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Speaker 1: Hey, Danie, what do you think makes black holes so interesting?

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Speaker 2: You know, I think the mystery, the finality of it,

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Speaker 2: the weirdness of it.

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Speaker 1: For sure, they're like a magnet for fascination.

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Speaker 2: They absolutely are for curiosity, for investigation, for dedication.

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Speaker 1: And it's not just physicists. Everyone seems to have questions

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Speaker 1: about black holes.

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Speaker 2: Yeah, they seem to be sort of mentally magnetic.

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Speaker 1: So black holes attract matter and also questions.

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Speaker 2: They definitely attract questions. They seem to repel understanding.

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Speaker 1: Or they just repel physicists.

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Speaker 2: I'm pretty sure they'd be happy to suck me right in.

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Speaker 1: I don't think I want to go down that rabbit hole.

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Speaker 1: Hi am Hora May Cartoons, an author of Oliver's Great

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Speaker 1: Big Universe.

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

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Speaker 2: at UC Irvine, and I desperately want to know what's

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Speaker 2: inside those black.

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Speaker 1: Holes, if there is even an inside. Right do we

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Speaker 1: know that they have an inside?

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Speaker 2: We don't really know anything beyond the event horizon at all.

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Speaker 2: In some sense, the interior of a black hole could

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Speaker 2: be like another universe.

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Speaker 1: Whoa like We could be living inside of a black

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Speaker 1: hole right now, is that possible.

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Speaker 2: I think that gives me a mental black hole even

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Speaker 2: thinking about it.

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Speaker 1: I suckered you write in. But anyways, welcome to our

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Speaker 1: podcast Daniel and Jorge Explain the Universe, a production of iHeartRadio.

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Speaker 2: In which we try our best not to give you

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Speaker 2: a headache while we contemplate the deepest secrets of the universe.

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Speaker 2: Want to understand everything that's out there, from the tiniest

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Speaker 2: little bits to the hugest swirling black holes and everything

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Speaker 2: in between, because we think that it's possible somehow to

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Speaker 2: make sense of it all, to understand it, to predict it,

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Speaker 2: and to explain all of it to you.

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Speaker 1: Yeah, that's right. We try to be the advil or

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Speaker 1: tile and all to your understanding of the universe, not

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Speaker 1: give you a headache about how amazing things are, but

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Speaker 1: rather try to ease the pain of trying to wrap

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Speaker 1: your mind around this amazing costmoves we live in. I

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Speaker 1: think it was as your prescription for physics.

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Speaker 2: Well, everybody out there is going to need like another

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Speaker 2: kind of health insurance now physics health insurance.

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Speaker 1: The physicists have special health insurance for you know, headaches

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Speaker 1: and mind bending.

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Speaker 2: We're going to help you cover the cost of understanding

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Speaker 2: the universe, because while physics has made lots of progress

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Speaker 2: in understanding the way the universe works, there are still

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Speaker 2: huge gaps in our knowledge. In fact, we're pretty sure

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Speaker 2: there's more that we own understand than that we do,

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Speaker 2: and a lot of those mysteries might have answers waiting

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Speaker 2: for us beyond the curtain of the event horizon.

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Speaker 1: Yeah, as we've talked about, we only know about five

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Speaker 1: percent of the whole universe. The rest, the other ninety

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Speaker 1: five percent is a complete mystery. And even within the

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Speaker 1: five percent there we think we know, there are still

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Speaker 1: huge holes in our understanding of how things work and

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Speaker 1: what can happen out there in the universe.

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Speaker 2: The best way to unravel some of the open mysteries

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Speaker 2: is to embrace the unknown, is to dive into our

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Speaker 2: ignorance and try to reveal something new about the universe.

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Speaker 2: Often this happens at the extreme points of the universe,

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Speaker 2: places where things are super duper hot, are super duper dense,

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Speaker 2: or super duper crazy, because it's that those places that

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Speaker 2: our understanding breaks down. That's one reason why black holes

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Speaker 2: are so attractive to physicists, because they are where our

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Speaker 2: current theories have to break.

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Speaker 1: Yeah, it seems like there's no place in the universe

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Speaker 1: that is more extreme or mysterious and a black hole.

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Speaker 1: We have so many questions about that. Everyone has questions

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Speaker 1: about it. It seems that it attracts not just mass

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Speaker 1: and energy, but also curiosity.

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Speaker 2: It does absolutely. I don't know if it sucks in curiosity,

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Speaker 2: or it's radiating curiosity, or how the whole curiosity field works.

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Speaker 1: Talking talking radiation of curiosity exactly.

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Speaker 2: Maybe it's consuming anti curiosity while radiating curiosity.

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Speaker 1: He knows anti curiosity. Oh, that's an interesting concept, But

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Speaker 1: what is that?

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Speaker 2: I don't know. That's what we're trying to generate on

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Speaker 2: this podcast. We're trying to satisfy everybody's curiosity or are

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Speaker 2: we just trying to stoke it. I'm not even sure anymore.

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Speaker 1: It sounds like you're trying to annihilate people curiosity.

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Speaker 2: No, I guess we're trying to generate anti confusion particles.

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Speaker 2: How about that?

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Speaker 1: Oh, there you go, rock Ons, get it. Tino's exactly

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Speaker 1: the AHA particles. That's what we're after.

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Speaker 2: Yeah, I want to be one with the AHA field.

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Speaker 2: But there are still very basic questions about how black

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Speaker 2: holes work, what it means to be near a black hole,

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Speaker 2: what you would experience, what you might measure with your

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Speaker 2: devices near a black hole. We've talked about the massive

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Speaker 2: black holes, we talked about the charge of black holes,

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Speaker 2: we talked about the spin of black holes. But there

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Speaker 2: are still even more basic things we can think about

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Speaker 2: when it comes to black holes.

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

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Speaker 1: do black holes have magnetic fields?

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Speaker 2: Like?

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Speaker 1: Are they attractive or repulsive? Do they have raised or not?

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Speaker 2: Can you use black holes to find lost wedding rings

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Speaker 2: on the beach? I knew there was a practical application

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Speaker 2: of my research somewhere.

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Speaker 1: Could you use it to detect your wedding ring on

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Speaker 1: the beach when in it just swallow up the whole beach?

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Speaker 2: Then you'd have a good excuse for why you lost

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Speaker 2: your wedding ring. Look, there was a black hole on

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Speaker 2: the beach.

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Speaker 1: Yeah, and you would technically know where it is. It's

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Speaker 1: inside the black hole. You just you know you can't

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Speaker 1: get it.

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Speaker 2: Ever, Yeah, exactly. No number of explainingons is going to

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Speaker 2: get you out of that jam.

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Speaker 1: Yeah, But yeah, it's an interesting question. Do black holes

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Speaker 1: have magnetic field? And I know, we've did a whole

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Speaker 1: episode on whether black holes have a charge, right, Yeah,

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Speaker 1: and so this is different. This is more about the

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Speaker 1: magnetic field.

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Speaker 2: Yeah, we did one on charge, we did another one

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Speaker 2: on spin. There's not that much stuff you can actually

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Speaker 2: know about black holes, and we know so little, so

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Speaker 2: I'm always excited to talk more about it.

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Speaker 1: Then we do a whole episode on the hairiness of

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Speaker 1: a black hole.

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Speaker 2: That's true, their lack of hairiness actually their smooth shavenness.

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Speaker 1: Yeah. Well, this is an interesting question, and so as usual,

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Speaker 1: we were wondering how many people out there had thought

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Speaker 1: about whether black holes have magnetic fields, and if they do,

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Speaker 1: what do they look like or feel like.

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Speaker 3: I think it's possible that they do, I think if

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Speaker 3: I'm not too sure exactly after rationalets, but somehow I

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Speaker 3: feel like it might be possible for black holes to

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Speaker 3: have mynetic fields.

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Speaker 4: I think they do, if only from the spiraling matter

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Speaker 4: that's been consumed by the black hole. Whether or not

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Speaker 4: they are magnetic in their core, whatever their core is,

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Speaker 4: if you can have a call in a black hole,

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Speaker 4: I don't know, but by virtue of the whole of

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Speaker 4: the object that's whorly yes.

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Speaker 5: I do not believe so only because I do not

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Speaker 5: believe there are any charged particles within a black hole. However,

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Speaker 5: since we do see jets coming from black holes at times,

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Speaker 5: that could be totally wrong about that.

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Speaker 1: I don't really know, but if I had to guess,

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Speaker 1: I think they would like.

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Speaker 2: Something to do with the hawking radiation being magnetized somehow, or.

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Speaker 6: So the black hole itself beyond the event horizon. I

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Speaker 6: don't think we can know that, but the area around

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Speaker 6: the black hole where the Acresian disk is probably can

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Speaker 6: have a magnetic field.

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Speaker 2: Black Holes have mass, and they have spin, and I

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Speaker 2: believe they have a charge.

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Speaker 6: So if something has a charge, it should also have

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Speaker 6: a magnetic field, probably a little squirrely with the amount.

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Speaker 2: Of gravitational force is going on, but going with yes.

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Speaker 7: Yes, I'm pretty sure black holes have magnetic fields because

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Speaker 7: whenever a particle that's charged enters it, the electric charge

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Speaker 7: is conserved. So I guess a black hole would need

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Speaker 7: to have that magnetic field that the particle had.

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Speaker 1: I have no idea that.

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Speaker 7: As a wild guest, I would say, yes, they have

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Speaker 7: probably vacuumed app some magnetic vibes along the way.

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Speaker 2: Black holes do have magnetic fields.

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Speaker 3: I'm pretty sure that the Beatles wrote a song about it,

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Speaker 3: Magnetic fields forever.

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Speaker 6: If a black hole is churning around, does it create

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Speaker 6: a magnetic field? Is there a north pole to a

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Speaker 6: black hole? I wonder if magnetism can escape gravity or

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Speaker 6: is immune to it.

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Speaker 2: I think magnetize are neutron stars with a magnetic charge.

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Speaker 2: I'm not sure about a black hole. Maybe if it's

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Speaker 2: spinning and has an electric charge.

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Speaker 5: I think that if a black hole a bunch of

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Speaker 5: large stuff with a magnetic field, and the black hole

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Speaker 5: would get a magnetic field.

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Speaker 8: I'm gonna say yes because this one out of three

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Speaker 8: things that that black hole present so that we can measure.

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Speaker 8: But I forget one of them. So there are spin, there, mass,

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Speaker 8: and electromagnetic force. So I'm gonna say yes.

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Speaker 1: All right. Interesting answers from a lot of magnetic people.

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Speaker 2: Yeah, you could tell a lot of people had not

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Speaker 2: thought about this question at all. They seem to sort

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Speaker 2: of come up with their answers on the fly.

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Speaker 1: Yeah, it's kind of a polarizing question.

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Speaker 2: People either retracted or repelled by it.

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Speaker 1: Yeah, Well, it seemed to attract definitely a lot of

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Speaker 1: ideas about what's going on in the black hole, and

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Speaker 1: so let's dive right into it. Daniel take us through

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Speaker 1: the basics of black holes and how they relate to electromagnetism.

