The sound the universe makes Janna Levin

I want to ask you all to consider for a

second the very simple fact that by far

most of what we know about the universe

comes to us from light we can stand on

the earth and look up at the night sky

and see stars with our bare eyes the Sun

burns our peripheral vision we see light

reflected off the moon and in the time

since Galileo pointed that rudimentary

telescope at the celestial bodies the

known universe has come to us through

light across vast eras in cosmic history

and with all of our modern telescopes

we’ve been able to collect this stunning

silent movie of the universe these sort

of series of snapshots that go all the

way back to the Big Bang and yet the

universe is not a silent movie because

the universe isn’t silent

I’d like to convince you that the

universe has a soundtrack and that

soundtrack is played on space itself

because space can wobble like a drum it

can ring out a kind of recording

throughout the universe of some of the

most dramatic events as they unfold now

we’d like to be able to add to a kind of

glorious visual composition that we have

of the universe a sort of sonic

composition and while we’ve never heard

the sounds from space we really should

in the next few years start to turn up

the volume on what’s going on out there

and so in this ambition to capture songs

from the universe we turn our focus to

black holes and the promise they have

because black holes can bang on

space-time like mallets on a drum and

they have a very characteristic song

which I’d like to play for you some of

our predictions for what that song will

be like now black holes are dark against

a dark sky we can’t see them directly

they’re not brought to us with lights at

least not directly

we can see them indirectly because black

holes are weak havoc on their

environment they destroy stars around

them

they churn up debris in their

surroundings but they won’t come to us

directly through light we might one day

see a shadow a black hole can cast on a

very bright background but we haven’t

yet and yet black holes may be heard

even if they’re not seeing and that’s

because they bang on space-time like a

John now we owe the idea that space can

ring like a drum to Albert Einstein to

whom we owe so much iron Stein realized

that if space were empty if the universe

were empty it would be like this picture

except for maybe without the helpful

grid drawn on it but if we were freely

falling through the space even without

this helpful grid we might be able to

paint it ourselves because we would

notice that we traveled along straight

lines undeflected straight paths through

the universe Einstein also realized and

this is the real meat of the matter that

if you put energy or mass in the

universe it would curve space and a

freely falling object would pass by

let’s say the Sun and it would be

deflected along the natural curves in

that space it was Einstein’s great

general theory of relativity

now even light will be bent by those

paths and you can be bent so much that

you’re caught in orbit around the Sun as

the earth is or the moon around the

earth these are the natural curves in

space what Einstein did not realize was

that if you took our Sun and you crushed

it down to six kilometers so you took a

million times the mass of the earth and

you crushed it to six kilometers across

you would make a black hole an object so

dense that have light veered too close

it would never escape a dark shadow

against the universe it wasn’t Einstein

who realized this it was Karl

Schwarzschild who was a German Jew in

World War one joined the German army

already an accomplished scientist

working on the Russian front who I like

to imagine Schwartz shield in the war in

the trenches you know calculating

ballistic trajectories for cannon fire

and then in between calculating

Einstein’s equations you know as you do

in the

and he was reading Einsteins recently

published general theory of relativity

and he was thrilled by this theory and

he quickly surmised an exact

mathematical solution that describes

something very extraordinary curves so

strong that space would rain down into

them space itself would curve like a

waterfall flowing down the throat of a

hole and even the light could not escape

this current light would be dragged down

the hole as everything else would be in

all that would be left would be a shadow

now he wrote to Einstein and he said as

you will see the war has been kind to me

enough between despite the heavy gunfire

I’ve been able to get away from it all

and walk through the land of your ideas

and Einstein was very impressed with

this exact solution and I should hope

also the dedication of the scientist you

know this is the hard-working scientist

under harsh conditions and he took short

shields idea to the Prussian Academy of

Sciences the next week

but Einstein always thought black holes

were a mathematical oddity he did not

believe they existed in nature he

thought Nature would protect us from

their formation it was decades before

the term black hole was coined and

people realized that black holes are

real Astrophysical objects in fact

they’re the death state of very massive

stars that collapse catastrophic ly at

the end of their lifetime now our Sun

will not collapse to a black hole it’s

