Speaker 1: My World. Welcome to Stuff to Blow your Mind from
Speaker 1: how Stuff Works dot com. Hey, welcome to Stuff to
Speaker 1: Blow your Mind. My name is Robert Lamb and I'm
Speaker 1: Joe McCormick, and today is going to be part one
Speaker 1: of a multi part episode on on a topic that
Speaker 1: I know you came back from New York with a fever.
Speaker 1: For Robert, We're gonna be talking about black holes, that's right. Yeah,
Speaker 1: I attended, Uh, I attended a talk at the World
Speaker 1: Science Festival that I believe I mentioned in our previous
Speaker 1: sort of World Science Festival roundup episode that I just
Speaker 1: thought did a great job of providing an overview of
Speaker 1: black holes and uh help straighten out a few of
Speaker 1: the details for me. Yeah, I realized we have talked
Speaker 1: about black holes on the podcast before, but you haven't
Speaker 1: really I felt given it, given them proper, do We haven't.
Speaker 1: We haven't really uh looked at black holes with the
Speaker 1: attention that they deserve. Yeah, And of course, even in
Speaker 1: doing a multi part series, we're not gonna be able
Speaker 1: to cover every interesting thing about black holes. So this
Speaker 1: is gonna be kind of a grab bag of things
Speaker 1: that seemed interesting to us. So in this first episode,
Speaker 1: we're gonna be talking mainly about the history of the idea,
Speaker 1: where it came from, how we arrived at this bizarre
Speaker 1: conclusion about the cosmos that we live in. In the
Speaker 1: second episode, we're going to be focusing mainly on like
Speaker 1: how we get a look at these things. And in
Speaker 1: the third episode, I think we're gonna explore some of
Speaker 1: the strangest avenues of thought that you can contemplate with
Speaker 1: regard to black holes, like what's it like to fall
Speaker 1: into one? Or what happens when a black hole collapses?
Speaker 1: Does it does it create something on the inside? Yeah,
Speaker 1: And I want to acknowledge that black holes, I feel
Speaker 1: are kind of a challenging topic to tackle some people.
Speaker 1: I mean, certainly from a like a physics standpoint, yes,
Speaker 1: but but also just in terms of becoming engaged with
Speaker 1: the idea, because I know there are plenty of you
Speaker 1: out there like, yeah, black holes, let's do this. I
Speaker 1: love I love science I love science fiction. I think
Speaker 1: King of of all my favorite black hole related movies.
Speaker 1: But I know other people are a little hesitant because ultimately,
Speaker 1: black holes are a concept that have very little impact
Speaker 1: on our personal lives and the scope of the universe.
Speaker 1: That we observe and interact in. Well, they don't have
Speaker 1: any people in them, right. I mean a lot of times,
Speaker 1: I think when people look up to space and they say,
Speaker 1: you know, I want to be interested in it, but
Speaker 1: there's if there's no people up there, it's hard to
Speaker 1: feel like I'm following a story or narrative. Or can
Speaker 1: I even imagine a person there, because obviously there are
Speaker 1: no people on Mars. But I can, But I can
Speaker 1: imagine a future in which there are people on Mars.
Speaker 1: I can. I can imagine multiple different sci fi scenarios,
Speaker 1: many of which match up reasonably well with scientific expectations,
Speaker 1: and and that can allow me to engage myself in
Speaker 1: Mars more. But unfortunately, if you know anything about black holes,
Speaker 1: you know that it's not even possible to say colonies
Speaker 1: a black hole. You can't have singular and knots going
Speaker 1: in there to see what's on the inside. Or you could,
Speaker 1: but it just wouldn't be very useful for us on
Speaker 1: the outside, or I guess very useful for those getting
Speaker 1: ripped apart on the inside. Right. And I think another
Speaker 1: challenge with black holes is that when they have played
Speaker 1: a key role in science fiction and been made ultimately
Speaker 1: kind of relatable concepts. Uh, the films don't really do
Speaker 1: much with the science. They don't really do a great
Speaker 1: job about really conveying what a black hole is. For instance,
Speaker 1: I have to admit that my first introduction to black
Speaker 1: holes was the nineteen seventy nine Walt Disney sci fi
Speaker 1: movie The black Hole. Oh, Robert, I've never seen this one,
Speaker 1: but I'm excited. I'm excited for you to tell me
Speaker 1: about it. Tell me about it, fill my brain. All right,
Speaker 1: we'll just briefly. I'll try not to go on too
Speaker 1: long about this, because this is a film I loved
Speaker 1: as a child and I still look back on finally today.
Speaker 1: But it lands in a weird spot for a science
Speaker 1: fiction film because it's it's not as fun and original
Speaker 1: as nineteen seventy seven Star Wars, and of course it's
Speaker 1: nowhere near as high minded and scientifically savvy as ninety
Speaker 1: eight two thousand and one of Space Odyssey. But then again,
Speaker 1: you know what is Instead, it's kind of an old
Speaker 1: fashioned Jules Verne esque tale of space explorers who wind
Speaker 1: up on a space station that's circling a black hole,
Speaker 1: and the station's run by a mad scientist whose only
Speaker 1: attendance are robots and lowbottomized androids. There's ultimately some fairly
Speaker 1: horrific and and kind of ambitious stuff mixed in there,
Speaker 1: but you're also faced with just kind of a maximum
Speaker 1: dosage of of of of late seventies big budget cinema.
Speaker 1: Like all the actors you would expect to show up
Speaker 1: do show up. Ernest borg nine, Anthony Perkins, great, Maximilian
Speaker 1: Shell shows up as the villain. How about Harry Dean Stanton?
Speaker 1: Uh no, no, Dean Stanton, as I recall, And you
Speaker 1: also have one of the Bottoms brothers, timoth Bottoms, No, no,
Speaker 1: no one one of the other ones. Not not last
Speaker 1: picture was it last picture show? Yeah, less picture show, Yeah,
Speaker 1: not last picture shows bottoms, but but but one of
Speaker 1: the other ones some other bottoms yes, okay. And also
Speaker 1: slim pickings, slim pickings. Yeah, he's the voice of a
Speaker 1: robhid just busted up robot it had It is really
Speaker 1: cool robots in it. I gotta see this. The trailer
Speaker 1: is pretty great for it. H In fact, if we
Speaker 1: if we can play it, I would like to just
Speaker 1: throw in just a clip from this trailer. There is
Speaker 1: an inexorable force in the cosmos, where time and space converge,
Speaker 1: a place beyond men's vision but not to his reach.
Speaker 1: It is the most misdious and awesome point in the universe,
Speaker 1: whether here and now maybe forever. The black hole in
Speaker 1: this film, the actual black hole that we're presented with,
Speaker 1: it's it's it's presented like a vortex. It's it's more
Speaker 1: in keeping with the charybdis whirlpool of Greek myth. You know, this,
Speaker 1: this terrible thing that you're on the verge of falling into.
Speaker 1: It's ultimately treated with more religious reverence than scientific, which
Speaker 1: of course is pretty much what happens later on in
Speaker 1: the film Event Horizon, which I also love, but it's
Speaker 1: hardly a scientific tour to force. Were you watching Event
Speaker 1: Horizon recently, Robert, Yes, I was. I started watching it
Speaker 1: again last night, but only made it about ten minutes
Speaker 1: in before my ambient kicked in, because that's a horrible idea.
