Kind: captions
Language: en
no surprises here but i've seen my fair
share of sci-fi movies nerds unite
there's something about the laser
battles
and cgi spaceships
and the generally epic soundtracks
[Music]
you could say i'm something of a science
fiction natto
but there's one trope one plot device
one thing that almost always leaves me
with more questions than answers
black
holes
they're like the all-around go-to in
sci-fi they can act as a wormhole that
somehow conveniently links two distant
bits of the universe for space travel
or they can become a dark hungry space
monster that gobbles down everything in
its vicinity
which sounds like a fitting description
of a lot of people come thanksgiving but
let's get away from that mental image
and talk about interstellar instead
approaching the event horizon
port side
dipping down beneath it
to go through it
heading towards
blackness
it's all black
guitars you read me from the scientists
i've talked to for this podcast
interstellar is not only a favorite
sci-fi movie one of the movies that i
enjoyed most was actually interstellar i
am very fond of interstellar i do love
interstellar
interstellar offers us the most accurate
cinematic depiction of black holes we
could hope for
i mean after all they did consult
theoretical physicist kip thorne
gravitational form losing control stick
i want to believe matthew mcconaughey
knows what he's talking about i do i'm
on his side but still this is a made-up
movie so how much do we really know
about black holes
and how much do we think we know
today on nova now universe revealed
we're taking matters into our own hands
and journeying straight into a black
hole to find out just how much is
fiction and how much is reality and here
reporting for duty as your co-pilot i'm
alok patel
in some sense black holes are places not
things
and that's very attractive to me it's
much less gooey and messy and sloppy so
there's something about the purity of
the empty spacetime and the black hole
that's very intriguing
jana levin is a professor of physics and
astronomy at barnard college of columbia
university
she's also an author and general black
hole enthusiast and janna agreed to take
me on a journey into a black hole
specifically the supermassive black hole
at the center of our milky way galaxy
so i was wondering if you and i could
play like sci-fi movie
and we could pretend that we're in a
spaceship and we're ready to head off to
the center of the milky way to go to the
black hole the first thing i need to
know is what are we going to call our
spaceship
[Laughter]
um gosh i don't know i mean
there's this cute trick that when we
name black holes we name them with a
star
so our black hole is called sag a star
sagittarius a star because it's in the
direction of the constellation
sagittarius from our perspective
so i think we should call our
spaceship something like milky way star
milky way star i was gonna like put like
jan levstar in there to try to give a
nod to you
oh you know my animation name is jan 11.
like jan
11.
oh my gosh all right so it's going to be
a play so
our spaceship our spaceship the jan 11
star is now heading towards the
theoretical black hole in the milky way
if you had an educated guess how far
roughly is this from us i mean i i'm
saying like 25 000 light years but yeah
it's between 25 and 27 000 light years
away from us so if we traveled at the
speed of light we would get to the
center of our galaxy and 26 000 light
years let's just land in the middle so
we're
now we're traveling for 26 000 years if
we're going the speed of light which we
can't yet do so i'm assuming that we
have brought snacks and cards and games
to play for this
extended period of time what is
happening to our view
around us as we're getting closer to the
black hole
i think people often think of black
holes as these big
megalith monsters but actually the whole
point is that they're small for their
heft they're actually really hard to see
from far away
so the black hole sagittarius a star
is only about 20 times the width of the
sun across
if you picture the sun on the sky
and you imagine 20 times larger and then
you push it to 26 000 light years that
thing is as small as a piece of fruit on
the moon
from where we're standing
so you don't see a lot until you get
very very close
you have to get really up up in its face
and then you start to see that it's
bending the shape of space-time and so
the path of light is bent around it and
so it's like a lens it's like you only
notice it's there because there's a
shadow
and because it's causing the distortion
of things behind it that's the only
reason you know it's there
since we have 26 000 light years to
travel we've got a few minutes to wrap
our heads around black holes we first
need to talk about space time
not space and time but space time one
word
the idea of space-time is part of albert
einstein's theory of special relativity
in this theory
space and time are woven together into a
four-dimensional fabric called
space-time with three dimensions of
space and one dimension of time
connecting space and time isn't actually
that foreign to us
think about every time you've made a
