speaker 1: It's not going to let it slide. Well, what about
• 21:23
  Speaker 1: the idea that you know, sometimes black holes might be
• 21:26
  Speaker 1: connected through a warm hole to a white hole, right,
• 21:29
  Speaker 1: which would be spewing out energy instead of sucking in energy,
• 21:33
  Speaker 1: and that energy is coming from the black holes. Is
• 21:36
  Speaker 1: it's possible for a black hole to kind of leak
• 21:38
  Speaker 1: out or or you know, shrink because it's leaking through
• 21:41
  Speaker 1: a white hole somewhere else. Yeah, there are ways that
• 21:43
  Speaker 1: black holes can shrink. One of them that sounds sort
• 21:45
  Speaker 1: of stronger. Theoretical footing that we've never seen it before
• 21:48
  Speaker 1: is Hawking radiation. You know, the quantum effects near the
• 21:51
  Speaker 1: edge of the black hole, and the black hole having
• 21:53
  Speaker 1: a non zero temperature suggests that it should be radiating
• 21:56
  Speaker 1: away energy, which shrinks the mass of the black hole.
• 21:59
  Speaker 1: So the concept there again is the size of the
• 22:01
  Speaker 1: black hole. The radius the event horizon depends on the
• 22:04
  Speaker 1: total energy there. So if you take away energy, the
• 22:07
  Speaker 1: black hole shrinks. And another option, though even on much
• 22:10
  Speaker 1: worse footing theoretically, is this question of white holes. It
• 22:14
  Speaker 1: is possible that black holes and white holes sort of
• 22:17
  Speaker 1: share a singularity that connected by a wormhole. But this
• 22:20
  Speaker 1: is like speculation upon speculation, But yes, absolutely, mask could
• 22:24
  Speaker 1: then move through that wormhole, come out the other side
• 22:27
  Speaker 1: of the white hole, and shrink the size of that
• 22:29
  Speaker 1: black hole. And what would happen to the banana that
• 22:31
  Speaker 1: was at the border they got absorbed? Would it have
• 22:33
  Speaker 1: it then have a chance to escape the black hole
• 22:35
  Speaker 1: once it's inside the event horizon. I think the only
• 22:38
  Speaker 1: way for it to get out would be through the
• 22:40
  Speaker 1: wormhole and out the white hole. But what if the
• 22:43
  Speaker 1: you know, event horizon shrinks, I guess the banana would
• 22:47
  Speaker 1: fall in a little bit too, right, exactly, Yeah, banana
• 22:49
  Speaker 1: would fall in with it. So the moral of the
• 22:51
  Speaker 1: story is, if you drop your banana into a black hole,
• 22:53
  Speaker 1: let it go, because man, it's gone. Well, you can
• 22:57
  Speaker 1: go to the nearest white hole and maybe he'll come
• 22:59
  Speaker 1: out one particle at a time or something. That's right,
• 23:04
  Speaker 1: Go near your white hole and open your mouth and
• 23:05
  Speaker 1: see if it tastes like banana or donuts if you're lucky,
• 23:10
  Speaker 1: maybe banana donuts. There you go, it's the ultimate smoothie maker.
• 23:13
  Speaker 1: Just throw all of your ingredients into the black hole
• 23:15
  Speaker 1: and go stand by the white hole and see what
• 23:16
  Speaker 1: comes out. No, Danny, what happens if I take a
• 23:20
  Speaker 1: banana and put it through a donut? I think you
• 23:22
  Speaker 1: just invented the latest pop food craze. A bonut A BANONU.
• 23:28
  Speaker 1: All right, Well, that's a black hole. It's full of
• 23:30
  Speaker 1: interesting mysteries and amazing effects and physics that that are
• 23:34
  Speaker 1: going on and that we are starting to understand. But
• 23:37
  Speaker 1: then there's another fundamental and monumental thing in the universe
• 23:40
  Speaker 1: called a gravitational wave, and so let's get into what
• 23:44
  Speaker 1: that is and what's going to happen when the two
• 23:46
  Speaker 1: meet at the same place. But first let's take a
• 23:49
  Speaker 1: quick break. All right, we're talking about fun fan fiction.
• 24:04
  Speaker 1: I guess you know we're where conjuring imaginary meetups in
• 24:10
  Speaker 1: the universe physics fan fiction exactly, it's not quite fan fiction,
• 24:14
  Speaker 1: because this thing is happening, this question is happening all
• 24:17
  Speaker 1: over the universe. Probably gravitational waves are passing through all
• 24:20
  Speaker 1: of space and time and there are black holes in
• 24:23
  Speaker 1: the universe. So somewhere out there right now, there's probably
• 24:26
  Speaker 1: a gravitational wave hitting a black hole, almost certainly, and
• 24:30
  Speaker 1: the universe has to decide what happens. Right. That's the
• 24:33
  Speaker 1: amazing thing about experiments. You set something up in the
• 24:36
  Speaker 1: universe has to have an outcome. It can't be like,
• 24:39
  Speaker 1: I don't know, you figure it out, right. An answer
• 24:43
  Speaker 1: to experiments, the universe can't pass the buck exactly, can't
• 24:46
  Speaker 1: go pass I'm not sure about this one. They wrote
• 24:50
  Speaker 1: this cells into a corner and now they've got to
• 24:51
  Speaker 1: figure out how the movie ends, right exactly. Maybe that's
• 24:54
  Speaker 1: when the universe events time travel so we can red
• 24:56
  Speaker 1: con its own history. Yeah, Or maybe that's when it
• 25:01
  Speaker 1: invents event horizon so you can never know what's going on.
• 25:05
  Speaker 1: Maybe that's just the plot hole fixer for the universe.
• 25:07
  Speaker 1: It is the ultimate plot holes. Nice, but you know,
• 25:11
  Speaker 1: it's sort of an interesting statement in philosophy, this assumption
• 25:14
  Speaker 1: that the universe is in the end following laws, that
• 25:18
  Speaker 1: the laws aren't predictable, that we can figure them out,
• 25:21
  Speaker 1: and that the universe is bound by them. Right, That
• 25:23
  Speaker 1: every physical effect has a physical cause, and that means
• 25:27
  Speaker 1: that any physical situation you set up must be predictable
• 25:31
  Speaker 1: by those physical laws, and so something's got to happen, right,
• 25:34
  Speaker 1: Something's got to happen. Is that the mantra for physics,
• 25:38
  Speaker 1: Something's got to happen. What happens if I collide a
• 25:41
  Speaker 1: basilian particles together? Something's going to happen. Yeah. In physics
• 25:44
  Speaker 1: it goes by the name of unitarity. It says that
• 25:47
  Speaker 1: the wave function when you integrate it has to be one,
• 25:49
  Speaker 1: which means something's got to happen. The probability distribution has
• 25:52
  Speaker 1: to go somewhere. It can't be like you do this
• 25:55
  Speaker 1: experiment and nothing happens, or the particles just disappear. Right,
• 25:59
  Speaker 1: Quantum in nation flows through the universe. It can't be deleted,
• 26:03
  Speaker 1: which means that it's got to go somewhere. That's the
• 26:05
  Speaker 1: theory at least, Or do you think that's what's going
• 26:07
  Speaker 1: to happen or it has to happen, right. It could
• 26:08
  Speaker 1: be then maybe there are places where things break down. Right.