Speaker 1: It's it's not really not ten minutes end, because you
Speaker 1: get past the scary stuff and then you're just done
Speaker 1: a spaceship, and then you realize it's time to go
Speaker 1: to bed. I realized that the spaceship in that movie
Speaker 1: it's like the only leather punk spaceship I've ever seen
Speaker 1: in science fiction. It's like, you know, those like black
Speaker 1: leather wrist bands with the metal studs on them. It's
Speaker 1: that as a spaceship, it is very industrious, especially the uh,
Speaker 1: the core that you end up exploring. But but hopefully
Speaker 1: we'll get to talk about event Arizon a little bit
Speaker 1: more in one of the future episodes. But basically the
Speaker 1: idea is it's got a black hole and that's how
Speaker 1: you get to Hell. I think, yeah, which again is
Speaker 1: kind of the idea that has explored in Disney's a
Speaker 1: black Hole as well. So there's people in it, well,
Speaker 1: there are things in it, humanoids that you end up
Speaker 1: with characters traveling through it. It's ultimately the confusing part
Speaker 1: is that both films kind of treat a black hole
Speaker 1: more like a wormhole, which is a separate thing altogether,
Speaker 1: but that is ultimately more relatable I think to us
Speaker 1: the idea of like a magic tunnel that goes somewhere.
Speaker 1: But of course, actual black holes don't exist on a
Speaker 1: scale that that directly influences individual human life for life
Speaker 1: on Earth, except in our study of them. But the
Speaker 1: bottom line is that they're They're just a physical reality
Speaker 1: of our universe. They're not some sort of evil, malignant force.
Speaker 1: They are just a physical part of the universe. At
Speaker 1: the same time, though, I would say they are astounding
Speaker 1: and one of the most interesting things in the universe
Speaker 1: because they are the absolute extremists of of what we
Speaker 1: know about physics. They're sort of like the test cases.
Speaker 1: They're the exceptions. They break things that and that. For
Speaker 1: that reason, they're interesting to scientists because we can look
Speaker 1: at them and say, okay, what happens in these extreme
Speaker 1: cases where you know, where we can't necessarily see inside
Speaker 1: to know the answer. So at this point some of
Speaker 1: you might be asking, well, well, what is a black hole?
Speaker 1: Just lay lay out the basic definition. If it's not
Speaker 1: a wormhole, it's not a gateway to Hell, then then
Speaker 1: what are we talking about here? Well, in short, we're
Speaker 1: talking about regions of space where the gravity is so
Speaker 1: intense that light cannot escape the poll and the gravity
Speaker 1: is that intense because matter is compressed to a very
Speaker 1: small space and they range in size. For instance, primordial
Speaker 1: black holes are no larger than a single atom, but
Speaker 1: they contain the mass of a terrestrial Mount him So
Speaker 1: Mount everest crunched down to the side of an atom.
Speaker 1: It's pretty dense. A stellar black hole might be ten
Speaker 1: kilometers in diameter, but would boast the mass of twenty suns,
Speaker 1: for instance. And then finally you have the supermassive black hole. Uh,
Speaker 1: the types of black holes that that that that live
Speaker 1: at the centers of galaxies. Uh. And these would have
Speaker 1: the mass of millions of suns compressed to a sphere
Speaker 1: the size of a single solar system. That's extreme compression. Yeah,
Speaker 1: a little harder to even think about it. Like I
Speaker 1: find that the mountain atom uh comparison is maybe a
Speaker 1: little more impactful for the human imagination. But still we're
Speaker 1: talking about considerable, considerable consolidation of mass. Now we call
Speaker 1: them black holes because light cannot escape them. Optically, they
Speaker 1: appear as an absence. We can't see inside them, but
Speaker 1: we can observe the effect of say, of of this
Speaker 1: intense gravity on the surrounding environment. And despite the fact
Speaker 1: that we can't see inside them, as we'll talk about
Speaker 1: a couple of times as we go along, that doesn't
Speaker 1: necessarily mean we don't see anything around them. In fact,
Speaker 1: they can often put on quite a show. Yeah, I
Speaker 1: hate to lean into the horror movie implications here, but
Speaker 1: it's kind of like imagine the uh, the house from
Speaker 1: the Texas Chainsaw Mask. Here, you can't see any of
Speaker 1: the teenagers dying inside it from the outside, but you
Speaker 1: see them like moving towards the house. You see a
Speaker 1: lot of of random hippie activity on the outside, and
Speaker 1: it gives you an idea of what might be going
Speaker 1: on in the inside. Actually came up with an analogy
Speaker 1: I was going to use in the next episode, but
Speaker 1: maybe I'll go ahead and say it. So this is
Speaker 1: a little less grizzly than what you said, but kind
Speaker 1: of similar. So, uh, imagine you've got like a haunted
Speaker 1: house ride in an amusement park, and the ride, the
Speaker 1: part of the ride that you ride in is the
Speaker 1: soundproof box where nobody can hear anything on the outside.
Speaker 1: So you've got everybody in line to get in the ride,
Speaker 1: to get in the soundproof box and go through the
Speaker 1: haunted house. And as you're hurting tourists towards this soundproof box,
Speaker 1: even though you can't hear any of the screams inside
Speaker 1: the box, you will hear more and more sort of
Speaker 1: nervous chatter and laughter and shrieks as people are approaching
Speaker 1: the door, but then once you shut the door, bye bye.
Speaker 1: I like that we both independently came up with haunted
Speaker 1: house explanations for black holes. Personally, I seriously doubt that
Speaker 1: the Texas Chainsaw House is haunted or contains a black hole. Now,
Speaker 1: now it's important to note in all of this that
Speaker 1: I really think we should try and get away from
Speaker 1: thinking of black holes as essentially galactus or or some
Speaker 1: sort of other unstoppable, insatiable cosmic devour that just destroys
Speaker 1: and consumes everything, which is kind of hard because, as
Speaker 1: we've discussed before in the show, like that's a classic
Speaker 1: mythic trope, like the idea of some entity that will
Speaker 1: consume the Sun. I mean, it's key to these various
Speaker 1: eclipse mythologies that we've discussed in the past. But a
Speaker 1: black hole is not, uh, this thing is just going
Speaker 1: to eat the entire universe. They're bound by physics, so stars, planets,
Speaker 1: whole galaxies may orbit around them. And I've seen it
Speaker 1: pointed out before by NASA that if our Sun were
Speaker 1: a black hole of equal mass, the Earth would not
Speaker 1: fall in. Yeah, that's a point I've read many times before.
