Dr. France Córdova, Director, National Science
Foundation Good morning. Welcome to our distinguished visitors, members
of the press, NSF staff, and National Science Board members, represented by Dr. Maria Zuber
of MIT. Scientists from the LIGO, Virgo, and GEO scientific
collaborations, members of the Caltech and MIT communities, and all our guests. I specifically want to recognize representatives
from the Max Planck Society, the UK Science and Technology Facilities Council, and the
Australian Research Council, whose generous contributions have also helped bring us to
today. I'm Dr. France Córdova, the director of the
National Science Foundation. Without a doubt, the reason so many of us
are here today is because we believe in the potential of the Laser Interferometer Gravitational-Wave
Observatory. Opening a new observational window would allow
us to see our universe and some of the most violent phenomena within it in an entirely
new way. Since the mid-1970s, the National Science
Foundation has been funding the science that ultimately led to LIGO's construction. And in 1992, when then NSF director, Walter
Massey and the National Science Board approved LIGO's initial funding, it was the largest
investment NSF had ever made. It was a big risk, but the National Science
Foundation is the agency that takes these kinds of risks. We support fundamental science and engineering
at a point along the road to discovery where that path is anything but clear. NSF funds trailblazers. It's why the U.S. continues to be a global
leader in advancing knowledge. So, without further delay, because I, too,
am eager to hear the latest updates from LIGO's lead scientist, let's kick things off with
a video, and then go to Dave Reitze for, who is LIGO's executive director. Video begins David Reitze
Gravitational waves were predicted by Einstein about a hundred years ago, and they are dynamical
perturbations in the fabric of space time. Ripples in space time, if you will. Rainer Weiss
The gravitational wave stretches space in one direction and compresses space in the
other direction. David Reitze
Nobody really believed that you could ever detect them, because the size of the effect
is so small. Rainer Weiss
I came to the conclusion that, yeah, if you made this long enough-- David Reitze
Nobody had ever made something like this before, so there was a lot of technological challenges
that needed to be overcome. Dr. France Córdova
That's what scientific discovery is really all about. You don't choose the simple things to do. Rainer Weiss
We have done something which is brand new. David Reitze
Field has busted wide open. Gabriele Gonzalez
It's monumentic. It's like Galileo using the telescope for
the first time. Kip Thorne
I looked at it, and I thought, my god, this looks like it's it. Video ends David Reitze, LIGO Laboratory Executive Director,
Caltech Ladies and gentlemen, we have detected gravitational
waves. We did it. I am so pleased to be able to tell you that. So, these gravitational waves were produced
by two colliding black holes that came together, merged to form a single black hole about 1.3
billion years ago. They were detected by LIGO, the Laser Interferometer
Gravitational-Wave Observatory. LIGO is the most precise measuring device
ever built. Let me start with what we saw. So, on September 14th, 2015, the two LIGO
observatories, in Hanford, Washington and Livingston, Louisiana, recorded a signal nearly
at the same time, nearly simultaneously. And the signal had a very specific characteristic,
a characteristic of as time went forward, the frequency went up. And, what was amazing about this signal is
that it's exactly what you would expect, what Einstein's theory of general relativity would
predict for two big, massive objects like black holes in-spiraling and merging together. Now, it took us months of careful checking,
re-checking, analysis, looking at every piece of data to make sure that what we saw was
not something that wasn't a gravitational wave, but in fact, it was a gravitational
wave, and we've convinced ourselves that's the case, and we're here to announce that,
that today. But I do want to say something else. This, this is not just about the detection
of gravitational waves. That's the story today. But what's really exciting is what comes next,
right. It's 400 years ago, Galileo turned a telescope
to the sky and opened the era of modern observational astronomy. I think we're doing something equally important
here today. I think we're opening a window on the universe,
the window of gravitational-wave astronomy. So, I'm going to show you two videos that
are going to sort of tell you what we discovered. So, the first video is the two black holes. So, what you're looking at on the screen here
are two black holes, each of them are about thirty solar mass, have about thirty times
the mass of the sun, all right? And you're looking, the black holes are the
black things in the middle, and you're looking at the stars behind them. By the way, this is not a Hollywood production
that I'm going to show you. It is actually a real computer simulation,
solving Einstein's equations for these merging black holes. So this is really what it would look like
if you were in a spaceship close up. And I will also point out that the movie I'm
showing you is vastly slowed down, relative to what happened here. So, let me start it. All right, you can see that, as the black
holes spin around each other, all right, the stars behind them are warped and that's because
the strong gravitational fields bend the light that comes around. But what I want you to pay attention to in
this video is the fact that, as they orbit, the black holes are getting closer and closer
to one another. The orbit is speeding up, and eventually they're
going to merge. The event horizons are going to join, boom. They produce one big black hole, which relaxes
and you see a little bit of vibration there and it becomes two smaller black holes die. One bigger black hole is born. Now, what's really amazing about this is this
is the first time that this kind of a system has ever been seen, a binary black hole merger,
and it's proof that binary black holes exist in the universe. So, I want to put this in perspective for
you, because I think it's very important, all right, to give a sense of what really
happened here. So, each of these black holes are about 150
kilometers in diameter, a little bit bigger than that. Take something that's 150 kilometers in diameter,
so that's about, a little bit bigger, maybe a lot bigger than the metropolitan Washington
DC area, pack thirty times the mass of the sun in that, accelerate it to about half the
speed of light. Now, take another thing, thirty times the
mass of the sun, accelerate it half the speed of light and collide them together. That's what we saw here. It's mind-boggling. All right, now, let me talk about the gravitational
waves. You didn't see any gravitational waves there. What you saw was actually the black holes. Now, let me look at this from the, the gravitational-wave
perspective. So, you're going to see, again, a computer
simulation. This is a real simulation, using Einstein's
equations. You see the two black holes, and the green
that you see are the gravitational waves that are produced as the black holes orbit around
one another, their orbit decays, and they merge together. So, they're spinning around. You see the, they're getting closer and closer
together. As they get closer and closer together, more
gravitational waves, they merge, and there's this burst of gravitational waves that travels
for 1.3 billion years. It passes through everything. It goes right through matter, right though
stars, and it eventually gets to the earth, all right? And when it gets to the earth, the gravitational
wave passes and what it's going to do is stretch and compress space as these waves pass. And you'll see that the earth is jiggling
