1.3 billion years ago in a distant
distant galaxy two black holes locked
into a spiral falling inexorably towards
each other and collided converting three
sons worth of stuff into pure energy in
the tenth of a second for that brief
moment in time the glow was brighter
than all the stars in all the galaxies
in all of the known universe
it was a very big bang but they didn't
release their energy in light
I mean you know they're black holes all
that energy was pumped into the fabric
of space and time itself making universe
explode in gravitational waves let me
give you a sense of the time scale at
work here 1.3 billion years ago earth
had just managed to evolve multicellular
life since then earth is made and
evolved corals fish plants dinosaurs
people and even got to use the internet
about 25 years ago a particularly
audacious set of people realize that MIT
kip thorne and Ronald raver at Caltech
decided that it would be really neat to
build a giant laser detector with which
to search for the gravitational waves
from things like colliding black holes
the most people thought they were not
but enough people realized that they
were brilliant knots that the US
National Science Foundation decided to
fund their crazy idea
so after decades of development
construction and imagination and
breathtaking amount of hard work they
built their detector called ligo the
laser interferometer gravitational-wave
Observatory for the last several years
like has been undergoing a huge
huge expansion in his accuracy a
tremendous improvement in its detection
ability it's now called advanced LIGO as
a result in early September of 2015 ligo
turned on for a type final test run
while they started out a few lingering
details and on sep tember 14 of 2015
just days after the detector had gone
live the gravitational waves from those
colliding black holes pass through the
earth and they pass through you and me
and they pass through the detector
there's two moments in my life that are
more emotionally intense than that one
is the birth of my daughter it
the other is what I had to say goodbye
to my father when he was terminally ill
you know it was the payoff of my career
basically everything they've been
working a lot it's no longer science
fiction so that's my very good friend
and collaborator Scott Hughes
theoretical physicist at MIT who has
been studying gravitational waves from
black holes and the signals that they
could impart on observatories like Lego
for the past 23 years
let me take a moment to tell you what i
mean by a gravitational wave the
gravitational wave is a ripple in the
shape of space and time as the wave
passes by it stretches space and
everything in it in one direction and
compresses it in the other
this has led to countless instructors of
general relativity doing a really silly
dance to demonstrate in their classes on
general relativity it stretches and
expands stretches so the trouble with
gravitational waves is that they're very
weak their preposterous Lee week for
example the waves that hit us on sep
tember 14 and yes every single one of
you stretched and compressed under the
action of that wave when the waves hit
they stretch the average person by one
part in 10 to the 21
that's a decimal place 2000
and a one that's why everyone thought
the LIGO people were not even with a
laser detector five kilometers long and
that's already crazy they would have to
measure the length of those detectors to
less than 1000 of the radius of the
nucleus of an atom and that's
preposterous
so towards the end of his classic texts
on gravity like a co-founder Kip Thorne
describe the hunt for gravitational
waves as follows he said the technical
difficulties to be surmounted in
constructing such detectors are enormous
but physicists are ingenious and with
the support of a broadly public all
obstacles will surely be overcome
thorn published that in 1973 42 years
before he succeeded and coming back to
lego Scott likes to say that like Oh
acts like a year more than it does like
an I don't explain what that means
visible light has a wavelength the size
that's much smaller than the things
around you the features on people's
faces the size of your cell phone and
that's really useful because it lets you
make an image or a map of the things
around you by looking at the light
coming from different spots in the scene
about you sound is different
audible sound has a wavelength that
could be up to 50 feet long and that
makes it really difficult in fact in
practical purposes impossible to make an
image of something you really care about
your child's face instead we use sound
to listen for features like pitch and
tone and rhythm and volume to infer a
story behind the sounds that's Alice
talking that's Bob interrupting silly
Bob so the same is true of gravitational
waves we can't use them to make simple
images of things out in the universe but
by listening to changes in
the amplitude and the frequency of those
waves we can hear the story that those
waves are telling and at least four ligo
the frequencies that it can hear are in
the audio band so if we convert the wave
patterns into pressure waves and error
into sound we can literally hear the
universe speaking to us for example
listening to gravity just in this way
can tell us a lot about the collision of
two black holes something that my
colleague Scott has spent an awful lot
of time thinking about if the two black
holes are non spinning you get a very
simple chirp work if the two bodies are
spinning very rapidly i have that same
sharp but with a modulation on top of it
so it kind of goes really remember it's
sort of the vocabulary of spin imprinted
on this waveform so on sep tember 14
2015 a day that's definitely gonna live
in my memory ligo heard this so if you
know how to listen
that is the sound of two black holes
each of about thirty solar masses that
were whirling around at a rate
comparable to what goes on in your
blender it's worth pausing here to think
about that means two black holes the
dentist thing in the universe one with a
massive 29 sons and one with the mass of
36 sons whirling around each other a
hundred times per second before they
collide just imagine power of that
fantastic and we know it because we
heard it
that's the lasting importance of ligo
it's an entirely new way to observe the
universe that we've never had before
it's a way that lets us hear the
universe and here the invisible and
there's a lot out there that we can't
see in practice or even in principle so
supernova for example I would love to
know why very massive stars explode in a
supernova they're very useful
we learned a lot about the universe from
them the problem is all the interesting
physics happens in the core and the core
is he
behind thousands of kilometers of iron
and carbon and silicon will never see
through its opaque the light
gravitational waves go through iron as
if it were glass totally transparent the
big bet i would love to be able to
explore the first few moments of the
universe will never see them because the
Big Bang itself is obscured by its own
afterglow with gravitational waves we
should be able to see all the way back
to the beginning perhaps most
importantly i'm positive that there are
things out there we've never seen that
we may never be able to see and we
haven't even imagined things that will
only discovered by listening and in fact
even in that very first event like oh
found things that we didn't expect
here's my colleague and one of the key
members of the lego collaboration Matt
Evans my colleagues at MIT addressing
exactly that we're kind of stars which
produced the black hole but we observed
hear about the dinosaurs of the universe
for these massive things that are all
from prehistoric times and the black
holder colloquy dinosaur bones of what
we do archaeology so it plus really have
a whole nother angle on what's out there
in the universe and how the stars can be
the end of course how we can't be out of
this whole match our challenge now is to
be as audacious as possible thanks to
like oh we know how to build exquisite
detectors that can listen to the
universe to the russell and the chirp of
the cosmos our job is to dream up and
build new observatories a whole new
generation observatories on the ground
in space
I mean what could be more glorious than
listening to the Big Bang itself
our job now is to dream big dream with
us thank you
I had throughout the only person around
it doesn't have TV coverage to the face
and then he got the black up now you're
gonna be getting a TV picture now we are
getting
vector
I want all
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