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(contemplative orchestral music)

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You had to admire people that would devote years,

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and years, and years to trying to do it

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with the likelihood being that they would fail.

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More than two decades ago,

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two teams decided to try what seemed impossible,

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to prove the existence of black holes.

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Both of these kind of converged at almost the same time,

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but coming about it in very different ways.

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We're crazy optimists in this business.

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You have to be.

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If you look at all the things that could go wrong,

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then why would you dedicate your career to it?

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One team called LIGO

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plan to use giant instruments

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called laser interferometers

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to detect tiny ripples in space-time

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called gravitational waves

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caused by the merger of two black holes.

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Albert Einstein thought that it will be impossible

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to ever detect them.

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We're looking for motions

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that are about 1,000th of the size

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of a proton inside the nucleus of an atom.

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The other team

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called the Event Horizon Telescope

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would try to capture an actual image of a black hole,

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a task comparable to seeing a tennis ball on the moon.

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And so you need a telescope the size of the entire earth.

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But obviously,

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we couldn't build a telescope the size of the the earth.

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But in radio astronomy,

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you can play this near magical trick

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where you take two telescopes separated by some distance,

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bring the data that they receive together

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to form a telescope

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as though you had one as large as the distance

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between these telescopes.

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Finding black holes,

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either by taking an image of one

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or by detecting them with gravitational waves

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would be among the most difficult challenges

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in the history of science.

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I was sort of trembling in front of the challenge.

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It was hopeless

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because the technology would never be there.

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We staged experiments that went nowhere.

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We tried and we failed.

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And if they found what they were looking for,

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could they keep it secret until they were sure?

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Many people had a eureka moment.

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I was completely blown away

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by how clear cut this signal was.

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And I had a moment of panic.

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We all kept the results secret.

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Because I knew if that was right,

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we would be writing history.

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All I could do is figure out how we had gone wrong,

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how are we fooling ourselves?

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At some point,

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you have to stop and just listen to the universe.

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(contemplative orchestral music)

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Black holes were born of theory.

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They might really exist,

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but there was no direct proof.

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Many felt that the idea itself must be fatally flawed.

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An extremely massive object

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will curve the space-time around it so much

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that anything that passes by

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will actually fall into that object

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and will not be able to escape.

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Even light wouldn't be able to escape,

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and that's basically a black hole.

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But is this real?

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Clearly, something like this would not occur in nature.

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No one felt that nature would be that crazy.

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These cosmic objects are more extraordinary

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than we could ever have dreamt up.

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At the center of a black hole,

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the laws of physics as we know today,

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they break down.

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There's no matter there.

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The structure that we see is a vacuum structure.

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It's like a tornado in space-time.

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In their purest form,

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the concept of black holes starts with Albert Einstein.

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For physicists,

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the great year for Einstein was 1905

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when he solved several of the biggest problems in physics

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within a matter of months.

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And then he spent 10 years developing his theory of gravity,

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which is general relativity.

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What we see coming out of general relativity

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is that matter and energy has the ability

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to affect the space time around it.

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Space time is a mathematical concept

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that unites time with three dimensions of physical space

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so that they are intimately woven together

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into what is called the fabric of space time.

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The actual presence of matter distorts this fabric.

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If you send a light beam past a, say, a star or a planet,

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the reason it bends is

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because it's trying to follow the straightest path possible

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in a geometry that is now curved.

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And thus, that is what gravity is.

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It's basically the geometry of space time.

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Within weeks of Einstein

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publishing his revolutionary theory of gravity,

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people began trying to figure out what it all meant.

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One of the first

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was a German physicist called Karl Schwarzschild.

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Despite being in his forties,

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Karl decided to volunteer to fight in the First World War

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and he worked as an artillery man.

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He was able to predict how space

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and time would look like around a point mass.

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And he realizes if you compact matter

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into a small enough volume,

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that there is this event horizon

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at what we can now call the Schwarzschild radius

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where the speed of escape is larger than the speed of light,

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where even light cannot make it out.

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A one way boundary

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where information and light can only go in,

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but never can come out again.

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That's the moment when black holes really were born.

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Of course, completely crazy idea.

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This wouldn't exist.

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Neither man realized that it was anything more

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than a mathematical construct

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that they didn't really have to worry about

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because no one felt that nature would allow it to happen.

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Poor Karl Schwarzschild,

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he died very quickly after finding the solutions

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due to an illness that he got in the trenches there.

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Throughout the 20th century,

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the theoretical study of black holes became vibrant

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and popular among scientists.

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They had theories for how they might form.

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And astronomers had even started to speculate

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about where they might lurk in the cosmos.

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So there are two varieties of black holes,

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the stellar variety,

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which are born during the death of stars.

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And they weigh a few or 10 times what our sun does.

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Stellar mass black holes

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are thought to have a Schwarzschild radius

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of around the size of a small modern city.

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Even though they have a mass of 10 or 20 suns,

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they are tiny in comparison to the stars

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from which they were born.

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Super massive black holes, however,

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would contain the combined mass of millions

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or even billions of suns.

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They could have a Schwarzschild radius

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the size of an entire solar system.

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Astronomers wondered if stellar black holes

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were hiding in all galaxies

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and that super massive black holes

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might be found at the heart of many.

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They even named the super massive black hole

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that they suspected might lie at the heart of our galaxy

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Sagittarius A star.

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Are they out there?

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The theory predicted it, but are they really real?

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To try and answer that question,

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the team called LIGO

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would try to find the smaller black holes

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with gravitational waves,

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while the Event Horizon team

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would hunt the super massive black holes

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using a type of astronomy that uses radio waves.

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If you have optical light,

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the wavelengths are tiny, tiny, tiny.

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But if you study radio emission,

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the wavelengths are actually big.

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And so you have a gigantic dish

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that can reflect radio waves.

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It was intense radio emissions

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coming from the center of galaxies

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that first made astronomers suspect

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that super massive black holes must be the culprit.

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So we had to think a little bit

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about these emission mechanisms,

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like what would cause is glow in radio waves?

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And so what can power something like that

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is gravitational accretion onto a super massive black hole.

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That's the only way we know of to power something like this.

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In the 20th century,

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the idea of capturing an image of a black hole

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with these radio emissions

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was far beyond the realms of possibility,

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but some people did dare to dream.

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Many times in science,

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you wind up in a situation

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where somebody makes an initial discovery

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and it goes under appreciated.

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And this is the case with Jean-Pierre Luminet.

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I mean, this was a real visionary.

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In 1979, he came with the first full simulation

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of what a black hole would look like if you were there,

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like if you could really see in infinite detail.

