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Speaker 4: Hey Danian, what do you think makes black holes so interesting?
Speaker 2: You know?
Speaker 1: I think the mystery, the finality of it, the weirdness
Speaker 1: of it.
Speaker 4: For sure, they're like a magnet for fascination.
Speaker 1: They absolutely are for curiosity, for investigation, for dedication.
Speaker 4: And it's not just physicists. Everyone seems to have questions
Speaker 4: about black holes.
Speaker 1: Yeah, they seem to be sort of mentally magnetic.
Speaker 4: So black holes attract matter and also questions.
Speaker 1: They definitely attract questions. They seem to repel understanding.
Speaker 4: Or they just repel physicists.
Speaker 1: I'm pretty sure they'd be happy to suck me right in.
Speaker 4: I don't think I want to go down that rabbit hole.
Speaker 5: Hi.
Speaker 4: I am Hora May Cartoons, an author of Oliver's Great
Speaker 4: Big Universe.
Speaker 1: Hi. I'm Daniel. I'm a particle physicist and a professor
Speaker 1: at UC Irvine, and I desperately want to know what's
Speaker 1: inside those.
Speaker 4: Black holes, if there's even an inside. Right do we
Speaker 4: know that they have an inside?
Speaker 1: We don't really know anything beyond the event horizon at all.
Speaker 1: In some sense, the interior of a black hole could
Speaker 1: be like another universe.
Speaker 4: Whoa like We could be living inside of a black
Speaker 4: hole right now? Is that possible?
Speaker 1: I think that gives me a mental black hole even
Speaker 1: thinking about it.
Speaker 4: Hi, suckered you write in, But anyways, welcome to our podcast,
Speaker 4: Daniel and Jorge Explain the Universe, a production of iHeartRadio.
Speaker 1: In which we try our best not to give you
Speaker 1: a headache while we contemplate the deepest secrets of the universe.
Speaker 1: We want to understand everything that's out there, from the
Speaker 1: tiniest little bits to the hugest swirling black holes and
Speaker 1: everything in between, because we think that it's possible somehow
Speaker 1: to make sense of it all, to understand it, to
Speaker 1: predict it, and to explain all of it to you.
Speaker 4: Yeah, that's right. We try to be the advil or
Speaker 4: tile and all to your understanding of the universe, not
Speaker 4: give you a headache about how amazing things are, but
Speaker 4: rather try to ease the pain of trying to wrap
Speaker 4: your mind around this amazing cost mooves we live in.
Speaker 4: I think it was as your prescription for physics.
Speaker 1: Well, everybody out there is going to need like another
Speaker 1: kind of health insurance now physics health insurance.
Speaker 4: The physicists have special health insurance for you know, headaches
Speaker 4: and mind bending.
Speaker 1: We're going to help you cover the cost of understanding
Speaker 1: the universe because while physics has made lots of progress
Speaker 1: in understanding the way the universe works, there are still
Speaker 1: huge gaps in our knowledge. In fact, we're pretty sure
Speaker 1: there's more that we don't understand than that we do,
Speaker 1: and a lot of those mysteries might have answers waiting
Speaker 1: for us beyond the curtain of the event horizon.
Speaker 4: Yeah, as we've talked about, we only know about five
Speaker 4: percent of the whole universe. The rest, the other ninety
Speaker 4: five percent is a complete mystery. And even within the
Speaker 4: five percent that we think we know, there are still
Speaker 4: huge holes in our understanding of how things work and
Speaker 4: what can happen out there in the universe.
Speaker 1: The best way to unravel some of the open mysteries
Speaker 1: is to embrace the unknown, is to dive into our
Speaker 1: ignorance and try to reveal something new about the universe.
Speaker 1: Often this happens at the extreme points of the universe,
Speaker 1: places where things are super duper hot, or super duper dense,
Speaker 1: or super duper crazy, because it's that those places that
Speaker 1: our understanding breaks down. That's one reason why black holes
Speaker 1: are so attractive to physicists, because they are where our
Speaker 1: current theories have to break.
Speaker 4: Yeah, it seems like there's no place in the universe
Speaker 4: that is more extreme or mysterious than a black hole.
Speaker 4: We have so many questions about that. Everyone has questions
Speaker 4: about it. It seems that it attracts not just mass
Speaker 4: and energy, but also curiosity.
Speaker 1: It does absolutely. I don't know if it sucks in curiosity,
Speaker 1: or it's radiating curiosity, or how the whole curiosity field works.
Speaker 4: Talking talking radiation of curiosity exactly.
Speaker 1: Maybe it's consuming anti curiosity while radiating.
Speaker 4: Curiosity anti curiosity. Oh, that's an interesting concept, but what
Speaker 4: is that?
Speaker 1: I don't know. That's what we're trying to generate on
Speaker 1: this podcast. We're trying to satisfy everybody's curiosity or are
Speaker 1: we just trying to stoke it. I'm not even sure anymore.
Speaker 4: Yeah, it sounds like you're trying to annihilate people curiosity.
Speaker 1: No, I guess we're trying to generate anti confusion particles.
Speaker 1: How about that?
Speaker 4: Oh, there you go, rock Ons, get a Tino's exactly,
Speaker 4: the AHA particles, that's what we're after.
Speaker 1: Yeah, I want to be one with the AHA field.
Speaker 1: But there are still very basic questions about how black
Speaker 1: holes work, what it means to be near black hole,
Speaker 1: what you would experience, what you might measure with your
Speaker 1: devices near a black hole. We've talked about the massive
Speaker 1: black holes, we talked about the charge of black holes,
Speaker 1: we talked about the spin of black holes. But there
Speaker 1: are still even more basic things we can think about
Speaker 1: when it comes to black holes.
Speaker 4: So today on the podcast, we'll be tackling the question
Speaker 4: do black holes have magnetic fields?
Speaker 1: Like?
Speaker 4: Are they attractive or repulsive? Do they have raised or not?
Speaker 1: Can you use black holes to find lost wedding rings
Speaker 1: on the beach? I knew there was a practical application
Speaker 1: of my research somewhere.
Speaker 4: Could you use it to detect your wedding ring on
Speaker 4: the beach when in it just swallow up the whole beach?
Speaker 1: Then you'd have a good excuse for why you lost
Speaker 1: your wedding ring there was a black hole on the beach.
Speaker 4: Yeah, and you would technically know where it is. It's
Speaker 4: inside the black hole. You just you know you can't
Speaker 4: get it ever.
Speaker 1: Yeah, exactly. No number of explaining on's is going to
Speaker 1: get you out of that jam.
Speaker 4: Yeah, but yeah, it's an interesting question. Do black holes
Speaker 4: have magnetic field? And I know we've did a whole
Speaker 4: episode on whether black holes have a charge, right, Yeah,
Speaker 4: and so this is different, this is more about the
Speaker 4: magnetic field.
Speaker 1: Yeah, we did one on charge, we did another one
Speaker 1: on spin. There's not that much stuff you can actually
Speaker 1: know about black holes, and we know so little, so
Speaker 1: I'm always excited to talk more about it.
Speaker 4: Then we do a whole episode on the hairiness of
Speaker 4: a black hole.
Speaker 1: That's true, their lack of hairiness actually their smooth shavenness.
Speaker 4: Yeah. Well, this is an interesting question, and so as usual,
Speaker 4: we were wondering how many people out there had thought
Speaker 4: about whether black holes have magnetic fields, and if they do,
Speaker 4: what do they look like or feel like.
