Hey, Kelly, we love physics on the podcast, don't we.
Yes, especially when it's not physics that's threatening the lives of my children.
Yes.
And we're big fans of biology, of course, naturally, and we agree that chemistry is not a science but actually a torture device invented to ruin the lives of tenth graders around the world.
Right, Well, it might be complicated. I mean, yes, chemistry was the one class in college I got a B plus in and I hated it and I still kind of hate it. But like you know, food, chemistry, there's it's complicated.
Wait are you a pro chemistryite? Is that what's happening here?
It's just it's not so black and white, That's what I'm saying.
Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I believe in drawing clear, bright lines between the sciences.
You know. I think one of my favorite episodes that we did was about whether or not we need to thinking about biological questions at the level of physics. And so I don't think I believe that you like to draw black and white lines between topics. And I think we both agree it's more fun when they kind of meld into one another.
No, you're right, all of science is a big, squishy endeavor, but chemistry is on the other side of that line.
Yeah. No, we hate chemistry. That's fine. Oh, kem, like maybe the hardest thing I've ever done. Like, OKM, then childbirth.
You shouldn't do either of those without anesthetic.
That's right, that's right. I'm Kelly. I got bees in chemistry, and I met Rice University where I study parasites as an adjunct.
And welcome to the podcast Daniel and Jorge explain in the Universe, in which we talk about our love for physics and the universe, and we try to avoid negging chemistry, but it's unavoidable sometimes.
Yeah. Yeah, No, it makes you feel better too sometimes, so you just need you've got to go for it.
I just like provoking those chemistry loving listeners, because you know, I love your messages in my inbox, even if they're angry rants about how wonderful chemistry is. Send them to me.
Out of all the fields that you probably don't want to make people angry, and I think the chemists probably have the most ways to like kill you in ways that can't be tracked so.
Lately. I'm not sure this was well thought out in the end, but we do want to hear from you. We want to hear about your love for chemistry, your love for physics, and also your questions about the nature of the universe, because on this podcast, we believe that everybody deserves to understand what we do and don't know about the universe, to have it explained to them in
a way that's understandable, that clicks in their mind. And so if you have a question about how the universe works that you haven't heard a sufficient answer to, please write to us to questions at Daniel and Jorge dot com. You will always hear from us, even deep into the far future when we're writing emails from caves in front of the flickering fire because chemistry has destroyed the world. We will still answer your questions.
That's right, nothing can stop us.
So today on the podcast we'll be answering listener questions Fall Equinox Edition. We are happy to be back in your ear holes talking about the mysteries of the universe and specifically answering questions from listeners like you.
And we must be out of practice because otherwise we wouldn't have threatened the chemists.
Exactly. Good to shake off the rust a little bit. Wait, rust is chemistry, isn't it? Anyway, Today we have a question that's definitely about physics, but it's also about things that are black and white. This is a question from white about white holes.
Thank Daniel and hohe. I have a question about black holes. I've heard of some theories about white holes existing, and I was wondering where the white holes would get all the stuff they were spewing out. Could it be possible that somehow black holes in white house holes are connected. If that is the case, and theoretically, is it possible to escape a black hole? Thank you so much, Wyatt.
So I don't think that I've ever heard about a white hole. But then you're gonna be like Kelly, you forget you were on an entire episode where we spent an hour talking about this, because my memory is really really good. But often I think that in science sometimes things don't have to be super analogous. But we're just like, well, it would be kind of fun if I named it
this thing that I found something similar. So, yeah, tell me about white holes and are they like the opposite of a black hole, Like, what is the deal?
Yeah, white holes are very confusing because they're not even a very well defined concept like a black hole. At least we know exactly what we're talking about, and we know in general relativity it's a region in space where things can fall in, but nothing can leave because space is so twisted, so bent up, that every path forward leads towards the center. The idea of a black hole is not just that there's a very powerful force of gravity, but that space itself is curved in such a way
that every path just leads towards the center. Right, it's a real extreme version of general relativity. Really forces you to think about things not in terms of gravity as a force, but as the bending of space time changing how things move. So that's what a black hole is. A white hole is much more fuzzy. Some people in gravitational theory and in quantum gravity say white holes don't even exist. Their nonsense. So there's lots of disagreement about what they are. But as you say, there's sort of
like an analogy that black holes. People ask like, well, what about the opposite of a black hole? What would that be like? And so a white hole is sort of like, you know, take a black hole and flip it through the mirror, what would it look like? And that's what you get as a white hole. And so a white hole in theory would be a region of space where, instead of not being able to escape, nothing
can go in. Right, It's a place you can't enter, So things can escape somehow if they're already there, but nothing could go into a white hole. It's a place in space where there are no paths to it, instead of no paths out of it.
So it's like running into a wall, like with the road Runner in Coyote. Is that like you just you can't get in there.
