Kind: captions
Language: en
If just magically you snapped your
fingers and the sun was a black hole, we
could just orbit completely safely. In
fact, you can't get within a million and
a half kilometers of the sun, right?
It's the center of the sun. You'd be
incinerated. So, the sun's much more
hostile than the black hole. I could get
30 kilometers outside a black hole.
>> That is so cool.
>> Yeah. I could get right on top of it.
>> Star sun
>> Yeah.
>> is more malignant than black hole sun.
>> Yeah, for sure. You could orbit very
close to a black hole and be perfectly
safe if you had your your own little
unit, nice little space station with all
your amenities.
[Music]
What's up y'all? Today I sat down with
Jana 11. She's an astrophysicist who's
an expert on black holes. And who
doesn't want to hear about black holes?
You might have seen her hosting the Nova
film Black Hole Apocalypse, and she's
written a bunch of books on the subject,
including her latest Black Hole survival
guide. She's a professor of physics and
astronomy at Barnard College and the
founding scientific director at Pioneer
Works, which is this really cool artist
and science-led nonprofit cultural
center. We talked about some of the
biggest misconceptions people have about
black holes, how weird black holes can
be, and how scientists actually go about
detecting them. This conversation bent
my spacetime. Now, if you feel attracted
to this content, gravitationally or
otherwise, please rate us, leave a
review, or drop us a comment. Make sure
to subscribe so you can catch every
episode. Your support means everything
and helps us reach more curious minds
like yours. Now, let's get it.
>> Welcome, Jana.
>> Thank you. I'm glad to be here.
>> Yeah. So, I did a little background
research.
>> Yeah.
>> And realize that you and I are born in
the same year.
>> No way. You're not allowed to tell
people that.
>> Wait. We're both like 26.
>> So, here here is something that I wonder
if we have in common since we're from
the same generation. When I was in high
school, yeah, and college, and I was
asked to write an essay, I realized
pretty quickly that if I wrote my essay
around about black holes,
>> I would get an A cuz the teacher had no
idea. In fact, I did my senior thesis on
uh energy extraction for a black hole.
So, did you
>> Okay.
>> use the same technique.
>> Was this high school?
>> No, no, no. In high school, just that
they exist.
>> Okay. Yeah.
>> I found a book in the library at college
and so I'm like, ah, yeah. So, you use
the same trick or
>> Oh, you know, I think I just fell into
black holes. It's, you know,
metaphorically speaking.
>> Okay. Is that like pun intended or
>> uh Yeah. I mean, I didn't start studying
science until about halfway through
college.
>> Oh,
>> I didn't start studying physics. Okay.
Were you a science major?
>> Math and physics. No, I was a philosophy
major. I was so misguided.
>> Well, I don't know. That's
>> completely No, deep thinking. It's the
big questions. Exactly. So, that's
really it. It's the big questions. And
then I kind of accidentally discovered
physics and realized that this had this
transcendent power and that it was true
for everybody. Nobody was arguing about
what somebody meant anymore. Nobody's
like, "What did Einstein mean? I can't
because you can learn it and it's
yours." I thought that was incredible.
And you can teach it to somebody else
and it can propagate through the world
that way. I was completely overwhelmed
with the power of that. Whereas people
were still arguing about philosophers
from 400 years ago,
>> what they might have meant.
I just thought, you know, it could not
have been that important then.
>> Well, yeah. Yeah. Or they don't know
what they're doing, right? There isn't
an answer. Cuz that that struck me what
you just said.
>> Um you know, when you're young and
you're having these debates uh about
religion and politics, right? I I would
point out to people, I was like, "Yeah,
you know what? There's something about
science that's different from religion."
Yeah.
>> And that is is that it's the same
everywhere on the planet. It's not like
you go to Saudi Arabia or you go to
India or you go to China and suddenly
there's a different version. Right.
>> Absolutely. Rammenujin can come out of a
small town and another continent and
reinvent ways of calculating pi.
>> It's just true.
>> Yeah, it's just true. It just is.
>> And yeah, so I do love that about math
and physics.
>> So let's get into black holes,
>> right?
>> So when when we think about a black
hole,
>> I think that uh you know, in a second
we're going to define what it is, but I
think one of the things that
>> is not appreciated is
>> how small they are. So, like if the sun
were a black hole, it would be something
like two miles or something.
>> Yeah. I mean, I'm still stuck in
kilometers. It would be six kilometers
across.
>> Oh, kilome across.
>> I give that to me. Miles, I don't know.
>> Yeah. So, if you saw an asteroid, that's
six. That's a tiny asteroid.
>> A tiny object that would fit inside
Manhattan.
>> So, you wouldn't even see it as you're
approaching Manhattan, right? If you
were like out in space and stars all
around, you wouldn't even notice a
little a sunsized black hole. Yeah,
black holes are notoriously hard to
detect because you can't resolve them.
They're too tiny.
>> Um, think of a star on the sky twinkling
and those are millions of kilometers
across, millions of times bigger and
they're just a twinkling speck. How are
you going to see something emitting no
light, right?
>> Reflecting no light that's only six km
across at such a great distance. You're
not.
>> You're not even at a close distance. And
we people I think were very surprised
that we had never taken a picture of a
black hole before this century. So when
we were talking about detecting black
holes was all indirect,
>> very well deduced, very compelling, very
convincing, but we didn't have a picture
of one, right?
>> And that's only been in the last few
years.
>> Let's get into
>> the reputation of black holes because
you know if you watch Interstellar,
>> you know that they can do some nasty
things like they can make you older than
your children,
>> right? Wait. Yeah. Younger than your
children. Younger than your children.
Then there's this notion that they just
suck everything in. So once upon a time,
ABC News called me science's greatest
hype man.
>> But you're the PR agent for black holes.
So are they as bad?
>> Yeah, I think they get a bad reputation.
So they're not these weapons of
destruction that they're portrayed to
be. I like to do a little myth busting
about black holes. One of the one of the
first myths is that black holes will
destroy everything in the universe. And
um actually they're you leave them
alone, they'll leave you alone. You
know, they're quite
>> they're quite benign in a lot of ways.
So
>> if the sun were to turn into a black
hole tomorrow, I mean, it would be
terrible. Um we would lose our life
force. It would get cold.
>> But uh our orbit would be would be
pretty much the same. Our orbit would
would be fine. Right.
>> So, we wouldn't get sucked into the sun.
>> So, the planets wouldn't get Mercury
wouldn't get sucked in.
>> No, we I mean, yeah. If just magically
you snapped your fingers and the sun was
a black hole, we could just orbit
completely safely. In fact, the sun is a
million and a half kilometers uh across,
right? Um and so you you can't get
within a million and a half kilometers
of the sun, right? It's the center of
the sun. You'd be it's you'd be
incinerated. So the sun's much more
hostile than the black hole. I could get
30 kilometers outside a black hole.
>> That is so cool.
>> Yeah, I could get right on top of it.
>> Star sun,
>> yeah,
>> is more malignant than black hole sun.
>> Yeah, for sure. You could orbit very
close to a black hole um and be
perfectly safe if you had your your own
little unit, nice little space station
with all your amenities. You could just
sit there and watch it
>> unfold. You just flipped the universe,
right? Because everybody think black
hole, star, right? Which hurts most
most,
>> right? You think black hole. Yeah. But
the answer is no. Star.
>> No. And in fact, the bigger the black
hole, the kind of safer you are. Um
>> if you if you fall across a very big
black hole, you won't even you won't
feel squeezed, stretched, torn apart,
spaghettified. None of that stuff will
happen to you until you start to get
towards the center.
>> Until you get to the very
>> Yeah. I mean, then it gets pretty bad. I
mean, there's no Right. There's no
surviving.
>> Well, it depends. No. What if you flex?
>> It's going to be stronger than you.
>> Is it stronger than your molecular bomb
atomic
>> bomb? Right. But think about you just
flex. Think about how weak the earth is.
The entire mass of the earth. That whole
gravitational field of the entire planet
is pulling on you right now. But you I
can lift my little arm, you know?
>> Right. Yeah. You're strong enough to to
go in the opposite direction.
>> Look at me. Right.
>> But if you were if you if you were on a
neutron star, which is a dead star that
did not quite become a black hole, it is
a dense object.
>> Um but it does not have an event
horizon. Light can escape. We do see
neutron stars with light.
>> Um but they are so dense um that let's
say they're 20 kilometers across instead
of just six or something.
They're still so dense that you'd be
liquefied because you could not lift
your arm up. You could you're atoms. You
could not flex. You could not stay bound
together. Just gravity would totally
>> um uh pull you apart.
>> So several months back last fall, I got
to ride the vomit comet, the zerog
plane.