Speaker 1: So what would happen to the Earth if the Sun
Speaker 1: turned into a black hole? The Earth would keep orbiting. Yeah,
Speaker 1: So again, to come back to the Texas Chainsaw mascure House,
Speaker 1: it's it's not like the Texas Chainsaw Masscure House is
Speaker 1: just going to suck in everybody in the surrounding area
Speaker 1: and collapse the town. Now, the town continues to thrive. Yeah,
Speaker 1: the next door neighbors, they just keep going to work,
Speaker 1: they saying, keep selling barbecue. Everything's fine. And I also
Speaker 1: think again, the whole aspect of this is a stumbling
Speaker 1: block because it tends to encourage us to think of
Speaker 1: black holes less as what they presumably are and more
Speaker 1: like wormholes. Okay, so it's like it's like a tunnel
Speaker 1: you can go through. Yeah, yeah, But ultimately, a singularity
Speaker 1: is not a gateway. It doesn't go anywhere other than
Speaker 1: to the center of its gravity. Their celestial objects that
Speaker 1: just happened to be massive on a scale that's really
Speaker 1: harder to square with human experience. Well, I can tell already,
Speaker 1: Robert that you're running into issues with the language that
Speaker 1: we have to use to describe things, because there is
Speaker 1: no language, I mean, the only language we have is
Speaker 1: like normal terrestrial vocabulary, and then the metaphors we build
Speaker 1: out of that normal terrestrial vocabulary, so inevitably our language
Speaker 1: will ultimately fail to have words that, at a fundamental
Speaker 1: level really communicate the nature of celestial objects, you know,
Speaker 1: powerful objects, huge objects like black holes. So we we
Speaker 1: just have to use metaphors, right, and the idea of
Speaker 1: a black hole is a metaphor. Yeah, and it's it's
Speaker 1: a challenge for science communication for sure. A lot of
Speaker 1: great black hole studies come out, and then you look
Speaker 1: at the headlines that that are used right to to
Speaker 1: relate these findings, and it's it's I often get a
Speaker 1: laugh out of it because the world leader model is
Speaker 1: so often employed and you end up hearing reading about
Speaker 1: hannibal black holes, gobbling black holes, eating black holes, barfing
Speaker 1: black holes. Yeah, it's so anthropomorphised in a really visceral way.
Speaker 1: I mean you almost want to imagine that there are
Speaker 1: articles about dating black holes, swipe right black holes. But
Speaker 1: it's it's kind of a your damned if you do,
Speaker 1: your damned if you don't situation. It's kind of like
Speaker 1: when you when when we even anthropomorphize evolution to some extent,
Speaker 1: we treat it like a person, right, And I mean,
Speaker 1: on one hand, I acknowledge, yes, one should not do that.
Speaker 1: You fall into, you know, potential traps by doing it.
Speaker 1: But at the same time, you ultimately are trying to
Speaker 1: put some fairly complex ideas into a form that people
Speaker 1: can really consume. Well, you can talk about evolution without
Speaker 1: anthropomorphizing it or you know, treating it like a person
Speaker 1: with intentions. It's possible to do that. It can just
Speaker 1: get really tedious to constantly be talking that way. So
Speaker 1: we and we inevitably in these discussions, if we're just
Speaker 1: trying to move things long and you know, move at
Speaker 1: a brisk pace, we end up using the shorthand. And
Speaker 1: the same thing happens for black holes. Black holes, we
Speaker 1: end up using these colloquial shorthands to describe them that
Speaker 1: are based on Earth metaphors that don't really get at
Speaker 1: the truth of what it's like to have the geometry
Speaker 1: of space time warped by this gravitational anomaly. Now, one
Speaker 1: of the really fascinating things about black holes, though, is
Speaker 1: that we we simply we didn't simply look into the
Speaker 1: sky and observe them. Uh. It all began with the math.
Speaker 1: It began with with with some some very bright individuals
Speaker 1: crunching the numbers and seeing them as a possibility. Yeah,
Speaker 1: and that's one of the things that makes black holes
Speaker 1: so interesting. They weren't like stars. They weren't you know, stars.
Speaker 1: We could look up and know something was there, and
Speaker 1: then over time gradually make observations to refine our knowledge
Speaker 1: of what stars are. Right, black holes weren't like that.
Speaker 1: We had to work them out from first principles and
Speaker 1: then say, okay, is there a way we could observe them?
Speaker 1: It worked actually the opposite way. Yeah, that's the beautiful
Speaker 1: part we see because we see it paying off. We
Speaker 1: we we we we end up looking out into the
Speaker 1: cosmos and observing the very things that we have simulated
Speaker 1: with math and physics. The great astrophysicists Supermania and Chandra
Speaker 1: Sheker had in a prologue to his book The Mathematical
Speaker 1: Theory of black Holes, he wrote, quote, the black holes
Speaker 1: of nature are the most perfect macroscopic objects there are
Speaker 1: in the universe. The only elements in their construction are
Speaker 1: our concepts of space and time. All right, Well, on
Speaker 1: that note, we're gonna take a quick break, and when
Speaker 1: we come back. We are going to jump into the
Speaker 1: history of black holes. Thank you, thank alright, we're back.
Speaker 1: So previously we were just talking about how black holes
Speaker 1: began as an idea before they were observed in nature.
Speaker 1: They started as something that people worked out from principles
Speaker 1: they had established through other means, rather than something we
Speaker 1: looked up into the heavens and saw. And there's there's
Speaker 1: a really great book about this actually that I want
Speaker 1: to for two because it's one of the sources I
Speaker 1: used in working on this episode. But it's called black
Speaker 1: Hole by Marcia Bartoustiac, and it's a it's a book
Speaker 1: just about the history of the idea of the black hole,
Speaker 1: how it went from the idea of gravity to something
Speaker 1: that we now do experiments on with with cosmological detection equipment.
Speaker 1: So the story of the black hole can really be connected,
Speaker 1: I think, to the broader story of the discovery of gravity. Uh.
Speaker 1: You know, we often don't even bother to think anymore,
Speaker 1: why do objects fall down and not up? But I, oh,
Speaker 1: I sometimes wonder like do kids still have this thought?
Speaker 1: Do kids ask this sometimes or are they exposed to
Speaker 1: the theories we have of gravity before they even have
Speaker 1: the chance to ask that question naturally, you know, that's
Speaker 1: that's a great question, because I they certainly grasp the
Speaker 1: idea and the reality of gravity is just one of
Speaker 1: the realities of the natural world that they've evolved to
Speaker 1: thrive him. Of course we understand how it works, but
Speaker 1: why yeah, yeah, you know my own personal experience, I
Speaker 1: don't know that I've ever had a conversation with my
Speaker 1: son about gravity um or at least not when he
Speaker 1: was old enough to to appreciate it. I'm gonna have
Speaker 1: to make a mission of explaining it to him. But
Speaker 1: he also he may know already because he listens to
Speaker 1: to educational podcasts, so he when I mentioned black holes,
Speaker 1: he was like, oh, yeah, black holes. I was listening
Speaker 1: to a while in the world about black holes, so
Speaker 1: he already had a already had a leg up on
Speaker 1: the concept. Well, I mean, it's one of those things
Speaker 1: where most of us, I think, even people who are
Speaker 1: aware of general relativity, we sort of have the idea
Speaker 1: that we understand how gravity works, but then sit down
Speaker 1: and try to put into words like explain it, and
Speaker 1: then you start going, oh, wait a minute. But yeah,
Speaker 1: So it's one of those things that once you've heard
Speaker 1: it you think you've got to grasp on it, but
Speaker 1: even then it can prove tricky to try to explain yourself.
Speaker 1: But so you know, thousands or maybe millions of people
Speaker 1: must have stopped to wonder this all the time before
Speaker 1: we had a real answer why did things fall down
Speaker 1: instead of up? And for a long time I think
Speaker 1: humans were led astray by this intuitive, false cosmology of geocentrism.
Speaker 1: So if you believe, like Aristotle, that the Earth is
Speaker 1: the center of the universe, it makes a kind of
Speaker 1: intuitive sense that everything would fall toward the center, right
Speaker 1: And then again I sometimes wonder, like, why is that
Speaker 1: even intuitive? Why doesn't everything fall away from the center
Speaker 1: out to the edges. It just feels right enough that
Speaker 1: you can stop thinking about the question basically. But then
Speaker 1: once you introduce the Copernican model, the you know, the
Speaker 1: heliocentric model of the Solar system, and the idea that
Speaker 1: the Earth is not the center of the universe and
Speaker 1: in fact is no kind of privileged place at all.