plan to see someone you have to agree on
both a place to meet up and a time to be
there
janna and i agreed to meet on the gen 11
star spacecraft right now so that we
could journey into a black hole together
if we hadn't agreed on a time jenna
might be in the middle of teaching one
of her classes and if we hadn't agreed
on a place i might be light years away
from janet by now simple enough right
but get this not only are time and space
woven together like a fabric that fabric
is flexible like a trampoline or the
skin of a drum capable of being
stretched or bent by objects with mass
or energy one familiar example of the
bending of space-time is gravity the
funny thing about gravity is we think
it's such a dominant
force in our experience but it's
actually really really weak i mean the
whole earth is pulling on me and i can
still lift my water
you know
it requires incredible concentrations of
mass and energy to notice that things
are deforming space and time but the
idea is that
yeah matter and energy curve space and
time and then that space time tells
everything else how to fall
weightlessly and freely around those
curves in space and time so one way to
think of it is like this if i were to
take one of these books off the shelf
and i was to throw one of them
we know it would not travel on a
straight line
and during the time that that book is
falling freely uninterrupted by the
floor of my office or by a chair
anything else getting in its way during
the time that it's falling freely we
know it traces a curved path
and that should be the first observation
that it's following a curved trajectory
in spacetime which is crazy i can
literally go around the globe throwing
things
and everything will follow arcs and
curved paths and i can map
the shape of space-time around the earth
that way
the gravity we experience on earth is
weak enough that we can lift objects or
walk around or slam dunk on the b-ball
court
but a black hole is a place where
gravity is so intense that not even
light can escape and the gravity gets
that strong because an incredibly large
amount of matter has been squeezed into
an incredibly tiny space
so what do curves in space time have to
do with black holes
let's start at the moment a black hole
is born
one way scientists believe black holes
are created is through the death of
certain stars
so imagine a star is collapsing under
its own weight but at some point it does
get so dense that it creates a black
hole and what we really mean by that is
that it has deformed the space time
around it so substantially that it has
left almost as an archaeological imprint
on the space-time behind it
a curve so deep
that not even light can escape it would
have to travel faster than the speed of
light to escape again
and it can't do that and nothing can do
that so it falls in
so it leaves an emptiness behind
not even the light from the star
is there
the black hole is just an empty shadow
and there's no more there in the shadow
than there is in the shadow of a tree
you said early on that the way we can
tell
we're approaching the black holes not
necessarily because we see this
pitch-black
ominous beautiful object or lack of
object but we see light bending
we see a shadow
and the light bending around this
darkness so if you saw the image that
was released in 2019
which is the first time we've ever
actually seen an image of a black hole
which is an absolutely stunning human
achievement
shep doleman of harvard was the pi on
the event horizon telescope project and
drove that forward took him 20 years you
know as a real labor of love
we are delighted
to be able to report to you today
that we have seen what we thought was
unseeable
we have seen
and taken a picture
of a black hole
here it is
[Music]
[Applause]
that's shep doleman unveiling the first
picture ever taken of a black hole it
looks like a bright fiery glowing blob
with a dark circle in the center kind of
like a fancy artisanal space donut i'm
looking at the picture right now and
it's beautiful and kind of scary at the
same time and what they took a picture
of was the shadow right so just like a
tree's shadow in midnight there's no
such thing
you can't see a tree's shadow
in darkness you need to have some source
of light
and so what they looked for was the
bright light around the black hole
casting the shadow
when material falls towards the black
hole the matter and light spiral around
it like water going down a drain
this creates a bright ring around the
dark black hole in the center and
in the rim of that bright light you see
this utter darkness which is the empty
space of the black hole event horizon
what exactly is the event horizon that's
the point at which the shadow is cast it
is an empty region of space
at which you would have to travel faster
than the speed of light to escape and
it's like saying what's the shadow of a
tree
it's not like there's a thing in the
shadow of the tree
it's just the region where light doesn't
penetrate
[Applause]
alright we've now traveled most of our
26 000 light year journey
as we get closer to the black hole we
see the light bending around it
leaving a dark shadow