• 26:11
  Speaker 1: Certainly could be. We definitely don't understand quantum mechanics that deeply,
• 26:14
  Speaker 1: and we could also be philosophically wrong about the universe's
• 26:18
  Speaker 1: assumption that every experiment has an outcome that makes sense
• 26:21
  Speaker 1: and is reproducible. You know, that's just an assumption. It's
• 26:23
  Speaker 1: been working really well so far, but we don't really
• 26:26
  Speaker 1: know why even that is. So. Yeah, if you want
• 26:29
  Speaker 1: to question the foundations, then we can go all the
• 26:31
  Speaker 1: way down. Yeah. I mean, we used to think that
• 26:33
  Speaker 1: energy is always conserved, but it turns out then energy
• 26:36
  Speaker 1: is not always conserved in the whole universe. Yeah, exactly.
• 26:39
  Speaker 1: Physics has been upending the apple card for hundreds of years.
• 26:42
  Speaker 1: Al Right, Well, we talked about black holes for a while,
• 26:45
  Speaker 1: and now the question is what happens when it HiT's
• 26:47
  Speaker 1: a gravitational wave, which is something that's pretty cool. So
• 26:50
  Speaker 1: let's step through it and talk about what is a
• 26:53
  Speaker 1: gravitational wave. A gravitational wave is a combination of something
• 26:55
  Speaker 1: that's very familiar to us, a wave, an update in information,
• 27:00
  Speaker 1: and something that's very weird, right, which is gravity. So
• 27:03
  Speaker 1: you can think about gravitational waves. It's sort of like
• 27:06
  Speaker 1: a way to communicate gravitational information. You know, like you
• 27:10
  Speaker 1: are in space and there's gravity around you, there's a
• 27:13
  Speaker 1: gravitational field around you. Imagine for a moment that that's
• 27:17
  Speaker 1: not changing. It's the same you know, whatever is creating
• 27:20
  Speaker 1: that gravitational field is fixed in place and not changing,
• 27:23
  Speaker 1: So there's no gravitational information, there's no updates. Right, every
• 27:26
  Speaker 1: moment your gravitational force is the same. But what if
• 27:29
  Speaker 1: that does change. What if somebody, for example, deletes the Sun,
• 27:33
  Speaker 1: which is the source of your gravity, then how does
• 27:35
  Speaker 1: that information propagate through the universe. Newton said that it
• 27:38
  Speaker 1: was instantaneous, that if you deleted the Sun, gravity far
• 27:41
  Speaker 1: away from the Sun would instantly change, right, it would
• 27:44
  Speaker 1: go to zero instantly. Einstein told us that that's not true.
• 27:47
  Speaker 1: That gravitational information is information and the gravitational field takes
• 27:52
  Speaker 1: time to update, and that update the change in the
• 27:55
  Speaker 1: gravitational field propagating through space because the source of the
• 27:59
  Speaker 1: gravi potational field has changed. That is a gravitational wave.
• 28:03
  Speaker 1: It's an update to the gravitational field. Right. It's kind
• 28:06
  Speaker 1: of like if you ask, like what happens if someone
• 28:08
  Speaker 1: shakes the sun or the sun like wiggles, Like do
• 28:11
  Speaker 1: you feel those wiggles right away or do you have
• 28:14
  Speaker 1: to wait a while for those wiggles to get to you?
• 28:17
  Speaker 1: And I guess you know. The idea is also that
• 28:19
  Speaker 1: if you're closer to the Sun. You're going to feel
• 28:20
  Speaker 1: those wiggles first, so there's sort of like a propagation,
• 28:24
  Speaker 1: like a ripple of those wiggles that um comes out
• 28:27
  Speaker 1: of the sun exactly, and those ripples travel at the
• 28:30
  Speaker 1: speed of light. So these gravitational waves is information that
• 28:33
  Speaker 1: propagates through the gravitational field. These which really are in
• 28:37
  Speaker 1: the end ripples in the curvature of space time because gravity, remember,
• 28:42
  Speaker 1: not really a force. It's just the effect of the
• 28:44
  Speaker 1: curvature of space time, which is invisible to us except
• 28:47
  Speaker 1: for this weird effect that it has on the path
• 28:50
  Speaker 1: of particles. And so as you say, if you wiggle
• 28:53
  Speaker 1: the Sun, for example, that should change the curvature of space,
• 28:56
  Speaker 1: and that causes a gravitational wave with frequency proportion all
• 29:00
  Speaker 1: to the wiggling, which is totally analogous to like how
• 29:02
  Speaker 1: you create electromagnetic waves. You take an electron which has
• 29:06
  Speaker 1: an electric field all through space, and you wiggle it
• 29:09
  Speaker 1: in an antenna, for example, at a certain frequency. Then
• 29:11
  Speaker 1: it shakes the electromagnetic field. It changes that field which
• 29:15
  Speaker 1: is emanating out from the electron, and that shake in
• 29:18
  Speaker 1: the electromagnetic field is a photon. It's a wiggle in
• 29:21
  Speaker 1: the electromagnetic field, and so in the same wave you
• 29:24
  Speaker 1: wiggle the source of gravity like the sun, then you
• 29:27
  Speaker 1: get wiggles in the gravitational field, and that's a gravitational wave. Right. Well,
• 29:32
  Speaker 1: I wonder if you can get into a little bit
• 29:34
  Speaker 1: of a rabbit hole here thinking about what simultaneity is
• 29:37
  Speaker 1: and whether or not you can actually measure a wave
• 29:41
  Speaker 1: moving or the or to claim that it didn't happen
• 29:44
  Speaker 1: at the same time, because you know, as we talked
• 29:47
  Speaker 1: about in the last episode, it's kind of hard to
• 29:49
  Speaker 1: synchronize clocks and make sure that the wave you didn't
• 29:51
  Speaker 1: feel that gravitational wave at the same time that it
• 29:54
  Speaker 1: was generated. I mean, simonsonety is complicated and it's not
• 29:57
  Speaker 1: trivial or intuitive. We can't think about a luck all
• 30:00
  Speaker 1: the way through space and imagine that everybody agrees on
• 30:04
  Speaker 1: the order of events. But that doesn't mean and we
• 30:06
  Speaker 1: can't talk about it from our frame and say, like,
• 30:08
  Speaker 1: what do we think happen firth, what do we see?