Speaker 1: It's just another object floating around in space, Suddenly we
Speaker 1: really need an explanation for why objects fall to the
Speaker 1: ground rather than fly off in the opposite direction. And
Speaker 1: the bigger question. Is the force that causes objects to
Speaker 1: fall to the ground the same force that guides planets
Speaker 1: in their orbits around the Sun. I like what you
Speaker 1: said about the geocentric view because I think the geocentric
Speaker 1: view also kind of lines up with our aasic egoic
Speaker 1: experience of the world, Like everything in the world ultimately
Speaker 1: breaks down to what I feel about it, because I
Speaker 1: am the only the only experience, the only worldview you
Speaker 1: know that I that I have control of and one
Speaker 1: percent vision through. And uh. But then if someone would say, actually,
Speaker 1: you're not the most important person in the world. Is
Speaker 1: uh this person over here is that throws everything out
Speaker 1: of out of whack. Well, it makes you realize that
Speaker 1: your egoic view is not even necessarily a coherent view,
Speaker 1: is just something that you can do without having to
Speaker 1: think about. And I would argue the same is largely
Speaker 1: true for geocentric physics. Uh though actually, in a funny way,
Speaker 1: a lot of really intense thinking did go into constructing
Speaker 1: geocentric cosmologies and they look kind of beautiful. But anyway,
Speaker 1: coming back to gravity, so so we know that for example,
Speaker 1: Johannes Kepler suggested that the sun exerted a magnetic force
Speaker 1: that guided the orbits of the planets. Weird to think
Speaker 1: back to a time when they were thinking, Okay, how
Speaker 1: are the planets controlled in there? Or maybe it's magnetism.
Speaker 1: We know magnets exist, that's an attractive force. Maybe that's
Speaker 1: what controls it. And in the sixteen thirties, Descartes proposed
Speaker 1: that the orbits of the planets were guided by swirlings
Speaker 1: in the ether, which was this substance that was believed
Speaker 1: to occupy space. The ether would have been kind of
Speaker 1: like air water, this fluid that occupied empty space, and
Speaker 1: you could have whirlpools or cyclones guiding objects in a
Speaker 1: circular pattern around a center of motion, and that would
Speaker 1: be what would guide orbits in the ether. But then,
Speaker 1: of course we got to Newton. And so in sixteen
Speaker 1: seven Isaac Newton struck gold with the philosophy naturalists Principia Mathematica,
Speaker 1: or the Principia as people usually call it these days,
Speaker 1: and it established the mathematical principles that correctly describe gravity
Speaker 1: and planetary motion, which in effect turn out to be
Speaker 1: the same thing. The motion of the planets dis guided
Speaker 1: by momentum and gravity, and Newton calculated the inverse square
Speaker 1: law of gravity, meaning that as you move away from
Speaker 1: an object, it's gravitational influence is diminished by the square
Speaker 1: of the distance. So what does that mean. That means
Speaker 1: if you double the distance between two objects, the gravitational
Speaker 1: force between them is reduced to a fourth and if
Speaker 1: you quadruple the distance, the gravitational force between them is
Speaker 1: decreased to one sixteen. It's a square of the distance.
Speaker 1: So this indicates that the force of gravity is a
Speaker 1: constant force, spreading out equally in all three dimensions. And
Speaker 1: so a key insight that that Newton has that gravity
Speaker 1: is universal. It applies equally to the objects we drop
Speaker 1: and throw here on Earth, end of the objects we
Speaker 1: see in the night sky. Though it's worth pointing out
Speaker 1: at this stage that we still didn't know what gravity
Speaker 1: actually was other than this mutually attractive force between objects
Speaker 1: with mass. Newton wrote, actually, quote, I have not as
Speaker 1: yet been able to deduce from phenomena the reason for
Speaker 1: these properties of gravity, and I do not feign hypotheses.
Speaker 1: And so Newton's laws were widely accepted, especially after they
Speaker 1: were used to correctly predict the reappearing of Halley's comment
Speaker 1: and this leads us to an English natural philosopher, geologist, astronomer, mathematician,
Speaker 1: dabbler in mini domains named John Michelle. That's right, armed
Speaker 1: only with a Newtonian and obviously pre Einsteiny and understanding
Speaker 1: of gravity. Um. John Michelle and Henry Cavendish, Uh, contemplated
Speaker 1: some pretty big cosmological questions, including the scale of the
Speaker 1: universe and the cycle of stars. Yeah, they were really
Speaker 1: ahead of their time in a way. John Michelle for
Speaker 1: a long time was not necessarily recognized as one of
Speaker 1: the earliest people to think about black holes. But but
Speaker 1: he did some interesting work. Yeah. And and to put
Speaker 1: him in within a you know, you have the right
Speaker 1: time scale here. Uh. John Mitchell literally of seventeen and
Speaker 1: Cavendish lived seventeen through eighteen ten. Okay, so what was
Speaker 1: the deal? What? How did they touch on black holes? All? Right? So,
Speaker 1: even in their day, it was known that stars flared up,
Speaker 1: they subsided, and even vanished from the heavens. A popular
Speaker 1: theory of the day was that they had dark spots
Speaker 1: on them, you know, much like the spots that could
Speaker 1: be observed on our own sun, and that this would
Speaker 1: affect visibility. Though theories varied on what those dark spots
Speaker 1: were actually going to be. They might be dark valleys
Speaker 1: or ripples or peaks at a darker core underlying you know,
Speaker 1: outer fluid or gases, um scum, or rock like bodies.
Speaker 1: Even uh, there was all the star scum, yes, your
Speaker 1: star scum. And then there was this cool idea that
Speaker 1: that was also thrown around that you might have flattened stars.
Speaker 1: So these would have been I guess kind of like
Speaker 1: kind of like lenses rotating disks. Yeah, And so if it,
Speaker 1: depending on what how it was facing you, it would
Speaker 1: affect luminosity. So if it turned its edge to you,
Speaker 1: there would obviously be a lot less illumination. So it's
Speaker 1: not exactly the same principle, but I can see that
Speaker 1: being an interesting inside preceding the discovery of things like pulsars.
Speaker 1: So they pondered the structure of the cosmos and the
Speaker 1: nature of stars and eventually hit upon a rather i
Speaker 1: would say, haunting idea. And this was in Sight three.
Speaker 1: What if a star was was massive enough, large enough
Speaker 1: that it attracted back upon itself all the light it admitted,
Speaker 1: in other words, so massive that light itself could not
Speaker 1: achieve escape velocity. This was the idea of the dark star. WHOA,
Speaker 1: Now we should give a little more context and explanation
Speaker 1: to what they're thinking was here. But I have to
Speaker 1: say the name of this paper because it's crazy. The
Speaker 1: paper by John michelle In, presented at the Royal Society
Speaker 1: of London in seven in seventeen eighty three and eighty
Speaker 1: four was quote on the means of discovering the distance, magnitude,
Speaker 1: etcetera of the fixed stars in consequence of the diminution
Speaker 1: of the velocity of their light. In case such a
Speaker 1: diminution should be found to take play sent any of them,
Speaker 1: and such other data should be procured from observations as
Speaker 1: would be farther necessary for that purpose. That's a pretty
Speaker 1: good one. It's got a ring to it. He needs
Speaker 1: like a social media editor working with him. And you
Speaker 1: get that title down. Yeah, So what's what's the clickbait
Speaker 1: title of this paper? Oh you gotta you gotta some
Speaker 1: help fit um. You know a gobbling star in there.
