Daniel and Kelly’s Extraordinary Universe - Listener Questions 45: Gravity and Black holes

Episode Date: November 28, 2023

Daniel and Jorge venture to the edge of human knowledge about black holes, gravity and magnetic fields.See omnystudio.com/listener for privacy information.

This is an I-Heart podcast. Your entire identity has been fabricated. Your beloved brother goes missing without a trace. You discover the depths of your mother's illness. I'm Danny Shapiro. And these are just a few of the powerful stories I'll be mining on our upcoming 12th season of Family Secrets. We continue to be moved and inspired by our guests

and their courageously told stories. Listen to Family Secrets Season 12, on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast. Here's a clip from an upcoming conversation about how to be a better you. When you think about emotion regulation, you're not going to choose an adaptive strategy which is more effortful to use unless you think there's a good outcome. Avoidance is easier. Ignoring is easier.

Denials easier. Complex problem solving takes effort. Listen to the psychology podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Every case that is a cold case that has DNA. Right now in a backlog will be identified in our lifetime. On the new podcast, America's Crime Lab, every case has a story to tell. And the DNA holds the truth. He never thought he was going to get caught. And I just looked at my computer screen.

I was just like, ah, gotcha. This technology is already solving so many cases. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. It's important that we just reassure people that they're not alone, and there is help out there. The Good Stuff podcast, Season 2, takes a deep look into One Tribe Foundation, a non-profit fighting suicide in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission. One Tribe, save my life twice. Welcome to Season 2 of the Good Stuff.

Listen to the Good Stuff podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Hey, Daniel, do you ever get tired of answering questions from listeners? Not so far, but, you know, ask me again in another five years. What's going to happen in five years? I might have a different answer. You sometimes get the same questions over and over. You know, there are a lot of common themes in these questions. That's true.

And do you have like pre-pre-prepared answers ready to go? You can't really do that because every question's a little bit different. And for me, the fun part is figuring out like what somebody misunderstood to lead to their confusion and helping them unravel that. So you can't just like program an AI to answer questions for you? Kind of like they do now with like customer service lines. You could definitely program an AI to answer questions. but it would generate nonsense. Sometimes isn't the answer nonsense in physics,

especially quantum mechanics? The most amazing thing about the universe is that it doesn't seem to be nonsense. It seems to actually make sense. So far, maybe I'll ask you again in five years. Maybe in five years you'll have replaced me with an AI. Maybe in five years will all be replaced by AIs, and only AIs will be listening to this.

But maybe not. I-I. Hi, I'm Jorge. I'm a cartoonist and the author of Oliver's Great Big Universe. Hi, I'm Daniel. I'm a professor of physics, and I do experiments at CERN, and I don't think that I'm an AI. But you could be, are you saying? We never know philosophically where our consciousness comes from. could all actually be AIs. Yeah, we could.

I guess there's several possibilities, right? Like we could be in a simulation or something and we could all be AIs. Or, you know, if the people where religions are right, then technically we are kind of artificial intelligence because we were made by another intelligence. Yeah, it certainly could be. Or we could all just be Cylons, you know, thinking we're humans programmed to think we are humans, but silicon underneath. Yeah, on a TV show that sadly got canceled.

That was a great. show. But anyways, welcome to our podcast, Daniel and Jorge Explain the Universe, a production of iHeartRadio. In which we use our consciousness simulated or not, artificial or not, to try to understand the nature of the universe. Whether it's real or not, and whether our subjective experience is organic or not, we think it's worthwhile to try to understand what's out there, to try to make it all work in our minds, to ask questions and seek answers. And that's what this podcast is all about. Yeah, sometimes I feel like my intelligence is simulated. Like, I'm just pretending to be intelligent?

What's the difference between being intelligent and effectively pretending? Oh, good point. That's an intelligent answer. And I don't mean that in a fake sense. I mean that in an unartificial sense. Sometimes I feel like the most important function I serve for my students is asking them dumb questions about their research. And often I see it spark good ideas. They're like, well, that doesn't make any sense, but it gives me a good idea about something I could do.

So you're incentivized to ask dumb questions? I just simulate knowing what I'm doing and somehow the people around me get stuff done. It sounds like you could program an AI to ask dumb questions and then you don't have to do anything. Yeah, exactly. I think often I could be replaced by a cardboard cut out of myself. Just having students explain what they're doing to me helps them understand what they're doing wrong. Yeah, and it has pre-programmed answers like or questions like, huh, that's really interesting. Have you checked the error bars?

are you sure about those assumptions that's it just have it on loop people come in they press a button you're in a Caribbean island doing nothing you know or they just pull a string behind me or I'm just like a stuffed teddy bear there you go maybe we should actually make merch stuffed versions of us they pull the back of you and you go hmm and they pull the back of me and it goes chuckle yeah perfect and then someone could just replicate the entire podcast without us there just pull strings you could build a robot to pull the strings and we'd be done oh man but I guess you need someone to press the record button I have students who can do that

perfect but yeah it is a pretty interesting and amazing universe whether it's simulated or not or whether we are simulated or not and whether we are artificial or not we have questions about what's going on in this universe about how it all works scientists have questions that are busy doing experiments to try to get answers but we're not the only ones with questions. Everybody out there asks questions about the nature of the universe since the first people have looked up in the night sky

and wondered what all those twinkling lights were. Being curious is just part of being human and looking for answers is doing science, whether or not you're getting paid for it. Yeah, it's not just the job of scientists to ask questions about the universe. It's your job. It's everybody's job. To look at the cosmos and wonder why it's all there and how it all works.