>> Oh wow.
>> And zero G was fascinating, but what I
found really fascinating was when you
were going up and you were at 2 G's,
>> right?
>> I never experienced that, you know, and
Yeah.
>> It's a lot harder to move around. Yeah,
it's hard to move around,
>> right? When you increase the the
equivalent acceleration.
>> Yeah. So, because I started puking, I
was no longer lying flat. I was back in
a chair strapped in with my back. It
>> was terrible. That's why I won't do it.
>> But I got to do all these gravity
experiments
>> back there. And that was so weird to me.
Weirder than
>> than the zero G. Well, zero G I can
achieve by jumping off the table,
>> right?
>> It just doesn't last very long. So this
was Einstein called this the happiest
thought of his life when he realized you
know I feel heavy on this chair you know
I can't get out of bed or that's not
gravity that's actually you pushing off
the atoms
>> in your chair in your bed this idea of
the thought experiment removing effects
that don't belong in your experiment he
said let's just remove the chair let's
remove the floor let's remove the ground
what happens then you're just falling
>> and he called it freef fall
>> and you feel weightless
>> he coined that phrase
>> oh my god You know, I've never thought
about it. He didn't say freef fall.
>> Now we need Now we need a history check.
>> Yeah. Now we need because you know
sometimes you you you learn what where
the phrase came from. It's typically
Shakespeare, but
>> right maybe it was Shakespeare or Dante.
>> Yeah. Or Flavor Flave.
>> Well, I I would have thought it was
Einstein, but I guess I've never
actually
>> checked. But the the concept that you
will experience weightlessness if you
remove everything
>> except gravity is very profound. So zero
G's, this idea that I have to go up in
Blue Origin and break the Carmen line
where the atmosphere thins out in order
to experience no gravity. That's
nonsense. That makes no sense at all.
>> Um
>> all that's happened is you're falling
and you get more fall out of a greater
height than if you do if you jump off
the table
>> and you crash on the floor immediately.
It lasts longer and you get to do a
little parabola right before you have to
scoop up again. But you can get zero G
under uh earthly circumstances. You when
you're at the Carmen line where things
like Blue Origin are skirting, you are
absolutely being pulled on by the Earth.
You do not want to drop like a stone and
hit the surface of the Earth because you
will, right? You're not going to drift
off. So the International Space Station
is another great example. They're very
much under the pole of the Earth.
>> Otherwise, they just
>> Yeah. They're They're not floating away.
They're bound to the Earth. They keep
falling towards the Earth. In fact,
>> just missing it.
>> They're just missing it.
>> Yeah,
>> it's exactly what they're doing. They're
cruising so fast, 17,500 mph
>> um that they clear the horizon. They
just never actually crash into the
crust.
>> Yeah.
>> But they are um very much experiencing
gravity or gravity and if you were to
stop it from cruising at 17,500 miles an
hour, it would drop like a stone.
>> So before we go further, let's
>> define what a black hole is. Let's do
black hole 101,
>> right? tell the audience how you define
a black hole.
>> Yeah, I think there's many different
ways to approach it. Yeah. Most people
will say um an object so dense that not
even light can escape. Yeah.
>> And there's good things about that
description. There's really bad things
about that description. So, a good thing
about the description is that it
captures one of the most fundamental
attributes of the black hole and that is
that it goes completely dark.
>> Yeah.
>> Nothing will ever escape, not even
light. And so that part is the crux in
some sense of what a black hole is.
>> We we say that around the black hole we
circumscribe it with the region around
which light can no longer escape. We
call that the event horizon.
>> Yeah.
>> What's bad about that description is
that there's nothing there. There's no
dense object
>> at the
>> at the event horizon. Right. So I don't
like the image of a thing,
>> you know, a thing, right? That's just
really really dense. Now, it's true
often black holes are made by dense
things on their way out,
>> right? Yeah. Yeah.
>> But at the event horizon where the light
is forced to fall in, there's just empty
space.
>> So, the black hole is just a spaceime,
>> a volume of space,
>> right? It's just uh it's more of a place
in some sense than a thing. Yeah. So, I
can go up to this event horizon and if
I'm trying to shine a flashlight and I'm
shining light, the light as I get closer
will be trapped in orbit
>> at some point around the black hole. And
then eventually as I get closer, it
won't even be able to do that anymore.
It's just going straight in.
>> And it's just going straight in as am I.
>> Right.
>> But there's no I don't bump into any
matter. I don't smack into any surface.
I just sail across an empty space.
>> Yeah. So what are black holes?
>> Disappointing.
>> Well, I mean, honestly, you might not
even notice anything bad was happening
to you. Yeah.
>> It would be no more dramatic in some
sense than stepping into the shadow of a
tree. It's just a shadow.
>> So, suddenly,
>> yeah. But cut off.
>> Yeah. So, so if you say what is a black
hole, I would say the black hole is
really the event horizon.
>> Okay.
>> It's this horizon beyond which
>> light cannot escape. If you're looking
out, you can see light coming in though,
right?
>> That's right. So, if you fall in, it can
be bright on the inside. Uh because the
light can fall in from all the stars
shining, all the galaxies, all of that
can fall in behind you and you can see
all of this happening. Um so, it can be
right on the inside, it's just dark on
the outside.
>> So, let's do an example.
>> It's a oneway, it's a one-way uh
transition.
>> So, suppose the light's coming in toward
you and you hold up a mirror
>> to reflect the light back out. What
happens?
>> It's tricky because we're standing on
the outside of a black hole, let's say.
>> Yeah.
>> And we're throwing that light in and
your companion has fallen in right ahead
of you.
>> We are imagining that interior to that
event horizon that that is a spatial
direction. I mean all our intuition says
it. It says it says once you cross
inside there's a spatial direction
pointing towards the center of a point
in space.
>> But space and time are relative.
>> Okay. And to the observer who has fallen
inside, they are very rotated relative
to your space and time,
>> what they're calling space and what
you're calling space are now very
misaligned.
>> And so that direction for the observer
who fell in that points towards what we
sometimes call the singularity.
>> Yeah.
>> That is a direction in time now,
>> right? So the person falling in can no
more bounce the light that comes in
behind them back out than they can
bounce the light backward in time.
>> Wow.
>> So there is no such option to do that.
Nor would they imagine such an option
because to them they and the light are
continuing to fall forward in time
>> and that is driving them in the same
direction towards the center.
>> So let me let me create an tricky. I'm
not saying
>> is it like refraction like where you see
the spoon in the water and so this was
going in that direction but now it looks
like it's
>> somewhere else disconnected but it's
more extreme.
>> Yeah. I mean
>> so the event horizon would be like the
surface of the water.
>> Yeah. I I would say um there is you can
bounce the light in different spatial
directions just that direction is no
longer space at all. So, uh, you know,
it really is
>> it really is, um, in your past,
>> the event horizon. So, there's no even
turning around anymore. And, you know,
the light can fall in behind you. You
can see things, but you can't claw your
way back, nor can you send anything back
that way. Now, if you could travel back
in time, we could get tricky and start
to talk about things like that. But then
you're doing stuff on the outside.
That's pretty crazy, too.
>> So, is there So, we talk about the
strong gravity. Yeah. Yeah.
>> And so we usually speak in terms of
space, curvature of space and time.
>> So is it possible to
>> curve time in such a way that you move
backwards in time?
>> Oh well, I can definitely um move to for
instance someone's future
>> by by rotating space and time or bending
space and time. Um, we don't yet know of
a way for for me to travel to my future.
>> But I can travel to yours.
>> I could go in a rocket ship travel near
the speed of light.
>> I You said we're born in the same year.
I could come back 10 years your time,
>> 2 minutes my time, right? I mean,
technologically, I can't do it. But but
but physics allows it.
>> Possible.
>> And particles do this. light things can
I mean not heavy things you know things
that don't have a lot of mass
>> can do things like that so I could go
travel in a rocket ship go towards Alpha
Centauri near the speed of light double
back um and I'll I'll be 2 minutes older
and you'll be 10 years older so really
the idea is that as I get faster and
faster towards the speed of light it's
as though it's as though time stands
still altogether
>> and your your your uh your clocks are
elapsing hardly at all. they're they're
barely ticking. And um and this is one
of the deep ideas in relativity
sometimes called time dilation. Um that
uh time is not absolute and it really it
matters what path you're on in spaceime.
What we call
>> this phrase we use all the time, the age
of the universe.
>> Yeah.
>> There is no such thing because it's all
relative.
>> Oh well um well that's an interesting
question. I would say you can very well
define the age of the universe in the
following way. You can say for an
observer
>> Yeah.