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To capture an image of a real black hole

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in the way that John-Pierre Luminet imagined

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would require a radio telescope

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with a dish as big as the planet earth

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and technologies that simply didn't exist yet.

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However, for the gravitational wave team,

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they had an even more fundamental problem to solve.

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Nobody even knew if gravitational waves were real at all.

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The theory behind them originated with Albert Einstein

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from around the same time

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that Karl Schwarzschild was formulating his ideas

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of black holes.

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In 1916,

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Einstein wrote a little paper, five pages long maybe.

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He looked at the equations of general relativity

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that he had developed,

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and he noticed it had a great similarity

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if you put it in a certain way

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to the equations of electricity and magnetism.

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And since electricity and magnetism have waves,

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he conjectured that gravity must also have waves.

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By the 1930s,

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Einstein had written a further two papers

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on the subject of gravitational waves.

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According to Einstein,

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this phenomenon of gravitational waves

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is very interesting from a theoretical point of view,

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but any real effect on earth will be so small

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that it will be very likely

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always impossible to ever detect them.

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They were never fully accepted

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during this whole period and beyond,

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even until his death.

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The great Albert Einstein died in 1955.

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Black holes and gravitational waves,

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ideas that were rooted in his theories,

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were far from being considered a reality.

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But in 1958,

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50 of the world's greatest experts

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in general relativity had a meeting.

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So at this now renowned conference,

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the question of whether gravitational waves really do exist

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and produce something that could be measured was raised.

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Richard Feynman was there.

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He said, if gravitational waves really exist,

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they have to be able to do something.

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They can't just exist.

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They have to be able to transfer energy.

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And so he made a,

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what we call like a (indistinct) experiment,

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just a thought experiment.

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And that was if you have a bar

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and you put a couple of rings on it,

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and then a gravitational wave goes through the bar,

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it'll take the bar,

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and it'll expand it, and contract it,

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and expand it, and contract it

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at the frequency of the gravitational wave.

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As it expands, it, of course, pushes on the rings

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and they would move.

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But what's happening

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is that they're transferring energy friction to the ring.

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This clever thought experiment

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inspired one of the people at the meeting

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to actually build such a device.

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His name was Joseph Weber

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and the machines he created are called Weber bars,

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the first ever gravitational wave detectors.

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It's accepted today that his bar detectors

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were not sensitive enough to be able to make any detections,

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but he played a very important role

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in sparking the rest of the world's interest

275
00:12:22,270 --> 00:12:26,350
into what a different type of detector might look like

276
00:12:27,310 --> 00:12:29,310
that could ultimately be more sensitive.

277
00:12:30,600 --> 00:12:33,500
So gravitational waves, if they exist,

278
00:12:33,500 --> 00:12:35,560
how do they manifest themselves?

279
00:12:37,474 --> 00:12:39,560
If I take just a place

280
00:12:39,560 --> 00:12:41,430
and a gravitational wave comes through,

281
00:12:41,430 --> 00:12:44,610
it distorts the space and time

282
00:12:44,610 --> 00:12:47,510
such that it stretches it in one direction

283
00:12:47,510 --> 00:12:49,430
and squashes it in the other direction.

284
00:12:49,430 --> 00:12:51,360
The easiest way to think about it

285
00:12:51,360 --> 00:12:54,180
is what happens when you go to the amusement park

286
00:12:54,180 --> 00:12:55,630
and you see these mirrors.

287
00:12:55,630 --> 00:12:57,850
You look in one and you get tall and thin.

288
00:12:57,850 --> 00:13:00,460
You go to the next one, you get short and fat.

289
00:13:00,460 --> 00:13:03,610
If you imagine that you're now a detector,

290
00:13:03,610 --> 00:13:06,120
it's basically going back and forth

291
00:13:06,120 --> 00:13:07,250
between those two mirrors.

292
00:13:07,250 --> 00:13:09,360
You're getting taller and shorter

293
00:13:09,360 --> 00:13:12,040
and fatter at the frequency of the gravitational waves.

294
00:13:12,040 --> 00:13:15,680
So maybe the gravitational wave is 60 Hertz,

295
00:13:15,680 --> 00:13:18,080
so 60 times a second, you're going (vocalizing).

296
00:13:19,260 --> 00:13:20,890
And that's what we have to measure.

297
00:13:20,890 --> 00:13:22,803
So how are we gonna measure that?

298
00:13:23,950 --> 00:13:26,130
So we had to find out a way

299
00:13:26,130 --> 00:13:28,420
to be able to detect here on earth

300
00:13:28,420 --> 00:13:30,800
some very, very small perturbations.

301
00:13:30,800 --> 00:13:33,760
And it turned out that the most sensitive instrument

302
00:13:33,760 --> 00:13:36,100
that we could make and design

303
00:13:36,100 --> 00:13:38,203
is what is called a laser interferometer.

304
00:13:39,500 --> 00:13:41,490
So what does an interferometer do?

305
00:13:41,490 --> 00:13:43,160
I take a beam of light

306
00:13:43,160 --> 00:13:46,370
and I get to a place where there's a mirror

307
00:13:46,370 --> 00:13:49,140
that sends half the light in one direction

308
00:13:49,140 --> 00:13:51,580
and half the light in the perpendicular direction.

309
00:13:51,580 --> 00:13:54,680
If somewhere down the way, I put a mirror,

310
00:13:54,680 --> 00:13:56,180
it'll bounce back.

311
00:13:56,180 --> 00:13:59,340
And if I've calibrated it so that they're the same length,

312
00:13:59,340 --> 00:14:01,920
they'll come back at exactly the same time.

313
00:14:01,920 --> 00:14:04,820
If I invert the signal from one to the other,

314
00:14:04,820 --> 00:14:06,130
they'll have exactly canceled.

315
00:14:06,130 --> 00:14:08,030
I have a little photo detector.

316
00:14:08,030 --> 00:14:10,390
It sees nothing, okay?

317
00:14:10,390 --> 00:14:12,120
But now imagine the gravitational wave

318
00:14:12,120 --> 00:14:14,050
went through this same thing.

319
00:14:14,050 --> 00:14:15,550
And 60 times a second,

320
00:14:15,550 --> 00:14:18,250
one arm's gonna get a little longer than the other.

321
00:14:18,250 --> 00:14:20,970
The light will come back at a slightly different time

322
00:14:20,970 --> 00:14:24,770
and the light will go 60 times a second,

323
00:14:24,770 --> 00:14:27,770
depending on how strong the gravitational wave was.