It's not like there's a wall there that's preventing you. You have to think about space as being curved and there's just like no way to get there. It's not like there's an obstacle between you and there. It's just like no paths lead there. You have to try to like Google map something, and it's like there is no route. That's essentially this idea that there might be places in space that are blocked off by the curvature so that
you can never even get there. Not that you can't escape, but that you can never even get there, and they're motivated by this sort of theoretical calculation that Roger Penrose did. He thought about like the way space is organized around a black hole, and he carves it up into these coordinates, and there's the coordinates near the black hole and coordinates in the black hole, and the way that he sort of laid it out on a piece of paper, there's
like a blank spot. It suggests that there could be a place in space where particles could go from there, but because of the shape of the event horizon near a black hole, they could never get in there. And so it's sort of conceptually trying to like cross the T or dot the I to say like, well, if it's here on the piece of paper, maybe it also actually exists out there in the universe.
And so the thing that would be keeping you from getting there is that like some force is pulling you too hard for you to be able to move into that space. Is that the mmm?
Okay, yeah, exactly. So imagine, for example, there's a white hole somewhere in space and you have a laser and you shoot your laser at the white hole and you think, well, why can't my photon go into the white hole. Well, the reason it's a white hole is that space is curved around it, and so if you try to shoot your laser at the white hole, you'll find that it doesn't go in. It bends through curved space and goes
in another direction. The same way, for example, if you shoot a laser beam near a black hole, it can bend around the black hole and go in some other direction. Right, we know that curved space can change the path of photons than any other particle, right, that's what curved space does. That's why curved space is so awesome, because it can even change the path of photons, which have no mass,
they technically feel no gravity. But that's why it's important to think about gravity as curvature of space, changing the path of particles that flow through it. So, now, just arrange space to have curvature so that no matter what direction you shoot a photon from, it basically glances off. It's like the perfect armor you have, like space as a shield, so that anything that comes near you just pick ricochets off and goes in another direction. It's not
like a wall there. It's not a force, it's the curvature of space itself. That you've ranged in this way that photon glance off and go in another direction.
What would you need to have for that to happen? By making sense, how would that come about?
Yeah, you're perfectly making sense, And nobody really knows the answer to that question because it's not really a solid theoretical concept. Nobody knows how a white hole could form. There's this theory that if there was a black hole which had existed forever, an eternal black hole, not one
that was created. We we have, like a star that collapses and forms a black hole, but a black hole which it somehow existed forever, even though we think the universe has a finite age in general relativity imagined somehow an infinitely old universe that doesn't have a big bang in the heart of it. So you could have eternal black holes. These things somehow would also have white holes attached to them, And that's essentially what why it is
asking about. Somehow, if you have an eternal black hole formed in such a way that it's always existed, right so I guess, not formed just like exists, then it naturally has a region of space which is also a white hole. So we don't know how to make one. But if an eternal black hole existed, then the theory suggests they would also be a paired with it, a
white hole, and the two are connected. So the singularity of the black holes connected to the edge of this white hole in such a way that things that fall into the black hole could come out the white hole.
But only if the black hole always existed.
Only if the black hole always existed. So we don't know how to make this, but it is compatible with general relativity. It's very similar situation to the other mind bending concept in general relativity of wormholes. Wormholes are the connection between two points in space. The idea that like, all right, I'm here and I want to be an Alpha centauri, but I don't want to fly through four light years of space to get there, because the speed
of light means that would take forever. What if instead of flying through space, there was just like a connection between my spot in space and their spot in space, so I could just like step through a portal to go from here to there. That's allowed in general relativity. That's called a wormhole.
I think one of my biggest disappointments with physics, or maybe physicists, is that you all haven't figured that out yet, because those wormholes would be great, and I.
Want to get to Wyatt's question about white holes, but first let's take a quick break. Okay, we're back and we're answering listener questions about black holes and white holes and wormholes and all the holes that they make in your brain.
I just finished reading auror U by Kim Stanley Robinson, and I think interplanetary travel would be super cool but probably will mostly just kill people unless we can figure out something like the wormholes. So anyway, get on it please.
Heck, I even want wormholes for like going to work or going to the grocery store. Like imagine you don't need a shopping cart and then load it into your car, and then unload it from your car and load in your fridge. You could just stand at your fridge, open a wormhole to the grocery store and just take stuff off the shelf directly into your fridge.
Theft would be a much bigger problem in a world with that technology.
That's an engineering challenge once we figure out the physics. But yes, wormholes are definitely something we aspire to, and the amazing thing is that they're not ruled out in general relativity they are allowed, but again we don't know how to make them. We can say that a wormhole can exist in the universe general relativity doesn't forbid it, but we don't know how to go from a universe without a wormhole to a universe with a wormhole and
still follow all the laws of general relativity. It's like saying, oh, yes, that house would hold itself up. We have no idea how to construct it, so it also holds itself up while it's half built. Right. We don't have a path to go from a no wormhole universe to a wormhole universe, and in the same way, we don't know how to go from a universe without a white hole black hole pair connected by a wormhole to a universe that has one.
We can say if it exists in the universe and has always existed somehow weirdly in a way that makes no sense, then that's fine with the laws of physics, But we don't know how to go from not having one to having one. How to basically build a white hole?
