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Speaker 1: My World. Welcome to Stuff to Blow your Mind from

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Speaker 1: how Stuff Works dot com. Hey, welcome to Stuff to

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Speaker 1: Blow your Mind. My name is Robert Lamb and I'm

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Speaker 1: Joe McCormick, and today is going to be part one

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Speaker 1: of a multi part episode on on a topic that

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Speaker 1: I know you came back from New York with a fever.

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Speaker 1: For Robert, We're gonna be talking about black holes, that's right. Yeah,

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Speaker 1: I attended, Uh, I attended a talk at the World

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Speaker 1: Science Festival that I believe I mentioned in our previous

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Speaker 1: sort of World Science Festival roundup episode that I just

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Speaker 1: thought did a great job of providing an overview of

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Speaker 1: black holes and uh help straighten out a few of

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Speaker 1: the details for me. Yeah, I realized we have talked

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Speaker 1: about black holes on the podcast before, but you haven't

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Speaker 1: really I felt given it, given them proper, do We haven't.

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Speaker 1: We haven't really uh looked at black holes with the

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Speaker 1: attention that they deserve. Yeah, And of course, even in

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Speaker 1: doing a multi part series, we're not gonna be able

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Speaker 1: to cover every interesting thing about black holes. So this

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Speaker 1: is gonna be kind of a grab bag of things

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Speaker 1: that seemed interesting to us. So in this first episode,

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Speaker 1: we're gonna be talking mainly about the history of the idea,

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Speaker 1: where it came from, how we arrived at this bizarre

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Speaker 1: conclusion about the cosmos that we live in. In the

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Speaker 1: second episode, we're going to be focusing mainly on like

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Speaker 1: how we get a look at these things. And in

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Speaker 1: the third episode, I think we're gonna explore some of

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Speaker 1: the strangest avenues of thought that you can contemplate with

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Speaker 1: regard to black holes, like what's it like to fall

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Speaker 1: into one? Or what happens when a black hole collapses?

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Speaker 1: Does it does it create something on the inside? Yeah,

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Speaker 1: And I want to acknowledge that black holes, I feel

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Speaker 1: are kind of a challenging topic to tackle some people.

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Speaker 1: I mean, certainly from a like a physics standpoint, yes,

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Speaker 1: but but also just in terms of becoming engaged with

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Speaker 1: the idea, because I know there are plenty of you

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Speaker 1: out there like, yeah, black holes, let's do this. I

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Speaker 1: love I love science I love science fiction. I think

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Speaker 1: King of of all my favorite black hole related movies.

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Speaker 1: But I know other people are a little hesitant because ultimately,

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Speaker 1: black holes are a concept that have very little impact

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Speaker 1: on our personal lives and the scope of the universe.

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Speaker 1: That we observe and interact in. Well, they don't have

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Speaker 1: any people in them, right. I mean a lot of times,

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Speaker 1: I think when people look up to space and they say,

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Speaker 1: you know, I want to be interested in it, but

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Speaker 1: there's if there's no people up there, it's hard to

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Speaker 1: feel like I'm following a story or narrative. Or can

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Speaker 1: I even imagine a person there, because obviously there are

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Speaker 1: no people on Mars. But I can, But I can

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Speaker 1: imagine a future in which there are people on Mars.

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Speaker 1: I can. I can imagine multiple different sci fi scenarios,

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Speaker 1: many of which match up reasonably well with scientific expectations,

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Speaker 1: and and that can allow me to engage myself in

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Speaker 1: Mars more. But unfortunately, if you know anything about black holes,

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Speaker 1: you know that it's not even possible to say colonies

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Speaker 1: a black hole. You can't have singular and knots going

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Speaker 1: in there to see what's on the inside. Or you could,

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Speaker 1: but it just wouldn't be very useful for us on

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Speaker 1: the outside, or I guess very useful for those getting

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Speaker 1: ripped apart on the inside. Right. And I think another

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Speaker 1: challenge with black holes is that when they have played

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Speaker 1: a key role in science fiction and been made ultimately

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Speaker 1: kind of relatable concepts. Uh, the films don't really do

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Speaker 1: much with the science. They don't really do a great

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Speaker 1: job about really conveying what a black hole is. For instance,

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Speaker 1: I have to admit that my first introduction to black

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Speaker 1: holes was the nineteen seventy nine Walt Disney sci fi

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Speaker 1: movie The black Hole. Oh, Robert, I've never seen this one,

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Speaker 1: but I'm excited. I'm excited for you to tell me

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Speaker 1: about it. Tell me about it, fill my brain. All right,

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Speaker 1: we'll just briefly. I'll try not to go on too

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Speaker 1: long about this, because this is a film I loved

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Speaker 1: as a child and I still look back on finally today.

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Speaker 1: But it lands in a weird spot for a science

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Speaker 1: fiction film because it's it's not as fun and original

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Speaker 1: as nineteen seventy seven Star Wars, and of course it's

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Speaker 1: nowhere near as high minded and scientifically savvy as ninety

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Speaker 1: eight two thousand and one of Space Odyssey. But then again,

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Speaker 1: you know what is Instead, it's kind of an old

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Speaker 1: fashioned Jules Verne esque tale of space explorers who wind

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Speaker 1: up on a space station that's circling a black hole,

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Speaker 1: and the station's run by a mad scientist whose only

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Speaker 1: attendance are robots and lowbottomized androids. There's ultimately some fairly

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Speaker 1: horrific and and kind of ambitious stuff mixed in there,

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Speaker 1: but you're also faced with just kind of a maximum

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Speaker 1: dosage of of of of late seventies big budget cinema.

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Speaker 1: Like all the actors you would expect to show up

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Speaker 1: do show up. Ernest borg nine, Anthony Perkins, great, Maximilian

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Speaker 1: Shell shows up as the villain. How about Harry Dean Stanton?

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Speaker 1: Uh no, no, Dean Stanton, as I recall, And you

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Speaker 1: also have one of the Bottoms brothers, timoth Bottoms, No, no,

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Speaker 1: no one one of the other ones. Not not last

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Speaker 1: picture was it last picture show? Yeah, less picture show, Yeah,

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Speaker 1: not last picture shows bottoms, but but but one of

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Speaker 1: the other ones some other bottoms yes, okay. And also

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Speaker 1: slim pickings, slim pickings. Yeah, he's the voice of a

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Speaker 1: robhid just busted up robot it had It is really

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Speaker 1: cool robots in it. I gotta see this. The trailer

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Speaker 1: is pretty great for it. H In fact, if we

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Speaker 1: if we can play it, I would like to just

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Speaker 1: throw in just a clip from this trailer. There is

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Speaker 1: an inexorable force in the cosmos, where time and space converge,

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Speaker 1: a place beyond men's vision but not to his reach.

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Speaker 1: It is the most misdious and awesome point in the universe,

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Speaker 1: whether here and now maybe forever. The black hole in

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Speaker 1: this film, the actual black hole that we're presented with,

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Speaker 1: it's it's it's presented like a vortex. It's it's more

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Speaker 1: in keeping with the charybdis whirlpool of Greek myth. You know, this,

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Speaker 1: this terrible thing that you're on the verge of falling into.

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Speaker 1: It's ultimately treated with more religious reverence than scientific, which

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Speaker 1: of course is pretty much what happens later on in

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Speaker 1: the film Event Horizon, which I also love, but it's

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Speaker 1: hardly a scientific tour to force. Were you watching Event

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Speaker 1: Horizon recently, Robert, Yes, I was. I started watching it

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Speaker 1: again last night, but only made it about ten minutes

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Speaker 1: in before my ambient kicked in, because that's a horrible idea.

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Speaker 1: It's it's not really not ten minutes end, because you

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Speaker 1: get past the scary stuff and then you're just done

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Speaker 1: a spaceship, and then you realize it's time to go

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Speaker 1: to bed. I realized that the spaceship in that movie

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Speaker 1: it's like the only leather punk spaceship I've ever seen

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Speaker 1: in science fiction. It's like, you know, those like black

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Speaker 1: leather wrist bands with the metal studs on them. It's

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Speaker 1: that as a spaceship, it is very industrious, especially the uh,

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Speaker 1: the core that you end up exploring. But but hopefully

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Speaker 1: we'll get to talk about event Arizon a little bit

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Speaker 1: more in one of the future episodes. But basically the

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Speaker 1: idea is it's got a black hole and that's how

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Speaker 1: you get to Hell. I think, yeah, which again is

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Speaker 1: kind of the idea that has explored in Disney's a

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Speaker 1: black Hole as well. So there's people in it, well,

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Speaker 1: there are things in it, humanoids that you end up

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Speaker 1: with characters traveling through it. It's ultimately the confusing part

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Speaker 1: is that both films kind of treat a black hole

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Speaker 1: more like a wormhole, which is a separate thing altogether,

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Speaker 1: but that is ultimately more relatable I think to us

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Speaker 1: the idea of like a magic tunnel that goes somewhere.

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Speaker 1: But of course, actual black holes don't exist on a

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Speaker 1: scale that that directly influences individual human life for life

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Speaker 1: on Earth, except in our study of them. But the

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Speaker 1: bottom line is that they're They're just a physical reality

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Speaker 1: of our universe. They're not some sort of evil, malignant force.

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Speaker 1: They are just a physical part of the universe. At

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Speaker 1: the same time, though, I would say they are astounding

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Speaker 1: and one of the most interesting things in the universe

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Speaker 1: because they are the absolute extremists of of what we

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Speaker 1: know about physics. They're sort of like the test cases.

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Speaker 1: They're the exceptions. They break things that and that. For

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Speaker 1: that reason, they're interesting to scientists because we can look

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Speaker 1: at them and say, okay, what happens in these extreme

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Speaker 1: cases where you know, where we can't necessarily see inside

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Speaker 1: to know the answer. So at this point some of

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Speaker 1: you might be asking, well, well, what is a black hole?

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Speaker 1: Just lay lay out the basic definition. If it's not

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Speaker 1: a wormhole, it's not a gateway to Hell, then then

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Speaker 1: what are we talking about here? Well, in short, we're

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Speaker 1: talking about regions of space where the gravity is so

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Speaker 1: intense that light cannot escape the poll and the gravity

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Speaker 1: is that intense because matter is compressed to a very

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Speaker 1: small space and they range in size. For instance, primordial

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Speaker 1: black holes are no larger than a single atom, but

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Speaker 1: they contain the mass of a terrestrial Mount him So

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Speaker 1: Mount everest crunched down to the side of an atom.

