Latest / Daniel and Kelly’s Extraordinary Universe / What's it like to fall into a black hole?

Transcript

What's it like to fall into a black hole? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Jorge, did you pack a bag? Why do I
• 0:10
  Speaker 1: need to back one? We're going on a field trip today.
• 0:13
  Speaker 1: Oh nice, Where are we going? We're going on a
• 0:16
  Speaker 1: physics field trip. Actually, does I mean I have to
• 0:19
  Speaker 1: go to a classroom or something. It means it's a
• 0:21
  Speaker 1: thought field trip, sort of like a thought experiment. I
• 0:24
  Speaker 1: don't need to bring snacks. It's a thought experiment, So
• 0:28
  Speaker 1: you can bring any snacks you can think of. Well,
• 0:30
  Speaker 1: I can think of a lot of snacks. I am
• 0:48
  Speaker 1: or handmade cartoonists and the creator of PhD comics. I'm Daniel.
• 0:52
  Speaker 1: I'm a particle of physicist and I enjoy snacks from
• 0:55
  Speaker 1: around the world. Do you just think you're a physicist, Daniel,
• 0:58
  Speaker 1: or are you an actual physicist? What's the difference? Welcome
• 1:02
  Speaker 1: to our philosophy podcast, folks, the philosophy of being a physicist.
• 1:06
  Speaker 1: That's another branch of philosophy we invented on this podcast.
• 1:10
  Speaker 1: Now is it a branch of philosophy or physics. It's
• 1:13
  Speaker 1: a whole new field all into itself. No. On this podcast,
• 1:17
  Speaker 1: we'd like to think that anybody who asked questions about
• 1:19
  Speaker 1: the universe is a physicist. So anyone who claims to
• 1:22
  Speaker 1: be a physicist is a physicist in my book, Well,
• 1:25
  Speaker 1: welcome to our podcast Daniel and Jorge Explain the Universe,
• 1:27
  Speaker 1: a production of I Heart Radio in which we all
• 1:30
  Speaker 1: act like physicists and ask deep questions about the universe.
• 1:34
  Speaker 1: How does it work, what does it look like? What
• 1:36
  Speaker 1: are those little bits over there? How did these things
• 1:38
  Speaker 1: even happen? And we ask those questions and try to
• 1:41
  Speaker 1: find the answers. Sometimes we get some answers, Sometimes we
• 1:44
  Speaker 1: just find more questions. But we hope to entertain you
• 1:47
  Speaker 1: a little bit along the way because there are a
• 1:49
  Speaker 1: lot of questions out there in the universe, because there
• 1:51
  Speaker 1: are a lot of mystery still out there unresolved in
• 1:55
  Speaker 1: the cosmos. That's right, because there are a lot of
• 1:57
  Speaker 1: people out there asking questions. Remember that questions don't belong
• 2:01
  Speaker 1: to the universe. They belong to us. There are our
• 2:03
  Speaker 1: personal questions about the universe. And the way that science
• 2:06
  Speaker 1: moves forward is people asking those questions, people thinking how
• 2:10
  Speaker 1: does that work? Or what does it look like in there?
• 2:13
  Speaker 1: Let's go find out. So the way we unravel secrets
• 2:16
  Speaker 1: to the universe is first by asking those big questions. Yeah,
• 2:19
  Speaker 1: I guess you're right. That is interesting to think about
• 2:21
  Speaker 1: that there are like the universe doesn't have mysteries on
• 2:25
  Speaker 1: its own. Like, I mean, the universe knows everything it
• 2:28
  Speaker 1: knows about itself. It's just us who don't know it.
• 2:31
  Speaker 1: And so we're asking questions and we make it a mystery.
• 2:33
  Speaker 1: That's right, except that we are part of the universe.
• 2:36
  Speaker 1: So maybe we are that part of the universe that's
• 2:38
  Speaker 1: asking itself questions about itself. Universe know thyself. Man, you
• 2:42
  Speaker 1: just give me a headache, a philosophical headache of physics tache.
• 2:47
  Speaker 1: But yeah, there are a lot of mysteries out there,
• 2:50
  Speaker 1: are a lot of pockets of unknown in the universe
• 2:53
  Speaker 1: that humans we just don't know what's inside of him,
• 2:55
  Speaker 1: that's right. And we are a curious species. We want
• 2:58
  Speaker 1: to see what's under that what's over that hill, what's
• 3:01
  Speaker 1: in that weird bag over there. We just want to know.
• 3:05
  Speaker 1: So we want to see all the cool stuff in
• 3:06
  Speaker 1: the universe. We use our telescopes to zoom in on
• 3:09
  Speaker 1: far away stuff. We pick up rocks that fell from space.
• 3:12
  Speaker 1: We want to see it all. Yeah, and there is
• 3:15
  Speaker 1: no more mysterious pocket of mystery, mysterious pocket of mystery
• 3:21
  Speaker 1: in the universe than a black hole. Black Holes are these,
• 3:25
  Speaker 1: you know, pockets of space time that nobody really knows
• 3:29
  Speaker 1: what's inside of them, And there might not be anything
• 3:32
  Speaker 1: interesting inside of them, but just the fact that nobody
• 3:34
  Speaker 1: can look inside, that nobody can go inside and tell
• 3:37
  Speaker 1: us what comes out, makes it mysterious. It's like if
• 3:40
  Speaker 1: I hold an empty pillow case in front of kids
• 3:42
  Speaker 1: and say what do you think's inside? They get excited.
• 3:45
  Speaker 1: Maybe this is a dinosaur were in there. It doesn't
• 3:47
  Speaker 1: really matter as long as it's hidden. It's mysterious and
• 3:51
  Speaker 1: what makes us curious. It sounds like something someone might
• 3:53
  Speaker 1: call the cops on you, Daniel, if you started doing
• 3:56
  Speaker 1: that random kids on the street. That was another thought experiment,
• 3:59
  Speaker 1: not recommended that in your thought arrest. Yeah, so black
• 4:05
  Speaker 1: holes are super weird. I mean they were theoretical up
• 4:08
  Speaker 1: until a little while ago, until we first saw one
• 4:12
  Speaker 1: with our own eyes, our own in tennis and cameras.
• 4:15
  Speaker 1: I mean that we saw them gravitationally, but nobody had
• 4:18
  Speaker 1: really sort of seen one until recently. That's right. There
• 4:21
  Speaker 1: were a theoretical curiosity because general relativity predicted that they existed,
• 4:25
  Speaker 1: but also predicted that they had something really really weird.
• 4:28
  Speaker 1: At their hearts, a singularity, a place where the theory
• 4:31
  Speaker 1: actually broke down because it predicted that space curvature went infinite.
• 4:36
  Speaker 1: So for a long time physicist thought, well, that probably
• 4:39
  Speaker 1: doesn't actually happen. The universe does something, there's something to
• 4:42
  Speaker 1: prevent that from really existing in reality. But then we
• 4:46
  Speaker 1: saw them. We see them at the center of our galaxy,
• 4:49
  Speaker 1: these super massive black holes with stars whizzing around them,
• 4:52
  Speaker 1: and we see stars that have collapsed into black holes.
• 4:56
  Speaker 1: So we know they are a real thing in the universe.
• 4:58
  Speaker 1: We just don't know it's in them. Yeah, well we
• 5:01
  Speaker 1: got a picture of them. They do indeed look like
• 5:03
  Speaker 1: black holes. I mean the picture that we got was
• 5:06
  Speaker 1: it last year, I think, or a couple of years ago.
• 5:08
  Speaker 1: It shows you a black circle basically with all the
• 5:12
  Speaker 1: right stuff scrolling around it, but it is indeed black
• 5:15
  Speaker 1: like there you can't see anything in the middle of it. Yeah,
• 5:18
  Speaker 1: it's simultaneously like amazing technologically and also kind of disappointing
• 5:23
  Speaker 1: because all you're really seeing is a sort of doughnut
• 5:26
  Speaker 1: of accretion disc around the black hole that's glowing in
• 5:29
  Speaker 1: just the way you'd expect, But the black hole itself
• 5:32
  Speaker 1: just looks black, and so it's sort of hard to
• 5:34
  Speaker 1: distinguish a black hole from nothing. Well, you can't see
• 5:37
  Speaker 1: any stars behind it, like in we look anywhere else
• 5:41
  Speaker 1: in space, you would see its stars behind him, right, Yeah,
• 5:45
  Speaker 1: that's true. And next to that really bright region from
• 5:48
  Speaker 1: the accretion disc, it is a pretty black shadow. So yeah,
• 5:51
  Speaker 1: you're seeing a very dark shadow from the black hole. Yeah.
• 5:54
  Speaker 1: So the question is what's inside of that dark region?