>> who's not moving a lot relative to the
expansion of the universe. Right. So
we're not zipping around a rocket
expansion. Yeah. We're just kind of as
though you drew a dot on spaceime and
stretched the spaceime, but you you're a
bit of ink.
>> You're a coordinate and you haven't
moved. You're just stained on the
spacetime. Then you can very well define
according to the clocks of all of those
observers just like you all over the
universe or the observable universe that
it is 13.8 billion years ago
>> that this primordial event happened that
we call the big bang that you're going
to do that's going we're all going to
agree on that because we're all in a
very similar um
>> yeah but what if you travel so so fast
>> that a billion years passes for me but
two seconds pass for you.
>> Yeah. Yeah. Now I would say right so so
you would say yes I have not
>> you you've moved yourself off that
>> I've moved myself off of that and I
understand though why everyone else is
claiming the universe is a billion years
older so we can agree on that we can say
yes I understand why you all
>> in coordination are arguing that the
universe is 13.8 billion years or if
we've had another billion 14.8 in 8
billion years, you know, in a billion
years. Um,
>> but but for the objects in the universe,
they all have their own set.
>> They all have, right? They can all have
their own their own experience of the
passage of time.
>> Wow.
>> And um and you can you can't think of it
as a terrain. You know, you experience
the train differently. We know that this
is real. We know it's not just your
speed, but it can also be near the earth
or away from the earth. So um near near
heavy objects or away from heavy
objects, they curve the whole spaceime
>> in a way um that's unambiguous. So we
know that our clocks
>> uh run more slowly on the surface of the
earth
>> than they do further and further away.
And we see this effect in our
satellites. Our satellites are doing two
things, right? GPS units have to correct
for the motion of the of the satellites
around the earth and their distance from
the earth to get the relativity and
gravity effect,
>> right? I actually think the motion might
dominate for some satellites, but yeah,
but you have to do both relativistic
effects and then um and so the
satellites have slightly different uh
clocks or their clocks are are um not
synced with ours perfectly.
>> Man, that is wild. So, they have to
they're moving relative to each other.
They're moving relative to the ground.
So that's a lot of calculations,
>> right? And they if you don't correct for
it, then you're not going to find your
Uber.
>> There's no way you're going to find you.
>> Yeah.
>> All right. So here's a question I get. I
I people ask me this all the time
>> and I think I have an answer.
>> Yeah.
But the question is, you know, they say,
look, if you take
>> the uh uh
estimated mass of the entire universe
>> when you do a calculation
>> of the radius that you'd have to push
that all into to turn into a black hole,
>> it turns out to be about roughly the
size of the observable universe.
>> So, is the universe a black hole?
>> Yeah. Um, no. I'd say the universe is
not a black hole. Um, there's different
things. First of all, the universe is
expanding and um and so so so taking a
step back, Einstein really said how
matter and energy is distributed in
spaceime dictates how spacetime curves,
>> right?
>> And uh when we say, "Oh, I'm around a
black hole and everything's going to
fall in." We're kind of ignoring the
fact that there's all this other stuff
in the universe. When I look at the
average of all the stuff in the universe
on the largest scale, um the solution to
that to Einstein's equations, which
would tell you if it was a black hole,
it would tell you if this was a black
hole, and it is not. Um they say no,
>> it yeah, the the the solution to an
average amount of stuff, more or less
the same, you know, um all over the
observable universe is that it's
actually expanding. And
>> in fact, if you look at all the matter
in the universe, the mystery isn't that
it's expanding. It's actually expanding
faster than the mass can account for.
>> Um, and that's where people have heard
this expression about dark energy.
>> And so we we're deducing that there's
something else out there that is
contributing to the energy budget of the
universe.
>> Yeah.
>> And it's driving the spaceime to expand
ever faster. So, it's getting faster and
faster, not slower and slower because
you would kind of expect it to be
getting slower and slower. It comes out
of the big bang
>> because everything's all gravitationally
attracted to each other,
>> right? It's coming out of the big bang.
It's expanding eventually. You know, it
could kind of just get to its maximum,
feel all that mass and come back and
collapse again. Um, but that is not
what's happening.
>> So, I was a graduate student and I did
X-ray physics and, you know, extreme
ultraviolet physics. So, there was this
one bright object in the sky, Signis X1,
this double star.
>> Amazing. But then,
>> you know, they okay, we're looking at
the light, we're interpreting the light,
there must be a black hole there.
>> But then we have
>> Andrea gets and her team Yeah. measuring
the stars moving around the center of
the galaxy, right?
>> We have um the event horizon telescope
imaging, you know, planet size radio
telescope imaging black holes at the
centers of galaxies, super massive ones,
>> right?
>> And then we get LIGO Virgo gravitational
wave observatories,
>> right? M
>> this is nuts.
>> Yeah, this has been the century for
black holes.
>> It's
>> I mean I would say uh
late part of the last century uh people
were kind of losing interest in black
holes. It wasn't clear there was that uh
enthusiasm that there is now. All all of
this has been driven by experimental and
observational discoveries that happened
this century
>> as it should be.
>> Yes.
>> Yeah. Freaking Einstein spoiled us
coming out of with this theory. Yeah.
Right. But an observation and an
experiment.
>> Yeah. I mean it just gave people a lot
more energy and they were galvanized to
understand these very difficult problems
and um and theoretically black holes
remain incredibly important. But um but
they were real astrophysical objects.
Einstein even accepted the math of black
holes before he accepted uh their
reality in in the sky. He he thought
nature would protect us from
>> such
>> well it does sound like a crazy thing to
occur, right? Because it's so different
from our experience.
>> But even more so, how are you going to
crush something
>> that small? Yeah.
>> Right.
>> That big to that small,
>> right? So, how am I going to make the
sun a black hole? I mean, I can't crush
this cup. You know, in principle, this
could be a black hole. It just be atomic
sized, but nobody can overcome
>> the resistance of the matter. So matter
has its own forces, nuclear forces and
>> quantum forces. Yeah. And they do it
does not want to be crushed.
>> No, it does not.
>> And um we all know that it's very hard.
You guys try to crush a beer can, you
know,
>> they can only make the egg experiment.
>> So here's the question. So what's next?
So where where is this going?
>> Yeah.
>> Because I feel like we're at the infancy
of it in a way, right? Because these
experiments are
>> I mean if all of our science funding
doesn't get cut. Yeah. So um we we could
be in the infancy of it. I mean the the
a lot of the experiments took many many
years 20 years or 50 years.
>> I mean LIGO this experiment which
detected two black holes in orbit around
each other which then collided and
merged into one big black hole and it
was like mallets banging on a drum. the
whole of spaceime literally space and
time ringing and the ringing
>> emanated through the universe in the
particular case of our discovery.
>> What was it? Uh a billion and a half
years.
Do I have that number?
>> The first the first one. I feel like
that's right.
>> Was a billion and a half light years
away.
>> Yeah. Wow.
>> Like multisellularity was underway on
the earth.
>> Oh my goodness.
>> Right. Right. And I mean that's
happening all over, but this was the one
>> that we were on this collision course
with it.
>> That is
>> and you know, humans evolve.
>> Einstein comes around and it's at a
neighboring star system. It's still on
its way here ringing. Space time's
ringing. Um
>> Einstein showed up just in enough time
for us to see it
>> for for us to detect this one. And and
by the time they built the the detector
and they uh
>> Well, go into it because I don't think
the people may know what LIGO is. So, so
LIGO is the laser uh uh interferometric
gravitational wave observatory. Um it
it's a very cumbersome name. I don't you
don't even need to know just LIGO to
mirrors and lasers
>> to its friends.
>> Um it's an enormous instrument. It's
shaped like an L and it shines light
down these
>> long vacuum tubes uh four kilometers
long on each side. And what it's really
doing I I liken it to a musical
instrument. What it's really doing is
it's delicately bouncing these mirrors
so that if a wave passes in the space
itself, the mirrors will like bob with
the wave and then the distance traveled
along the two directions is going to be
modulated by this bobbling. And and the
entire experiment is designed to detect
motions like that of less than a
10,000th the width of an atom across
four kilometers. It was the most
stunning engineering achievement. I
mean, even if it hadn't detected
anything, it would have been really sad.
But as an engineering achievement, it
was tremendous. It took 50 years.
>> Wow.
>> Um, and so you imagine that when they
finally installed the advanced
components of this detector, they had
been running for 15 years with an
initial detector that detected nothing.
Crickets, right? But they knew it wasn't
sensitive enough.
>> They keep pushing. 15 years later, it's
now 50 years after it began, a hundred
years since Einstein first proposed
these waves in the shape of space time.
centenery.
