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LIGO detects gravitational waves — announcement at press conference (part 1)


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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