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Speaker 2: So fundamentally, we don't really know what black holes are

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Speaker 2: in our actual universe, like the physical things that are

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Speaker 2: at the center of the galaxy, or they have really

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Speaker 2: dense stuff orbiting them really closely. We're not really sure

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Speaker 2: what those things are, but we do have a concept

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Speaker 2: in our theory general relativity dicks a kind of black

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Speaker 2: hole that we know. Again, general relativity can't be right,

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Speaker 2: so this theoretical object can't actually align with what's out

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Speaker 2: there in the universe, but it gives us something to

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Speaker 2: dig into, something that play with. And because general relativity

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Speaker 2: tells us that gravity is not a force between objects

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Speaker 2: the way Newton described it, but instead a curvature of

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Speaker 2: space time, there's something weird that can happen when you

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Speaker 2: get enough mass, enough energy density actually together in one place,

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Speaker 2: which is that space can curve so much that the

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Speaker 2: inside is essentially cut off from the outside. There's a

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Speaker 2: place beyond which space is curved so that it only

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Speaker 2: points towards the center of the black hole, meaning any

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Speaker 2: object that falls past, that event horizon will always end

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Speaker 2: up at the center of the black hole. And so

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Speaker 2: this is the basic concept of a black hole, sort

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Speaker 2: of extreme space time curvature that generates this event horizon

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Speaker 2: past which nothing can escape.

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Speaker 1: Right, right, because I feel like that's always one of

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Speaker 1: the carriats we have to point out is that the

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Speaker 1: bending of space time, right, it's not just sort of space,

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Speaker 1: it's also sort of like what happens in the future.

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Speaker 2: There are definitely time related effects. Also, mass bends space

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Speaker 2: and creates this event horizon, it also bends time. So

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Speaker 2: you are near a black hole, for example, a distant observer,

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Speaker 2: we'll see your clock go more slowly, and near black holes,

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Speaker 2: space and time are very confusing, and in fact, the

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Speaker 2: whole concept of space time is easier to understand in

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Speaker 2: special relativity when you have flat space. In general relativity,

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Speaker 2: which direction is space and which direction is time becomes

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Speaker 2: very very confusing, and in some cases it's not even clear.

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Speaker 1: And so, as you said, it's something that physics predicts

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Speaker 1: is happening out there in the universe because we see

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Speaker 1: around us and it seems like, you know, the Sun

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Speaker 1: is bending space around it, the Earth is bending space

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Speaker 1: around and we're bending space around us. But if you

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Speaker 1: take it to an extreme, it predicts something called a

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Speaker 1: black hole.

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Speaker 2: Yeah, and a lot of people imagine a black hole

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Speaker 2: in a sort of Newtonian way. They think, oh, gravity

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Speaker 2: is so strong that you have to go faster than

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Speaker 2: the speed of light in order to escape it. But

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Speaker 2: it's not a question of forces, it's not a question

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Speaker 2: of a velocity. It's not a Newtonian picture at all.

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Speaker 2: It really tells you that the story of how gravity

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Speaker 2: works is very, very different. That you're literally trapped inside

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Speaker 2: this event horizon. No amount of velocity, no force can

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Speaker 2: ever escape it because the shape of space itself has changed.

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Speaker 2: And so if you imagine space is this like emptiness

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Speaker 2: in which things float, then you need a new idea.

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Speaker 2: General relativity tells us we could describe it as this

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Speaker 2: sort of stuff with curvature to it, that we're moving

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Speaker 2: through that curvature, and that curvature is not sitting inside

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Speaker 2: some like deeper, larger space that you might be tempted

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Speaker 2: to imagine. That's all there is, and we are trapped

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Speaker 2: inside of it, and there's nothing on the outside of

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Speaker 2: it as far as we.

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Speaker 1: Know, right, right, and as usual we also have to

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Speaker 1: give the cavit that black holds are technically theoretical, right, Like,

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Speaker 1: we've seen things that sort of behave like black hold

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Speaker 1: but we haven't sort of been in front of one

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Speaker 1: or touched it, right.

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Speaker 2: That's right. And what we're describing is a prediction of

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Speaker 2: general relativity, which we know to be very accurate in

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Speaker 2: most circumstances, except we expect it to break down when

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Speaker 2: things get very very intense and very very small. And so,

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Speaker 2: for example, general relativity predicts that at the heart of

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Speaker 2: one of these black holes is a singularity, a point

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Speaker 2: of infinite density. This runaway gravity just goes on forever

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Speaker 2: and you get infinite curvature at the heart of the

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Speaker 2: black hole. But we don't think that that's really happening

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Speaker 2: because we know that that's in conflict with quantum mechanics.

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Speaker 2: And so real black holes, if they exist out there

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Speaker 2: in the universe, can't align perfectly with this theoretical description

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Speaker 2: of a general relativity black hole. There has to be

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Speaker 2: some quantum fuzziness to it, some other version of a

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Speaker 2: black hole. And we talked recently on the podcast how

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Speaker 2: quantum black holes probably radiate. They're not perfectly black due

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Speaker 2: to Hawking radiation, and there must be other changes we

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Speaker 2: need to make from this general relativity picture of a

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Speaker 2: black hole to a realistic quantum gravity black hole that

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Speaker 2: we don't even know how to describe. And you're right

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Speaker 2: that the things we've seen out there in the universe,

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Speaker 2: at the heart of our galaxy, etc. We're not even

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Speaker 2: sure if they actually are black holes because we've not

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Speaker 2: technically observed an event horizon. All we've seen is that

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Speaker 2: there are very dense objects, very massive, very small, very compact,

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Speaker 2: and so we suspect that they are black holes, but

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Speaker 2: they could be something else. These days, there are quantum

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Speaker 2: gravity inspired ideas for other things that could fit the data.

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Speaker 2: Fuzzballs or dark stars, etc. Yeah, all kinds of fun names.

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Speaker 1: I wonder if we should maybe start calling black holes

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Speaker 1: and not black holes then maybe.

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Speaker 2: Or maybe just black holes with a question mark black

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Speaker 2: holes really dark objects rdos.

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Speaker 1: All right, So then a big concept in a black

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Speaker 1: hole is this idea of an event horizon. Now is

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Speaker 1: the idea of an event horizon also dependent on relativity

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Speaker 1: and quantum mechanics playing nicely with each other, or does

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Speaker 1: relativity only break down at the center of a black hole? Like,

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Speaker 1: is the edge of a black holes safe to talk about?

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Speaker 2: The edge of a black hole is really only something

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Speaker 2: we can talk about in general relativity. We don't know

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Speaker 2: how quantum mechanics will modify that. It might make it

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Speaker 2: so that there are no event horizons. These buzzballs, for example,

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Speaker 2: compact states of strings do not have event horizons at all,

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Speaker 2: So it could be that there are no event horizons

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Speaker 2: in the universe. So if we want to talk about this,

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Speaker 2: really the only thing we can do is talk about

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Speaker 2: what general relativity predicts, even though we're not exactly sure

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Speaker 2: it's real.

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Speaker 1: So then how do you define the event horizon?

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Speaker 2: Then? Well, in general relativity, the event horizon is the

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Speaker 2: point past which no information can escape, and that's something

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Speaker 2: we can calculate in general relativity and depends on the

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Speaker 2: mass of the object, also whether it's spinning, whether it

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Speaker 2: has charged these kinds of things.

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Speaker 1: And it's kind of a very special point in a

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Speaker 1: black hole because that's the point at which not even information.

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Speaker 2: Can escape, right, Yeah, that's right.

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Speaker 1: So the sort of limits of the things we can

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Speaker 1: know about the black hole.

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Speaker 2: Yeah, you can't know anything that's going on inside the

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Speaker 2: black hole, but you can measure some things about the

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Speaker 2: black hole, like we know, for example, obviously you can

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Speaker 2: measure the black hole's mass. You can measure its gravitational

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Speaker 2: effects on things nearby. If you fly near a black hole,

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Speaker 2: you're going to be drawn towards it because space is curved,

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Speaker 2: So the effect of the black hole exists outside the

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Speaker 2: event horizon. You can sort of think of it as

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Speaker 2: the event horizon itself having a property. The event horizon

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Speaker 2: is there, it summarizes all the stuff that's inside of it.

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Speaker 2: The mass of the event horizon or the black hole

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Speaker 2: itself affects space outside the event horizon. So you can

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Speaker 2: definitely know that about the black hole, and you can

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Speaker 2: know a couple of other details as well.

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Speaker 1: Like the spin and also the charge of a black hole.

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Speaker 2: Right, Yeah, that's right. Those are the three things that

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Speaker 2: general relativity says we can know about the black hole.

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Speaker 2: That a black hole can also be spinning, right, Things

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Speaker 2: that fall into a black hole if they have angler

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Speaker 2: momentum to keep having angular momentum, because in our universe,

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Speaker 2: angular momentum is conserved. We're pretty sure same thing with

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Speaker 2: electric charge. The universe strictly preserves electric charge. We've never

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Speaker 2: seen that violated. You can create plus and minus particles together,

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Speaker 2: but the overall charge of the universe has to be

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Speaker 2: the same. And so if you drop an electron into

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Speaker 2: a black hole, then the black hole has to have

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Speaker 2: that charge because it can't just disappear from the universe.

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Speaker 2: So mass, spin, and charge are the things you can

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Speaker 2: know about a black hole from the outside. You can't

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Speaker 2: know like the arrangement of charges or masses or spins

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Speaker 2: or whatever inside the event horizon, but you don't have

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Speaker 2: to in order to know the total mass or the

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Speaker 2: total charge or the total spin from the outside.

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Speaker 1: Can you tell if that black hole has a headache

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Speaker 1: or something?

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Speaker 2: Do black holes wear mood rings? I wish they did?

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Speaker 2: Always black?

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Speaker 1: Does that mean do they wear engagement rings? Well, you

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Speaker 1: said charge, and I'm wondering. You know, that's the electromagnetic charge,

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Speaker 1: but we also talked about it in this podcast. But

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Speaker 1: other kinds of charge in the universe, from the weak

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Speaker 1: fours and the strong force. Can you know those other

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Speaker 1: charges about a black hole? Can you know the color

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Speaker 1: of a black hole?

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Speaker 2: The color charges are really fun and tricky concept. It's

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Speaker 2: not something we really understand very well because objects that

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Speaker 2: have color don't ever exist in the universe. We only

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Speaker 2: see neutral things, like things that have color, like quarks

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Speaker 2: are always bound together into neutral states, something with the

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Speaker 2: opposite color or the other two complementary colors, so they

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Speaker 2: balance out because there's so much energy in the strong force,

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Speaker 2: so things can't have their own color charge. You might

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Speaker 2: want to imagine, like what happens if you have a

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Speaker 2: quark anti quark pair and they're bound together, but one

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Speaker 2: of them falls into the black hole. And now you're

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Speaker 2: doing quantum gravity, because we're talking about bound states of quarks,

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Speaker 2: and one of them falls into the black hole and

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Speaker 2: the other one doesn't. We don't know the answers to

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Speaker 2: those questions because we don't have a theory of quantum gravity.

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Speaker 1: But is it possible then maybe they also conserve those

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Speaker 1: kinds of charges, and you would have to add that

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Speaker 1: to the list of things you can know about a

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Speaker 1: black hole.

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Speaker 2: It is possible, And it's also possible that there are

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Speaker 2: other kinds of charges in the universe we've never even discovered,

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Speaker 2: like dark matter could have all sorts of other forces.