• 5:58
  Speaker 1: What's going on in there? Because you can't see in
• 6:01
  Speaker 1: it and there's nothing to see when you take a
• 6:03
  Speaker 1: picture of it. Yeah, and so the explorer and us
• 6:05
  Speaker 1: wonders what's in there? Is it possible to like send
• 6:08
  Speaker 1: a probe or a ship or even a person to
• 6:11
  Speaker 1: go explore? Yeah, and this is a situation that a
• 6:13
  Speaker 1: lot of people have considered, like what would it be
• 6:15
  Speaker 1: like to send something into the black hole? So today
• 6:19
  Speaker 1: on the podcast, we'll be asking the question, what's it
• 6:26
  Speaker 1: like to fall into a black hole? Is this something
• 6:30
  Speaker 1: you would wondered about? Horrid these days that have other
• 6:32
  Speaker 1: things to wonder about the faith of humanity without a
• 6:38
  Speaker 1: black hole. It makes me wonder like if I was
• 6:40
  Speaker 1: standing at the edge of a black hole, would I
• 6:42
  Speaker 1: be tempted to jump in because you might learn some
• 6:45
  Speaker 1: of the secrets of the universe. But on the other hand,
• 6:47
  Speaker 1: you'd probably die and at the very least would never
• 6:50
  Speaker 1: come back to see your family. So that'd be a
• 6:52
  Speaker 1: tough choice to have to make. Yeah, I think I
• 6:53
  Speaker 1: would wonder what it's like to jump into it, but
• 6:56
  Speaker 1: maybe not me jumping into it, you know what I mean?
• 6:59
  Speaker 1: Like I would love for I don't know somebody else
• 7:02
  Speaker 1: to do it, And for example, you'd happily send me
• 7:05
  Speaker 1: into a black hole if I could report back what
• 7:08
  Speaker 1: I mean, if you're standing at the edge of a
• 7:10
  Speaker 1: black hole, would I push you? Maybe don't answer that question. Well,
• 7:17
  Speaker 1: the good thing is the evidence would be totally gone.
• 7:20
  Speaker 1: They could never ask you if I pushed you or not.
• 7:22
  Speaker 1: The perfect crime. Wow, somebody has to write that science
• 7:25
  Speaker 1: fiction novel death by black hole black hole murder. Yeah,
• 7:28
  Speaker 1: the perfect crime because it technically it might not never happen.
• 7:32
  Speaker 1: It might even destroy the information. Wow. Well that's that.
• 7:36
  Speaker 1: The other next sci fi novels are criminals who use
• 7:39
  Speaker 1: black holes to erase their evidence. Yeah. So, as usually,
• 7:42
  Speaker 1: we were wondering how many people out there had asked
• 7:45
  Speaker 1: themselves this question, and how many people out there. I
• 7:48
  Speaker 1: think they have an answer for this. So, as usual,
• 7:50
  Speaker 1: Daniel went out into the wild of the Internet to
• 7:52
  Speaker 1: ask listeners what they think it's like to fall into
• 7:57
  Speaker 1: a black hole. And all of these folks answered this
• 7:59
  Speaker 1: question with knowing it in advance and no googling allowed.
• 8:03
  Speaker 1: If you would like the answer that questions for future episodes,
• 8:06
  Speaker 1: please write to us do questions at Daniel and Jorge
• 8:09
  Speaker 1: dot com. We will happily put your uninformed speculation on
• 8:12
  Speaker 1: the podcast. So I think about it for a second,
• 8:15
  Speaker 1: what do you think it would be like to fall
• 8:17
  Speaker 1: into a black hole. Here's what people had to say.
• 8:20
  Speaker 1: Either you fall in a really huge, immense black hole,
• 8:25
  Speaker 1: uh those super massive black holes, and you fall really
• 8:30
  Speaker 1: slowly and then died at some point, or you get
• 8:34
  Speaker 1: spaghettified in one of these smaller ones. I know that
• 8:39
  Speaker 1: as you fall into a black hole, you will be
• 8:42
  Speaker 1: experiencing everything in your own real time, so it's not
• 8:45
  Speaker 1: like everything will stop or anything like that for you.
• 8:48
  Speaker 1: As far as the rest, I would say, very painful,
• 8:51
  Speaker 1: thank you, be very good. I think it depends on
• 8:55
  Speaker 1: what you mean. So, like the body itself would be
• 8:58
  Speaker 1: what they're called spaghettifier and broken into its constituent atomic particles,
• 9:04
  Speaker 1: so you'd be pretty much ripped apart. But like the
• 9:07
  Speaker 1: gravity is so strong, but like even the difference in
• 9:10
  Speaker 1: your height would see a pretty significant shift in gravitational forces,
• 9:16
  Speaker 1: So the gravity on your feet would be very much stronger,
• 9:19
  Speaker 1: depending on restruction you're following in than the gravity you
• 9:22
  Speaker 1: know you'd feel. And at the top of your head, well,
• 9:24
  Speaker 1: I know that from the outside you'd never seen fallen
• 9:27
  Speaker 1: because time would slow down so much that they love frozen.
• 9:32
  Speaker 1: But you yourself, I think you'd probably be torn to shreds.
• 9:37
  Speaker 1: As you know, any part of you that was ahead
• 9:42
  Speaker 1: of some other part of you would be sucked in
• 9:45
  Speaker 1: much faster. And I guess we don't really know the answer,
• 9:49
  Speaker 1: but I assume it would be like torn to shreds.
• 9:51
  Speaker 1: I don't know. I think from what I know you
• 9:55
  Speaker 1: my body would be ripped apart. It would just be
• 10:00
  Speaker 1: and him, you know, stretched like a spaghetti uh, stretchy,
• 10:05
  Speaker 1: like one second you're there and the next ye're not. Obviously,
• 10:09
  Speaker 1: no one knows what it's actually like to fall into
• 10:12
  Speaker 1: a black hole, but from what I've read, the theory
• 10:16
  Speaker 1: is that you would be spaghettified because you know, if
• 10:19
  Speaker 1: you fell in the feet first, for example, your feet,
• 10:22
  Speaker 1: the gravity at your feet would be much stronger than
• 10:24
  Speaker 1: your head, so you get pulled apart. So I don't
• 10:28
  Speaker 1: think it would be much fun. All right, and not
• 10:31
  Speaker 1: good is the general message I get from. Yes, our
• 10:35
  Speaker 1: council of Advisers recommend against pushing your podcast host into
• 10:39
  Speaker 1: a black hole. Although that I heard a lot of
• 10:41
  Speaker 1: mentions of pasta, so you know that could be a
• 10:44
  Speaker 1: good snack. Yeah, exactly. I said, come prepared. You know,
• 10:46
  Speaker 1: we're going on a field trip, so everybody packed spaghetti
• 10:49
  Speaker 1: at something. All right, Well, there a lot of interesting answer,
• 10:55
  Speaker 1: is there. Some people think you would survive and some
• 10:57
  Speaker 1: people don't think you would survive. Yeah. I seem to
• 10:59
  Speaker 1: me like these folks have about black holes and if
• 11:01
  Speaker 1: even maybe given some thought to what it would be
• 11:03
  Speaker 1: like to fall into it before they heard this question,
• 11:06
  Speaker 1: so they were pretty well prepared. I was impressed. Good answers, listeners. Yeah,
• 11:09
  Speaker 1: and nobody have to push anyone into it either that
• 11:12
  Speaker 1: we know off and no people were tossed in the
• 11:16
  Speaker 1: black hole for the making of this episode. Yeah, so alright,
• 11:19
  Speaker 1: let's jump into it, Daniel. So today we're gonna sort
• 11:22
  Speaker 1: of paint the scenario right, like, we're gonna go next
• 11:24
  Speaker 1: to a black hole and then we're actually gonna go in.
• 11:28
  Speaker 1: We're going to talk about what it's going to be
• 11:29
  Speaker 1: like for somebody doing that. That's right, because a lot
• 11:32
  Speaker 1: of people mentioned this concern that you might not even
• 11:34
  Speaker 1: be able to go into a black hole because you
• 11:36
  Speaker 1: would get torn up before you get too close. So
• 11:40
  Speaker 1: I guess a question is is even possible to go
• 11:42
  Speaker 1: into a black hole and still feel that experience or
• 11:46
  Speaker 1: would you just die before even going in? Yeah, And
• 11:50
  Speaker 1: it turns out that it depends. It depends on the
• 11:52
  Speaker 1: size of the black hole. If you have a really
• 11:55
  Speaker 1: small black hole, then the edge the event horizon, the
• 11:58
  Speaker 1: part past which nothing thing can escape, is much closer
• 12:01
  Speaker 1: to the singularity at the heart, and so it's actually
• 12:04
  Speaker 1: difficult to get to the event horizon because you have
• 12:07
  Speaker 1: to get sort of closer to the black hole. But
• 12:09
  Speaker 1: for a bigger black hole, a massive one like the
• 12:12
  Speaker 1: one at the center of our galaxy, the event horizon
• 12:15
  Speaker 1: is so far from the singularity that it's safer to
• 12:18
  Speaker 1: approach the event horizon. Wait, what what do you mean?
• 12:21
  Speaker 1: So it is possible to go into the black hole.
• 12:24
  Speaker 1: It is actually possible to survive going over the event
• 12:27
  Speaker 1: horizon into the black hole as long as the black
• 12:30
  Speaker 1: hole is big enough. That's sort of the twist. All right, Well,
• 12:33
  Speaker 1: maybe break that down for us. What what would cause
• 12:36
  Speaker 1: me not to survive going into the black hole. So
• 12:38
  Speaker 1: the reason that a black hole pulls you apart this
• 12:40
  Speaker 1: spaghettification is due to the strength of its gravitational field,
• 12:44
  Speaker 1: but also due to how fast that gravitational field is
• 12:47
  Speaker 1: changing the slope of the gravitational field, if you will,
• 12:51
  Speaker 1: Because you are not a tiny point, you are an
• 12:53
  Speaker 1: actual physical thing. You have a front and a back
• 12:56
  Speaker 1: and two sides. And if the black holes pulling on
• 12:59
  Speaker 1: for example, you're head at a different strength than is
• 13:02
  Speaker 1: pulling on your feet, then effectively it's pulling your head
• 13:05
  Speaker 1: off of your body. It's tearing you apart. That's what
• 13:08
  Speaker 1: we call tidal forces. When gravitational forces are different on
• 13:11
  Speaker 1: one side of an object and on the other, that's
• 13:14
  Speaker 1: the same as having a force pull that thing apart.