like Jell-O. I want, I don't, I don't want people to be scared here. The earth doesn't really do this. This effect is greatly, greatly exaggerated,
but it gives you the effect. And then we zoom in and how we detect these
are using the interferometer that's in LIGO. And Rai Weiss is going to tell you more about
the interferometer. I just want to say one thing, that the effect
that we're trying to measure from these violent, you know, these big black holes colliding
each other at half the speed of light, all right, is so tiny that it takes something
like LIGO to measure it. We are try, we are trying to measure things,
basically, at 1/1000ths the diameter of a proton. That's the size of the signal that you see
on earth from those events that take place 1.3 billion years away, all right. Let me put that in perspective, because I
think those kinds of numbers, you know, are hard to get your head around. All right, if we were trying to measure the
distance between the sun and the nearest star, which is about three and a quarter light years
away, LIGO would, is capable of measuring that, if it could do that, to a level of about
the width of a human hair. So, the width of a human hair over three and
a quarter light years. That's remarkable precision, right. Now, what LIGO does is it actually takes these
vibrations in space time, these ripples in space time, and it records them on a photodetector,
and you can actually hear them. So, what LIGO has done, it's the first time
the universe has spoken to us through gravitational waves and this is remarkable. Up until now, we've been deaf to gravitational
waves, but today we are, we're able to hear them. That's just amazing to me. I think this is big, again, because what's
going to come now is we're going to be able to hear more of these things and, no doubt,
we'll hear things that we expected to hear, like binary black holes or perhaps binary
neutron stars colliding, but we will also hear things that we never expected. And, as we open a new window in astronomy,
we may see things that we never, we never saw before. So let me conclude by thanking the National
Science Foundation. For forty years, since the NSF started funding
Caltech and MIT to do pilot experiments for LIGO, and then in 1992, the NSF went ahead
and funded the LIGO project, right, and they took a big risk, all right. This, this was, this was bold. The science was solid, but we didn't know
how many events we would see. The technology was nowhere near developed. This was truly, I think, a scientific moonshot. I really believe that. And, we did it. We landed on the moon. So, I really want to thank Dr. Córdova and
NSF and also U.S. Congress, the taxpayers, who have supported this research, because
it's really, really gotten to the point now where it's going to take off. So, I'm going to conclude my remarks, and
I'm going to introduce my esteemed colleague, Gabriele Gonzalez. Gaby is a professor of Louisiana State University. She's also the spokesperson for the LIGO scientific
collaboration and she's going to tell you more about this event and about the team that
discovered it and about the observatory. So, I turn it over to Gaby. Gabriela Gonzalez, LIGO Scientific Collaboration
Spokesperson, Louisiana State University Thank you. It's an honor to be here, to tell you about
this fantastic discovery. This discovery has taken a long time. This has been a long journey, but it also
has been the work of many people. There's only a few of us here, but there's
been, there are now more than 1,000 people working on this and there have been hundreds
of people developing the technology, doing the analysis, and building these detectors. We are very proud of this work, taking a village,
a worldwide village. That was the LIGO scientific collaboration,
working together with the Virgo collaboration in Europe. And we have been analyzing data from two detectors,
in Hanford, Washington and Livingston, Louisiana. LIGO built two detectors, because we are measuring
these tiny distortions of space time here on earth that you can only believe they're
real if you see them both at the same time on places that are far apart. That's the only way to be sure that these
are not local disturbances and they are coming from astrophysical sources. These detectors are l-shaped. This is the LIGO Livingston detector. They are four kilometers long on each side. That's the Hanford detector. And we have lasers that go back and forth
between mirrors to measure the distance between those mirrors. And gravitational waves would distort the
space time and would be measured as distortions in that distance of four kilometers. Again, it takes a lot of people to do this
and you can see a lot of people, young and, young people doing this, as well as people
who have been working on this for decades. So, this is it. This is what we saw. September 14, last year, we saw this signal
in Livingston, Louisiana. That is a measure, that's a waveform that
we saw. The units are strain, that's distortion of
space time, and you can see a peak value, the largest value of this wave form was a
part in ten to the twenty one. For four kilometers, that's a tiny, tiny fraction
of a proton diameter. That's incredibly tiny. But this signal is seen, you can see it even
by eye above the ever-present, rumbling noise that we have in the detector. But we know it's real, because seven milliseconds
later, we saw the same thing in the Hanford detector. This is it. That's how we know we have gravitational waves. But we know a lot more than that. You can see that these signals have oscillations
that grow in frequency and amplitude and then settle down, and that's exactly the prediction
that we know from solving Einstein's equations on computers for the coalescence of two black
holes settling into, merging into a larger black hole and settling down. And the coincidence is remarkable. You can see here, overlaid, the template that
we used or the numerical relativity simulation that was done for these, for the coalescence
of these black holes. That's how we know, not only that we detected
gravitational waves, but these waves were produced by the coalescence of black holes. So, these are the fantastic news we are telling
you about. Now, from these wave form, you can tell a
lot more. You can tell, from the frequency, the masses
of the initial black holes, they had twenty-nine and thirty-six solar masses. From the fitting to the numerical relativity
wave form, we can tell that when they merged, they formed a larger black hole, but not with
a sum of the two masses, with only sixty-two solar masses. And that's because there were three solar
masses emitted in energy, in gravitational waves. That's a huge amount of energy. And we can tell all of that from this tiny
fraction of a second in the wave form. We can even tell more than that. From the amplitude of the wave form, you can
tell how far away this system was. It was more than a billion light years away. This merger happened 1.3 billion years ago
when multi-cellular life here on earth was just beginning to spread. And the signal took a billion years to come
to earth and produce this tiny distortion in our detectors that we are very proud to
measure. Now, you can read a lot more details about
these things in a paper that has just appeared online, peer-reviewed, in Physical Review
Letters. We are also publishing a lot more details
in other papers that will be made public. Now, we can also put these wave forms, we
can make a color plot time frequency diagram and you can see the color, denoting the amplitude,
so it gets brighter as time goes on and then dimmer when the black hole rings down. You can also that the frequency is increasing
and the frequencies of these wave forms are in the human hearing range. We can hear gravitational waves. We can hear the universe. That's what, that's one of the beautiful things
about this. We are not only going to be seeing the universe,
we are going to be listening to it. Now, I wanted to play the gravitational wave