324
00:14:27,770 --> 00:14:28,670
And that's all we have.

325
00:14:28,670 --> 00:14:29,970
We have a detector

326
00:14:29,970 --> 00:14:32,950
that's measuring the length of these two arms.

327
00:14:32,950 --> 00:14:34,400
That's called interferometry.

328
00:14:35,660 --> 00:14:36,500
Two of the people

329
00:14:36,500 --> 00:14:39,310
who believe that interferometry might be the solution

330
00:14:39,310 --> 00:14:41,360
for finding gravitational waves,

331
00:14:41,360 --> 00:14:44,070
and therefore, for finding black holes

332
00:14:44,070 --> 00:14:48,323
{\an8}were Rainer Weiss from MIT and Kip Thorne from Caltech.

333
00:14:50,680 --> 00:14:52,690
I started on the faculty at Caltech

334
00:14:52,690 --> 00:14:55,330
as a particle physicist at the same time

335
00:14:55,330 --> 00:14:57,300
Kip Thorne started as a general relativist,

336
00:14:57,300 --> 00:14:59,430
and we were close friends.

337
00:14:59,430 --> 00:15:00,930
By the 1980s,

338
00:15:00,930 --> 00:15:02,890
several groups from around the world

339
00:15:02,890 --> 00:15:05,140
would start to consider building interferometers

340
00:15:05,140 --> 00:15:07,740
to search for gravitational waves.

341
00:15:07,740 --> 00:15:10,720
The British and Germans formed a collaboration.

342
00:15:10,720 --> 00:15:12,510
The Italians and French

343
00:15:12,510 --> 00:15:15,540
started a collaboration called Virgo.

344
00:15:15,540 --> 00:15:16,930
And in the U.S.,

345
00:15:16,930 --> 00:15:21,930
Rainer Weiss, Ron Drever, and Kip Thorne formed LIGO.

346
00:15:22,230 --> 00:15:24,400
But getting funding to build such a venture

347
00:15:24,400 --> 00:15:25,953
was not going to be easy.

348
00:15:26,950 --> 00:15:29,970
What was pointed out in the U.S. Congress

349
00:15:29,970 --> 00:15:32,680
about whether to appropriate funds

350
00:15:32,680 --> 00:15:35,270
was just how extraordinarily sensitive

351
00:15:35,270 --> 00:15:36,910
these detectors would have to be.

352
00:15:36,910 --> 00:15:41,090
You would need to be able to measure these mirrors

353
00:15:41,090 --> 00:15:42,580
moving at distances

354
00:15:42,580 --> 00:15:45,460
that were some 10,000 times smaller

355
00:15:45,460 --> 00:15:47,960
than the diameter of an atom.

356
00:15:47,960 --> 00:15:51,400
And when thinking about that in an astronomical terms,

357
00:15:51,400 --> 00:15:54,400
that's maybe, say, the same as being able

358
00:15:54,400 --> 00:15:57,570
to measure the distance to the nearest star

359
00:15:57,570 --> 00:15:59,790
and being able to say definitively

360
00:15:59,790 --> 00:16:01,300
whether that distance has changed

361
00:16:01,300 --> 00:16:03,020
by the width of a human hair.

362
00:16:03,020 --> 00:16:05,830
And so these mind-boggling ideas

363
00:16:05,830 --> 00:16:08,630
were used as a way to cast doubt

364
00:16:08,630 --> 00:16:11,563
on the plausibility of such an experiment.

365
00:16:13,450 --> 00:16:14,720
In 1990,

366
00:16:14,720 --> 00:16:16,300
the National Science Foundation

367
00:16:16,300 --> 00:16:19,000
approved the construction of two detectors,

368
00:16:19,000 --> 00:16:23,390
Livingston, Louisiana, and Hanford, Washington State.

369
00:16:23,390 --> 00:16:25,690
But LIGO was going to need a lot of money

370
00:16:25,690 --> 00:16:27,730
and firm leadership

371
00:16:27,730 --> 00:16:30,710
if it was to stand a chance of finding stellar black holes

372
00:16:30,710 --> 00:16:32,273
with gravitational waves.

373
00:16:35,370 --> 00:16:37,850
The Event Horizon Telescope team

374
00:16:37,850 --> 00:16:39,130
that would try to take an image

375
00:16:39,130 --> 00:16:41,180
of a super massive black hole

376
00:16:41,180 --> 00:16:44,480
would not officially form for many more years,

377
00:16:44,480 --> 00:16:47,190
though the ideas upon which it would be based

378
00:16:47,190 --> 00:16:48,653
were beginning to emerge.

379
00:16:49,490 --> 00:16:50,690
When I was in graduate school,

380
00:16:50,690 --> 00:16:53,520
I had the great fortune to work with Dr. Alan Rogers,

381
00:16:53,520 --> 00:16:55,620
who was one of the pioneers of radio astronomy.

382
00:16:55,620 --> 00:16:58,380
And he got me hooked on using interferometry

383
00:16:58,380 --> 00:17:01,630
to make the most detailed images of the sky

384
00:17:01,630 --> 00:17:02,970
that we could make at the time.

385
00:17:02,970 --> 00:17:06,090
And we started doing this with Sagittarius A star,

386
00:17:06,090 --> 00:17:08,000
which we thought was a super massive black hole

387
00:17:08,000 --> 00:17:10,270
in the center of our Milky Way galaxy.

388
00:17:10,270 --> 00:17:12,000
So there is a technique out there

389
00:17:12,000 --> 00:17:14,720
that helps us with increasing the resolution

390
00:17:14,720 --> 00:17:17,150
that we can get from a telescope,

391
00:17:17,150 --> 00:17:19,770
which is not to use a single one,

392
00:17:19,770 --> 00:17:22,560
but to use pairs of telescopes

393
00:17:23,459 --> 00:17:27,380
and look at the distant object at the same time

394
00:17:27,380 --> 00:17:29,240
with these pairs of telescopes,

395
00:17:29,240 --> 00:17:30,910
record the incoming light.

396
00:17:30,910 --> 00:17:35,660
And because we time tag exactly when each signal arrived,

397
00:17:35,660 --> 00:17:38,250
we can after the fact combine these signals

398
00:17:38,250 --> 00:17:39,790
using super computers,

399
00:17:39,790 --> 00:17:41,120
just match them up

400
00:17:41,120 --> 00:17:44,947
and pretend we had the resolution of a telescope

401
00:17:44,947 --> 00:17:47,933
that's as big as the separation between the two.