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Speaker 2: There could be like a dark version of electromagnetism with

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Speaker 2: dark photons and dark charges, and black holes could have

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Speaker 2: those dark charges as well.

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Speaker 1: Wait, were you saying black holes could have a hidden

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Speaker 1: charge like a hidden fee?

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Speaker 2: Exactly? Check your statements, people.

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Speaker 1: When you buy a black hole, read the small print

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Speaker 1: before you go into a black hole. All right, So

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Speaker 1: then that's you know, we can tell it it has

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Speaker 1: a gravitational field and an electric field. And now let's

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Speaker 1: talk about a magnetic field of a black hole. What

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Speaker 1: exactly is a magnetic field?

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Speaker 2: Magnetic fields are really weird and awesome because they have

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Speaker 2: lots of really interesting symmetries, symmetries that exist and also

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Speaker 2: symmetries that are broken. Like in a lot of ways,

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Speaker 2: the magnetic field is a perfect sister to the electric field,

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Speaker 2: like light, for example, is a between electric fields and

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Speaker 2: magnetic field. It's slashing perfectly back and forth between electric

401
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Speaker 2: fields and magnetic fields and back. It really tells us

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Speaker 2: that the distinction we make between electric fields and magnetic

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Speaker 2: fields is a little bit arbitrary. It's just sort of

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Speaker 2: like a historical thing. We drew a dotted line between

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Speaker 2: these two things that are really part of a larger hole.

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Speaker 2: But there also are important differences between electric fields and

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Speaker 2: magnetic fields. For example, we have electric charges in the universe,

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Speaker 2: but we don't have magnetic charges. Like an electron has

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Speaker 2: a negative charge. You can just create a charged object

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Speaker 2: by putting an electron on it, right, you can't do

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Speaker 2: that with a magnetic field. There's nothing with a magnetic charge.

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Speaker 2: If it existed, this would be called a magnetic monopole.

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Speaker 2: It'd be like something with just a north or something

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Speaker 2: with just a south. We've never seen one in the universe.

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Speaker 2: Physicists don't know why. They think maybe they do exist

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Speaker 2: out there, or used to exist in the early universe.

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Speaker 2: But you can't make a magnetic field the same way

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Speaker 2: you make an electric field by just adding a magnetic

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Speaker 2: charge to something.

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Speaker 1: Well, maybe take a step back here, because you know,

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Speaker 1: like I'm wondering, how do you even define what a

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Speaker 1: magnetic field is. You know, like a gravitational field tells

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Speaker 1: me how much a planet, for example, is pulling on

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Speaker 1: me at any point in space, or an electric field

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Speaker 1: tells me how much you know, an electron is repelling

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Speaker 1: or pushing me or attracting me at any point in space.

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Speaker 1: What does a magnetic field tell you?

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Speaker 2: Yeah, great question. If they were magnetic monopoles, then they

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Speaker 2: would be affected by magnetic fields. The same way that

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Speaker 2: electrical charges are affected by electric fields. They would be

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Speaker 2: accelerated in one way or another. But those don't exist,

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Speaker 2: so we can't use that to define magnetic fields.

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Speaker 1: What do you mean, like when you talk about monopole,

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Speaker 1: you mean like like an a maact that you have

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Speaker 1: a north in the south.

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Speaker 2: Right in the magnets that we have in our universe,

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Speaker 2: we have a north in the south. Those are dipole

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Speaker 2: magnets that create a dipole magnetic field. There's a pair

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Speaker 2: of a North in the south.

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Speaker 1: So are you saying, like, if you had a North

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00:21:56,560 --> 00:21:58,359
Speaker 1: in front of me and I'm the south, it would

442
00:21:58,359 --> 00:22:00,879
Speaker 1: tell me how much I'm attracted to the north repel?

443
00:22:01,000 --> 00:22:02,720
Speaker 2: Yeah, exactly. If you have a huge magnet makes a

444
00:22:02,720 --> 00:22:05,360
Speaker 2: magnetic field, and then if you put a North in

445
00:22:05,400 --> 00:22:08,159
Speaker 2: that field, it would get pushed or pulled in one direction,

446
00:22:08,440 --> 00:22:10,359
Speaker 2: and by the strength of that push or pull, you

447
00:22:10,359 --> 00:22:12,000
Speaker 2: could measure the magnetic field.

448
00:22:12,200 --> 00:22:14,919
Speaker 1: So there is some sort of charge, Yeah, exactly, Like

449
00:22:14,960 --> 00:22:17,359
Speaker 1: what would determine how much of that push and pool?

450
00:22:17,359 --> 00:22:17,760
Speaker 1: I feel?

451
00:22:17,880 --> 00:22:21,040
Speaker 2: Well, the north and south are like the plus and minus. Right,

452
00:22:21,080 --> 00:22:23,080
Speaker 2: North and south for a magnetic field are plus and

453
00:22:23,160 --> 00:22:24,600
Speaker 2: minus for electric charges.

454
00:22:24,840 --> 00:22:26,560
Speaker 1: And I can have like more of it or less fit.

455
00:22:26,680 --> 00:22:30,280
Speaker 2: Yeah, exactly, you've got to bigger magnets or smaller magnets.

456
00:22:30,520 --> 00:22:33,160
Speaker 2: You've got to more norths and more souths. We've never

457
00:22:33,200 --> 00:22:35,280
Speaker 2: seen a north on its own or a south on

458
00:22:35,320 --> 00:22:37,840
Speaker 2: its own the way we have for electric charges. But

459
00:22:37,960 --> 00:22:40,560
Speaker 2: in principle they could exist. Nothing in physics says that

460
00:22:40,640 --> 00:22:43,959
Speaker 2: they can't. But we've only ever seen them paired together.

461
00:22:44,200 --> 00:22:46,240
Speaker 1: I mean, like, if something has a north, it also

462
00:22:46,280 --> 00:22:46,919
Speaker 1: has a south.

463
00:22:47,160 --> 00:22:50,159
Speaker 2: Yeah, and that's because those magnetic fields are actually made

464
00:22:50,640 --> 00:22:54,240
Speaker 2: by electric charges. See, there's a very close connection between

465
00:22:54,280 --> 00:22:57,560
Speaker 2: electricity and magnetism because if you take an electric charge,

466
00:22:57,720 --> 00:23:00,560
Speaker 2: like an electron, and you wiz it around them, it

467
00:23:00,600 --> 00:23:04,040
Speaker 2: makes a magnetic field. Any charge in motion, any charge

468
00:23:04,040 --> 00:23:07,280
Speaker 2: with velocity, is going to make a magnetic field. And

469
00:23:07,359 --> 00:23:10,480
Speaker 2: so every magnetic field that we ever created is actually

470
00:23:10,480 --> 00:23:12,880
Speaker 2: made by moving electric charges.

471
00:23:13,440 --> 00:23:15,800
Speaker 1: So if it's made by electric charges, it's made by

472
00:23:15,800 --> 00:23:18,040
Speaker 1: the electric field. So why do we even call it

473
00:23:18,040 --> 00:23:18,720
Speaker 1: its own field.

474
00:23:18,840 --> 00:23:21,320
Speaker 2: Well, because it's made by electric charges doesn't mean it's

475
00:23:21,320 --> 00:23:24,840
Speaker 2: an electric field, right, Yeah, we could just call this electromagnetism.

476
00:23:24,920 --> 00:23:27,080
Speaker 2: You might be saying, Hey, the distinction between these two things.

477
00:23:27,119 --> 00:23:30,920
Speaker 2: Seems arbitrary. Yes, it's totally arbitrary and historical. Because we

478
00:23:31,000 --> 00:23:33,640
Speaker 2: discovered magnets and we discovered lightning. We call them two

479
00:23:33,640 --> 00:23:36,040
Speaker 2: separate things. We build two theories, and then boom, one

480
00:23:36,119 --> 00:23:39,080
Speaker 2: day a brilliant Scottish dude realized they are actually two

481
00:23:39,119 --> 00:23:42,040
Speaker 2: parts of the same thing. Now we call them electromagnetism.

482
00:23:42,080 --> 00:23:45,280
Speaker 2: And you might say, let's just call it all electromagnetic fields. Cool,

483
00:23:45,400 --> 00:23:47,280
Speaker 2: we can do that, but we do notice that there

484
00:23:47,320 --> 00:23:50,240
Speaker 2: are two different charges that are described by this field,

485
00:23:50,280 --> 00:23:53,600
Speaker 2: electric charges and magnetic charges, and only one seems to

486
00:23:53,640 --> 00:23:54,720
Speaker 2: exist in the universe.

487
00:23:55,240 --> 00:24:00,960
Speaker 1: M all right, So it's deeply connected to electricity, and

488
00:24:01,680 --> 00:24:04,399
Speaker 1: if some things just seem to have it or not, right,

489
00:24:04,520 --> 00:24:06,439
Speaker 1: things would charge seem to have it or not.

490
00:24:06,760 --> 00:24:09,640
Speaker 2: Yeah. So every magnet we've ever seen in the universe

491
00:24:09,760 --> 00:24:13,200
Speaker 2: is either a tiny little object that has quantum spin,

492
00:24:13,480 --> 00:24:16,359
Speaker 2: like an electron has quantum spin, and that spin combined

493
00:24:16,400 --> 00:24:19,399
Speaker 2: with its charge, makes it a tiny little magnet. But

494
00:24:19,520 --> 00:24:21,720
Speaker 2: because it's spinning, it makes two magnets. It makes a

495
00:24:21,760 --> 00:24:24,320
Speaker 2: north and a south, so it's a little dipole magnet.

496
00:24:25,080 --> 00:24:27,600
Speaker 2: Or you can have current like motion of electrons through

497
00:24:27,640 --> 00:24:31,280
Speaker 2: a wire that makes a dipole magnet. So every magnetic

498
00:24:31,359 --> 00:24:34,120
Speaker 2: field we've ever seen is made either by tiny little

499
00:24:34,160 --> 00:24:37,720
Speaker 2: quantum particles having their own little magnetic fields. That's, for example,

500
00:24:37,880 --> 00:24:40,439
Speaker 2: why your refrigerator magnet has a magnetic field. Has all

501
00:24:40,440 --> 00:24:43,400
Speaker 2: these little particles with quantum spin oriented in the same

502
00:24:43,440 --> 00:24:47,000
Speaker 2: way adding up, or like an electromagnet, like an electric

503
00:24:47,080 --> 00:24:49,760
Speaker 2: motor that comes because of current from electricity.

504
00:24:51,359 --> 00:24:53,879
Speaker 1: Interesting, and so I guess now the question is, since

505
00:24:53,920 --> 00:24:57,800
Speaker 1: black holes can have an electric charge and also spin,

506
00:24:58,400 --> 00:25:02,080
Speaker 1: can they also have a magnetic field. So let's dig

507
00:25:02,119 --> 00:25:17,520
Speaker 1: into that. But first let's take a quick break. All right,

508
00:25:17,560 --> 00:25:20,560
Speaker 1: we're asking the question can a black hole have a

509
00:25:20,720 --> 00:25:23,720
Speaker 1: magnetic field? And what would happen if you put it

510
00:25:23,760 --> 00:25:25,200
Speaker 1: on your fridge?

511
00:25:26,560 --> 00:25:28,760
Speaker 2: You would eat everything in your fridge.