for you to hear, but it's so short that it's just a thump. So, what we have done is taken the real signal
and shifted a bit in frequency, but it's still the real signal. Did you hear the chirp? There's the rumbling noise and then there's
the chirp. Let me do that again. That's the chirp we've been looking for. This is the signal we have measured. We can even tell more. Because we have two detectors, it's like having
two ears. We can localize the signal, not very well,
with two, with only two ears. But we can tell it came from the southern
sky in the rough direction of the Magellanic Cloud and we could have a broad area, a broad
uncertainty area for the region. Of course, it points, the source is a very
point light source. I mean, the merger happened in a small region,
but we cannot tell exactly where it happened, because we only had two detectors. But this will get better. We, we will have a network of gravitational
wave detectors. GEO600 has been working for decades as a technology
demonstrator, but Virgo is going to come with a sensitivity closer to the LIGO detectors
later this year. So we will have three ears to localize a signals. And later on, we hope to include in the network
the KAGRA detector in Japan and hopefully one in LIGO-India very soon. So this is just the beginning. We discovered gravitational waves, gravitational
waves from the merger of black holes. It's been a very long road. But this is just the beginning. This is the first of many to come. Now that we have detectors to, able to detect
these systems, now that we know that binary black holes are out there, we'll begin listening
to the universe. Thank you. We'll, we have, we'll hear now from Rai Weiss,
one of the founders of LIGO, who will tell us about the history and the technology in
these amazing detectors. Rainer Weiss, LIGO Co-Founder, Massachusetts
Institute of Technology All right, well, I'm going to tell you a little
about history and then some about the instrument. And the, I want to first remind you of Einstein's
1915 big discovery, which was celebrated just recently, was the, really the formulation
of these field equations, which were a completely different way to look at gravity. I mean, I, most of us were taught Newton. We talked about forces in gravity. Einstein didn't have that conception. He had the conception that, actually, space
gets distorted, and you can see this in this picture of, of a membrane that is sitting
under the sun, which is that yellow object, and then you can see a little dimple that's
made by the earth. And what, that distortion in space and time
is the thing that also tells those objects how they're supposed to move. So, it's a completely different and a radical
different idea about how gravity, how gravity operates. And then, in 1916, he applied these field
equations to the idea of gravitational waves. There had to be something that communicated
electromag, communicated information. And it couldn't go faster than the velocity
of light. That was already known. And so what he then found is that there were
waves in this theory that moved and propagated the velocity of light and what they were,
were strains in space. They were, and I'll show you a strain in space,
so you can visualize it. Here is this thing that, I don't know, I hope
you can see. It's not the easiest thing. I'm going to make believe the gravitational
wave that you're being demonstrated is coming at you and if, I'll be the agency that moves
the universe here. And you'll notice an interesting thing about
it. They're, if you look at any pair of points
on this thing. What is a strain? A strain is the difference in distance that
two points have as a function of time divided by their initial separation. And you'll notice that in the middle of this
thing, it's small, that strain. The strain is the same all over this, but
the amount of motion is small in the middle. And it's quite large at the edges. And that's one of the reasons, now you have
some image why we built, had to build LIGO to be so big. You had to overcome a lot of other things
that were going on. So, we wanted to make sure that we made it
long enough so you could see this. Now, even with this wonderful, enormous source
that you've just heard about, the, and you know the numbers, the, Einstein, first of
all, could never have conceived of that. But even, let's just look at it. What it is is that, in the early days of,
let's say, 1916, Einstein probably looked very hard at doing things himself, he was
a practical physicist. He was a patent clerk. And what he probably did is he saw that these
waves were generated by accelerating mass, and he probably put on the backs of envelopes,
and we're looking for those envelopes. People don't have them, but they had to exist. Some calculations, could you move a mass that's
big enough, could you measure it with the existing devices that existed in 1916, and
you couldn't. Einstein was very despondent about that. He also then looked at, probably he looked
at, astronomical systems like binary stars and the ones he knew about in those days had
long periods and they just would never change aspect. Nothing would change about them, as they were
radiating gravitational waves. It was just too small. And so what's happened since then, is the,
two things have happened. One is that astronomers have found compact
objects like black holes and neutron stars, which changed the whole aspect of how fast
things can accelerate, and then the other thing that really has changed is the technology. And that is an enormous step in the last hundred
years. And the, so, with that, you're still now having
these things, and I'll describe how we do this in a minute. Let me get you a little perspective. You've already had some, but I want a different
perspective on what ten to the minus twenty one means, okay? Ten to minus twenty one strain, everybody's
saying is a thousandth the size of a nucleus. So, let's get to a little visceral feeling
about that. I mean, the strain is ten to minus twenty-one,
if you now multiple that by four kilometers, you wind up with ten to the minus eighteen,
ten to minus eighteen meters, if you, okay. Now, what is that? And most people don't know the ten to the
minuses, so they'd like to have it as, it's a decimal point and seventeen zeros and then
a one, okay? That's, so you have to think of it as a, as
a fraction. And now let's look what that is. Start with a meter and divide it by a million
three times over. The first time you divide it, you get a micron. So, ten to minus six. That's sort of the size of a cell, or maybe
a thousandth of your hair. Well, we've got much more to go. Then, you divide by another million, and now
you figure you're at ten to minus twelve. That's about one hundredth the size of an
atom, and you're still not there. And now you divide again by another million
and you get to this number that we have to measure. And that's the a thousandth the size of a
nucleus. So how do we do it? Well, we do it by timing light. That's how we do it. And I'll show you this in this, here's an
Michelson interferometer, which is the device that does the measurement. And what you'll see in the, see this round
cylinder there, that's the laser. It's a make-believe laser. Then there's, there's a beam splitter, which
is that thing, which a thin, little thing in the middle. Then there are two mirrors, which have those
aspects, one to the left, one to the right. And then a make-believe detector, which is
that rectangular thing, and now let me turn this animation on. And what we do is we fire light from the laser
into the system. Now this is the electric field in the light. The color is the intensity of the light, so
you'll see where the, the color tells you where the light is, but the electric field
is indexed by the different colors of the field. And you'll notice the way this was set up
is that right now there is no light at the photodetector. That's the trap you've set for the gravitational