• 30:11
  Speaker 1: And in the case of gravitational waves, we can actually
• 30:13
  Speaker 1: measure their propagation through space. So we have seen gravitational
• 30:17
  Speaker 1: waves because we have detectors on Earth that are sensitive
• 30:20
  Speaker 1: to these things, and we have multiple detectors and we
• 30:22
  Speaker 1: can see them propagating through space because they hit one
• 30:25
  Speaker 1: detector before another detector. And this is the way we
• 30:28
  Speaker 1: can actually get directional information about gravitational waves. We can say, oh,
• 30:32
  Speaker 1: look it hit in New Orleans before it hit in
• 30:35
  Speaker 1: Washington and in Italy. Therefore it must have been going
• 30:38
  Speaker 1: in that direction. And so that helps us triangulate the
• 30:41
  Speaker 1: source of the gravitational wave because we can actually see
• 30:44
  Speaker 1: it arriving at different places at different times, which shows
• 30:48
  Speaker 1: you that it really is flowing through space at a
• 30:50
  Speaker 1: certain speed. M. Well, yeah, I guess if you measure
• 30:54
  Speaker 1: it first and if one place and then later in
• 30:56
  Speaker 1: the other one, then it's it's moving. It's moving through space. Yeah,
• 30:59
  Speaker 1: And we can see the same wiggle, right, It's like
• 31:01
  Speaker 1: each of these things have a very characteristic wiggle, usually
• 31:04
  Speaker 1: formed by the black hole merger or neutron star murder
• 31:07
  Speaker 1: that formed it. So we can tell that it's the
• 31:08
  Speaker 1: same gravitational wave. Now, as you said earlier, gravitational waves
• 31:12
  Speaker 1: are everywhere in space because every acceleration generates them. When
• 31:16
  Speaker 1: you run to the kitchen to get a banana and
• 31:19
  Speaker 1: you've accelerated, then you're creating little gravitational waves. Remember that
• 31:23
  Speaker 1: gravity is super duper weak, and so the gravity from
• 31:25
  Speaker 1: your body or from your banana is really really weak.
• 31:28
  Speaker 1: So while it does generate gravitational waves anytime anything accelerates,
• 31:33
  Speaker 1: those are basically impossible to see. That's why when we
• 31:36
  Speaker 1: look for gravitational waves, we usually look for ones generated
• 31:38
  Speaker 1: by incredibly massive objects, like huge stars or like black
• 31:43
  Speaker 1: holes with tens of times the mass of the Sun,
• 31:45
  Speaker 1: because you need a lot of gravity to generate gravitational
• 31:49
  Speaker 1: waves that we can actually see. Right, well, it sorta
• 31:51
  Speaker 1: depends how many bananas you eat too, right though, Right Like,
• 31:54
  Speaker 1: if you eat enough bananas, you will technically generate a
• 31:56
  Speaker 1: big gravitational wave. Exactly, if you just throw everything in
• 31:59
  Speaker 1: your free into the black hole and then eat it
• 32:01
  Speaker 1: as a smoothie at the other side of the white hole,
• 32:04
  Speaker 1: it's gonna taste pretty funny and you're gonna get pretty heavy. Now, confused,
• 32:08
  Speaker 1: but it's kind of interesting to think that everything does
• 32:10
  Speaker 1: generate a gravitational wave. Like right like, as you said,
• 32:13
  Speaker 1: if I jump up and down or move my arm,
• 32:14
  Speaker 1: I am generating gravitational wave. And in fact, that gravitational
• 32:18
  Speaker 1: wave that I'm generating with my arm. Even though it's
• 32:20
  Speaker 1: really small and weak, it is sort of propagating through
• 32:23
  Speaker 1: the universe, and technically it is gonna, you know, go
• 32:26
  Speaker 1: out to the edge of the universe, right, it will.
• 32:28
  Speaker 1: In the same way that if you, like, you know,
• 32:30
  Speaker 1: stand at night and shine your flashlight up at the
• 32:32
  Speaker 1: sky and turn it on and off, you're sending photons
• 32:35
  Speaker 1: which could travel forever, right, billions or trillions of years
• 32:39
  Speaker 1: until they hit some alien eyeball on some other planet
• 32:42
  Speaker 1: or never. Right, they could just go forever. In that
• 32:44
  Speaker 1: same way, everything that we throw out into space could
• 32:46
  Speaker 1: go forever. Remember though, that your gravitational waves, they start
• 32:50
  Speaker 1: off really weak, and they get weaker with distance because
• 32:53
  Speaker 1: the energy that's in the gravitational waves get spread out
• 32:56
  Speaker 1: over a larger and larger sphere as they get further
• 32:59
  Speaker 1: and further from you. So the strength of these gravitational
• 33:02
  Speaker 1: waves goes like one over the distance squared, just like
• 33:05
  Speaker 1: all other kinds of radiation. So they start off already weak,
• 33:08
  Speaker 1: and then twice as far away they are four times weaker,
• 33:11
  Speaker 1: and ten times as far away they are a hundred
• 33:13
  Speaker 1: times weaker, And that gets pretty stiff pretty quick. Right,
• 33:16
  Speaker 1: But I guess, as far as we know, gravitational waves
• 33:18
  Speaker 1: are not sort of quantum, right, So there's no minimum
• 33:21
  Speaker 1: size to these waves, is there, right? So technically the
• 33:24
  Speaker 1: waves I'm making with my arm right now are going
• 33:26
  Speaker 1: to travel throughout the entire U dors. Well, we don't know.
• 33:29
  Speaker 1: It's a great question, you know. People might be wondering
• 33:31
  Speaker 1: because we compared earlier gravitational waves to photons, and gravitational
• 33:35
  Speaker 1: waves are classical objects, meaning that we don't know if
• 33:39
  Speaker 1: they are made at the small scale out of some
• 33:41
  Speaker 1: quantum unit. So a better analogy is probably not the photon,
• 33:44
  Speaker 1: but like a big pulse of light, which might be
• 33:47
  Speaker 1: made out of many photons. So gravitational waves might be
• 33:51
  Speaker 1: classical objects, meaning it might be smooth and continuous and
• 33:54
  Speaker 1: as you say, they could get as small as you like,
• 33:56
  Speaker 1: or they might be made out of gravitons like the
• 34:00
  Speaker 1: quantum unit of gravity. But we just don't know because
• 34:03
  Speaker 1: we don't have a quantum theory of gravity, so we
• 34:06
  Speaker 1: can see gravitational waves without knowing whether or not there
• 34:10
  Speaker 1: are even are gravitons. Gravitons, if they exist, would be
• 34:14
  Speaker 1: like tiny little pieces of a gravitational wave. Each one
• 34:17
  Speaker 1: might have like tend to the sixteen gravitons. Yeah, and
• 34:21
  Speaker 1: you know, I think this sort of gets down to
• 34:23
  Speaker 1: the question of the episode, because you know, when you
• 34:26
  Speaker 1: shoot a flashlight out into this guy, you're sending out photons.