Speaker 1: Let's see, I tried to measure the massive binary stars.
Speaker 1: You can't You won't believe what happened next by the
Speaker 1: way that they figured that. Uh that if you have
Speaker 1: a dark star like this. This would be the case
Speaker 1: if you had a star as dense as our sun,
Speaker 1: but with a radius four nineties seven times larger, and
Speaker 1: it's such it would be difficult to optically observe such
Speaker 1: a star. Yeah, so what what was Michelle doing in
Speaker 1: this paper? As I just alluded to, his main goal,
Speaker 1: the more banal goal was to measure the mass of
Speaker 1: binary stars. So he was armed with, as you said,
Speaker 1: Newton's gravitational laws. People were excited about Newton at the time.
Speaker 1: What you could learn by using Newton so, uh, the
Speaker 1: laws guiding planetary orbits, and he had those in hand,
Speaker 1: and with those you could calculate the masses of two
Speaker 1: stars in a binary system by observing the way they
Speaker 1: orbit one another over the years. If you know how
Speaker 1: wide their orbit is and how long it takes them
Speaker 1: to orbit, you can estimate their mass. But Michell also
Speaker 1: explored the limits of light, so he was working on
Speaker 1: this assumption that light was composed of what was known
Speaker 1: at the time as corpuscles. That makes the light sound
Speaker 1: very romantic, I know, and kind of organic as well. Yeah.
Speaker 1: So the corepuscles of light collections of particles, which, given
Speaker 1: what we know about light today is sort of partially
Speaker 1: correct and partially incorrect, right like we know we know
Speaker 1: it's now given that light can be measured in particle
Speaker 1: units known as photons, but can also behave like a wave.
Speaker 1: But operating on this earlier assumption that light was composed
Speaker 1: of these corpuscles these particles, Michell noted that light, like
Speaker 1: anything else, must have an escape velocity. So the normal
Speaker 1: illustration of this is you stand on the evace of
Speaker 1: the Earth, you throw a baseball straight up in the
Speaker 1: air at a hundred kilometers an hour, it'll fall back
Speaker 1: down to the ground. And if you throw it at
Speaker 1: two hundred kilometers an hour, it will travel up farther,
Speaker 1: but it will still fall back down. If you just
Speaker 1: keep throwing it up at greater and greater velocities each time,
Speaker 1: eventually it's going to reach a velocity where, if it's
Speaker 1: at the right angle, it doesn't fall straight back down
Speaker 1: to the ground, but instead can go into orbit around
Speaker 1: the planet. And if you keep throwing it straight up
Speaker 1: at a great enough velocity, eventually it will actually escape
Speaker 1: the planet's gravity and fly off into space and not
Speaker 1: fall back down to Earth. And specifically, how fast an
Speaker 1: object needs to be traveling to leave Earth's gravity is
Speaker 1: eleven point two kilometers per second. If you can go
Speaker 1: that fast, you can leave. If not, you're stuck here
Speaker 1: with the rest of us. Uh. And a funny side
Speaker 1: here is that you ever think about the idea of
Speaker 1: a terrestrial alien planet with so much mass essentially that
Speaker 1: it prohibits the aliens who live there from practicing space
Speaker 1: exploration when also to just so so stocky they had
Speaker 1: trouble with it. Yeah, I mean, who knows how that
Speaker 1: would change their culture and all that. But uh, but yeah,
Speaker 1: I mean you could imagine a more massive planet that
Speaker 1: had a greater escape velocity might just make it the
Speaker 1: case that you could never come up with a technology
Speaker 1: that could get you out of the planet's gravity. Well,
Speaker 1: this is my entire read on the the the horror
Speaker 1: film phantasm, by the way, is that they have that
Speaker 1: portal that goes to another world. Well, how did they
Speaker 1: get here in the first place? Yeah, I guess they
Speaker 1: sent the tall man. And the tall man is tall
Speaker 1: because he's supposed to be on a high gravity planet,
Speaker 1: and it like you know, straightens them out and makes
Speaker 1: them taller on our planet. And then they have to
Speaker 1: crunch those corpses down into dwarves so that they can
Speaker 1: labor on the on the high gravity world. You know,
Speaker 1: it's it's a really smart concept. It it really gets
Speaker 1: at things that make you think, uh phantasm, Yeah, yeah,
Speaker 1: I mean, it's just mysterious enough to get your brain working,
Speaker 1: you know. Oh you know when Silicon Valley saw that ball,
Speaker 1: they were all like, I could to design one of those.
Speaker 1: I can make that ball. Yeah I Pentagon, come on, yeah,
Speaker 1: I one day, we'll see him. Now. So coming back
Speaker 1: to John Michelle, So what he believed was that you
Speaker 1: got these core pustles of light and they they've got
Speaker 1: an escape velocity as well, and what they have to
Speaker 1: do to shine away from a star is escape the
Speaker 1: stars gravity. And fortunately, as Michelle, light travels very very fast,
Speaker 1: so this doesn't normally happen. But he realized as we
Speaker 1: were saying, that if a star have has enough mass,
Speaker 1: even according to this new Tonian model of physics, before
Speaker 1: we had relativity, before we had Einstein, even on Newtonian mechanics,
Speaker 1: you could imagine a star so big with so much
Speaker 1: gravity that even light could not escape it and would
Speaker 1: always get pulled back down. And like you said Robert.
Speaker 1: The number he came up with was that a star
Speaker 1: four hundred and ninety seven times the escape velocity of
Speaker 1: our sun would prevent all light from leaving. And to
Speaker 1: read a quote from Michelle's work, the existence of bodies
Speaker 1: under these circumstances, we could have no information from sight.
Speaker 1: Yet if other luminous bodies should happen to revolve about them,
Speaker 1: we might still perhaps from the motions of those revolving bodies,
Speaker 1: infer the existence of the central ones with some degree
Speaker 1: of probability, as this might afford a clue to some
Speaker 1: of the apparent irregularities of revolving bodies, which would not
Speaker 1: be easily explicable on any other hypothesis. So Michelle's planting
Speaker 1: a clue there for how we could detect black holes
Speaker 1: or objects that did not allow light to escape before
Speaker 1: we've even discovered relativity. And I wanted to drive home
Speaker 1: again that this was the eighteenth century. Yeah, this is so,
Speaker 1: this is this is pretty out their thought from the
Speaker 1: time by by far. And I should point out that
Speaker 1: Sir William Herschel also argued on the basis of the
Speaker 1: particulate theory of light the corpuscles that nebulae could be
Speaker 1: made of agglomerations of particles of light captured by gravity,
Speaker 1: is sort of sort of held in place by gravity.