wave. And now people begin to wiggle in the animation,
the end mirrors, and you'll notice light appears, disappears, at the photodetector. That tiny motion and that fact, that light,
the amount of light that goes to the photodetector is proportional to that strain in the gravitational
wave. That's the method of the detection. Okay, now you're not done yet. You've got a device that measures tiny motions
or tiny distances, differences in time. But you're not done, because you see, those
mirrors are sitting on the earth, and the earth is very noisy. It jiggles everything. And you want to make sure that the thing that
jiggles, the mirrors, is only the gravitational wave. So, we use all sorts of tricks. And I'll show you one trick. Here's one of the tricks. What, what we do is we suspend the mirrors
from a pendulum Here is a sort of demonstration pendulum, and here's the mirror, and my hand
will be the ground motion. And you'll notice if I move it very slowly
or at low frequencies, the pendulum follows me. It follows the ground motion completely. Now let me wiggle it fast, and you'll notice
the pendulum stands still, while I'm wiggling. That's the basis of the idea. Now that's done with a tremendous elegance
and, you know, with cunning in this picture. This is what's actually in the apparatus. You see it on the screen now. And that is now four of these things in series,
okay? And by the way, the principle I just showed
you is very much like the principle in a car. Makes you comfortable in a Cadillac and sort
of bumpy in a truck, you know? Okay. Now, the thing, you're not done yet, because
there are other forces you have to worry about. And they are thermal noises, all sorts of
noise, even quantum noise in this system. And all of that technology, which has been
developed, had it been available to Einstein in 2016, I would have bet that he would've
invented LIGO. I mean, he was smart enough and he knew enough
physics. He wasn't just a theorist, okay? All right, now, I'd like to introduce to you,
Kip Thorne, who is both a theorist and really an experimenter. And he was a visionary in this field, because
he, he thought about this many years, thought about all the sources, thought about what
the theory really meant. And I want to give you a nice example from
Kip's life. He wrote a book, a popular book, that many
of us have read. It's called Black Holes and Time Warps and
in, and it says, undertitle is Einstein's Outrageous Legacy. And in that book, he tries to introduce the
public to all the wild things that go on in the theory and he has a group of people on
a spaceship, commanded by a woman, who are going to visit all different kinds of black
holes. The first place they go to is a stationary
black hole, and that is like the one in our own galaxy. Then they go to a spinning black hole, and
they look at that for a while. But then, very carefully, they approach a
pair of black holes weighing twenty-four solar masses that are going around each other and
they merge into a single black hole, and then the universe gives a little burp when that
is over. That's all in that book, written, well, a
chapter of that book was written in 1983, okay? And we actually have seen it. So, Kip. Kip Thorne, LIGO Co-Founder, Caltech
Don't forget your toys, right? Rai is a modest man, but you should know that
he was the primary inventor of the interferometers that detected these gravitational waves and
major additional contributions, in terms of ideas, came from Ronald Drever, who is the
third founder of LIGO, along with Rai and me. Unfortunately, Ron is too ill to be able to
be with us today, but his family and he send their greetings. LIGO has been a half-century quest. It arose in part in the 1960s from pioneering
work by Joseph Weber at the University of Maryland, and it arose from interferometer
R&D in the 1970s and '80s at Caltech, MIT, in Scotland, and in Germany. In the late 19-, in the 1990s, we, Caltech
and MIT built the facilities for LIGO with funding from the National Science Foundation. And then, in the late 1990s, LIGO was expanded
to include scientists from many universities around the world and many nations, as Gabriele
Gonzalez described to you. In the 2000s, the initial interferometers
were built and operated in LIGO as precursors to the advanced interferometers that we are
telling you about today. The advanced interferometers were installed
in, between 2010 and 2015. They carried out their first gravitational
wave search, beginning last Autumn, with spectacular results almost immediately. Now, until now, we have only seen warped space
time. We, as scientists, have only seen warped space
time, what is very calm, as though we had only seen the surface of the ocean on a very
calm day when it's quite glassy. We had never seen the ocean in a storm, broiled
in a storm, with crashing waves. All of that changed on September 14. The colliding black holes that produced these
gravitational waves created a violent storm in the fabric of space and time, a storm in
which time speeded up, then slowed down, speeded up again, a storm in which the shape of space
was bent in this way and that way. We have been able to deduce the full details
of the storm by comparing the gravitational wave forms that LIGO saw with the wave forms
that are predicted by super computer simulations. And so, here I'm going to show you a video
that describes the very bottom, it's not very bright, but at the very bottom is the gravitational
wave form that was seen, cleaned of all of its noise, and it agrees beautifully with
the gravitational wave form predicted by the simulations and by seeing which simulation
agrees in gravitational wave form, we can then go in and look at the computer simulation
and deduce what I show you for the storm in the middle of the screen. And time is shown in the upper left of the
screen, the flow of time. Now, the shape of space I show to you by imagining
that we are living in a higher dimensional universe looking in on our universe, I take
away one of the three dimensions from our universe, so it looks like a surface, a two-dimensional
surface, and the flow of time, oh, and then I should say that the funnels that you see
in there represent the warping of space around a black hole. The flow of time is represented by the colors. In the green region, near the center, time
is flowing at its normal rate. In the yellow regions, it's slowed by twenty
to thirty percent. And in the red regions, it's tremendously
slowed. The silver arrows describe the motion of space. It's dragged into motion by the spins and
the gravity and the movement, the overall movement of the black holes, and then the
motion of space causes the orbit to recess, as you saw. I'm pausing the movie now to watch the onset
of the collision. You're going to see in slow motion, the growth,
the warping. I'm going to pause it, stop it here for a
moment. And you can see the extreme warping and then
we see it oscillate and settle down finally into a single black hole, a new black hole
has been born. Far away, in purple and blue, we see the gravitational
waves propagating toward earth carrying the news of the collision. Now, the storm was brief, twenty milliseconds,
very brief, but very powerful. The total power output in the gravitational
waves, during the brief collision, was fifty times greater than all of the power put out
by all of the stars in the universe put together. It's unbelievable. Fifty times the power of all the stars in
the universe put together. Because it was so brief, the total energy
was not that big. It was only what you would get by taking three
suns, annihilating them, and putting them into gravitational waves. Well, that's, that's kind of a lot. And so, colliding black holes are not the
only source of gravitational waves that LIGO will see. We will see gravitational waves from spinning
neutron stars, stars the size of Washington DC, made of pure nuclear matter, weighing