402
00:17:50,240 --> 00:17:53,250
We call it very long baseline interferometry

403
00:17:53,250 --> 00:17:58,100
and the key thing here is that we interfere the signals

404
00:17:58,100 --> 00:18:00,813
that we receive on different parts of the earth.

405
00:18:02,330 --> 00:18:05,230
To use very long baseline interferometry

406
00:18:05,230 --> 00:18:08,500
or VLBI to actually capture an image

407
00:18:08,500 --> 00:18:10,440
of a super massive black hole

408
00:18:10,440 --> 00:18:13,290
was going to require a radical leap forward

409
00:18:13,290 --> 00:18:15,840
in our understanding of how matter

410
00:18:15,840 --> 00:18:18,540
spins around a black hole that is feeding,

411
00:18:18,540 --> 00:18:21,040
the so-called accretion disk.

412
00:18:21,040 --> 00:18:24,810
I think any revolution requires a group of people

413
00:18:24,810 --> 00:18:26,730
sorting out the ideas that they have,

414
00:18:26,730 --> 00:18:29,100
figuring out what's the best way to move forward.

415
00:18:29,100 --> 00:18:32,870
I met Dimitrios when we were both at Harvard.

416
00:18:32,870 --> 00:18:37,500
In fact, our first paper together is on Sagittarius A star,

417
00:18:37,500 --> 00:18:38,630
the emission from it,

418
00:18:38,630 --> 00:18:42,340
and whether the accretion flow around the black hole

419
00:18:42,340 --> 00:18:45,220
would allow us to see down to the horizon.

420
00:18:45,220 --> 00:18:46,053
It was the time

421
00:18:46,053 --> 00:18:49,050
where we had just started thinking differently

422
00:18:49,050 --> 00:18:52,020
about how do black holes accumulate matter

423
00:18:52,020 --> 00:18:53,340
from their surroundings.

424
00:18:53,340 --> 00:18:55,830
For about 20 to 30 years, there was a paradigm,

425
00:18:55,830 --> 00:18:58,543
but then it became obvious sometime in the '90s

426
00:18:58,543 --> 00:19:01,350
that that paradigm was not right.

427
00:19:01,350 --> 00:19:02,850
So it was that small group

428
00:19:02,850 --> 00:19:04,793
that started building a new paradigm.

429
00:19:05,960 --> 00:19:08,070
We were doing the theoretically, you know?

430
00:19:08,070 --> 00:19:09,090
We were thinking about,

431
00:19:09,090 --> 00:19:11,890
where does this radio emission come from in black holes?

432
00:19:11,890 --> 00:19:14,480
Some people proposed that this would come

433
00:19:14,480 --> 00:19:17,940
from the matter of that shoots out from the plasma jets,

434
00:19:17,940 --> 00:19:19,590
and other colleagues were calculating

435
00:19:19,590 --> 00:19:21,430
that the radio emission would come from the matter

436
00:19:21,430 --> 00:19:22,830
falling into the black hole.

437
00:19:22,830 --> 00:19:25,900
We had group meetings that lasted eight hours.

438
00:19:25,900 --> 00:19:26,810
We just had coffee,

439
00:19:26,810 --> 00:19:29,850
we just had the white board and we were trying out ideas.

440
00:19:29,850 --> 00:19:30,723
And most of them were wrong,

441
00:19:30,723 --> 00:19:32,140
most of them failed,

442
00:19:32,140 --> 00:19:35,290
but a few of them turned out to be really important.

443
00:19:35,290 --> 00:19:37,850
One of those questions that we wanted to ask is,

444
00:19:37,850 --> 00:19:39,530
what would the black hole look like

445
00:19:39,530 --> 00:19:41,170
if I were to take a picture?

446
00:19:41,170 --> 00:19:44,520
Will it be a big fuzzy, fluff of cloud,

447
00:19:44,520 --> 00:19:46,580
or will it be something really small,

448
00:19:46,580 --> 00:19:49,370
as small as the Event Horizon of the black hole?

449
00:19:49,370 --> 00:19:53,120
So we spent about 10 years learning how to tweak the theory

450
00:19:53,120 --> 00:19:54,903
and make predictions of black holes

451
00:19:54,903 --> 00:19:56,560
that were not the same

452
00:19:56,560 --> 00:19:58,710
as the ones that Albert Einstein predicted.

453
00:19:59,920 --> 00:20:01,040
And lo and behold,

454
00:20:01,040 --> 00:20:05,987
we always saw this dark shadow in the very center.

455
00:20:06,973 --> 00:20:10,100
Irrespectively of how the matter was rotating,

456
00:20:10,100 --> 00:20:11,354
whether it was falling in,

457
00:20:11,354 --> 00:20:12,330
whether it was flowing out,

458
00:20:12,330 --> 00:20:14,120
whether the black hole was rotating,

459
00:20:14,120 --> 00:20:16,650
as long as the mass was known as a black hole,

460
00:20:16,650 --> 00:20:18,260
the shadow had to be there.

461
00:20:18,260 --> 00:20:20,210
So in year 2000,

462
00:20:20,210 --> 00:20:23,350
I realized that at certain wavelengths,

463
00:20:23,350 --> 00:20:27,170
the entire accretion flow is actually transparent

464
00:20:27,170 --> 00:20:29,170
and allows us to see all the way down

465
00:20:29,170 --> 00:20:31,020
to the horizon of the black hole,

466
00:20:31,020 --> 00:20:33,740
which is what we're after, that shadow.

467
00:20:33,740 --> 00:20:35,030
How would that look like?

468
00:20:35,030 --> 00:20:36,960
Could we actually see that?

469
00:20:36,960 --> 00:20:38,820
And it turns out that the answer depended on

470
00:20:38,820 --> 00:20:40,300
how did I take the picture,

471
00:20:40,300 --> 00:20:42,487
what wavelengths of light did I use?

472
00:20:45,080 --> 00:20:47,190
This new multinational community

473
00:20:47,190 --> 00:20:50,450
of radio astronomers and theorists realized

474
00:20:50,450 --> 00:20:54,200
that the key was to push very long baseline interferometry

475
00:20:54,200 --> 00:20:56,550
to see higher frequencies of light.

476
00:20:56,550 --> 00:20:58,260
The higher frequency you observe,

477
00:20:58,260 --> 00:20:59,880
the finer your angular resolution.

478
00:20:59,880 --> 00:21:01,820
Your pictures get much crisper

479
00:21:01,820 --> 00:21:04,760
and you can see the details that you want to see.