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Speaker 1: It's pretty dense. A stellar black hole might be ten

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Speaker 1: kilometers in diameter, but would boast the mass of twenty suns,

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Speaker 1: for instance. And then finally you have the supermassive black hole. Uh,

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Speaker 1: the types of black holes that that that that live

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Speaker 1: at the centers of galaxies. Uh. And these would have

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Speaker 1: the mass of millions of suns compressed to a sphere

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Speaker 1: the size of a single solar system. That's extreme compression. Yeah,

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Speaker 1: a little harder to even think about it. Like I

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Speaker 1: find that the mountain atom uh comparison is maybe a

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Speaker 1: little more impactful for the human imagination. But still we're

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Speaker 1: talking about considerable, considerable consolidation of mass. Now we call

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Speaker 1: them black holes because light cannot escape them. Optically, they

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Speaker 1: appear as an absence. We can't see inside them, but

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Speaker 1: we can observe the effect of say, of of this

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Speaker 1: intense gravity on the surrounding environment. And despite the fact

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Speaker 1: that we can't see inside them, as we'll talk about

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Speaker 1: a couple of times as we go along, that doesn't

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Speaker 1: necessarily mean we don't see anything around them. In fact,

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Speaker 1: they can often put on quite a show. Yeah, I

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Speaker 1: hate to lean into the horror movie implications here, but

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Speaker 1: it's kind of like imagine the uh, the house from

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Speaker 1: the Texas Chainsaw Mask. Here, you can't see any of

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Speaker 1: the teenagers dying inside it from the outside, but you

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Speaker 1: see them like moving towards the house. You see a

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Speaker 1: lot of of random hippie activity on the outside, and

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Speaker 1: it gives you an idea of what might be going

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Speaker 1: on in the inside. Actually came up with an analogy

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Speaker 1: I was going to use in the next episode, but

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Speaker 1: maybe I'll go ahead and say it. So this is

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Speaker 1: a little less grizzly than what you said, but kind

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Speaker 1: of similar. So, uh, imagine you've got like a haunted

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Speaker 1: house ride in an amusement park, and the ride, the

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Speaker 1: part of the ride that you ride in is the

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Speaker 1: soundproof box where nobody can hear anything on the outside.

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Speaker 1: So you've got everybody in line to get in the ride,

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Speaker 1: to get in the soundproof box and go through the

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Speaker 1: haunted house. And as you're hurting tourists towards this soundproof box,

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Speaker 1: even though you can't hear any of the screams inside

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Speaker 1: the box, you will hear more and more sort of

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Speaker 1: nervous chatter and laughter and shrieks as people are approaching

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Speaker 1: the door, but then once you shut the door, bye bye.

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Speaker 1: I like that we both independently came up with haunted

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Speaker 1: house explanations for black holes. Personally, I seriously doubt that

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Speaker 1: the Texas Chainsaw House is haunted or contains a black hole. Now,

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Speaker 1: now it's important to note in all of this that

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Speaker 1: I really think we should try and get away from

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Speaker 1: thinking of black holes as essentially galactus or or some

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Speaker 1: sort of other unstoppable, insatiable cosmic devour that just destroys

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Speaker 1: and consumes everything, which is kind of hard because, as

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Speaker 1: we've discussed before in the show, like that's a classic

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Speaker 1: mythic trope, like the idea of some entity that will

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Speaker 1: consume the Sun. I mean, it's key to these various

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Speaker 1: eclipse mythologies that we've discussed in the past. But a

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Speaker 1: black hole is not, uh, this thing is just going

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Speaker 1: to eat the entire universe. They're bound by physics, so stars, planets,

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Speaker 1: whole galaxies may orbit around them. And I've seen it

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Speaker 1: pointed out before by NASA that if our Sun were

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Speaker 1: a black hole of equal mass, the Earth would not

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Speaker 1: fall in. Yeah, that's a point I've read many times before.

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Speaker 1: So what would happen to the Earth if the Sun

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Speaker 1: turned into a black hole? The Earth would keep orbiting. Yeah,

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Speaker 1: So again, to come back to the Texas Chainsaw mascure House,

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Speaker 1: it's it's not like the Texas Chainsaw Masscure House is

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Speaker 1: just going to suck in everybody in the surrounding area

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Speaker 1: and collapse the town. Now, the town continues to thrive. Yeah,

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Speaker 1: the next door neighbors, they just keep going to work,

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Speaker 1: they saying, keep selling barbecue. Everything's fine. And I also

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Speaker 1: think again, the whole aspect of this is a stumbling

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Speaker 1: block because it tends to encourage us to think of

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Speaker 1: black holes less as what they presumably are and more

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Speaker 1: like wormholes. Okay, so it's like it's like a tunnel

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Speaker 1: you can go through. Yeah, yeah, But ultimately, a singularity

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Speaker 1: is not a gateway. It doesn't go anywhere other than

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Speaker 1: to the center of its gravity. Their celestial objects that

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Speaker 1: just happened to be massive on a scale that's really

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Speaker 1: harder to square with human experience. Well, I can tell already,

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Speaker 1: Robert that you're running into issues with the language that

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Speaker 1: we have to use to describe things, because there is

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Speaker 1: no language, I mean, the only language we have is

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Speaker 1: like normal terrestrial vocabulary, and then the metaphors we build

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Speaker 1: out of that normal terrestrial vocabulary, so inevitably our language

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Speaker 1: will ultimately fail to have words that, at a fundamental

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Speaker 1: level really communicate the nature of celestial objects, you know,

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Speaker 1: powerful objects, huge objects like black holes. So we we

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Speaker 1: just have to use metaphors, right, and the idea of

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Speaker 1: a black hole is a metaphor. Yeah, and it's it's

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Speaker 1: a challenge for science communication for sure. A lot of

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Speaker 1: great black hole studies come out, and then you look

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Speaker 1: at the headlines that that are used right to to

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Speaker 1: relate these findings, and it's it's I often get a

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Speaker 1: laugh out of it because the world leader model is

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Speaker 1: so often employed and you end up hearing reading about

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Speaker 1: hannibal black holes, gobbling black holes, eating black holes, barfing

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Speaker 1: black holes. Yeah, it's so anthropomorphised in a really visceral way.

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Speaker 1: I mean you almost want to imagine that there are

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Speaker 1: articles about dating black holes, swipe right black holes. But

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Speaker 1: it's it's kind of a your damned if you do,

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Speaker 1: your damned if you don't situation. It's kind of like

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Speaker 1: when you when when we even anthropomorphize evolution to some extent,

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Speaker 1: we treat it like a person, right, And I mean,

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Speaker 1: on one hand, I acknowledge, yes, one should not do that.

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Speaker 1: You fall into, you know, potential traps by doing it.

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Speaker 1: But at the same time, you ultimately are trying to

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Speaker 1: put some fairly complex ideas into a form that people

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Speaker 1: can really consume. Well, you can talk about evolution without

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Speaker 1: anthropomorphizing it or you know, treating it like a person

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Speaker 1: with intentions. It's possible to do that. It can just

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Speaker 1: get really tedious to constantly be talking that way. So

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Speaker 1: we and we inevitably in these discussions, if we're just

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Speaker 1: trying to move things long and you know, move at

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Speaker 1: a brisk pace, we end up using the shorthand. And

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Speaker 1: the same thing happens for black holes. Black holes, we

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Speaker 1: end up using these colloquial shorthands to describe them that

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Speaker 1: are based on Earth metaphors that don't really get at

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Speaker 1: the truth of what it's like to have the geometry

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Speaker 1: of space time warped by this gravitational anomaly. Now, one

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Speaker 1: of the really fascinating things about black holes, though, is

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Speaker 1: that we we simply we didn't simply look into the

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Speaker 1: sky and observe them. Uh. It all began with the math.

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Speaker 1: It began with with with some some very bright individuals

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Speaker 1: crunching the numbers and seeing them as a possibility. Yeah,

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Speaker 1: and that's one of the things that makes black holes

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Speaker 1: so interesting. They weren't like stars. They weren't you know, stars.

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Speaker 1: We could look up and know something was there, and

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Speaker 1: then over time gradually make observations to refine our knowledge

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Speaker 1: of what stars are. Right, black holes weren't like that.

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Speaker 1: We had to work them out from first principles and

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Speaker 1: then say, okay, is there a way we could observe them?

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Speaker 1: It worked actually the opposite way. Yeah, that's the beautiful

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Speaker 1: part we see because we see it paying off. We

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Speaker 1: we we we we end up looking out into the

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Speaker 1: cosmos and observing the very things that we have simulated

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Speaker 1: with math and physics. The great astrophysicists Supermania and Chandra

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Speaker 1: Sheker had in a prologue to his book The Mathematical

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Speaker 1: Theory of black Holes, he wrote, quote, the black holes

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Speaker 1: of nature are the most perfect macroscopic objects there are

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Speaker 1: in the universe. The only elements in their construction are

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Speaker 1: our concepts of space and time. All right, Well, on

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Speaker 1: that note, we're gonna take a quick break, and when

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Speaker 1: we come back. We are going to jump into the

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Speaker 1: history of black holes. Thank you, thank alright, we're back.

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Speaker 1: So previously we were just talking about how black holes

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Speaker 1: began as an idea before they were observed in nature.

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Speaker 1: They started as something that people worked out from principles

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Speaker 1: they had established through other means, rather than something we

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Speaker 1: looked up into the heavens and saw. And there's there's

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Speaker 1: a really great book about this actually that I want

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Speaker 1: to for two because it's one of the sources I

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Speaker 1: used in working on this episode. But it's called black

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Speaker 1: Hole by Marcia Bartoustiac, and it's a it's a book

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Speaker 1: just about the history of the idea of the black hole,

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Speaker 1: how it went from the idea of gravity to something

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Speaker 1: that we now do experiments on with with cosmological detection equipment.

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Speaker 1: So the story of the black hole can really be connected,

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Speaker 1: I think, to the broader story of the discovery of gravity. Uh.

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Speaker 1: You know, we often don't even bother to think anymore,

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Speaker 1: why do objects fall down and not up? But I, oh,

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Speaker 1: I sometimes wonder like do kids still have this thought?

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Speaker 1: Do kids ask this sometimes or are they exposed to

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Speaker 1: the theories we have of gravity before they even have

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Speaker 1: the chance to ask that question naturally, you know, that's

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Speaker 1: that's a great question, because I they certainly grasp the

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Speaker 1: idea and the reality of gravity is just one of

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Speaker 1: the realities of the natural world that they've evolved to

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Speaker 1: thrive him. Of course we understand how it works, but

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Speaker 1: why yeah, yeah, you know my own personal experience, I

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Speaker 1: don't know that I've ever had a conversation with my

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Speaker 1: son about gravity um or at least not when he

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Speaker 1: was old enough to to appreciate it. I'm gonna have

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Speaker 1: to make a mission of explaining it to him. But

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Speaker 1: he also he may know already because he listens to

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Speaker 1: to educational podcasts, so he when I mentioned black holes,

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Speaker 1: he was like, oh, yeah, black holes. I was listening

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Speaker 1: to a while in the world about black holes, so

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Speaker 1: he already had a already had a leg up on

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Speaker 1: the concept. Well, I mean, it's one of those things

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Speaker 1: where most of us, I think, even people who are

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Speaker 1: aware of general relativity, we sort of have the idea

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Speaker 1: that we understand how gravity works, but then sit down

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Speaker 1: and try to put into words like explain it, and

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Speaker 1: then you start going, oh, wait a minute. But yeah,

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Speaker 1: So it's one of those things that once you've heard

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Speaker 1: it you think you've got to grasp on it, but

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Speaker 1: even then it can prove tricky to try to explain yourself.