more than the sun, with little mountains on their surfaces that, as the stars spin, those
mountains generate continuous gravitational waves, long-lasting gravitational waves. We'll see gravitational waves from black holes
tearing neutron stars apart, gravitational waves from neutron stars colliding. We are searching for gravitational waves from
the central core engines of supernova explosions and amazingly, we're searching for gravitational
waves, and have some hope of finding them, from cosmic strings, giant strings that reach
across the universe. They're thought to have been created by the
inflationary expansion of the fundamental strings that are the building blocks of all
matter, that expansion, inflation at the beginning of the universe. Now, LIGO has opened a new window onto the
universe, a gravitational-wave window. But all of our previous windows, through which
astronomers have looked, are electromagnetic. The astronomers look, for example, with optical
telescopes through the optical window, radio telescopes through the radio window, x-ray
telescopes on-board satellites through the x-ray window, and each time a new window has
been opened up, there have been big surprises. The universe seen through optical telescopes
was very serene. As seen through radio telescopes and x-ray
telescopes, it's tremendously violent. Gravitational waves are so radically different
from electromagnetic waves that I think we can be rather sure that we will see big surprises,
perhaps even bigger surprises, through the gravitational-wave windows than we have seen
through the new radio and optical, radio and x-ray windows. LIGO is just the beginning with gravitational-wave
astronomy. Over the next decade or two, we will have
four gravitational-wave windows opened onto the universe. There's LIGO, looking at gravitational waves
with oscillation periods of milliseconds. There will be a window with gravitational
waves that oscillate with periods of minutes to hours. There will be a window with gravitational
waves that oscillate with periods of years to decades. And a window with billion-year long oscillations. It is really remarkable that LIGO is such
a fantastic beginning. Now, I'd like to turn this back to Dr. France
Córdova, the director of NSF, but I'd like to do so in thanking Dr. Córdova and her
predecessors for a fabulous forty-year partnership with, between NSF and the LIGO collaboration. We began with a high-risk dream, with very
potential, very high potential payoff and we are here today with a great triumph, a
whole new way to observe the universe. Dr. Córdova. Dr. France Córdova
Wow. Einstein would be beaming, wouldn't he? This is obviously a very, very special moment. It's a very special moment for me, personally,
to be able to hug a faculty mentor when I was a graduate student at Caltech, and hearing
Kip and Virginia Tremble, the spouse of Joseph Weber, inspire us students with stories of
black holes, which seemed imaginary at the time. And, look, look where we've come now. It's just amazing. So, today you and the hundreds of collaborators
who have made this discovery possible mark this day as truly historic. I commend each of you, as well as all the
NSF program directors, who have stood by you steadfastly for about forty years. Let's give a big hand to our NSF program directors. Fabulous. You had the vision and the drive. You had the persistence, the commitment to
expand what we'll learn about our universe over the coming years and decades. As a graduate student at Caltech in the 70s
and now as NSF director, I'm struck by how this represents more than just a new generation
of observation. It's seeing our universe with new eyes, in
an entirely new way. I invited Dr. Virginia Tremble to join us
today. Virginia's both an astrophysicist and an historian
of astronomy. Her late spouse, Dr. Joseph Weber, did pioneering
work in the '60s that Kip Thorne already highlighted. And it's really very special that at NSF's
LIGO facility in Hanford, Washington, his early instrument is on display. Discoveries of this magnitude do not happen
overnight. They aren't made by one person, working along
in a lab. They arise from the boldness and brilliance
of scientists like Rai Weiss, Kip Thorne, Ron Drever, and Joe Weber at the start. And now, Gabriele Gonzalez, Dave Reitze, the
entire international LIGO collaboration, and so many others whose contributions have led
to this moment. And just as one scientist does not do it alone,
many times neither can one funding agency or one country. Bruce Allen, the managing director at the
Max Planck Institute for Gravitational Physics is here with us today. Likewise, John Womersley, the director of
the UK Science and Technology Facilities Council is here, as is Anthony Murfett from the Australian
Research Council. Gentlemen, please stand and be recognized. Thank you so much. I single out these three, because the UK, Germany,
and Australia have all made direct contributions to the advanced LIGO instrumentation and to
the LIGO scientific collaboration. I encourage reporters to talk with them and
hear their stories, because their role in this international endeavor is significant
and we most definitely could not be here today without their support. Thank you. That said, this is a press conference, and
we have reporters her and also in an overflow room and listening in via a webcast. Those who aren't in this room will provide
questions to NSF staff who will ask them here in this room. And please, as you ask your questions, give
us your name and affiliation and wait for the microphone. And now, let me open this up to your questions,
and I'll moderate them and try to determine who goes first, but thank you very much for
being with us today. And I saw-- Here and then over here, please. Davide Castelvecchi
Hello, Davide Castelvecchi from Nature magazine. So, if I understand correctly, this event
was spotted even before the actual science run began. Now, is there, is there a sense of an, what
did you think when you first saw it and, you know, when you communicate it to the public,
to the world, is there a sense that maybe this is too good to be true? David Reitze
I'll start it. I'm sure that everybody here has a comment
about that. So, to your first point, it started before
the science run officially began. That's actually true. However, we were in an engineering test of
our instruments where we were running them as if it were in a science run, and so we
were operating them just the same way. We were checking the data the same way. So, we were quite confident when this event
came in and was vetted that it was a good event. Were we surprised that it was too good to
be true? Absolutely. My reaction was wow. I could, I couldn't believe it. Gabriela Gonzalez
Yes, I should say that there has been a lot of talk about whether this could have been
an injection, or a blind injection, and I want to say it's absolutely not an injection. We did check very, very carefully all of our
injection systems, because in the beginning, we thought, perhaps one of our tests produced
this. But we know we didn't, because we have very
careful monitoring systems and we checked all of that. So, it was amazing. This was a gift of nature. It was not just black holes, but it was a
signal that we could see by eye. We, many signals in the future will probably
not be this loud. But, it was true. It is true. Rainer Weiss
I'd like to add something to that, if I may. You're getting a good answer, but I'll give
you a slightly instrumental answer. And that is, I mean, look, I think it was
already said that we saw this at both detectors, both in Louisiana and in Washington state. Now, you have to also know a little about
what are at those detectors. We have a bevy of instruments that measure
environmental, environmental noise, the seismic noise, the possibility that there's micro,
that there's a sound. The fact that there could be tilts of the