but since we aren't yet at the event
horizon we're still safe in our
spacecraft so you can safely set up an
orbit on a bent path around a black hole
it's very convenient that black holes
bend space time as does the earth the
reason why the international space
station is in orbit around the earth is
because the earth has curved spacetime
in such a way that we can find a
circular curved path around the earth
it's fantastic so we love it we send
spacecraft up above the earth we turn
off their engines and we let them free
fall they just always clear the horizon
and they travel in a curved path and
they never hit the earth and they're not
burning any fuel whatsoever
they're just literally just free falling
and so similarly you can do the same
thing around a black hole you can safely
orbit a black hole it's completely fine
and that's the benefit of the curved
space time
my other question is as we start to get
closer
to the black hole what is happening to
our speed of our spacecraft what's
happening to the speed of matter around
us as we get closer so let's say
you and i are in orbit in the jan
11 star
spacecraft
and we're you know
we're arguing
and you throw me out of the spacecraft
and i fall into the black hole
or vice versa or vice versa or i throw
you out of the stage hey wait
we will start to notice that our very
excellent swiss watches that were
designed to be totally not lose a second
and are accurate begin to fall out of
sync so you're approaching the event
horizon the black hole your watch will
begin to look really lagging behind mine
but your experience of time is
completely natural it's not as though
you think time is slow it's not like
your biological clock is immune from the
same physical consequences this is a
completely real
slowing of the passage of time
for you relative to me so you will be
like
metabolizing food really slowly your
neurons will be firing really slowly not
for you
but just from my perspective i'll be
wondering what is going on with you and
similarly i'll look like i'm very sped
up and
the funny thing is that you have to get
really really close to the black hole
for this to be extreme
and the closer and closer you get to a
black hole it can get to the point where
two minutes have passed for you
and 20 years have passed for me
whoa
okay so how far away from sagittarius a
star would this be happening you said it
was a very very very close very close
[Music]
agonizingly dangerously close
but do not cross it
and then you burn an incredibly
expensive amount of fuel
to get back out yes i could be 60 years
older and you could be two minutes older
and you would look at me and i'd be old
i would be like crazy old and it would
be real and i would have grandchildren
and great-grandchildren and that would
be real
you know they would have new lives and
they'd have gone to college and they'd
have had experiences and you'd be two
minutes older
that's real
i'm literally speechless right now cause
i'm like oh my gosh but okay and then in
this in this moment when i'm dangerously
close can i feel would i feel something
like a suction or a force pulling me
into
the event horizon
it's actually another one of these myths
i love to dispel black holes are pretty
harmless like
if you think about the curvature of the
earth you hardly notice it walking
around you don't notice it at all
but the smaller
a curved object you stand on the more if
you stood on a basketball you'd
definitely be struggling to balance
right
so black holes are similar the bigger
the black hole the less you notice
you would drift across the event horizon
and nothing would happen to you the
smaller the black hole the more likely
you would feel the effects just like the
basketball
you would feel
that you were being like oh man my left
foot my right foot are not on an equal
footing and i'm starting to feel the
pull differently from my head to my feet
so weirdly the bigger the black hole the
less you notice it at least initially
you're in real trouble once you're
inside
okay this is the space where we say it's
time for a quick break
after which we'll get into that real
trouble the point of no return
when we return
[Music]
welcome back aboard the jan 11 star
spacecraft safely orbiting the black
hole at the center of the milky way
known as sagittarius a star
before the break janna and i were
talking about the event horizon
sometimes referred to as the point of no
return
because once you cross it all the fuel
in the universe won't allow you to
escape the event horizon it's probably
very dark in this black hole in the
sense where there's no there's funnily
enough black holes can be bright on the
inside even if they're dark on the
outside because all of the light from
the galaxy can fall in behind you so it
can be really bright on the inside you
can see
the results of the climate change crisis
you can see
civilizations come and go you can see
the election of 2024 you can see
stars be born and die
all in a flash of a microsecond for you
before you're crushed to death in the
center
so it can be very bright on the inside
before talking to you i was scared of
black holes and now i want to dive into
one of them