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Speaker 1: But so you know, thousands or maybe millions of people

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Speaker 1: must have stopped to wonder this all the time before

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Speaker 1: we had a real answer why did things fall down

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Speaker 1: instead of up? And for a long time I think

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Speaker 1: humans were led astray by this intuitive, false cosmology of geocentrism.

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Speaker 1: So if you believe, like Aristotle, that the Earth is

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Speaker 1: the center of the universe, it makes a kind of

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Speaker 1: intuitive sense that everything would fall toward the center, right

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Speaker 1: And then again I sometimes wonder, like, why is that

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Speaker 1: even intuitive? Why doesn't everything fall away from the center

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Speaker 1: out to the edges. It just feels right enough that

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Speaker 1: you can stop thinking about the question basically. But then

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Speaker 1: once you introduce the Copernican model, the you know, the

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Speaker 1: heliocentric model of the Solar system, and the idea that

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Speaker 1: the Earth is not the center of the universe and

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Speaker 1: in fact is no kind of privileged place at all.

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Speaker 1: It's just another object floating around in space, Suddenly we

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Speaker 1: really need an explanation for why objects fall to the

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Speaker 1: ground rather than fly off in the opposite direction. And

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Speaker 1: the bigger question. Is the force that causes objects to

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Speaker 1: fall to the ground the same force that guides planets

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Speaker 1: in their orbits around the Sun. I like what you

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Speaker 1: said about the geocentric view because I think the geocentric

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Speaker 1: view also kind of lines up with our aasic egoic

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Speaker 1: experience of the world, Like everything in the world ultimately

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Speaker 1: breaks down to what I feel about it, because I

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Speaker 1: am the only the only experience, the only worldview you

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Speaker 1: know that I that I have control of and one

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Speaker 1: percent vision through. And uh. But then if someone would say, actually,

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Speaker 1: you're not the most important person in the world. Is

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Speaker 1: uh this person over here is that throws everything out

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Speaker 1: of out of whack. Well, it makes you realize that

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Speaker 1: your egoic view is not even necessarily a coherent view,

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Speaker 1: is just something that you can do without having to

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Speaker 1: think about. And I would argue the same is largely

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Speaker 1: true for geocentric physics. Uh though actually, in a funny way,

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Speaker 1: a lot of really intense thinking did go into constructing

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Speaker 1: geocentric cosmologies and they look kind of beautiful. But anyway,

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Speaker 1: coming back to gravity, so so we know that for example,

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Speaker 1: Johannes Kepler suggested that the sun exerted a magnetic force

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Speaker 1: that guided the orbits of the planets. Weird to think

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Speaker 1: back to a time when they were thinking, Okay, how

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Speaker 1: are the planets controlled in there? Or maybe it's magnetism.

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Speaker 1: We know magnets exist, that's an attractive force. Maybe that's

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Speaker 1: what controls it. And in the sixteen thirties, Descartes proposed

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Speaker 1: that the orbits of the planets were guided by swirlings

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Speaker 1: in the ether, which was this substance that was believed

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Speaker 1: to occupy space. The ether would have been kind of

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Speaker 1: like air water, this fluid that occupied empty space, and

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Speaker 1: you could have whirlpools or cyclones guiding objects in a

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Speaker 1: circular pattern around a center of motion, and that would

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Speaker 1: be what would guide orbits in the ether. But then,

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Speaker 1: of course we got to Newton. And so in sixteen

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Speaker 1: seven Isaac Newton struck gold with the philosophy naturalists Principia Mathematica,

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Speaker 1: or the Principia as people usually call it these days,

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Speaker 1: and it established the mathematical principles that correctly describe gravity

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Speaker 1: and planetary motion, which in effect turn out to be

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Speaker 1: the same thing. The motion of the planets dis guided

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Speaker 1: by momentum and gravity, and Newton calculated the inverse square

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Speaker 1: law of gravity, meaning that as you move away from

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Speaker 1: an object, it's gravitational influence is diminished by the square

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Speaker 1: of the distance. So what does that mean. That means

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Speaker 1: if you double the distance between two objects, the gravitational

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Speaker 1: force between them is reduced to a fourth and if

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Speaker 1: you quadruple the distance, the gravitational force between them is

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Speaker 1: decreased to one sixteen. It's a square of the distance.

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Speaker 1: So this indicates that the force of gravity is a

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Speaker 1: constant force, spreading out equally in all three dimensions. And

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Speaker 1: so a key insight that that Newton has that gravity

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Speaker 1: is universal. It applies equally to the objects we drop

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Speaker 1: and throw here on Earth, end of the objects we

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Speaker 1: see in the night sky. Though it's worth pointing out

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Speaker 1: at this stage that we still didn't know what gravity

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Speaker 1: actually was other than this mutually attractive force between objects

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Speaker 1: with mass. Newton wrote, actually, quote, I have not as

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Speaker 1: yet been able to deduce from phenomena the reason for

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Speaker 1: these properties of gravity, and I do not feign hypotheses.

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Speaker 1: And so Newton's laws were widely accepted, especially after they

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Speaker 1: were used to correctly predict the reappearing of Halley's comment

428
00:23:01,359 --> 00:23:07,880
Speaker 1: and this leads us to an English natural philosopher, geologist, astronomer, mathematician,

429
00:23:08,040 --> 00:23:13,160
Speaker 1: dabbler in mini domains named John Michelle. That's right, armed

430
00:23:13,240 --> 00:23:16,720
Speaker 1: only with a Newtonian and obviously pre Einsteiny and understanding

431
00:23:16,720 --> 00:23:21,960
Speaker 1: of gravity. Um. John Michelle and Henry Cavendish, Uh, contemplated

432
00:23:22,000 --> 00:23:25,359
Speaker 1: some pretty big cosmological questions, including the scale of the

433
00:23:25,480 --> 00:23:28,160
Speaker 1: universe and the cycle of stars. Yeah, they were really

434
00:23:28,200 --> 00:23:30,280
Speaker 1: ahead of their time in a way. John Michelle for

435
00:23:30,320 --> 00:23:33,720
Speaker 1: a long time was not necessarily recognized as one of

436
00:23:33,760 --> 00:23:36,480
Speaker 1: the earliest people to think about black holes. But but

437
00:23:36,560 --> 00:23:38,840
Speaker 1: he did some interesting work. Yeah. And and to put

438
00:23:38,880 --> 00:23:41,080
Speaker 1: him in within a you know, you have the right

439
00:23:41,160 --> 00:23:47,159
Speaker 1: time scale here. Uh. John Mitchell literally of seventeen and

440
00:23:47,240 --> 00:23:50,800
Speaker 1: Cavendish lived seventeen through eighteen ten. Okay, so what was

441
00:23:50,880 --> 00:23:53,680
Speaker 1: the deal? What? How did they touch on black holes? All? Right? So,

442
00:23:54,240 --> 00:23:57,080
Speaker 1: even in their day, it was known that stars flared up,

443
00:23:57,280 --> 00:24:01,240
Speaker 1: they subsided, and even vanished from the heavens. A popular

444
00:24:01,320 --> 00:24:04,400
Speaker 1: theory of the day was that they had dark spots

445
00:24:04,520 --> 00:24:06,600
Speaker 1: on them, you know, much like the spots that could

446
00:24:06,640 --> 00:24:10,080
Speaker 1: be observed on our own sun, and that this would

447
00:24:10,080 --> 00:24:14,240
Speaker 1: affect visibility. Though theories varied on what those dark spots

448
00:24:14,520 --> 00:24:17,400
Speaker 1: were actually going to be. They might be dark valleys

449
00:24:17,560 --> 00:24:22,000
Speaker 1: or ripples or peaks at a darker core underlying you know,

450
00:24:22,480 --> 00:24:27,800
Speaker 1: outer fluid or gases, um scum, or rock like bodies.

451
00:24:27,880 --> 00:24:31,440
Speaker 1: Even uh, there was all the star scum, yes, your

452
00:24:31,520 --> 00:24:34,159
Speaker 1: star scum. And then there was this cool idea that

453
00:24:34,480 --> 00:24:38,240
Speaker 1: that was also thrown around that you might have flattened stars.

454
00:24:39,200 --> 00:24:40,600
Speaker 1: So these would have been I guess kind of like

455
00:24:41,760 --> 00:24:46,320
Speaker 1: kind of like lenses rotating disks. Yeah, And so if it,

456
00:24:46,400 --> 00:24:49,480
Speaker 1: depending on what how it was facing you, it would

457
00:24:49,600 --> 00:24:52,200
Speaker 1: affect luminosity. So if it turned its edge to you,

458
00:24:52,480 --> 00:24:56,280
Speaker 1: there would obviously be a lot less illumination. So it's

459
00:24:56,359 --> 00:24:58,720
Speaker 1: not exactly the same principle, but I can see that

460
00:24:58,840 --> 00:25:03,320
Speaker 1: being an interesting inside preceding the discovery of things like pulsars.

461
00:25:04,760 --> 00:25:06,879
Speaker 1: So they pondered the structure of the cosmos and the

462
00:25:06,960 --> 00:25:10,280
Speaker 1: nature of stars and eventually hit upon a rather i

463
00:25:10,320 --> 00:25:13,280
Speaker 1: would say, haunting idea. And this was in Sight three.

464
00:25:13,880 --> 00:25:17,520
Speaker 1: What if a star was was massive enough, large enough

465
00:25:17,560 --> 00:25:21,480
Speaker 1: that it attracted back upon itself all the light it admitted,

466
00:25:21,880 --> 00:25:24,600
Speaker 1: in other words, so massive that light itself could not

467
00:25:24,800 --> 00:25:30,560
Speaker 1: achieve escape velocity. This was the idea of the dark star. WHOA,

468
00:25:31,080 --> 00:25:34,520
Speaker 1: Now we should give a little more context and explanation

469
00:25:34,600 --> 00:25:36,560
Speaker 1: to what they're thinking was here. But I have to

470
00:25:36,680 --> 00:25:40,240
Speaker 1: say the name of this paper because it's crazy. The

471
00:25:40,400 --> 00:25:44,600
Speaker 1: paper by John michelle In, presented at the Royal Society

472
00:25:44,600 --> 00:25:47,160
Speaker 1: of London in seven in seventeen eighty three and eighty

473
00:25:47,200 --> 00:25:51,560
Speaker 1: four was quote on the means of discovering the distance, magnitude,

474
00:25:51,680 --> 00:25:55,280
Speaker 1: etcetera of the fixed stars in consequence of the diminution

475
00:25:55,400 --> 00:25:58,000
Speaker 1: of the velocity of their light. In case such a

476
00:25:58,080 --> 00:26:00,920
Speaker 1: diminution should be found to take play sent any of them,

477
00:26:01,200 --> 00:26:04,639
Speaker 1: and such other data should be procured from observations as

478
00:26:04,680 --> 00:26:07,800
Speaker 1: would be farther necessary for that purpose. That's a pretty

479
00:26:07,840 --> 00:26:09,440
Speaker 1: good one. It's got a ring to it. He needs

480
00:26:09,480 --> 00:26:11,680
Speaker 1: like a social media editor working with him. And you

481
00:26:11,800 --> 00:26:15,720
Speaker 1: get that title down. Yeah, So what's what's the clickbait

482
00:26:15,800 --> 00:26:18,879
Speaker 1: title of this paper? Oh you gotta you gotta some

483
00:26:19,000 --> 00:26:21,520
Speaker 1: help fit um. You know a gobbling star in there.