Speaker 1: I think it's possible that they do.
Speaker 4: I think if I'm not too sure exactly after rationale
Speaker 4: it's but somehow I feel like it might be possible
Speaker 4: for black holes to have magnetic fields.
Speaker 6: I think they do if from the spiraling matter that's
Speaker 6: been consumed by the black hole. Whether or not they
Speaker 6: are magnetic in their core, whatever their core is, if
Speaker 6: you can have a call in a black hole, I
Speaker 6: don't know, but by virtue of the whole of the
Speaker 6: object that's wholy, yes.
Speaker 7: I do not believe so, only because I do not
Speaker 7: believe there are any charged particles within a black hole. However,
Speaker 7: since we do see jets coming from black holes at times,
Speaker 7: that could be totally wrong about that.
Speaker 8: I don't really know, but if I had to guess,
Speaker 8: I think they would like something to do with the
Speaker 8: hawking radiation being magnetized somehow, or so.
Speaker 5: The black hole itself beyond the event horizon.
Speaker 3: I don't think we can know that, but the area
Speaker 3: around the black hole where the Acresian disk is probably
Speaker 3: can have a magnetic field.
Speaker 1: Black Holes have mass, and they have spin, and I
Speaker 1: believe they have a charge. So if something has a charge,
Speaker 1: it should also have a magnetic field. Probably a little
Speaker 1: squirrely with.
Speaker 9: The amount of gravitational forces going on, but going with
Speaker 9: the yes.
Speaker 10: Yes, I'm pretty sure black holes have magnetic fields because
Speaker 10: whenever a particle let's charged enters it, the electric charge
Speaker 10: is conserved. So I guess a black hole would need
Speaker 10: to have that magnetic field that the particle had.
Speaker 4: I have no idea that.
Speaker 10: As a wild guest, I would say yes, they have
Speaker 10: probably vacuumed app some magnetic vibes along the way.
Speaker 1: Black holes do have magnetic fields. I'm pretty sure that
Speaker 1: the Beatles wrote a song about it. Magnetic field forever.
Speaker 9: If a black hole is churning around, does it create
Speaker 9: a magnetic field? Is there a north pole to a
Speaker 9: black hole? I wonder if magnetism can escape gravity or
Speaker 9: is immune to it.
Speaker 1: I think magnetize are neutron stars with a magnetic charge.
Speaker 1: I'm not sure about a black hole. Maybe if it's
Speaker 1: spinning and has an electric charge.
Speaker 5: I think that if a black hole a bunch of
Speaker 5: large stuff with a magnetic field, and the black hole
Speaker 5: would get a magnetic field. I'm gonna say yes, because
Speaker 5: there's one other three things that have that black present
Speaker 5: so that we can measure, but I forget one of them.
Speaker 5: So there are spin, there, mass, and electromagnetic force. So
Speaker 5: I'm gonna say yes.
Speaker 4: All right, interesting answers from a lot of magnetic people.
Speaker 1: Yeah, you could tell a lot of people had not
Speaker 1: thought about this question at all. They seem to sort
Speaker 1: of come up with their answers on the fly.
Speaker 4: Yeah, it's kind of a polarizing question.
Speaker 1: People either retracted or repelled by it. Yeah.
Speaker 4: Yeah, Well it seemed to attract definitely a lot of
Speaker 4: ideas about what's going on in the black hole, and
Speaker 4: so let's dive right into it. Daniel take us through
Speaker 4: the basics of black holes and how they relate to electromagnetism.
Speaker 1: So fundamentally, we don't really know what black holes are
Speaker 1: in our actual universe, like the physical things that are
Speaker 1: at the center of the galaxy, or they have really
Speaker 1: dense stuff orbiting them really closely. We're not really sure
Speaker 1: what those things are, but we do have a concept
Speaker 1: in our theory. General relativity predicts a kind of black
Speaker 1: hole that we know. Again, general relativity can't be right,
Speaker 1: so this theoretical object can't actually align with what's out
Speaker 1: there in the universe, but it gives us something to
Speaker 1: dig into, something that play with. And because general relativity
Speaker 1: tells us that gravity is not a force between objects
Speaker 1: the way Newton described it, but instead a curvature of
Speaker 1: space time, there's something weird that can happen when you
Speaker 1: get enough mass, enough energy density actually together in one place,
Speaker 1: which is that space can curve so much that the
Speaker 1: inside is essentially cut off from the outside. There's a
Speaker 1: place beyond which space is curved so that it only
Speaker 1: points towards the center of the black hole, meaning any
Speaker 1: object that falls past that event horizon will always end
Speaker 1: up at the center of the black hole. And so
Speaker 1: this is the basic concept of a black hole, sort
Speaker 1: of extreme space time curvature that generates this event horizon
Speaker 1: past which nothing can.
Speaker 4: Escape, right right, Because I feel like that's always. One
Speaker 4: of the carriats we have to point out is that
Speaker 4: the bending of space time, right, it's not just sort
Speaker 4: of space, it's also sort of like what happens in
Speaker 4: the future.
Speaker 1: There are definitely time related effects. Also, mass bends space
Speaker 1: and creates this event horizon, it also bends time. So
Speaker 1: you are near a black hole, for example, a distant observer,
Speaker 1: we'll see your clock go more slowly, and near black holes,
Speaker 1: space and time are very confusing, and in fact, the
Speaker 1: whole concept of space time is easier to understand in
Speaker 1: special relativity when you have flat space. In general relativity,
Speaker 1: which direction is space and which direction is time becomes
Speaker 1: very very confusing, and in some cases it's not even clear.
Speaker 4: And so, as you said, it's something that physics predicts
Speaker 4: is happening out there in the universe because we see
Speaker 4: around us and it seems like, you know, the Sun
Speaker 4: is bending space around and the Earth is bending space around,
Speaker 4: and we're bending space around us. But if you take
Speaker 4: it to an extreme, it predicts something called a black hole.
Speaker 1: Yeah, and a lot of people imagine a black hole
Speaker 1: in a sort of Newtonian way. They think, oh, gravity
Speaker 1: is so strong that you have to go faster than
Speaker 1: the speed of light in order to escape it. But
Speaker 1: it's not a question of forces, it's not a question
Speaker 1: of a velocity. It's not a Newtonian picture at all.
Speaker 1: It really tells you that the story of how gravity
Speaker 1: works is very, very different. That you're literally trapped inside
Speaker 1: this event horizon. No amount of velocity, no force can
Speaker 1: ever escape it because the shape of space itself has changed.
Speaker 1: And so if you imagine space is this like emptiness
Speaker 1: in which things float, then you need a new idea.
Speaker 1: General relativity tells us we could describe it as this
Speaker 1: sort of stuff with curvature to it, that we're moving
Speaker 1: through that curvature, and that curvature is not sitting inside
Speaker 1: some like deeper, larger space that you might be tempted
Speaker 1: to imagine. That's all there is, and we are trapped
Speaker 1: inside of it and there's nothing on the outside of
Speaker 1: it as far as we know.
Speaker 4: Right, right, and as usual, we also have to give
Speaker 4: the cavet that black holes are technically theoretical, right, Like
Speaker 4: we've seen things that sort of behave like black holes,
Speaker 4: but we haven't sort of been in front of one
Speaker 4: or touched it, right, that's right.