black holes might be bright on the
inside and dark on the outside
but there are occasions when
supermassive black holes create powerful
jets of radiation and particles that
shoot out in narrow beams
[Music]
i mean if light can't escape a black
hole where do these bright jets come
from
so the black hole is like
sharks swirling around in the water
creating waves it's not that the shark
is disgorging
water
it's that it's churning up water and
it's creating waves and so the black
hole is churning up
electromagnetic energy
and it's creating a source of power and
energy none of the matter originates
from inside the black hole
it all has to come from outside the
black hole so it's disrupted stars it's
torn apart other solar systems and it's
throwing them out into these fantastic
jets but again none of it comes from
inside the black hole the irony is that
the darkest phenomenon conceivable in
the universe becomes the brightest
beacon in the actual universe
this is so wild
you know i'm i can't help i can't help
but now start to think about
some of the concepts of black holes
we've seen in science fiction television
and you know one thing i have to ask is
it is the whole concept of a wormhole
which
it sounds so bizarre to me but is it
is it even theoretically possible yeah
that black holes can somehow transport
matter to another point in the universe
wow so that's gone
all over the place for a hundred years
and this is what i love about
theoretical physics is it's okay to
dream
and to be wrong
and then it sits on the shelf like a
great book for a while and then it comes
back again and somebody's like wait
didn't somebody say something about this
70 years ago and this is kind of what's
happening with wormhole physics so
the way to think about it is like i'm
right now on the fifth floor of a
building at barnard college
and there's a wormhole which exists to
get me to the fourth floor it's called a
stairwell
and if that wormhole didn't exist it'd
have to go a long way around
right
the wormhole is like a little shortcut
somebody built for me now we actually
think that there are these black hole
wormholes which are quantum
quantum which relates to the physical
behavior of very very small stuff like
atoms and subatomic particles in quantum
mechanics two different particles can
become entangled meaning they're linked
even though they exist in different
points in space
this is known as quantum entanglement
but that connection on the quantum level
might actually be able to act as a
wormhole
maybe black holes
actually emerge out of the entanglement
of a bunch of quantum wormholes
and that in some sense the black hole
isn't the fundamental thing but the
wormholes are the fundamental thing
from our macroscopic perspective we
think there's a black hole but when we
come up close we realize oh it's just
layers and layers and layers of quantum
wormholes
it's amazing how everything and anything
is potentially possible here one
question i forgot to ask you
you know you talked about light and how
it could potentially be bright do black
holes inside do this sound like anything
oh black holes sound like something from
the outside for sure
so we have recorded the sound of black
holes
one way to imagine is so if black holes
curve space time
then if they move the curves in space
time have to follow them
and because of the limit of the speed of
light they can't follow faster than the
speed of light it takes them a while
right to catch up to the moving black
hole and so what's actually created is
if a black hole moves there are waves in
the shape of space time
as the curves in space time try to catch
up to the black hole
a black hole wanders close to another
black hole they become engaged in a
gravitational dance until they
eventually merge
as they orbit around each other
they not only curve space-time they
create waves within it and these two
black holes are like mallets on a drum
they're creating waves in the shape of
the drum of space-time and those waves
are basically unimpeded because gravity
is so weak so like let's say you create
a curve in the shape of space-time and
it begins to wobble
in response to the motion of the black
holes it can travel like wobbling and
traveling like that we call them
gravitational waves and in fact we
record them very much like you would
record the ringing shape of a drum and
we play it back as sound
because that's the natural translation
fact is if you sit in the control room
of these experiments which is one the
main one is called ligo there's other
virgo and there's a chicagra
that trio of experiments around the
globe play them back in the control room
through conventional speaker systems oh
my like you can listen to the machine
and you can listen
to the first discovery in 2015 of black
holes ringing the shape of space-time it
happens
by coincidence to be in the human
auditory range
ligo this instrument is famously
sensitive to the same range of
frequencies that the piano plays
ligo stands for laser interferometer
gravitational wave observatory
listen to the sound of the gravitational
waves caused by two black holes merging
captured by ligo in september 2015.