484
00:26:21,960 --> 00:26:24,840
Speaker 1: Let's see, I tried to measure the massive binary stars.

485
00:26:24,920 --> 00:26:28,359
Speaker 1: You can't You won't believe what happened next by the

486
00:26:28,440 --> 00:26:31,720
Speaker 1: way that they figured that. Uh that if you have

487
00:26:31,840 --> 00:26:33,680
Speaker 1: a dark star like this. This would be the case

488
00:26:33,760 --> 00:26:35,960
Speaker 1: if you had a star as dense as our sun,

489
00:26:36,040 --> 00:26:39,159
Speaker 1: but with a radius four nineties seven times larger, and

490
00:26:39,200 --> 00:26:42,320
Speaker 1: it's such it would be difficult to optically observe such

491
00:26:42,359 --> 00:26:45,960
Speaker 1: a star. Yeah, so what what was Michelle doing in

492
00:26:46,000 --> 00:26:48,760
Speaker 1: this paper? As I just alluded to, his main goal,

493
00:26:48,880 --> 00:26:51,720
Speaker 1: the more banal goal was to measure the mass of

494
00:26:51,840 --> 00:26:54,600
Speaker 1: binary stars. So he was armed with, as you said,

495
00:26:54,680 --> 00:26:58,080
Speaker 1: Newton's gravitational laws. People were excited about Newton at the time.

496
00:26:58,160 --> 00:27:01,080
Speaker 1: What you could learn by using Newton so, uh, the

497
00:27:01,200 --> 00:27:04,240
Speaker 1: laws guiding planetary orbits, and he had those in hand,

498
00:27:04,600 --> 00:27:07,040
Speaker 1: and with those you could calculate the masses of two

499
00:27:07,119 --> 00:27:09,960
Speaker 1: stars in a binary system by observing the way they

500
00:27:10,119 --> 00:27:12,520
Speaker 1: orbit one another over the years. If you know how

501
00:27:12,640 --> 00:27:15,159
Speaker 1: wide their orbit is and how long it takes them

502
00:27:15,200 --> 00:27:18,840
Speaker 1: to orbit, you can estimate their mass. But Michell also

503
00:27:19,000 --> 00:27:22,320
Speaker 1: explored the limits of light, so he was working on

504
00:27:22,440 --> 00:27:24,879
Speaker 1: this assumption that light was composed of what was known

505
00:27:24,920 --> 00:27:28,320
Speaker 1: at the time as corpuscles. That makes the light sound

506
00:27:28,400 --> 00:27:31,320
Speaker 1: very romantic, I know, and kind of organic as well. Yeah.

507
00:27:31,400 --> 00:27:35,040
Speaker 1: So the corepuscles of light collections of particles, which, given

508
00:27:35,160 --> 00:27:37,280
Speaker 1: what we know about light today is sort of partially

509
00:27:37,400 --> 00:27:40,840
Speaker 1: correct and partially incorrect, right like we know we know

510
00:27:40,960 --> 00:27:43,560
Speaker 1: it's now given that light can be measured in particle

511
00:27:43,680 --> 00:27:46,399
Speaker 1: units known as photons, but can also behave like a wave.

512
00:27:46,800 --> 00:27:50,080
Speaker 1: But operating on this earlier assumption that light was composed

513
00:27:50,160 --> 00:27:53,960
Speaker 1: of these corpuscles these particles, Michell noted that light, like

514
00:27:54,119 --> 00:27:58,000
Speaker 1: anything else, must have an escape velocity. So the normal

515
00:27:58,080 --> 00:28:00,359
Speaker 1: illustration of this is you stand on the evace of

516
00:28:00,400 --> 00:28:02,600
Speaker 1: the Earth, you throw a baseball straight up in the

517
00:28:02,680 --> 00:28:05,680
Speaker 1: air at a hundred kilometers an hour, it'll fall back

518
00:28:05,680 --> 00:28:07,359
Speaker 1: down to the ground. And if you throw it at

519
00:28:07,400 --> 00:28:10,200
Speaker 1: two hundred kilometers an hour, it will travel up farther,

520
00:28:10,400 --> 00:28:12,600
Speaker 1: but it will still fall back down. If you just

521
00:28:12,840 --> 00:28:16,040
Speaker 1: keep throwing it up at greater and greater velocities each time,

522
00:28:16,080 --> 00:28:18,679
Speaker 1: eventually it's going to reach a velocity where, if it's

523
00:28:18,720 --> 00:28:21,320
Speaker 1: at the right angle, it doesn't fall straight back down

524
00:28:21,359 --> 00:28:23,760
Speaker 1: to the ground, but instead can go into orbit around

525
00:28:23,800 --> 00:28:26,080
Speaker 1: the planet. And if you keep throwing it straight up

526
00:28:26,160 --> 00:28:29,600
Speaker 1: at a great enough velocity, eventually it will actually escape

527
00:28:29,640 --> 00:28:32,119
Speaker 1: the planet's gravity and fly off into space and not

528
00:28:32,440 --> 00:28:35,800
Speaker 1: fall back down to Earth. And specifically, how fast an

529
00:28:35,880 --> 00:28:39,680
Speaker 1: object needs to be traveling to leave Earth's gravity is

530
00:28:39,840 --> 00:28:42,040
Speaker 1: eleven point two kilometers per second. If you can go

531
00:28:42,200 --> 00:28:44,520
Speaker 1: that fast, you can leave. If not, you're stuck here

532
00:28:44,560 --> 00:28:47,160
Speaker 1: with the rest of us. Uh. And a funny side

533
00:28:47,200 --> 00:28:49,680
Speaker 1: here is that you ever think about the idea of

534
00:28:49,720 --> 00:28:54,040
Speaker 1: a terrestrial alien planet with so much mass essentially that

535
00:28:54,160 --> 00:28:57,640
Speaker 1: it prohibits the aliens who live there from practicing space

536
00:28:57,720 --> 00:29:02,080
Speaker 1: exploration when also to just so so stocky they had

537
00:29:02,160 --> 00:29:04,600
Speaker 1: trouble with it. Yeah, I mean, who knows how that

538
00:29:04,600 --> 00:29:07,240
Speaker 1: would change their culture and all that. But uh, but yeah,

539
00:29:07,280 --> 00:29:09,520
Speaker 1: I mean you could imagine a more massive planet that

540
00:29:09,640 --> 00:29:13,080
Speaker 1: had a greater escape velocity might just make it the

541
00:29:13,120 --> 00:29:15,360
Speaker 1: case that you could never come up with a technology

542
00:29:15,480 --> 00:29:17,840
Speaker 1: that could get you out of the planet's gravity. Well,

543
00:29:18,040 --> 00:29:21,040
Speaker 1: this is my entire read on the the the horror

544
00:29:21,080 --> 00:29:23,920
Speaker 1: film phantasm, by the way, is that they have that

545
00:29:24,080 --> 00:29:26,280
Speaker 1: portal that goes to another world. Well, how did they

546
00:29:26,320 --> 00:29:29,560
Speaker 1: get here in the first place? Yeah, I guess they

547
00:29:29,600 --> 00:29:31,840
Speaker 1: sent the tall man. And the tall man is tall

548
00:29:31,960 --> 00:29:34,920
Speaker 1: because he's supposed to be on a high gravity planet,

549
00:29:34,960 --> 00:29:36,960
Speaker 1: and it like you know, straightens them out and makes

550
00:29:37,000 --> 00:29:38,720
Speaker 1: them taller on our planet. And then they have to

551
00:29:38,760 --> 00:29:41,479
Speaker 1: crunch those corpses down into dwarves so that they can

552
00:29:41,600 --> 00:29:45,320
Speaker 1: labor on the on the high gravity world. You know,

553
00:29:45,480 --> 00:29:48,800
Speaker 1: it's it's a really smart concept. It it really gets

554
00:29:48,840 --> 00:29:52,880
Speaker 1: at things that make you think, uh phantasm, Yeah, yeah,

555
00:29:53,200 --> 00:29:56,120
Speaker 1: I mean, it's just mysterious enough to get your brain working,

556
00:29:56,320 --> 00:29:59,040
Speaker 1: you know. Oh you know when Silicon Valley saw that ball,

557
00:29:59,160 --> 00:30:00,880
Speaker 1: they were all like, I could to design one of those.

558
00:30:01,040 --> 00:30:06,000
Speaker 1: I can make that ball. Yeah I Pentagon, come on, yeah,

559
00:30:06,920 --> 00:30:09,720
Speaker 1: I one day, we'll see him. Now. So coming back

560
00:30:09,800 --> 00:30:13,720
Speaker 1: to John Michelle, So what he believed was that you

561
00:30:13,800 --> 00:30:16,040
Speaker 1: got these core pustles of light and they they've got

562
00:30:16,120 --> 00:30:18,160
Speaker 1: an escape velocity as well, and what they have to

563
00:30:18,240 --> 00:30:20,360
Speaker 1: do to shine away from a star is escape the

564
00:30:20,400 --> 00:30:25,000
Speaker 1: stars gravity. And fortunately, as Michelle, light travels very very fast,

565
00:30:25,120 --> 00:30:28,080
Speaker 1: so this doesn't normally happen. But he realized as we

566
00:30:28,160 --> 00:30:30,600
Speaker 1: were saying, that if a star have has enough mass,

567
00:30:31,120 --> 00:30:34,040
Speaker 1: even according to this new Tonian model of physics, before

568
00:30:34,080 --> 00:30:38,320
Speaker 1: we had relativity, before we had Einstein, even on Newtonian mechanics,

569
00:30:38,880 --> 00:30:42,160
Speaker 1: you could imagine a star so big with so much

570
00:30:42,200 --> 00:30:45,280
Speaker 1: gravity that even light could not escape it and would

571
00:30:45,280 --> 00:30:47,920
Speaker 1: always get pulled back down. And like you said Robert.

572
00:30:48,280 --> 00:30:51,120
Speaker 1: The number he came up with was that a star

573
00:30:51,360 --> 00:30:54,280
Speaker 1: four hundred and ninety seven times the escape velocity of

574
00:30:54,320 --> 00:30:57,720
Speaker 1: our sun would prevent all light from leaving. And to

575
00:30:57,800 --> 00:31:01,280
Speaker 1: read a quote from Michelle's work, the existence of bodies

576
00:31:01,360 --> 00:31:04,920
Speaker 1: under these circumstances, we could have no information from sight.