actually not massive enough but if we

did a little thought experiment as

Einstein was very fond of doing we could

imagine putting the Sun crushed down to

six kilometers and putting a tiny little

earth around it in orbit maybe 30

kilometers outside of the black hole Sun

and it would be self illuminated because

now the sun’s gone we have no other

source of light so let’s make our little

earth self illuminated and you would

realize you could put the earth in a

happy orbit even 30 kilometers outside

of this crushed black hole this crushed

black hole actually would fit inside

Manhattan more or less it would it might

spill off into the Hudson a little bit

before it destroyed the earth but you

know basically that’s what we’re talking

about talking about an object you could

crush down two

the square area of Manhattan so we move

this earth very close 30 kilometers

outside and we notice it’s perfectly

fine

orbiting around the black hole there’s a

sort of myth that black holes devour

everything in the universe but you

actually become very close to fall in

but what’s very impressive is that from

our vantage point we can always see the

earth it cannot hide behind the black

hole the light from the earth some of it

falls in but some of it gets lens de

round and brought back to us so you

can’t hide anything behind a black hole

if this were Battlestar Galactica and

you’re fighting the Cylons don’t hide

behind the black hole you know they can

see you okay now our Sun will not

collapse to a black hole it’s not

massive enough but there are tens of

thousands of black holes in our galaxy

and if one were to eclipse the Milky Way

this is what it would look like we would

see a shadow of that black hole against

the hundred billion stars in our Milky

Way galaxy and its luminous dust lanes

and if we were to fall towards this

black hole we would see all of that

light lens de round it and we could even

start to cross into that shadow and

really not notice that anything dramatic

had happened it would be bad if we tried

to fire our Rockets and get out of there

because we couldn’t any more than light

can escape but even though the black

hole is dark from the outside it’s not

dark on the inside because all of the

light from the galaxy can fall in behind

us and even though do a relativistic

effect known as time dilation our clocks

would seem to slow down relative to

galactic time it would look as though

the evolution of the galaxy had been

sped up and shot at us right before you

know we were crushed to death by the

black hole it would be like a near-death

experience where you see the light at

the end of the tunnel but it’s like a

total death experience

and there’s no way of telling anybody

about the light at the end of the tunnel

now we’ve never seen a shadow like this

of a black hole but black holes can be

heard even if they’re not seen imagine

now taking an Astra physically realistic

situation imagine two black holes that

have lived a long life together maybe

they started as stars and collapsed to

two black holes each one ten times the

mass of the Sun so now we’re going to

crush them down 260 kilometres across

they can be spinning hundreds of times a

second at the end of their lives they’re

going around each other very near the

speed of light so they’re crossing

thousands of kilometres in a fraction of

a second and as they do so they not only

curve space but they leave behind in

their wake a ringing of space an actual

wave on space time-space squeezes and

stretches as it emanates out from these

black holes banging on the universe and

they travel out into the world into the

cosmos at the speed of light this

computer simulation is due to a

relativity group at NASA Goddard it took

almost 30 years for anyone in the world

to crack this problem this was one of

the groups it shows two black holes in

orbit around each other again with these

helpfully painted curves and if you can

see it’s kind of faint but if you can

see the red waves emanating out those

are the gravitational waves they’re

literally the sounds of space ringing

and they will travel out from these

black holes at the speed of light as

they ring down and coalesce to one

spinning quiet black hole at the end of

the day if you were standing near enough

your ear would resonate with the

squeezing and stretching of space you

would literally hear the sound now of

course your head would be squeezed and

stretched unhelpfully so you might have

trouble understanding what’s going on

but I’d like to play for you the sound

that we predict this is from my group a

slightly less glamorous computer

modelling but imagine a lighter black

hole falling into a very heavy black

hole the sounds you’re hearing is a

light black hole banging on space each

time it gets close if it gets far away

it’s a little too quiet

but it comes in like a mallet and it

literally cracks space wobbling it like

a drum and we can predict what the sound

will be we know that as it falls in it

gets faster and it gets louder and

eventually we’re going to hear the

little guy just fall into the bigger guy

and it’s gone now I’ve never heard it

that loud it’s actually more dramatic at

home it sounds kind of anticlimactic

it’s like ding-ding thing this is

another sound from my group now I’m not

showing you any images because black

holes don’t leave behind helpful trails