512
00:25:29,880 --> 00:25:32,840
Speaker 1: There you go. You can blame that also on a

513
00:25:32,840 --> 00:25:33,440
Speaker 1: black hole.

514
00:25:33,880 --> 00:25:36,080
Speaker 2: I don't know who finished the pie, honey, really, I don't.

515
00:25:36,119 --> 00:25:37,480
Speaker 2: Maybe it was a black hole in the middle of

516
00:25:37,480 --> 00:25:38,720
Speaker 2: the night. Check the camera.

517
00:25:39,880 --> 00:25:41,639
Speaker 1: Yeah me, Rich, I'll put a black hole in the

518
00:25:41,640 --> 00:25:42,480
Speaker 1: fridge there.

519
00:25:43,760 --> 00:25:46,840
Speaker 2: The new black hole diet by Daniel Yeah.

520
00:25:46,880 --> 00:25:48,480
Speaker 1: I don't think that sounds it's work.

521
00:25:49,680 --> 00:25:51,040
Speaker 2: I might need to work shop that a bit.

522
00:25:51,119 --> 00:25:54,280
Speaker 1: Yeah, yeah, yeah, yeah, it's more like an excuse for

523
00:25:54,320 --> 00:25:59,639
Speaker 1: a bad diet. But yeah, so black holes do they have?

524
00:26:00,160 --> 00:26:02,399
Speaker 1: Getting feels like literally, if we have a tiny one,

525
00:26:02,440 --> 00:26:04,879
Speaker 1: would it stick to your fridge? That's kind of what

526
00:26:04,920 --> 00:26:07,400
Speaker 1: we're asking here today, right, right.

527
00:26:07,880 --> 00:26:11,640
Speaker 2: Yeah, it's a really cool question, and the answer is

528
00:26:11,880 --> 00:26:17,480
Speaker 2: it depends why am I not surprised? It depends on

529
00:26:17,520 --> 00:26:21,560
Speaker 2: your reference frame, It depends on your velocity. Because we

530
00:26:21,600 --> 00:26:24,520
Speaker 2: don't have magnetic monopoles. You can't just like throw a

531
00:26:24,560 --> 00:26:27,399
Speaker 2: monopole into a black hole and have it have a

532
00:26:27,440 --> 00:26:31,040
Speaker 2: magnetic field, like inherently. The only way for it to

533
00:26:31,119 --> 00:26:33,480
Speaker 2: have a magnetic field is for it to do what

534
00:26:33,560 --> 00:26:36,800
Speaker 2: electrons do and electric currents do, which is have a

535
00:26:36,960 --> 00:26:40,040
Speaker 2: charge and a spin. So take a black hole, spin

536
00:26:40,119 --> 00:26:42,239
Speaker 2: it and charge it by shooting like a beam of

537
00:26:42,280 --> 00:26:45,439
Speaker 2: electrons right near the event horizon, so it gets some

538
00:26:45,480 --> 00:26:48,600
Speaker 2: angular momentum and it gets some charge. In that case,

539
00:26:48,640 --> 00:26:50,960
Speaker 2: it will get a magnetic field because now it's spinning

540
00:26:51,280 --> 00:26:54,520
Speaker 2: relative to you. So if you have like a magnetometer

541
00:26:54,880 --> 00:26:58,800
Speaker 2: or something, you will measure a magnetic field near the event.

542
00:26:58,600 --> 00:27:00,879
Speaker 1: Horizon, sort of in the same way that like an

543
00:27:00,920 --> 00:27:04,400
Speaker 1: electron on its own can have an electric field because

544
00:27:04,400 --> 00:27:07,040
Speaker 1: it's a charge. It does charge and it has spin.

545
00:27:07,560 --> 00:27:08,760
Speaker 2: Yeah, exactly right.

546
00:27:08,920 --> 00:27:11,000
Speaker 1: Or like if you take a coil of wire and

547
00:27:11,080 --> 00:27:14,040
Speaker 1: you spin a bunch of electrons that is those that's

548
00:27:14,040 --> 00:27:16,520
Speaker 1: a charge spinning which creates a magnetic field.

549
00:27:16,760 --> 00:27:19,359
Speaker 2: Yeah, exactly. You make a coil of wire and you

550
00:27:19,440 --> 00:27:21,760
Speaker 2: run a current through it, that makes the magnetic field

551
00:27:21,800 --> 00:27:24,480
Speaker 2: through the coil, right. Or simply if you just have

552
00:27:24,520 --> 00:27:26,760
Speaker 2: a single line of wire, not a coil, and you

553
00:27:26,880 --> 00:27:29,040
Speaker 2: run electrons through it, then you're going to get a

554
00:27:29,080 --> 00:27:32,840
Speaker 2: magnetic field around the wire. But that magnetic field is

555
00:27:32,960 --> 00:27:37,600
Speaker 2: frame dependent. It depends on the electrons moving relative to

556
00:27:37,640 --> 00:27:41,520
Speaker 2: you through the wire. It only happens because electrons are moving.

557
00:27:41,680 --> 00:27:45,879
Speaker 2: It's charges in motion that give us magnetic fields. So

558
00:27:45,920 --> 00:27:48,480
Speaker 2: if you have your black hole and it's spinning near you,

559
00:27:48,480 --> 00:27:51,040
Speaker 2: you measure magnetic field. Now you get in your ship

560
00:27:51,240 --> 00:27:53,919
Speaker 2: and you start orbiting the black hole at exactly the

561
00:27:53,920 --> 00:27:55,840
Speaker 2: same rate it's spinning, so that when you look out

562
00:27:55,840 --> 00:27:58,520
Speaker 2: of your ship the black hole is not spinning relative

563
00:27:58,560 --> 00:28:01,560
Speaker 2: to you, then it no longer has a magnetic field.

564
00:28:01,680 --> 00:28:04,280
Speaker 2: The magnetic field is frame dependent.

565
00:28:04,480 --> 00:28:08,439
Speaker 1: Well, meaning that the magnetic field disappears or that you

566
00:28:08,520 --> 00:28:11,200
Speaker 1: don't feel it.

567
00:28:11,200 --> 00:28:12,879
Speaker 2: It's not there. I mean, we don't even know if

568
00:28:12,880 --> 00:28:16,480
Speaker 2: fields are real anyway, but you can't measure it, and

569
00:28:16,520 --> 00:28:19,040
Speaker 2: according to the physics, it isn't there. Like you do

570
00:28:19,080 --> 00:28:22,400
Speaker 2: the calculation, there's a prediction of no magnetic field there.

571
00:28:23,080 --> 00:28:25,320
Speaker 2: And the thing is the field itself. You like to think

572
00:28:25,320 --> 00:28:27,760
Speaker 2: of it as something physical. It's out there in the universe.

573
00:28:28,200 --> 00:28:31,240
Speaker 2: But the distinction between electric fields and magnetic fields, like

574
00:28:31,240 --> 00:28:33,879
Speaker 2: you were saying earlier, is a little bit arbitrary, and

575
00:28:33,880 --> 00:28:36,760
Speaker 2: it turns out to depend on your frame of reference.

576
00:28:36,800 --> 00:28:39,400
Speaker 2: And not just for black holes, also for the simple

577
00:28:39,440 --> 00:28:42,640
Speaker 2: situation of electron going down a wire. If you jump

578
00:28:42,680 --> 00:28:44,520
Speaker 2: in a car and you drive down the wire the

579
00:28:44,520 --> 00:28:47,320
Speaker 2: same speed as the electrons, the electrons only have an

580
00:28:47,320 --> 00:28:50,400
Speaker 2: electric field. But your buddy who's standing next to the wire,

581
00:28:50,480 --> 00:28:52,600
Speaker 2: he measures the electrons going through the wire, they have

582
00:28:52,640 --> 00:28:55,880
Speaker 2: a velocity. He will also see a magnetic field. So

583
00:28:55,960 --> 00:28:59,920
Speaker 2: magnetic fields are always frame dependent because they depend on velocity.

584
00:29:00,520 --> 00:29:02,600
Speaker 1: Well that's a little bit odd to me, I guess.

585
00:29:03,280 --> 00:29:06,120
Speaker 1: So let's say have like a loop of wire and

586
00:29:06,160 --> 00:29:08,520
Speaker 1: I run a current through it, and you're saying, if

587
00:29:08,520 --> 00:29:11,400
Speaker 1: I sit in the middle of it, on a like

588
00:29:11,440 --> 00:29:13,360
Speaker 1: an office chair and I spin myself that I'm not

589
00:29:13,400 --> 00:29:15,120
Speaker 1: going to feel the magnetic force.

590
00:29:15,320 --> 00:29:17,720
Speaker 2: Yeah. If you spin at the same rate that those

591
00:29:17,720 --> 00:29:21,360
Speaker 2: electrons are moving, so the electrons have no velocity relative

592
00:29:21,400 --> 00:29:24,280
Speaker 2: to you, then you will feel no magnetic field. You'll

593
00:29:24,320 --> 00:29:26,760
Speaker 2: sense no magnetic field. It's a timely a little bit

594
00:29:26,760 --> 00:29:29,000
Speaker 2: more complicated there because now we're spinning, so we have

595
00:29:29,040 --> 00:29:32,800
Speaker 2: acceleration and non inertial frames, so it's a little bit

596
00:29:32,840 --> 00:29:35,320
Speaker 2: simpler in the straight line case. But yeah, the same

597
00:29:35,360 --> 00:29:36,560
Speaker 2: thing applies, right.

598
00:29:36,720 --> 00:29:38,200
Speaker 1: I guess that's what I was trying to get at,

599
00:29:38,280 --> 00:29:41,080
Speaker 1: is that you're saying it it depends, but it doesn't

600
00:29:41,120 --> 00:29:44,200
Speaker 1: depend on like an inertial frame, which is sort of

601
00:29:44,240 --> 00:29:46,320
Speaker 1: like the standard frames of the universe. It's like you

602
00:29:46,360 --> 00:29:49,360
Speaker 1: have to make up this weird frame, right, like I

603
00:29:49,400 --> 00:29:53,400
Speaker 1: would be feeling other things. I won't feel that electromagnetic field,

604
00:29:53,600 --> 00:29:57,280
Speaker 1: but I'm going to feel, for example, uh, this interpretal force.

605
00:29:57,600 --> 00:30:00,720
Speaker 2: Yeah, exactly. And that's sort of the Missy piece because

606
00:30:00,720 --> 00:30:03,480
Speaker 2: you might be wondering, like, hold on a second. If

607
00:30:03,520 --> 00:30:05,920
Speaker 2: I'm measuring a magnetic field and my friend is not

608
00:30:06,080 --> 00:30:09,120
Speaker 2: measuring a magnetic field, how is that possible? If you

609
00:30:09,200 --> 00:30:11,520
Speaker 2: dropped a monopole into that situation, would it get pushed

610
00:30:11,560 --> 00:30:14,000
Speaker 2: or would it not get pushed? Right, there has to

611
00:30:14,040 --> 00:30:16,920
Speaker 2: be like one answer to that question, and the answer

612
00:30:17,000 --> 00:30:19,320
Speaker 2: is a little bit subtle but kind of beautiful. What

613
00:30:19,400 --> 00:30:22,560
Speaker 2: relativity tells us is that the same laws of physics

614
00:30:22,600 --> 00:30:26,840
Speaker 2: apply no matter what your reference frame, but the story

615
00:30:26,880 --> 00:30:30,040
Speaker 2: they tell about why things happen doesn't have to agree.