Speaker 1: And what we're describing is a prediction of general relativity,
Speaker 1: which we know to be very accurate in most circumstances,
Speaker 1: except we expect it to break down when things get
Speaker 1: very very intense and very very small. And so, for example,
Speaker 1: general relativity predicts that at the heart of one of
Speaker 1: these black holes is a singularity, a point of infinite density.
Speaker 1: This runaway gravity just goes on forever, and you get
Speaker 1: infinite curvature at the heart of the black hole. But
Speaker 1: we don't think that that's really happening because we know
Speaker 1: that that's in conflict with quantum mechanics. And so real
Speaker 1: black holes, if they exist out there in the universe,
Speaker 1: can't align perfectly with this theoretical description of a general
Speaker 1: relativity black hole. There has to be some quantum fuzziness
Speaker 1: to it, some other version of a black hole. And
Speaker 1: we talked recently on the podcast how quantum black holes
Speaker 1: probably radiate. They're not perfectly black due to Hawking radiation,
Speaker 1: and there must be other changes we need to make
Speaker 1: from this general relativity picture of a black hole to
Speaker 1: a realistic quantum gravity black hole that we don't even
Speaker 1: know how to describe. And you're right that the things
Speaker 1: we've seen out there in the universe, at the heart
Speaker 1: of our galaxy, etc. We're not even sure if they
Speaker 1: actually are black holes, because we've not technically observed an
Speaker 1: event horizon. All we've seen is that there are very
Speaker 1: dense objects, very massive, very small, very compact, and so
Speaker 1: we suspect that they are black holes, but they could
Speaker 1: be something else. These days, there are quantum gravity inspired
Speaker 1: ideas for other things that could fit the data. Fuzzballs
Speaker 1: or dark stars, etc. Yeah, all kinds of fun names.
Speaker 4: I wonder if we should maybe start calling black holes
Speaker 4: and not black holes then maybe or.
Speaker 1: Maybe just black holes with a question mark black holes
Speaker 1: really dark objects rdos.
Speaker 4: All right, So then a big concept in a black
Speaker 4: hole is this idea of an event horizon. Now is
Speaker 4: the idea of an event horizon also dependent on relativity
Speaker 4: and quantum mechanics playing nicely with each other, or does
Speaker 4: relativity only break down at the center of a black
Speaker 4: like the edge of a black holes safe to talk about.
Speaker 1: The edge of a black hole is really only something
Speaker 1: we can talk about in general relativity. We don't know
Speaker 1: how quantum mechanics will modify that. It might make it
Speaker 1: so that there are no event horizons. These fuzzballs. For example,
Speaker 1: compact states of strings do not have event horizons at all,
Speaker 1: So it could be that there are no event horizons
Speaker 1: in the universe. So if we want to talk about this,
Speaker 1: really the only thing we can do is talk about
Speaker 1: what general relativity predicts, even though we're not exactly sure
Speaker 1: it's real.
Speaker 4: So then how do you define the event horizon?
Speaker 1: Then? Well, in general relativity, the event horizon is the
Speaker 1: point past which no information can escape, and that's something
Speaker 1: we can calculate in general relativity, and it depends on
Speaker 1: the mass of the object, also whether it's spinning, whether
Speaker 1: it has charged these kinds of things.
Speaker 4: And it's kind of a very special point in a
Speaker 4: black hole because that's the point at which not even
Speaker 4: information can escape.
Speaker 1: Right, Yeah, that's right.
Speaker 4: So sort of is the things we can know about
Speaker 4: the black hole.
Speaker 1: Yeah, you can't know anything that's going on inside the
Speaker 1: black hole, but you can measure some things about the
Speaker 1: black hole, like we know, for example, obviously you can
Speaker 1: measure the black hole's mass, you can measure its gravitational
Speaker 1: effects on things nearby. If you fly near a black hole,
Speaker 1: you're going to be drawn towards it because space is
Speaker 1: curved so the effect of the black hole exists outside
Speaker 1: the event horizon. You can sort of think of it
Speaker 1: as the event horizon itself having a property. The event
Speaker 1: horizon is there, it summarizes all the stuff that's inside
Speaker 1: of it. The mass of the event horizon or the
Speaker 1: black hole itself, affects space outside the event horizon. So
Speaker 1: you can definitely know that about the black hole, and
Speaker 1: you can know a couple of other details as well.
Speaker 4: Like the spin and also the charge of a black hole.
Speaker 1: Right, yeah, that's right. Those are the three things that
Speaker 1: general relativity says we can know about the black hole.
Speaker 1: That a black hole can also be spinning, right, Things
Speaker 1: that fall into a black hole, if they have angular momentum,
Speaker 1: they have to keep having angular momentum because in our universe,
Speaker 1: angular momentum is conserved. We're pretty sure. Same thing with
Speaker 1: electric charge. The universe strictly preserves electric charge. We've never
Speaker 1: seen that violated. You can create plus and minus particles together,
Speaker 1: but the overall charge of the universe has to be
Speaker 1: the same. And so if you drop an electron into
Speaker 1: a black hole, then the black hole has to have
Speaker 1: that charge because it can't just disappear from the universe.
Speaker 1: So mass, spin, and charge are the things you can
Speaker 1: know about a black hole from the outside. You can't
Speaker 1: know like the arrangement of charges or masses or spins
Speaker 1: or whatever inside the event horizon, but you don't have
Speaker 1: to in order to know the total mass or the
Speaker 1: total charge or the total spin from the outside.
Speaker 4: Can you tell if that black hole has a headache
Speaker 4: or something?
Speaker 1: Do black holes wear mood rings? I wish they did?
Speaker 1: Always black?
Speaker 4: Does that mean do they wear engagement rings? Well, you
Speaker 4: said charge, and I'm wondering. You know, that's the electromagnetic charge,
Speaker 4: but we also talk about it in this podcast. But
Speaker 4: other of charge in the universe, from the weak fours
Speaker 4: and the strong force. Can you know those other charges
Speaker 4: about a black hole? Can you know the color of
Speaker 4: a black hole?
Speaker 1: The color charges are really fun and tricky concept. It's
Speaker 1: not something we really understand very well because objects that
Speaker 1: have color don't ever exist in the universe. We only
Speaker 1: see neutral things like things that have color, like quarks,
Speaker 1: are always bound together into neutral states, something with the
Speaker 1: opposite color or the other two complementary colors, so they
Speaker 1: balance out because there's so much energy in the strong force,
Speaker 1: so things can't have their own color charge. You might
Speaker 1: want to imagine, like what happens if you have a
Speaker 1: quark anti quark pair and they're bound together, but one
Speaker 1: of them falls into the black hole. And now you're
Speaker 1: doing quantum gravity because we're talking about bound states of quarks,
Speaker 1: and one of them falls into the black hole and
Speaker 1: the other one doesn't. We don't know the answers to
Speaker 1: those questions because we don't have a theory of quantum gravity.
Speaker 4: But is it possible then maybe they also conserve those
Speaker 4: kinds of charges, and you would have to add that
Speaker 4: to the list of things you can know about a
Speaker 4: black hole.
Speaker 1: It is possible, And it's also possible that there are
Speaker 1: other kinds of charges in the universe we've never even discovered,
Speaker 1: Like dark matter could have all sorts of other forces.
Speaker 1: There could be like a dark version of electromagnetism with
Speaker 1: dark photons and dark charges, and black holes could have
Speaker 1: those dark charges as well.
Speaker 4: Wait were you saying black holes could have a hidden
Speaker 4: charge like a hidden fee?