Ugh uugh is all I could think.
This is complicated.
Let's imagine a white hole does exist out there. What would you see that would make you be like, oh my gosh, we actually found one, and would it be something emerging? Like you put your laser out there, the laser goes around the bend of space time, but then a laser comes back out through the spot that you tried to get it into but it couldn't and then you were like, whoa something came out of the white hole. That would be evidence if you saw something like that.
Yeah, that's a pretty good short version of it. Let's unpack it a little bit. Like one way to discover a white hole is to see evidence of a place in space that nothing can enter. The same way we look for a black hole as a region of space that's emitting no light, no radiation. We know this tremendous curvature, but we don't know what's there, and it's not glowing in any way. And so that's how we forget, example,
discovered black holes near the center of the galaxy. We see things zooming by, so we know there's a lot of mass in a very small space, but we can't actually see anything. In the same way, we might discover white hole by finding some location in space where weirdly photons get bent around it. The more direct evidence would be a place in space that's emitting light with no
other explanation. Right, if laser beams are shooting out of some place in space and there's no known origin for it, that's like a great analogy to you know, laser beams are being eaten by this black hole. So if laser beams are just being generated by space, that would be
really fascinating clue about white holes. The problem is though, that we don't know that white holes would have to generate radiation, right, Like, the thing about a white hole is that nothing can enter it, but that also means that nothing has to leave it, right, Things can leave it, but they will only leave the white hole if they're in there. So you could have like a white hole that's empty. Nothing can enter it, and so things could leave it if they were there, but there's nothing in there,
so it's basic invisible. And so it's possible to have white holes that are like quiet that don't emit anything. But if you have a white hole that's connected to a black hole, and I think this is why it's questioned if black holes and white holes are connected, then stuff could fall into the black hole and be connected to the white hole. And come out the other side of the white hole, and that would be basically like a wormhole. But if you one directional right, you couldn't go back
in the white hole. So you take that trip to Alpha Centauri, you're in Alpha Centauri unless there's another black hole white hole pair going the other direction.
And when you get to Alpha Centauri, are you still spaghettified.
Yeah, there's a whole lot more to figure out there from an engineering perspective, because these wormholes are a minuscule you know, they're particle sized, and so to make them larger requires all sorts of exotic technology. We definitely do not have like particles that radiate energy, negative mass particles that essentially expand space the way dark energy does. We don't know if that's possible at all. And as you approach the mouth of this black hole, you would still
be spagetified. So in order to be safe, you'd want the black hole to be really, really large, because larger black holes have weaker tidal forces near their edge. So there's a lot to figure out before you're willing to send your kids to the store using a black hole white hole pair, for sure, But in principle it is theoretically possible, but again, we don't know how to build it, so it's really a ways off. And it might turn out, in a fuller understanding of gravity that the thing makes
no sense at all, that white holes don't exist. It might just be a feature of our classical theory of general relativity.
Oh, physics, you're so crazy.
The thing I love about this question is that it highlights, like, really how little we understand about the basic nature of space and time. You know, Newton thought about space and time is absolute and infinite, just like the backdrop of the universe. But we now know that it's more interesting than that. We know that space can twist and ripple and curve and expand and do all sorts of funny things,
but we still don't really understand what space is. We know that our current theory general relativity has got to be incomplete, and it's got all these wacko predictions, some of which come true, like black holes, and other things like singularities inside black holes we're pretty sure are wrong, and the other weird features like white holes were like, man,
that is bonkers. Let's figure this all out. But in one hundred years or five hundred years, when we have figured this all out, people are going to look back and think, wow, we really didn't understand anything back in twenty twenty four.
So the good news is that there's lots of job security in physics because there's lots of work left to do.
It turns out the universe is a pretty big puzzle. So thank you very much. Why to write again with your particular question about physics. We want to hear from all of you forever and deep into the infinite future. If you have questions about the nature of the universe, please write to us two questions at Danielanjorney dot com. But just to wrap up why, the answer is, white holes are a very fuzzy theoretical concept, not even every
theorist that thinks that they make sense theoretically. But if they do exist, and they have always existed in the universe, then it's possible that they are connections between black holes and white holes, and that you could go into a black hole and emerge from a white hole. But Kelly would have to sign off on a permission slip telling you that it's safe. First.
I'm only signing off on my kids' permission slips. Everybody else can make their own decisions. I'm only holding back my children from exploring the universe.
You don't feel some sort of in loco parentis obligation as a podcast host.
Hosting a podcast doesn't make me feel like I have any obligations whatsoever. But I do feel like I need to let my kids make their own choices eventually, but not yet.
All right, everybody you heard that you're on your own, make your own decisions. All we can do is advise you.
That means you can't sue us.
That's really what it means, Yes, chemists or not, you can't sue us. Well. Thanks very much for joining us on this black and white episode about drawing boundaries between regions in space. Thank you Why for running in, Thank you Kelly for joining me, and thanks everybody for thinking about the universe.
Thanks Daniel.
Tune in next time 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. 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.