616
00:30:30,360 --> 00:30:32,760
Speaker 2: So in one scenario, your friend will say, oh, there's

617
00:30:32,760 --> 00:30:35,720
Speaker 2: a magnetic field there and it helps push things around.

618
00:30:35,840 --> 00:30:38,640
Speaker 2: The other person will say, no, there's no magnetic field there,

619
00:30:38,760 --> 00:30:40,840
Speaker 2: but they will also see the electric field is a

620
00:30:40,840 --> 00:30:43,920
Speaker 2: little bit different and that will compensate. So one person

621
00:30:43,920 --> 00:30:47,240
Speaker 2: will see a combination of electric and magnetic fields doing

622
00:30:47,280 --> 00:30:51,680
Speaker 2: pushes and pulls on charge particles and magnetic monopoles. Somebody

623
00:30:51,680 --> 00:30:54,400
Speaker 2: else will see only electric fields and no magnetic fields,

624
00:30:54,480 --> 00:30:57,920
Speaker 2: but they'll actually predict the same motion for all the particles.

625
00:30:58,040 --> 00:31:00,760
Speaker 2: They'll just have a different reason for why it happened.

626
00:31:01,360 --> 00:31:04,960
Speaker 1: Right. It's sort of like if you're moving with the electricity,

627
00:31:05,000 --> 00:31:09,160
Speaker 1: then you won't feel the forces of the electromagnetic field,

628
00:31:09,200 --> 00:31:13,200
Speaker 1: but you'll have to push and spin yourself around the wire,

629
00:31:13,920 --> 00:31:16,720
Speaker 1: which is sort of equivalent, I think, is what you're saying.

630
00:31:16,920 --> 00:31:19,040
Speaker 2: Yeah, all the differences actually add up to give the

631
00:31:19,080 --> 00:31:21,959
Speaker 2: same prediction, which is kind of amazing. And that's one

632
00:31:21,960 --> 00:31:24,800
Speaker 2: of the beautiful things about relativity is that it shows

633
00:31:24,840 --> 00:31:28,240
Speaker 2: you that all these pieces work together, because really the

634
00:31:28,280 --> 00:31:32,440
Speaker 2: distinction between electricity and magnetism is a bit arbitrary, and

635
00:31:32,480 --> 00:31:35,640
Speaker 2: it's even frame dependent. You know, people going at different

636
00:31:35,680 --> 00:31:38,520
Speaker 2: speeds see electric fields or magnetic fields. But all the

637
00:31:38,520 --> 00:31:42,120
Speaker 2: pieces work together, so that even people in different reference frames,

638
00:31:42,280 --> 00:31:44,480
Speaker 2: while they tell a different story about why things happen,

639
00:31:44,560 --> 00:31:46,959
Speaker 2: like did you have a magnetic field or not, they

640
00:31:46,960 --> 00:31:49,560
Speaker 2: will agree in these scenarios about what actually did happen.

641
00:31:50,160 --> 00:31:52,200
Speaker 1: But I wonder if you can just can you just

642
00:31:52,240 --> 00:31:55,479
Speaker 1: say the same thing about everything in the universe. You know,

643
00:31:55,680 --> 00:31:59,240
Speaker 1: like you could also make gravity disappear if you move

644
00:31:59,320 --> 00:32:02,440
Speaker 1: with the grat, or you can make like a charge

645
00:32:02,520 --> 00:32:04,480
Speaker 1: disappear if you move with the charges.

646
00:32:04,920 --> 00:32:07,720
Speaker 2: Not everything in the universe is frame dependent. For example,

647
00:32:07,800 --> 00:32:10,239
Speaker 2: black holes are not. If there's a black hole, then

648
00:32:10,280 --> 00:32:13,840
Speaker 2: everybody agrees there's a black hole. You can't like boost

649
00:32:13,840 --> 00:32:16,760
Speaker 2: yourself into some frame in which there is no black hole.

650
00:32:17,200 --> 00:32:19,640
Speaker 2: This is why, for example, you can't make a black

651
00:32:19,640 --> 00:32:22,600
Speaker 2: hole just by going really really fast. You might think, oh,

652
00:32:22,640 --> 00:32:24,320
Speaker 2: black holes are actually happen when you have a lot

653
00:32:24,320 --> 00:32:27,239
Speaker 2: of energy, not just mass. So why can't I make

654
00:32:27,280 --> 00:32:29,400
Speaker 2: a black hole by taking a particle and zooming it

655
00:32:29,440 --> 00:32:32,360
Speaker 2: to really high speeds because that would make a frame

656
00:32:32,400 --> 00:32:35,400
Speaker 2: dependent black hole, which doesn't exist in our universe. So

657
00:32:35,480 --> 00:32:38,600
Speaker 2: there are some things that are invariant no matter what

658
00:32:38,640 --> 00:32:41,280
Speaker 2: frame you're in, inertial or not. But yeah, there are

659
00:32:41,280 --> 00:32:43,400
Speaker 2: a lot of things in the universe that are frame dependent,

660
00:32:43,440 --> 00:32:45,880
Speaker 2: I think more than people suspect, right.

661
00:32:46,120 --> 00:32:48,400
Speaker 1: I wonder if the analogy is sort of like, you know,

662
00:32:48,520 --> 00:32:50,280
Speaker 1: if you jump out of an airplane and you're falling

663
00:32:50,280 --> 00:32:53,520
Speaker 1: towards Earth, you can't tell that there's a planet there

664
00:32:53,640 --> 00:32:55,920
Speaker 1: blow you right, Like, to you, it's going to feel

665
00:32:55,920 --> 00:32:58,480
Speaker 1: like you're floating in space as you plummet to your death.

666
00:32:58,680 --> 00:33:02,040
Speaker 2: Yeah, that's right in that scenario. Actually, in freefall, you're

667
00:33:02,040 --> 00:33:05,600
Speaker 2: not doing any accelerating. It's the planet that's accelerating towards you.

668
00:33:05,640 --> 00:33:08,440
Speaker 2: The surface of the planet is accelerating towards you. If

669
00:33:08,440 --> 00:33:12,000
Speaker 2: you take out a gravitometer or an accelerometer in that scenario,

670
00:33:12,120 --> 00:33:15,000
Speaker 2: you'll measure no acceleration, So you need to look out

671
00:33:15,000 --> 00:33:18,320
Speaker 2: the window to see a planet rushing towards you to

672
00:33:18,360 --> 00:33:21,200
Speaker 2: discover that your life span is going to be very short.

673
00:33:21,440 --> 00:33:23,440
Speaker 1: Right, So in that way, sort of gravity is also

674
00:33:23,720 --> 00:33:26,320
Speaker 1: reference dependent, Right, I can make it disappear if I

675
00:33:26,400 --> 00:33:27,440
Speaker 1: jump out of an airplane.

676
00:33:27,640 --> 00:33:30,240
Speaker 2: Lots of gravitational effects are frame dependent. Yes, there are

677
00:33:30,280 --> 00:33:33,200
Speaker 2: some things that are frame independent, like the existence of

678
00:33:33,200 --> 00:33:36,480
Speaker 2: a black hole, but a lot of things are frame dependent, absolutely,

679
00:33:36,760 --> 00:33:39,720
Speaker 2: And you're right that this story applies very broadly. There's

680
00:33:39,800 --> 00:33:43,000
Speaker 2: lots of situations in physics where people will disagree about

681
00:33:43,040 --> 00:33:45,920
Speaker 2: why things happened, even if they apply the same rules,

682
00:33:46,320 --> 00:33:49,040
Speaker 2: and they might agree about what happened, they'll tell a

683
00:33:49,040 --> 00:33:52,240
Speaker 2: different story about how that happened or why that happened,

684
00:33:52,600 --> 00:33:54,200
Speaker 2: even though the outcome is the same.

685
00:33:55,720 --> 00:33:58,280
Speaker 1: But I guess if you stick to what most people

686
00:33:58,360 --> 00:34:01,560
Speaker 1: think is normal, which is like an inertial frame or

687
00:34:02,120 --> 00:34:05,920
Speaker 1: you know, not spin around at a crazy speed in

688
00:34:05,960 --> 00:34:08,840
Speaker 1: an office chair, then you would say that a black

689
00:34:08,840 --> 00:34:10,360
Speaker 1: hole does have a magnetic field.

690
00:34:10,600 --> 00:34:12,879
Speaker 2: Yeah, exactly, and it's not special, right. The black hole

691
00:34:12,920 --> 00:34:15,400
Speaker 2: has a magnetic field, and exactly the same way a

692
00:34:15,440 --> 00:34:18,000
Speaker 2: coil of wire has a magnetic field. You got charge

693
00:34:18,040 --> 00:34:21,200
Speaker 2: in there, You've got spin, so you're moving charges, so

694
00:34:21,239 --> 00:34:23,719
Speaker 2: you get a magnetic field. The magnetic field of a

695
00:34:23,719 --> 00:34:26,880
Speaker 2: black hole is not deficient in any way compared to

696
00:34:27,040 --> 00:34:29,760
Speaker 2: the magnetic field from an electromagnetic motor, for example.

697
00:34:31,120 --> 00:34:32,600
Speaker 1: And I guess what that means is that if I

698
00:34:32,640 --> 00:34:35,520
Speaker 1: take a compass and I hold it up close to

699
00:34:35,760 --> 00:34:37,880
Speaker 1: a black hole, I'm going to see it point in

700
00:34:37,880 --> 00:34:40,160
Speaker 1: a specific direction, right, just like it points to a

701
00:34:40,320 --> 00:34:41,840
Speaker 1: specific direction here on Earth.

702
00:34:42,239 --> 00:34:45,040
Speaker 2: Yeah, exactly, a black hole have a magnetic field the

703
00:34:45,120 --> 00:34:47,160
Speaker 2: way the Earth does. And we think the Earth's magnetic

704
00:34:47,160 --> 00:34:51,720
Speaker 2: field probably comes from convection and flow of stuff inside

705
00:34:51,760 --> 00:34:54,560
Speaker 2: the Earth, though we don't totally understand. And so yeah,

706
00:34:54,640 --> 00:34:57,640
Speaker 2: you could use a compass to navigate near a magnetic

707
00:34:57,840 --> 00:34:58,440
Speaker 2: black hole.

708
00:34:59,080 --> 00:35:01,160
Speaker 1: So I mean black holes have a north and south pole.

709
00:35:01,320 --> 00:35:03,080
Speaker 2: Yeah, exactly, they have a north and south pole for

710
00:35:03,120 --> 00:35:05,880
Speaker 2: their spin as well. Right, A black hole that doesn't

711
00:35:05,920 --> 00:35:09,239
Speaker 2: spin is spherically symmetric, But a spinning black hole has

712
00:35:09,239 --> 00:35:12,200
Speaker 2: broken that symmetry because there has to be some axis

713
00:35:12,280 --> 00:35:14,640
Speaker 2: around which it's spinning. So that gives it a north

714
00:35:14,640 --> 00:35:17,680
Speaker 2: and south spin black hole, because that spin is what

715
00:35:17,760 --> 00:35:20,959
Speaker 2: generates the magnetic field. It also then has a north

716
00:35:20,960 --> 00:35:22,320
Speaker 2: and south magnetic pole.