ground, the fact there could be RF interference, everything you can think of and hope, well,
maybe there's some we haven't thought of, but everything we could think of has an instrument
that measures it. And what one does is you use those signals
and you see if they are in any way coincident with the gravitational-wave signal that you
suspect. On top of that, there's one further thing. We have, and this is quite elaborate, we have
something like a hundred thousand signals that come out of the instrument, different
things, different [] systems. Everywhere in the system we are monitoring
the interferometer itself and so, consequently, we also look at those channels to see if there's
something that is not in the outward channel, the proper channel. There are many other channels that could look
like the gravitational wave you're seeing in what's called the proper channel, and we
didn't see anything. So, that's, that process that I just described
to you is what all of us went through in a long, it took a long time to get this out
and that's part of the reason. Kip Thorne
Let me add just one thing. The, this signal is just barely not strong
enough that it could have been seen in the initial interferometers. And so, after thinking about it, when I first
saw it, I was very startled, but then I just realized that if it was just below the level
of where you could see it from the initial interferometers, and then you turn on with
sensitivity that is three times better than that, well, that's what this signal is. It's three times above the level of where
you would have just barely missed it in the initial interferometer. It's because of the big jump in sensitivity
from going from the initial interferometers to the advanced interferometers. It's not all that startling in hindsight. It was tremendously startling at the time. Rainer Weiss
In fact, Kip, it's ten times better in the region where that signal begins is, yeah,
but, yeah, yeah. Dr. France Córdova
And NSF was very pleased and relieved on behalf of all our taxpayers. Great, so we have a question here. Seth Borenstein
Seth Borenstein, the Associated Press, for Kip or any of the other scientists, seeing
that you saw it so early, first, can you tell us what that might mean in terms of prevalence
of gravitational waves, especially at that lower frequency that you can now, that you
can now hear, are, does this lead you to believe that there are far more out there now that
you're listening with more sensitivity? And in terms of, well, I, and I guess the
other part of this is, or is, or was this just sort of dumb luck, you got the one ever
year or decade and it just happened to be about the right time you were turning on? And can you go, explain the importance of
these lower frequencies that you can now hear this in that you couldn't before. Kip Thorne
Well, let me just say that the technical paper that has just been published, as, during this
press conference, does contain a very careful statistical analysis that states what this
means, what this brings us about inform, of information about how often these things may
occur. Meta analysis does say we ought to see some
more over the coming year, and it is very carefully documented as to just what the probabilities
of this are. Maybe others can answer in more detail. Dr. France Córdova
Well, my understanding is that the sensitivity can still be tweaked up a little bit, too. Kip Thorne
That's right. Dr. France Córdova
And that should yield more detections. Kip Thorne
So, that's the additional factor is that LIGO is, advanced LIGO is at one third of its ultimate
design sensitivity, and over the next few years, that, the noise level will be brought
down, LIGO will be three times better. That means you see three times farther into
the universe. That means that the volume in the universe
you can see goes up by a factor of three cubed or twenty seven. And so, after this tweaking of improvement,
the rate will be twenty-seven, or approximately thirty times higher, than it is now and it's
already high enough that we should be seeing more this, in this coming year. So, it's really fantastic. We're, we are going to have a huge richness
of gravitational wave signals in LIGO. Dr. France Córdova
And that's a promise. All right. [unknown]:
Hi, my name is []. I'm a Russian reporter [] here in Washington DC. First of all, gentlemen, and ladies and gentlemen,
congratulations on the wonderful news, on the wonderful discovery. Second of all, coming from Russia, I obviously
have a question about the scientific collaboration with the Russians. I understand that actually the Soviets, in
1962, suggested the use of interferometers, only then they were too expensive to be used. So, if you could touch on that a little bit
and, most importantly, is what lies ahead? What lies ahead? Are you planning, like, one of the physicists
I spoke to said that the next stage should probably bringing these things into space,
without the interference from earth and trying to measure the effects out there. So, what are your plans for the next stage
of the research? Rainer Weiss
Let me, let me try it. Okay, let me try to answer you partly. Look, nobody gave the impression that people
hadn't thought of interferometers before. In fact, I don't remember the authors that
were, in '62-- Kip Thorne
Mikhail Gertsenshtein and Vladislav Pustovoit. Rainer Weiss
Yeah, Gertsenshtein was one of them, right. Kip Thorne
I know, because I spent a lot of time in the Soviet Union in that era and they were friends
of mine. Rainer Weiss
And it turns out that it wasn't, it wasn't just with them, but what was done there was
not to design a system, it was to look at the concept, could one measure the existence
of a gravitational wave by using light or electromagnetic radiation as a way of detecting
them. Then there was actually another effort made
in the United States by people at Hughes who built the little instrument that actually
Michelson interferometer was solidly connected to a table and very much like a readout for
a bar-- Virginia Tremble
It was connected to a gravestone actually. Rainer Weiss: What? Virginia Tremble
It was connected not to a tabletop, but to a large gravestone. Rainer Weiss
A grave stone. Okay, well-- Kip Thorne
This is the historian of astronomy. Dr. France Córdova
Virginia Tremble knows. Rainer Weiss
And that came from an idea that Joe Weber had as a way of possibly doing it besides
the method that he had chosen. So, the concept of this, doing this interferometrically
has been around. It's not the, it didn't start right away with
LIGO. Kip Thorne
Now let me just interrupt you, because I still call Rai the primary inventor and that is
because, in 1972, he, having done an extensive analysis, he published a paper in an obscure,
internal journal of MIT in which he identified all of the major noise sources that the initial
LIGO interferometers would face, and he spelled out how you would deal with each of these
and what the resulting sensitivity would be that you had to have a instrument that was
kilometers long for success, but with an instrument of that sort, you should be able to get to
the required sensitivities. And that, spelling all of that out, in quantitative
detail, is what I would regard as really the primary invention of what we see today. But, indeed, the outline of the idea began
with Gertsenshtein and Pustovoit in a Russian journal in 1962. Rainer Weiss
Yeah, let me talk about, let me talk about the space thing, because on that, we were
much involved in that, too. That is now, you probably have heard of the
project LISA, L-I-S-A, Laser Interferometer Space Antenna. Many people in the world have been involved,
the United States, the Scots, Italians, a lot of people are involved in that and, of
course, the Germans. And what has happened there is actually both
good and bad. What's happened is NASA, in 2011, this was
a very big recommended project by NASA, by, from the Decadal studies, they recommended