>> Some guys are working on a machine, you
know, experimentalists um on two on two
different sites. In the middle of the
night, they decided they weren't ready
for the science run. Um they they
they're they're working to the we hours
in the morning. They they get um besides
themselves, they decide it's time to go
home. They mercifully leave the
instrument locked, but they drive away
with still on.
>> Locked meaning ready for detection, not
offline. And um this wave washes over
the site in Louisiana. It travels at the
speed of light until it washes over the
site in in Washington state. And the
instrument rings and literally they
would listen to the instrument in the uh
control room. Honestly, if if it had
struck a couple hours earlier, they
would have been messing with the
instrument too much to have made this
detection. It's only the first
detection. It's not like it was the only
event in the universe. It was just the
one that fate would have we were on a
collision course with, right? And so um
so it it detects this ring. It's
incredibly uh fast. It happens in
milliseconds and it's incredibly you
would say quiet. It has signal has to be
drastically amplified. But it does
happen in the human auditory range. The
instrument is sensitive to frequencies
of the ringing of spaceime um that are
the same as like the piano.
>> Wow. which is and the piano is such a
great instrument because it's like the
human auditory range. That's why all
theorists learn
>> musical theorists learn on the piano.
>> So what notes are they then? So I does
it go by mass like oh if it's
>> Yeah. Just like you would think that the
bigger the mass of the black hole, the
lower the notes.
>> Oh, I see.
>> So there are some black holes that are
so big um and the collisions are at
frequencies that we can't detect on
Earth. And there is a project called
LISA which is proposed for space which
seems to be moving along.
>> So you have a instead of four kilometers
the distance is much longer.
>> Yeah. You can have a millions of
kilometers. And what you're doing you're
not actually having them physically
connected. You're having nodes
>> which are just floating uh uh
instruments that shine lasers between
them through the empty space
>> uh around in probably a heliocentric
orbit. So it's orbiting the sun.
>> So a big triangle orbiting the sun. big
triangle orbiting the sun.
>> Yeah. I mean, each three of the
instruments are separately orbiting,
>> right? Yeah. Yeah.
>> So, but um but the point is I kind of
liken it to an electric guitar. If you
think of how an electric guitar works,
you pluck a string, right?
>> The string rings at a certain frequency,
but you don't really hear it
>> very well.
>> What do you mean?
>> You have to put the the amplifier, it's
electric, right? And the amplifier
records the ringing and plays it back to
you, right? And that is actually kind of
how the instrument works. It's like it's
like a musical instrument. It's
detecting the ringing of space,
>> right?
>> And then it's going through this
incredibly elaborate process of
amplifying it for you and playing it
back to you.
>> So now
>> you can listen to it.
>> Oh, really? So you go to
>> Yeah, that's what it sounds like. It's
like a It's called a chirp.
>> So So tell me this. Can you tell what it
is by the sound of the chirp?
>> It's a great question. Mathematically
there are these really interesting
papers that are say can you hear the
shape of a drum? So from the frequencies
of the ringing space um can you deduce
like the shape of the drum? In this case
the analogy would really be the motion
of the mallets.
>> I see
>> the the magnitude the the heft
>> of the mallets their mass and their
motions. And the answer is yeah. I mean
there are some that you can't tell one
from the other but you can absolutely.
So have they simulated it so so you can
go and listen to like here's what this
would sound like here's what that would
sound like.
>> Right. So the first one they detected
they could very quickly and they've been
working on this also for decades this
analysis. Yeah.
>> Right. You give me the sound and I'll
give you the black holes. Right. That's
a that's a hard hard problem. Many many
groups worked on that for a very long
time. So different groups who try to get
overlapping results. That's one way that
they know that they haven't just totally
biased and they have a real detection.
And so what they came back with with was
we just heard the collision of two black
holes. They were each around 30 times
the mass of the sun. One was a little
bigger, one was a little smaller.
>> So they're big. That's pretty big. 30
times the mass of the sun.
>> And um and they caught them in their
final handful of orbits
>> in a long long life together. They might
have been together for billions of years
solely spiraling together, banging
spaceime, losing energy, coming closer,
getting faster. By the time they're that
close together, they could be traveling
at 3/4 the speed of light and it's
happening really fast.
>> Okay. So, you just said something. So,
when I was in graduate school, one of
the guys who won a Nobel Prize in my
department
>> Uhhuh.
>> was for um this in spiral of
>> uh black holes due to
>> or I think it might have been even um
binary stars because they're
>> they lose energy by emitting
gravitational waves,
>> right? So those gravitational waves that
are just emitted from the two things
orbiting each other.
>> Yes.
>> We can't detect that.
>> No. And it's a really good question. We
can detect that they're spiraling
together,
>> right?
>> And we can use that to to deduce uh that
we have calculated how much energy is
being lost right
>> to these waves. And that was beautifully
done. Nobel prizes were involved. Taylor
and Hol.
>> Yes.
>> Right. And one of them was a pulsar.
Right. Uh what was it called?
>> Taylor pulsar, right? Um and um
>> oh that's how they did the timing
because it was uh so a pulsar is a
neutron star
>> that has a beam that
>> right
>> points at you intermittently. So you see
beeps right and um it was an incredibly
accurate determination, but they didn't
directly detect the gravitational waves
themselves. And you're saying, "Yeah, we
can't detect those and we cannot.
They're way too weak." This is part of
gravity being weak. the earth's pulling
on us, but it's actually it's I can beat
the whole earth. I can jump, you know.
So, so
how would the frequency compare then?
Would it be
>> too uh low
>> and um and the amplitude just just
undetectable?
>> So, so the the the the volume
>> and the pitch, right,
>> are outside of the range of our
instruments.
>> Yeah. Yeah. It's like exactly the volume
is your volume knob is way too low. Um,
and even this was, you know, this
sensitivity that we're describing is is
required because it's still it's by the
time it gets here,
>> it's just, you know, it's so faint. If
you were floating near those two black
holes when they were colliding,
>> it is conceivable that even in the
vacuum of empty space that your ear
mechanism could ring in response.
>> Wow.
>> And you would hear it
>> if you were close enough.
>> Literally, it would move your hear it.
Yeah. And your skull being less given to
squeezing and stretching hopefully would
resist, but you hear it, right? Your
brain would do that.
>> So here's here's here's something that
comes to mind then.
>> If these gravitational waves are
emanating from these black holes
colliding,
>> are they escaping from inside the black
hole?
>> Yeah, it's a great question. They are
not escaping from inside the black hole.
It is ringing space outside the black
holes. However, the sum the final black
hole,
>> yes,
>> has a mass that's less than the sum of
the two black holes. The E= MC² energy,
the mass that's lost is all pumped into
these gravitational waves. Wow.
>> So, the 30 something solar mass black
hole and the 20some solar mass black
hole when they merge, yeah,
>> that black hole is a little lighter
>> than the sum of those two masses. And
are we talking
>> all of that energy E= MC² energy as we
know from nuclear bombs right is huge.
So all of that energy it was something
like three solar masses of energy is
enormous. And that means that that event
was the most powerful event
>> um human beings have recorded since the
big bang.
>> Wow. Um I mean now there have been
others but the power in it
>> was more than the power in all the light
from all the stars in the observable
universe combined.
>> So how many of these things have they
discovered now?
>> Well now if the instrument were
operating all the time kind of monthly
>> be like one a month we say
>> kind of monthly and and and um and the
fact that they're so powerful people
didn't expect the black holes to be that
big. So people worried look the black
holes are going to be a few times the
mass of the sun only 10 times like
that's a good kind of canonical
>> 10 and so it's going to be hard to get
anything loud enough to ring our
instruments. They're going to have to be
in real close and we're going to have to
get real lucky. But that's not what
happened.
>> So we got black holes are big. Yeah.
>> Yeah. Do we have hundreds or thousands
of times in in terms of these
collisions?
>> I would say well so in principle they're
happening all the time. They're just too
far away. So we're kind of saying out to
the distance we can we can detect I
don't want to say see because none of it
comes out as light
>> right all of this comes out in the ring
in the black holes it's complete
darkness
>> so it's one of the rare experiments in
astronomy where we're not talking about
a telescope collecting light it's
completely different
>> so here's a question if it's emitting
all that energy like three solar masses
of energy
>> it may not be doing it in all directions
equally so could it just like
>> create a jet of gravitational energy and
fly off.
>> You do have to think about the
orientation of the orbital plane,
>> you know, so they're orbiting around
each other and there's a plane it what
the orientation of that plane relative
to your line of sight or your line of
detection in this case. And it does
matter. It will change the signal. And
so we also um there's some ambiguity in
trying to deter determine things like
that. Well, I guess the question I was
getting at though is does the new black
hole that formed
>> by the emitting all this gravitational
wave energy, could that gravitational
wave energy propel it to turn into a
black hole that just shoots?