Speaker 1: So essentially that we have the groundwork here for what
Speaker 1: would eventually become the concept of a black hole, even
Speaker 1: though they certainly were not calling it a black hole. No,
Speaker 1: and uh one more thinker, we should mention somebody who
Speaker 1: often gets credited, maybe more often than Michelle, or at
Speaker 1: least used to get credited more often than John Michelle
Speaker 1: is Pierre Simon de Laplace. So, in seventeen ninety six,
Speaker 1: with the upheaval of the French Revolution still in effect,
Speaker 1: the French astronomer and general scholar kind of Renaissance Guy
Speaker 1: Pierre Simon de Laplace published Exposition du System dumont or
Speaker 1: the System of the World, And in this book he
Speaker 1: hypothesized the existence of cores, obscures, or hidden bodies or
Speaker 1: dark bodies of those dark bodies out there. So so
Speaker 1: he wrote, quote, a luminous star of the same density
Speaker 1: as the Earth, and whose diameter should be two hundred
Speaker 1: and fifty times larger than that of the Sun, would not,
Speaker 1: in consequence of its attraction and allow any of its
Speaker 1: rays to arrive at us. It is therefore possible that
Speaker 1: the largest luminous bodies in the universe may, through this cause,
Speaker 1: be invisible. Now, notice that Laplace estimated a different required
Speaker 1: size to prevent the escape of light. This is because
Speaker 1: he expected stars to have a different density than Michelle did.
Speaker 1: But either way, I love that idea. So he's saying,
Speaker 1: it's possible that the biggest things out there in the
Speaker 1: universe are completely invisible to us. We we wouldn't even
Speaker 1: know they were there. Now, rounding up from this, we
Speaker 1: know that Michelle and Laplace were certainly ahead of their time,
Speaker 1: but they were also wrong about a lot of stuff,
Speaker 1: just owing to the time that they lived. Like that,
Speaker 1: they didn't know lots of things about physics and about
Speaker 1: astronomy that we did. When they imagine stars getting so
Speaker 1: big that no light could escape their gravity, they imagine,
Speaker 1: for one thing, stars scaling up simply by getting bigger
Speaker 1: at a constant density. And then they also imagined light
Speaker 1: being a projection of particles that would be slowed down
Speaker 1: by gravity. So let's complicate the picture with some Einstein.
Speaker 1: Let's do it. We're into the twentieth century now, during
Speaker 1: the opening decades of the twentieth century German theoretical physicist
Speaker 1: Albert Einstein in is the picture. He was born eighteen
Speaker 1: seventy nine died ninety and he gave us a new
Speaker 1: theory of gravitation, the general theory of relativity, and it
Speaker 1: entails the idea that massive objects distort space time. And
Speaker 1: we experienced this as gravity. Okay, So this is a
Speaker 1: change in the idea of gravity. Instead of being a
Speaker 1: force that that objects exert on each other, general relativity
Speaker 1: imagines gravity as indentations in the geometry of the space
Speaker 1: time we inhabit. That's right. Now, there's a there's a
Speaker 1: wonderful experiment that I always like to fall back on
Speaker 1: to kind of explain this, And in fact, there's a
Speaker 1: video of this on stuff to Blow your Mind dot com,
Speaker 1: and i'll i'll try and put a link to it
Speaker 1: on the landing page for this episode. But basically it
Speaker 1: involves taking a plastic sheet, having it stretched out generally
Speaker 1: like if you stretch it over a hula hoop, okay,
Speaker 1: and then you apply weighted balls onto the sheet, so
Speaker 1: you know, you might have something that's the size of
Speaker 1: a baseball up until up up scaling up to things
Speaker 1: about the size of say a bowling ball, all right,
Speaker 1: and when you place those on the sheet, it distorts
Speaker 1: the sheet. It distorts the space time that is the
Speaker 1: surface of that sheet. Right, So normal planets and stars
Speaker 1: might be things on the sheets sort of like baseballs
Speaker 1: or golf balls or something causing these small indentations where
Speaker 1: generally things can move around them and not cause there
Speaker 1: wouldn't really be much of an issue until you got
Speaker 1: very close, and then you'd start to kind of circle
Speaker 1: around or have your path diverted as you passed by
Speaker 1: one of them, owing to the indentations they make in
Speaker 1: the topography of the sheet. But imagine you've got, say,
Speaker 1: like a big hunk of depleted uranium, and you put
Speaker 1: that on the sheet like the densest thing you can
Speaker 1: come across, and it's gonna bend the sheet down in
Speaker 1: this crazy kind of suction that will for a certain
Speaker 1: radius around it pull all kinds of stuff in. Yeah,
Speaker 1: you try and roll a marble then across the sheet,
Speaker 1: and it doesn't stand a chance it's going to be
Speaker 1: sucked in. Can't it can't say roll past and just
Speaker 1: get its path diverted. Suddenly things will just get sucked
Speaker 1: all the way in and never come out. And so this,
Speaker 1: in essence is the general theory of relativity. And again
Speaker 1: it differs from the Newtonian model in which gravity wasn't
Speaker 1: innate force, right, which Newton didn't know how to explain,
Speaker 1: and I respect he didn't try to explain. He just said,
Speaker 1: this is how it is. I'll write equations showing you
Speaker 1: how to solve for it and how to predict how
Speaker 1: it works. But I'm not going to say what it is.
Speaker 1: Now We've got a pretty idea what it actually is,
Speaker 1: and it's these these distortions in the geometry of space time.
Speaker 1: The funny thing about that is, I think how often
Speaker 1: we still talk about gravity as a force, as if
Speaker 1: it were some kind of like magnetism attracting matter. I mean,
Speaker 1: I honestly think about it that way most of the time. Yeah.
Speaker 1: I mean again, we have to fall back on on
Speaker 1: our experience, and that ends up coloring what we think
Speaker 1: we know about the cosmos. Yeah. And so Einstein definitely
Speaker 1: put he put together the theory radical framework for how
Speaker 1: general relativity works. But one thing you might wonder is, like, Okay, well,
Speaker 1: let's say we're really into Einstein's theory of general relativity.
Speaker 1: How would you ever test whether such a thing were true?