that this be the third most important thing that they would do, and because of overruns
and other problems at NASA, all of that was stopped in 2011, okay? Stopped to the point where the, what happens,
the Europeans picked it up alone. They tried to push it. They're still now in the process of that,
and just this December, a very successful thing has happened. They have, called something, they have launched
something called the LISA Pathfinder, which was a technology test. And so far, as far as I know, one of the more
critical things that's happened is that they've been able to release test masses in that system,
which was a big worry that people had. Now, the thing is the compromise that was
made in Europe, and I will say something a little bold here, the compromise that was
made in Europe to make it so that the Americans didn't have to contribute, because they weren't
going to, they've got to do a little bit, turns out, probably, not the best thing to
do for the science. The science and the risk involved in doing
that space mission. So, consequently, many of us are trying to
get a collaboration to be re-established, well, meaningful collaboration between the
United States and Europe on this thing. I hope that happens. Kip Thorne
Let me just, let me just add that the space-based antenna -- David Reitze
There are lots of journalists out here that I'm sure would like to ask questions. So go ahead, but, answer your question. Kip Thorne
Let me just say that that will open up the gravitational-wave window with periods of
minutes to hours, that, the second of the windows I talked about. Dr. France Córdova
Right, right. That's very important, your slide where you
showed that they're going to be looking at different phenomena than what we did with
LIGO. So, that, that's just key here. It spreads out the, like the electromagnetic
spectrum is spread, this spreads out the gravitational-wave spectrum. Yeah. Great. Okay, we have a question here. Ivan Semeniuk
Hello, there, it's Ivan Semeniuk from The Globe and Mail newspaper in Canada. Congratulations. First, very briefly, I just hope one of you
can clarify the duration of the signal the detectors picked up. It looks like 0.2 seconds, but I just want
to be sure. But, more broadly, could you comment and reflect
on the sources, because these are not just any old black holes. They're extremely heavy black holes, and I'm
wondering what you think that says about conditions in the universe at the time that these, that
these things form. What might we be learning here? Gabriela Gonzalez: Yes, I mean this, first,
the 0.2 seconds is a duration that you see of, above the noise, but the analysis that
we do is a lot more sophisticated than that. We don't do an analysis by eye. So, we can tell not, we can tell that this
wave form, of course, generated a long time ago, these black holes were circling each
other for billions of years before merging. So, we only see the last merger, the last
cycles before the merger and the one or two cycles after the merger in there, but the
signal is a lot longer. You asked about the systems. Yes, these are not heaviest black holes, because
we all know about million solar mass black holes in the centers of galaxies, tens of
millions, but these stellar mass black holes, we knew existed because we know that supernovas
exploding and neutron stars colliding form stellar mass black holes and there is evidence
from x-ray observations about stellar mass black holes, but they all had been relatively
lower masses. And this is a higher mass. On the other hand, this was a coalescence
of two black holes, so you don't expect to see electromagnetic counterparts, so you don't,
you didn't expect to see a system like this with x-ray observations. You might. There might be other things in there, but
the fact that these were not seen by x-ray observations didn't mean that these couldn't
exist. Now, we know they exist and we will tell how
many there are, what kinds of masses they are with future observations. So, it's, we have opened a new window. We are not contradicting any theories that
there were before. David Reitze
Yeah, and let me briefly follow up, because it goes back to a point that's very important. This is our initial run. This is a, this is the maiden voyage, if you
will, of advanced LIGO, all right. It, we haven't gotten the detectors to the
sensitivities where we expect them to be operating, and in particular, at lower frequencies. And there's a relationship between the frequency
response of the interferometers and the size or the mass of the signal that we detect. So, it is very possible that when we get our
interferometers more sensitive at lower frequencies, and that's much harder, actually, that's,
it's very, very hard to get these things working right at low frequencies. We have a, we have a, you know, our work cut
out for us. There may be more massive black holes out
there that we haven't seen yet. Hundred solar mass. We could be sensitive to five hundred solar
mass black holes. So there could be a really, a nice discovery
space that opens up once we get out there. Gabriela Gonzalez
And let me add that there are many other scientists from the collaboration here. Vicky Kalogera can answer in a lot more detail
that kind of question. Dr. France Córdova
Well, and Kip Thorne, I think some of you know, is a consultant on the movie Interstellar,
so now, now we will await Interstellar 2, the sequel. David Reitze
You're the executive producer, actually. Dr. France Córdova
All right, we have a question from our webcast or overflow room here? Lisa]
Yes, we have about 90,000 watching via webcast and among those is a journalist, Pete Spotts,
from the Christian Science Monitor. He says, what sorts of interworkings can these
wave forms probe in addition to providing information on the distance and masses of
the progenitors? Kip Thorne
In this case of the binary black holes, the wave forms, as I described with this beautiful
color movie, they tell us, by comparing those with computer simulations, you infer the wild
storm in space time that occurred. And it is the combination of computer simulations
and the observations that are going to get us, in many cases, very, very deep understandings. In this case, when neutron stars collide in
the central engines of supernovae. So, that's a powerful combination. David Reitze
Yeah, it's remarkable that those wave forms that Gaby showed reveal so much information
about the event. Now, the one thing we should say is we can't
speak in certainties here. When we say, 1.3 billion years, it's approximately. It could've been further. It could've been 1.6 billion years. It could've been 900 million light years away. The masses could have been bigger, smaller,
or heavier, and that's just due to the fact that there's uncertainties in the data itself. But these, these wave forms give you an immense
amount of information about what the sources are, about what the progenitors are, about
what the final mass is. Gabriele Gonzalez
And let me just spend thirty seconds saying that the way we learn this information takes
a lot of work. It's not just numerical relativity simulation. Those are too expensive to do in quantity
for search for this signal. It's the analytical wave forms that are matched
to those numerical relativity wave forms that we can produce in numbers and then we can
tell, not just what's the most likely mass, what's the most likely speed, but also what's
the uncertainty in those numbers. And that's why this field takes so many people
to work on, because we need to do everything and we need to do everything right. Dr. France Córdova
Yeah, you brought up a really good point. I think some of other listeners are from our
supercomputer centers that we fund and their contributions have just been seminal in all
of this of doing the computational modeling. So, a big shout out to them. Let's see. Lisa, you have one more question here and