as two black holes close in on each
other circling faster and faster both
the frequency and amplitude of the waves
they create increase
translated to audio this means the pitch
and volume of the sound increase
so as black holes merge the resulting
sound resembles little chirps
ironically these chirps might sound
small but they're the result of a huge
and powerful cosmic event that first
detection in 2015
was the most powerful event human beings
have ever observed
since the big bang
and none of it came out as light
all of it came out in the ringing of the
shape of space-time which we recorded by
the time it got here it was painfully
quiet which is why the experiment was
such an achievement
but it was one of the most energetic
events in the history of the universe
i was going to ask you what all this
knowledge
about black holes what it means for us
here on earth and how we're applying it
to other questions
2015 that moment
had to represent something very
important in terms of our our
understanding of black holes but also
what it means for us to be studying them
i love that question so
it was august right before
the event was recorded
and ray weiss who has since won the
nobel prize and was one of the major
architects of the instrument had spent
50 years of his life on this
and the first instrument was built in
2000 and crickets crickets
right
15 years later they installed the
advanced machine
we're on the eve of the immense machine
and he says to me if we don't detect
black holes this is a failure
and it's such an honest painfully honest
statement
from a scientist who's devoted
literally his whole life to it
it was a labor of love it was a labor of
curiosity
so it's just something about the human
ambition why do we go on hikes why do we
want to look from the top of mountain
out of view why do we want to know
things why do we want to read books why
do we want to write books because that's
who we are as a species we might be a
complicated
failed species but that's probably our
best side
[Music]
so now
i went against your advice i was like
i'm on jan 11 star but i'm going into
these black holes i dive into the black
hole you say don't do it i will never
see you again i say but i must do this
in the name of science so what happens
to me what happens to matter to bodies
so if you fall into a black hole the
size of the sun you have microseconds
before you begin to notice on the
interior that your feet are being pulled
more strongly than your head
and that you're being crushed
towards the singularity towards the
center of the black hole the singularity
is hypothesized and even if it isn't
real a region of infinite curvature
infinite gravity infinite destiny even
if it isn't real it's definitely the
case that as you approach that special
point the curves in spacetime become
very extreme
simply put
singularities are places where our laws
of physics and math break down
like how dividing by zero has no answer
it's undefined
gravitational singularities are places
where the gravity density and curvature
of space-time are infinite
which basically means it's going to be a
bumpy ride
and so you begin to become played you
would be torn apart
your ligaments would be torn as i fall
into the black hole feet first
the gravity pulls more forcefully on my
feet than my head
causing my body to stretch out longer
and longer until i'm elongated into a
string one atom wide
it's a process
fittingly referred to as
spaghettification
you would be ripped into your
fundamental particles and then those
fundamental particles would have to find
their way towards the center of the
black hole
in fact
find their ways really the wrong way of
saying it there would be forced forced
towards the center of the black hole the
center of the black hole is as
inevitable as the future
because the black hole in some sense has
switched
the placement of space and time
so from the outside what we point to is
the center of the black hole
for a person on the inside is a point in
time it's the future
and they can no more avoid
the singularity or whatever's in the
center then they can avoid the next
moment in time
[Music]
nova now universe revealed is a
production of gbh and prx it's produced
by teres bernardo jenny cataldo ari
daniel caitlyn falz and jocelyn gonzalez
julia court and chris schmidt are the
co-executive producers of nova suki
bennett is senior digital editor
christina manan is associate researcher
robin kasmer is science editor robert
boyd is digital associate producer
shyla duff is digital video intern and
devin maverick robbins is managing
producer of podcasts at gbh
i'm alok patel
we'll be back next week with our final
episode of the series looking way back
to where it all began
the big bang
if you love stories about our universe
visit pbs.org nova now podcast and check
out nova universe revealed a five-part
film series about the same topics we're
discussing right here like mysteries of
black holes you can check it out
streaming now on the pbs video app visit
pbs.org nova
this podcast has been made possible by
the gordon and betty moore foundation
gbh
[Music]