Speaker 1: Exactly check your statements. People, When you.
Speaker 4: Buy a black hole, read the small print before you
Speaker 4: go into a black hole. All right, So then that's
Speaker 4: you know, we can tell it it has a gravitational
Speaker 4: field and an electric field. And now let's talk about
Speaker 4: a magnetic field of a black hole. What exactly is
Speaker 4: a magnetic field.
Speaker 1: Magnetic fields are really weird and awesome because they have
Speaker 1: lots of really interesting symmetries, symmetries that exist and also
Speaker 1: symmetries that are broken. Like in a lot of ways,
Speaker 1: the magnetic field is a perfect sister to the electric field,
Speaker 1: like light, for example, is a balance between electric fields
Speaker 1: and magnetic field. It's slashing perfectly back and forth between
Speaker 1: electric fields and magnetic fields and back. It really tells
Speaker 1: us that the distinction we make between electric fields and
Speaker 1: magnetic fields is a little bit arbitrary. It's just sort
Speaker 1: of like a historical thing. We drew a dotted line
Speaker 1: between these two things that are really part of a
Speaker 1: larger hole. But there also are important differences between electric
Speaker 1: fields and magnetic fields. For example, we have electric charges
Speaker 1: in the universe, but we don't have magnetic charges. Like
Speaker 1: an electron has a negative charge, you can just create
Speaker 1: a charged object by putting an electron on it, right,
Speaker 1: you can't do that with a magnetic field. There's nothing
Speaker 1: with a magnetic charge. If it existed, this would be
Speaker 1: called a magnetic monopole. It'd be like something with just
Speaker 1: a north or something with just a south. We've never
Speaker 1: seen one in the universe. Physicists don't know why. They
Speaker 1: think maybe they do exist out there or used to
Speaker 1: exist in the early universe. But you can't make a
Speaker 1: magnetic field the same way you make an electric field
Speaker 1: by just adding a magnetic charge to something.
Speaker 4: Well, maybe take a step back here, because you know,
Speaker 4: like I'm wondering, how do you even define what a
Speaker 4: magnetic field is? You know, like a gravitational field tells
Speaker 4: me how much a planet, for example, is pulling on
Speaker 4: me at any point in space, or an electric field
Speaker 4: tells me how much you know, an electron is repelling
Speaker 4: or pushing me or attracting me at any point in space.
Speaker 4: What does a magnetic field tell you?
Speaker 1: Yeah, great question. If there were magnetic monopoles, then they
Speaker 1: would be affected by magnetic fields the same way that
Speaker 1: electrical charges are affected by electric fields. They would be
Speaker 1: accelerated in one way or another. But those don't exist,
Speaker 1: so we can't use that to define magnetic fields.
Speaker 4: What do you mean, like when you talk about monopole,
Speaker 4: you mean like like an a mac that you have
Speaker 4: a North in the south.
Speaker 1: Right, in the magnets that we have in our universe,
Speaker 1: we have a north and the south. Those are dipole
Speaker 1: magnets that create a dipole magnetic field. There's a pair
Speaker 1: of a North in the south.
Speaker 4: So are you saying, like, if you had a North
Speaker 4: in front of me and I'm the south, it would
Speaker 4: tell me how much I'm attracted to the north or repel?
Speaker 1: Yeah, exactly. If you have huge magnet makes a magnetic field,
Speaker 1: and then if you put a North in that field,
Speaker 1: it would get pushed or pulled in one direction, and
Speaker 1: by the strength of that push or pull, you could
Speaker 1: measure the magnetic field.
Speaker 4: So there is some sort of charge, Yeah, exactly, Like
Speaker 4: what would determine how much of that push and pool?
Speaker 4: I feel?
Speaker 1: Well, the north and south are like the plus and minus. Right,
Speaker 1: North and South for a magnetic field are plus and
Speaker 1: minus for electric charges.
Speaker 4: And I can have like more of it or lessit.
Speaker 1: Yeah, exactly. You're going to bigger magnets or smaller magnets.
Speaker 1: You go to more norths and more souths. We've never
Speaker 1: seen a north on its own or a south on
Speaker 1: its own the way we have for electric charges. But
Speaker 1: in principle they could exist. Nothing in physics says that
Speaker 1: they can't. But we've only ever seen them paired together.
Speaker 4: I me mean like if something has a north, it
Speaker 4: also has a south.
Speaker 1: Yeah, and that's because those magnetic fields are actually made
Speaker 1: by electric charges. See, there's a very close connection between
Speaker 1: electricity and magnetism because if you take an electric charge
Speaker 1: like an electron, and you whiz it around in a circle,
Speaker 1: it makes a magnetic field. Any charge in motion, any
Speaker 1: charge with velocity, is going to make a magnetic field.
Speaker 1: And so every magnetic field that we ever created is
Speaker 1: actually made by moving electric charges.
Speaker 4: So if it's made by electric charges, it's made by
Speaker 4: the electric field. So why do we even call it
Speaker 4: its own field.
Speaker 1: Well, because it's made by electric charges doesn't mean it's
Speaker 1: an electric field, right, Yeah, we could just call this electromagnetism.
Speaker 1: You might be saying, Hey, the distinction between these two
Speaker 1: things seems arbitrary. Yes, it's totally arbitrary and historical. Because
Speaker 1: we discovered magnets and we discovered lightning. We call them
Speaker 1: two separate things. We build two theories and then boom
Speaker 1: one day, A brilliant Scottish dude realized they are actually
Speaker 1: two parts of the same thing. Now we call them electromagnetism,
Speaker 1: and you might say, let's just call it all electromagnetic fields. Cool,
Speaker 1: we can do that. But we do notice that there
Speaker 1: are two different charges that are described by this field,
Speaker 1: electric charges and magnetic charges, and only one seems to
Speaker 1: exist in the universe.
Speaker 4: M all right, So it's deeply connected to electricity, and
Speaker 4: some things just seem to have it or not. Right,
Speaker 4: things would charge seem to have it or not.
Speaker 1: Yeah, So every magnet we've ever seen in the universe
Speaker 1: is either a tiny little object that has quantum spin,
Speaker 1: like an electron has quantum spin, and that spin combined
Speaker 1: with its charge makes it a tiny little magnet. But
Speaker 1: because it's spinning, it makes two magnets. It makes a
Speaker 1: north and a south, so it's a little dipole magnet.
Speaker 1: Or you can have current like motion of electrons through
Speaker 1: a wire that makes a dipole magnet. So every magnetic
Speaker 1: field we've ever seen is made either by tiny little
Speaker 1: quantum particles having their own little magnetic fields. That's, for example,
Speaker 1: why your refrigerator magnet has a magnetic field. Has all
Speaker 1: these little particles with quantum spin oriented in the same
Speaker 1: way adding up or like an electromagnet, like an electric
Speaker 1: motor that comes because of current from electricity.
Speaker 4: Interesting and so I guess now the question is, since
Speaker 4: black holes can have an electric charge and also spin,
Speaker 4: can they also have a magnetic field. So let's dig
Speaker 4: into that. But first let's take a quick break.
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Speaker 4: All right, we're asking the question, can a black hole
Speaker 4: have a magnetic field? And what would happen if you
Speaker 4: put it on your fridge?
Speaker 1: You would eat everything in your fridge.
Speaker 4: There you go. You can blame that also on a
Speaker 4: black hole.