577
00:31:05,480 --> 00:31:09,720
Speaker 1: Yet if other luminous bodies should happen to revolve about them,

578
00:31:10,240 --> 00:31:13,800
Speaker 1: we might still perhaps from the motions of those revolving bodies,

579
00:31:13,920 --> 00:31:17,320
Speaker 1: infer the existence of the central ones with some degree

580
00:31:17,360 --> 00:31:20,680
Speaker 1: of probability, as this might afford a clue to some

581
00:31:20,840 --> 00:31:24,520
Speaker 1: of the apparent irregularities of revolving bodies, which would not

582
00:31:24,680 --> 00:31:29,200
Speaker 1: be easily explicable on any other hypothesis. So Michelle's planting

583
00:31:29,240 --> 00:31:32,680
Speaker 1: a clue there for how we could detect black holes

584
00:31:32,800 --> 00:31:36,360
Speaker 1: or objects that did not allow light to escape before

585
00:31:36,480 --> 00:31:39,680
Speaker 1: we've even discovered relativity. And I wanted to drive home

586
00:31:39,720 --> 00:31:44,920
Speaker 1: again that this was the eighteenth century. Yeah, this is so,

587
00:31:45,080 --> 00:31:47,040
Speaker 1: this is this is pretty out their thought from the

588
00:31:47,120 --> 00:31:49,760
Speaker 1: time by by far. And I should point out that

589
00:31:49,960 --> 00:31:52,480
Speaker 1: Sir William Herschel also argued on the basis of the

590
00:31:52,560 --> 00:31:56,400
Speaker 1: particulate theory of light the corpuscles that nebulae could be

591
00:31:56,520 --> 00:32:00,440
Speaker 1: made of agglomerations of particles of light captured by gravity,

592
00:32:00,480 --> 00:32:02,880
Speaker 1: is sort of sort of held in place by gravity.

593
00:32:03,360 --> 00:32:06,600
Speaker 1: So essentially that we have the groundwork here for what

594
00:32:06,680 --> 00:32:09,320
Speaker 1: would eventually become the concept of a black hole, even

595
00:32:09,360 --> 00:32:11,760
Speaker 1: though they certainly were not calling it a black hole. No,

596
00:32:12,240 --> 00:32:15,200
Speaker 1: and uh one more thinker, we should mention somebody who

597
00:32:15,320 --> 00:32:18,760
Speaker 1: often gets credited, maybe more often than Michelle, or at

598
00:32:18,840 --> 00:32:21,080
Speaker 1: least used to get credited more often than John Michelle

599
00:32:21,560 --> 00:32:25,680
Speaker 1: is Pierre Simon de Laplace. So, in seventeen ninety six,

600
00:32:25,800 --> 00:32:28,480
Speaker 1: with the upheaval of the French Revolution still in effect,

601
00:32:28,880 --> 00:32:32,880
Speaker 1: the French astronomer and general scholar kind of Renaissance Guy

602
00:32:33,240 --> 00:32:37,600
Speaker 1: Pierre Simon de Laplace published Exposition du System dumont or

603
00:32:37,680 --> 00:32:40,000
Speaker 1: the System of the World, And in this book he

604
00:32:40,160 --> 00:32:45,000
Speaker 1: hypothesized the existence of cores, obscures, or hidden bodies or

605
00:32:45,200 --> 00:32:48,560
Speaker 1: dark bodies of those dark bodies out there. So so

606
00:32:48,720 --> 00:32:51,960
Speaker 1: he wrote, quote, a luminous star of the same density

607
00:32:52,040 --> 00:32:54,560
Speaker 1: as the Earth, and whose diameter should be two hundred

608
00:32:54,560 --> 00:32:57,760
Speaker 1: and fifty times larger than that of the Sun, would not,

609
00:32:58,320 --> 00:33:01,360
Speaker 1: in consequence of its attraction and allow any of its

610
00:33:01,480 --> 00:33:04,440
Speaker 1: rays to arrive at us. It is therefore possible that

611
00:33:04,560 --> 00:33:08,040
Speaker 1: the largest luminous bodies in the universe may, through this cause,

612
00:33:08,560 --> 00:33:12,840
Speaker 1: be invisible. Now, notice that Laplace estimated a different required

613
00:33:12,920 --> 00:33:15,040
Speaker 1: size to prevent the escape of light. This is because

614
00:33:15,080 --> 00:33:18,080
Speaker 1: he expected stars to have a different density than Michelle did.

615
00:33:18,400 --> 00:33:21,000
Speaker 1: But either way, I love that idea. So he's saying,

616
00:33:21,240 --> 00:33:24,120
Speaker 1: it's possible that the biggest things out there in the

617
00:33:24,280 --> 00:33:27,280
Speaker 1: universe are completely invisible to us. We we wouldn't even

618
00:33:27,320 --> 00:33:29,840
Speaker 1: know they were there. Now, rounding up from this, we

619
00:33:29,920 --> 00:33:33,320
Speaker 1: know that Michelle and Laplace were certainly ahead of their time,

620
00:33:33,360 --> 00:33:35,440
Speaker 1: but they were also wrong about a lot of stuff,

621
00:33:35,600 --> 00:33:38,280
Speaker 1: just owing to the time that they lived. Like that,

622
00:33:38,400 --> 00:33:40,680
Speaker 1: they didn't know lots of things about physics and about

623
00:33:40,720 --> 00:33:43,360
Speaker 1: astronomy that we did. When they imagine stars getting so

624
00:33:43,520 --> 00:33:46,080
Speaker 1: big that no light could escape their gravity, they imagine,

625
00:33:46,120 --> 00:33:49,120
Speaker 1: for one thing, stars scaling up simply by getting bigger

626
00:33:49,240 --> 00:33:52,560
Speaker 1: at a constant density. And then they also imagined light

627
00:33:52,720 --> 00:33:55,880
Speaker 1: being a projection of particles that would be slowed down

628
00:33:56,040 --> 00:33:59,480
Speaker 1: by gravity. So let's complicate the picture with some Einstein.

629
00:34:00,200 --> 00:34:02,840
Speaker 1: Let's do it. We're into the twentieth century now, during

630
00:34:02,880 --> 00:34:06,680
Speaker 1: the opening decades of the twentieth century German theoretical physicist

631
00:34:06,880 --> 00:34:09,240
Speaker 1: Albert Einstein in is the picture. He was born eighteen

632
00:34:09,280 --> 00:34:12,719
Speaker 1: seventy nine died ninety and he gave us a new

633
00:34:12,880 --> 00:34:16,680
Speaker 1: theory of gravitation, the general theory of relativity, and it

634
00:34:16,880 --> 00:34:21,200
Speaker 1: entails the idea that massive objects distort space time. And

635
00:34:21,320 --> 00:34:23,960
Speaker 1: we experienced this as gravity. Okay, So this is a

636
00:34:24,239 --> 00:34:26,480
Speaker 1: change in the idea of gravity. Instead of being a

637
00:34:26,680 --> 00:34:31,200
Speaker 1: force that that objects exert on each other, general relativity

638
00:34:31,200 --> 00:34:35,520
Speaker 1: imagines gravity as indentations in the geometry of the space

639
00:34:35,600 --> 00:34:38,560
Speaker 1: time we inhabit. That's right. Now, there's a there's a

640
00:34:38,560 --> 00:34:41,080
Speaker 1: wonderful experiment that I always like to fall back on

641
00:34:41,680 --> 00:34:43,360
Speaker 1: to kind of explain this, And in fact, there's a

642
00:34:43,480 --> 00:34:45,239
Speaker 1: video of this on stuff to Blow your Mind dot com,

643
00:34:45,280 --> 00:34:46,680
Speaker 1: and i'll i'll try and put a link to it

644
00:34:46,719 --> 00:34:49,360
Speaker 1: on the landing page for this episode. But basically it

645
00:34:49,400 --> 00:34:52,760
Speaker 1: involves taking a plastic sheet, having it stretched out generally

646
00:34:52,840 --> 00:34:55,240
Speaker 1: like if you stretch it over a hula hoop, okay,

647
00:34:55,760 --> 00:35:00,160
Speaker 1: and then you apply weighted balls onto the sheet, so

648
00:35:00,360 --> 00:35:01,800
Speaker 1: you know, you might have something that's the size of

649
00:35:01,840 --> 00:35:05,239
Speaker 1: a baseball up until up up scaling up to things

650
00:35:05,280 --> 00:35:07,759
Speaker 1: about the size of say a bowling ball, all right,

651
00:35:07,840 --> 00:35:10,960
Speaker 1: and when you place those on the sheet, it distorts

652
00:35:11,080 --> 00:35:13,560
Speaker 1: the sheet. It distorts the space time that is the

653
00:35:13,640 --> 00:35:17,120
Speaker 1: surface of that sheet. Right, So normal planets and stars

654
00:35:17,239 --> 00:35:19,759
Speaker 1: might be things on the sheets sort of like baseballs

655
00:35:19,880 --> 00:35:23,000
Speaker 1: or golf balls or something causing these small indentations where

656
00:35:23,280 --> 00:35:26,640
Speaker 1: generally things can move around them and not cause there

657
00:35:26,640 --> 00:35:28,440
Speaker 1: wouldn't really be much of an issue until you got

658
00:35:28,560 --> 00:35:30,480
Speaker 1: very close, and then you'd start to kind of circle

659
00:35:30,520 --> 00:35:33,560
Speaker 1: around or have your path diverted as you passed by

660
00:35:33,680 --> 00:35:36,759
Speaker 1: one of them, owing to the indentations they make in

661
00:35:36,840 --> 00:35:40,359
Speaker 1: the topography of the sheet. But imagine you've got, say,

662
00:35:40,440 --> 00:35:43,279
Speaker 1: like a big hunk of depleted uranium, and you put

663
00:35:43,360 --> 00:35:45,480
Speaker 1: that on the sheet like the densest thing you can

664
00:35:45,560 --> 00:35:48,719
Speaker 1: come across, and it's gonna bend the sheet down in

665
00:35:48,840 --> 00:35:52,720
Speaker 1: this crazy kind of suction that will for a certain

666
00:35:52,840 --> 00:35:55,399
Speaker 1: radius around it pull all kinds of stuff in. Yeah,

667
00:35:55,400 --> 00:35:57,480
Speaker 1: you try and roll a marble then across the sheet,

668
00:35:57,520 --> 00:35:59,279
Speaker 1: and it doesn't stand a chance it's going to be

669
00:35:59,320 --> 00:36:02,719
Speaker 1: sucked in. Can't it can't say roll past and just

670
00:36:02,800 --> 00:36:06,000
Speaker 1: get its path diverted. Suddenly things will just get sucked

671
00:36:06,040 --> 00:36:08,440
Speaker 1: all the way in and never come out. And so this,

672
00:36:08,600 --> 00:36:11,240
Speaker 1: in essence is the general theory of relativity. And again

673
00:36:11,280 --> 00:36:14,520
Speaker 1: it differs from the Newtonian model in which gravity wasn't

674
00:36:14,560 --> 00:36:17,240
Speaker 1: innate force, right, which Newton didn't know how to explain,

675
00:36:17,360 --> 00:36:19,839
Speaker 1: and I respect he didn't try to explain. He just said,

676
00:36:19,880 --> 00:36:22,160
Speaker 1: this is how it is. I'll write equations showing you

677
00:36:22,520 --> 00:36:24,279
Speaker 1: how to solve for it and how to predict how

678
00:36:24,320 --> 00:36:26,000
Speaker 1: it works. But I'm not going to say what it is.

