Speaker 1: Hey, Kelly, we love physics on the podcast, don't we.
Speaker 2: Yes, especially when it's not physics that's threatening the lives
Speaker 2: of my children.
Speaker 3: Yes.
Speaker 1: And we're big fans of biology, of course, naturally, and
Speaker 1: we agree that chemistry is not a science but actually
Speaker 1: a torture device invented to ruin the lives of tenth
Speaker 1: graders around the world.
Speaker 2: Right, Well, it might be complicated. I mean, yes, chemistry
Speaker 2: was the one class in college I got a B
Speaker 2: plus in and I hated it and I still kind
Speaker 2: of hate it. But like you know, food, chemistry, there's
Speaker 2: it's complicated.
Speaker 1: Wait are you a pro chemistryite? Is that what's happening here?
Speaker 2: It's just it's not so black and white, That's what
Speaker 2: I'm saying.
Speaker 1: Hi, I'm Daniel. I'm a particle physicist and a professor
Speaker 1: at UC Irvine, and I believe in drawing clear, bright
Speaker 1: lines between the sciences.
Speaker 2: You know. I think one of my favorite episodes that
Speaker 2: we did was about whether or not we need to
Speaker 2: thinking about biological questions at the level of physics. And
Speaker 2: so I don't think I believe that you like to
Speaker 2: draw black and white lines between topics. And I think
Speaker 2: we both agree it's more fun when they kind of
Speaker 2: meld into one another.
Speaker 1: No, you're right, all of science is a big, squishy endeavor,
Speaker 1: but chemistry is on the other side of that line.
Speaker 2: Yeah. No, we hate chemistry. That's fine. Oh, kem, like
Speaker 2: maybe the hardest thing I've ever done. Like, OKM, then childbirth.
Speaker 1: You shouldn't do either of those without anesthetic.
Speaker 2: That's right, that's right. I'm Kelly. I got bees in chemistry,
Speaker 2: and I met Rice University where I study parasites as
Speaker 2: an adjunct.
Speaker 1: And welcome to the podcast Daniel and Jorge explain in
Speaker 1: the Universe, in which we talk about our love for
Speaker 1: physics and the universe, and we try to avoid negging chemistry,
Speaker 1: but it's unavoidable sometimes.
Speaker 2: Yeah. Yeah, No, it makes you feel better too sometimes,
Speaker 2: so you just need you've got to go for it.
Speaker 1: I just like provoking those chemistry loving listeners, because you know,
Speaker 1: I love your messages in my inbox, even if they're
Speaker 1: angry rants about how wonderful chemistry is. Send them to me.
Speaker 2: Out of all the fields that you probably don't want
Speaker 2: to make people angry, and I think the chemists probably
Speaker 2: have the most ways to like kill you in ways
Speaker 2: that can't be tracked so.
Speaker 1: Lately. I'm not sure this was well thought out in
Speaker 1: the end, but we do want to hear from you.
Speaker 1: We want to hear about your love for chemistry, your
Speaker 1: love for physics, and also your questions about the nature
Speaker 1: of the universe, because on this podcast, we believe that
Speaker 1: everybody deserves to understand what we do and don't know
Speaker 1: about the universe, to have it explained to them in
Speaker 1: a way that's understandable, that clicks in their mind. And
Speaker 1: so if you have a question about how the universe
Speaker 1: works that you haven't heard a sufficient answer to, please
Speaker 1: write to us to questions at Daniel and Jorge dot com.
Speaker 1: You will always hear from us, even deep into the
Speaker 1: far future when we're writing emails from caves in front
Speaker 1: of the flickering fire because chemistry has destroyed the world.
Speaker 1: We will still answer your questions.
Speaker 2: That's right, nothing can stop us.
Speaker 1: So today on the podcast we'll be answering listener questions
Speaker 1: Fall Equinox Edition. We are happy to be back in
Speaker 1: your ear holes talking about the mysteries of the universe
Speaker 1: and specifically answering questions from listeners like you.