One of our goals on this podcast is to find answers for you, but also to stimulate your questions to get you to think about the things you don't understand, to hear what we're saying and then try to click it together in your mind. And when it doesn't quite fit, we'd love if you reached out to us

to ask us your questions about the universe. We'll always answer them to questions at danielandhorpe.com. Yeah, everybody has questions, kids, adults, and everyone in between and sometimes we'd like to answer those questions here on the podcast. We absolutely do.

So feel free to write to us and ask us your questions. Sometimes I'll get a question that I think, hmm, I bet other people want to know the answer to that. And so we'll answer it here on the podcast. Do you sometimes think, oh, nobody else wants to know the answer to that? Do you have the opposite feeling? I do sometimes get personal questions about people's life path and stuff like that. And so, yeah, that's individualized answers that don't need to be on the podcast.

Do you ever get a question that it's like so complicated you don't think anyone else would be interested? I get a lot of people sending me their personal theories of the universe. And I'm not sure anybody else really wants to read those hundreds of pages written by retired engineers. But what if they're right? Oh, I see. But then it becomes your theory. And then you want everyone to read about it. No, I read those theories and give them critiques.

And if there was something to it, then yeah, you'd hear about it. Well, as Daniel said, we'd like to answer questions here on the podcast. And so on today's episode, we'll be tackling. This are questions. Number 45. Gravity and black holes. That's the theme of the questions today. Gravity and black holes.

Yeah, black holes and gravity seem to be on people's minds the week that these questions came in. Yeah, and so we have some great questions here about famous physics experiments, the event horizons of black holes, and what happened since the Big Bang? Pretty deep questions, deep in time and space. So we'll just jump right in. Our first question comes from Sean, from Canada. Hey, Daniel and Jorge, this is Sean calling from Canada. I have a question about the observer effect.

What would happen if the observer was on the inside of the event horizon of a black hole and the experiment being observed was on the outside of the event horizon of a black hole? Would it know that it's being observed? Would the waves collapse and all that stuff? Yeah, let me know. Thanks. Interesting question. I guess the gist of it is that what happens if you're inside of a black hole, can't tell what's going on outside of the black hole? Yeah, there's a lot of really interesting stuff going on in this question.

It's about black holes. It's about quantum mechanics. It's about all that kind of stuff. Of course, inside a black hole, you can see things that are happening outside a black hole, right? A black hole is where information cannot escape from, but new information can always arrive. Like photons can fall into black holes. And if you were inside a black hole, those photons could still reach you. So from within a black hole, you can observe things happening in the outside of the universe. But I love this question because it touches on this complicated quantum mechanical issue of observing things, changing them.

Often in quantum mechanics, we say that observation changes an experiment. And he's wondering, if you're doing that observation while you're inside a black hole, can you change an experiment that's outside a black hole? Because I guess in quantum mechanics, once you observe something, it changes the wave function of it, right? Exactly. And this is something in quantum mechanics that's not very, very well understood. So often when you push the boundaries and come up with crazy thought

experiments, the answer is we don't know or we have no idea because actually our theory of quantum mechanics doesn't make any sense. So it's probably important to like sum up what is the observer effect in quantum mechanics, what we're talking about here. But I guess maybe I have many more basic questions about this setup here. So like the observer, you are inside the black hole and this is I guess assuming you survive going into the black hole, right? Yeah, I assume you survive if you're observing the experiment. Like you have a camera and you take it inside of the black hole

and you somehow survive, you would still be getting information from outside the black hole. But you wouldn't, I guess, see like the whole universe. Like I think we've talked about this before. The whole universe would look like one pinpoint to you. That's right.

All light that arrives on the black hole would arrive to you and just one point. So like the entire event horizon would be collapsed to a single point in your vision. The rest, every other direction from your perspective, would be towards the singular. because remember that black holes are curvatures of space time.

And so changing the way space is organized inside the black hole. Okay. So now the scenario is that there's maybe like an electron just outside the black hole and it's about to veer to the right or to the left depending on some magnetic field, right? Because it has some quantum uncertainty about that. And then the question is, could you see that? Like could the photon from that electron reach you? Would it reach you? So a photon from that electron definitely could reach you.

electron gives off a photon that can fall in the black hole and then it can reach you inside the black hole. Absolutely. What about like time? Doesn't time slow down at the surface of a black hole or doesn't it stand still? So time does get slowed down by gravity. Places that have strong curvature feel time going more slowly. So for example, if you're near a black hole and you're looking at the rest of the universe, your time is going more slowly. You see the rest of the universe going more quickly. Or if you're watching somebody fall into a black hole, you see their time slow down. So from the outside, you can't actually see somebody fall into a black hole. You're right. If time slows down so much as they approach the event horizon that it's not until like time equals

infinity that they actually fall in from your perspective. But if you're the person falling in to the event horizon, then you just fall past the event horizon. You don't notice these effects. The electron, which is fly right in from your perspective inside the black hole. Inside the black hole, exactly. But really, outside of the black hole, it wouldn't happen for infinity. From the point of view of a distant observer, watching you fall in, it wouldn't happen until time equals infinity or until something else falls

in the black hole and grows it so that it encompasses you. That's the reason that like real black holes in the universe can actually grow, that they don't have to wait until time equals infinity for things to fall in because there's a whole series of things falling in. Each one grows the event horizon for the previous one. Okay, so you can get information from inside the black hole. And I guess you're not really watching the electron. You're just watching whether it veers to the right or to the left, right? Something detects the electron going right or left or something. Yeah, I think the setup he's interested in is like an electron is in a superposition of two possible states. Like does it go left or right?

And somehow you maybe use a photon to detect left versus right. And that photon falls into the black hole. And he's wondering if observing that photon inside the black hole collapses the way functioning experiment outside the black hole. Right. Because I guess since you're inside the black hole, there's like no way for the electron to know. whether you saw it or not. Exactly. That's where this cool quantum mechanics black hole paradox comes in.