Speaker 1: You know, if you could do all of your Newtonian
Speaker 1: experiments just using Newtonian physics and get the right answers
Speaker 1: on Earth, how would you test to see whether Einstein's
Speaker 1: theory was actually better? So there did come along some demonstrations,
Speaker 1: and one of them, one that proved very decisive for
Speaker 1: public opinion, was in nineteen nineteen when the English astrophysicist
Speaker 1: Arthur Eddington carried out an experiment to test the predictions
Speaker 1: of Einstein's theory. And I think we've talked about this
Speaker 1: experiment on the show before, but one of the predictions
Speaker 1: of general relativity is that light passing directly by a
Speaker 1: massive object like a star should actually be bent by
Speaker 1: a specific predictable amount, depending on how massive the object
Speaker 1: is and how close the light passes. And so a
Speaker 1: pretty easy way to test this would be by say,
Speaker 1: taking a picture of the star field at night and
Speaker 1: noting where all of the stars are, getting the locations
Speaker 1: of those stars, and then watching what happens when the
Speaker 1: Sun passes between the Earth and those stars. It should
Speaker 1: be if Einstein's theory is right, that the light coming
Speaker 1: to us from the star behind the Sun should get
Speaker 1: bent as it's coming right past the Sun. So when
Speaker 1: it's right beside the edge of the Sun, our view
Speaker 1: of it should be displaced and distorted by a very predictable,
Speaker 1: certain small but certain amount. But part of the problem is, well,
Speaker 1: how do you test that, Like, can you usually look
Speaker 1: at the stars if you're looking also at the sun. Yes,
Speaker 1: you need something, you need something special to happen, something
Speaker 1: that that that blocks out the sign. If only there
Speaker 1: were some other object in the sky that was just
Speaker 1: the right size to do that. And for we're very
Speaker 1: fortunate to live in that laboratory by accident. So Earth's
Speaker 1: Earth is very privileged. And here's one way that the
Speaker 1: Copernican principle seems to fail. Earth is very privileged, and
Speaker 1: that our moon is just about the same size as
Speaker 1: the Sun, apparently from our perspective. So the Moon can
Speaker 1: block out the Sun's light during a solar eclipse. And
Speaker 1: if you wait for a solar eclipse, you actually could
Speaker 1: look at the stars that are shooting light at you
Speaker 1: from right beside the Sun from your perspective. So the
Speaker 1: Eddington experiment waited for a solar eclipse when the moon
Speaker 1: passed in front of the Sun, and that eclipse came
Speaker 1: in May nineteen nineteen, passing over Eddington's experimental station on
Speaker 1: prin Cape Island off the western coast of Africa, and
Speaker 1: also over some uh some other astronomers working in the
Speaker 1: Amazon rainforest. And so the eclipse dimmed the light from
Speaker 1: the Sun enough for Ddington and colleagues to take photos
Speaker 1: of the starfield in the background, and they found that
Speaker 1: the Sun did indeed bend the light from the stars
Speaker 1: right around it, and the light was bent by the
Speaker 1: amount predicted by Einstein's general relativity. So this experiment was
Speaker 1: a huge international sensation. It was in all the newspapers,
Speaker 1: and it made Einstein a celebrity. Kind of makes me wonder,
Speaker 1: like what sort of scientific experiment would make headlines in
Speaker 1: major newspapers like front page headlines in major newspapers today. Well, uh,
Speaker 1: skipping ahead a little bit here, but I believe gravitational
Speaker 1: waves uh made some some headlines. They made some I mean, like,
Speaker 1: can you imagine them as like top banner, like beating
Speaker 1: out all the politics and everything like that. Yeah, it
Speaker 1: is it is difficult to imagine it, but yeah, I
Speaker 1: want to say we still have some some hits on
Speaker 1: the way maybe maybe. So now we know that even
Speaker 1: those stars can't slow down light. One of the key
Speaker 1: features of Einstein's work is that the principle of the
Speaker 1: speed of light and a vacuum never changes. Right. We
Speaker 1: do know that very massive objects bend light as the
Speaker 1: light travels along its trajectory through spacetime very near them.
Speaker 1: And this is where we are going to introduce somebody
Speaker 1: who changed the game when it comes to black holes,
Speaker 1: and that is Carl Schwartzhield. We will discuss him when
Speaker 1: we come back from a break. Than alright, we're back,
Speaker 1: So Robert, take us into the mind of Karl schwartz Shield.
Speaker 1: All right, So Karl schwartz Field was a German physicist
Speaker 1: and astronomer. He lived only eighteen seventy three through nineteen sixteen.
Speaker 1: He died in the war. Yeah, now he and I
Speaker 1: should say they should point he did. He died of illness,
Speaker 1: but he did still very much die during the First
Speaker 1: World World War. Uh. And he calculated the possibility of
Speaker 1: an Einsteiny and dark star. Um. He like did this
Speaker 1: while he was in the in the service, I believe. Yeah. Yeah,
Speaker 1: Often it's described as him like being in the trenches.
Speaker 1: I think that, well, we like the room. The room.
Speaker 1: It's a romantic idea, right, the idea that we have
Speaker 1: someone that's in a literal pit and they're in a
Speaker 1: it's a time in in world history that is that
Speaker 1: feels like a pity and a time of just total war, uh,
Speaker 1: encompassing the Earth, and it's seeming like we not, we
Speaker 1: might not be able to climb back out of it.
Speaker 1: And here this, uh, this gentleman is contemp lighting the
Speaker 1: black hole. Yeah. As World War one is changing the
Speaker 1: social fabric of Europe and much of the world, short
Speaker 1: Shield here is changing the fabric of spacetime. Yeah. And
Speaker 1: as a he shorts shorts Field was a very impressive dude,
Speaker 1: though he was again he only lived to be forty
Speaker 1: two years of age. Uh. But during his short life
Speaker 1: he made practical and theoretical contributions to astronomy, and he
Speaker 1: used general relativity equations to demonstrate celestial bodies within enough
Speaker 1: mass would have an escape velocity beyond the speed of light.
Speaker 1: I should also point out that again, even though he
Speaker 1: died at the age of forty two, he had his
Speaker 1: first theoretical physics paper published at the age of sixteen. Yeah.
Speaker 1: He you get the impression that, like you're when you
Speaker 1: read about him, you're sort of in the presence of
Speaker 1: one of those brains. Uh so. Yeah. He he was
Speaker 1: experimenting with different types of geometry for understanding the behavior
Speaker 1: of massive objects like stars, and part of what he
Speaker 1: was doing was trying to work out rigorous solution sans
Speaker 1: to Einstein's equations. Einstein had sort of done the simplified
Speaker 1: version of general relativity, and he's like, surely it'll be
Speaker 1: really hard to work out all of the rigorous, you know,
Speaker 1: precise solutions of my equations. But but swart Shield did,
Speaker 1: and he did this by using a system of spherical coordinates.
Speaker 1: Short Shield discovered that if you imagine the mass of
Speaker 1: a star compressed down to a great density around it
Speaker 1: in all directions reaching out to a specific radius later
Speaker 1: known as the swart Shield radius, would form this gravitational
Speaker 1: dead zone. Anything that went into the dead zone, whether
Speaker 1: it was matter, light, whatever, would never come out again.
Speaker 1: And this spherical dead zone came to be known at
Speaker 1: the time as the schwart Shield sphere. Now we call
Speaker 1: the boundary leading over into this zone today the event horizon,
Speaker 1: and that's where you get the movie title. Of course,
Speaker 1: that's sort of the outer boundary of the zone of
Speaker 1: total influence of the black hole. Because inside this radius,
Speaker 1: inside the event horizon, swart Shield concluded that all radiation
Speaker 1: and matter passing into the sphere would become stuck. And
Speaker 1: of course, under general relativity, if you were flying into
Speaker 1: this sphere, outside, observers would notice your time slowing down
Speaker 1: as you approached the sphere, and to those observers out there,
Speaker 1: you would appear to sort of stop as you crossed over.
Speaker 1: So do the people imagining this object, like, what would
Speaker 1: they picture? Maybe according to this conception, anything entering the
Speaker 1: sphere of the short Shield radius would seem to appear
Speaker 1: frozen forever in time at the moment it was about
Speaker 1: to cross over into the dead zone. Speaking, this made
Speaker 1: me think about one of the videos we watched from
Speaker 1: the World You were there at the event, but one
Speaker 1: that I watched from the World Science Festival this year
Speaker 1: had a astrophysicist Chep Doleman talking about black holes and
Speaker 1: he said, quote, what happens in the black hole stays
Speaker 1: in the black hole. Yeah. I like that. That that
Speaker 1: that oftentimes you see the especially the more modern physicists
Speaker 1: who who have written about black holes that they tend
Speaker 1: to have a sense of humor regarding their nature. Yeah, yeah,
Speaker 1: I think that's generally true, like they don't get all well.