480
00:21:04,760 --> 00:21:05,700
But the second thing is

481
00:21:05,700 --> 00:21:08,100
that as you move higher in frequency,

482
00:21:08,100 --> 00:21:11,510
you can see more deeply into all the hot gas.

483
00:21:11,510 --> 00:21:14,180
So you really want to see all the way to the event horizon.

484
00:21:14,180 --> 00:21:15,530
You want to get sharper images,

485
00:21:15,530 --> 00:21:18,290
and that pushed us to higher frequencies.

486
00:21:18,290 --> 00:21:20,600
The target that everyone was focusing on

487
00:21:20,600 --> 00:21:22,840
was the suspected super massive black hole

488
00:21:22,840 --> 00:21:26,513
at the center of our galaxy, Sagittarius A star.

489
00:21:27,820 --> 00:21:30,430
I was convinced we would be able to see

490
00:21:30,430 --> 00:21:32,520
the black hole at the center of our Milky Way

491
00:21:32,520 --> 00:21:34,740
with a global telescope array,

492
00:21:34,740 --> 00:21:37,300
but that required a lot of money,

493
00:21:37,300 --> 00:21:39,260
new telescopes, new receivers,

494
00:21:39,260 --> 00:21:43,363
and it required a big community to work together.

495
00:21:47,580 --> 00:21:48,680
There's a transition

496
00:21:48,680 --> 00:21:51,270
that many areas of science go through

497
00:21:51,270 --> 00:21:53,730
in terms of moving from things in the laboratory,

498
00:21:53,730 --> 00:21:57,110
taking those ideas and concepts and scaling them up

499
00:21:57,110 --> 00:22:00,000
to turn those into a large scale project,

500
00:22:00,000 --> 00:22:02,130
it's a skill in itself.

501
00:22:02,130 --> 00:22:02,963
Barry Barish

502
00:22:02,963 --> 00:22:04,900
had been working in particle physics

503
00:22:04,900 --> 00:22:08,380
at the superconducting supercollider in Texas.

504
00:22:08,380 --> 00:22:11,340
The U.S. Congress canceled the supercollider

505
00:22:11,340 --> 00:22:14,820
at a time when LIGO needed somebody

506
00:22:14,820 --> 00:22:16,810
that was capable of taking it

507
00:22:16,810 --> 00:22:19,607
to get both the funding that was needed

508
00:22:19,607 --> 00:22:21,460
and be able to put it together

509
00:22:21,460 --> 00:22:23,700
in a way that would make it work.

510
00:22:23,700 --> 00:22:27,010
In 1994, the National Science Foundation

511
00:22:27,010 --> 00:22:30,420
made Barish the laboratory director of LIGO.

512
00:22:30,420 --> 00:22:31,730
About six months later,

513
00:22:31,730 --> 00:22:33,820
went to the National Science Board

514
00:22:33,820 --> 00:22:36,170
that oversees the National Science Foundation,

515
00:22:36,170 --> 00:22:38,133
and convinced them, and they funded us.

516
00:22:40,220 --> 00:22:43,710
I think the real hero is not me, it's the NSF.

517
00:22:43,710 --> 00:22:46,950
For me, the big issue was to get a strong enough team,

518
00:22:46,950 --> 00:22:48,920
as good as these two institutions are,

519
00:22:48,920 --> 00:22:50,210
Caltech and MIT.

520
00:22:50,210 --> 00:22:52,380
For our problem as hard as gravitational waves,

521
00:22:52,380 --> 00:22:55,460
we needed to tap the best people in the world.

522
00:22:55,460 --> 00:22:57,890
The underlying technologies

523
00:22:57,890 --> 00:23:00,060
that are relevant for gravitational wave detection

524
00:23:00,060 --> 00:23:03,010
were being developed in different places.

525
00:23:03,010 --> 00:23:04,530
In 1997,

526
00:23:04,530 --> 00:23:07,940
Barish established the LIGO Scientific Collaboration,

527
00:23:07,940 --> 00:23:11,730
which merged several international groups into LIGO.

528
00:23:11,730 --> 00:23:15,250
This meant there were now two major multinational groups

529
00:23:15,250 --> 00:23:17,120
vying to build detectors,

530
00:23:17,120 --> 00:23:18,723
LIGO and Virgo.

531
00:23:20,820 --> 00:23:24,140
The group that would become the Event Horizon Telescope

532
00:23:24,140 --> 00:23:25,863
were also making progress.

533
00:23:27,730 --> 00:23:29,120
So we all started to work together

534
00:23:29,120 --> 00:23:31,140
at three millimeter wavelengths,

535
00:23:31,140 --> 00:23:33,110
and then we realized that to push it even further,

536
00:23:33,110 --> 00:23:34,790
we had to go to one millimeter wavelength.

537
00:23:34,790 --> 00:23:37,430
And that's when we began this little race,

538
00:23:37,430 --> 00:23:40,610
a competitive but also a collegial race.

539
00:23:40,610 --> 00:23:44,610
Could we push this technique to its real limits?

540
00:23:44,610 --> 00:23:46,650
And that was great time.

541
00:23:46,650 --> 00:23:48,683
And then we ran into this roadblock.

542
00:23:50,810 --> 00:23:52,950
For many years, we were stymied.

543
00:23:52,950 --> 00:23:54,060
We were just stuck

544
00:23:54,060 --> 00:23:56,270
because we didn't have the sensitivity we needed

545
00:23:56,270 --> 00:23:58,720
to make these observations at high frequencies.

546
00:23:58,720 --> 00:24:00,370
As soon as you go to high frequencies,

547
00:24:00,370 --> 00:24:01,600
everything becomes harder.

548
00:24:01,600 --> 00:24:05,003
The atmosphere reduces the signal coming from black holes.

549
00:24:06,450 --> 00:24:08,680
The superconducting cameras

550
00:24:08,680 --> 00:24:10,520
that we mount on each of our telescopes

551
00:24:10,520 --> 00:24:13,580
to receive the radio waves from the black hole,

552
00:24:13,580 --> 00:24:14,840
they become more noisy.

553
00:24:14,840 --> 00:24:17,110
So everything is working against you.

554
00:24:17,110 --> 00:24:18,560
The one thing that we had,

555
00:24:18,560 --> 00:24:21,593
our secret weapon was that we could increase the bandwidth.

556
00:24:23,180 --> 00:24:27,050
Starting at around 2000 and going til about 2006,

557
00:24:27,050 --> 00:24:29,710
there was this explosion in capability

558
00:24:29,710 --> 00:24:33,460
that happened because we started building our instruments

559
00:24:33,460 --> 00:24:35,580
out of commercial electronics.