Because if you take away the black hole, we have the sort of classic observer effect, that the electron can still be 50% chance left, 50% chance right, until its wave function is collapsed. When does the wave function collapse? Well, nobody really knows the answer to that,

but one ridiculous but standard description of quantum mechanics says that the electron's wave function is collapsed when it's observed by a classical object, like a person or a big detector or something. So the photon can bounce off of the electron without collapsing its wave function because it's still a quantum object.

But then when that photon carrying that information hits a screen or a detector or an eyeball or something like that, a classical object, it collapses the whole wave function. And that's when the electron decided, okay, I went left or okay, I went right. But does it collapse only for the observer or for the entire universe?

Like if you observe it, but I don't know what you observe, is it still a quantum object to me? Oh, great question. And the answer to that depends on your quantum mechanics philosophy. So in standard quantum mechanics, Copenhagen interpretation, it collapses for everybody. And it collapses instantly across space and time. Those two objects are entangled.

The photon and the electron are quantum mechanically entangled, meaning that they share a fate. They're connected to each other. If the electron goes left, then the photon looks a certain way. And if electron goes right, the photon looks another way. So in your standard interpretation, as soon as you observe the photon, that collapses the electron for everybody. But in other interpretations of quantum mechanics, like Carlo Revelli's relational quantum mechanics, then it only collapses for the person doing the observation. One person can collapse it for themselves.

Somebody else could have it be uncollapsed. And a third person can collapse it in another way. So there's different theories of quantum mechanics. In the standard one that people typically think about, and we complain about it a lot because it doesn't make much sense, it's collapsed for everybody. It also sort of depends on the idea of Schrodinger's box, right? Doesn't it? Like, if I wrap a box around you, the observer and the electron, like it's still a quantum object to me,

no matter whose interpretation I think about, does it? The cat is both alive and dead, and you saw it and not saw it at the same time. Yeah, that is the paradox raised by Schrodinger's box, that things can be unobserved, but still be classical. So in the standard Copenhagen interpretation, we say classical objects collapse the wave function and quantum objects do not.

The problem with the standard quantum mechanics is that there's no different. of what's a classical and what's a quantum object. So it's sort of a useless distinction. But in the standard interpretation, then you would still have collapsed the wave function because you'd be a classical object. And your observation collapses it,

even if I don't know what you've seen before. You're not a quantum object, so you can't be in a superposition. Okay, so this is an extra twist to it. Now, let's say that you're the observer and you're inside of a black hole and you saw the electron go right or left. I think Sean is asking,

how does that affect things? Did the wave function collapse for the electron, or is it still unknown for the rest of the universe? This is a really great and very, very difficult question. And before we answer it, I want to compare it to a similar complicated question, which is just about entangled objects that are really far apart, right? A similar question you might ask is, well, if the photon is really far away from the electron when it's observed, how does the electron know to collapse? If the photon flies for 1,000 light years before it gets observed,

how does the electron then collapse instantly across time? These questions are related because they have to do with apparently sending impossible information. And this is a classic question in quantum mechanics theory, right? And this is the paradox posed by Einstein decades and decades ago when he complained that quantum mechanics makes no sense because it requires things to violate special relativity to collapse instantly across time. Things outside of each other's light cones somehow causing each other to change. So in the case of entangled quantum particles, the answer is that it does travel faster than light in a way, right?

Like once you collapse, one half of it, a few light years away, it sort of instantly changes what you have in front of you. Exactly. And there's a really crucial subtlety here. You're totally right that the collapse happens instantaneously across space and time. So quantum mechanics is what we call non-local. And that's because the wave function is broad. It doesn't just exist in one place. Don't think of it like one particle doing something to the other. particle is one big quantum state and you collapse it anywhere it collapses everywhere

simultaneously that does happen instantaneously across space and time but and this is the crucial nuance it doesn't send any information so collapsing the wave function with a photon really really far apart doesn't send information to the electron you can't use it to like send signals faster than the speed of light though a lot of people imagine that quantum mechanics entanglement can do that you can't actually send information just collapses the whole wave function simultaneously, it's not a mechanism for information transmission. I see. I think what you're saying is that like there's no rule to how big a quantum system can be or how far apart its parts can be. So like even if I have one half here and another

have, you know, millions of light years away, it's just still one quantum system. There's no ruling quantum mechanics that says, oh, no, you're too far apart. Now you're two separate quantum systems. You're actually like still the same system. Exactly. And quantum mechanics explicitly is non-local. Stuff can happen coordinated across. space and time. It doesn't have to be like this thing bumps into that thing, which is right next to it. It's very weird property of quantum mechanics that we really don't fully understand. Okay. So now the question is, what if half of my system is inside of a black hole, is it still one system? Great question. And the answer depends on your theory of quantum gravity,

because now this is a question that involves quantum mechanics. We're talking about quantum particles and wave functions. And it involves event horizons, so gravitational effects. And the truth is, We don't know how to marry those two things. So I'm sorry, Sean, you're asking a question. We don't really know the answer to because we don't have a theory of quantum gravity. Meaning, like, we don't know how, like if you distort gravity a lot, like in a black hole, you don't know how it affects this idea of like a quantum system being the two halves, even though they're far apart.