then we'll take yours in the back of the room. Lisa
Okay, it's actually a question that's been echoed, speaking of echoes, echoes throughout
the web, questions about what that means for us here on earth and will this bring us further
in the science of things like time travel and high-speed traveling? David Reitze
Oh, Kip, this is tailor-made for you. This is your question. Gabriela Gonzalez
What's the next movie? Kip Thorne
I think it brings us a much deeper understanding, by the combination of the theory and the observation,
a much deeper understanding of how warped space time behaves when it is extremely warped,
when it is, what we call, in the non-linear regime and highly dynamical and with very
high speeds. I don't think it's going to bring any closer
to being able to do time travel. I wish it would, but that's a different direction,
and LIGO is heading in, LIGO's direction is really understanding the wild dynamics of
highly-warped space time. Dr. France Córdova
All right, question back here? [] Cabrera
[] Cabrera from [] in Italy. Which is the role of Italian scientists and
the antenna Virgo near Pisa, in Italy? Dr. France Córdova
Okay, on Virgo, Gaby. Gabriel Gonzalez
Yes, their role is very, very important, not just in the future, we expect the Virgo detector
to join the network this year and then when we detect the future sources, the next detections,
we will have a much better localization because we have the Virgo detector working with the
LIGO detectors. But it's not only that. LIGO scientists and Virgo scientists have
been working with LIGO data and with Virgo data now for many years. So the analysis that we have done on this
discovery is jointly done by all the members of the LIGO collaboration and the Virgo collaboration,
and that's why we say it took a village. It took a worldwide village to do this. David Reitze
And I'll add that we are anxiously awaiting for Virgo to get online. We have somebody here who's the leader of
the Virgo project, or the Virgo detector project, Giovanni Losurdo, so he can talk a lot more
about that. Dr. France Córdova
Yeah, Giovanni, wave your hand so people can see who you are. Thank you, being with us. So, we have a question here. Adrian Cho
Adrian Cho, Science magazine. So, first of all, congratulations on this
amazing accomplishment. I'm struck by the fact that, you know, for
the first time, you know, humans have detected gravitational radiation. And, you know, this may be a big leap, but,
you know, we've just, you know, found the quanta of the three other forces of nature,
the weak force, the strong force, and the electromagnetic force. These seem like very classical objects, but
it's also incredibly extreme conditions. Is, does LIGO, in this sort of observation,
have any purchase on, you know, moving towards a quantum theory of gravity? David Reitze
Quantum gravity, yeah. I think the answer's no, but I'm going to,
again, there are theorists on this panel. And one of them is right there. Kip Thorne
There is one crucial thing, which is highlighted in the paper that has just been published,
and that is, by looking, very carefully comparing the observed gravitational-wave form with
the results of solving Einstein's equations numerically on a computer to very high precision,
comparing those two wave forms, you can see whether or not the waves got slightly distorted
in their shape as they traveled 1.3 billion light years. They would've been slightly distorted if the
graviton, the particle, fundamental particle that carries the gravitational waves had a
non-zero rest mass. And through these observations, as is described
in this paper, LIGO has placed a stronger limit on the rest mass of the graviton than
we've ever had before. That limit, I think, check me. I think it translates in more normal language,
into ten to the minus fifty-five grams. I think that's the number, but-- Gabriel Gonzalez
We know it in kilometers. David Reitze
I know it in, I know it in kilometers also. Ten to the sixteen kilometers. Kip Thorne
Pardon? Dave Reitze
Ten to the sixteen. Rainer Weiss
Can I answer you in a different way? I mean, turn your question a little bit. And that is, I think there's a miracle of
sorts here already. Certainly, for me there is. I mean, here these equations were written
in 1915, okay? And they'd been tested in the wheat fields,
I mean, you know, many of the rel, the tests in general relativity have been done in the
field of the earth, the field of the sun, the solar system, and now also in the binary
pulsar, which was the Hulse-Taylor object, and these were all the strongest fields that
we would have a tiny, compared to what we're looking at now. The field has a unity strength, if you want
to really say what it is, in this black hole system. And nevertheless, the field equations seem
to work, which is sort of amazing, to me. This tremendous range, a dynamic range of
the thing, is just amazing. Dr. France Córdova
All right, who has a microphone? Let's get a microphone to some of our, okay,
and then the fellow back here had, next. Okay, yes. []:
My name is [] from the Japanese newspaper, the [] Shimbun, and also in Japan, gravitational
waves detector called KAGRA will start observation soon, so could you tell me a little bit what
is your expectation of the Japanese gravitational detector? David Reitze
Right, so as-- Dr. France Córdova
Can you repeat? So it's the Kamioka gravitation-- David Reitze
Yeah, so the question, the question came from a, I'm sorry, I didn't get your name, but
a reporter who covers, in Japan talking about, asking about tell, say a little bit about
the role of Japan and the role of KAGRA, which is the Japanese gravitational-wave detector
under development right now and under construction right now. So, I'll start with just the basics. KAGRA is much like LIGO, much like Virgo. It's a three-kilometer interferometer, not
a four-kilometer interferometer. It's underground. It's in the Kamioka mines, which has a lot
of advantages, actually. We don't, they don't suffer from the same
kind of environmental perturbations that we do. It's expected to come online probably 2019,
maybe 2018. They still have some work to do. It's, it's got some really advanced technology. It's even more advanced than LIGO. They use cryogenics to cool the mirrors to
make them more quiet. They don't vibrate as much. All right, that's really pioneering technology. Like Virgo, like the two LIGO detectors, all
right, KAGRA adds something to this ability for us to be able to localize events. All right, so, when you have one detector,
interfer, this is, this is the best way to say this. Interferometers are like microphones, all
right? They're sort of omni-directional, all right. An interferometer cannot tell you where the
event came from in the sky. Two interferometers gives you a little bit
of localization. You saw that in Gaby's presentation. Three interferometers gives you more localization. It's like triangulating. But it turns out even three interferometers
doesn't cover the whole sky. It depends on the orientation of the interferometers,
in the plane, all right, you can't really see things. So, KAGRA, this, this fourth interferometer
that's going to come up in 2018 or 2019 will greatly enhance our capability to localize
things. So that banana that Gaby showed you that had,
I don't know, six or seven hundred degrees in it, all right, that can shrink down to
ten square degrees, five square degrees, making it much easier for telescopes to be able to
go and see the events that LIGO, KAGRA, and Virgo are seeing. Dr. France Córdova
All right, we're going to continue questions, but we do have to say goodbye to our listeners
on webcast now. Thank you very much for having joined this
most important moment. Geoff Brumfiel
Geoff Brumfiel with National Public Radio. So, my question is given you saw this thing
even before you started your scientific run, have you see other, [Audio cuts out]
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