• 13:18
  Speaker 1: And that's happening like right now. It's not something that
• 13:20
  Speaker 1: just happens near a black hole. Is like if I
• 13:23
  Speaker 1: stand up here on Earth, the Earth is pulling my
• 13:26
  Speaker 1: feet more than it's pulling my head. That's right. The
• 13:29
  Speaker 1: Earth is trying to pull your head off your body
• 13:31
  Speaker 1: right now. But the slope of the Earth's gravitation of field,
• 13:35
  Speaker 1: how much different it is at your feet and at
• 13:37
  Speaker 1: your head, is very, very small, and your body is
• 13:41
  Speaker 1: strong enough to resist that tension. You can resist the
• 13:44
  Speaker 1: tidal force of the Earth. So here on Earth it's weak.
• 13:47
  Speaker 1: Post gravity is relatively weak pasta compared to a black hole.
• 13:51
  Speaker 1: But in a black hole gravity is stronger, and so
• 13:54
  Speaker 1: the difference between the gravity and my head and my
• 13:56
  Speaker 1: legs is stronger. So that could pull me apart. That's right,
• 14:00
  Speaker 1: because these tidal forces, the thing that pulls you apart
• 14:02
  Speaker 1: depends on the forces being different at your foot and
• 14:05
  Speaker 1: at your head. And as you get closer to a
• 14:07
  Speaker 1: black hole, closer to the center of the black hole,
• 14:10
  Speaker 1: the curvature increases, the difference of the gravitational force at
• 14:14
  Speaker 1: your head and your foot increases. Now the Earth, you
• 14:17
  Speaker 1: can't get that much closer to the Earth than its surface.
• 14:19
  Speaker 1: If you dug into the Earth, the gravitational forces actually
• 14:22
  Speaker 1: start to weaken because you have a lot of the
• 14:24
  Speaker 1: mass on the outside of you. The cool thing about
• 14:26
  Speaker 1: a black hole is that it has so much mass
• 14:29
  Speaker 1: in a tiny little area, so you can get really
• 14:32
  Speaker 1: close to it without losing any of the gravitational force.
• 14:34
  Speaker 1: It just gets stronger and stronger and stronger. So that's
• 14:37
  Speaker 1: why for a black hole, you can get close enough
• 14:40
  Speaker 1: to it that it has an event horizon, and that
• 14:43
  Speaker 1: the tidal forces, these things pulling you apart, can be
• 14:45
  Speaker 1: stronger than your body can withstand. Now, I think that
• 14:49
  Speaker 1: usually people talk about that happening before you enter the
• 14:54
  Speaker 1: black hole. But you're telling me that it's not necessarily
• 14:56
  Speaker 1: Like I won't get spaghettified necessarily outside of the black hole.
• 15:00
  Speaker 1: I could get spaghettified inside of the black hole, in
• 15:02
  Speaker 1: which case I could technically go into a black hole. Yeah, exactly.
• 15:06
  Speaker 1: The threshold of which you get spaghettified depends on the
• 15:09
  Speaker 1: mass of the black hole. Now, so it is the
• 15:11
  Speaker 1: size of the black hole. But there's this point where
• 15:13
  Speaker 1: they cross. If a black hole is big enough, then
• 15:15
  Speaker 1: the sort of spaghettification point is inside the event horizon.
• 15:19
  Speaker 1: If the black hole is small enough, then the spaghetification
• 15:22
  Speaker 1: point is outside the event horizon. You get torn apart
• 15:25
  Speaker 1: before you go inside to a small black hole you
• 15:28
  Speaker 1: get torn apart after you go inside. For a really
• 15:30
  Speaker 1: big black hole, that's because the size of the black
• 15:33
  Speaker 1: hole where the edge of the event horizon is depends
• 15:35
  Speaker 1: differently on the mass than the spaghettification point. Right, And
• 15:39
  Speaker 1: when you say event horizon, you mean like the actual
• 15:42
  Speaker 1: like what this is considered the edge of the black hole,
• 15:44
  Speaker 1: Like that's the point where light can't escape exactly. And
• 15:47
  Speaker 1: that's just an arbitrary definition. We say the black hole
• 15:49
  Speaker 1: begins at the event horizon, the place where a ray
• 15:52
  Speaker 1: of light, even if pointed exactly away from the black hole,
• 15:57
  Speaker 1: still would not be able to escape. All right, So
• 15:59
  Speaker 1: then I guess then technically, if I wanted to go
• 16:01
  Speaker 1: into a black hole like pass the event horizon, I
• 16:04
  Speaker 1: need to pick a big black hole, right, because the
• 16:08
  Speaker 1: little one would turn me apart before I go into it. Yeah,
• 16:12
  Speaker 1: that's right. You need to pick a black hole about
• 16:13
  Speaker 1: a thousand times bigger than the mass of our sun
• 16:17
  Speaker 1: before it's safe to enter, before coming to the event
• 16:20
  Speaker 1: horizon will not tear you apart from the tidal forces.
• 16:24
  Speaker 1: That doesn't sound like a lot like I would expect to,
• 16:26
  Speaker 1: you know, decent sized black hole to be more than
• 16:28
  Speaker 1: a thousand times the mass. Yeah, and there are big
• 16:31
  Speaker 1: black holes out there that are much bigger than that.
• 16:33
  Speaker 1: In fact, there's a bit of a gap. There are
• 16:34
  Speaker 1: a few black holes out there that are like ten
• 16:37
  Speaker 1: or fifty or eighty times the mass of our sun.
• 16:39
  Speaker 1: These come from stars just collapsing into a black hole.
• 16:43
  Speaker 1: And then there are black holes in this sort of
• 16:44
  Speaker 1: million sun range, and these are the black holes at
• 16:47
  Speaker 1: the centers of galaxies, these super massive black holes. There
• 16:50
  Speaker 1: actually aren't a lot of black holes in that intermediate
• 16:53
  Speaker 1: range because there isn't a process to form them, unless there,
• 16:56
  Speaker 1: of course, are primordial black holes that nobody's seen those.
• 16:59
  Speaker 1: So your options are black holes that are sort of
• 17:02
  Speaker 1: small like the mass of our sun, which would be
• 17:04
  Speaker 1: too dangerous to get close to, or really really big
• 17:07
  Speaker 1: ones which are pretty safe to approach. There's no medium option,
• 17:12
  Speaker 1: like you can only buy a compact car or a
• 17:15
  Speaker 1: giant suv. Yeah, but the giant SUVs are safer, and
• 17:18
  Speaker 1: the bigger they get, the safer they are, because the
• 17:20
  Speaker 1: bigger they get, the further from the singularity the event
• 17:24
  Speaker 1: horizon is, and so the safer it is to go
• 17:27
  Speaker 1: across that event horizon, right, And the bigger black holes
• 17:29
  Speaker 1: are also harder to park, so there's a trade off. Yeah,
• 17:33
  Speaker 1: well you're going to the black hole. Nobody's gonna bring
• 17:35
  Speaker 1: the black hole to you. What do you mean, no
• 17:37
  Speaker 1: matter how important you are. Well, technically everyone near a
• 17:41
  Speaker 1: black hole pools on the black hole. So the technically
• 17:43
  Speaker 1: the black hole moves a little bit towards you tube. Yeah, exactly,
• 17:46
  Speaker 1: just like blowing in the wind. You know, it has
• 17:48
  Speaker 1: almost no impact. But you're right, You and the black
• 17:50
  Speaker 1: hole are a system, and together you're orbiting the center
• 17:53
  Speaker 1: of mass, which is basically the black hole. You're basically
• 17:56
  Speaker 1: negligible when it comes to black holes. Well, it sounds
• 17:58
  Speaker 1: like if you're curious to see what's inside of a
• 18:00
  Speaker 1: black hole and you want to get inside past the
• 18:02
  Speaker 1: event horizon, you need to pick a big one, otherwise
• 18:04
  Speaker 1: you'll be torn apart before you even get there. Right, Well,
• 18:08
  Speaker 1: let's get into what you would actually see as you
• 18:10
  Speaker 1: go into the black hole, and let's talk about what's
• 18:13
  Speaker 1: inside of it. But first let's take a quick break.