Exactly. We just don't know. It might affect it or it might not affect it. Exactly. We don't know if gravity collapses wave functions or not, or gravity is fundamentally quantum mechanical and allows things to be in super positions even as they cross event horizons. We don't have the answer to that. But I can speculate in analogy to the other scenario where you have two quantum particles

really far apart, basically outside of each other's light cones, which is sort of like being outside of each other's event horizons, there's still the wave function does collapse, but no information is transmitted. So I suspect that what happens here is that if you observe the photon inside the black hole, It does collapse the wave function of the electron outside the black hole, but without transmitting any information, and so not breaking that rule of black holes. Well, does that mean you could somehow communicate from inside of a black hole

to the outside of a black hole? No, in the same way that you can't use quantum entangled particle collapse to send information. You also can't send information from inside an event horizon using the collapse of a quantum object across that event horizon. That's the analogy. So I wonder if, like, practically speaking, you didn't really collapse it because you're inside of a black hole and nobody will ever know what you saw. So pretty much the rest of the universe, the half that's outside is still quantum unknown. Yeah, that's very insightful because the reason you can't send information across quantum particles faster than light is that you can't know whether it's collapsed. Like if I have a quantum particle and you have a quantum particle and they're entangled, I can measure mine, which would collapse your.

if you haven't already measured it, but you can't tell if I've collapsed it. All you can do is measure your particle and get like spin up or spin down or left or right. You can never tell that I've collapsed it. That information doesn't get transmitted. And so in the same way, if somebody observes that photon inside the event horizon,

somebody else looking at the electron can't tell whether the electron's wave function has been collapsed or not. Okay, so then the answer to Rashan is that we have no idea, which is a comment answer we give here in the podcast because nobody knows how gravity, or extreme gravity like black holes affects quantum mechanics and quantum systems and wave collapse. But our best guess here on the podcast is that it probably does collapse it, but maybe it doesn't matter, so it doesn't really collapse it.

Yeah, that's a great summary. Well, let's get to our other questions here today about black holes and about the Big Bang and magnetic fields. So let's get to those. But first, let's take a quick break. A foot washed up a shoe with some. bones in it. They had no idea who it was. Most everything was burned up pretty good from the fire that not a whole lot was salvageable.

These are the coldest of cold cases, but everything is about to change. Every case that is a cold case that has DNA right now in a backlog will be identified in our lifetime. A small lab in Texas is cracking the code on DNA. Using new scientific tools, they're finding clues in evidence so tiny you might just miss it. He never thought he was going to get caught. And I just looked at my computer screen. I was just like, ah, gotcha. On America's Crime Lab, we'll learn about victims and survivors.

And you'll meet the team behind the scenes at Othrum, the Houston Lab that takes on the most hopeless cases to finally solve the unsolvable. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. I had this, like, overwhelming sensation that I had. had to call her right then. And I just hit call. I said, you know, hey, I'm Jacob Schick. I'm the CEO of One Tribe Foundation and I just wanted to call on and let her know there's a lot of people

battling some of the very same things you're battling. And there is help out there. The Good Stuff Podcast Season 2 takes a deep look into One Tribe Foundation, a non-profit fighting suicide in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission. I was married to a combat army veteran and he actually took his own life to suicide. One tribe saved my life twice. There's a lot of love that flows through this place and it's sincere. Now it's a personal mission.

Don't want to have to go to any more funerals, you know. I got blown up on a React mission. I ended up having an amputation below the knee of my right leg and a traumatic brain injury because I landed on my head. Welcome to Season 2 of the Good Stuff. Listen to the Good Stuff podcast on the IHeart Radio app, Apple Podcast, or wherever you get your podcast. Your entire identity has been fabricated. Your beloved brother goes missing without a trace.

You discover the depths of your mother's illness the way it has echoed and reverberated throughout your life, impacting your very legacy. Hi, I'm Danny Shapiro. And these are just a few of the profound and powerful stories I'll be mining on our 12th season of Family Secrets. With over 37 million downloads, we continue to be moved and inspired.

by our guests and their courageously told stories. I can't wait to share 10 powerful new episodes with you, stories of tangled up identities, concealed truths, and the way in which family secrets almost always need to be told. I hope you'll join me and my extraordinary guests for this new season of Family Secrets. Listen to Family Secrets Season 12 on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts.

I'm Dr. Joy Harden Bradford, and in session 421 of therapy for black girls, I sit down with Dr. Othia and Billy Shaka to explore how our hair connects to our identity, mental health, and the ways we heal. Because I think hair is a complex language system, right, in terms of it can tell how old you are, your marital status, where you're from, you're a spiritual belief. But I think with social media, there's like a hyperfixation and observation of our hair, right? that this is sometimes the first thing someone sees when we make a post or a reel is how our hair is styled. We talk about the important role hairstylist play in our community, the pressure to always look put together, and how breaking up with perfection can actually free us. Plus, if you're someone who gets anxious about flying,

don't miss Session 418 with Dr. Angela Neil Barnett, where we dive into managing flight anxiety. Listen to therapy for black girls on the iHeart Radio app, Apple Podcasts, or wherever you. you get your podcast. Right, we're taking listener questions here today and at least trying to answer them, although sometimes the answer is we don't, nobody knows. Sometimes the answer is great question.

I wish I knew the answer. If you have the answer, write it to us in a hundred page summary and then Daniel will read it and let you know. That's right. Really, the answer some of these questions requires us to develop. theories of quantum gravity. And to figure out how to develop those theories, we want to look inside black holes,

which is impossible. So we're a little bit stuck sometimes. Well, you can't look inside of a black hole. Just can't tell anyone what you saw. Yeah, that's right. That physicist who fell into a black hole knows the answers. Just can't get any awards for it. Yeah.

