September 23, 2025 • 19 mins
Daniel and Kelly answer a question about how white holes are connected to black holes.
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Speaker 1 (00:07):
Hey, Kelly, we love physics on the podcast, don't we.
Speaker 2 (00:10):
Yes, especially when it's not physics that's threatening the lives
of my children.
Speaker 3 (00:14):
Yes.
Speaker 1 (00:16):
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.
Speaker 2 (00:26):
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.
Speaker 1 (00:40):
Wait are you a pro chemistryite? Is that what's happening here?
Speaker 2 (00:43):
It's just it's not so black and white, That's what
I'm saying.
Speaker 1 (01:03):
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.
Speaker 2 (01:13):
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.
Speaker 1 (01:29):
No, you're right, all of science is a big, squishy endeavor,
but chemistry is on the other side of that line.
Speaker 2 (01:34):
Yeah. No, we hate chemistry. That's fine. Oh, kem, like
maybe the hardest thing I've ever done. Like, OKM, then childbirth.
Speaker 1 (01:45):
You shouldn't do either of those without anesthetic.
Speaker 2 (01:47):
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.
Speaker 1 (01:57):
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.
Speaker 2 (02:07):
Yeah. Yeah, No, it makes you feel better too sometimes,
so you just need you've got to go for it.
Speaker 1 (02:13):
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.
Speaker 2 (02:22):
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.
Speaker 1 (02:32):
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
(02:53):
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.
(03:13):
We will still answer your questions.
Speaker 2 (03:15):
That's right, nothing can stop us.
Speaker 1 (03:17):
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.
Speaker 2 (03:35):
And we must be out of practice because otherwise we
wouldn't have threatened the chemists.
Speaker 1 (03:41):
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.
Speaker 3 (03:55):
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.
Speaker 2 (04:19):
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
(04:40):
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?
Speaker 1 (04:50):
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
(05:11):
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
(05:32):
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
(05:52):
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
(06:14):
in space where there are no paths to it, instead
of no paths out of it.
Speaker 2 (06:19):
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.
Speaker 1 (06:25):
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
(06:47):
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
(07:09):
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
(07:30):
actually exists out there in the universe.
Speaker 2 (07:33):
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?
Speaker 1 (07:46):
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
(08:07):
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,
(08:29):
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
(08:50):
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.
Speaker 2 (09:03):
What would you need to have for that to happen?
By making sense, how would that come about?
Speaker 1 (09:09):
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
(09:31):
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
(09:52):
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
(10:14):
white hole in such a way that things that fall
into the black hole could come out the white hole.
Speaker 2 (10:21):
But only if the black hole always existed.
Speaker 1 (10:24):
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
(10:46):
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.
Speaker 2 (11:02):
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.
Speaker 1 (11:12):
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
(11:34):
and wormholes and all the holes that they make in
your brain.
Speaker 2 (11:37):
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.
Speaker 1 (11:51):
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.
Speaker 2 (12:07):
Theft would be a much bigger problem in a world
with that technology.
Speaker 1 (12:12):
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
(12:34):
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.
(12:56):
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?
Speaker 2 (13:09):
Ugh uugh is all I could think.
Speaker 1 (13:11):
This is complicated.
Speaker 2 (13:15):
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.
(13:37):
That would be evidence if you saw something like that.
Speaker 1 (13:40):
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,
(14:00):
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
(14:23):
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
(14:44):
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.
(15:06):
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
(15:26):
Alpha Centauri, you're in Alpha Centauri unless there's another black
hole white hole pair going the other direction.
Speaker 2 (15:32):
And when you get to Alpha Centauri, are you still spaghettified.
Speaker 1 (15:36):
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
(15:57):
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
(16:20):
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.
Speaker 2 (16:35):
Oh, physics, you're so crazy.
Speaker 1 (16:38):
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
(17:00):
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
(17:21):
figured this all out, people are going to look back
and think, wow, we really didn't understand anything back in
twenty twenty four.
Speaker 2 (17:27):
So the good news is that there's lots of job
security in physics because there's lots of work left to do.
Speaker 1 (17:34):
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
(17:57):
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.
Speaker 2 (18:15):
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.
Speaker 1 (18:24):
You don't feel some sort of in loco parentis obligation
as a podcast host.
Speaker 2 (18:28):
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.
Speaker 1 (18:38):
All right, everybody you heard that you're on your own,
make your own decisions. All we can do is advise you.
Speaker 2 (18:43):
That means you can't sue us.
Speaker 1 (18:46):
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.
Speaker 2 (19:00):
Thanks Daniel.
Speaker 1 (19:02):
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
(19:25):
from iHeartRadio, visit the iHeartRadio app. Apple podcasts, or wherever
you listen to your favorite shows.