679
00:36:26,760 --> 00:36:29,120
Speaker 1: Now We've got a pretty idea what it actually is,

680
00:36:29,520 --> 00:36:34,319
Speaker 1: and it's these these distortions in the geometry of space time.

681
00:36:34,560 --> 00:36:36,879
Speaker 1: The funny thing about that is, I think how often

682
00:36:37,000 --> 00:36:39,960
Speaker 1: we still talk about gravity as a force, as if

683
00:36:39,960 --> 00:36:42,960
Speaker 1: it were some kind of like magnetism attracting matter. I mean,

684
00:36:43,080 --> 00:36:47,439
Speaker 1: I honestly think about it that way most of the time. Yeah.

685
00:36:47,440 --> 00:36:50,000
Speaker 1: I mean again, we have to fall back on on

686
00:36:50,160 --> 00:36:54,600
Speaker 1: our experience, and that ends up coloring what we think

687
00:36:54,680 --> 00:36:58,800
Speaker 1: we know about the cosmos. Yeah. And so Einstein definitely

688
00:36:58,840 --> 00:37:01,120
Speaker 1: put he put together the theory radical framework for how

689
00:37:01,239 --> 00:37:05,319
Speaker 1: general relativity works. But one thing you might wonder is, like, Okay, well,

690
00:37:05,440 --> 00:37:08,560
Speaker 1: let's say we're really into Einstein's theory of general relativity.

691
00:37:08,840 --> 00:37:11,480
Speaker 1: How would you ever test whether such a thing were true?

692
00:37:12,080 --> 00:37:14,120
Speaker 1: You know, if you could do all of your Newtonian

693
00:37:14,200 --> 00:37:17,800
Speaker 1: experiments just using Newtonian physics and get the right answers

694
00:37:17,880 --> 00:37:21,520
Speaker 1: on Earth, how would you test to see whether Einstein's

695
00:37:21,560 --> 00:37:25,359
Speaker 1: theory was actually better? So there did come along some demonstrations,

696
00:37:25,440 --> 00:37:27,759
Speaker 1: and one of them, one that proved very decisive for

697
00:37:27,840 --> 00:37:32,120
Speaker 1: public opinion, was in nineteen nineteen when the English astrophysicist

698
00:37:32,239 --> 00:37:35,120
Speaker 1: Arthur Eddington carried out an experiment to test the predictions

699
00:37:35,160 --> 00:37:37,520
Speaker 1: of Einstein's theory. And I think we've talked about this

700
00:37:37,600 --> 00:37:40,280
Speaker 1: experiment on the show before, but one of the predictions

701
00:37:40,320 --> 00:37:43,480
Speaker 1: of general relativity is that light passing directly by a

702
00:37:43,560 --> 00:37:46,960
Speaker 1: massive object like a star should actually be bent by

703
00:37:47,000 --> 00:37:50,720
Speaker 1: a specific predictable amount, depending on how massive the object

704
00:37:50,880 --> 00:37:53,160
Speaker 1: is and how close the light passes. And so a

705
00:37:53,200 --> 00:37:56,040
Speaker 1: pretty easy way to test this would be by say,

706
00:37:56,120 --> 00:37:58,920
Speaker 1: taking a picture of the star field at night and

707
00:37:59,080 --> 00:38:01,760
Speaker 1: noting where all of the stars are, getting the locations

708
00:38:01,800 --> 00:38:04,840
Speaker 1: of those stars, and then watching what happens when the

709
00:38:05,080 --> 00:38:08,720
Speaker 1: Sun passes between the Earth and those stars. It should

710
00:38:08,840 --> 00:38:12,520
Speaker 1: be if Einstein's theory is right, that the light coming

711
00:38:12,600 --> 00:38:15,399
Speaker 1: to us from the star behind the Sun should get

712
00:38:15,560 --> 00:38:18,080
Speaker 1: bent as it's coming right past the Sun. So when

713
00:38:18,120 --> 00:38:20,640
Speaker 1: it's right beside the edge of the Sun, our view

714
00:38:20,719 --> 00:38:23,960
Speaker 1: of it should be displaced and distorted by a very predictable,

715
00:38:24,080 --> 00:38:27,960
Speaker 1: certain small but certain amount. But part of the problem is, well,

716
00:38:28,000 --> 00:38:30,879
Speaker 1: how do you test that, Like, can you usually look

717
00:38:30,960 --> 00:38:34,319
Speaker 1: at the stars if you're looking also at the sun. Yes,

718
00:38:34,520 --> 00:38:37,120
Speaker 1: you need something, you need something special to happen, something

719
00:38:37,239 --> 00:38:39,880
Speaker 1: that that that blocks out the sign. If only there

720
00:38:39,920 --> 00:38:43,000
Speaker 1: were some other object in the sky that was just

721
00:38:43,320 --> 00:38:46,040
Speaker 1: the right size to do that. And for we're very

722
00:38:46,160 --> 00:38:50,480
Speaker 1: fortunate to live in that laboratory by accident. So Earth's

723
00:38:50,840 --> 00:38:53,239
Speaker 1: Earth is very privileged. And here's one way that the

724
00:38:53,280 --> 00:38:56,080
Speaker 1: Copernican principle seems to fail. Earth is very privileged, and

725
00:38:56,160 --> 00:38:58,839
Speaker 1: that our moon is just about the same size as

726
00:38:58,920 --> 00:39:02,279
Speaker 1: the Sun, apparently from our perspective. So the Moon can

727
00:39:02,440 --> 00:39:06,160
Speaker 1: block out the Sun's light during a solar eclipse. And

728
00:39:06,280 --> 00:39:08,239
Speaker 1: if you wait for a solar eclipse, you actually could

729
00:39:08,320 --> 00:39:10,680
Speaker 1: look at the stars that are shooting light at you

730
00:39:10,920 --> 00:39:14,640
Speaker 1: from right beside the Sun from your perspective. So the

731
00:39:14,800 --> 00:39:17,359
Speaker 1: Eddington experiment waited for a solar eclipse when the moon

732
00:39:17,440 --> 00:39:19,920
Speaker 1: passed in front of the Sun, and that eclipse came

733
00:39:19,960 --> 00:39:23,920
Speaker 1: in May nineteen nineteen, passing over Eddington's experimental station on

734
00:39:24,040 --> 00:39:27,080
Speaker 1: prin Cape Island off the western coast of Africa, and

735
00:39:27,239 --> 00:39:30,160
Speaker 1: also over some uh some other astronomers working in the

736
00:39:30,200 --> 00:39:33,839
Speaker 1: Amazon rainforest. And so the eclipse dimmed the light from

737
00:39:33,880 --> 00:39:36,440
Speaker 1: the Sun enough for Ddington and colleagues to take photos

738
00:39:36,480 --> 00:39:39,160
Speaker 1: of the starfield in the background, and they found that

739
00:39:39,239 --> 00:39:41,920
Speaker 1: the Sun did indeed bend the light from the stars

740
00:39:42,080 --> 00:39:43,920
Speaker 1: right around it, and the light was bent by the

741
00:39:43,960 --> 00:39:48,040
Speaker 1: amount predicted by Einstein's general relativity. So this experiment was

742
00:39:48,120 --> 00:39:51,279
Speaker 1: a huge international sensation. It was in all the newspapers,

743
00:39:51,360 --> 00:39:54,440
Speaker 1: and it made Einstein a celebrity. Kind of makes me wonder,

744
00:39:54,560 --> 00:39:58,719
Speaker 1: like what sort of scientific experiment would make headlines in

745
00:39:58,880 --> 00:40:04,560
Speaker 1: major newspapers like front page headlines in major newspapers today. Well, uh,

746
00:40:05,040 --> 00:40:07,960
Speaker 1: skipping ahead a little bit here, but I believe gravitational

747
00:40:08,040 --> 00:40:13,360
Speaker 1: waves uh made some some headlines. They made some I mean, like,

748
00:40:13,680 --> 00:40:16,160
Speaker 1: can you imagine them as like top banner, like beating

749
00:40:16,200 --> 00:40:18,520
Speaker 1: out all the politics and everything like that. Yeah, it

750
00:40:18,680 --> 00:40:22,880
Speaker 1: is it is difficult to imagine it, but yeah, I

751
00:40:23,400 --> 00:40:25,680
Speaker 1: want to say we still have some some hits on

752
00:40:25,800 --> 00:40:29,160
Speaker 1: the way maybe maybe. So now we know that even

753
00:40:29,200 --> 00:40:31,960
Speaker 1: those stars can't slow down light. One of the key

754
00:40:32,040 --> 00:40:34,920
Speaker 1: features of Einstein's work is that the principle of the

755
00:40:35,000 --> 00:40:38,239
Speaker 1: speed of light and a vacuum never changes. Right. We

756
00:40:38,400 --> 00:40:41,680
Speaker 1: do know that very massive objects bend light as the

757
00:40:41,800 --> 00:40:45,359
Speaker 1: light travels along its trajectory through spacetime very near them.

758
00:40:45,920 --> 00:40:48,960
Speaker 1: And this is where we are going to introduce somebody

759
00:40:49,000 --> 00:40:51,880
Speaker 1: who changed the game when it comes to black holes,

760
00:40:52,080 --> 00:40:55,440
Speaker 1: and that is Carl Schwartzhield. We will discuss him when

761
00:40:55,520 --> 00:40:59,640
Speaker 1: we come back from a break. Than alright, we're back,

762
00:41:00,040 --> 00:41:03,120
Speaker 1: So Robert, take us into the mind of Karl schwartz Shield.

763
00:41:03,440 --> 00:41:06,880
Speaker 1: All right, So Karl schwartz Field was a German physicist

764
00:41:06,960 --> 00:41:12,000
Speaker 1: and astronomer. He lived only eighteen seventy three through nineteen sixteen.

765
00:41:12,400 --> 00:41:14,880
Speaker 1: He died in the war. Yeah, now he and I

766
00:41:14,920 --> 00:41:17,160
Speaker 1: should say they should point he did. He died of illness,

767
00:41:17,239 --> 00:41:20,319
Speaker 1: but he did still very much die during the First

768
00:41:20,360 --> 00:41:24,080
Speaker 1: World World War. Uh. And he calculated the possibility of

769
00:41:24,480 --> 00:41:28,960
Speaker 1: an Einsteiny and dark star. Um. He like did this

770
00:41:29,120 --> 00:41:32,560
Speaker 1: while he was in the in the service, I believe. Yeah. Yeah,

771
00:41:33,280 --> 00:41:35,600
Speaker 1: Often it's described as him like being in the trenches.

772
00:41:35,640 --> 00:41:38,359
Speaker 1: I think that, well, we like the room. The room.

773
00:41:38,440 --> 00:41:40,680
Speaker 1: It's a romantic idea, right, the idea that we have

774
00:41:40,880 --> 00:41:43,200
Speaker 1: someone that's in a literal pit and they're in a

775
00:41:43,600 --> 00:41:46,759
Speaker 1: it's a time in in world history that is that

776
00:41:46,960 --> 00:41:52,200
Speaker 1: feels like a pity and a time of just total war, uh,

777
00:41:52,520 --> 00:41:55,200
Speaker 1: encompassing the Earth, and it's seeming like we not, we

778
00:41:55,320 --> 00:41:56,960
Speaker 1: might not be able to climb back out of it.