That physicist solved everything. Let's throw a Nobel Prize medal inside the black hole for them. There you go. That million dollars. or million crooner, I'm sure they can find a good use for it in there. All right, so our second question comes from Ryan, who lives in Northern Virginia. Hello, Daniel and Jorge. My name is Ryan, and I live in Northern Virginia. I have a question for you today about black holes, more specifically about their magnetic

fields. If the Earth's magnetic field comes from its liquid outer core, where does a black hole's magnetic field come from? Considering there's no liquid core in the black hole and nothing is supposed to be able to escape the event horizon, I'm left to guess that the accretion disk is the big driver of the magnetic field. But that's just a guess. Thanks for considering my question. Love the show. Awesome. Great question, Ryan. You know, I don't know the answer here. And I'm going to guess maybe the answer is again, we don't know, because it deals with black holes. No, this one I think we do know the answer to actually. What? Yeah, I know. Physics knows something.

All right. Well, let's see. Ryan's question is, where does a black hole's magnetic field come from because I guess black holes have a magnetic field do we know that for sure well we do measure very strong magnetic fields near black holes how do we measure them how do we measure them great question well we can see the effect right sometimes black holes have enormous jets of stuff that shoot up and down on their north and south poles and we think that comes from the magnetic field like funneling particles up and down sort of the same way that the earth's magnetic field causes northern lights charged particles coming towards Earth magnetic field get funneled up towards the North and South Poles.

Particles falling into a black hole sometimes will miss because the magnetic field will deflect them up and down. You get these enormous like thousands of light years long jets of stuff shooting out of black holes. We think from the magnetic fields. Well, I guess first of all, we think those are black holes and that those jets are coming from black holes, don't we? Like, we haven't actually seen the inside of it.

What's inside of those jets? We've studied those jets in some great detail and we have really pretty good models that predict those jets. Recently we imaged a couple of black holes and saw ripples in the accretion disk around them and so we're able to like really pin down the details of the magnetic field near the black hole.

I mean, we'd love to send a probe near the black hole and measure those directly, but there's a lot of indirect ways to measure those magnetic fields just by seeing the impact to have on charge particles near the black hole. And I guess the other question is, how do you know those magnetic fields are coming from the black hole and not from the stuff around the black hole?

Yeah, that's a great question. and we don't know the answer to that. We're sure that the stuff around the black hole can make a magnetic field. Those are charged particles. They're moving in a circle. So you have a current moving in a circle that always generates a magnetic field. The second part is thinking about whether a black hole on its own could have a magnetic field, even without the accretion disk, even without the stuff swirling around it.

Whether just the black hole itself can have a magnetic field is a really interesting question. Do we know the answer? Does a black hole on its own have an inherent? magnetic field. So we can answer that question theoretically. We've never seen a black hole all by itself without an accretion disc and measured it. But according to general relativity, black holes can have magnetic fields. And that's because black holes can do two crucial things. One, they can have an electric charge. And two, they can spin. And essentially anything with an electric charge that spins has a magnetic field. But you're saying it's all theoretical, though.

It's theoretical because we've never observed a black hole without any stuff around it and measured its magnetic field. That would be an awesome test of this theory. I see. So basically we don't know. Yeah, that's true of lots of things, I suppose. We're not sure about it, but we do have a pretty good idea. And lots of our models of spinning black holes and black holes with charge have been tested indirectly. We've never done this exact test.

Okay, so you're saying theoretically black holes, do have magnetic fields because they somehow preserve it, right? Even though when you throw charged particles in it, with spin on it and magnetic fields, presumably that doesn't get destroyed by the black hole. Exactly. And Ryan is asking about like where that magnetic field might come from because you can't see anything beyond the event horizon.

So you can't have like swirling matter within the event horizon causing this magnetic field. Why not? Because the details of anything like that happening within the event horizon is shielded. by the event horizon. You can only know a few things about what's happening inside the event horizon. You can know the total mass,

you can know the electric charge, and you can know the spin. Meaning even if there are a bunch of electrons spinning inside of a black hole, the magnetic field they would generate couldn't leak out of the black hole. Is that what you're saying? Because space would just be pointing inwards.

A lot of the details of what's happening to those electrons you wouldn't be sensitive to. Like if one electron zig's up or zigs down, you couldn't sense that the outside. You can, however, sense that there are a bunch of electrons and you can sense that they're spinning overall because you can measure the total spin of the black hole and the total electric charge of the black hole. Like when electron falls into a black hole, just before it falls in, it has an electric field and when it falls in, that electric field is now frozen on

the outside of the black hole. Whatever happened to the electron after it falls in can no longer change that electric field. It's sort of frozen there. So you can tell that something has fallen in and that it had charge, but the detail is what happens afterwards you're shielded from. So then are you saying like to get the magnetic field of a black hole, you just multiply its charge by its spin somehow and that gives you like what you would feel as a magnetic field outside of the black hole. But those are like overall numbers, not related to anything in detail inside of it. Exactly. In the same way that an electron has a little magnetic field. Where does the magnetic field and electron come from? It doesn't have a magnetic charge. It

has an electric charge and it has quantum spin. Those two things combined to give the electron a tiny little magnetic direction, a magnetic dipole. And you can't tell what's going on inside the electron. We think maybe it's a fundamental particle. We have no idea. We can't see inside and it doesn't matter. We know it has an overall charge and an overall spin.

And so the overall charge and spin of a black hole similarly gives it a magnetic moment. It's a magnetic dipole. I wonder if like Ryan's question was more like, you know, how can a black hole have a magnetic field if nothing can escape it. You know what I mean? Like if the electromagnetic field it has is due to the stuff inside of the black hole, how can its magnetism escape the black hole? Yeah, that's a great question.

We have a whole episode on how black holes can have magnetic fields and electric fields and digs into the details of this question. Very briefly, though, the answer is that the overall charge is essentially spread out on the event horizon. So if something falls into a black hole, you're not getting information. from within the event horizon. You're just getting information from the event horizon. So think about the event horizon itself as now having that charge and having that spin.