Speaker 2: And we must be out of practice because otherwise we
Speaker 2: wouldn't have threatened the chemists.
Speaker 1: Exactly. Good to shake off the rust a little bit. Wait,
Speaker 1: rust is chemistry, isn't it? Anyway, Today we have a
Speaker 1: question that's definitely about physics, but it's also about things
Speaker 1: that are black and white. This is a question from
Speaker 1: white about white holes.
Speaker 3: Thank Daniel and hohe. I have a question about black holes.
Speaker 3: I've heard of some theories about white holes existing, and
Speaker 3: I was wondering where the white holes would get all
Speaker 3: the stuff they were spewing out. Could it be possible
Speaker 3: that somehow black holes in white house holes are connected.
Speaker 3: If that is the case, and theoretically, is it possible
Speaker 3: to escape a black hole? Thank you so much, Wyatt.
Speaker 2: So I don't think that I've ever heard about a
Speaker 2: white hole. But then you're gonna be like Kelly, you
Speaker 2: forget you were on an entire episode where we spent
Speaker 2: an hour talking about this, because my memory is really
Speaker 2: really good. But often I think that in science sometimes
Speaker 2: things don't have to be super analogous. But we're just like, well,
Speaker 2: it would be kind of fun if I named it
Speaker 2: this thing that I found something similar. So, yeah, tell
Speaker 2: me about white holes and are they like the opposite
Speaker 2: of a black hole, Like, what is the deal?
Speaker 1: Yeah, white holes are very confusing because they're not even
Speaker 1: a very well defined concept like a black hole. At
Speaker 1: least we know exactly what we're talking about, and we
Speaker 1: know in general relativity it's a region in space where
Speaker 1: things can fall in, but nothing can leave because space
Speaker 1: is so twisted, so bent up, that every path forward
Speaker 1: leads towards the center. The idea of a black hole
Speaker 1: is not just that there's a very powerful force of gravity,
Speaker 1: but that space itself is curved in such a way
Speaker 1: that every path just leads towards the center. Right, it's
Speaker 1: a real extreme version of general relativity. Really forces you
Speaker 1: to think about things not in terms of gravity as
Speaker 1: a force, but as the bending of space time changing
Speaker 1: how things move. So that's what a black hole is.
Speaker 1: A white hole is much more fuzzy. Some people in
Speaker 1: gravitational theory and in quantum gravity say white holes don't
Speaker 1: even exist. Their nonsense. So there's lots of disagreement about
Speaker 1: what they are. But as you say, there's sort of
Speaker 1: like an analogy that black holes. People ask like, well,
Speaker 1: what about the opposite of a black hole? What would
Speaker 1: that be like? And so a white hole is sort
Speaker 1: of like, you know, take a black hole and flip
Speaker 1: it through the mirror, what would it look like? And
Speaker 1: that's what you get as a white hole. And so
Speaker 1: a white hole in theory would be a region of
Speaker 1: space where, instead of not being able to escape, nothing
Speaker 1: can go in. Right, It's a place you can't enter,
Speaker 1: So things can escape somehow if they're already there, but
Speaker 1: nothing could go into a white hole. It's a place
Speaker 1: in space where there are no paths to it, instead
Speaker 1: of no paths out of it.
Speaker 2: So it's like running into a wall, like with the
Speaker 2: road Runner in Coyote. Is that like you just you
Speaker 2: can't get in there.
Speaker 1: It's not like there's a wall there that's preventing you.
Speaker 1: You have to think about space as being curved and
Speaker 1: there's just like no way to get there. It's not
Speaker 1: like there's an obstacle between you and there. It's just
Speaker 1: like no paths lead there. You have to try to
Speaker 1: like Google map something, and it's like there is no route.