Hey, Kelly, we love physics on the podcast, don't we.
Speaker 2 (00:10):
Yes, especially when it's not physics that's threatening the lives
of my children.
Speaker 3 (00:14):
Yes.
Speaker 1 (00:16):
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.
Speaker 2 (00:26):
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.
Speaker 1 (00:40):
Wait are you a pro chemistryite? Is that what's happening here?
Speaker 2 (00:43):
It's just it's not so black and white, That's what
I'm saying.
Speaker 1 (01:03):
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.
Speaker 2 (01:13):
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.
Speaker 1 (01:29):
No, you're right, all of science is a big, squishy endeavor,
but chemistry is on the other side of that line.
Speaker 2 (01:34):
Yeah. No, we hate chemistry. That's fine. Oh, kem, like
maybe the hardest thing I've ever done. Like, OKM, then childbirth.
Speaker 1 (01:45):
You shouldn't do either of those without anesthetic.
Speaker 2 (01:47):
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.
Speaker 1 (01:57):
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.
Speaker 2 (02:07):
Yeah. Yeah, No, it makes you feel better too sometimes,
so you just need you've got to go for it.
Speaker 1 (02:13):
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.
Speaker 2 (02:22):
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.
Speaker 1 (02:32):
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
(02:53):
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.
(03:13):
We will still answer your questions.
Speaker 2 (03:15):
That's right, nothing can stop us.
Speaker 1 (03:17):
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.
Speaker 2 (03:35):
And we must be out of practice because otherwise we
wouldn't have threatened the chemists.
Speaker 1 (03:41):
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.
Speaker 3 (03:55):
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.
Speaker 2 (04:19):
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
(04:40):
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?
Speaker 1 (04:50):
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
(05:11):
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
(05:32):
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
(05:52):
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
(06:14):
in space where there are no paths to it, instead
of no paths out of it.
Speaker 2 (06:19):
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.
Speaker 1 (06:25):
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
(06:47):
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
(07:09):
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
(07:30):
actually exists out there in the universe.
Speaker 2 (07:33):
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?
Speaker 1 (07:46):
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
(08:07):
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,
(08:29):
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
(08:50):
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.
Speaker 2 (09:03):
What would you need to have for that to happen?
By making sense, how would that come about?
Speaker 1 (09:09):
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
(09:31):
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
(09:52):
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
(10:14):
white hole in such a way that things that fall
into the black hole could come out the white hole.
Speaker 2 (10:21):
But only if the black hole always existed.
Speaker 1 (10:24):
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
(10:46):
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.
Speaker 2 (11:02):
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.
Speaker 1 (11:12):
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
(11:34):
and wormholes and all the holes that they make in
your brain.
Speaker 2 (11:37):
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.
Speaker 1 (11:51):
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.
Speaker 2 (12:07):
Theft would be a much bigger problem in a world
with that technology.
Speaker 1 (12:12):
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
(12:34):
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.
(12:56):
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?
Speaker 2 (13:09):
Ugh uugh is all I could think.
Speaker 1 (13:11):
This is complicated.
Speaker 2 (13:15):
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.
(13:37):
That would be evidence if you saw something like that.
Speaker 1 (13:40):
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,
(14:00):
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
(14:23):
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
(14:44):
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.
(15:06):
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
(15:26):
Alpha Centauri, you're in Alpha Centauri unless there's another black
hole white hole pair going the other direction.
Speaker 2 (15:32):
And when you get to Alpha Centauri, are you still spaghettified.
Speaker 1 (15:36):
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
(15:57):
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
(16:20):
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.
Speaker 2 (16:35):
Oh, physics, you're so crazy.
Speaker 1 (16:38):
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
(17:00):
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
(17:21):
figured this all out, people are going to look back
and think, wow, we really didn't understand anything back in
twenty twenty four.
Speaker 2 (17:27):
So the good news is that there's lots of job
security in physics because there's lots of work left to do.
Speaker 1 (17:34):
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
(17:57):
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.
Speaker 2 (18:15):
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.
Speaker 1 (18:24):
You don't feel some sort of in loco parentis obligation
as a podcast host.
Speaker 2 (18:28):
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.
Speaker 1 (18:38):
All right, everybody you heard that you're on your own,
make your own decisions. All we can do is advise you.
Speaker 2 (18:43):
That means you can't sue us.
Speaker 1 (18:46):
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.
Speaker 2 (19:00):
Thanks Daniel.
Speaker 1 (19:02):
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
(19:25):
from iHeartRadio, visit the iHeartRadio app. Apple podcasts, or wherever
you listen to your favorite shows.
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