560
00:24:35,580 --> 00:24:36,660
Imagine that.

561
00:24:36,660 --> 00:24:37,830
Up until that point,

562
00:24:37,830 --> 00:24:41,610
we had been developing specialized instrumentation

563
00:24:41,610 --> 00:24:43,450
that took a decade to design,

564
00:24:43,450 --> 00:24:45,420
and manufacturer, and get into the field

565
00:24:45,420 --> 00:24:47,613
because it was so exquisitely specialized.

566
00:24:48,820 --> 00:24:51,690
Graphics processing units or GPUs

567
00:24:51,690 --> 00:24:53,650
are specialized computer chips

568
00:24:53,650 --> 00:24:56,423
that are used primarily for video graphics.

569
00:24:57,550 --> 00:25:00,290
We weren't pushing the development of GPUs.

570
00:25:00,290 --> 00:25:03,110
In fact, the gaming industry was,

571
00:25:03,110 --> 00:25:04,410
but we thought, hey,

572
00:25:04,410 --> 00:25:07,140
we can solve Einstein's equations on these things

573
00:25:07,140 --> 00:25:11,053
and we can do it much faster than with traditional CPUs.

574
00:25:12,290 --> 00:25:14,500
The same was true for data storage.

575
00:25:14,500 --> 00:25:17,370
Consumer hard drives were becoming ever faster

576
00:25:17,370 --> 00:25:19,530
and greater in capacity.

577
00:25:19,530 --> 00:25:21,550
All of a sudden, we could go to the store,

578
00:25:21,550 --> 00:25:23,840
buy components, hook them together,

579
00:25:23,840 --> 00:25:27,040
and we could make something that was 10 times more capable,

580
00:25:27,040 --> 00:25:28,930
10 times lower cost,

581
00:25:28,930 --> 00:25:31,430
and we could design it 10 times faster.

582
00:25:31,430 --> 00:25:33,817
It was nothing short of a miracle.

583
00:25:38,360 --> 00:25:39,890
The LIGO detectors had to be

584
00:25:39,890 --> 00:25:43,430
the most sensitive scientific instruments in the world.

585
00:25:43,430 --> 00:25:47,663
And it's all because our planet is such a noisy place.

586
00:25:48,610 --> 00:25:50,820
Much of the good work happens at night,

587
00:25:50,820 --> 00:25:53,730
and that's simply because the environment around you

588
00:25:53,730 --> 00:25:55,020
is quieter at night.

589
00:25:55,020 --> 00:25:57,580
There are fewer cars driving on the road,

590
00:25:57,580 --> 00:26:00,040
hitting bumps and causing the ground to shake,

591
00:26:00,040 --> 00:26:03,210
people, falling trees that are falling down in the forest.

592
00:26:03,210 --> 00:26:05,340
The operation of heavy machinery nearby,

593
00:26:05,340 --> 00:26:07,353
it's also lower at night.

594
00:26:08,860 --> 00:26:10,770
There's also natural effects.

595
00:26:10,770 --> 00:26:13,600
Of course, earthquakes are an obvious consideration

596
00:26:13,600 --> 00:26:15,570
that might jump into many people's minds.

597
00:26:15,570 --> 00:26:16,403
Believe it or not,

598
00:26:16,403 --> 00:26:18,470
even if you're in the center of a continent,

599
00:26:18,470 --> 00:26:22,840
there is a peak of motion that occurs at very low frequency

600
00:26:22,840 --> 00:26:25,023
due to waves beating on the ocean shore.

601
00:26:27,060 --> 00:26:30,230
The reason that all of these sorts of things matter

602
00:26:30,230 --> 00:26:32,010
is because ultimately,

603
00:26:32,010 --> 00:26:34,900
these mirrors that we're trying to detect

604
00:26:34,900 --> 00:26:38,480
very small motions of are connected to the ground.

605
00:26:38,480 --> 00:26:41,290
The earth ground is shaking all the time

606
00:26:41,290 --> 00:26:43,500
by about a millionth of a meter,

607
00:26:43,500 --> 00:26:46,400
which is a million of a million times more

608
00:26:46,400 --> 00:26:47,780
than what we're trying to measure.

609
00:26:47,780 --> 00:26:50,400
So this is one reason that our system

610
00:26:50,400 --> 00:26:52,110
can not just sit on the ground,

611
00:26:52,110 --> 00:26:57,060
but our mirrors are the most quiet place on earth.

612
00:26:57,060 --> 00:26:58,823
The beam splitter itself is a mirror,

613
00:26:58,823 --> 00:27:01,480
a big piece of glass suspended on wires.

614
00:27:01,480 --> 00:27:05,560
That has to be isolated from external disturbances,

615
00:27:05,560 --> 00:27:07,750
so it's housed inside a vacuum tank.

616
00:27:07,750 --> 00:27:10,193
That vacuum tank is inside a big building.

617
00:27:12,140 --> 00:27:14,920
Out from that building go two arms.

618
00:27:14,920 --> 00:27:18,064
Inside that arch, there's a vacuum pipe.

619
00:27:18,064 --> 00:27:20,690
Inside that travel the laser beams

620
00:27:20,690 --> 00:27:23,480
that travel the length of these four kilometer arms.

621
00:27:23,480 --> 00:27:25,800
The ends of the arms inside those buildings,

622
00:27:25,800 --> 00:27:28,040
there are vacuum tanks.

623
00:27:28,040 --> 00:27:32,070
Inside those tanks are some isolation systems

624
00:27:32,070 --> 00:27:34,840
that isolate from ground vibrations,

625
00:27:34,840 --> 00:27:37,780
mirrors that are suspended in the initial incarnation

626
00:27:37,780 --> 00:27:40,263
of LIGO on metal wires.

627
00:27:41,810 --> 00:27:44,080
But it's not just vibrations and noise

628
00:27:44,080 --> 00:27:46,110
that LIGO has to fight against,

629
00:27:46,110 --> 00:27:49,700
but barely imaginable quantum effects.

630
00:27:49,700 --> 00:27:52,300
To measure precisely how the two waves get together,

631
00:27:52,300 --> 00:27:55,800
you have to measure how many photons hit your detector.

632
00:27:55,800 --> 00:27:57,560
But since the number of photons

633
00:27:57,560 --> 00:27:59,290
is what we call a quantum variable,

634
00:27:59,290 --> 00:28:01,380
there's an intrinsic uncertainty there.

635
00:28:01,380 --> 00:28:02,650
We cannot do better

636
00:28:02,650 --> 00:28:06,050
than what the Heisenberg uncertainty principle dictate.