Speaker 1: I don't know who finished the pie? Honey, really, I
Speaker 1: don't Maybe it was a black hole in the middle
Speaker 1: of the night. Check the camera.
Speaker 4: Yeah, me, Rich, I'll put a black hole in the
Speaker 4: fridge there.
Speaker 1: The new black hole diet by Daniel.
Speaker 4: Yeah, I don't think that hounds work.
Speaker 1: I might need to workshop that a bit.
Speaker 4: Yeah, yeah, yeah, yeah, it's more like an excuse for
Speaker 4: a bad diet. But yeah, So black holes do they
Speaker 4: have magnating feels? Like literally, if you have a tiny one,
Speaker 4: would it stick to your fridge? That's kind of what
Speaker 4: we're asking here today.
Speaker 1: Right, right, Yeah, it's a really cool question, and the answer.
Speaker 4: Is it dependens Why am I not surprised?
Speaker 1: It depends on your reference frame, It depends on your velocity.
Speaker 1: Because we don't have magnetic monopoles. You can't just like
Speaker 1: throw a monopole into a black hole and have it
Speaker 1: have a magnetic field, like inherently. The only way for
Speaker 1: it to have a magnetic field is for to do
Speaker 1: what electrons do and electric currents do, which is have
Speaker 1: a charge and a spin. So take a black hole,
Speaker 1: spin it and charge it by shooting like a beam
Speaker 1: of electrons right near the event horizon, so it gets
Speaker 1: some angle momentum and it gets some charge. In that case,
Speaker 1: it will get a magnetic field because now it's spinning
Speaker 1: relative to you. So if you have like a magnetometer
Speaker 1: or something, you will measure a magnetic field near the event.
Speaker 4: Horizon, sort of in the same way that like an
Speaker 4: electron on its own can have an electric field because
Speaker 4: it's a charge, it does charge and it has spin.
Speaker 1: Yeah exactly right.
Speaker 4: Or like if you take a coil of wire and
Speaker 4: you spin a bunch of electrons that is those that's
Speaker 4: a charge spinning, which creates a magnetic field.
Speaker 1: Yeah exactly. You make a coil of wire and you
Speaker 1: run a current through it, that makes a magnetic field
Speaker 1: through the coil, right, Or simply if you just have
Speaker 1: a single line of wire, not a coil, and you
Speaker 1: run electrons through it, then you're going to get a
Speaker 1: magnetic field around the wire. But that magnetic field is
Speaker 1: frame dependent. It depends on the electrons moving relative to
Speaker 1: you through the wire. It only happens because the electrons
Speaker 1: are moving. It's charges in motion that give us magnetic fields.
Speaker 1: So if you have your black hole and it's spinning
Speaker 1: near you, you measure a magnetic field. Now you get
Speaker 1: in your ship and you start orbiting the black hole
Speaker 1: at exactly the same rate it's spinning, so that when
Speaker 1: you look out of your ship, the black hole is
Speaker 1: not spinning relative to you. Then it no longer has
Speaker 1: a magnetic field. The magnetic field is frame dependent.
Speaker 4: WHOA, meaning that the magnetic field disappears, or that you
Speaker 4: don't feel it.
Speaker 1: It's not there. I mean, we don't even know if
Speaker 1: fields are real anyway, but you can't measure it, and
Speaker 1: according to the physics, it isn't there. Like you do
Speaker 1: the calculation, there's a prediction of no magnetic field there.
Speaker 1: Then the thing is the field itself. You like to
Speaker 1: think of it as something physical. It's out there in
Speaker 1: the universe. But the distinction between electric fields and magnetic fields,
Speaker 1: like you were saying earlier, is a little bit arbitrary,
Speaker 1: and it turns out to depend on your frame of reference,
Speaker 1: and not just for black holes, also for the simple
Speaker 1: situation of electron going down a wire. If you jump
Speaker 1: in a car and you drive down the wire the
Speaker 1: same speed as the electrons, the electrons only have an
Speaker 1: electric field, but your buddy who's standing next to the wire,
Speaker 1: he measures the electrons going through the wire they have
Speaker 1: a velocity, he will also see a magnetic field. So
Speaker 1: magnetic fields are always frame dependent because they depend on velocity.
Speaker 4: Well, that's a little bit odd to me, I guess.
Speaker 4: So let's say have like a loop of wire mm hmm,
Speaker 4: and I run a current through it, And you're saying
Speaker 4: if I sit in the middle of it on a
Speaker 4: like an office chair, and I spin myself that I'm
Speaker 4: not going to feel the magnetic force.
Speaker 1: Yeah. If you spin at the same rate that those
Speaker 1: electrons are moving, so the electrons have no velocity relative
Speaker 1: to you, then you will feel no magnetic field. You'll
Speaker 1: sense no magnetic field. It's a tiny little bit more
Speaker 1: complicated there because now we're spinning, so we have acceleration
Speaker 1: and non inertial frames. So it's a little bit simpler
Speaker 1: in the straight line case. But yeah, the same thing applies.
Speaker 4: Right, I guess That's what I was trying to get at,
Speaker 4: is that you're saying it depends but it doesn't depend
Speaker 4: on like an inertial frame, which is sort of like
Speaker 4: the standard frames of the universe. It's like you have
Speaker 4: to make up this weird frame, right, like I would
Speaker 4: be feeling other things, I won't feel that electromagnetic field,
Speaker 4: but I'm going to feel, for example, this interpretal force.
Speaker 1: Yeah, exactly, And that's sort of the missing piece because
Speaker 1: you might be wondering, like, hold on a second. If
Speaker 1: I'm measuring a magnetic field and my friend is not
Speaker 1: measuring a magnetic field, how is that possible If dropped
Speaker 1: a monopole into that situation, would it get pushed or
Speaker 1: would it not get pushed? Right? There has to be
Speaker 1: like one answer to that question, and the answer is
Speaker 1: a little bit subtle but kind of beautiful. What relativity
Speaker 1: tells us is that the same laws of physics apply
Speaker 1: no matter what your reference frame, but the story they
Speaker 1: tell about why things happen doesn't have to agree. So
Speaker 1: in one scenario, your friend will say, oh, this magnetic
Speaker 1: field there and it helps push things around. The other
Speaker 1: person will say, no, there's no magnetic field there, but
Speaker 1: they will also see the electric field is a little
Speaker 1: bit different, and that will compensate. So one person will
Speaker 1: see a combination of electric and magnetic fields doing pushes
Speaker 1: and pulls on charge particles and magnetic monopoles. Somebody else
Speaker 1: will see only electric fields and no magnetic fields, but
Speaker 1: they'll actually predict the same motion for all the particles.
Speaker 1: They'll just have a different reason for why it happened.
Speaker 4: Right. It's sort of like if you're moving with the electricity,
Speaker 4: then you won't feel the forces of the electromagnetic field,
Speaker 4: but you'll have to push and spin yourself around the wire,
Speaker 4: which is sort of equivalent, I think, is what you're saying.
Speaker 1: Yeah, all the differences actually add up to give the
Speaker 1: same prediction, which is kind of amazing. And that's one
Speaker 1: of the beautiful things about relativity is that it shows
Speaker 1: you that all these pieces work together, because really the
Speaker 1: distinction between electricity and magnetism is a bit arbitrary and
Speaker 1: it's frame dependent. You know, people going in different speeds
Speaker 1: see electric fields or magnetic fields. But all the pieces
Speaker 1: work together so that even people in different reference frames,
Speaker 1: while they tell a different story about why things happen,
Speaker 1: like did you have a magnetic field or not, they
Speaker 1: will agree in these scenarios about what actually did happen.