Speaker 1: That's essentially this idea that there might be places in
Speaker 1: space that are blocked off by the curvature so that
Speaker 1: you can never even get there. Not that you can't escape,
Speaker 1: but that you can never even get there, and they're
Speaker 1: motivated by this sort of theoretical calculation that Roger Penrose did.
Speaker 1: He thought about like the way space is organized around
Speaker 1: a black hole, and he carves it up into these coordinates,
Speaker 1: and there's the coordinates near the black hole and coordinates
Speaker 1: in the black hole, and the way that he sort
Speaker 1: of laid it out on a piece of paper, there's
Speaker 1: like a blank spot. It suggests that there could be
Speaker 1: a place in space where particles could go from there,
Speaker 1: but because of the shape of the event horizon near
Speaker 1: a black hole, they could never get in there. And
Speaker 1: so it's sort of conceptually trying to like cross the
Speaker 1: T or dot the I to say like, well, if
Speaker 1: it's here on the piece of paper, maybe it also
Speaker 1: actually exists out there in the universe.
Speaker 2: And so the thing that would be keeping you from
Speaker 2: getting there is that like some force is pulling you
Speaker 2: too hard for you to be able to move into
Speaker 2: that space. Is that the mmm?
Speaker 1: Okay, yeah, exactly. So imagine, for example, there's a white
Speaker 1: hole somewhere in space and you have a laser and
Speaker 1: you shoot your laser at the white hole and you think, well,
Speaker 1: why can't my photon go into the white hole. Well,
Speaker 1: the reason it's a white hole is that space is
Speaker 1: curved around it, and so if you try to shoot
Speaker 1: your laser at the white hole, you'll find that it
Speaker 1: doesn't go in. It bends through curved space and goes
Speaker 1: in another direction. The same way, for example, if you
Speaker 1: shoot a laser beam near a black hole, it can
Speaker 1: bend around the black hole and go in some other direction. Right,
Speaker 1: we know that curved space can change the path of
Speaker 1: photons than any other particle, right, that's what curved space does.
Speaker 1: That's why curved space is so awesome, because it can
Speaker 1: even change the path of photons, which have no mass,
Speaker 1: they technically feel no gravity. But that's why it's important
Speaker 1: to think about gravity as curvature of space, changing the
Speaker 1: path of particles that flow through it. So, now, just
Speaker 1: arrange space to have curvature so that no matter what
Speaker 1: direction you shoot a photon from, it basically glances off.
Speaker 1: It's like the perfect armor you have, like space as
Speaker 1: a shield, so that anything that comes near you just
Speaker 1: pick ricochets off and goes in another direction. It's not
Speaker 1: like a wall there. It's not a force, it's the
Speaker 1: curvature of space itself. That you've ranged in this way
Speaker 1: that photon glance off and go in another direction.
Speaker 2: What would you need to have for that to happen?
Speaker 2: By making sense, how would that come about?
Speaker 1: Yeah, you're perfectly making sense, And nobody really knows the
Speaker 1: answer to that question because it's not really a solid
Speaker 1: theoretical concept. Nobody knows how a white hole could form.
Speaker 1: There's this theory that if there was a black hole
Speaker 1: which had existed forever, an eternal black hole, not one
Speaker 1: that was created. We we have, like a star that
Speaker 1: collapses and forms a black hole, but a black hole
Speaker 1: which it somehow existed forever, even though we think the
Speaker 1: universe has a finite age in general relativity imagined somehow
Speaker 1: an infinitely old universe that doesn't have a big bang
Speaker 1: in the heart of it. So you could have eternal
Speaker 1: black holes. These things somehow would also have white holes
Speaker 1: attached to them, And that's essentially what why it is
Speaker 1: asking about. Somehow, if you have an eternal black hole
Speaker 1: formed in such a way that it's always existed, right
Speaker 1: so I guess, not formed just like exists, then it
Speaker 1: naturally has a region of space which is also a
Speaker 1: white hole. So we don't know how to make one.