>> It can happen.
>> So, right. So, it shoots so much energy
in one direction the black hole starts
to jettison. Black holes can be cruising
along.
>> Yeah.
>> Holy cow. So, out of nowhere.
>> Yeah. I mean, it you know, it maybe came
in it would it all depends on the orbits
just like the mallets on the drum. If
you swirl them around, it makes a
certain sound. It's very,
>> you know, eccentric, right? If it's
looping, coming close and going back out
again, it will be very different. It'll
be like a knocking. It'll get quiet.
It'll bang. It'll get quiet and then
you'll hear it kind of banging bang bang
bang bang.
>> Um, so, so yes, we can kind of determine
its orbital motion as well as the masses
of the original black holes. And yeah,
maybe sometimes there are these funny
things that can happen where a lot of
energy goes off in one direction and the
black hole just starts to kind of wander
around the galaxy,
but once it happens, it goes quiet uh
once it
>> so you get no more data.
>> So there's actually something really
deep about this question of this ringing
down. So when the the event horizons
merge like this bubble of ink and
bobbles down and then goes quiet, that's
because uh something very profound about
black holes and that is that they they
cannot tolerate any imperfections
>> and and that's actually a deep point. So
we've been talking about tolerate
>> they cannot tolerate any imperfection.
If you took Mount Everest and you tried
to put it
>> I've dated a black hole once in my
youth. It was.
>> Yeah.
>> Haven't we all known?
>> Um or I was ever I don't know. But if
so, you put Mount Everest on the event
horizon. Uh it won't tolerate that bump
for long. Okay. It has to shake it off.
And one way to see it is kind of
philosophically to go back to my roots
which I disparaged.
Um, and that is the event horizon says
you can know nothing about the interior
of a black hole.
>> Right? You cannot know anything about
it. If that bump remained, you would
know more about it than you should be
allowed to.
>> Oh, is this very principle?
>> Black holes have no hair.
>> Black holes have no hair. The idea it
can't have stuff emanating out of it
which would tell you if you could trace
the hair, it would tell you about
properties on the inside. The event
horizon really forbids the transmission
of information from the interior of the
black hole to the exterior. We kind of
establish kind of by definition right by
definition. So that means that I can't
come up to a black hole a billion years
after its formation and deduce ah that
was a blue star because that would mean
somehow information was coming out of
the interior and and no information
could come out of that interior. But why
is that a deep thing? Why? Oh, well,
okay. Oh, there's there's there's
several reasons why it's a deep thing,
but in in this context, I would say
>> it's a deep thing because it means that
there's something featureless about
black holes. There are some things I can
know about it.
>> I can know its electric charge,
>> right?
>> I can know its mass and I can know its
spin.
>> Yes,
>> that's it.
>> That's it.
>> That's my whole list, right?
>> Yeah. So the reason why that's so
profound is it means it's not like
anything else in the universe which can
>> which can have flaws
>> and features right so even a neutron
star can have tiny tiny they're very
tiny tiny tiny little features I could
say oh that's my neutron star
>> right
>> I put a flag on it I went to the moon I
put a flag on it the moon has this big
crater it has these it's a specific moon
>> and it's made up of this stuff
>> it means that black holes are so
featureless that they're closer to
fundamental particles
>> than they are to astrophysical objects
in
>> two black holes.
>> Mhm.
>> That had the same mass, charge, and
spin.
>> You cannot tell the difference.
>> And I did the cup game.
>> There's no meaning to saying which one's
which. It's worse than saying, "Ah,
that's, you know, I tracked it in my
mind." There's no meaning
>> to saying this black hole is mine or
this was the one I marked or uh they are
indistinguishable in the same way that
an electron is indistinguishable
from every other electron in the
universe. One electron is not a little
bit heavier. You can't say, "Oh, that's,
you know, that was my electron that I
sloughed off to, you know, this
morning." Um they're so identical that
they're technically interchangeable in a
very profound way. Wow. because we think
that they're a fundamental particle of
nature. So there's something fundamental
about the electron. It's indivisible,
>> right?
>> And um and it cannot be a little faster
spin, a little heavier.
>> So there was this theory I heard that
because electrons are indistinguishable,
that means there's really only one
electron in the universe. Have you heard
this?
>> I have sort of, but
>> yeah, I made it. So that Yeah. So
>> they're too busy for me.
If you choose three, you know, you
choose a set of three numbers to to, you
know, that really is one black hole.
>> Yeah. So, well, so but it does suggest
that black holes could be fundamental to
nature. Now, this is why it's uh this is
why it's so profound. Whereas a neutron
star is not fundamental to nature. It's
made through a specific process. It's
strictly astrophysical. It happens
because of nuclear physics and these
kinds of details. And neutron stars are
all a little different from every other
neutron star. They're slightly slightly
different. They're more similar
>> because they're they're getting on their
way to black holes. It's harder
>> to put a mountain
>> on a neutron star, right, than it is on
the Earth. So, they're very similar.
>> But, um but the black hole being
indistinguishable suggests it might be
fundamental to the laws of nature.
>> And that the fact that these huge
objects, stars, made these big
macroscopic black holes is crazy. But we
should expect them in the big bang as
well as little tiny microscopic black
holes because we should expect that they
are fundamental to the laws of nature.
>> Okay. So let me tell you where you where
you inspired my mind to go there.
>> Right. Yeah.
>> Elementary particles
>> are considered point particles.
>> Yet they have masses. Mhm.
>> So you can conclude
>> if you take that model seriously that
they have infinite density
>> and that's sort of like we say about the
singularity of a black hole. So is it
the case that
>> if you tend to infinite density you tend
to being fundamental to the universe?
>> It's an interesting question. I think
you would say I think you're absolutely
right. We we think of electrons as point
particles,
>> right? But you can't really exactly
specify the location of the electron
because of quantum mechanics,
>> right?
>> And that kind of leads to a sort of
fuzziness. It's not just the Heisenberg
uncertainty principle, but even the
whole things.
>> What about the black hole? If it's going
down to what appears to be
>> the center, but the horizon, right,
>> is pretty classical. It's not even
doesn't have to be quantum. It's so big.
>> So the the when we talk about this
fundamental black hole where the only
thing we can say are these three
numbers.
>> Yeah. Does that apply to the entire
system including the event horizon or is
that the whatever lies at the heart of
the black hole?
>> Yeah, I would say if you take that
really seriously, you don't what does it
mean to say what's at the heart of the
black hole
>> for us?
>> It's behind the horizon, right?
>> So in some sense even if yeah something
really happened there. I threw an
astronaut in. They had an experience.
They were torn to shreds. And right
before
>> they were, they understood. You know
what was really at the center. It was
not a singularity. It was some quantum
madness. Right? To some extent, that
doesn't matter.
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All right, so I'm going to give you some
headlines. We're going to do a lightning
round.
>> Two are true,
>> okay,
>> and one is fake.
>> Okay,
>> and so if you can pick out the fake one.
Let's go.
Physicists say many black holes seated
in atmosphere could suck heat and fight
global warming.
>> Is it true that physicists said that?
>> Yeah. So some physicists they did their
models and they were like listen you
know if we take these tiny black holes
>> we could use this to fight global
climate change. Another one.
>> Okay. There could be strange black hole
moons that can indicate the existence of
an advanced alien civilization.
>> Okay.
>> And the third one,
physicists propose a cheaper alternative
to building a big accelerator.
>> Uhhuh.
>> We could just use super massive black
holes.
>> Okay. I would say um none of those
things are true.
These are real headlines and may not be
true but which made the pages of
>> oh that is that involves some social
theory that I can't conquer. I can
imagine the mini black hole was an
actual headline but I'm just imagining
um uh what was the other one?
>> So we have the atmosphere using a black
hole
>> right
>> a black hole moon being in sign of an
advanced alien civilization. If we could
try to Yeah.
>> And using the super massive black holes
as particle colliders,
>> but you got to put it in Switzerland.
That's the only
>> Yeah. I mean,
>> huh. Well, I could say that uh super
massive black holes are probably
particle accelerators.
>> All right. So, you eliminated that one
and you were right.
>> Yeah, because they they So, black holes
in general can I mean, but this is
actually real. Like, we see this
>> um we see enormous jets coming out of
>> super massive black holes. These jets
are electromagnetic. They're literally
like ray guns um where where particles
are shooting incredibly powerfully high
energy particles. It could be X-ray
literally like an X-ray gun um along
these magnetic field lines and and we
know that black holes can do that. So
the irony of the darkest phenomena in
the universe becoming the powerful
engines of the brightest phenomena. Now
the particles aren't coming from inside
the black hole.
>> Okay. But here's originating from
outside.