There might be crazy stuff going on inside, weird quantum effects or singularities or ringularities or whatever. You can't tell, but you can tell that something charged fell in. And you can tell without getting any information about what's going on inside the event horizon. It sort of sounds like you're saying that the black hole's magnetic field comes from its surface. Like, it's the surface of the black hole that's basically, you know, facing out to the rest of the universe and, you know, emanating an electric charge and an electric field. And that's why we can see it. Yeah, that's a good way to think about it.

The event horizon or the surface of it equivalently has three properties, mass, spin, and charge. And we can measure those and those have an effect on the rest of the universe, right? The same way, like the mass of the black hole, even though it's contained within the event horizon, still curves space outside the event horizon. and it can affect their trajectories of stuff. Think of that as a property of the event horizon. It doesn't matter what's going on inside behind the screen of the event horizon if things are swirling around or not. All you know is the overall mass, the overall charge, and the overall spin.

And that can create a magnetic field. But again, time slows down almost to a standstill near the event horizon. How does the magnetic field ever get out? Don't I have to wait till infinity to feel that magnetic field? Yes, so time near the black hole is really, really slowed down. not slowed down totally to infinity. So black holes can radiate information, for example. Like if a black hole gets accelerated by another black hole,

it can radiate a gravitational wave. Or if it has charge, it will also radiate photons. Again, these are coming from the surface of the black hole, not from within it. So we're not breaking the rules of black holes, but they can radiate that information. And you're right, that things near black holes are slowed down. And so it does take longer and like those gravitational waves are slowed down

by the time dilation of the gravitational field. So without that effect, those gravitational waves would look much crazier and the photons would be much higher frequency. But they're stretched out and red shifted by that time dilation. Not all the way to infinity because the curvature isn't infinity outside the black hole. All right. Well, it sounds like the answer for Ryan

is that a black hole's magnetic field comes from its surface. It's event horizon, basically, or at least we can practically think of it as coming from the surface and the event horizon. and that's why we're able to see it and experience it. We think. We think most... We don't know for sure because it's a black hole.

We don't know for sure anything. We don't even know if we exist or if this is a simulation. And also remember that most of the magnetic fields we've measured probably do mostly come from the accretion disk of stuff around them. But as Jorge says, we don't know for sure. All right. Well, let's get to our last question of the day, which is about the expanding universe and gravity

and the Big Bang. But first, let's take another quick break. A foot washed up a shoe with some bones in it. They had no idea who it was. Most everything was burned up pretty good from the fire that not a whole lot was salvageable. These are the coldest of cold cases, but everything is about to change. Every case that is a cold case that has DNA. Right now in a backlog will be identified in our lifetime. A small lab in Texas is cracking the code on DNA. Using new scientific tools, they're finding clues in evidence so tiny you might just miss it.

He never thought he was going to get caught, and I just looked at my computer screen. I was just like, ah, gotcha. On America's Crime Lab, we'll learn about victims and survivors, and you'll meet the team behind the scenes at Othrum, the Houston Lab that takes on the most hopeless cases, to finally solve the unsolvable. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Your entire identity has been fabricated. Your beloved brother goes missing without a trace.

You discover the depths of your mother's illness, the way it has echoed and reverberated throughout your life, impacting your very legacy. Hi, I'm Danny Shapiro. And these are just a few of the profound and powerful stories I'll be mining on our life. 12th season of Family Secrets. With over 37 million downloads, we continue to be moved and inspired by our guests and their courageously told stories. I can't wait to share 10 powerful new episodes with you, stories of tangled up identities, concealed truths, and the way in which family secrets almost always need to be told. I hope you'll join me and my extraordinary guests for this new season of Family Secrets. Listen to

Family Secrets Season 12 on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. I had this, like, overwhelming sensation that I had to call her right then. And I just hit call. I said, you know, hey, I'm Jacob Schick. I'm the CEO of One Tribe Foundation. And I just wanted to call on and let her know there's a lot of people battling some of the very same things you're battling. And there is help out there. The Good Stuff Podcast, Season 2, takes a deep look into One Tribe Foundation, a nonprofit fighting suicide.

in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission. I was married to a combat army veteran, and he actually took his own life to suicide. One Tribe saved my life twice. There's a lot of love that flows through this place,

and it's sincere. Now it's a personal mission. Don't have to go to any more funerals, you know. I got blown up on a React mission. I ended up having amputation below the knee of my right leg and a traumatic brain injury because I landed on my head. Welcome to Season 2 of the Good Stuff. Listen to the Good Stuff podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts.

I'm Dr. Joy Hardin Bradford. And in session 421 of Therapy for Black Girls, I sit down with Dr. Othia and Billy Shaka to explore how our hair connects to our identity, mental health, and the ways we heal. Because I think hair is a complex language system, right, in terms of it can tell how old you are, your marital status, where you're from, your spiritual beliefs. but I think with social media there's like a hyper fixation and observation of our hair right, that this is sometimes the first thing someone sees when we make a post

or a reel is how our hair is styled. We talk about the important role hairstyles play in our community the pressure to always look put together and how breaking up with perfection can actually free us. Plus, if you're someone who gets anxious about flying, don't

miss session 418 with Dr. Angela Neil Barnett, where we dive to managing flight anxiety. Listen to therapy for black girls on the IHeartRadio app, Apple Podcasts, or wherever you get your podcast. All right, we're answering listener questions here, our favorite kind of episode where we take your questions that you send in and we try to answer them, usually with answers that are not,

we don't know. We do our best. Sometimes nobody knows, which is an answer, technically. It is. And I wonder if that's like really satisfying because it means for the listener like, ooh, I'm at the forefront of human knowledge or really disappointing because like the rest of humanity is still left unsatisfied. I guess it is pretty exciting, right?