Speaker 1: But if an eternal black hole existed, then the theory
Speaker 1: suggests they would also be a paired with it, a
Speaker 1: white hole, and the two are connected. So the singularity
Speaker 1: of the black holes connected to the edge of this
Speaker 1: white hole in such a way that things that fall
Speaker 1: into the black hole could come out the white hole.
Speaker 2: But only if the black hole always existed.
Speaker 1: Only if the black hole always existed. So we don't
Speaker 1: know how to make this, but it is compatible with
Speaker 1: general relativity. It's very similar situation to the other mind
Speaker 1: bending concept in general relativity of wormholes. Wormholes are the
Speaker 1: connection between two points in space. The idea that like,
Speaker 1: all right, I'm here and I want to be an
Speaker 1: Alpha centauri, but I don't want to fly through four
Speaker 1: light years of space to get there, because the speed
Speaker 1: of light means that would take forever. What if instead
Speaker 1: of flying through space, there was just like a connection
Speaker 1: between my spot in space and their spot in space,
Speaker 1: so I could just like step through a portal to
Speaker 1: go from here to there. That's allowed in general relativity.
Speaker 1: That's called a wormhole.
Speaker 2: I think one of my biggest disappointments with physics, or
Speaker 2: maybe physicists, is that you all haven't figured that out yet,
Speaker 2: because those wormholes would be great, and I.
Speaker 1: Want to get to Wyatt's question about white holes, but
Speaker 1: first let's take a quick break. Okay, we're back and
Speaker 1: we're answering listener questions about black holes and white holes
Speaker 1: and wormholes and all the holes that they make in
Speaker 1: your brain.
Speaker 2: I just finished reading auror U by Kim Stanley Robinson,
Speaker 2: and I think interplanetary travel would be super cool but
Speaker 2: probably will mostly just kill people unless we can figure
Speaker 2: out something like the wormholes. So anyway, get on it please.
Speaker 1: Heck, I even want wormholes for like going to work
Speaker 1: or going to the grocery store. Like imagine you don't
Speaker 1: need a shopping cart and then load it into your car,
Speaker 1: and then unload it from your car and load in
Speaker 1: your fridge. You could just stand at your fridge, open
Speaker 1: a wormhole to the grocery store and just take stuff
Speaker 1: off the shelf directly into your fridge.
Speaker 2: Theft would be a much bigger problem in a world
Speaker 2: with that technology.
Speaker 1: That's an engineering challenge once we figure out the physics.
Speaker 1: But yes, wormholes are definitely something we aspire to, and
Speaker 1: the amazing thing is that they're not ruled out in
Speaker 1: general relativity they are allowed, but again we don't know
Speaker 1: how to make them. We can say that a wormhole
Speaker 1: can exist in the universe general relativity doesn't forbid it,
Speaker 1: but we don't know how to go from a universe
Speaker 1: without a wormhole to a universe with a wormhole and
Speaker 1: still follow all the laws of general relativity. It's like saying, oh, yes,
Speaker 1: that house would hold itself up. We have no idea
Speaker 1: how to construct it, so it also holds itself up
Speaker 1: while it's half built. Right. We don't have a path
Speaker 1: to go from a no wormhole universe to a wormhole universe,
Speaker 1: and in the same way, we don't know how to
Speaker 1: go from a universe without a white hole black hole
Speaker 1: pair connected by a wormhole to a universe that has one.
Speaker 1: We can say if it exists in the universe and
Speaker 1: has always existed somehow weirdly in a way that makes
Speaker 1: no sense, then that's fine with the laws of physics,
Speaker 1: But we don't know how to go from not having
Speaker 1: one to having one. How to basically build a white hole?
Speaker 2: Ugh uugh is all I could think.
Speaker 1: This is complicated.