• 34:29
  Speaker 1: And technically those photons could go to the ends of
• 34:32
  Speaker 1: the universe and keep going. But more likely they're gonna
• 34:34
  Speaker 1: you know, hit a dust particle and bounce or get
• 34:37
  Speaker 1: absorbed or um, something happens to them when they hit
• 34:41
  Speaker 1: something else. And also, if you think about the analogy
• 34:43
  Speaker 1: of like a ripple in a lake, that wave, that
• 34:46
  Speaker 1: water wave loses energy as it goes from the friction
• 34:48
  Speaker 1: of the of the molecules. But the gravitational waves are different, right,
• 34:52
  Speaker 1: They sort of don't actually hit things when they hit things. Yeah,
• 34:56
  Speaker 1: gravitational waves are incredible because they in principle pass right
• 35:00
  Speaker 1: through stuff. You know, you have some like huge gas cloud.
• 35:04
  Speaker 1: Photons might not be able to penetrate it because they've
• 35:06
  Speaker 1: got to interact with all the stuff in the gas cloud.
• 35:08
  Speaker 1: They could absorbed by it, or they get reflected by
• 35:11
  Speaker 1: and whatever. Gravitational waves are ripples in the underlying substrate
• 35:16
  Speaker 1: of space itself, right, so they pass right through these
• 35:19
  Speaker 1: gas clouds. They can go basically through anything. They can
• 35:22
  Speaker 1: go through neutron stars, right, some of the densest non
• 35:25
  Speaker 1: black hole material in the universe. And so in that sense,
• 35:28
  Speaker 1: they're an incredible way to see the universe because they
• 35:31
  Speaker 1: can pass through stuff that is otherwise totally opaque to us.
• 35:36
  Speaker 1: So they're incredible like new kind of eyeball that like,
• 35:39
  Speaker 1: you know, excuse the analogy, but X rays everything in
• 35:42
  Speaker 1: the universe. One thing we're really excited about is using
• 35:45
  Speaker 1: them to see even further back in time. You know,
• 35:49
  Speaker 1: the earliest light that we can see from the universe
• 35:51
  Speaker 1: comes from the cosmic microwave background radiation, which is from
• 35:54
  Speaker 1: the first moment when the universe was transparent to photons,
• 35:58
  Speaker 1: like and years after the Big Bang, universe went from
• 36:02
  Speaker 1: opaque plasma to transparent gas so the photons could fly free.
• 36:06
  Speaker 1: We can't see before that with photons, but we might
• 36:09
  Speaker 1: be able to see before that with gravitational waves. People
• 36:12
  Speaker 1: are looking for gravitational waves created during the Big Bang
• 36:16
  Speaker 1: that we might even be able to see. Yeah, that's
• 36:18
  Speaker 1: pretty amazing, and so I guess what happens. Then we
• 36:21
  Speaker 1: have a gravitational wave hits something solid like a planet,
• 36:25
  Speaker 1: like it just totally goes through it, or does it
• 36:28
  Speaker 1: lose a little bit of energy? Does some of the
• 36:31
  Speaker 1: gravitational wave get absorbed, or does it really um you know,
• 36:35
  Speaker 1: nothing happens to the way. It's a great question. So
• 36:37
  Speaker 1: what happens to the stuff that's in space when a
• 36:41
  Speaker 1: gravitational wave passes through it? And you're right, this is
• 36:43
  Speaker 1: critical to understand when we get into the question of
• 36:45
  Speaker 1: what happens when it hits a black hole? So in
• 36:47
  Speaker 1: one sense, things do happen, right, Like we can see
• 36:50
  Speaker 1: gravitational waves because they do have an effect on our
• 36:53
  Speaker 1: physical systems. Like the way that we detect them is
• 36:56
  Speaker 1: that we measure distances changing remember gravitational way, it is
• 37:00
  Speaker 1: a change in the curvature of space. The curvature of
• 37:03
  Speaker 1: space really is another way of saying, like how far
• 37:05
  Speaker 1: apart are different parts of space to each other? You know,
• 37:08
  Speaker 1: you bend space by changing the intrinsic curvature of space
• 37:11
  Speaker 1: by saying, like this piece of space is now closer
• 37:14
  Speaker 1: than that one. And so the natural path or a
• 37:16
  Speaker 1: photon is what looks like a curve, it's really a
• 37:18
  Speaker 1: straight line through this bent space. And so the way
• 37:21
  Speaker 1: we detect them is by having these laser beams which
• 37:23
  Speaker 1: are shooting back and forth between mirrors constantly measuring the
• 37:27
  Speaker 1: distance between those mirrors. And so we see the gravitational
• 37:30
  Speaker 1: wave because it changes the distance between those mirrors. Because
• 37:33
  Speaker 1: it actually shrinks the space between them. We can measure
• 37:36
  Speaker 1: that because we know the speed of light and it's
• 37:37
  Speaker 1: bouncing back, we can time essentially the distance between the
• 37:40
  Speaker 1: speed of light. It's a bit more complicated because the
• 37:43
  Speaker 1: measurement has to be very precise, so they use interferometry.