To be, to like come up against the boundary of human knowledge, right? Yeah, exactly. Like when I ask you a question and you don't know the answer, I'm like, wow, I am at the boundary of Daniel's knowledge of the universe. Now, the boundary of Daniel's knowledge, not the same as the boundary of human knowledge. Let's not make that mistake. Or at least the boundary of the research you've been able to do for the last hour before the podcast. Exactly.

I'm at the boundary of human knowledge in one tiniest little corner of the vast sphere of human knowledge. Well, we're all here with you. And so our last question of the day comes from Arjun. Hi, Daniel. I have a question. It just got me thinking while I was on. the shower. We've come to understand that gravity is a bending of space time and that's objects which would normally travel in a straight line tend to take a curved path around the body which

is distorting space time. We also know that space itself is expanding in the universe for the last ever since Big Bang happened. Do we think the effects of gravity have changed over the last couple billion years or do we expect it to be different later now that we know that space itself is expanding or stretching or thinning out whatever you may call it will that affect the way gravity acts and behaves or has it changed over the years what do you reckon awesome question what do we reckon daniel do we know the answer in this case i reckon that arjun probably takes really long showers to have such deep thoughts about the whole history of the universe which is awesome Thank you, Arjun, for such a great question.

So as usual, we have some ideas about how this works, but there's lots that we still don't understand, especially about the expanding and the accelerating expansion of the universe. Okay, let me see if I understand Arjun's question. He's in the shower, and he's wondering, you know, the universe, since the Big Bang has, first of all, it expanded really fast, space itself expanded really fast, and space today is still expanding,

and there's more and more space growing and being created. The universe is expanding due to something called Dark. energy and I think his question is like is gravity affected by this expansion of space like do we know if gravity itself has been the same for the last 14 billion years or is there an indication that maybe as the universe expands it could be changing the effects of gravity like is gravity space dependent what do you reckon daniel i think there's a crucial piece of the history of the universe that you sort of yada yotted over there because you're right the things did expand very quickly in the beginning, but then that expansion actually decelerated because the stuff

in the universe slowed down the expansion. And then later on, like six billion years ago, it started picking up again and it started to accelerate the expansion. So there's this funny sort of like zigzag in the history of the universe. It wasn't always just accelerating expansion. It was always expansion, but there was a period when that expansion was decelerating. I emphasize that not just because it's a cool zigzag, but to underline something which I think is crucial to answering Arjun's question, is that's part of gravity. Gravity is not just things pulling themselves together. It's also space expanding. That is general relativity, our framework that we have, what Arjun describes is like things moving through bent space time. That allows for the universe to expand. That's sort of part

of what gravity is. What do you mean? Like it's in the equations of our theories of gravity for the universe to expand due to dark energy? It's part of general relativity that the universe can expand under certain conditions. So the broad answer to Arjun's question is we think the rules of the universe, the rules of gravity and space time and general relativity have not changed over the last 14 billion years. And we can describe all of these weird epics of the universe using one consistent framework. And that's sort of amazing. So the rules haven't changed even though the conditions do change from year to year and things get further apart and whatever. So there are specific conditions under which general relativity predicts the universe will expand and that that expansion will

accelerate. If you have a bunch of energy inherent in space stored in a field that has high potential energy, then general relativity says space will expand and that expansion will accelerate. So we see that happening in the universe. We look back at the history of the universe. We see it's expanding. We see that expansion is accelerating. And so we say, oh, there must be some energy stored in a field somewhere with a lot of potential energy that's causing this. We don't know what that is. We don't know what that field is. We have no explanation for it. But general relativity can accommodate that. Okay. I think what you're saying is that physicists have a set of equations that explain the universe and that set of equations has gravity in it and it also has the expansion

of the universe in it. So it's like they're all actually kind of connected already in the theories of physics. Yes, exactly. So it's not like one of them, we don't know if one of them is doing something the other one doesn't know. That's right. And when people say gravity, colloquially, they mean like stuff attracting and things falling towards planets and whatever. When physicists say gravity, they mean the whole shebang. They mean the whole theory of space. time and all of its consequences because moving from like a Newtonian view of gravity as a force to an Einsteinian view of gravity as motion of stuff through curved space time has all of these consequences not just oh light is also bent by gravity but also the universe can expand and it could

also collapse all of these things are consequences of this geometric view of the universe we have from general relativity and we think that those rules have not changed that the same rules applied in the very, very beginning and in the middle point when things were decelerating, and now when things are accelerating. So in the broadest sense, the rules of gravity, general relativity have not changed over the course of the universe.

I see, like the rules by which you mean the equations, but I wonder if Arjun means like, you know, imagine there's a term in your equations for gravity. I wonder if he could mean that, you know, has that term in the equation change as the universe grew? Like, could it that be something the equations don't take into account or

could it be something we haven't noticed or or what? Yeah, there's a couple ways in which that could be true. First of all, we assume that dark energy or whatever this is, this potential field that's causing the accelerating expansion in the universe, we assume that that's constant everywhere in space and everywhere in time. And mostly that works. I mean, I said that we can explain the whole history of the universe, and that's mostly

true, but there are some discrepancies. Like we measure it early in the universe, we measure it late in the universe, and those two numbers don't quite agree. You can read more about that. It's called the Hubble Tension, essentially that's predicting the rate of expansion. and different measurements don't quite agree. So that's quite interesting. So it might be that the dark energy is changing over time.