717
00:35:22,640 --> 00:35:25,879
Speaker 1: Whoa, And so if I have a tiny spinning black hole,

718
00:35:25,920 --> 00:35:28,040
Speaker 1: then it would be attracted to my fridge door.

719
00:35:28,280 --> 00:35:31,479
Speaker 2: Right, Yes, it would be attracted to your fridge door.

720
00:35:31,920 --> 00:35:34,560
Speaker 2: Even if its gravity was too weak to hold it there,

721
00:35:34,640 --> 00:35:38,040
Speaker 2: its magnetic field might be powerful enough, because remember, magnetic

722
00:35:38,040 --> 00:35:41,680
Speaker 2: fields are much more powerful than gravity. So you make

723
00:35:41,719 --> 00:35:44,080
Speaker 2: a tiny black hole out of a few electrons, it

724
00:35:44,160 --> 00:35:46,640
Speaker 2: might not have very strong gravity, but the magnetic fields

725
00:35:46,640 --> 00:35:48,080
Speaker 2: could already be quite powerful.

726
00:35:48,200 --> 00:35:50,319
Speaker 1: Yeah, it's interesting to think that a black hole has

727
00:35:50,360 --> 00:35:53,800
Speaker 1: a north and south pole. I hear the north pole

728
00:35:53,800 --> 00:35:55,840
Speaker 1: of a black hole is where all the dark elves

729
00:35:55,880 --> 00:35:56,279
Speaker 1: hang out.

730
00:35:59,280 --> 00:36:01,360
Speaker 2: Are they making presence for dark Christmas?

731
00:36:02,280 --> 00:36:06,000
Speaker 1: And now they're just making a bunch of coal presents

732
00:36:06,040 --> 00:36:10,279
Speaker 1: for everyone? It's the opposite. It's the opposite. Can you

733
00:36:10,320 --> 00:36:12,920
Speaker 1: measure the magnetic field of a black hole from a distance?

734
00:36:13,040 --> 00:36:15,279
Speaker 2: In principle, if you were near the black hole, you

735
00:36:15,280 --> 00:36:17,320
Speaker 2: can do what we describe, which is used the compass.

736
00:36:17,880 --> 00:36:21,279
Speaker 2: We can't go near black holes, unfortunately, but we can

737
00:36:21,320 --> 00:36:25,160
Speaker 2: see the effect of black holes on nearby particles. Right,

738
00:36:25,200 --> 00:36:27,520
Speaker 2: black holes are almost never on their own. They formed

739
00:36:27,560 --> 00:36:29,840
Speaker 2: because they're in the middle of some dense blob of

740
00:36:29,920 --> 00:36:33,000
Speaker 2: matter they've been gobbling, so usually there's a lot of

741
00:36:33,000 --> 00:36:35,480
Speaker 2: stuff around them. And if you trace the path of

742
00:36:35,560 --> 00:36:38,759
Speaker 2: the charged particles near the black hole, then you can

743
00:36:38,800 --> 00:36:43,520
Speaker 2: measure something about its magnetic field. But those particles also

744
00:36:43,560 --> 00:36:46,279
Speaker 2: will generate a magnetic field. So teasing those two things

745
00:36:46,280 --> 00:36:47,520
Speaker 2: apart is quite tricky.

746
00:36:47,680 --> 00:36:47,919
Speaker 5: Mmm.

747
00:36:48,680 --> 00:36:50,560
Speaker 1: Sort of like give you throw a bunch of iron

748
00:36:51,160 --> 00:36:54,719
Speaker 1: filings feelings filings at a black hole, they would form

749
00:36:54,760 --> 00:36:56,799
Speaker 1: a pattern around the black hole, and that would tell you, Oh,

750
00:36:56,840 --> 00:36:59,960
Speaker 1: that's the magnetic field, that's where the north pole is pointing.

751
00:37:00,600 --> 00:37:03,359
Speaker 2: Yeah, it's filings. If it's little pieces of shaved iron,

752
00:37:03,400 --> 00:37:05,600
Speaker 2: it's fillings. If they came from people's teeth, which were.

753
00:37:05,480 --> 00:37:11,960
Speaker 1: You imagine both? I guess, I guess both would work.

754
00:37:12,239 --> 00:37:13,719
Speaker 2: I guess if you go near a black hole, it

755
00:37:13,800 --> 00:37:15,919
Speaker 2: might pull out your iron fillings. What if you file

756
00:37:16,000 --> 00:37:18,520
Speaker 2: some fillings, I'm going to find a complaint with the

757
00:37:18,520 --> 00:37:19,479
Speaker 2: black hole division if.

758
00:37:19,360 --> 00:37:21,920
Speaker 1: That happens, another full.

759
00:37:21,719 --> 00:37:24,280
Speaker 2: I think they're filled up already.

760
00:37:24,560 --> 00:37:27,320
Speaker 1: Yeah, all right, So then could we measure it potentially

761
00:37:27,320 --> 00:37:29,200
Speaker 1: from Earth? Like if we you know, we have these

762
00:37:29,239 --> 00:37:31,680
Speaker 1: pictures now of what we think are black holes. Could

763
00:37:31,719 --> 00:37:34,439
Speaker 1: we measure their magnetic feel from here?

764
00:37:34,800 --> 00:37:37,600
Speaker 2: Absolutely, we can and we have we have.

765
00:37:38,480 --> 00:37:40,839
Speaker 1: All right, well let's talk about that, but work, let's

766
00:37:40,880 --> 00:37:56,520
Speaker 1: take another quick break. All right, we're talking about the

767
00:37:56,560 --> 00:38:00,520
Speaker 1: polarity of a black hole. They're very polarizing black holes.

768
00:38:01,080 --> 00:38:03,600
Speaker 1: Some people love them, some people really love them.

769
00:38:04,480 --> 00:38:05,720
Speaker 2: Those are your only two choices.

770
00:38:06,880 --> 00:38:09,279
Speaker 1: Yeah, you either either love it or you don't love it.

771
00:38:10,320 --> 00:38:12,560
Speaker 2: Fill out this survey or what take your iron fillings?

772
00:38:12,600 --> 00:38:15,520
Speaker 1: Well, we talked about how black hole has a magnetic field,

773
00:38:15,560 --> 00:38:18,439
Speaker 1: but it's sort of not new information, right, Like it's

774
00:38:19,040 --> 00:38:21,399
Speaker 1: it's it's the product of its charge and it's been

775
00:38:22,600 --> 00:38:25,040
Speaker 1: so it's not like it has a fourth property that

776
00:38:25,080 --> 00:38:27,160
Speaker 1: you can find out about it. It's it's sort of

777
00:38:27,160 --> 00:38:29,680
Speaker 1: a derivative of its charge and spin.

778
00:38:30,080 --> 00:38:33,920
Speaker 2: Yeah, exactly, not derivative in the calculus sense, but derivative

779
00:38:34,000 --> 00:38:36,480
Speaker 2: in the like, oh you just copied that sense. It

780
00:38:36,560 --> 00:38:39,000
Speaker 2: comes out of the other properties. It's not a core

781
00:38:39,080 --> 00:38:41,880
Speaker 2: basic quantity of a black hole itself, unless the black

782
00:38:41,880 --> 00:38:44,360
Speaker 2: hole had a magnetic monopole in it, and then it

783
00:38:44,400 --> 00:38:46,839
Speaker 2: would be a core property. But you're right, it sort

784
00:38:46,840 --> 00:38:49,160
Speaker 2: of emerges from the other properties.

785
00:38:49,520 --> 00:38:51,800
Speaker 1: What do you mean if a black hole ada monopole.

786
00:38:51,920 --> 00:38:54,000
Speaker 2: If a black hole aida monopole would be something we

787
00:38:54,080 --> 00:38:56,799
Speaker 2: call a dionic black hole, and it would have its

788
00:38:56,800 --> 00:39:00,480
Speaker 2: own monopole magnetic field, just like the monopole that fell

789
00:39:00,520 --> 00:39:01,680
Speaker 2: into it, Right.

790
00:39:02,000 --> 00:39:04,279
Speaker 1: How would it ever eat a monopole number one?

791
00:39:04,320 --> 00:39:06,440
Speaker 2: A monopole would have to exist in the universe, and

792
00:39:06,480 --> 00:39:08,799
Speaker 2: we don't know that they do, but they might, and

793
00:39:08,840 --> 00:39:10,399
Speaker 2: then they would have to go near a black hole.

794
00:39:10,440 --> 00:39:11,400
Speaker 2: And then gobble gobble.

795
00:39:12,560 --> 00:39:15,279
Speaker 1: Could a black hole split a dipole into a two

796
00:39:15,280 --> 00:39:17,400
Speaker 1: monopoles that it eats one and it shoots off the

797
00:39:17,400 --> 00:39:17,759
Speaker 1: other one.

798
00:39:17,800 --> 00:39:20,440
Speaker 2: That would be an awesome feature of quantum gravity. Currently

799
00:39:20,480 --> 00:39:24,560
Speaker 2: in our predictions, know, you can't split a diepole because like,

800
00:39:24,600 --> 00:39:26,840
Speaker 2: where does that come from? It comes from the electron spinning,

801
00:39:26,880 --> 00:39:29,600
Speaker 2: So you're going to split the electron somehow, So we

802
00:39:29,640 --> 00:39:30,560
Speaker 2: don't know how to do that.

803
00:39:31,080 --> 00:39:32,640
Speaker 1: I don't know in general, can you tell a black

804
00:39:32,640 --> 00:39:33,799
Speaker 1: hole what it can or can't do?

805
00:39:35,880 --> 00:39:38,400
Speaker 2: If black holes are listening to this podcast, I apologize

806
00:39:38,400 --> 00:39:39,480
Speaker 2: for my presumptuousness.

807
00:39:40,920 --> 00:39:45,279
Speaker 1: They're going to come after your fridge watch out, all right, Well,

808
00:39:46,200 --> 00:39:49,040
Speaker 1: so what can we see of a black hole or

809
00:39:49,080 --> 00:39:49,799
Speaker 1: what have we seen?

810
00:39:50,160 --> 00:39:52,520
Speaker 2: So we've seen. The black holes have a huge effect

811
00:39:52,520 --> 00:39:55,480
Speaker 2: on nearby matter. They don't just suck stuff in, they

812
00:39:55,640 --> 00:39:59,560
Speaker 2: also shunt stuff away from themselves. Their magnetic feels can

813
00:39:59,600 --> 00:40:02,840
Speaker 2: be so strong that in falling particles can actually follow

814
00:40:02,880 --> 00:40:06,040
Speaker 2: those magnetic fields and then escape the black hole, you know,

815
00:40:06,080 --> 00:40:08,280
Speaker 2: the same way that like we've seen these aurora. Because

816
00:40:08,400 --> 00:40:11,880
Speaker 2: charge particles falling in towards the Earth end up spiraling

817
00:40:11,920 --> 00:40:14,080
Speaker 2: around our magnetic fields and then end up in the

818
00:40:14,120 --> 00:40:17,440
Speaker 2: North Pole. It's also possible when particles are falling in

819
00:40:17,480 --> 00:40:20,239
Speaker 2: towards a black hole. Basically the same thing happens, but

820
00:40:20,280 --> 00:40:22,880
Speaker 2: they get so much speed that they then escape the

821
00:40:22,920 --> 00:40:25,640
Speaker 2: grip of the black hole and they shoot out up

822
00:40:25,719 --> 00:40:28,439
Speaker 2: and down the North and South poles. And we see

823
00:40:28,480 --> 00:40:32,279
Speaker 2: these enormous jets from black holes. You see galaxies with

824
00:40:32,360 --> 00:40:35,040
Speaker 2: super massive black holes at their center, and then these

825
00:40:35,160 --> 00:40:38,759
Speaker 2: huge jets extending thousands of light years up and down,

826
00:40:38,840 --> 00:40:41,400
Speaker 2: sort of above and below the plane of the galaxy.