>> So this massive beam
>> Yeah. coming out of a center of a super
massive black hole.
>> We're talking light years.
>> Yeah. Um Oh, yeah. The the jets can be
bigger than the galaxy in which they
live. Yeah. You can see the jets.
>> Yeah. Hundreds of thousands of light
years. Burst like you can see them
breaking out of the galaxy in cases.
>> Why did the Empire just use that Death
Star, right? That hole,
>> right? Which leads us to the second
headline. Yeah, I mean uh uh so it's not
true in the sense that there has not
been an advanced civilization that we
are aware of that has made black hole
moons. Let's just be clear that has not
happened. That has not happened to our
deserve that. But could we, you know,
just like we people look for Dyson
sphere signals,
>> right? I suppose, you know, gosh, if you
figured out a way to collapse uh um I
mean a black hole moon is still pretty
big. I mean the sun if it was a black
hole it would be much smaller than our
moon.
>> Right.
>> Right. Much smaller than our moon.
>> But then what would if you put it at the
moon's distance earth would orbit it
>> like now.
>> Right. Exactly. So I don't know about
that one. Um the mini black holes. Yeah.
I don't know. I I mean I can imagine a
calculation. Let's see. How would this
work? A little mini black hole would
suck heat out because it would absorb
stuff. Problem with mini black holes is
they emit a lot too. There you go.
>> Through Hawking radiation.
>> There you go. So that was a false one.
>> So that was a false one. So they would
be hotter. Yeah.
>> Then they would So they would heat up
the atmosphere.
>> Well, you know what? This is a um
terrible speed round because it's based
on headlines, right? And people would
just write things to get crazy things.
>> Yeah. Yeah.
>> But but that's so the interesting thing
about little so big all black holes we
think Hawking radiate. they they emit
>> some quantum energy through this very
subtle process that made Stephen Hawking
so famous for its discovery. Um the
bigger the black hole, the colder they
are,
>> right?
>> So the smaller the black hole, the
hotter they are. So if I had a little
mini black hole and I put it in the
atmosphere, I'd be very likely to heat
up the atmosphere.
>> That does not work with boxes.
>> And it would Right. Yeah. And they also
explode. They explode.
>> The the tiny ones get smaller and
smaller.
>> Yeah. They explode eventually. Yeah. So
they're they're not going to do much
good for cooling off.
>> All right. All right. So, one thing
about relativity, I mean, excuse me,
about black holes to me is how they lie
at the intersection, right? They're
classical physics and size, but they're
astronomical cosmological objects and
>> they're in a realm of uh quantum
mechanics in the sense of the horizon
properties and the singularity and
they're relativistic.
>> Right.
>> Right. So if you look at this deep
connection between the quantum and
relativity and cosmology and black holes
like what is that where does that lead
you?
>> Mhm. So I mean this we were just talking
about Hawking um it is it is the same
sense the black holes seem to be saying
something fundamental about the
universe. They also seem to be this one
terrain that we have just mathematically
pen and paper on which we can explore
gravity at its strongest colliding with
quantum mechanics.
>> And you might have thought as you just
set it up look black holes, you know,
it's still a big object. Usually we
think of them as macroscopic objects.
>> Yeah, exactly.
>> And um so why am I worrying about
quantum mechanics at six kilometers and
not even a lot of curvature? Like I
said, you could sail across the horizon
and nothing bad happens to you. You're
not
>> you're not in some crazy quantum realm.
Um well, it turns out and that's why
Hawkings discovery was so ingenious. It
took just a little smidge of quantum
mechanics to show that there was a very
big problem. Okay. What I mean by a
little smidge of quantum mechanics is
this idea that even empty space
>> has a little bit of quantum mechanics
going on,
>> right? Yeah. Yeah.
>> We've talked about Heisenberg's
uncertainty principle,
>> which says you can never precisely say
exactly where a particle is located
without losing a tremendous amount of
knowledge, let's say, in its motion,
>> right?
>> In its momentum.
>> Um,
>> well, that also kind of means you can
never exactly say a particle's not
there. kind of led to these ideas. What
does it mean to say I 100% certainty say
there's no particle there? Doesn't seem
to be quite right according to
Heisenberg. And people started thinking
about oh well,
>> you know, you can have these sort of
pairs of particles that come out of
nothing.
>> Yeah.
>> As long as they match enough to go back
to nothing.
>> If one's spinning up, the other better
be spinning down. If one's positively
charged, the other better be negatively
charged. They have to equal the zero,
you know, the nothingness. Yes. uh of of
of empty space. They can't come out. You
can't come out in like two positive
particles. That can't happen, right?
They have to cancel each other in all
the ways you can kind of imagine. Um
>> as long as it happens really fast and
they go away again,
>> right?
>> And um and so in this room, I have no
way of kind of capturing that energy.
It's happens really fast. It's
>> But black hole can do something super
sneaky. If this is happening, it's
nothing special about the black hole.
This is just quantum mechanics of empty
space.
nothing to do with the black hole being
strong gravity or weak gravity or
nothing. It's just that if this happens
and one of the little particles in the
pair
>> ends up on the wrong side of the event
horizon, the other one can't go back to
the vacuum because now it's it's
tainted. It has colors
>> that can't go into the nothingness. You
know, it has properties. It has charges.
It's gone, right? It it can't disappear
into the vacuum. It lost its pair.
Now that particle which originated
outside the black hole is stuck and it
lives. It exists
>> stuck in existence.
>> It's stuck in existence.
>> So the the event horizon did something
very very tricky by not permitting
>> you know that the pair can never its
pair can never make it back out again.
>> Right? And so so the one that was
stranded can just sail off to the
distance and it looks like a particle is
emitted. It looks like the black hole is
is radiating particles.
>> Right
>> now this is a very very very tiny effect
for all astrophysical black holes.
>> They are
>> let me just just clarify that point. So
it looks like it's radiating particles.
>> Yeah.
>> But the particle actually originates
from outside the black hole.
>> Yeah. And it could be a photon. It could
be an actual photon or it could be a
particle, right?
>> Um but that lost it, they can all lose
their pairs.
>> And um and it looks like the edge of the
black hole just out just outside the
event horizon is radiating.
>> Yeah.
>> And it looks it has a temperature
>> and um and the tricky thing is that the
particle it absorbed
>> what you think of as like you like oh it
has a negative momentum. It's momentum
is directed with the whole space-time
rotation in the same way that space and
time interchange places. Momentum and
energy interchange places and the black
hole feels like it absorbed a negative
energy.
>> Black hole got a little lighter.
>> Wow.
>> In the process, black hole gets a little
smaller.
>> It seems to be radiating at this hawking
temperature and it gets a little smaller
and eventually gets smaller and smaller
and the process gets hotter, faster,
more catastrophic. And the idea is
eventually the black hole just explodes
like we talked about the mini black
holes just explodes.
>> So basically what you're saying is is
that quantum mechanics is costic to
black holes. It's corrosive to black
holes.
>> They will evaporate away. Wow.
>> Via this very subtle quantum process.
And it's not extreme quantum mechanic.
It's not quantum gravity. I don't need
quantum gravity. Just a tiny little bit.
So, one of the things, one of the black
hole people I saw speaking in an
interview
>> was uh Marco
>> Relli,
>> and he mentioned Carlo Reveli. That's
right. Carlo. Marco.
>> Yeah. Italian.
>> They're twins.
>> Um he mentioned that they're bigger on
the inside than they are on the outside.
>> Oh, yeah.
>> So, I've never actually saw the geometry
>> inside of a black hole. So, how does
that come about?
>> Yeah. So, so black holes being bigger on
the inside than the outside. Uh, the way
I think about it, let's say you draw a
circle.
>> Okay, we all are used to drawing a
straight line to the center of that
circle. So, that's flat.
>> Wow.
>> And I know exactly how much area
>> is contained in that flat
>> geometry. But if it's curved, if I pull,
if it's a little net webbing and I pull
it like a horn,
>> like a trumpet, now there's a lot more
area,
>> right? until you get to the center
because of the curvature.
>> So curved things can hide. That's a
little misleading cuz I had to bend it
into a third dimension but yes
>> into another dimens. So that reminds me
of um the way they used to determine the
areas of
>> uklitian figures right
>> with uh triangles inside of it. Right.
>> So you can get the area of a circle.
>> Yeah. Everything we believe about areas
and volumes inscribed
boundaries. Yeah. Yeah.
>> Rectang a triangle inside of a black
hole. The three angles don't sum to 180.
>> They do not.
>> No.
>> And um so it's non uklidian geometry.
It's not flat geometry. And that's
exactly it that the space time is
curved. Now I can't really do that with
the black hole because I'd have to
visualize it in
>> curving in a different dimension. It's
just very hard to do. You don't have to
do the curving.