Speaker 2: Let's imagine a white hole does exist out there. What
Speaker 2: would you see that would make you be like, oh
Speaker 2: my gosh, we actually found one, and would it be
Speaker 2: something emerging? Like you put your laser out there, the
Speaker 2: laser goes around the bend of space time, but then
Speaker 2: a laser comes back out through the spot that you
Speaker 2: tried to get it into but it couldn't and then
Speaker 2: you were like, whoa something came out of the white hole.
Speaker 2: That would be evidence if you saw something like that.
Speaker 1: Yeah, that's a pretty good short version of it. Let's
Speaker 1: unpack it a little bit. Like one way to discover
Speaker 1: a white hole is to see evidence of a place
Speaker 1: in space that nothing can enter. The same way we
Speaker 1: look for a black hole as a region of space
Speaker 1: that's emitting no light, no radiation. We know this tremendous curvature,
Speaker 1: but we don't know what's there, and it's not glowing
Speaker 1: in any way. And so that's how we forget, example,
Speaker 1: discovered black holes near the center of the galaxy. We
Speaker 1: see things zooming by, so we know there's a lot
Speaker 1: of mass in a very small space, but we can't
Speaker 1: actually see anything. In the same way, we might discover
Speaker 1: white hole by finding some location in space where weirdly
Speaker 1: photons get bent around it. The more direct evidence would
Speaker 1: be a place in space that's emitting light with no
Speaker 1: other explanation. Right, if laser beams are shooting out of
Speaker 1: some place in space and there's no known origin for it,
Speaker 1: that's like a great analogy to you know, laser beams
Speaker 1: are being eaten by this black hole. So if laser
Speaker 1: beams are just being generated by space, that would be
Speaker 1: really fascinating clue about white holes. The problem is though,
Speaker 1: that we don't know that white holes would have to
Speaker 1: generate radiation, right, Like, the thing about a white hole
Speaker 1: is that nothing can enter it, but that also means
Speaker 1: that nothing has to leave it, right, Things can leave it,
Speaker 1: but they will only leave the white hole if they're
Speaker 1: in there. So you could have like a white hole
Speaker 1: that's empty. Nothing can enter it, and so things could
Speaker 1: leave it if they were there, but there's nothing in there,
Speaker 1: so it's basic invisible. And so it's possible to have
Speaker 1: white holes that are like quiet that don't emit anything.
Speaker 1: But if you have a white hole that's connected to
Speaker 1: a black hole, and I think this is why it's questioned
Speaker 1: if black holes and white holes are connected, then stuff
Speaker 1: could fall into the black hole and be connected to
Speaker 1: the white hole. And come out the other side of
Speaker 1: the white hole, and that would be basically like a wormhole.
Speaker 1: But if you one directional right, you couldn't go back
Speaker 1: in the white hole. So you take that trip to
Speaker 1: Alpha Centauri, you're in Alpha Centauri unless there's another black
Speaker 1: hole white hole pair going the other direction.
Speaker 2: And when you get to Alpha Centauri, are you still spaghettified.
Speaker 1: Yeah, there's a whole lot more to figure out there
Speaker 1: from an engineering perspective, because these wormholes are a minuscule
Speaker 1: you know, they're particle sized, and so to make them
Speaker 1: larger requires all sorts of exotic technology. We definitely do
Speaker 1: not have like particles that radiate energy, negative mass particles
Speaker 1: that essentially expand space the way dark energy does. We
Speaker 1: don't know if that's possible at all. And as you
Speaker 1: approach the mouth of this black hole, you would still
Speaker 1: be spagetified. So in order to be safe, you'd want
Speaker 1: the black hole to be really, really large, because larger
Speaker 1: black holes have weaker tidal forces near their edge. So
Speaker 1: there's a lot to figure out before you're willing to
Speaker 1: send your kids to the store using a black hole
Speaker 1: white hole pair, for sure, But in principle it is
Speaker 1: theoretically possible, but again, we don't know how to build it,
Speaker 1: so it's really a ways off. And it might turn out,
Speaker 1: in a fuller understanding of gravity that the thing makes
Speaker 1: no sense at all, that white holes don't exist. It
Speaker 1: might just be a feature of our classical theory of
Speaker 1: general relativity.
