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