Speaker 4: But I wonder if you can just can you just
Speaker 4: say the same thing about everything in the universe, you know,
Speaker 4: like you could also make gravity disappear if you move
Speaker 4: with the gravity, right, or you can make electric charge
Speaker 4: disappear if you move with the charges.
Speaker 1: Not everything in the universe is frame dependent. For example,
Speaker 1: black holes are not. If there's a black hole, then
Speaker 1: everybody agrees there's a black hole. You can't like boost
Speaker 1: yourself into some frame in which there is no black hole.
Speaker 1: This is why, for example, you can't make a black
Speaker 1: hole just by going really really fast. You might think, oh,
Speaker 1: black holes are actually happen when you have a lot
Speaker 1: of energy, not just mass. So why can't I make
Speaker 1: a black hole by taking a particle and zooming it
Speaker 1: to really high speeds because that would make a frame
Speaker 1: dependent black hole, which doesn't exist in our universe. So
Speaker 1: there are some things that are invariant no matter what
Speaker 1: frame you're in, inertial or not. But yeah, there are
Speaker 1: a lot of things in the universe that are frame dependent,
Speaker 1: I think more than people suspect, right.
Speaker 4: I wonder if the analogy is sort of like, you know,
Speaker 4: if you jump out of an airplane, you're falling towards Earth,
Speaker 4: you can tell that there's a planet there blow you right,
Speaker 4: Like to you, it's going to feel like you're floating
Speaker 4: in space as you plummet to your death.
Speaker 1: Yeah, that's right. In that scenario, you're actually in freefall,
Speaker 1: you're not doing any accelerating. It's the planet that's accelerating
Speaker 1: towards you. The surface of the planet is accelerating towards you.
Speaker 1: If you take out a gravitometer or an accelerometer in
Speaker 1: that scenario, you'll measure no acceleration. So you need to
Speaker 1: look out the window to see a planet rushing towards
Speaker 1: you to discover that your life span is going to
Speaker 1: be very short.
Speaker 4: Right, So in that way, sort of gravity is also
Speaker 4: a reference dependent, right, I can make it disappear if
Speaker 4: I jump out of an airplane.
Speaker 1: Lots of gravitational effects are frame dependent. Yes, there are
Speaker 1: some things that are frame independent, like the exist instance
Speaker 1: of a black hole, but a lot of things are
Speaker 1: frame dependent, absolutely, And you're right that this story applies
Speaker 1: very broadly. There's lots of situations in physics where people
Speaker 1: will disagree about why things happened, even if they apply
Speaker 1: the same rules and they might agree about what happened,
Speaker 1: they'll tell a different story about how that happened or
Speaker 1: why that happened, even though the outcome is the same.
Speaker 4: But I guess if you stick to what most people
Speaker 4: think is normal, which is like an inertial frame or
Speaker 4: you know, not spin around at a crazy speed in
Speaker 4: an office chair. Then you would say that a black
Speaker 4: hole does have a magnetic field.
Speaker 1: Yeah exactly, and it's not special, right. A black hole
Speaker 1: has a magnetic field, and exactly the same way a
Speaker 1: coil of wire has a magnetic field. You got charge
Speaker 1: in there, you got spin, so you're moving charges, so
Speaker 1: you get a magnetic field. The magnetic field of a
Speaker 1: black hole is not deficient in any way compared to
Speaker 1: the magnetic field from an electromagnetic motor, for example.
Speaker 4: And I guess what that means is that if I
Speaker 4: take a compass and I hold it up close to
Speaker 4: a black hole, I'm going to see it point in
Speaker 4: a specific direction, right, just like it points to a
Speaker 4: specific direction here on Earth.
Speaker 1: Yeah, exactly, a black hole have a magnetic field the
Speaker 1: way the Earth does. And we think the Earth's magnetic
Speaker 1: field probably comes from convection and flow of stuff inside
Speaker 1: the Earth, though we don't totally understand. And so yeah,
Speaker 1: you could use a compass to navigate near a magnetic
Speaker 1: black hole.
Speaker 4: So I mean black holes have a north and south pole.
Speaker 1: Yeah, exactly. They have a north and south pole for
Speaker 1: their spin as well, right, A black hole that doesn't
Speaker 1: spin is spherically symmetric, but a spinning black hole has
Speaker 1: broken that symmetry because there has to be some axis
Speaker 1: around which it's spinning. So that gives it a north
Speaker 1: and south spin black hole, and because that spin is
Speaker 1: what generates the magnetic field, it also then has a
Speaker 1: north and south magnetic pole.
Speaker 4: Whoa, And so if I have a tiny spinning black hole,
Speaker 4: then it would be attracted to my fridge door, right.
Speaker 1: Yes, it would be attracted to your fridge door. Even
Speaker 1: if it's was too weak to hold it there, it's
Speaker 1: magnetic field might be powerful enough, because remember, magnetic fields
Speaker 1: are much more powerful than gravity. So you make a
Speaker 1: tiny black hole out of a few electrons, it might
Speaker 1: not have very strong gravity, but the magnetic fields could
Speaker 1: already be quite powerful.
Speaker 4: Yeah, it's interesting to think that a black hole has
Speaker 4: a north and south pole. I hear the north pole
Speaker 4: of a black hole where all the dark elves hang out.
Speaker 1: Are they making dark presents for dark Christmas?
Speaker 4: And now they're just making a bunch of coal presents
Speaker 4: for everyone? It's the opposite. It's the opposite. Can you
Speaker 4: measure the magnetic field of a black hole from a distance.
Speaker 1: In principle, if you were near the black hole, you
Speaker 1: can do what we describe, which is used the compass.
Speaker 1: We can't go near black holes, unfortunately, but we can
Speaker 1: see the effect of black holes on nearby particles. Right.
Speaker 1: Black holes are almost never on their own. They formed
Speaker 1: because they're in the middle of some dense blob of
Speaker 1: matter they've been gobbling, so usually there's a lot of
Speaker 1: stuff around them. And if you trace the path of
Speaker 1: the charged particles near the black hole, then you can
Speaker 1: measure something about its magnetic field. But those particles also
Speaker 1: will generate a magnetic field, so teasing those two things
Speaker 1: apart is quite tricky.
Speaker 4: Hmmm. Sort of like if you threw a bunch of
Speaker 4: iron filings fillings filings at a black hole, they would
Speaker 4: form a pattern around the black hole, and that would
Speaker 4: tell you, oh, that's the magnetic feel, that's where the
Speaker 4: north pole is pointing.
Speaker 1: Yeah, it's filings. If it's little pieces of shaved iron,
Speaker 1: it's fillings. If they came from people's teeth, which were.
Speaker 12: You imagine.
Speaker 4: Both, I guess, I guess both would work.
Speaker 1: I guess if you go near a black hole, it
Speaker 1: might pull out your iron fillings.
Speaker 4: What do you file some fillings?
Speaker 1: I'm going to find a complaint with the black Hole
Speaker 1: Division if.
Speaker 4: That happens another full I think they filled up already. Yeah,
Speaker 4: all right, So then could we measure it potentially from earth?
Speaker 4: Like if we you know, we have these pictures now
Speaker 4: of what we think are black holes, could we measure
Speaker 4: their magnetic feel from here?