• 37:46
  Speaker 1: We have a whole episode and video about that. But basically,
• 37:49
  Speaker 1: it does shrink the stuff in space, so you can
• 37:52
  Speaker 1: measure those distances, but then it shrinks it back, right,
• 37:55
  Speaker 1: so it squeezes it and then it comes back. So
• 37:57
  Speaker 1: from that sense, no energy is lost, right, space is rippled,
• 38:01
  Speaker 1: but then the gravitational wave just passes on. Right. It's
• 38:04
  Speaker 1: sort of like like I was thinking, it's sort of
• 38:06
  Speaker 1: like a slink. If you take a slinking, you stretch
• 38:08
  Speaker 1: it out and then you sort of pinch one bit
• 38:11
  Speaker 1: of it and then let go. It's gonna that pinching
• 38:13
  Speaker 1: is sort of going to propagate, right, It's gonna squeeze
• 38:16
  Speaker 1: the little bit of slinky next to it, but then
• 38:18
  Speaker 1: it's gonna stretch out, and then that's gonna squeeze the
• 38:20
  Speaker 1: little bit of slinky next to that one. And so
• 38:22
  Speaker 1: like space, you see this kind of squeezing and stretching
• 38:25
  Speaker 1: of space. But as you say, I think that's really
• 38:27
  Speaker 1: kind of the question is like, is any energy going
• 38:30
  Speaker 1: into moving and squeezing the stuff that's in this space, right,
• 38:34
  Speaker 1: because you're you're technically sort of accelerating it, right, Like
• 38:37
  Speaker 1: if a gravitational ways passes through the Earth, you're squeezing
• 38:40
  Speaker 1: all the Earth molecules together a little bit and all
• 38:43
  Speaker 1: then spreading them out a little bit. Doesn't it take
• 38:45
  Speaker 1: energy to squeeze them and also to unsqueeze them. So
• 38:48
  Speaker 1: this is a topic of great debate in the nineteen
• 38:50
  Speaker 1: fifties about whether gravitational waves can actually deposit energy into
• 38:54
  Speaker 1: matter or whether they just sort of like pass through
• 38:57
  Speaker 1: taking their energy with them. And find me came up
• 38:59
  Speaker 1: with a great way of thinking about this. It's called
• 39:01
  Speaker 1: the sticky bead example. And so imagine like some rod
• 39:04
  Speaker 1: and this rod is like really tightly held together with
• 39:07
  Speaker 1: atomic forces, and then you have beads on that rod
• 39:09
  Speaker 1: that can slide up and down, and so as the
• 39:11
  Speaker 1: gravitational wave comes through, the rod is sort of like
• 39:14
  Speaker 1: held to a fixed length by the atomic forces, and
• 39:17
  Speaker 1: the beads will be slid back and forth by the
• 39:19
  Speaker 1: gravitational wave because the relative distances between the beads will change,
• 39:24
  Speaker 1: but they'll slide back and forth and they'll end up
• 39:26
  Speaker 1: in the same position because there's no friction. But then
• 39:28
  Speaker 1: if you add friction to it, then what happens as
• 39:31
  Speaker 1: they slide back and forth on the rod is that
• 39:33
  Speaker 1: they do heat up the rod, and that takes some
• 39:36
  Speaker 1: of the energy from the gravitational waves. The answer from
• 39:39
  Speaker 1: this thought experiment is that the gravitational wave can deposit
• 39:44
  Speaker 1: some energy in this matter as it's passing through if
• 39:47
  Speaker 1: it generates friction between stuff. If some stuff resists the
• 39:50
  Speaker 1: motions of gravitational wave and other stuff doesn't, so you
• 39:53
  Speaker 1: get friction sliding between them. Right, But I guess wouldn't
• 39:57
  Speaker 1: everything have friction to them, right? Like nothing is quite
• 40:00
  Speaker 1: held together by perfect spring exactly, So there's nothing that's
• 40:03
  Speaker 1: really friction lists, So everything has some internal friction. Even
• 40:07
  Speaker 1: those mirrors in Lego right where they're measuring these gravitational waves.
• 40:10
  Speaker 1: They're held up on the wall, and the wall is
• 40:13
  Speaker 1: part of a larger cavity and his internal friction in
• 40:15
  Speaker 1: that whole setup. And so the answer in the end
• 40:18
  Speaker 1: is that gravitational waves do deposit energy and stuff as
• 40:21
  Speaker 1: they pass through, and so they do get fainter and
• 40:24
  Speaker 1: fainter as they propagate out through the universe. They do
• 40:27
  Speaker 1: get it sort of absorbed a little bit. But I
• 40:29
  Speaker 1: guess I'm thinking, you know, kind of like a wave
• 40:31
  Speaker 1: in the ocean or at the at the beach. You know,
• 40:33
  Speaker 1: a wave is not just like in one spot. It's
• 40:36
  Speaker 1: a long piece of the coast, right Like a wave
• 40:38
  Speaker 1: is really long, and if it goes through me, I
• 40:41
  Speaker 1: might block a little bit of it where I am,
• 40:44
  Speaker 1: but the whole wave's still going to keep going, and
• 40:46
  Speaker 1: in fact, it's sort of almost reassembles itself after it
• 40:49
  Speaker 1: hits me. A wave is a very long object, and
• 40:51
  Speaker 1: in this case, a gravitational wave is more like a
• 40:53
  Speaker 1: sphere right from a black hole Merger. Gravitational waves admit
• 40:57
  Speaker 1: in every direction, and so if you put hoges in
• 40:59
  Speaker 1: one direction and you will get heated up by the
• 41:01
  Speaker 1: gravitational way, but the rest of it won't be impacted
• 41:04
  Speaker 1: at all, and you can calculate what would happen after
• 41:06
  Speaker 1: it hits you, right, the way sort of reforms, so
• 41:08
  Speaker 1: it's a little bit distorted on the other side. All right,
• 41:10
  Speaker 1: Well that's a gravitational wave. They're pretty interesting. They are
• 41:13
  Speaker 1: not quite unstoppable, right, You can't stop him if you
• 41:16
  Speaker 1: have enough mass, although they are so large, and maybe
• 41:19
  Speaker 1: they might ignore an obstacle that it's in their path.
• 41:22
  Speaker 1: And so let's get into the ultimate question of what
• 41:24
  Speaker 1: happens when a gravitational wave meets a black hole? Which
• 41:28
  Speaker 1: one will get matter? But first let's take a quick break.
• 41:43
  Speaker 1: All right, we're talking about the ultimate meetup of what
• 41:46
  Speaker 1: happens when a gravitational wave meets a black hole? And
• 41:49
  Speaker 1: I guess, first of all, Daniel, is it a friendly meeting,
• 41:51
  Speaker 1: like are they looking forward to seeing hanging out or
• 41:55
  Speaker 1: is this a fight to be had? I think black
• 41:59
  Speaker 1: hole and gravitational waves it just sort of like screaming
• 42:02
  Speaker 1: through the universe. So I think they're just going to
• 42:04
  Speaker 1: get matter and matter about the matter. And I guess
• 42:07
  Speaker 1: they are they going to turn red or green? And
• 42:10
  Speaker 1: are are there gamma rays involved? Because right, black holes
• 42:13
  Speaker 1: are are full of gamma rays. Yeah, well, I think
• 42:16
  Speaker 1: that as they curve space, they tend to redshift things,
• 42:19
  Speaker 1: so they're gonna get redder and redder, right, which is
• 42:21
  Speaker 1: the color of anger and comic books, isn't it all? Right? Well,
• 42:24
  Speaker 1: that's the ultimate comic book question. Here, what happens when
• 42:26
  Speaker 1: a gravitational wave meets a black hole? And uh, what happens, Daniel?
• 42:31
  Speaker 1: Does it crack the black hole? Does a gravitational wave
• 42:33
  Speaker 1: gets sucked in or split in half? So once again
• 42:36
  Speaker 1: black holes win? Right? Black holes seem to win every
• 42:39
  Speaker 1: single time you throw something at them, another black hole,
• 42:41
  Speaker 1: a neutron, star, or a banana, even a gravitational wave.