Speaker 2: Oh, physics, you're so crazy.
Speaker 1: The thing I love about this question is that it highlights, like,
Speaker 1: really how little we understand about the basic nature of
Speaker 1: space and time. You know, Newton thought about space and
Speaker 1: time is absolute and infinite, just like the backdrop of
Speaker 1: the universe. But we now know that it's more interesting
Speaker 1: than that. We know that space can twist and ripple
Speaker 1: and curve and expand and do all sorts of funny things,
Speaker 1: but we still don't really understand what space is. We
Speaker 1: know that our current theory general relativity has got to
Speaker 1: be incomplete, and it's got all these wacko predictions, some
Speaker 1: of which come true, like black holes, and other things
Speaker 1: like singularities inside black holes we're pretty sure are wrong,
Speaker 1: and the other weird features like white holes were like, man,
Speaker 1: that is bonkers. Let's figure this all out. But in
Speaker 1: one hundred years or five hundred years, when we have
Speaker 1: figured this all out, people are going to look back
Speaker 1: and think, wow, we really didn't understand anything back in
Speaker 1: twenty twenty four.
Speaker 2: So the good news is that there's lots of job
Speaker 2: security in physics because there's lots of work left to do.
Speaker 1: It turns out the universe is a pretty big puzzle.
Speaker 1: So thank you very much. Why to write again with
Speaker 1: your particular question about physics. We want to hear from
Speaker 1: all of you forever and deep into the infinite future.
Speaker 1: If you have questions about the nature of the universe,
Speaker 1: please write to us two questions at Danielanjorney dot com.
Speaker 1: But just to wrap up why, the answer is, white
Speaker 1: holes are a very fuzzy theoretical concept, not even every
Speaker 1: theorist that thinks that they make sense theoretically. But if
Speaker 1: they do exist, and they have always existed in the universe,
Speaker 1: then it's possible that they are connections between black holes
Speaker 1: and white holes, and that you could go into a
Speaker 1: black hole and emerge from a white hole. But Kelly
Speaker 1: would have to sign off on a permission slip telling
Speaker 1: you that it's safe. First.
Speaker 2: I'm only signing off on my kids' permission slips. Everybody
Speaker 2: else can make their own decisions. I'm only holding back
Speaker 2: my children from exploring the universe.
Speaker 1: You don't feel some sort of in loco parentis obligation
Speaker 1: as a podcast host.
Speaker 2: Hosting a podcast doesn't make me feel like I have
Speaker 2: any obligations whatsoever. But I do feel like I need
Speaker 2: to let my kids make their own choices eventually, but
Speaker 2: not yet.
Speaker 1: All right, everybody you heard that you're on your own,
Speaker 1: make your own decisions. All we can do is advise you.
Speaker 2: That means you can't sue us.
Speaker 1: That's really what it means, Yes, chemists or not, you
Speaker 1: can't sue us. Well. Thanks very much for joining us
Speaker 1: on this black and white episode about drawing boundaries between
Speaker 1: regions in space. Thank you Why for running in, Thank
Speaker 1: you Kelly for joining me, and thanks everybody for thinking
Speaker 1: about the universe.
Speaker 2: Thanks Daniel.
Speaker 1: Tune in next time for more science and curiosity. Come
Speaker 1: find us on social media, where we answer questions and
Speaker 1: post videos. We're on Twitter, Discord, Insta, and now TikTok.
Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain
Speaker 1: the Universe is a production of iHeartRadio. For more podcasts
Speaker 1: from iHeartRadio, visit the iHeartRadio app. Apple podcasts, or wherever
Speaker 1: you listen to your favorite shows.