And again, that wouldn't mean a change in the rules, but it would mean some change in the conditions, which is affecting your experience of the universe. And also, maybe more importantly, the second sense is that the density of stuff in the universe is definitely decreasing. Like things used to be really hot and dense, and now they're very cold and very far apart. And so there's definitely like less sense of gravity in the universe

because those mass density of stuff in the universe is going down. Space goes up. The amount of mass doesn't change, so the density decreases. Things get further and further apart. You're feeling less gravity from distant galaxies than you were before because they're now further away from you, and that's going to keep going. So I guess technically you would be feeling more the gravity of Earth, right, as the universe gets more empty and empty, right? Like, I'm going to weigh more in the future, regardless of what I do. If you're relying on distant gravities to lift you up off the surface of the earth

and make you feel light, then I have bad news for you, yes. That's my diet plan. Forget a Zempic, you know. The dark energy diet. Yeah, exactly. I suggest hitting the gym instead of relying on distant galaxies. But I'm not a health expert. Don't take advice from me.

Well, I wonder if Arjun's question then maybe more simply is like, you know, if I have a black hole of the same mass and I see it bend light around it, is it going to bend light the same way now, in the future, in the past when the universe was maybe more scrunched together,

or is that light can be bent differently depending on what the universe is doing? Like, especially like, let's say we're going through a period where space is expanding faster and faster or we're hitting, you know, in that zigzag, we're hitting a point of maximum expansion. That light is going to bend

a little bit differently, right, than it would in a period of not so fast expansion. All right. So now you've pushed this into a corner of general relativity that we don't understand very well. So the answer is we don't know. The answer is we don't know. And also fascinatingly because we don't even understand our own theory. Like general relativity has no problem with having black holes in an expanding universe. But we don't know how to do that calculation. Like Einstein's equations are nasty and they're very, very difficult to solve. We can only solve them in very specialized simplified settings like

you have a black hole in an otherwise empty universe that we can solve. Or, Or you have a universe that's expanding, but the matter in it is totally uniform, like dust sprinkled everywhere. We don't know how to solve the equations for a black hole in an expanding universe or a universe with like chunky stuff in it. So we have all these approximations. And so the specific question you just asked, like what happens to a black hole in the expanding universe, we don't know how to do that calculation. But we think that the rules are not changing, right? And so for a black hole, gravity is basically the same as it was a billion. years ago and 5 billion years ago, like the nature of space itself is not changing. It doesn't

thin out. You know, as the universe expands and that expansion accelerates, you just get more space and that space behaves, we think, according to the same rules. And so bends light the same way as it always did. All right. Well, then the answer, Arjun seems to be that. You don't think that the rules of the universe are changing, meaning like what a physicist would consider to be gravity, which is the whole set of equations, you don't think that's changing. But maybe the effects of a black hole might be changing, you don't know how to calculate that. That's right. And there was even this fast-in-any paper a few months ago

about how black holes might be driving the expansion of the universe, right? That black holes might actually be like weird clusters of dark energy. So just to highlight like how little we understand the expansion of the universe and how tricky it is to do these kind of calculations in any sort of realistic setting. Yeah, or in the shower. The shower is probably the best place to do these calculations. Yeah. Well, if it wasn't for gravity,

You couldn't take a shower. You definitely need gravity to shower. Oh, my gosh. Wow. Thank you, gravity. We should be saying every time we have a shower. Yeah. If not, for gravity, we'd all be a little bit stinkier.

Or we would all have to take baths in zero gravity, which I think is dangerous, isn't it? Like, you would very quickly drown because the water would just engulf you. Maybe. But again, don't take health advice from this podcast that is outside our area of expertise. Yeah. Don't take health advice from a cartoonist and a physicist. Stay on your diet, whatever it was before this podcast. That's right.

Listen to a real doctor. Not the academic kind. Exactly. You know what the best thing about getting your PhD is? There's a best thing. Every meeting is now a doctor's appointment. There you go. I'm sure everyone loves doctor's appointments.

Does that mean that this podcast is a doctor's appointment for the thousands of people who listen to us? I guess so, yeah. Oh, man. Keep your pants on, everyone. Yeah, keep your pants out. We're not going to grab anything or ask you to cough. No. The only things we're probing are the nature of the universe. The only black holes we're investigating are the theoretical kind. That's right. That's right. Only physical dark matter that we're interested in. All right. Well, that answers Arjun's question and everybody's question.

Again, another interesting journey to the edge of human knowledge in the realization of how much we know and still have yet to know about the universe, which is kind of exciting. That's right, so keep asking questions. You'll be surprised how quickly you can get to the edge of human knowledge. Or the edge of a black hole, apparently. Or the edge of this doctor's appointment.

Or the edge of this podcast. So we hope you enjoyed that. Thanks for joining us. See you next night. For more science and curiosity, come find us on social media where we answer questions. and post videos.

We're on Twitter, Discord, Insta, and now TikTok. And remember that Daniel and Jorge Explain the Universe is a production of IHeartRadio. For more podcasts from IHeartRadio, visit the IHeartRadio Apple, Apple Podcasts, or wherever you listen to your favorite shows. It's important that we just reassure people that they're not alone, and there is help out there.

The Good Stuff Podcasts, season two, takes a deep look into One Tribe Foundation, a non-profit fighting suicide in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission. One Tribe, save my life twice. Welcome to Season 2 of the Good Stuff.

Listen to the Good Stuff podcast on the Iheart Radio app, Apple Podcast, or wherever you get your podcast. Every case that is a cold case that has DNA. Right now in a backlog will be identified in our lifetime. On the new podcast, America's Crime Lab, every case has a story to tell, and the DNA holds the truth. He never thought he was going to get caught, and I just looked at my computer screen. I was just like, ah, gotcha. This technology's already solving so many cases.

Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast. Here's a clip from an upcoming conversation of... about how to be a better you. When you think about emotion regulation, you're not going to choose an adaptive strategy which is more effortful to use unless you think there's a good outcome. Avoidance is easier.

Ignoring is easier. Denials easier. Complex problem solving takes effort. Listen to the psychology podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. This is an IHeart podcast.