Speaker 1: I mean, so here's what you can contrast that lighthearted
Speaker 1: approach with. Apparently some French speaking astrophysicists took to calling
Speaker 1: the short shield sphere the sphere catastrophe, the sphere that's
Speaker 1: a hard thing to say, sphere catastrophe. I like the
Speaker 1: idea of this, of this is being the avant garde
Speaker 1: French version of the event Arizon. Oh I'd pay to
Speaker 1: see that. I hope it's still have sam Neil. Now
Speaker 1: we go with the instead. Oh yeah, okay, it would be.
Speaker 1: It would be a great version of event Horizon where
Speaker 1: every scene they have fresh baked bread. Now, one thing
Speaker 1: that's worth noting about the sphere of doom, the schwart
Speaker 1: shield sphere or the sphere catastrophe, it's not actually the
Speaker 1: same as the central object, the black hole itself. An
Speaker 1: example given in Marcia Bartosik's black Hole, our son is
Speaker 1: about one point four million kilometers wide. If a star
Speaker 1: the mass of our Sun were compressed down to a point,
Speaker 1: the sphere catastropheke surrounding it would be less than six
Speaker 1: kilometers across. If the mass of ten sons were reduced
Speaker 1: to a point like volume, its sphere catastrophe would be
Speaker 1: about sixty kilometers wide. And as we mentioned earlier, if
Speaker 1: our son were to suddenly shrink down to that size,
Speaker 1: objects far outside the sphere would not suddenly be like
Speaker 1: sucked in or torn apart. The planets would continue orbiting
Speaker 1: just like they orbit the Sun, only it's only much
Speaker 1: closer that things would really go crazy. But here's a
Speaker 1: really important point that we need to drive home. At
Speaker 1: this stage, even after short Shield had done these these calculations,
Speaker 1: most physicists and astronomers did not believe a black hole
Speaker 1: could exist in nature. Uh. Einstein just thought that short
Speaker 1: Shield sphere sphere of doom thing was a sign there
Speaker 1: was still some things to work out in the theory,
Speaker 1: and Einstein did not think that black holes would be
Speaker 1: found in the actual universe. So at the time, the
Speaker 1: idea that it might have just been a mirror ghost
Speaker 1: in the math kind of a remainder that had to
Speaker 1: be figured out later on. Yeah, so you do the
Speaker 1: math and you say, oh, this is a strange finding.
Speaker 1: But people, I think, just assumed, Well, so we'll find
Speaker 1: out something in the future that will make sense of
Speaker 1: all this, you know, we will have some kind of observation,
Speaker 1: some update to the theory, something that will eventually let
Speaker 1: us know, oh, okay, there's not actually such a thing
Speaker 1: as a black hole. They weren't calling it a black
Speaker 1: hole at the time, but there's not actually one of
Speaker 1: these to be found in nature. Something prevents this from happening.
Speaker 1: So remember Arthur Eddington, the English astro physicist who did
Speaker 1: the eclipse experiment about general relativity. In his nineteen book
Speaker 1: The Internal Constitution of the Stars, he wrote, I think,
Speaker 1: kind of dryly, invoking some awesome imagery, I might add quote,
Speaker 1: a star of two d and fifty million kilometers radius
Speaker 1: could not possibly have so high a density as the Sun. Firstly,
Speaker 1: the force of gravitation would so great that light would
Speaker 1: be unable to escape it, the rays falling back to
Speaker 1: the star like a stone to the Earth. Secondly, the
Speaker 1: red shift of the spectral lines would be so great
Speaker 1: that the spectrum would be shifted out of existence. Thirdly,
Speaker 1: the mass would produce so much curvature of the space
Speaker 1: time metric that space would close up around the star,
Speaker 1: leaving us outside i e. Nowhere. So the idea is
Speaker 1: that it would can suddenly contain all of space, and
Speaker 1: then we couldn't be in space anymore. Well, when you
Speaker 1: put it like that, it does sound like a like
Speaker 1: a mathematical problem that has to be worked out later on.
Speaker 1: But of course Eddington was wrong about that, and even
Speaker 1: Schwartzfield himself didn't think you would find these mathematical objects
Speaker 1: in nature. He thought that sort of the outward pressure
Speaker 1: of stars would prevent them from collapsing down to a
Speaker 1: volume smaller than that sphere catastrophe. And remember he was
Speaker 1: not setting out to posit the existence of black holes.
Speaker 1: That wasn't his goal. That they just simply pop up
Speaker 1: as this weird byproduct of him using general relativity to
Speaker 1: calculate the gravitational fields generated by different kinds of massive
Speaker 1: bodies in space. Now we have to stress here that
Speaker 1: sword Shield didn't call it a black hole. He called
Speaker 1: it a discontinuity. Yeah, what did Eddington call it? Oh?
Speaker 1: He called it a magic circle. Oh that's really good.
Speaker 1: I kind of wish we'd stuck with that. Yeah, though
Speaker 1: that of course has its own baggage. You expect like
Speaker 1: elves to come flying out of it, right. Uh No,
Speaker 1: But the term black hole was coined later still by
Speaker 1: American theoretical physicist John Archibald Wheeler, who lived nineteen eleven
Speaker 1: through two thousand and eight. Did he coin it or
Speaker 1: was he just the first one to start using it? Well?
Speaker 1: He has. So the story that I read is that
Speaker 1: he was in a conference in New York City in
Speaker 1: nineteen sixty seven and he apparently seized on a suggestion
Speaker 1: shouted from the audience. I'm a I'm as I could.
Speaker 1: I couldn't find out what the exact shout was, but
Speaker 1: I'm assuming it was something like call it a black hole, John,
Speaker 1: or that's a black hole, something of that effect, or
Speaker 1: just maybe a chant black hole black hole. So he
Speaker 1: was like trying to work the audience. He's like, throw
Speaker 1: out some names, come on, give me some ideas, and
Speaker 1: people are like magic circle and he's like, nah, no,
Speaker 1: no magic circles here. Yeah, it's like improv alright, somebody
Speaker 1: give me a theme and we'll we'll construct some sort
Speaker 1: of theoretical physics structure out of it. How about dark Star?
Speaker 1: So in his autobiography Sphere Catastrophe, I would like to
Speaker 1: see an improv sketch around the sphere catastrophe. Uh So.
Speaker 1: In his autobiography, Wheeler wrote that the black hole quote
Speaker 1: teaches us that space can be crumpled like a piece
Speaker 1: of paper into an infanticible dot, that time can be
Speaker 1: extinguished like a blown out flame, and that the laws
Speaker 1: of physics that we regard as sacred, as immutable or anything,
Speaker 1: but which I think sums it up rather nicely. Yeah,
Speaker 1: I like that. Well, I mean it also Wheeler, there
Speaker 1: he speaking, Einstein is ms right, Like the whole idea
Speaker 1: of general relativity is that we used to think, oh,
Speaker 1: space and time, those are the things that are constant
Speaker 1: and immutable, and other stuff can can get moved around,
Speaker 1: and we found out through relativity. No, well, the speed
Speaker 1: of light and a vacuum might be constant, but space
Speaker 1: and time you mess all. You mess with them a
Speaker 1: lot and Wheeler Wheeler is carrying that torch. So maybe
Speaker 1: that's going to be where we have to wrap up today.
Speaker 1: But the big question left lingering for us to explore
Speaker 1: next time is how did this mathematical curiosity this sort
Speaker 1: of like weird artifact of people trying to solve problems
Speaker 1: on paper become a feature that scientists actually think exists
Speaker 1: out in the physical world, and how do we detect
Speaker 1: them if they do exist? You will find out next time.
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