of ink and space is not painted showing

you the curves but if you’re ready float

by in space on a space holiday and you

heard this you want to get moving

want to get away from the sound both

black holes are moving both black holes

are getting closer together in this case

they’re both wobbling quite a lot and

then they’re going to merge

yeah that’s gone now that chirp is very

characteristic of black holes merging

that it chirps up at the end now

that’s our prediction for what we’ll see

luckily we’re at the safe distance in

Long Beach California and surely

somewhere in the universe two black

holes have merged and surely the space

around us is ringing after maybe

traveling a million light-years or a

million years at the speed of light to

get to us but the sound is too quiet for

any of us to ever hear there are very

industrious experiments being built on

earth one called LIGO which will detect

deviations in the squeezing and

stretching of space at less than the

fraction of a nucleus of an atom over

four kilometers it’s a remarkably

ambitious experiment and it’s going to

be an advanced sensitivity within the

next few years to pick this up there’s

also a mission proposed for space which

hopefully will launch in the next ten

years called Lisa and Lisa will be able

to see supermassive black holes black

holes millions or billions of times the

mass of the Sun in this Hubble image we

see two galaxies they look like they’re

frozen and some embrace and each one

probably harbors a supermassive black

hole at its core but they’re not frozen

they’re actually merging these two black

holes are colliding and they will merge

over a billion year timescale it’s

beyond our human perception to pick up a

song of that duration but Lisa could see

the final stages of two supermassive

black holes earlier in the universe’s

history the last 15 minutes before they

fall together and it’s not just black

holes but it’s also any big disturbance

in the universe and the biggest of them

all is the Big Bang you know when that

expression was coined it was derisive

like oh who would believe in a Big Bang

you know but now it actually might be

more technically accurate because it

might bang it might make a sound

this animation for my friends at proton

studio shows looking at the Big Bang

from the outside we don’t ever want to

do that actually we want to be inside

the universe because there’s no such

thing as standing outside the universal

you’re inside the BIGBANG it’s

everywhere it’s all around you in the

spaces wobbling chaotically 14 billion

years past and this song is still

ringing all around us galaxies form and

generations of stars form in those

galaxies and around one star at least

one star is a habitable planet and here

we are frantically building these

experiments doing these calculations

writing these computer codes imagine a

billion years ago two black holes

collided that song has been ringing

through space for all that time we

weren’t even here you know it gets

closer and closer 40,000 years ago we’re

still doing cave paintings

it’s like hurry build your instruments

getting closer and closer and in 20

whatever year it will be when our

detectors are finally at an advanced

sensitivity we’ll build them we’ll turn

the machines and bang we’ll catch it the

first song from space if it was the Big

Bang that we were going to pick up it

would sound like this it’s a terrible

sound it’s literally the definition of

noise it’s white noise it’s such a

chaotic ringing but it’s around us

everywhere presumably if it hasn’t been

wiped out by some other process in the

universe and if we pick it up it will be

music to our ears because it will be the

quiet echo of that moment of our

creation of our observable universe so

within the next few years we’ll be able

to turn up the sound track a little bit

render the universe in audio but if we

detect those earliest moments it’ll

bring us that much closer to an

understanding of the Big Bang which

brings us that much closer to asking

some of the hardest most elusive

questions if we run the movie of our

universe backwards we know that there

was a big bang in our past and we might

even hear the cacophonous sound of it

but was our Big Bang the only Big Bang I

mean we have to ask has it happened

before will it happen again I mean in

the spirit of rising to Ted’s challenge

to reignite wonder we can ask questions

at least for this last minute that

honestly might evade us forever but we

have to

is it possible that our universe is just

a plume off of some greater history or

is it possible that we’re just a branch

off of a multiverse each branch with its

own Big Bang in its past maybe some of

them with black holes playing drums

maybe some without you know maybe some

with sentient life and maybe some

without not in our past not in our

future but somehow fundamentally

connected to us so we have to wonder if

there is a multiverse in some other

patch of that multiverse are there

creatures here’s my multiverse creatures

are there other creatures in the

multiverse wondering about us and

wondering about their own origins and if

they are I can imagine them as we are

calculating writing computer code

building instruments trying to detect

that faintest sound of their origins and

wondering who else is out there thank

you