637
00:28:06,050 --> 00:28:08,910
That's one reason we need very powerful lasers.

638
00:28:08,910 --> 00:28:11,070
As we increase the laser power,

639
00:28:11,070 --> 00:28:14,980
the force exerted by the light on the mirrors

640
00:28:14,980 --> 00:28:16,860
also increases proportionally.

641
00:28:16,860 --> 00:28:18,660
So that becomes one of the big challenges

642
00:28:18,660 --> 00:28:20,403
of increasing the laser power.

643
00:28:21,270 --> 00:28:25,050
Every time a photon bounces off our suspended mirror,

644
00:28:25,050 --> 00:28:27,780
it transfers some momentum to the mirror.

645
00:28:27,780 --> 00:28:28,750
It gives it a kick,

646
00:28:28,750 --> 00:28:31,360
If it were to strike it off center,

647
00:28:31,360 --> 00:28:33,560
it's going to actually create a torque.

648
00:28:33,560 --> 00:28:36,030
The light causes the mirrors to twist.

649
00:28:36,030 --> 00:28:37,280
In an ideal situation,

650
00:28:37,280 --> 00:28:40,890
you would have the light striking the center of the mirror.

651
00:28:40,890 --> 00:28:44,260
So to be able to understand more about black holes

652
00:28:44,260 --> 00:28:46,190
and big stuff out there in the universe,

653
00:28:46,190 --> 00:28:47,860
we need to understand very well

654
00:28:47,860 --> 00:28:50,320
the physics of the quantum mechanics

655
00:28:50,320 --> 00:28:51,200
and the thermal motion of the atom,

656
00:28:51,200 --> 00:28:53,403
which is very small scale physics.

657
00:28:56,220 --> 00:28:57,350
In 2006,

658
00:28:57,350 --> 00:29:00,950
we fielded these new electronic systems for the first time,

659
00:29:00,950 --> 00:29:02,440
ad we took them to two sites,

660
00:29:02,440 --> 00:29:04,170
one in Arizona, Mount Graham,

661
00:29:04,170 --> 00:29:06,610
and one to Mauna Kea in Hawaii.

662
00:29:06,610 --> 00:29:08,650
We set up this experiment,

663
00:29:08,650 --> 00:29:12,020
but we were really flying a bit by the seat of our pants.

664
00:29:12,020 --> 00:29:13,260
So back at the core later,

665
00:29:13,260 --> 00:29:15,590
we played these data streams from Hawaii

666
00:29:15,590 --> 00:29:19,070
and Arizona back again, and again, and again.

667
00:29:19,070 --> 00:29:20,610
And we searched for months.

668
00:29:20,610 --> 00:29:22,000
And it was a heartbreaker.

669
00:29:22,000 --> 00:29:24,150
After months, we threw in the towel.

670
00:29:24,150 --> 00:29:26,280
We realized that we were just not gonna be able

671
00:29:26,280 --> 00:29:28,733
to detect Sagittarius A star.

672
00:29:29,700 --> 00:29:31,500
Later, we found out why.

673
00:29:31,500 --> 00:29:33,970
A small little chip of metal

674
00:29:33,970 --> 00:29:38,140
had fallen into the heart of the superconducting junction

675
00:29:38,140 --> 00:29:41,293
in the receiver of the Caltech Submillimeter Observatory.

676
00:29:44,430 --> 00:29:45,870
We were able to go back the next year,

677
00:29:45,870 --> 00:29:47,683
adding a new site in California.

678
00:29:48,980 --> 00:29:50,980
And this time, we were successful.

679
00:29:50,980 --> 00:29:52,260
We got the detections.

680
00:29:52,260 --> 00:29:53,970
And that showed us immediately

681
00:29:53,970 --> 00:29:56,390
that we were seeing horizon scale structure.

682
00:29:56,390 --> 00:29:57,860
That's the moment we knew

683
00:29:57,860 --> 00:30:00,277
that we could make an image of a black hole.

684
00:30:03,230 --> 00:30:05,530
The LIGO team was sure they had detectors

685
00:30:05,530 --> 00:30:06,680
that were working well,

686
00:30:07,930 --> 00:30:10,360
but if black holes were spiraling into one another

687
00:30:10,360 --> 00:30:11,840
somewhere in the universe,

688
00:30:11,840 --> 00:30:13,173
they were not hearing it.

689
00:30:14,990 --> 00:30:16,550
You don't know that you don't see something

690
00:30:16,550 --> 00:30:18,190
until you look for a while.

691
00:30:18,190 --> 00:30:22,940
And so it would run for six months or a year,

692
00:30:22,940 --> 00:30:25,293
and wouldn't see any events.

693
00:30:26,690 --> 00:30:28,500
We'd turn off, lick our wounds,

694
00:30:28,500 --> 00:30:30,843
put in some improvements, and then run again.

695
00:30:32,280 --> 00:30:33,870
But I think that is also maybe part of the excitement.

696
00:30:33,870 --> 00:30:35,530
So there was years, and years, and years

697
00:30:35,530 --> 00:30:37,650
of continually improving the detectors,

698
00:30:37,650 --> 00:30:38,770
collecting data, improving them,

699
00:30:38,770 --> 00:30:42,870
collecting data on no detection, no detection, no detection.

700
00:30:42,870 --> 00:30:46,220
There were times where myself or the community thought

701
00:30:46,220 --> 00:30:50,000
that maybe we got ourself into something too big.

702
00:30:50,000 --> 00:30:52,410
The initial version of LIGO wasn't good enough

703
00:30:52,410 --> 00:30:53,830
to see gravitational waves,

704
00:30:53,830 --> 00:30:54,737
it turns out.

705
00:30:56,370 --> 00:30:57,203
In 2010,

706
00:30:57,203 --> 00:30:59,470
the detectives were scheduled to shut down

707
00:30:59,470 --> 00:31:04,340
in preparation for a big upgrade called advanced LIGO.

708
00:31:04,340 --> 00:31:07,630
The team trying to make an image of a black hole realized

709
00:31:07,630 --> 00:31:08,950
that the friendly competition

710
00:31:08,950 --> 00:31:12,200
between several European and U.S. institutions

711
00:31:12,200 --> 00:31:14,330
wasn't going to be enough.

712
00:31:14,330 --> 00:31:16,530
We would need many more dishes.

713
00:31:16,530 --> 00:31:17,850
We would need the European dishes,

714
00:31:17,850 --> 00:31:19,580
we need the American dishes.