• 18:22
  Speaker 1: All right. I know, we are taking the probably the
• 18:24
  Speaker 1: worst field trip anyone can take, which is to go
• 18:28
  Speaker 1: inside of a black hole. He probably wouldn't come back
• 18:32
  Speaker 1: in time for races or the school bell. But we're
• 18:36
  Speaker 1: talking about what it would be like to go into
• 18:39
  Speaker 1: into it, Like what would you experience, what would you see,
• 18:41
  Speaker 1: what would you hear or feel as you go in? Yeah,
• 18:45
  Speaker 1: it would be pretty fun. I think it would be
• 18:46
  Speaker 1: an awesome field trip. I mean, it's not when you
• 18:48
  Speaker 1: could return from and so the permission slip would be
• 18:50
  Speaker 1: pretty crazy. But yeah, I think you might learn something
• 18:54
  Speaker 1: deep and true about the universe. You might reveal a secret,
• 18:57
  Speaker 1: an answer nobody knows, and so I think it'd be
• 18:59
  Speaker 1: pretty someome. I would definitely sign myself up for this
• 19:01
  Speaker 1: field trip really, like tomorrow, if somebody said, hey, Daniel,
• 19:05
  Speaker 1: would you like to go into a black hole and
• 19:06
  Speaker 1: learn the secrets of the universe? You would jump in?
• 19:09
  Speaker 1: You know, I might. I don't think I would take
• 19:11
  Speaker 1: a trip to Mars just for like planting a flag
• 19:14
  Speaker 1: on Mars, but to know the answer to one of
• 19:16
  Speaker 1: the deepest questions in the universe. I might, just because
• 19:20
  Speaker 1: remember that black holes are where general relativity breaks down,
• 19:24
  Speaker 1: is where we know that our theory of how space
• 19:26
  Speaker 1: and mass bend and dance with each other doesn't work anymore.
• 19:30
  Speaker 1: And something quantum, something new, something weird is going on
• 19:33
  Speaker 1: in there, and the only place we think general relativity
• 19:36
  Speaker 1: does break down is inside these black holes, and so
• 19:39
  Speaker 1: they literally hold secrets to really deep questions about the
• 19:41
  Speaker 1: universe that physicists are struggling over. So it's sort of
• 19:45
  Speaker 1: like asking, if I had an answer to a deep
• 19:47
  Speaker 1: question about the universe in this envelope, would you tear
• 19:50
  Speaker 1: it open? Yeah? Of course I would. I would shred
• 19:52
  Speaker 1: it instantly, right, even if the envelope tells you apart
• 19:55
  Speaker 1: they never come back. Well that's really interesting, because I mean,
• 20:00
  Speaker 1: you would give up knowing everything else about dear life
• 20:03
  Speaker 1: just to get this one secret. I think you'd be
• 20:05
  Speaker 1: really tempting. Yeah. I mean, fortunately, nobody's going to actually
• 20:08
  Speaker 1: ever offer me this, so I can bluff as much
• 20:10
  Speaker 1: as i'd like. Oh I see, I see, we can
• 20:12
  Speaker 1: have any opinion really doesn't matter, all right, So what
• 20:16
  Speaker 1: would it be like? So I picked the big black
• 20:18
  Speaker 1: hole because those are safer to approach than little black holes,
• 20:21
  Speaker 1: which is kind of weird, but I guess that's how
• 20:24
  Speaker 1: the math works. So now I picked a really big
• 20:27
  Speaker 1: one and I'm approaching it. What do I see? Well,
• 20:29
  Speaker 1: the first thing you see is the thing around the
• 20:32
  Speaker 1: doughnut around the black hole. Because most black holes are active,
• 20:35
  Speaker 1: they're still sucking stuff into them. But stuff doesn't fall
• 20:38
  Speaker 1: directly into the black hole because it still has some
• 20:41
  Speaker 1: angular momentum, which means it's spinning the way that we're
• 20:44
  Speaker 1: spinning around the Sun for example, without just falling in.
• 20:48
  Speaker 1: So the black hole has this stuff in orbit around it. Also,
• 20:51
  Speaker 1: that's called the accretion disc. It's the swirling mass of
• 20:54
  Speaker 1: gas and dust and doing all sorts of crazy stuff,
• 20:57
  Speaker 1: and some of it is falling in. But to all end,
• 21:00
  Speaker 1: it has to like lose some energy, has to give
• 21:02
  Speaker 1: up some angular momentum, and it does that by like
• 21:05
  Speaker 1: getting squeezed and glowing and giving off light. I guess.
• 21:08
  Speaker 1: In technically, a black hole is not that different than
• 21:11
  Speaker 1: like a sun, for example, so it would have stuff
• 21:14
  Speaker 1: orbiting around it. Yeah, it has hot gas orbiting around it,
• 21:17
  Speaker 1: and that hot gas is glowing. It's not having fusion necessarily,
• 21:21
  Speaker 1: but it's a very bright emitter. These are some of
• 21:23
  Speaker 1: the brightest things in the galaxy, these disks of gas
• 21:26
  Speaker 1: around a black hole. When they get really intense, you
• 21:29
  Speaker 1: call them quasars or even blaze ours, and they are
• 21:32
  Speaker 1: super duper crazy bright, So it's sort of ironic that
• 21:35
  Speaker 1: some of the brightest things in the universe are next
• 21:37
  Speaker 1: to some of the blackest things in the universe. Right,
• 21:39
  Speaker 1: But it's also not true that every black hole has
• 21:42
  Speaker 1: a bright accretion this like, some black holes could just
• 21:45
  Speaker 1: be like sitting there, right. Yeah, they certainly could be,
• 21:47
  Speaker 1: and it just depends on what's around it. If you
• 21:49
  Speaker 1: have a primordial black hole that was created during the
• 21:52
  Speaker 1: Big Bang and it's just like floating out around there
• 21:54
  Speaker 1: and there's nothing to eat, then it could just be
• 21:56
  Speaker 1: silently stealthily sitting there, totally black. The creation disc just
• 22:00
  Speaker 1: comes from stuff that's sort of on deck about to
• 22:03
  Speaker 1: fall into the black hole. But you're right, it's not
• 22:05
  Speaker 1: necessary that there's anything like that there. But if we're
• 22:09
  Speaker 1: choosing a supermassive black hole, the only way that happened
• 22:12
  Speaker 1: is if it's at the center of a galaxy, which
• 22:14
  Speaker 1: means it's been sucking in gas and dust and it's
• 22:16
  Speaker 1: surrounded by stuff. So you're pretty likely to find an
• 22:19
  Speaker 1: accretion disk around a supermassive black hole. Okay, right, that's right,
• 22:23
  Speaker 1: because we picked a big one to go into, so
• 22:25
  Speaker 1: it's it probably has that disk, and so as you
• 22:28
  Speaker 1: approach it, you probably want to avoid that disc, right,
• 22:31
  Speaker 1: and it's going to be a flat disc, so it
• 22:33
  Speaker 1: it's not that hard to avoid because it's pretty hot,
• 22:36
  Speaker 1: that's right. It's pretty hot and pretty nasty. And say
• 22:38
  Speaker 1: you want to avoid that, you want to come in
• 22:39
  Speaker 1: from the top or from the side, unless it's one
• 22:42
  Speaker 1: of these quasars, in which case it also has a crazy,
• 22:44
  Speaker 1: you know, spinning magnetic field that's beaming a huge beam
• 22:48
  Speaker 1: of light along the north and south axis, So you
• 22:50
  Speaker 1: want to come in a bit of an angle. But yeah,
• 22:52
  Speaker 1: there's an opening there. I mean, this is a black
• 22:54
  Speaker 1: hole field trip, but we still want to keep safety
• 22:56
  Speaker 1: in mount right, Yeah. And so the acretion disc is
• 22:59
  Speaker 1: at about three and a half times the width of
• 23:02
  Speaker 1: the black hole, right. Yeah. If you say the event
• 23:04
  Speaker 1: horizon is the radius of the black hole, then the
• 23:07
  Speaker 1: accretion disc sort of ends around three and a half
• 23:10
  Speaker 1: times that. Anything less than that and the stuff is
• 23:12
  Speaker 1: going to fall into the black hole. So everything at
• 23:15
  Speaker 1: that point and a little bit further out can sort
• 23:17
  Speaker 1: of stably orbit the black hole for a while until
• 23:20
  Speaker 1: it loses its energy through collision or radiation or whatever,
• 23:24
  Speaker 1: and then eventually falls in. But you don't find much
• 23:27
  Speaker 1: gas and dust less than three and a half because
• 23:29
  Speaker 1: that stuff has already falling in. I see, it's kind
• 23:31
  Speaker 1: of like the rings of Saturn. Like the rings of
• 23:33
  Speaker 1: Saturn are a ring, they don't go all the way
• 23:36
  Speaker 1: to the surface of the planet because stuff that's closer
• 23:39
  Speaker 1: to the planet falls in. So it is like it's
• 23:41
  Speaker 1: hanging out there in space. Yeah, exactly. So that's sort
• 23:43
  Speaker 1: of the inner edge of the accretion disc of the
• 23:46
  Speaker 1: black holes three and a half times of radius for
• 23:48
  Speaker 1: just that same reason. Yeah, alright, so I'm going into
• 23:51
  Speaker 1: the black hole, I move past the acreation disk. What
• 23:54
  Speaker 1: am I seeing now? So now what you're looking at
• 23:57
  Speaker 1: is the shadow of the black hole. And we have
• 23:59
  Speaker 1: to keep in mind as we get closer and closer
• 24:01
  Speaker 1: to the black hole, that space around the black hole
• 24:04
  Speaker 1: is bent. Remember that space is not just the backdrop,
• 24:07
  Speaker 1: is not just the emptiness. There's a dance between space
• 24:10
  Speaker 1: and mass. Mass tells space how to bend, and space
• 24:14
  Speaker 1: tells mass and light how to move. So that means
• 24:17
  Speaker 1: that photons don't travel in straight line. So what you're
• 24:20
  Speaker 1: looking at, what you see isn't necessarily what's there and
• 24:24
  Speaker 1: the environment of Earth where light mostly travels in straight lines.