779
00:41:57,200 --> 00:42:00,680
Speaker 1: And here this, uh, this gentleman is contemp lighting the

780
00:42:00,800 --> 00:42:03,680
Speaker 1: black hole. Yeah. As World War one is changing the

781
00:42:03,760 --> 00:42:07,520
Speaker 1: social fabric of Europe and much of the world, short

782
00:42:07,560 --> 00:42:10,840
Speaker 1: Shield here is changing the fabric of spacetime. Yeah. And

783
00:42:11,000 --> 00:42:15,279
Speaker 1: as a he shorts shorts Field was a very impressive dude,

784
00:42:15,320 --> 00:42:18,040
Speaker 1: though he was again he only lived to be forty

785
00:42:18,080 --> 00:42:20,919
Speaker 1: two years of age. Uh. But during his short life

786
00:42:20,960 --> 00:42:24,800
Speaker 1: he made practical and theoretical contributions to astronomy, and he

787
00:42:25,000 --> 00:42:29,560
Speaker 1: used general relativity equations to demonstrate celestial bodies within enough

788
00:42:29,680 --> 00:42:32,799
Speaker 1: mass would have an escape velocity beyond the speed of light.

789
00:42:33,239 --> 00:42:35,000
Speaker 1: I should also point out that again, even though he

790
00:42:35,400 --> 00:42:37,520
Speaker 1: died at the age of forty two, he had his

791
00:42:37,600 --> 00:42:41,239
Speaker 1: first theoretical physics paper published at the age of sixteen. Yeah.

792
00:42:41,360 --> 00:42:44,080
Speaker 1: He you get the impression that, like you're when you

793
00:42:44,160 --> 00:42:46,200
Speaker 1: read about him, you're sort of in the presence of

794
00:42:46,239 --> 00:42:49,719
Speaker 1: one of those brains. Uh so. Yeah. He he was

795
00:42:49,920 --> 00:42:54,000
Speaker 1: experimenting with different types of geometry for understanding the behavior

796
00:42:54,080 --> 00:42:56,640
Speaker 1: of massive objects like stars, and part of what he

797
00:42:56,760 --> 00:43:00,360
Speaker 1: was doing was trying to work out rigorous solution sans

798
00:43:00,440 --> 00:43:05,600
Speaker 1: to Einstein's equations. Einstein had sort of done the simplified

799
00:43:05,760 --> 00:43:08,680
Speaker 1: version of general relativity, and he's like, surely it'll be

800
00:43:08,760 --> 00:43:11,120
Speaker 1: really hard to work out all of the rigorous, you know,

801
00:43:11,480 --> 00:43:15,319
Speaker 1: precise solutions of my equations. But but swart Shield did,

802
00:43:15,719 --> 00:43:18,480
Speaker 1: and he did this by using a system of spherical coordinates.

803
00:43:18,680 --> 00:43:21,000
Speaker 1: Short Shield discovered that if you imagine the mass of

804
00:43:21,080 --> 00:43:24,800
Speaker 1: a star compressed down to a great density around it

805
00:43:24,880 --> 00:43:28,160
Speaker 1: in all directions reaching out to a specific radius later

806
00:43:28,239 --> 00:43:32,360
Speaker 1: known as the swart Shield radius, would form this gravitational

807
00:43:32,680 --> 00:43:36,479
Speaker 1: dead zone. Anything that went into the dead zone, whether

808
00:43:36,560 --> 00:43:40,440
Speaker 1: it was matter, light, whatever, would never come out again.

809
00:43:41,040 --> 00:43:43,640
Speaker 1: And this spherical dead zone came to be known at

810
00:43:43,680 --> 00:43:47,120
Speaker 1: the time as the schwart Shield sphere. Now we call

811
00:43:47,239 --> 00:43:51,200
Speaker 1: the boundary leading over into this zone today the event horizon,

812
00:43:51,440 --> 00:43:53,240
Speaker 1: and that's where you get the movie title. Of course,

813
00:43:53,760 --> 00:43:56,000
Speaker 1: that's sort of the outer boundary of the zone of

814
00:43:56,160 --> 00:43:59,960
Speaker 1: total influence of the black hole. Because inside this radius,

815
00:44:00,120 --> 00:44:04,360
Speaker 1: inside the event horizon, swart Shield concluded that all radiation

816
00:44:04,440 --> 00:44:07,480
Speaker 1: and matter passing into the sphere would become stuck. And

817
00:44:07,600 --> 00:44:10,399
Speaker 1: of course, under general relativity, if you were flying into

818
00:44:10,480 --> 00:44:15,080
Speaker 1: this sphere, outside, observers would notice your time slowing down

819
00:44:15,280 --> 00:44:18,560
Speaker 1: as you approached the sphere, and to those observers out there,

820
00:44:18,719 --> 00:44:21,680
Speaker 1: you would appear to sort of stop as you crossed over.

821
00:44:22,120 --> 00:44:24,640
Speaker 1: So do the people imagining this object, like, what would

822
00:44:24,640 --> 00:44:28,200
Speaker 1: they picture? Maybe according to this conception, anything entering the

823
00:44:28,280 --> 00:44:31,400
Speaker 1: sphere of the short Shield radius would seem to appear

824
00:44:31,560 --> 00:44:34,239
Speaker 1: frozen forever in time at the moment it was about

825
00:44:34,280 --> 00:44:38,000
Speaker 1: to cross over into the dead zone. Speaking, this made

826
00:44:38,040 --> 00:44:40,640
Speaker 1: me think about one of the videos we watched from

827
00:44:40,640 --> 00:44:42,640
Speaker 1: the World You were there at the event, but one

828
00:44:42,840 --> 00:44:44,799
Speaker 1: that I watched from the World Science Festival this year

829
00:44:44,880 --> 00:44:49,160
Speaker 1: had a astrophysicist Chep Doleman talking about black holes and

830
00:44:49,280 --> 00:44:52,160
Speaker 1: he said, quote, what happens in the black hole stays

831
00:44:52,200 --> 00:44:55,480
Speaker 1: in the black hole. Yeah. I like that. That that

832
00:44:55,640 --> 00:44:58,560
Speaker 1: that oftentimes you see the especially the more modern physicists

833
00:44:58,560 --> 00:45:01,239
Speaker 1: who who have written about black holes that they tend

834
00:45:01,320 --> 00:45:06,319
Speaker 1: to have a sense of humor regarding their nature. Yeah, yeah,

835
00:45:06,360 --> 00:45:09,680
Speaker 1: I think that's generally true, like they don't get all well.

836
00:45:09,719 --> 00:45:12,840
Speaker 1: I mean, so here's what you can contrast that lighthearted

837
00:45:12,880 --> 00:45:17,600
Speaker 1: approach with. Apparently some French speaking astrophysicists took to calling

838
00:45:17,640 --> 00:45:23,399
Speaker 1: the short shield sphere the sphere catastrophe, the sphere that's

839
00:45:23,400 --> 00:45:26,400
Speaker 1: a hard thing to say, sphere catastrophe. I like the

840
00:45:26,480 --> 00:45:28,920
Speaker 1: idea of this, of this is being the avant garde

841
00:45:29,040 --> 00:45:32,800
Speaker 1: French version of the event Arizon. Oh I'd pay to

842
00:45:32,840 --> 00:45:35,120
Speaker 1: see that. I hope it's still have sam Neil. Now

843
00:45:35,200 --> 00:45:39,239
Speaker 1: we go with the instead. Oh yeah, okay, it would be.

844
00:45:39,360 --> 00:45:41,680
Speaker 1: It would be a great version of event Horizon where

845
00:45:41,880 --> 00:45:45,080
Speaker 1: every scene they have fresh baked bread. Now, one thing

846
00:45:45,120 --> 00:45:47,760
Speaker 1: that's worth noting about the sphere of doom, the schwart

847
00:45:47,800 --> 00:45:51,400
Speaker 1: shield sphere or the sphere catastrophe, it's not actually the

848
00:45:51,600 --> 00:45:56,120
Speaker 1: same as the central object, the black hole itself. An

849
00:45:56,160 --> 00:46:00,360
Speaker 1: example given in Marcia Bartosik's black Hole, our son is

850
00:46:00,360 --> 00:46:04,040
Speaker 1: about one point four million kilometers wide. If a star

851
00:46:04,400 --> 00:46:07,920
Speaker 1: the mass of our Sun were compressed down to a point,

852
00:46:08,400 --> 00:46:11,759
Speaker 1: the sphere catastropheke surrounding it would be less than six

853
00:46:11,880 --> 00:46:15,760
Speaker 1: kilometers across. If the mass of ten sons were reduced

854
00:46:15,800 --> 00:46:19,239
Speaker 1: to a point like volume, its sphere catastrophe would be

855
00:46:19,280 --> 00:46:22,680
Speaker 1: about sixty kilometers wide. And as we mentioned earlier, if

856
00:46:22,719 --> 00:46:24,920
Speaker 1: our son were to suddenly shrink down to that size,

857
00:46:24,960 --> 00:46:28,360
Speaker 1: objects far outside the sphere would not suddenly be like

858
00:46:28,560 --> 00:46:32,400
Speaker 1: sucked in or torn apart. The planets would continue orbiting

859
00:46:32,480 --> 00:46:35,200
Speaker 1: just like they orbit the Sun, only it's only much

860
00:46:35,280 --> 00:46:38,239
Speaker 1: closer that things would really go crazy. But here's a

861
00:46:38,320 --> 00:46:41,040
Speaker 1: really important point that we need to drive home. At

862
00:46:41,120 --> 00:46:45,160
Speaker 1: this stage, even after short Shield had done these these calculations,

863
00:46:45,320 --> 00:46:48,640
Speaker 1: most physicists and astronomers did not believe a black hole

864
00:46:48,719 --> 00:46:52,080
Speaker 1: could exist in nature. Uh. Einstein just thought that short

865
00:46:52,120 --> 00:46:55,160
Speaker 1: Shield sphere sphere of doom thing was a sign there

866
00:46:55,200 --> 00:46:57,040
Speaker 1: was still some things to work out in the theory,

867
00:46:57,080 --> 00:46:59,880
Speaker 1: and Einstein did not think that black holes would be

868
00:47:00,040 --> 00:47:03,400
Speaker 1: found in the actual universe. So at the time, the

869
00:47:03,520 --> 00:47:05,360
Speaker 1: idea that it might have just been a mirror ghost

870
00:47:05,480 --> 00:47:08,440
Speaker 1: in the math kind of a remainder that had to

871
00:47:08,480 --> 00:47:10,680
Speaker 1: be figured out later on. Yeah, so you do the

872
00:47:10,800 --> 00:47:13,120
Speaker 1: math and you say, oh, this is a strange finding.