Speaker 1: Absolutely we can and we have we have.
Speaker 4: All right, well let's talk about that, but firk, let's
Speaker 4: take another quick break.
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Speaker 4: All Right, we're talking about the polarity of a black hole.
Speaker 4: They're very polarizing black holes. Some people love them, some
Speaker 4: people really love them.
Speaker 1: Those are your only two choices.
Speaker 4: Yeah, you either either love it or you don't love it.
Speaker 1: Fill out this survey or what take your iron feelings?
Speaker 4: Well, we talked about how black hole has a magnetic field,
Speaker 4: but it's sort of not new information, right, Like it's
Speaker 4: it's the product of its charge and it's been so
Speaker 4: it's not like it has a fourth property that you
Speaker 4: can find out about it. It's sort of a derivative
Speaker 4: of its charge and spin.
Speaker 1: Yeah, exactly, not derivative in the calculus sense, but derivative
Speaker 1: in the like, oh, you just copied that sense. It
Speaker 1: comes out of the other properties. It's not a core
Speaker 1: basic quantity of a black hole itself unless the black
Speaker 1: hole had a magnetic monopole in it, and then it
Speaker 1: would be a core property. But you're right, it sort
Speaker 1: of emerges from the other properties.
Speaker 4: What do you mean if a black hole eight a monopole.
Speaker 1: If a black hole at a monopole, it would be
Speaker 1: something we call a dionic black hole, and it would
Speaker 1: have its own monopole magnetic field, just like the monopole
Speaker 1: that fell into it.
Speaker 4: Right, How would it ever eat a monopole?
Speaker 1: Number one? A monopole would have to exist in the universe,
Speaker 1: and we don't know that they do, but they might,
Speaker 1: and then it would have to go near a black
Speaker 1: hole and then gobble gobble.
Speaker 4: Mm could a black hole split a dipole into a
Speaker 4: two monopoles, like it eats one and it shoots off
Speaker 4: the other one.
Speaker 1: That would be an awesome feature of quantum gravity. Currently
Speaker 1: in our predictions, know, you can't split a dipole because like,
Speaker 1: where does that come from? It comes from the electron spinning,
Speaker 1: So you're gonna split the electron somehow, So we don't
Speaker 1: know how to do that.
Speaker 4: I don't know in general, can you tell a black
Speaker 4: hole what it can or can't do?
Speaker 1: If black holes are listening to this podcast, I apologize
Speaker 1: for my presumptuousness.
Speaker 4: They're gonna come after your fridge watch out, all right. Well,
Speaker 4: so what can we see of a black hole or
Speaker 4: what have we seen?
Speaker 1: So we've seen that black holes have a huge effect
Speaker 1: on nearby matter. They don't just suck stuff in, they
Speaker 1: also shunt stuff away from themselves. Their magnetic fields can
Speaker 1: be so strong that in falling particles can actually follow
Speaker 1: those magnetic fields and then escape the black hole, you know,
Speaker 1: the same way that like we've seen these aurora, because
Speaker 1: charge particles falling in towards the Earth end up spiraling
Speaker 1: around our magnetic fields and then end up in the
Speaker 1: North Pole. It's also possible when particles are falling into
Speaker 1: towards a black hole. Basically the same thing happens, but
Speaker 1: they get so much speed that they then escape the
Speaker 1: grip of the black hole and they shoot out up
Speaker 1: and down the north and South poles. And we see
Speaker 1: these enormous jets from black holes. You see galaxies with
Speaker 1: super massive black holes at their center, and then these
Speaker 1: huge jets extending thousands of light years up and down,
Speaker 1: sort of above and below the plane of the galaxy.
Speaker 1: Those are jets from the central black hole, and they're
Speaker 1: powered by its magnetic field.
Speaker 4: Whoa wait, wait, wait, wait, hold on, it's not stuff
Speaker 4: coming out of the black hole, is it right? It's
Speaker 4: not right, because nothing can escape a black hole.
Speaker 1: It's not something escaping a black hole. It's something having
Speaker 1: a near miss. It's like fell in. And then a
Speaker 1: magnetic field outside the black hole, the same way we
Speaker 1: have on a magnetic field outside the atmosphere of the Earth.
Speaker 1: The magnetic field that's outside the black hole guides those
Speaker 1: particles towards the north and then they escape, but they
Speaker 1: never went inside the event horizon.
Speaker 4: I see now. I wonder if that means that looks
Speaker 4: different to like an electron than it does to a proton. Potentially.
Speaker 1: They definitely do look a little bit different. I mean,
Speaker 1: a proton and an electron have different charges, and so
Speaker 1: they're affected differently by those magnetic fields. But all these
Speaker 1: particles do see the same event horizon. The event horizon
Speaker 1: is the event horizon is the event horizon.
Speaker 4: But wouldn't they're like their paths near a black hole
Speaker 4: be different, in which case the point at which they
Speaker 4: would definitely fall in is different.
Speaker 1: Yeah, the paths near the event horizon are different because
Speaker 1: they are affected by magnetic fields differently, and their masses
Speaker 1: are different, et cetera, and their charges are different. But
Speaker 1: the event horizon is still just the event horizon. That's
Speaker 1: a feature of the curvature of space. It's not an
Speaker 1: issue of like the forces on the particles. Remember, it's
Speaker 1: a product of the black hole itself.
Speaker 4: And that's just from the mgnet field of the black
Speaker 4: hole itself. You mentioned earlier that the stuff swirling around
Speaker 4: it can also make magnet fields.
Speaker 1: Yeah, exactly. There's huge accretion disks surrounding most black holes,
Speaker 1: especially the ones at the center of galaxies that have
Speaker 1: been feeding on gas and dust, and so there's a
Speaker 1: lot of stuff that has fallen close to the black
Speaker 1: hole and is still in orbit around it. Remember, things,
Speaker 1: unless they fall directly towards the center of the black
Speaker 1: hole or towards the event horizon, they're still going to
Speaker 1: have some angular momentum. You can orbit a black hole
Speaker 1: the same way the Moon orbits the Earth. Black Holes
Speaker 1: are not like literally sucking things in. They're just gravity, right,
Speaker 1: They're just curvature of space. You could in principle, orbit
Speaker 1: a black hole forever and never fall in. But if
Speaker 1: you're in this big disc of gas and dust, you're
Speaker 1: also going to have friction. You're going to bump up
Speaker 1: against each other, and some stuff is going to end
Speaker 1: up falling in. But before it does, you know this
Speaker 1: huge disc of gas and tidal forces are heating it up,
Speaker 1: so it's really hot and energetic and glowing in the
Speaker 1: X ray. And because it's a lot of charged particles
Speaker 1: swirling around, it has its own very strong magnetic field.
Speaker 4: Like it adds to the black holes. Is a magnetic
Speaker 4: field or it cancels it? Or how does it interact
Speaker 4: with the black holes magnetic field itself?
Speaker 1: Yeah, great question, and that's essentially the cutting edge of
Speaker 1: our research right now. It's like, what do the black
Speaker 1: hole magnetic fields look like. What are the magnetic fields
Speaker 1: coming from the disc look like. It depends a lot
Speaker 1: on how calm or how turbulent that accretion disc is. Like,
Speaker 1: if everything is flowing very nicely, like Saturn's rings, then
Speaker 1: all those magnetic fields will add up very nicely and
Speaker 1: they'll all contribute in the same direction. But if it's
Speaker 1: sort of chaotic, like a big storm, then the magnetic
Speaker 1: fields generated by those particles might cancel each other out.