• 24:27
  Speaker 1: You can assume that you're seeing things as they are,
• 24:30
  Speaker 1: but if there are lenses and distortion happening, then you
• 24:32
  Speaker 1: expect to see an image which doesn't necessarily correspond exactly
• 24:36
  Speaker 1: to what's literally there. But what you see in front
• 24:39
  Speaker 1: of you is this big black circle, this shadow of
• 24:42
  Speaker 1: the black hole that's like two and a half times
• 24:45
  Speaker 1: the size of the actual event horizon, and you'll see
• 24:48
  Speaker 1: it be all black. And why is that? Why is
• 24:51
  Speaker 1: the black circle that I see bigger than the actual
• 24:53
  Speaker 1: black circle of the black hole Because anywhere in that
• 24:56
  Speaker 1: black shadow there's no path for light to get to
• 24:59
  Speaker 1: your eye. Is like if you traced it backwards, if
• 25:02
  Speaker 1: you started from your eyeball and trace the path of light,
• 25:05
  Speaker 1: that light would always end up in the black hole. So,
• 25:07
  Speaker 1: for example, what you're looking at when you look straight
• 25:10
  Speaker 1: at the heart of the black hole is the black hole,
• 25:13
  Speaker 1: and no light comes from there, obviously, so you see black.
• 25:16
  Speaker 1: But if you look above the edge of the black hole,
• 25:18
  Speaker 1: like larger than the rays the black hole, then the
• 25:21
  Speaker 1: light would come from the back of the black hole
• 25:23
  Speaker 1: and then curve around the black hole to your eye.
• 25:26
  Speaker 1: So what you're actually seeing there is sort of the
• 25:28
  Speaker 1: path light would take to get to the back of
• 25:30
  Speaker 1: the black hole, but again, no light is emitted from
• 25:33
  Speaker 1: the back of the black hole. Yeah, so that means
• 25:35
  Speaker 1: that I'm actually seeing kind of the back of the
• 25:37
  Speaker 1: black hole right like above the actual black hole. I'm
• 25:41
  Speaker 1: actually seeing the back of it because it's sort of
• 25:44
  Speaker 1: the light gets distorted from the back around the black
• 25:47
  Speaker 1: hole and onto my eye. It's sort of like a
• 25:50
  Speaker 1: lens like it's being magnified in three D exactly. Another
• 25:55
  Speaker 1: way to think about it is put a star on
• 25:57
  Speaker 1: the other side of the black hole, like a really
• 25:59
  Speaker 1: bright star. Would you see it's light creeping over the
• 26:02
  Speaker 1: edge of the event horizon. The answer is no, because
• 26:05
  Speaker 1: those photons would get bent down and then sucked into
• 26:08
  Speaker 1: the black hole. Even if they don't hit the event horizon.
• 26:11
  Speaker 1: As they pass over it, the black hole curves their path,
• 26:14
  Speaker 1: It slurps them down, and they get sucked into the
• 26:17
  Speaker 1: black hole eventually, so you don't see that light. So
• 26:20
  Speaker 1: the first light that you could see, the light that
• 26:22
  Speaker 1: would survive being passed to your eyes is about two
• 26:25
  Speaker 1: and a half times the event horizon. That's why we
• 26:28
  Speaker 1: talked about seeing an image of the black hole. It's
• 26:31
  Speaker 1: not the literal black hole itself. It's a distortion of
• 26:33
  Speaker 1: the space that makes it look bigger. It's like a mirrage,
• 26:37
  Speaker 1: like it's the black hole is pretending to be bigger
• 26:39
  Speaker 1: than it is. That's right. It's like a black cat
• 26:42
  Speaker 1: that's gotten really mad, and it's like and it posts
• 26:45
  Speaker 1: up and post itself up. Yeah, there you go. Black
• 26:48
  Speaker 1: cats black holes both are bad luck if they cross
• 26:51
  Speaker 1: your path, that's right. And so maybe the black hole
• 26:54
  Speaker 1: is more scared of us than we are of it.
• 26:56
  Speaker 1: The black hole is full of black cats, which case,
• 26:59
  Speaker 1: they will tear you apart. Also, I think we just
• 27:02
  Speaker 1: figured out we just answered the deepest question about quantum
• 27:05
  Speaker 1: gravity right there. All right, So I see the shadow
• 27:08
  Speaker 1: and now but now I'm getting closer, even closer than
• 27:12
  Speaker 1: the shadow, or can I enter the shadow? Well, as
• 27:14
  Speaker 1: you get closer this shadow, this circle of black that
• 27:17
  Speaker 1: you see in front of you, it starts out like
• 27:19
  Speaker 1: two and a half times the rays of the black hole,
• 27:21
  Speaker 1: it just gets bigger and bigger in your field of view.
• 27:24
  Speaker 1: And not just because you're getting closer to it, but
• 27:26
  Speaker 1: because the distortion of space is magnifying it more and more. Right,
• 27:30
  Speaker 1: So as you get closer and closer to it, it
• 27:32
  Speaker 1: sort of grows and takes up more and more of
• 27:35
  Speaker 1: your field of view, and it gets bigger and bigger
• 27:38
  Speaker 1: and bigger. But there is awesome stuff that happens even
• 27:41
  Speaker 1: before you get to the event horizon. Yeah, what happened. Well,
• 27:44
  Speaker 1: once you get to like one and a half times
• 27:46
  Speaker 1: the event horizon, this is the last point where light
• 27:49
  Speaker 1: can orbit the black hole stably. Remember the event horizon
• 27:53
  Speaker 1: is where light pointed outwards can't escape the black hole.
• 27:57
  Speaker 1: But even before that, light pointed inwards won't just gave
• 28:00
  Speaker 1: the black hole. Right, If you're two times the size
• 28:02
  Speaker 1: of the event horizon and you shine a flashlight into
• 28:04
  Speaker 1: the black hole, boom, it's going to get slurped in. Now,
• 28:07
  Speaker 1: if you're one and a half times the event horizon
• 28:09
  Speaker 1: and you shine a flashlight sideways so that it's not
• 28:12
  Speaker 1: going towards or away from the black hole, and that
• 28:15
  Speaker 1: light has just enough power to bend all the way
• 28:18
  Speaker 1: around the black hole and come back and hit you
• 28:20
  Speaker 1: in the back of the head. What light can orbit
• 28:25
  Speaker 1: a black hole? But light has no mass. Light has
• 28:28
  Speaker 1: no mass. But remember space is curved, and light doesn't
• 28:31
  Speaker 1: move in straight lines. It moves in the shortest path.
• 28:34
  Speaker 1: And what gravity is is the bending of space, which
• 28:38
  Speaker 1: changes effectively what is the shortest path between two things?
• 28:42
  Speaker 1: Like the reason that the Earth is going around the
• 28:44
  Speaker 1: Sun is not because the Earth has mass, but because
• 28:46
  Speaker 1: the Sun has bent the shape of space. So it's
• 28:49
  Speaker 1: more natural for this Earth to go in this circle.
• 28:52
  Speaker 1: And so light also can follow these curved paths when
• 28:55
  Speaker 1: space is bent. We see that all the time in
• 28:57
  Speaker 1: gravitational lensing, etcetera. And so what how upens here is
• 29:00
  Speaker 1: light essentially is orbiting the black hole. So if you
• 29:03
  Speaker 1: shine a flashlight, it will illuminate the back of your
• 29:06
  Speaker 1: own head, or if you don't have a flashlight, you
• 29:08
  Speaker 1: look out and you'll see photons from the back of
• 29:11
  Speaker 1: your own head. Whoa I've always wanted to know at
• 29:14
  Speaker 1: the back of my head looks like And you can't
• 29:16
  Speaker 1: just ask somebody around you. You have to take a
• 29:18
  Speaker 1: field chip to the black hole. That's the most efficient
• 29:20
  Speaker 1: way just to find that. It's easier than putting you
• 29:25
  Speaker 1: a couple of mirrors. And so at that point, any
• 29:28
  Speaker 1: light that's pointed at all towards the black hole will
• 29:31
  Speaker 1: fall in. Any light that's pointed perfectly tangent to the
• 29:34
  Speaker 1: black hole will orbit, and any light that is pointed
• 29:36
  Speaker 1: at all out will still escape. It needs some angle
• 29:40
  Speaker 1: away from the black hole to escape, but it's still possible.