873
00:47:13,320 --> 00:47:16,960
Speaker 1: But people, I think, just assumed, Well, so we'll find

874
00:47:17,040 --> 00:47:19,000
Speaker 1: out something in the future that will make sense of

875
00:47:19,040 --> 00:47:22,000
Speaker 1: all this, you know, we will have some kind of observation,

876
00:47:22,160 --> 00:47:25,279
Speaker 1: some update to the theory, something that will eventually let

877
00:47:25,400 --> 00:47:27,960
Speaker 1: us know, oh, okay, there's not actually such a thing

878
00:47:28,000 --> 00:47:29,960
Speaker 1: as a black hole. They weren't calling it a black

879
00:47:30,000 --> 00:47:32,160
Speaker 1: hole at the time, but there's not actually one of

880
00:47:32,239 --> 00:47:35,000
Speaker 1: these to be found in nature. Something prevents this from happening.

881
00:47:35,640 --> 00:47:38,799
Speaker 1: So remember Arthur Eddington, the English astro physicist who did

882
00:47:38,840 --> 00:47:43,160
Speaker 1: the eclipse experiment about general relativity. In his nineteen book

883
00:47:43,239 --> 00:47:46,279
Speaker 1: The Internal Constitution of the Stars, he wrote, I think,

884
00:47:46,719 --> 00:47:50,320
Speaker 1: kind of dryly, invoking some awesome imagery, I might add quote,

885
00:47:51,520 --> 00:47:54,440
Speaker 1: a star of two d and fifty million kilometers radius

886
00:47:54,760 --> 00:47:58,440
Speaker 1: could not possibly have so high a density as the Sun. Firstly,

887
00:47:58,560 --> 00:48:01,319
Speaker 1: the force of gravitation would so great that light would

888
00:48:01,320 --> 00:48:04,400
Speaker 1: be unable to escape it, the rays falling back to

889
00:48:04,480 --> 00:48:07,279
Speaker 1: the star like a stone to the Earth. Secondly, the

890
00:48:07,400 --> 00:48:10,040
Speaker 1: red shift of the spectral lines would be so great

891
00:48:10,120 --> 00:48:13,440
Speaker 1: that the spectrum would be shifted out of existence. Thirdly,

892
00:48:13,800 --> 00:48:17,320
Speaker 1: the mass would produce so much curvature of the space

893
00:48:17,440 --> 00:48:21,640
Speaker 1: time metric that space would close up around the star,

894
00:48:22,239 --> 00:48:27,160
Speaker 1: leaving us outside i e. Nowhere. So the idea is

895
00:48:27,239 --> 00:48:30,600
Speaker 1: that it would can suddenly contain all of space, and

896
00:48:30,640 --> 00:48:32,960
Speaker 1: then we couldn't be in space anymore. Well, when you

897
00:48:33,000 --> 00:48:34,800
Speaker 1: put it like that, it does sound like a like

898
00:48:34,880 --> 00:48:37,719
Speaker 1: a mathematical problem that has to be worked out later on.

899
00:48:38,360 --> 00:48:41,040
Speaker 1: But of course Eddington was wrong about that, and even

900
00:48:41,120 --> 00:48:44,440
Speaker 1: Schwartzfield himself didn't think you would find these mathematical objects

901
00:48:44,480 --> 00:48:46,880
Speaker 1: in nature. He thought that sort of the outward pressure

902
00:48:46,920 --> 00:48:49,640
Speaker 1: of stars would prevent them from collapsing down to a

903
00:48:50,120 --> 00:48:54,120
Speaker 1: volume smaller than that sphere catastrophe. And remember he was

904
00:48:54,200 --> 00:48:57,160
Speaker 1: not setting out to posit the existence of black holes.

905
00:48:57,239 --> 00:49:00,279
Speaker 1: That wasn't his goal. That they just simply pop up

906
00:49:00,400 --> 00:49:04,040
Speaker 1: as this weird byproduct of him using general relativity to

907
00:49:04,160 --> 00:49:07,760
Speaker 1: calculate the gravitational fields generated by different kinds of massive

908
00:49:07,800 --> 00:49:11,480
Speaker 1: bodies in space. Now we have to stress here that

909
00:49:11,640 --> 00:49:14,439
Speaker 1: sword Shield didn't call it a black hole. He called

910
00:49:14,440 --> 00:49:17,719
Speaker 1: it a discontinuity. Yeah, what did Eddington call it? Oh?

911
00:49:17,800 --> 00:49:20,839
Speaker 1: He called it a magic circle. Oh that's really good.

912
00:49:21,360 --> 00:49:23,759
Speaker 1: I kind of wish we'd stuck with that. Yeah, though

913
00:49:23,800 --> 00:49:26,160
Speaker 1: that of course has its own baggage. You expect like

914
00:49:26,320 --> 00:49:28,759
Speaker 1: elves to come flying out of it, right. Uh No,

915
00:49:28,920 --> 00:49:32,600
Speaker 1: But the term black hole was coined later still by

916
00:49:32,760 --> 00:49:37,240
Speaker 1: American theoretical physicist John Archibald Wheeler, who lived nineteen eleven

917
00:49:37,280 --> 00:49:39,600
Speaker 1: through two thousand and eight. Did he coin it or

918
00:49:39,719 --> 00:49:42,080
Speaker 1: was he just the first one to start using it? Well?

919
00:49:42,560 --> 00:49:45,120
Speaker 1: He has. So the story that I read is that

920
00:49:45,320 --> 00:49:47,200
Speaker 1: he was in a conference in New York City in

921
00:49:47,280 --> 00:49:51,000
Speaker 1: nineteen sixty seven and he apparently seized on a suggestion

922
00:49:51,320 --> 00:49:54,520
Speaker 1: shouted from the audience. I'm a I'm as I could.

923
00:49:54,560 --> 00:49:57,120
Speaker 1: I couldn't find out what the exact shout was, but

924
00:49:57,160 --> 00:49:59,839
Speaker 1: I'm assuming it was something like call it a black hole, John,

925
00:50:00,120 --> 00:50:02,920
Speaker 1: or that's a black hole, something of that effect, or

926
00:50:03,000 --> 00:50:05,600
Speaker 1: just maybe a chant black hole black hole. So he

927
00:50:05,719 --> 00:50:07,680
Speaker 1: was like trying to work the audience. He's like, throw

928
00:50:07,719 --> 00:50:09,600
Speaker 1: out some names, come on, give me some ideas, and

929
00:50:09,680 --> 00:50:13,080
Speaker 1: people are like magic circle and he's like, nah, no,

930
00:50:13,239 --> 00:50:16,200
Speaker 1: no magic circles here. Yeah, it's like improv alright, somebody

931
00:50:16,280 --> 00:50:19,239
Speaker 1: give me a theme and we'll we'll construct some sort

932
00:50:19,280 --> 00:50:23,640
Speaker 1: of theoretical physics structure out of it. How about dark Star?

933
00:50:25,520 --> 00:50:31,200
Speaker 1: So in his autobiography Sphere Catastrophe, I would like to

934
00:50:31,200 --> 00:50:34,400
Speaker 1: see an improv sketch around the sphere catastrophe. Uh So.

935
00:50:34,800 --> 00:50:38,640
Speaker 1: In his autobiography, Wheeler wrote that the black hole quote

936
00:50:38,840 --> 00:50:41,919
Speaker 1: teaches us that space can be crumpled like a piece

937
00:50:41,960 --> 00:50:45,719
Speaker 1: of paper into an infanticible dot, that time can be

938
00:50:45,840 --> 00:50:48,800
Speaker 1: extinguished like a blown out flame, and that the laws

939
00:50:48,840 --> 00:50:52,800
Speaker 1: of physics that we regard as sacred, as immutable or anything,

940
00:50:52,920 --> 00:50:55,439
Speaker 1: but which I think sums it up rather nicely. Yeah,

941
00:50:56,000 --> 00:50:59,520
Speaker 1: I like that. Well, I mean it also Wheeler, there

942
00:50:59,600 --> 00:51:03,160
Speaker 1: he speaking, Einstein is ms right, Like the whole idea

943
00:51:03,200 --> 00:51:05,640
Speaker 1: of general relativity is that we used to think, oh,

944
00:51:05,719 --> 00:51:08,160
Speaker 1: space and time, those are the things that are constant

945
00:51:08,200 --> 00:51:10,960
Speaker 1: and immutable, and other stuff can can get moved around,

946
00:51:11,080 --> 00:51:13,759
Speaker 1: and we found out through relativity. No, well, the speed

947
00:51:13,800 --> 00:51:15,879
Speaker 1: of light and a vacuum might be constant, but space

948
00:51:15,960 --> 00:51:18,000
Speaker 1: and time you mess all. You mess with them a

949
00:51:18,120 --> 00:51:23,239
Speaker 1: lot and Wheeler Wheeler is carrying that torch. So maybe

950
00:51:23,320 --> 00:51:25,280
Speaker 1: that's going to be where we have to wrap up today.

951
00:51:25,480 --> 00:51:28,280
Speaker 1: But the big question left lingering for us to explore

952
00:51:28,360 --> 00:51:31,640
Speaker 1: next time is how did this mathematical curiosity this sort

953
00:51:31,680 --> 00:51:34,440
Speaker 1: of like weird artifact of people trying to solve problems

954
00:51:34,520 --> 00:51:38,719
Speaker 1: on paper become a feature that scientists actually think exists

955
00:51:38,880 --> 00:51:42,080
Speaker 1: out in the physical world, and how do we detect

956
00:51:42,200 --> 00:51:44,919
Speaker 1: them if they do exist? You will find out next time.

957
00:51:45,480 --> 00:51:48,120
Speaker 1: In the meantime, however, be sure to head on over

958
00:51:48,239 --> 00:51:50,120
Speaker 1: to stuff to Blow your Mind dot com. That is

959
00:51:50,160 --> 00:51:52,759
Speaker 1: the mothership. That is where you will find all the

960
00:51:52,880 --> 00:51:55,200
Speaker 1: episodes of the podcast. You'll find links out to our

961
00:51:55,280 --> 00:51:57,680
Speaker 1: various social media accounts as well, and hey, I want

962
00:51:57,680 --> 00:52:00,439
Speaker 1: to remind everyone if you want to support our show,

963
00:52:01,000 --> 00:52:03,040
Speaker 1: a great way to do it is to rate and

964
00:52:03,239 --> 00:52:07,000
Speaker 1: review wherever you get your podcast. Big thanks as always

965
00:52:07,040 --> 00:52:10,320
Speaker 1: to our excellent audio producers Alex Williams and Tory Harrison.

966
00:52:10,480 --> 00:52:12,280
Speaker 1: If you want to get in touch with us directly

967
00:52:12,360 --> 00:52:14,640
Speaker 1: to let us know feedback on this episode or any other,

968
00:52:15,000 --> 00:52:17,440
Speaker 1: suggest a topic for the future, or just to say hi,

969
00:52:17,600 --> 00:52:19,720
Speaker 1: let us know where you listen from, you can email

970
00:52:19,840 --> 00:52:22,480
Speaker 1: us at blow the Mind at how stuff works dot

971
00:52:22,560 --> 00:52:33,600
Speaker 1: com for more on this and thousands of other topics.

972
00:52:33,760 --> 00:52:35,239
Speaker 1: Does it how stuff works dot com