>> You all see these these pictures of
these funnels that are meant to indicate
black holes.
>> And what that really is is an embedding
diagram. It's not that the black hole
like this is an actual direction in
space, right, which it bends into.
That's not it. But it just helps you
visualize. They're called embedding
diagrams because they help you visualize
the curvature as best that we can in our
limitations of our visualization, our 3D
>> our 3D minds.
>> Yes. Yes.
>> But but we do know everything we believe
about the volume inside a sphere is
based on uklitian geometry and it's not
uklidian in there.
>> And so they can be very big on the
inside. You know, you can have all kinds
of strange things. you can add to the
interior of black holes just to noodle
around. Yeah,
>> we don't think nature
>> does that when it collapses stars. But
if I'm just playing games with general
relativity, I mean, I can put all kinds
of crazy things on the interior of a
black hole.
>> Wow. So, another thing about black holes
that I heard
>> that is one of those things you hear a
lot as a person who consumes media and
books about this stuff
>> is the idea that all of the information
on the interior of the black hole
>> can be encoded on the surface. It's like
a hologram. You can get 3D information
from a 2D surface and then that somehow
extends to the universe.
>> So, what's going on here? So,
>> yeah, exactly. Tell me what's going on.
Well, let's go back a little bit because
when these things explode, here's the
problem. So, they explode. So, maybe
that's just what happens. And
fascinating. Wow. Interesting. Black
holes evaporate away and they explode.
Big deal. It's a big deal because it
said there was now a fundamental paradox
>> between Einstein's predictions about
black holes or they weren't Einstein's
but in the context of Einstein's theory,
>> right?
>> Versus the predictions of quantum
mechanics. Because I've told you you can
know nothing about the interior of a
black hole. you can know nothing about
it.
>> So that means that all of that radiation
that escaped from the black hole has no
information about what went in.
>> Now
what's so bad about that? Um you could
say, you know, when we talked about the
event horizon before, well so what? We
can't know what's on the inside. I'm
okay with that as long as it's still
there,
>> right?
>> Why does that matter to me? Because
quantum mechanics says you cannot
destroy information. So if I accept
even if you haven't studied quantum
mechanics, if you just take people's
word for it that the entire theory is
structured in such a way that you cannot
lose information. Right? Okay.
>> Yeah.
>> Now general relativity says the event
horizon is structured in such a way that
you cannot have that information that
you want. You cannot it is behind the
event horizon. Right? And all this
radiation that came out of the black
hole over billions of years could not
have had
>> a single bit of information about all
the quantum
>> particles that originally entered. Right
>> now, I don't mind that as long as
they're always locked inside. But once
you yank the curtain up, when this thing
explodes
>> and the event horizon is yanked up,
>> where did all that quantum information
go? Now I have a real problem. quantum
mechanics is wrong or something's wrong
about the predictions of general
relativity. Somehow the information does
get past the event horizon.
>> Has this has this been resolved
>> ongoing since the 70s? Okay. At one
point Hawking made a bet that
information was lost. It went back and
forth. Um uh the quantum people held
strong said quantum mechanics won't
give. And um and where we are now after
those 50 plus years is um the belief
that in fact the information will make
it out in very very subtle ways but it's
very subtle.
>> Interesting.
>> Very subtle. Now you talked about
holography and it all comes back to this
idea.
>> Yeah.
>> Um but it comes back to to where the
information maybe actually gets stored.
There's lots of different attempts
people have made.
>> Um and or entanglement between the
interior of a black hole and the
exterior of a black hole.
>> Oh wow.
>> And maybe um maybe the Hawking radiation
is quantum entangled. This is how crazy
it's gotten
>> with wormholes.
>> Oh, the ER equals DPR.
>> Yeah. So the idea that um you can
entangle across the event horizon with a
wormhole allows you to cheat the event
horizon a little so that now the the
radiation that escapes was entangled
with something on the interior of the
black hole
>> and thereby can have information.
>> So we use the phrase quantum
entanglement.
>> Would you mind explaining unpacking that
a little bit?
>> Yeah, quantum entanglement is pretty
tricky. So, so we can think of I often
give the wishbone example of
entanglement. Okay. So,
>> I don't know that one.
>> Do you know the you have Yeah, you know
what a wishbone is, right? You take
Right. As a kid, you you each hold at
some part of the poor turkey
>> and you break it um at Thanksgiving and
one of you gets the big piece and one of
you gets the small piece. It's never
even,
>> right?
>> And um so that's a non-quantum
entanglement. Suppose we didn't look at
the result.
>> We break it. We don't look and you put
yours in your pocket. I put mine in my
pocket. Right.
>> I look at mine. I have the big piece. I
know you have the small piece. Also not
quantum,
>> right?
>> Okay.
>> Um the quantum experiment
>> lets you know.
>> I immediately know yours.
>> Right.
>> The quantum ones drastically
more mysterious.
>> In the quantum superposition, we we we
break entanglement. We break the
wishbone. We put in our pockets. But it
hasn't assumed a definite state yet.
It's
>> I have the big one, you have the small
one plus I have the small piece and you
have the big bone. And so
>> we both have a combination of big piece
small piece until one of us looks
>> right. And so but it's literally in a
superp position of those two states. It
has not fully
>> sometimes we say collapsed
>> right
>> to be one or the other of those
solutions. It is actually
>> both.
And um if I very precariously travel to
Andromeda,
another galaxy far away. Quantum
mechanics is so delicate. It's hard to
maintain that superp position. So maybe
it just gets hot in the my pocket or I
just um I actually bombard it with
particles to see what's going on. Maybe
I shine light on it so I can literally
see it, right? I will disturb the superp
position and it will either be the big
piece and I've won or the small piece
and I've lost,
>> right? But instantaneously
your piece has assumed the proper pair.
So it's no longer it is no longer in a
super position. Yours was in was in this
>> state of boness. Mine was in the state
of bothness that we call superp
position. Right.
>> Where two million light years apart,
right?
>> You decide to look at yours.
>> Yeah.
>> And so it goes out of bothness state and
becomes a single state.
>> Yeah.
>> And mine two million light years away.
>> Yeah.
does the same thing and becomes the the
the correct wow.
>> Right? So Einstein talked about this uh
as an argument for why quantum mechanics
must be wrong.
>> He was trying to say it's wrong. It's
absurd.
>> That cannot be. First of all, it seems
as though information traveled faster
than speed of light.
>> Right?
>> And um second of all, it's just action
at a distance which he'd been trying to
cure since he first thought about curved
spaceime. didn't want the earth pulling
on the apple from some great distance.
It didn't make sense to him.
>> It was spooky action at distance and now
it was back.
>> Yeah.
>> And he had fixed this already, you know.
>> Um but it seems to be just the way it
is. Now I have to be you have to be
careful about information traveling
faster than the speed of light. When you
look at your piece, you don't know that
I've performed my experiment faster than
the speed of light. You don't know that
you're not the one who broke collapse
the wave function. for you and I to to
determine which one of us was the one
that collapsed and caused this to
happen, we'd have to get on a phone,
send a light signal, we would have to
communicate
>> slower or at the speed of light, right?
>> And so no classical information is ever
communicated faster than the speed of
light. But quantum information seems to
be able to do this.
>> Wow. So,
>> so the entanglement is this kind of oh
the outside particle and the Hawking
radiation comes out and it's the big
piece. It tells you that the small piece
is on the inside. You just learned
something about something on the inside
of the black hole.
>> Ah okay.
>> So that's how entanglement allows you to
get information about what's inside the
black hole.
>> Yeah.
>> It's very it's
>> so something on the outside can be
entangled with something on the inside
and therefore right
>> by making a measurement of the outside
>> you know everything about what's on the
inside. All these years.
>> All these years. Now, how now? There was
a whole there's a whole complicated
story about entanglements because I
thought my particle had to be entangled
with the Hawking its pair.
>> Yeah.
>> Because, you know, same reason, you
know, they had to be perfectly matched
to go back to the vacuum.
>> So, it can't be tangled with the pair
>> and be entangled with what made the
black hole
>> and the quantum particles that had
fallen in long ago. So, it wasn't that
quick a solution. They've really
struggled. And that's why wormholes
start to come in. They're like, "Well,
maybe particle on the outside is the
particle on the inside because they're
connected by a wormhole." It gets pretty
wacky. So, I'm I'm not going to tell you
that there's a pen and paper solution
where I can calculate it for you and
say, "See,
>> I'm tracking this quantum bit,
>> right?
>> And I can show you how it came out,
right? and how somebody on the outside
captured it and reconstructed
the piece of wood that fell inside
>> incendiary and I rebuilt it.