827
00:40:41,880 --> 00:40:44,640
Speaker 2: Those are jets from the central black hole, and they're

828
00:40:44,640 --> 00:40:46,320
Speaker 2: powered by its magnetic field.

829
00:40:46,680 --> 00:40:49,040
Speaker 1: Whoa wait, wait, wait, wait, hold on, it's not stuff

830
00:40:49,080 --> 00:40:51,719
Speaker 1: coming out of the black hole, is it right? It's

831
00:40:51,719 --> 00:40:53,680
Speaker 1: not right, because nothing can escape a black hole.

832
00:40:53,840 --> 00:40:56,759
Speaker 2: It's not something escaping a black hole. It's something having

833
00:40:56,760 --> 00:40:59,000
Speaker 2: a near miss. It's like fell in and then a

834
00:40:59,040 --> 00:41:02,520
Speaker 2: magnetic field outside the black hole, the same way we

835
00:41:02,560 --> 00:41:05,200
Speaker 2: have a magnetic field outside the atmosphere of the Earth.

836
00:41:05,400 --> 00:41:08,480
Speaker 2: The magnetic field that's outside the black hole guides those

837
00:41:08,520 --> 00:41:11,520
Speaker 2: particles towards the north and then they escape, but they

838
00:41:11,560 --> 00:41:13,160
Speaker 2: never went inside the event horizon.

839
00:41:14,320 --> 00:41:17,400
Speaker 1: I see now, I wonder if that means that a

840
00:41:17,440 --> 00:41:20,920
Speaker 1: black hole looks different to like an electron than it

841
00:41:20,960 --> 00:41:22,120
Speaker 1: does to a proton.

842
00:41:22,719 --> 00:41:26,040
Speaker 2: Potentially, they definitely do look a little bit different. I mean,

843
00:41:26,080 --> 00:41:28,879
Speaker 2: a proton and an electron have different charges, and so

844
00:41:29,160 --> 00:41:32,960
Speaker 2: they're affected differently by those magnetic fields. But all these

845
00:41:33,000 --> 00:41:36,000
Speaker 2: particles do see the same event horizon. The event horizon

846
00:41:36,040 --> 00:41:37,920
Speaker 2: is the event horizon is the event horizon.

847
00:41:39,160 --> 00:41:41,799
Speaker 1: But wouldn't they like their paths near a black hole

848
00:41:41,920 --> 00:41:44,759
Speaker 1: be different, in which case the point at which they

849
00:41:44,760 --> 00:41:46,680
Speaker 1: would definitely fall in is different.

850
00:41:46,960 --> 00:41:49,399
Speaker 2: Yeah, the paths near the event horizon are different because

851
00:41:49,400 --> 00:41:52,560
Speaker 2: they are affected by magnetic fields differently, and their masses

852
00:41:52,560 --> 00:41:55,680
Speaker 2: are different, et cetera, and their charges are different. But

853
00:41:55,719 --> 00:41:58,319
Speaker 2: the event horizon is still just the event horizon. That's

854
00:41:58,360 --> 00:42:00,839
Speaker 2: a feature of the curvature of space. It's not an

855
00:42:00,880 --> 00:42:03,799
Speaker 2: issue of like the forces on the particles. Remember, it's

856
00:42:03,840 --> 00:42:06,120
Speaker 2: a product of the black hole itself.

857
00:42:08,120 --> 00:42:10,160
Speaker 1: And that's just from the mcdaide field of the black

858
00:42:10,160 --> 00:42:13,439
Speaker 1: hole itself. You mentioned earlier that the stuff swirling around

859
00:42:13,520 --> 00:42:15,520
Speaker 1: it can also make mcnad fields.

860
00:42:15,719 --> 00:42:19,480
Speaker 2: Yeah, exactly. There's huge accretion disks surrounding most black holes,

861
00:42:19,600 --> 00:42:21,759
Speaker 2: especially the ones at the center of galaxies that have

862
00:42:21,840 --> 00:42:24,480
Speaker 2: been feeding on gas and dust, and so there's a

863
00:42:24,520 --> 00:42:27,120
Speaker 2: lot of stuff that has fallen close to the black

864
00:42:27,120 --> 00:42:30,080
Speaker 2: hole and is still in orbit around it. Remember, things,

865
00:42:30,160 --> 00:42:32,880
Speaker 2: unless they fall directly towards the center of the black

866
00:42:32,880 --> 00:42:35,239
Speaker 2: hole or towards the event horizon, they're still going to

867
00:42:35,320 --> 00:42:37,839
Speaker 2: have some angular momentum. You can orbit a black hole

868
00:42:37,880 --> 00:42:40,359
Speaker 2: the same way the Moon orbits the Earth. Black Holes

869
00:42:40,360 --> 00:42:43,400
Speaker 2: are not like literally sucking things in. They're just gravity, right,

870
00:42:43,440 --> 00:42:46,439
Speaker 2: They're just curvature of space. You could in principle, orbit

871
00:42:46,480 --> 00:42:49,520
Speaker 2: a black hole forever and never fall in. But if

872
00:42:49,520 --> 00:42:52,080
Speaker 2: you're in this big disc of gas and dust, you're

873
00:42:52,080 --> 00:42:53,719
Speaker 2: also going to have friction. You're going to bump up

874
00:42:53,719 --> 00:42:55,880
Speaker 2: against each other, and some stuff is going to end

875
00:42:55,960 --> 00:42:58,440
Speaker 2: up falling in. But before it does. You know, this

876
00:42:58,640 --> 00:43:01,920
Speaker 2: huge disc of gas and tidal forces are heating it up,

877
00:43:01,960 --> 00:43:04,680
Speaker 2: so it's really hot and energetic and glowing in the

878
00:43:04,880 --> 00:43:07,640
Speaker 2: X ray. And because it's a lot of charged particles

879
00:43:07,640 --> 00:43:11,600
Speaker 2: swirling around, it has its own very strong magnetic field.

880
00:43:12,360 --> 00:43:15,040
Speaker 1: Like it adds to the black holes. Is a magnetic

881
00:43:15,080 --> 00:43:18,040
Speaker 1: field or it cancels it? Or how does it interact

882
00:43:18,080 --> 00:43:20,960
Speaker 1: with the black holes? Is magnetic field itself?

883
00:43:21,080 --> 00:43:23,960
Speaker 2: Yeah, great question, and that's essentially the cutting edge of

884
00:43:23,960 --> 00:43:26,600
Speaker 2: our research right now. It's like, what do the black

885
00:43:26,600 --> 00:43:29,440
Speaker 2: hole magnetic fields look like? What are the magnetic fields

886
00:43:29,440 --> 00:43:31,879
Speaker 2: coming from the disc look like? It depends a lot

887
00:43:31,960 --> 00:43:35,880
Speaker 2: on how calm or how turbulent that accretion disc is. Like,

888
00:43:35,920 --> 00:43:40,120
Speaker 2: if everything is flowing very nicely, like Saturn's rings, then

889
00:43:40,160 --> 00:43:42,520
Speaker 2: all those magnetic fields will add up very nicely and

890
00:43:42,520 --> 00:43:45,080
Speaker 2: they'll all contribute in the same direction. But if it's

891
00:43:45,080 --> 00:43:48,120
Speaker 2: sort of chaotic, like a big storm, then the magnetic

892
00:43:48,120 --> 00:43:50,959
Speaker 2: fields generated by those particles might cancel each other out.

893
00:43:51,360 --> 00:43:53,720
Speaker 2: We also don't really know how much of the magnetic

894
00:43:53,719 --> 00:43:55,799
Speaker 2: field is coming from the disc and how much is

895
00:43:55,800 --> 00:43:58,600
Speaker 2: coming from the black hole itself. We can't separate those

896
00:43:58,600 --> 00:43:59,720
Speaker 2: two things very easily.

897
00:44:00,239 --> 00:44:01,920
Speaker 1: We can't because it's just too complicated.

898
00:44:02,320 --> 00:44:05,319
Speaker 2: Yeah, we don't really understand how much magnetic field there

899
00:44:05,360 --> 00:44:07,520
Speaker 2: is coming from the accretion disc because it's not something

900
00:44:07,560 --> 00:44:10,520
Speaker 2: we've modeled very well. We have lots of competing theories

901
00:44:10,560 --> 00:44:13,239
Speaker 2: about what the accretion disc looks like, and so to

902
00:44:13,280 --> 00:44:15,960
Speaker 2: separate out the black holes magnetic field you have to

903
00:44:16,040 --> 00:44:18,799
Speaker 2: understand the rest of the magnetic field very well. But

904
00:44:18,920 --> 00:44:21,080
Speaker 2: we've tried to do that. We've been able to take

905
00:44:21,120 --> 00:44:24,320
Speaker 2: these images of the event horizon or images of the

906
00:44:24,360 --> 00:44:27,759
Speaker 2: stuff near the event horizon, and recent pictures of that

907
00:44:28,000 --> 00:44:30,359
Speaker 2: have used some clever tricks to try to understand what

908
00:44:30,400 --> 00:44:33,240
Speaker 2: the magnetic fields look like near the black hole.

909
00:44:33,520 --> 00:44:35,600
Speaker 1: WHOA, how can you do that? Well, first of all,

910
00:44:35,600 --> 00:44:37,560
Speaker 1: you can't really see the event horizon, right, You only

911
00:44:37,600 --> 00:44:39,960
Speaker 1: see the shadow of the black hole, which is different.

912
00:44:40,200 --> 00:44:43,200
Speaker 2: Yeah, that's exactly right. We're just not seeing photons from

913
00:44:43,200 --> 00:44:45,680
Speaker 2: the event horizon or anywhere near it in a way

914
00:44:45,719 --> 00:44:49,279
Speaker 2: that lines up really really well with predictions of general relativity.

915
00:44:49,640 --> 00:44:52,720
Speaker 2: And so that's an indirect piece of evidence for black holes.

916
00:44:52,760 --> 00:44:55,839
Speaker 2: Another frustrating the indirect piece of evidence. But we can

917
00:44:55,960 --> 00:44:58,680
Speaker 2: see the stuff the accretion disc nearby it. That's why

918
00:44:58,719 --> 00:45:01,360
Speaker 2: these photos look sort of like a big crispy cream donut.

919
00:45:01,440 --> 00:45:01,560
Speaker 3: Right.