• 29:43
  Speaker 1: So this is the point of no return for almost
• 29:47
  Speaker 1: like for for light in a way, Yeah, as you
• 29:50
  Speaker 1: get closer, light can still escape if it's pointed further
• 29:53
  Speaker 1: and further out, And as you get closer and closer,
• 29:55
  Speaker 1: the event horizon is a point at which even light
• 29:58
  Speaker 1: pointed straight out from the black hole can no longer
• 30:01
  Speaker 1: get out. But the angle for light to escape gets
• 30:04
  Speaker 1: smaller and smaller as you get closer and closer to
• 30:06
  Speaker 1: the event horizon, until eventually it disappears. All right, So
• 30:09
  Speaker 1: then I've satisfied my curiosity. I know what the back
• 30:12
  Speaker 1: of my head looks like, finally, And then what happens
• 30:14
  Speaker 1: as I go in further than one and a half
• 30:16
  Speaker 1: times the radius of the black hole. Well, it's pretty
• 30:19
  Speaker 1: cool because this shadow, which has become bigger and bigger,
• 30:22
  Speaker 1: grows and grows and grows, and eventually it's even taking
• 30:26
  Speaker 1: up more than half of your vision. All right. If
• 30:28
  Speaker 1: you imagine yourself sort of at the center of a sphere,
• 30:31
  Speaker 1: you can look all around you. The black hole starts
• 30:33
  Speaker 1: out at one point of it, and as you get
• 30:35
  Speaker 1: closer and closer, it fills up more of that sphere,
• 30:38
  Speaker 1: and then it takes up even more than half of
• 30:40
  Speaker 1: that sphere. So you're not yet inside the event horizon,
• 30:44
  Speaker 1: but the distortion of light makes it look like it's
• 30:47
  Speaker 1: sort of eating you. It's like all around you, behind you,
• 30:50
  Speaker 1: you can still see out to the universe, but a
• 30:53
  Speaker 1: head of you and sort of around you you see
• 30:55
  Speaker 1: just the black hole shadow and it's completely pitch black, right,
• 30:59
  Speaker 1: like there's you're seeing the black hole, which is completely black.
• 31:03
  Speaker 1: There's no stars or anything that's right. It's there's no stars,
• 31:06
  Speaker 1: there's nothing there because everything that has fallen into the
• 31:09
  Speaker 1: black hole is ahead of you and cannot radiate towards you. Right,
• 31:13
  Speaker 1: Nothing that's inside the black hole can shoot anything in
• 31:16
  Speaker 1: your direction. The thing that remember is that black holes
• 31:19
  Speaker 1: change the shape of space, and inside the black hole,
• 31:22
  Speaker 1: space is sort of one directional. Every direction points towards
• 31:25
  Speaker 1: the center. And that's sort of beginning to happen now
• 31:28
  Speaker 1: as you approach the event horizon. So things that are
• 31:31
  Speaker 1: closer to the event horizon than you, they could still
• 31:34
  Speaker 1: send you a photon, like if a friend had jumped
• 31:36
  Speaker 1: in before you and he was sending flashlight pins back
• 31:39
  Speaker 1: to you. You could still see your friend, but the
• 31:41
  Speaker 1: black hole itself is not radiating anything else. But if
• 31:44
  Speaker 1: you turn around and you look at sort of the
• 31:46
  Speaker 1: shrinking window out to the rest of the universe, you
• 31:49
  Speaker 1: do see something pretty awesome. Yeah, I guess if it's
• 31:52
  Speaker 1: eating you up the blackness, it would be like going
• 31:54
  Speaker 1: into a tunnel and the entrance to the tunnel gets
• 31:57
  Speaker 1: smaller and smaller. Yes, it's exactly like going into a
• 31:59
  Speaker 1: tunnel and that engines gets smaller and smaller. Except when
• 32:02
  Speaker 1: you look at from a tunnel, you can only see
• 32:04
  Speaker 1: sort of light that shoots straight into the tunnel. But here,
• 32:07
  Speaker 1: if you look back where you came from, you can
• 32:09
  Speaker 1: see every direction. You can see the whole universe. Advantage
• 32:13
  Speaker 1: point from the black hole. You can see from the
• 32:15
  Speaker 1: other side of the black hole. Right, it'd be like
• 32:18
  Speaker 1: a super powerful fish eye lens that let's you see
• 32:21
  Speaker 1: everything in a small view. That's right, because things like
• 32:24
  Speaker 1: that are on the other side of the black hole.
• 32:26
  Speaker 1: Their light can bend around the black hole and then
• 32:29
  Speaker 1: come back and hit your eyeball. So the black hole
• 32:32
  Speaker 1: while it's about to eat you, is also still giving
• 32:34
  Speaker 1: you like a three hundred and sixty degree view of
• 32:37
  Speaker 1: the universe because of all this distortion. You wow. And
• 32:40
  Speaker 1: so it's a shrinking view two, right, Like, as I
• 32:42
  Speaker 1: moved towards the black hole, the actual radius of the
• 32:45
  Speaker 1: actual edge of the black hole, that view is going
• 32:47
  Speaker 1: to be shrinking and shrinking and shrinking, and then eventually
• 32:50
  Speaker 1: what it disappears and becomes a dot. Yeah, And as
• 32:52
  Speaker 1: you move further and further in your window to the
• 32:55
  Speaker 1: universe shrinks and eventually becomes a tiny dot. Right, Because
• 33:00
  Speaker 1: think about it. If you're at the event horizon and
• 33:01
  Speaker 1: you're looking out, the only way for light to escape
• 33:05
  Speaker 1: is to go straight out from the event horizon any
• 33:08
  Speaker 1: other angle and it's gone, which means if you invert that,
• 33:12
  Speaker 1: like coming at any other angle has to have come
• 33:14
  Speaker 1: from the black hole. So you're gonna see all black
• 33:17
  Speaker 1: except for one dot. And in that dot is a
• 33:20
  Speaker 1: picture of the entire universe compressed into a tiny little image.
• 33:24
  Speaker 1: Oh man, And then you're inside the black hole. And
• 33:27
  Speaker 1: then you're inside the black hole, and take careful notes,
• 33:29
  Speaker 1: because I want to hear all about it. All right,
• 33:31
  Speaker 1: let's talk about what is actually happening to you as
• 33:34
  Speaker 1: you go into the event horizon. But first let's take
• 33:37
  Speaker 1: another quick break. All right, Daniel, we are answering the
• 33:52
  Speaker 1: deepest questions of the universe right now, which is that
• 33:56
  Speaker 1: inside of the event horizon of a black hole, the
• 33:59
  Speaker 1: universe has disappeared behind me into a dot. Now I
• 34:03
  Speaker 1: am inside of a black hole. What's happening to me?
• 34:07
  Speaker 1: So we don't know. We don't know what's inside a
• 34:09
  Speaker 1: black hole. We don't know like the structure of matter.
• 34:12
  Speaker 1: Is there really a singularity at its core? Is there
• 34:15
  Speaker 1: something else weird going on? We're pretty sure a singularity
• 34:18
  Speaker 1: can't be right because it's an infinity, and we don't
• 34:21
  Speaker 1: think that those things actually exist in nature. That's what
• 34:24
  Speaker 1: general relativity predicts. Though general relativity also breaks down at
• 34:27
  Speaker 1: the singularity, can't make any real predictions. So we don't know.
• 34:31
  Speaker 1: But we could just sort of like assume that general
• 34:33
  Speaker 1: relativity is right and talk about what it would be
• 34:35
  Speaker 1: like to go into a general relativistic black hole. Well,
• 34:39
  Speaker 1: it only breaks down at the very center, right, That's right,
• 34:42
  Speaker 1: we think, So you know, up until you get to
• 34:44
  Speaker 1: the center, we you can sort of predict what's going
• 34:46
  Speaker 1: to happen. Yeah, if general relativity just needs like a
• 34:48
  Speaker 1: small modification, if it means like, okay, general relativity is
• 34:52
  Speaker 1: right about most of the black holes, just at the core.
• 34:54
  Speaker 1: It doesn't quite get the singularity right, and it gets
• 34:57
  Speaker 1: like fuzzed out by quantum mechanics. Maybe, but it could
• 35:00
  Speaker 1: be that we're totally wrong and that what's inside a
• 35:02
  Speaker 1: black hole is completely different and a huge surprise, and
• 35:05
  Speaker 1: quantum gravity is something totally unexpected. We just don't know,
• 35:09
  Speaker 1: we can't see, which is frustrating. But yeah, we can
• 35:12
  Speaker 1: imagine that there's some sort of singularity the core, and
• 35:14
  Speaker 1: then we could talk about what it's like then to
• 35:16
  Speaker 1: cross the event horizon and dive in. Right, we can
• 35:19
  Speaker 1: just assume e signs right. I mean a guy, he's
• 35:22
  Speaker 1: gotten some things, right, He had a couple of big hits.
• 35:26
  Speaker 1: He's got a pretty good track record. Yeah, so let's
• 35:28
  Speaker 1: go with Einstein is right and think about what would
• 35:30
  Speaker 1: be like to fall into the black hole. And again,
• 35:33
  Speaker 1: the most important thing to remember is that once you're
• 35:35
  Speaker 1: inside the black hole, space is now one directional. That
• 35:39
  Speaker 1: means it's not just like gravity is pulling you really
• 35:42
  Speaker 1: hard and you can't manage to escape. If you could
• 35:45
  Speaker 1: just go faster than the speed of light, it means
• 35:47
  Speaker 1: that every path moves towards the center of the black hole.