Speaker 1: We also don't really know how much of the magnetic
Speaker 1: field is coming from the disc and how much is
Speaker 1: coming from the black hole itself. We can't separate those
Speaker 1: two things very easily.
Speaker 4: We can't because it's just too complicated.
Speaker 1: Yeah, we don't really understand how much magnetic field there
Speaker 1: is coming from the accretion disc because it's not something
Speaker 1: we've modeled very well. We have lots of competing theories
Speaker 1: about what the accretion disc looks like, and so to
Speaker 1: separate out the black holes magnetic field, you have to
Speaker 1: understand the rest of the magnetic field very well. But
Speaker 1: we've tried to do that. We've been able to take
Speaker 1: these images of the event horizon or images of the
Speaker 1: stuff near the event horizon, and recent pictures of that
Speaker 1: have used some clever tricks to try to understand what
Speaker 1: the magnetic fields look like near the black hole.
Speaker 4: WHOA, how can you do that? Well, first of all,
Speaker 4: you can't really see the event horizon, right, You only
Speaker 4: see the shadow of the black hole, which is different.
Speaker 1: Yeah, that's exactly right. We're just not seeing photons from
Speaker 1: the event horizon or anywhere near it in a way
Speaker 1: that lines up really really well with predictions of general relativity.
Speaker 1: And so that's an indirect piece of evidence for black holes.
Speaker 1: Another frustrating the indirect piece of evidence. But we can
Speaker 1: see the stuff the accretion disc nearby it. That's why
Speaker 1: these photos look sort of like a big crispy cream donut.
Speaker 5: Right.
Speaker 1: You have the hot gas glowing near the accretion disk,
Speaker 1: and those photons that come from the gas that are
Speaker 1: emitted from these high speed charged particles, they can give
Speaker 1: us some clues about the magnetic field that they're in.
Speaker 1: Because the magnetic fields will polarize these photons, it changes
Speaker 1: how the photons wiggle, like are they're wiggling this way
Speaker 1: or they're wiggling that way. And if the magnetic fields
Speaker 1: are all nicely organized, then the polarization of those photons
Speaker 1: will be nicely organized, and if the magnetic fields are
Speaker 1: all a big hot mess, then the polarizations will all
Speaker 1: be scrambled. So they recently reanalyzed the image of the
Speaker 1: black hole at the heart of them eighty seven galaxy
Speaker 1: to try to measure the polarization of these photons, not
Speaker 1: just like where's it bright and where's it dim, but
Speaker 1: in which direction of those photons wiggling, And that gave
Speaker 1: them some clues about what might be happening in the
Speaker 1: accretion disc.
Speaker 4: WHOA, which would then sort of tell you what's going on, right.
Speaker 1: Yeah, exactly, and it's really fun. They had two models
Speaker 1: of black hole accretion disc magnetic fields. One of them
Speaker 1: was called sane stable and normal evolution s an E,
Speaker 1: and the other one is called mad magnetically arrested disc.
Speaker 1: So it was a big competition between the sane and
Speaker 1: the mad groups.
Speaker 4: They're like, no, I'm saying, no, you're mad.
Speaker 1: I mean, you've heard of crazy astronomical acronyms before, but
Speaker 1: this is like dueling crazy acronyms. I'm impressed by their coordination.
Speaker 11: Yeah.
Speaker 4: So each one of these was invented by a different group.
Speaker 1: Yeah, exactly, the like competing theories for how the accretion
Speaker 1: disc will come together, And basically the difference between them
Speaker 1: is how turbulent is it and how coherent is it?
Speaker 1: You know, is it basically all scrambled and you don't
Speaker 1: get a strong magnetic field or is it kind of
Speaker 1: coherent and well ordered, in which case you do get
Speaker 1: a stronger build up of the magnetic fields from the
Speaker 1: accretion disc.
Speaker 4: Right right? Or are they all just crazy physicists.
Speaker 1: Yeah, And so for a long time, people thought that
Speaker 1: the same scenario was more natural, sort of weaker fields
Speaker 1: because everything would be sort of more scrambled. But what
Speaker 1: they measured is more consistent with the mad scenario. That
Speaker 1: things are like nicely organized, so they all add up
Speaker 1: to give more powerful magnetic fields than people suspected.
Speaker 4: Meaning that the black hole is not as chaotic as
Speaker 4: we thought it was.
Speaker 1: Yeah, it turns out to be a little bit tidy.
Speaker 4: Wait, the mad scenario is more sane than the same scenario.
Speaker 1: The mad scenario is more like our universe. It's the
Speaker 1: one where things are better organized.
Speaker 4: Yeah, it sounds like physicists are just trying to drive
Speaker 4: us mad. All right, Well, I think that sort of
Speaker 4: answers the question black holes do have magnetic fields. I
Speaker 4: mean they have spin in charge, which means they'd have
Speaker 4: magnetic fields. You can take a black holes, stick it
Speaker 4: on your fridge, you can use it to mess up
Speaker 4: your friend's compass, but measuring it might be a little
Speaker 4: bit tricky because it's so far away, and there's also
Speaker 4: these weird physics and dynamics going on or around outside
Speaker 4: of it.
Speaker 1: That's right. We can't know what's going on inside a
Speaker 1: black hole, but magnetic fields give us a pretty good
Speaker 1: clue as to what's going on near a black hole,
Speaker 1: which one day might help us gain some clues about
Speaker 1: what's going on past the event horizon.
Speaker 4: Whoa do you think we can use magnets to see
Speaker 4: what's inside of a black Hole's kind of what you're saying.
Speaker 1: Well, in general relative we definitely cannot, But in a
Speaker 1: quantum version with quantum gravity, there could be some correlation
Speaker 1: between the information on the surface of the event horizon
Speaker 1: itself and what's going on inside. There could be some features,
Speaker 1: some hair to the black hole, and that could affect,
Speaker 1: for example, the radiation and the magnetic fields. And so eventually,
Speaker 1: if we get detailed enough information and better theories of
Speaker 1: quantum gravity, we might be able to see what's inside them.
Speaker 4: That would be insane.
Speaker 1: I wouldn't be mad about it.
Speaker 4: Well, you know what they say, wearing magnets can really
Speaker 4: help you out.
Speaker 1: Do they say that that sounds like pseudoscience?
Speaker 4: Well, honestly, all this black holes also sounds a little
Speaker 4: bit like pseudoscience.
Speaker 1: It's definitely not the final word on how any of
Speaker 1: this stuff works. Is just science in progress.
Speaker 4: I see, it's not pseudoscience. It's pre science.
Speaker 1: Everything is pre science.
Speaker 4: Nothing is the protocience. That sounds better protoscience.
Speaker 1: Science in action. About that?
Speaker 4: That's right. You don't want to be a pre scientist,
Speaker 4: all right? Well, another reminder about the incredible mysteries out
Speaker 4: there in the universe and how they're staring us right
Speaker 4: in our telescopes. You can see them, you can point telescopes,
Speaker 4: you can measure things about them, but all you see
Speaker 4: is pure unknowns.
Speaker 1: And their magnetic personalities.
Speaker 4: That's right, the riz. Well, we hope you enjoyed that.
Speaker 4: Thanks for joining us, See you next time.
Speaker 1: For more science and curiosity. Come find us on social media,
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