• 42:45
  Speaker 1: You know, if you throw anything with energy at a
• 42:48
  Speaker 1: black hole, it will just gobble it up. And that
• 42:50
  Speaker 1: includes gravitational waves. You know, in the end, gravitational waves,
• 42:55
  Speaker 1: there are ripples in space and time, and they can
• 42:58
  Speaker 1: be affected by the curvature of space the same way
• 43:02
  Speaker 1: the like photons can't. Right, Photons don't have any mass,
• 43:05
  Speaker 1: but they are affected by the curvature of space. They
• 43:08
  Speaker 1: are red shifted by gravitational expansion, they are distorted by
• 43:12
  Speaker 1: gravitational lensing, they are captured by black holes. All the
• 43:16
  Speaker 1: same things also apply to gravitational waves. Right, Well, I
• 43:20
  Speaker 1: guess the question is, you know what might be confusing
• 43:23
  Speaker 1: is that, you know, a black hole is a distortion
• 43:26
  Speaker 1: in space time. Right, It's like space sort of curves
• 43:30
  Speaker 1: towards the center of the black hole, and a gravitational
• 43:33
  Speaker 1: wave is a ripple in that space time. So does
• 43:38
  Speaker 1: it even make sense for a gravitational wave to hit
• 43:41
  Speaker 1: a black hole? Right? It's it's sort of like, you know,
• 43:44
  Speaker 1: if it's a ripple and a rope, but the rope
• 43:46
  Speaker 1: is just going down the drain. Nothing really collides, it's
• 43:50
  Speaker 1: just ripples down the rope into the hole. Be careful
• 43:53
  Speaker 1: about how we think about a black holes. Right. There
• 43:55
  Speaker 1: may be some mass concentrated at the center, but really,
• 43:58
  Speaker 1: when we're talking about the black hole or talking about
• 44:00
  Speaker 1: the event horizon, the event horizon is not a surface
• 44:03
  Speaker 1: in the way that you can stand on. It's just
• 44:04
  Speaker 1: a location past which nothing can emerge. And so a
• 44:08
  Speaker 1: gravitational wave, you should think about it as energy the
• 44:10
  Speaker 1: same way you think about a banana as energy. Bananas
• 44:13
  Speaker 1: made of particles. They're just ripples in those quantum fields,
• 44:16
  Speaker 1: and so a gravitational wave is ripples in space itself,
• 44:20
  Speaker 1: but in the end, that's just energy. When that energy
• 44:23
  Speaker 1: enters into the region around this dense mass inside the
• 44:27
  Speaker 1: event horizon, and that energy is affected by the curvature
• 44:30
  Speaker 1: of space itself, even though that energy is in the
• 44:33
  Speaker 1: curvature of space itself, right, I guess I'm thinking. You know,
• 44:36
  Speaker 1: it's sort of like the wave. The energy doesn't really
• 44:40
  Speaker 1: um go anywhere or disappears or gets absorbed. It just
• 44:44
  Speaker 1: sort of falls into the hole like everything else. It
• 44:46
  Speaker 1: falls into the hole and eventually ends up at the singularity.
• 44:50
  Speaker 1: If you believe in classical general relativity that there are
• 44:52
  Speaker 1: singularities at the hearts of black holes. Remember, singularities are
• 44:55
  Speaker 1: like endpoints, right, you throw a particle into singularity, there's
• 44:59
  Speaker 1: no direction for to go, which is sort of like
• 45:01
  Speaker 1: ends there. That's one reason why we think maybe general
• 45:03
  Speaker 1: relativity is wrong, because it seems like information is being
• 45:07
  Speaker 1: deleted from the universe when it goes into the singularity.
• 45:09
  Speaker 1: But according to classical general relativity, then yeah, the gravitational
• 45:13
  Speaker 1: wave just gets like slurped up into the singularity and
• 45:16
  Speaker 1: ends there. Just adds its energy to the singularity. Doesn't
• 45:19
  Speaker 1: matter what form of energy you're in. Photon banana, gravitational
• 45:23
  Speaker 1: wave anything that enters in the event horizon just contributes
• 45:27
  Speaker 1: to the mass of that black hole. Right, But we
• 45:29
  Speaker 1: talked about earlier how like if you throw a banana
• 45:32
  Speaker 1: into a black hole, never actually falls in because you know,
• 45:35
  Speaker 1: time slows down and it just looks frozen at the
• 45:37
  Speaker 1: surface of a black hole. Does the same thing happen
• 45:40
  Speaker 1: to a gravitational wave, Like you'll see the ripple sort
• 45:42
  Speaker 1: of ripple in and then stop at this at the surface. Yeah,
• 45:45
  Speaker 1: the same thing happens, but remember there's more gravitational wave
• 45:48
  Speaker 1: coming behind it. Usually, like, unless you have a single
• 45:50
  Speaker 1: burst of gravitational waves, then there's a train of these
• 45:53
  Speaker 1: gravitational ripples coming through the universe, and so each one
• 45:57
  Speaker 1: is growing the black hole a little bit, helping the
• 46:00
  Speaker 1: one that came before it actually fall past the event horizon.
• 46:03
  Speaker 1: So it's more like a long chain of bananas than
• 46:05
  Speaker 1: an individual banana. That's delicious. But you were also asking
• 46:10
  Speaker 1: earlier about like the whole wavefront of the gravitational wave.