>> So you can get information but not full
histories.
>> Nobody knows how to do it yet.
>> But why do they think it's plausible?
They think it's plausible because of um
these really subtle arguments around
holography.
>> I was just talking to my kid about this
cuz we were sitting around I build like
to build a fire at night sometimes,
right?
>> Yeah. And I was like, "Yeah, you know,
>> he was asking me about where does the
wood go, right?" And I was like, "Yeah,
so you know, if you
>> add up all the ash and capture it and
weigh it, capture all the smoke and
weigh it, and capture all the gases,
>> right?
>> It'll weigh the same as the original
would,
>> right?
>> But now the question becomes,
>> if you were to give someone, here's a
bag of ash, here's a bag of smoke,
here's a bag of gases,
>> what did I burn?"
>> Right? You can imagine they could
reconstruct that. Oh, you burned an
>> off. It's even stronger than that. If
you had carved your initials on the wood
in principle, I should be able to
reconstruct even that detail.
>> Oh jeez.
>> Everything I I must be able to
reconstruct. Now, of course, nobody
could do it in practice. So why do we
think that? We think that because we
think that this information isn't lost.
That's exactly it.
>> So
you really took things to a different
level on me, right? Because now you know
that's like a cosmetic feature as I
think of it. It's not
>> right. But it's still information and
how the atoms were arranged relative to
each other.
>> Wait, even their arrangement. So I can
say whether it was a cube or a sphere of
wood,
>> right? In principle
>> or a cylinder
>> and if it was an encyclopedia,
>> what if it was spinning as it was
burning?
>> You should be able to reconstruct the
written if if Shakespeare if Romeo and
Juliet was written on the page, you
should be able to reconstruct it. and
you burnt a piece of paper.
>> Um, but this is so this is how seriously
people take the idea of information.
Now,
>> you can't do it. So, the idea would be,
okay, if I'm sitting outside the black
hole and I have these stations and I'm
collecting
>> all the Hawking radiation, I should be
able to do what you just said I could do
for the burning wood and reconstruct
um all the information in it. But the
event horizon says it has no information
in it. So, I don't need to be able to do
it in practice. Right.
>> I just need to believe that the
information didn't disappear from the
universe.
>> Right. And then quantum mechanics are
satisfied.
>> The quantum mechanics is safe.
>> It's safe. Yeah. Yeah. So you mentioned
that black holes are
>> like fundamental particles like
electrons, right? They have this
description that's nicely neatly
packaged and they're indistinguishable.
>> Why is that a big deal?
>> I think it's a big deal because we often
talk about how black holes are dead
stars
>> and that's true. Some stars, if they're
very, very heavy at the end of their
life cycle when they run out of nuclear
fuel, will not be able to resist this
catastrophic collapse, right?
>> And they'll just keep falling. You know,
we talked about it's hard to crush
things. That's one of the only ways
anyone's ever thought of to make a black
hole. It's an entire star collapsing
without the nuclear fuel resisting the
the collapse.
>> So, we often think, okay, black holes
are these dead stars, collapsed stars.
But what we're realizing is that's just
one way nature figured out how to make
them,
>> right?
>> And it's just a way nature figured out
how to make very big macroscopic black
holes. Yeah.
>> Because if they're fundamental
particles, they should be made little
tiny black holes.
>> Yeah.
>> Like in the big bang, same time
electrons are made,
>> right? Matter is made in the early
universe,
>> right?
>> Um hydrogen in our body comes from the
early universe. I would I would argue
that you know when we talk about
>> these elementary particles what we say
is that they are uh quantizations of a
quantum field.
>> Right.
>> Right. And so we we think of there's an
electron field and there's these quark
fields. So would there be a black hole
field?
>> Well that's a really interesting
question. I I think you would say
there's a gravitational field and there
is a quanta of the gravitational field.
The graviton
>> right
>> the force carrier right of the
gravitational field. That's really
interesting. But uh are they quanta of
>> uh indivisible the the the smallest unit
of mass
>> in some sense. Right. So um a very
primordial black hole made made in the
big bang. It would actually be heavy for
um its tiny size. That's the whole thing
about black holes.
>> But aren't those the ones that radiate?
The the ones that
>> Oh, it's it's a really Right. It's a
really good question. So there's
different gradations you could make
>> because black holes unlike electrons can
come in different masses.
>> It can come in all masses.
>> So in the early universe the thinking is
really well you make primordial black
holes that um they are very small and
yes they explode. That's exactly what
people think happened to them. And so we
look for signals of these firecrackers
from the early universe that could be
exploding black holes. M
>> um and so people do take seriously that
black holes were formed in other ways
than just collapsed stars. So if they
are formed in a big bang, these
microscopic black holes
>> and we can get information out of them
then could they be a way of
>> well they can tell us yes they can tell
us about the big bang as can all the
particles right from the early universe
>> nucleiosynthesis
>> but the black hole is playing a special
role in terms of understanding the
fundamental laws of the universe because
it really is unique
>> in a terrain where gravity in quantum
mechanics are really fighting for
control, fighting for dominance, right?
So it is really the key and by terrain I
really mean calculations.
>> Nobody can do this in astrophysics yet,
right? Nobody can measure this in real
objects out there physically. So this is
just pen and paper, but it provides it's
tell it's giving us all the clues. It's
it's showing us the way.
>> Wow.
>> Right. because it's so restrictive,
>> so constrained, and yet it's telling us
all of this incredible um directions to
to look in to understand uh how quantum
mechanics and gravity came together. And
if we do understand it on the black
hole, we'll understand the big bang.
>> So, you're truly researching at the
frontier. You're at the edge of
understanding.
>> Well, I um right now I'm not really
right now I'm looking more at extra
spatial dimensions these days. Yes, I've
done many years of just black holes for
various properties but um
>> as engines as electromagnetic batteries
uh we have as
>> making black hole pulsars you know just
a phase where they could look like a
pulsar but be a black hole pulsar but
these days I work a lot in extra spatial
dimensions and the idea that
>> we were joking about our
three-dimensional selves but maybe not
maybe there are these extra dimensions
and we are just bound to ree for reasons
that we try to understand.
>> Wow.
>> And that is actually what I work on
every day these days.
>> That is amazing.
>> Yeah. So,
>> so is it in the context of string theory
or
>> Well, it's not string theory. In fact,
extra dimensions have been around for a
hundred years. As soon as Einstein
started working on spaceime and taking
seriously that space and time were
relative and people started asking well
like why three
>> why three space in one time? Yeah. And
in fact, there was really exciting ideas
that if the universe had higher
dimensions, it would
>> it would explain electromagnetism
as an uh which is one of our fundamental
forces as uh connected to gravity in a
fundamental way. it would unify them
together in a fundamental way that that
the extra dimensions uh could actually
make a a a mode of gravity look like a
photon or something like that.
>> Holy cow.
>> So the extra dimensions as part of
unification long predates string theory
and
>> Oh wow. Okay. And um and it might be
that dark energy is energy trapped in
the extra dimensions. Might be that dark
matter are exitations of the extra
dimensions. It could it could explain a
lot or it might just be that they're
there.
>> So talk about the edge of an
understanding like you're like let me
just take the So it's not motivated
necessarily by we've observed something.
It's more
>> like Einstein did it.
>> I'm dealing with these concepts that I'm
seeing.
>> We have this intuition. We started
looking at some things because when you
move around in in the extra dimensions,
sometimes thing can come things can come
back rotated in a profound way. I can
set a left-handed particle in and it can
come back right-handed. Very strange
things like that. And um and so there's
reasons you start poke noodling around,
but sometimes you don't know what you're
going to find,
>> right? Yeah.
>> And um and so but I say that my work is
unified around space-time themes. that
is almost always so it sounds very
different the big bang black holes extra
dimensions gravitational waves but
they're all really um spac-time
thinking.
>> Yeah. Yeah. You know I've done the same
trick in my career in the sense that I'm
like okay I can compute
>> I understand plasmas and I know how to
experiment. I can go to all these
different areas and
>> and sometimes you just have to to stay
agile.
>> Oh absolutely. Well I get bored
personally. I can't
>> I like to be a student again. So every
few years I have to be a student again.
I like to feel like everyone in the room
knows more than me.
>> Oh, yeah. I mean, my collaborators now
are they're all
>> they can dabble in string theory.
They're more than dabbled. They're all
really accomplished in string theory as
well as other areas of particle physics.
So, it's just a pleasure for me to
>> Well, this interview has been a pleasure
for me. Thank you so much.
>> Thank you so much
>> for expanding my event horizon.
>> Thank you for having me.
>> Awesome. Can't wait till next time. Hey,
Heat. Heat.
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