• 35:51
  Speaker 1: It's weird to think about space being one directional, but
• 35:54
  Speaker 1: think about the way you think about time time very
• 35:56
  Speaker 1: naturally think of as one directional. Outside a black hole,
• 36:00
  Speaker 1: time is one directional, moves forwards. Inside a black hole,
• 36:03
  Speaker 1: space is one directional and moves towards the center. Right,
• 36:07
  Speaker 1: But that's the ending is only because you can't go
• 36:10
  Speaker 1: faster than the speed of light. If you could go
• 36:12
  Speaker 1: faster than the speed of light, you could sort of
• 36:15
  Speaker 1: come out of that space. Right. Oh man, It's like
• 36:17
  Speaker 1: relativity says you can't escape a black hole and that
• 36:21
  Speaker 1: you can't go fast in the speed of light. So
• 36:23
  Speaker 1: what would happen if you believed relativity about one thing
• 36:26
  Speaker 1: but ignored it about the other thing. I'm not sure
• 36:29
  Speaker 1: that would sort of break the fundamental assumption of relativity.
• 36:32
  Speaker 1: You would break into thine. All right, Well, I guess
• 36:36
  Speaker 1: one thing that's interesting to note is what happens when
• 36:39
  Speaker 1: you actually cross the event horizon, Like when you step
• 36:43
  Speaker 1: through that point where light can escape. You know, what
• 36:47
  Speaker 1: actually happens to me as I go in. Yeah, And
• 36:50
  Speaker 1: the surprising thing is if you've picked a large black
• 36:53
  Speaker 1: hole where the tidal forces are not going to pull
• 36:55
  Speaker 1: you apart, the event horizon is not a special place.
• 36:58
  Speaker 1: It's not like there's a fire our wall, or there's
• 37:00
  Speaker 1: a gate, or there's dragons or anything right there. It's
• 37:04
  Speaker 1: just the point at which light can no longer escape.
• 37:07
  Speaker 1: And so your view the universe continues to shrink, and
• 37:09
  Speaker 1: you see more and more blackness around you. And that's
• 37:12
  Speaker 1: because every path for you, every future direction of yours,
• 37:16
  Speaker 1: is towards the center of the black hole, which of
• 37:18
  Speaker 1: course isn't emitting anything and looks black. So that's the
• 37:22
  Speaker 1: only thing that happens as you cross the event horizon.
• 37:25
  Speaker 1: No fireworks, no craziness, just sort of a ceiling of
• 37:28
  Speaker 1: your fate. And so then what I would experience is
• 37:32
  Speaker 1: just pure darkness. Right according to general relativity, I wouldn't
• 37:38
  Speaker 1: see any flashes of light or Matthew McConaughey and a
• 37:41
  Speaker 1: you know, premidal kind of space talking to his daughter.
• 37:45
  Speaker 1: Depends on if you believe in the power of love rhead, Yeah,
• 37:48
  Speaker 1: the fifth dimension. Yeah, to like, what according to general alativity,
• 37:53
  Speaker 1: what would I see if anything, would I just see
• 37:56
  Speaker 1: stuff continuing to fall into the black hole or what?
• 38:00
  Speaker 1: You can't see anything that's in front of you, right,
• 38:02
  Speaker 1: because even if stuff has fallen into the black hole
• 38:05
  Speaker 1: before you, it's ahead of you and it can't emit
• 38:07
  Speaker 1: light in your direction, so you just see blackness ahead
• 38:11
  Speaker 1: of you. The only light you could see while you're
• 38:14
  Speaker 1: inside the black hole is from things behind you. If
• 38:17
  Speaker 1: you're not traveling at the speed of light, then someone
• 38:19
  Speaker 1: outside the black hole can still be shooting a laser
• 38:22
  Speaker 1: at you that could catch up to you in that
• 38:25
  Speaker 1: remaining little tunnel from the outside universe, so you still
• 38:29
  Speaker 1: can't see a little dot. Otherwise, all around you is
• 38:32
  Speaker 1: just the blackness, a view of the singularity. But that's
• 38:35
  Speaker 1: assuming that your brain still works. Right. We talked about
• 38:39
  Speaker 1: spaghetification and the tidal forces tearing you apart, but we
• 38:42
  Speaker 1: don't even know if your mind, if your brain could work,
• 38:45
  Speaker 1: if space becomes one directional, because you know, your brain
• 38:48
  Speaker 1: relies on nervous signals, which go forwards and backwards and
• 38:52
  Speaker 1: sideways and all around, and the space is one directional,
• 38:55
  Speaker 1: could your blood even pump, could your nerves even fire? Right?
• 38:59
  Speaker 1: You couldn't have a thought that goes from the front
• 39:01
  Speaker 1: of your head to the back of your head, right, exactly, exactly,
• 39:05
  Speaker 1: Nothing can move further from the center of the black
• 39:08
  Speaker 1: hole because space is just one directional and so it's
• 39:10
  Speaker 1: hard to imagine how your body could be configured in
• 39:12
  Speaker 1: a way that you would actually even survive. What would
• 39:15
  Speaker 1: my body hold together? Even? Technically, yes, right, technically, yes,
• 39:19
  Speaker 1: the gravitational title forces near the edge of the event horizon,
• 39:22
  Speaker 1: a big black hole would not be enough to tear
• 39:24
  Speaker 1: you apart, so it wouldn't pull you into pieces. But
• 39:28
  Speaker 1: I don't think you could function very well. I mean,
• 39:30
  Speaker 1: your body would have to be reorganized in a way
• 39:33
  Speaker 1: so that things just flow in one direction. And so
• 39:36
  Speaker 1: you know, like if your blood is getting pumped away
• 39:38
  Speaker 1: from your heart, it's never returning to your heart, And
• 39:40
  Speaker 1: that doesn't sound like the recipe for a long life.
• 39:43
  Speaker 1: Well what if I was just thinking, like, could be
• 39:45
  Speaker 1: blood go from your heart to the back of your head?
• 39:48
  Speaker 1: Still if your head moves faster than the blood, like
• 39:51
  Speaker 1: you could you still have circulation that way? Like? Could
• 39:54
  Speaker 1: parts of my body accelerate more than the other parts,
• 39:56
  Speaker 1: which means they do go to the back of my head?
• 39:58
  Speaker 1: I think that your motion here would be ondly dominated
• 40:00
  Speaker 1: by the gravitational forces of the black hole, which would
• 40:03
  Speaker 1: swamp everything else. And so I think practically it would
• 40:06
  Speaker 1: be impossible to counter that and be like, you know,
• 40:09
  Speaker 1: taking a jump on a super supermassive planet is basically impossible.
• 40:13
  Speaker 1: And here we're talking about gravitational forces, which, even though
• 40:15
  Speaker 1: they're not strong enough to pull you apart yet, are
• 40:17
  Speaker 1: still very very strong. And you have nothing to push against, right,
• 40:21
  Speaker 1: so how are you going to accelerate your head relative
• 40:23
  Speaker 1: to the rest of your body. Well, it'd be like,
• 40:25
  Speaker 1: you know, in a super heavy planet, it's hard to
• 40:27
  Speaker 1: jump from the surface, But if I'm falling towards a
• 40:30
  Speaker 1: giant planet, you could still jump off of the inside
• 40:34
  Speaker 1: of your spacehip. Yeah. I suppose if you brought something
• 40:36
  Speaker 1: along to push against, then you could relatively change your
• 40:41
  Speaker 1: acceleration compared to that object. So you bring like a
• 40:45
  Speaker 1: huge bag of bananas and you start throwing them into
• 40:47
  Speaker 1: the center of the black hole, then you would change
• 40:49
  Speaker 1: your acceleration relative to those things. Yeah, so you could
• 40:53
  Speaker 1: maybe still have thoughts as you go in if each
• 40:56
  Speaker 1: of your little blood molecules throws tiny bananas and just
• 41:00
  Speaker 1: the right direction, then they could continue to park because
• 41:03
  Speaker 1: that the idea. Then you'd be glad you ate a
• 41:05
  Speaker 1: bunch of bananas before you went in. We've just proved it, folks.
• 41:08
  Speaker 1: Bananas will save you inside a black hole. They do
• 41:12
  Speaker 1: help you think. Alright, So, um, I would not see
• 41:16
  Speaker 1: a lot of interesting things, but maybe I would experience
• 41:19
  Speaker 1: something different, you know, like how would you you said
• 41:23
  Speaker 1: I might discover the secrets of the universe inside? Would
• 41:26
  Speaker 1: I see them, feel them or what I need to
• 41:28
  Speaker 1: like bring in an experiment with me. Yeah, well, we
• 41:31
  Speaker 1: don't know, because we don't know what you would see.
• 41:33
  Speaker 1: You can imagine, you know, what would it be like
• 41:35
  Speaker 1: under various scenarios, like if the singularity is real? Well, unfortunately,
• 41:39
  Speaker 1: there's no way you survive getting that close. I mean,
• 41:41
  Speaker 1: we talked about picking a black hole that's big enough
• 41:44
  Speaker 1: to cross the event horizon. But definitely, at some point
• 41:47
  Speaker 1: if you get close enough to a singularity, that title
• 41:49
  Speaker 1: forces will shred you and so you just cannot survive.