• 46:13
  Speaker 1: Because gravitational waves are affected by black holes, they can
• 46:16
  Speaker 1: also be like lensed by black holes. So you can
• 46:20
  Speaker 1: have like gravitational lensing of gravitational waves as they pass
• 46:25
  Speaker 1: around a black hole. So the ones that like actually
• 46:27
  Speaker 1: hit the event horizon are slurped in, but the ones
• 46:30
  Speaker 1: that go nearby, they can get like bent around the
• 46:33
  Speaker 1: black hole, right, and even get sort of like bent
• 46:35
  Speaker 1: back right reflected back towards the source of the gravitational wave. Yeah,
• 46:39
  Speaker 1: they absolutely could. In the same way. If you look
• 46:41
  Speaker 1: near a black hole, you're seeing all sorts of weird distortions,
• 46:44
  Speaker 1: Like you can see the other side of the event horizon,
• 46:47
  Speaker 1: and you can see stuff that we used around the
• 46:48
  Speaker 1: black hole and came back at you. Then you can
• 46:51
  Speaker 1: get the same effects with gravitational waves. And so for example,
• 46:54
  Speaker 1: if you have the bright source of gravitational waves and
• 46:57
  Speaker 1: then between you and that bright source is a black hole,
• 47:00
  Speaker 1: what would you see. You would see a little shadow,
• 47:03
  Speaker 1: or you would see gravitational waves coming in all directions,
• 47:05
  Speaker 1: except you would see this little shadow, just the same
• 47:08
  Speaker 1: way we saw a picture of a black hole recently,
• 47:10
  Speaker 1: right that was in the X ray. We saw an
• 47:12
  Speaker 1: accretion disc around a little shadow. So you would see
• 47:15
  Speaker 1: a gravitational wave shadow that's gobbling up some of the
• 47:19
  Speaker 1: black holes, but around it you would see these other
• 47:22
  Speaker 1: gravitational waves that are like lensed and distorted by the
• 47:25
  Speaker 1: black hole m interesting and with the gravitational wave also
• 47:29
  Speaker 1: continued to making the black hole bigger. It would right,
• 47:31
  Speaker 1: absolutely because it's got energy. But you know, there's an
• 47:33
  Speaker 1: important caveat here, which is that we're assuming that the
• 47:36
  Speaker 1: gravitational wave itself is pretty small, that like, relative to
• 47:40
  Speaker 1: the mass of the black hole, it's not that big
• 47:42
  Speaker 1: a deal because black holes typically have very large masses
• 47:45
  Speaker 1: and gravitational waves typically don't have that much energy. So
• 47:48
  Speaker 1: we're assuming basically like the black hole is fundamentally unchanged.
• 47:52
  Speaker 1: Maybe it grows a tiny bit, but it's not like
• 47:54
  Speaker 1: really changing the structure of space time around the black hole.
• 47:57
  Speaker 1: And then we're using that set up to like saw
• 48:00
  Speaker 1: all the wave equation for the gravitational wave in the
• 48:02
  Speaker 1: presence of an unchanged black hole, what would happen to
• 48:05
  Speaker 1: a gravitational wave If, however, the gravitational wave is like enormous,
• 48:09
  Speaker 1: is like really big, it's monster two supermassive black holes
• 48:13
  Speaker 1: have merged, then the kind of conation gets more complicated
• 48:16
  Speaker 1: because you can't assume that the gravitational wave is going
• 48:18
  Speaker 1: to not fundamentally change the black hole. And then it's
• 48:21
  Speaker 1: trickier to say exactly what happens. You need to like
• 48:23
  Speaker 1: fully solve the Einstein equations. You might get some weird
• 48:26
  Speaker 1: distortion to the black hole, but in the end, all
• 48:28
  Speaker 1: that energy is going to go into a bigger black hole. Well,
• 48:32
  Speaker 1: it's word of the thing that a gravitational wave has
• 48:35
  Speaker 1: energy in the traditional sense, because, as we talked about
• 48:38
  Speaker 1: it before in the podcast, anything with energy also bend
• 48:41
  Speaker 1: space and attracts other things. So it's almost like this
• 48:45
  Speaker 1: ripple in space is also rippling in space or you know,
• 48:49
  Speaker 1: attracting things. And the energy we're talking about is enormous.
• 48:52
  Speaker 1: You know, when two black holes merge, maybe they start
• 48:55
  Speaker 1: out each having like fifty times the mass of our Sun,
• 48:58
  Speaker 1: they don't form a black hole that has a hundred
• 49:01
  Speaker 1: times the mass of the Sun, and it ends up
• 49:03
  Speaker 1: with something like eighty times the mass of the Sun,
• 49:05
  Speaker 1: and the rest of it goes into gravitational waves. Just
• 49:09
  Speaker 1: not for a moment and think about how much energy
• 49:11
  Speaker 1: we're talking about. We're talking about all the energy is
• 49:14
  Speaker 1: stored in twenty times the mass of our Sun. Remember that,
• 49:18
  Speaker 1: like a single raisin a gram of matter has as
• 49:21
  Speaker 1: much energy as a nuclear bomb, right, So now imagine
• 49:25
  Speaker 1: how much energy is stored in the sun and now
• 49:27
  Speaker 1: twenty of those. So we're not talking about a small
• 49:30
  Speaker 1: amount of energy here. We're talking about incredible cosmic quantities
• 49:34
  Speaker 1: of energy radiated out through the universe. Right, But it
• 49:37
  Speaker 1: is the black hole at all affected by the graptational wave,
• 49:40
  Speaker 1: Like does it get even like squeezed a little bit,
• 49:43
  Speaker 1: or or you know, does it kind of like moving
• 49:45
  Speaker 1: a bit at all? Or is does black hole literally
• 49:48
  Speaker 1: totally ignore the gravitation wave and just sucks at it.
• 49:51
  Speaker 1: It definitely is affected by it. And as the gravitational
• 49:53
  Speaker 1: wave gets larger and larger, you start to approach the
• 49:56
  Speaker 1: case we talked about recently, which is like two black
• 49:58
  Speaker 1: holes merging. When two black holes merge, then you don't
• 50:02
  Speaker 1: just have like a big spherical event horizon. You get
• 50:05
  Speaker 1: this weird blob that forms as they merge, and it
• 50:07
  Speaker 1: becomes a peanut and eventually becomes a sphere. So something
• 50:10
  Speaker 1: similar would happen if you had a super powerful gravitational
• 50:13
  Speaker 1: wave that was approaching a black hole. It would distort
• 50:16
  Speaker 1: the shape of the event horizon. You would like grow
• 50:19
  Speaker 1: it out in one direction for another direction. Eventually a
• 50:22
  Speaker 1: black hole would like stabilize and thermalize and get into
• 50:24
  Speaker 1: equilibrium and become a sphere again. But momentarily it would
• 50:28
  Speaker 1: look really weird. And figure out exactly how that would look,
• 50:30
  Speaker 1: you'd have to solve the Einstein equations for that particular setup,
• 50:33
  Speaker 1: which is really hairy. Well, it's you sort of make
• 50:36
  Speaker 1: it sound like the black hole winds over the gravitational wave,
• 50:39
  Speaker 1: but I sort of feel kind of the opposite, because
• 50:42