920
00:45:01,560 --> 00:45:04,680
Speaker 2: You have the hot gas glowing near the accretion disk,

921
00:45:04,960 --> 00:45:07,200
Speaker 2: and those photons that come from the gas that are

922
00:45:07,200 --> 00:45:10,520
Speaker 2: emitted from these high speed charged particles. They can give

923
00:45:10,600 --> 00:45:13,279
Speaker 2: us some clues about the magnetic field that they're in

924
00:45:13,719 --> 00:45:17,400
Speaker 2: because the magnetic fields will polarize these photons. It changes

925
00:45:17,400 --> 00:45:19,600
Speaker 2: how the photons wiggle, like are they wiggling this way

926
00:45:19,640 --> 00:45:22,600
Speaker 2: or they're wiggling that way. And if the magnetic fields

927
00:45:22,600 --> 00:45:25,560
Speaker 2: are all nicely organized, then the polarization of those photons

928
00:45:25,560 --> 00:45:28,200
Speaker 2: will be nicely organized. And if the magnetic fields are

929
00:45:28,200 --> 00:45:30,759
Speaker 2: all a big hot mess, then the polarizations will all

930
00:45:30,800 --> 00:45:34,680
Speaker 2: be scrambled. So they recently reanalyze the image of the

931
00:45:34,719 --> 00:45:37,360
Speaker 2: black hole at the heart of the eighty seven galaxy

932
00:45:37,640 --> 00:45:40,440
Speaker 2: to try to measure the polarization of these photons, not

933
00:45:40,520 --> 00:45:42,840
Speaker 2: just like where's it bright and where's it dim, but

934
00:45:42,960 --> 00:45:45,960
Speaker 2: in which direction of those photons wiggling, and that give

935
00:45:46,000 --> 00:45:48,080
Speaker 2: them some clues about what might be happening in the

936
00:45:48,080 --> 00:45:49,000
Speaker 2: accretion disc.

937
00:45:49,000 --> 00:45:52,280
Speaker 1: WHOA, which would then sort of tell you what's going on, right.

938
00:45:52,400 --> 00:45:55,480
Speaker 2: Yeah, exactly, And it's really fun. They had two models

939
00:45:55,520 --> 00:45:58,799
Speaker 2: of black hole accretion disc magnetic fields. One of them

940
00:45:58,840 --> 00:46:04,360
Speaker 2: was called sane stable and normal evolution as ANE, and

941
00:46:04,480 --> 00:46:08,640
Speaker 2: the other one is called mad magnetically arrested disc. So

942
00:46:08,760 --> 00:46:10,920
Speaker 2: it was a big competition between the scene and the

943
00:46:11,080 --> 00:46:11,840
Speaker 2: MAD groups.

944
00:46:14,680 --> 00:46:16,480
Speaker 1: They're like, no, I'm saying, no, you're mad.

945
00:46:17,600 --> 00:46:21,200
Speaker 2: I mean, you've heard of crazy astronomical acronyms before, but

946
00:46:21,280 --> 00:46:25,160
Speaker 2: this is like dueling crazy acronyms. I'm impressed by their coordination.

947
00:46:25,520 --> 00:46:27,440
Speaker 1: Yeah, so each one of these was invented by a

948
00:46:27,440 --> 00:46:28,160
Speaker 1: different group.

949
00:46:28,600 --> 00:46:31,520
Speaker 2: Yeah, exactly. They like competing theories for how the accretion

950
00:46:31,680 --> 00:46:34,719
Speaker 2: disc will come together. And basically the difference between them

951
00:46:35,200 --> 00:46:37,719
Speaker 2: is how turbulent is it and how coherent is it?

952
00:46:38,200 --> 00:46:40,200
Speaker 2: You know, is it basically all scrambled and you don't

953
00:46:40,239 --> 00:46:42,480
Speaker 2: get a strong magnetic field, or is it kind of

954
00:46:42,520 --> 00:46:45,279
Speaker 2: coherent and well ordered, in which case you do get

955
00:46:45,320 --> 00:46:47,400
Speaker 2: a stronger build up of the magnetic fields from the

956
00:46:47,440 --> 00:46:49,000
Speaker 2: accretion disc, right right?

957
00:46:49,239 --> 00:46:51,279
Speaker 1: Or are they all just crazy physicists.

958
00:46:52,719 --> 00:46:54,759
Speaker 2: Yeah, And so for a long time people thought that

959
00:46:54,880 --> 00:46:58,400
Speaker 2: the same scenario was more natural sort of weaker fields

960
00:46:58,440 --> 00:47:01,560
Speaker 2: because everything would be sort of more scrambled. But what

961
00:47:01,680 --> 00:47:04,920
Speaker 2: they measured is more consistent with the mad scenario that

962
00:47:05,000 --> 00:47:08,040
Speaker 2: things are like nicely organized, so they all add up

963
00:47:08,080 --> 00:47:10,640
Speaker 2: to give more powerful magnetic fields than people.

964
00:47:10,480 --> 00:47:14,320
Speaker 1: Suspected, meaning that the black hole is not as chaotic

965
00:47:14,360 --> 00:47:15,320
Speaker 1: as we thought it was.

966
00:47:15,640 --> 00:47:17,360
Speaker 2: Yeah, it turns out to be a little bit tidy.

967
00:47:17,600 --> 00:47:21,200
Speaker 1: Wait, the mad scenario is more sane than the same scenario.

968
00:47:23,640 --> 00:47:26,480
Speaker 2: The mad scenario is more like our universe. It's the

969
00:47:26,520 --> 00:47:28,000
Speaker 2: one where things are better organized.

970
00:47:28,080 --> 00:47:32,680
Speaker 1: Yeah, it sounds like physicists are just trying to drive

971
00:47:32,760 --> 00:47:36,400
Speaker 1: as mad. All right, Well, I think that sort of

972
00:47:36,440 --> 00:47:39,759
Speaker 1: answers the question. Black holes do have magnetic fields. I

973
00:47:39,840 --> 00:47:41,880
Speaker 1: mean they have Spain in charge, which means they'd have

974
00:47:42,040 --> 00:47:44,600
Speaker 1: magnetic fields. You can take a black holes, stick it

975
00:47:44,680 --> 00:47:47,040
Speaker 1: on your fridge. You can use it to mess up

976
00:47:47,080 --> 00:47:50,560
Speaker 1: your friend's compass. But measuring it might be a little

977
00:47:50,560 --> 00:47:53,799
Speaker 1: bit tricky because it's so far away, and there's also

978
00:47:53,920 --> 00:47:58,040
Speaker 1: these weird physics and dynamics going on or around outside

979
00:47:58,080 --> 00:47:58,200
Speaker 1: of it.

980
00:47:58,360 --> 00:48:00,440
Speaker 2: That's right. We can't know what's going on inside a

981
00:48:00,520 --> 00:48:02,960
Speaker 2: black hole, but magnetic fields give us a pretty good

982
00:48:03,000 --> 00:48:05,359
Speaker 2: clue as to what's going on near a black hole,

983
00:48:05,840 --> 00:48:08,520
Speaker 2: which one day might help us gain some clues about

984
00:48:08,520 --> 00:48:10,640
Speaker 2: what's going on past the event horizon.

985
00:48:11,239 --> 00:48:14,200
Speaker 1: Whoa do you think we can use magnets to see

986
00:48:14,239 --> 00:48:16,160
Speaker 1: what's inside of a black hole? It's kind of what

987
00:48:16,200 --> 00:48:16,600
Speaker 1: you're saying.

988
00:48:16,760 --> 00:48:19,680
Speaker 2: Well, in general relativity we definitely cannot, But in a

989
00:48:19,840 --> 00:48:22,880
Speaker 2: quantum version, with quantum gravity, there could be some correlation

990
00:48:23,000 --> 00:48:25,920
Speaker 2: between the information on the surface of the event horizon

991
00:48:26,000 --> 00:48:29,800
Speaker 2: itself and what's going on inside. There could be some feature,

992
00:48:29,920 --> 00:48:32,800
Speaker 2: some hair to the black hole, and that could affect,

993
00:48:32,800 --> 00:48:36,320
Speaker 2: for example, the radiation and the magnetic fields. And so eventually,

994
00:48:36,360 --> 00:48:39,440
Speaker 2: if we get detailed enough information and better theories of

995
00:48:39,520 --> 00:48:42,279
Speaker 2: quantum gravity, we might be able to see what's inside them.

996
00:48:42,520 --> 00:48:43,640
Speaker 1: That would be insane.

997
00:48:43,880 --> 00:48:45,000
Speaker 2: I wouldn't be mad about it.

998
00:48:46,440 --> 00:48:48,560
Speaker 1: Well, you know what they say, wearing magnets can really

999
00:48:48,640 --> 00:48:49,080
Speaker 1: help you out.

1000
00:48:49,800 --> 00:48:52,399
Speaker 2: Do they say that that sounds like pseudoscience?

1001
00:48:55,320 --> 00:48:58,480
Speaker 1: Well, honestly, all this black holes so also sounds a

1002
00:48:58,480 --> 00:48:59,600
Speaker 1: little bit like sseuiccience.

1003
00:49:00,000 --> 00:49:02,080
Speaker 2: Definitely not the final word on how any of this

1004
00:49:02,160 --> 00:49:04,560
Speaker 2: stuff works. Is just science in progress.

1005
00:49:05,440 --> 00:49:11,000
Speaker 1: I see, it's not pseudoscience. It's pre science science, and

1006
00:49:11,080 --> 00:49:15,480
Speaker 1: it's key. Everything is pre science. Nothing is the proto science.

1007
00:49:15,520 --> 00:49:16,919
Speaker 1: That sounds better proto.

1008
00:49:16,680 --> 00:49:18,520
Speaker 2: Science science in action.

1009
00:49:18,760 --> 00:49:20,239
Speaker 1: About that, that's right, you don't want to be a

1010
00:49:20,600 --> 00:49:24,760
Speaker 1: pre scientist. All right? Well, another reminder about the incredible

1011
00:49:24,800 --> 00:49:27,480
Speaker 1: mysteries out there in the universe and how they're staring

1012
00:49:27,600 --> 00:49:29,719
Speaker 1: us right in our telescopes. You can see them, you

1013
00:49:29,800 --> 00:49:32,320
Speaker 1: can point telescopes, you can measure things about them, but

1014
00:49:33,520 --> 00:49:35,680
Speaker 1: all you see is pure.

1015
00:49:36,840 --> 00:49:39,239
Speaker 2: Unknown and their magnetic personalities.

1016
00:49:39,480 --> 00:49:41,840
Speaker 1: That's right, the riz. Well, we hope you enjoyed that.

1017
00:49:42,239 --> 00:49:44,879
Speaker 1: Thanks for joining us. See you next time.

1018
00:49:49,680 --> 00:49:52,520
Speaker 2: For more science and curiosity, come find us on social

1019
00:49:52,600 --> 00:49:56,480
Speaker 2: media where we answer questions and post videos. We're on Twitter,

1020
00:49:56,640 --> 00:50:00,239
Speaker 2: disc Org, Instant, and now TikTok. Thanks for listening, and

1021
00:50:00,320 --> 00:50:02,960
Speaker 2: remember that Daniel and Jorge Explain the Universe is a

1022
00:50:03,080 --> 00:50:07,600
Speaker 2: production of iHeartRadio. For more podcasts from iHeartRadio, visit the

1023
00:50:07,719 --> 00:50:11,839
Speaker 2: iHeartRadio app, Apple Podcasts, or wherever you listen to your

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Speaker 2: favorite shows.