• 41:53
  Speaker 1: But imagine then you had some like super duper strong
• 41:56
  Speaker 1: probe that was strong enough to resist that sort of
• 41:58
  Speaker 1: crushing force and it could get closer. Well, it doesn't
• 42:01
  Speaker 1: really matter because the closer you get to singularity, there's
• 42:04
  Speaker 1: always more singularity ahead of you, or the singularity is
• 42:07
  Speaker 1: a point of infinite density, so you can't be like
• 42:10
  Speaker 1: in it. You can't be past some of it. There's
• 42:12
  Speaker 1: always space between you and it, and that space gets
• 42:15
  Speaker 1: smaller and smaller and smaller, sort of like Zeno's paradox,
• 42:18
  Speaker 1: and the gravitational force gets greater and greater and greater
• 42:21
  Speaker 1: until it grows to infinity. But you can't like be
• 42:24
  Speaker 1: inside of it or in part of it. It's a
• 42:26
  Speaker 1: tiny infinitesimal dot. You'ld only just see blackness ahead of
• 42:30
  Speaker 1: you unless quantum mechanics is right, and that singularity isn't
• 42:34
  Speaker 1: actually infinite. If it exists in some sort of finite
• 42:37
  Speaker 1: space it's like fuzzed over by the Heisenberg uncertainty principle,
• 42:41
  Speaker 1: and it's a little bit larger, then it might be
• 42:43
  Speaker 1: possible to like interact with that in some way, or
• 42:45
  Speaker 1: to see it like talking to other parts of the singularity. Well,
• 42:48
  Speaker 1: but even if it was fuzzy in the middle, it
• 42:52
  Speaker 1: would still tear you apart at some point, right, it
• 42:54
  Speaker 1: would tear you apart before you got anywhere close enough
• 42:57
  Speaker 1: to do any physics experiments. But you know, if you
• 42:59
  Speaker 1: had some really powerful probe, they could get even closer
• 43:02
  Speaker 1: than because the quantum singularity might have some actual spatial extent.
• 43:07
  Speaker 1: There might be as small window in there for you
• 43:09
  Speaker 1: to do some experiments and actually measure it. But I
• 43:11
  Speaker 1: think even before then, it would be fascinating just to
• 43:14
  Speaker 1: map out the gravity as a function of the radius.
• 43:16
  Speaker 1: See like how does the gravitational intensity change or the
• 43:19
  Speaker 1: curvature space change as you get closer and closer to
• 43:22
  Speaker 1: the black hole center. That could have some surprises. You
• 43:24
  Speaker 1: could like measure the gravity in your hands as opposed
• 43:27
  Speaker 1: to the gravity your feet, and that might tell you
• 43:29
  Speaker 1: whether or not general relativity is working. Yeah, they're doing
• 43:33
  Speaker 1: lots of really cool tests of general relativity, and right now,
• 43:36
  Speaker 1: from the outside of black holes, they're watching gas swirl
• 43:39
  Speaker 1: and they're asking, does it swirl at the velocity we expect?
• 43:42
  Speaker 1: And they're using that essentially to measure the gravitational force
• 43:44
  Speaker 1: just past the edge of the black hole, because they
• 43:47
  Speaker 1: can't measure it on the inside, which is what they
• 43:48
  Speaker 1: would actually love to do. So if you're inside the
• 43:51
  Speaker 1: black hole, you can measure those forces of gravity, and
• 43:54
  Speaker 1: then you could understand something about what's happening at the
• 43:56
  Speaker 1: center just from the gravitational twisting and the tweaking of
• 43:59
  Speaker 1: the gravitation forces inside the black hole, you can see like,
• 44:02
  Speaker 1: is its spinning? Maybe the singularity is a ring and
• 44:05
  Speaker 1: it's actually spinning, or maybe it's just the dot. So
• 44:07
  Speaker 1: you could learn something about its structure by taking more
• 44:09
  Speaker 1: detailed measurements of the gravitational force as a function of
• 44:12
  Speaker 1: the distance from the center. Now, Daniel, would that be
• 44:15
  Speaker 1: worth it for you to learn that and never come back,
• 44:19
  Speaker 1: because I mean it doesn't sound like you know, the
• 44:22
  Speaker 1: universe would reveal, so you would just sort of confirmed
• 44:25
  Speaker 1: this one part of general relativity. Would that be worth
• 44:27
  Speaker 1: it for you? Or there could be a surprise. Right,
• 44:29
  Speaker 1: this is just two ideas humans have had, and we
• 44:32
  Speaker 1: don't think either of them is right. Was waiting inside
• 44:34
  Speaker 1: a black hole could be something totally different. It could
• 44:37
  Speaker 1: be a portal to another place in the universe, right,
• 44:39
  Speaker 1: a wormhole? It could be something completely surprising that unexpected.
• 44:43
  Speaker 1: I mean, think about how much of a surprise relativity
• 44:46
  Speaker 1: was or quantum mechanics, and now we're talking about something
• 44:49
  Speaker 1: which fuses and changes both of them, and so that
• 44:52
  Speaker 1: could be a surprise on the same scale or even
• 44:54
  Speaker 1: grander than the intellectual leap required to absorb those and
• 44:58
  Speaker 1: so yeah, I'm thirsty for that kind of realization. Sign
• 45:01
  Speaker 1: me up right. Well, but you wouldn't be able to
• 45:03
  Speaker 1: tell anyone, right because you're inside of the black hole.
• 45:06
  Speaker 1: But I would know you would be the only human
• 45:08
  Speaker 1: not to know this information and you wouldn't be able
• 45:12
  Speaker 1: to tell anyone. Would you still want to know if
• 45:14
  Speaker 1: you couldn't tell anyone, Well, since nobody's ever going to
• 45:16
  Speaker 1: call my bluff, I can confidently say yes, I would
• 45:19
  Speaker 1: want to know, because for me, physics isn't about like
• 45:22
  Speaker 1: finding it out and writing the paper. It's about knowing.
• 45:24
  Speaker 1: It's about that moment when you're asking nature a question
• 45:28
  Speaker 1: and forcing nature to reveal the answer, to extracting some
• 45:31
  Speaker 1: piece of information about the universe and just knowing it
• 45:34
  Speaker 1: because remember, science is about people's individual curiosity and this
• 45:38
  Speaker 1: is mine. All right, Well, it sounds like it's possible
• 45:43
  Speaker 1: to go into a black hole and discover some secrets
• 45:45
  Speaker 1: of the universe and actually survive, and it would be
• 45:48
  Speaker 1: pretty interesting and pretty mind and light bending to do it. Yeah,
• 45:53
  Speaker 1: I think that's something that surprises a lot of people
• 45:55
  Speaker 1: is that as you fall into the black hole is
• 45:57
  Speaker 1: sort of like nothing there. I mean, you get torn
• 45:59
  Speaker 1: apart by the ay, but there's no like threshold of
• 46:01
  Speaker 1: the event horizons, no trumpets that play, and you just
• 46:04
  Speaker 1: sort of fall right on in. Now, it's a different
• 46:07
  Speaker 1: story for people who are watching you jump into a
• 46:10
  Speaker 1: black hole. There's all sorts of weird relativistic effects there
• 46:13
  Speaker 1: as they see your time slowing down, even though for
• 46:16
  Speaker 1: you you can just fall right into the black hole
• 46:19
  Speaker 1: without noticing any effects on your clock. Wow, so it
• 46:23
  Speaker 1: would be a pretty smooth fall until it tears your
• 46:26
  Speaker 1: part inside of it. Yes, it would be pretty smooth
• 46:28
  Speaker 1: fall until you get torn into shreds. Better at your
• 46:31
  Speaker 1: spaghetti before you get to that point, then that's right.
• 46:34
  Speaker 1: How do you review that on Yelp? Would have been
• 46:36
  Speaker 1: five stars but got shredded and got turned into dinner
• 46:40
  Speaker 1: for the black hole? All right? Well, um, I think
• 46:44
  Speaker 1: it's you know, a part of a great exercise of
• 46:47
  Speaker 1: human evolution to imagine and to wonder what would be
• 46:51
  Speaker 1: like to do these crazy things in the universe. Absolutely,
• 46:54
  Speaker 1: and these are fun mind experiments because they sharpen our ideas.
• 46:58
  Speaker 1: They make us think what would it actually be. Let's
• 47:00
  Speaker 1: do the calculation. Let's think about what would happen to
• 47:03
  Speaker 1: somebody who jumped into a black hole. And hey, maybe
• 47:07
  Speaker 1: someday somebody's bluff will be called and they will actually
• 47:10
  Speaker 1: be transported to the edge of the event horizon and
• 47:12
  Speaker 1: encouraged to dive in to learn the answers some of
• 47:15
  Speaker 1: these deep questions about physics of the universe. And by somebody,
• 47:18
  Speaker 1: we mean you, Daniel, You're going to be the first one.
• 47:21
  Speaker 1: Because he said it on the record, We're throwing you in.
• 47:24
  Speaker 1: That's right. This is a legal statement right here. I
• 47:27
  Speaker 1: am bound by these statements. All right, Well, we hope
• 47:30
  Speaker 1: you enjoyed that little field trip inside of a black hole.
• 47:33
  Speaker 1: I hope you packed enough snacks. Thanks for joining us,
• 47:35
  Speaker 1: see you next time. Thanks for listening, and remember that
• 47:45
  Speaker 1: Daniel and Jorge Explain the Universe is a production of
• 47:48
  Speaker 1: I Heart Radio. For more podcast for my Heart Radio,
• 47:52
  Speaker 1: visit the I Heart Radio app, Apple Podcasts, or wherever
• 47:55
  Speaker 1: you listen to your favorite shows. No