  Speaker 1: gravitational wave is not just huge, it's sort of like
• 50:46
  Speaker 1: it's the size of basically the all the entire universe,
• 50:49
  Speaker 1: right like when two black holes collide, or a black
• 50:51
  Speaker 1: hole collides with a nutron star, it generates a sphere
• 50:55
  Speaker 1: of of a ripple, right like it's propagating in all
• 50:58
  Speaker 1: directions at the same time. And you know, if a
• 51:00
  Speaker 1: billions of light years away from the source, then literally
• 51:03
  Speaker 1: the size of that sphere is billions of light years wide,
• 51:07
  Speaker 1: whereas a black hole is really just like a tiny
• 51:09
  Speaker 1: little blip that it passes through, you know, sort of
• 51:12
  Speaker 1: like if you dig a hole in the sand at
• 51:14
  Speaker 1: the beach and the huge long wave passes through, Like
• 51:18
  Speaker 1: you know, some of the waves is going to fall
• 51:19
  Speaker 1: into the hole, but the rest of the way it's
• 51:20
  Speaker 1: just gonna keep going as if nothing happened, right, Yeah,
• 51:23
  Speaker 1: that's true. Gravitational waves are bigger than black holes, and
• 51:26
  Speaker 1: so some part of them will survive. Part that hits
• 51:29
  Speaker 1: the black hole it's gone, but the rest of it
• 51:32
  Speaker 1: will wiggle on through the universe. Yeah that's true. Yeah,
• 51:34
  Speaker 1: And in fact, the black hole might even sort of
• 51:37
  Speaker 1: feel insignificant to that gravitational wave. Right, It's like, oh,
• 51:40
  Speaker 1: here's a little holes, I'll just step over it. It
• 51:42
  Speaker 1: really is about the friends that the gravitational wave made
• 51:45
  Speaker 1: along the way, right, right, But do you know what
• 51:47
  Speaker 1: I mean, Like it's just as little blip. It's like
• 51:49
  Speaker 1: putting a little obstacle in a huge long, you know break,
• 51:53
  Speaker 1: you know, you know at the beach and the wave,
• 51:55
  Speaker 1: and in fact at the beach that when the wave
• 51:57
  Speaker 1: goes through an obstacle, it's sort of almost reforms itself
• 52:01
  Speaker 1: after the obstacle. The same thing happened here with the
• 52:03
  Speaker 1: black hole. Like with the wave that's me that immediately
• 52:06
  Speaker 1: hits the black hole will get sucked in, But will
• 52:08
  Speaker 1: the rest of the you know, waves sort of like
• 52:10
  Speaker 1: patch up that hole eventually? Yeah. Absolutely. As the wave
• 52:13
  Speaker 1: passes by the black hole, then the bits of the
• 52:16
  Speaker 1: gravitational wave that are like just barely making it passed.
• 52:19
  Speaker 1: They will continue to disperse, so eventually they will fan
• 52:22
  Speaker 1: out and sort of fill in that gap. It will
• 52:24
  Speaker 1: be totally unaffected. You could tell that that had happened.
• 52:27
  Speaker 1: You will see lensing effects on the gravitational wave from
• 52:30
  Speaker 1: the black hole. But yeah, there is no way that
• 52:32
  Speaker 1: one black hole can completely squash a gravitational wave. So
• 52:36
  Speaker 1: if you imagine, for example, a billion Superman's all running
• 52:39
  Speaker 1: out in different directions, then the Hulk can only stop
• 52:42
  Speaker 1: one of them. From that point of view, the billion
• 52:44
  Speaker 1: Superman win. The infinite sequels of Superman beats out the
• 52:48
  Speaker 1: one movie of the whole gave for me. Yeah, exactly,
• 52:52
  Speaker 1: all right, so it's sort of a toss up, I guess,
• 52:54
  Speaker 1: you know, like at the local level, a black hole
• 52:56
  Speaker 1: will win over the gravitational wave. But in the long term,
• 53:00
  Speaker 1: you know, the gravitational wave is going to have a better,
• 53:02
  Speaker 1: better life, don't They say? That's the best revenge to
• 53:05
  Speaker 1: have a good life. And remember that the universe is
• 53:10
  Speaker 1: filled with these gravitational waves. They're passing through you right now,
• 53:14
  Speaker 1: even if you're not the Hulk, Even if you're not Superman.
• 53:17
  Speaker 1: You're getting squeezed and tugged by gravitational waves probably generated
• 53:21
  Speaker 1: by ancient black holes gobbling each other billions of years ago.
• 53:25
  Speaker 1: It's everywhere. We have a whole episode about the cosmic
• 53:28
  Speaker 1: gravitational background, if you'd like to learn more about efforts
• 53:32
  Speaker 1: to discover and measure these very gentle gravitational waves. Yeah,
• 53:37
  Speaker 1: and even though you're the size that you are compared
• 53:39
  Speaker 1: to a giant black hole, you still affect that gravitational wave. Right.
• 53:43
  Speaker 1: It's passing through you, but you are sort of absorbing
• 53:45
  Speaker 1: a little bit of it each time. Right. Part of
• 53:47
  Speaker 1: the energy you have for your life today comes from
• 53:50
  Speaker 1: those gravitational waves. Well, I just have one more question, Daniel.
• 53:53
  Speaker 1: If I'm at the surface of a black hole and
• 53:55
  Speaker 1: I slip on a banana peal, do I still generate
• 53:58
  Speaker 1: a gravitational wave? You do? And then the black hole
• 54:01
  Speaker 1: eats it? And you exactly, you eat it when you
• 54:05
  Speaker 1: slip on the banana, and then the black hole eats
• 54:07
  Speaker 1: your waves. Lots of eating here in the universe. Time
• 54:11
  Speaker 1: to take a break for lunch, all right, Well, we
• 54:13
  Speaker 1: hope you enjoyed that and maybe made you think a
• 54:16
  Speaker 1: little bit about all of the amazing things that are
• 54:17
  Speaker 1: happening out there right now. There are gravitation waves hitting
• 54:21
  Speaker 1: black holes and black holes crashing into each other and
• 54:23
  Speaker 1: making gravitation a wave. It's a pretty busy universe, it is,
• 54:27
  Speaker 1: and those black holes continue to hide all of the
• 54:30
  Speaker 1: plot holes from us. We can't even figure out what's
• 54:32
  Speaker 1: going on, and they're by passing gravitational waves through them.
• 54:36
  Speaker 1: If gravitational waves did pass through black holes, then they
• 54:38
  Speaker 1: would be affected by what's inside and we can use
• 54:41
  Speaker 1: that as a way to see inside those black hole
• 54:44
  Speaker 1: event horizons. But unfortunately we can't, and they remain black. Oh,
• 54:49
  Speaker 1: Daniel getting mad, you're turning green or red. I'm just
• 54:53
  Speaker 1: frustrated by our inability to see the cosmic secrets hidden
• 54:57
  Speaker 1: inside black holes. Well, you can always ask the billion
• 54:59
  Speaker 1: superman in stud that are out there for future humanity.
• 55:02
  Speaker 1: All right, Well, thanks for joining us, see you next time.
• 55:13
  Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain
• 55:16
  Speaker 1: the Universe is a production of I Heart Radio. For
• 55:19
  Speaker 1: more podcast from my Heart Radio, visit the I Heart
• 55:22
  Speaker 1: Radio app, Apple Podcasts, or wherever you listen to your
• 55:25
  Speaker 1: favorite shows. Yeah,