715
00:31:19,580 --> 00:31:21,250
So it was clear at some point,

716
00:31:21,250 --> 00:31:24,030
those different efforts had to come together

717
00:31:24,030 --> 00:31:25,943
and merge into a global collaboration.

718
00:31:28,020 --> 00:31:31,127
And so there was a meeting in 2009 in California,

719
00:31:31,127 --> 00:31:33,540
and I was sitting there at a coffee break together

720
00:31:33,540 --> 00:31:35,190
with Shep Doeleman and was saying,

721
00:31:35,190 --> 00:31:37,640
if we want to get this funded later,

722
00:31:37,640 --> 00:31:38,563
we can't just keep talking about

723
00:31:38,563 --> 00:31:41,380
submillimeter VLBI array, blah, blah, blah.

724
00:31:41,380 --> 00:31:42,700
Nobody will understand what it is.

725
00:31:42,700 --> 00:31:44,810
We have to give it a flashy name.

726
00:31:44,810 --> 00:31:48,580
What about if we call it Event Horizon array

727
00:31:48,580 --> 00:31:49,413
or something like this?

728
00:31:49,413 --> 00:31:53,150
And in the end, we came down to Event Horizon Telescope,

729
00:31:53,150 --> 00:31:54,450
and that's how it started.

730
00:31:55,870 --> 00:31:58,600
The Event Horizon Telescope was finally

731
00:31:58,600 --> 00:31:59,823
and officially born.

732
00:32:01,110 --> 00:32:04,410
Meanwhile, LIGO was in the middle of its upgrade

733
00:32:04,410 --> 00:32:07,150
from initial LIGO to advanced.

734
00:32:07,150 --> 00:32:09,750
We wanted to build a very sensitive instrument.

735
00:32:09,750 --> 00:32:14,750
And that meant that we had to take some risks, if you want.

736
00:32:14,840 --> 00:32:15,700
Much of the effort

737
00:32:15,700 --> 00:32:18,210
that went into the advanced LIGO upgrade

738
00:32:18,210 --> 00:32:19,750
involved the mirrors

739
00:32:19,750 --> 00:32:23,410
and how they were isolated from the outside world.

740
00:32:23,410 --> 00:32:26,870
So instead of suspending these mirrors on metal wires,

741
00:32:26,870 --> 00:32:30,550
we were actually suspending them on glass fibers,

742
00:32:30,550 --> 00:32:32,123
fused silica fibers.

743
00:32:33,586 --> 00:32:36,910
Those fibers, they're very strong if you pull them,

744
00:32:36,910 --> 00:32:39,933
but if a grain of dust hit them, they shatter.

745
00:32:40,950 --> 00:32:42,660
Perhaps the greatest secret weapon

746
00:32:42,660 --> 00:32:44,550
that the LIGO team employed

747
00:32:44,550 --> 00:32:48,120
to isolate their detectives from unwanted vibrations

748
00:32:48,120 --> 00:32:50,120
was the same technology found

749
00:32:50,120 --> 00:32:52,383
in noise cancellation headphones.

750
00:32:53,270 --> 00:32:56,170
You put on these earphones on an airplane

751
00:32:56,170 --> 00:32:58,103
and the roar of the engines goes away,

752
00:32:59,420 --> 00:33:01,320
and you still hear the stewardess ask you,

753
00:33:01,320 --> 00:33:03,130
do you want coffee?

754
00:33:03,130 --> 00:33:07,010
So what it does is measure the ambient noise of the engines

755
00:33:07,010 --> 00:33:08,370
and cancel it.

756
00:33:08,370 --> 00:33:10,690
But the stewardess talking to you,

757
00:33:10,690 --> 00:33:12,380
it's not ambient, it's a signal,

758
00:33:12,380 --> 00:33:14,090
and so you hear that fine.

759
00:33:14,090 --> 00:33:17,740
So the idea was to bury inside of these shock absorbers

760
00:33:17,740 --> 00:33:19,810
little seismic sensors

761
00:33:19,810 --> 00:33:22,900
that measured any residual motion of the earth.

762
00:33:22,900 --> 00:33:25,430
And then we just pushed back against it,

763
00:33:25,430 --> 00:33:27,330
make little actuators that push

764
00:33:27,330 --> 00:33:29,630
to cancel the residual motion that's there

765
00:33:29,630 --> 00:33:31,480
after the shock absorbers.

766
00:33:31,480 --> 00:33:35,193
And that gained us a factor of 10 in sensitivity.

767
00:33:37,990 --> 00:33:40,270
The Event Horizon Telescope group

768
00:33:40,270 --> 00:33:42,170
had begun to consider trying to image

769
00:33:42,170 --> 00:33:44,180
another super massive black hole,

770
00:33:44,180 --> 00:33:46,233
as well as Sagittarius S star.

771
00:33:47,740 --> 00:33:50,000
There was another black hole out there,

772
00:33:50,000 --> 00:33:52,230
which was 1,000 times further way,

773
00:33:52,230 --> 00:33:54,853
but also 1,000 times more massive.

774
00:33:55,990 --> 00:33:57,330
M87 is a galaxy

775
00:33:57,330 --> 00:34:00,420
about 53 million light years from earth.

776
00:34:00,420 --> 00:34:02,080
And just like the Milky Way,

777
00:34:02,080 --> 00:34:06,240
we suspect it has a super massive black hole at its center,

778
00:34:06,240 --> 00:34:08,613
only one that is much bigger.

779
00:34:09,490 --> 00:34:11,040
M87 is so massive

780
00:34:11,040 --> 00:34:13,330
that it doesn't change during the course of an evening,

781
00:34:13,330 --> 00:34:16,410
whereas Sagittarius A star is speedier.

782
00:34:16,410 --> 00:34:18,110
And during the course of a night,

783
00:34:18,110 --> 00:34:19,833
it changes its appearance.

784
00:34:21,160 --> 00:34:23,030
The advanced LIGO detectors

785
00:34:23,030 --> 00:34:25,080
were now successfully upgraded

786
00:34:25,080 --> 00:34:27,120
and showing much higher sensitivity

787
00:34:27,120 --> 00:34:29,033
than anything achieved before.

788
00:34:30,180 --> 00:34:32,930
When we start a data run each year when we do this,

789
00:34:32,930 --> 00:34:34,650
there's a little period of time

790
00:34:34,650 --> 00:34:37,980
when people who are expert on particular things

791
00:34:37,980 --> 00:34:40,870
can still decide to make some changes of settings,

792
00:34:40,870 --> 00:34:42,340
so we call it an engineering run.

793
00:34:42,340 --> 00:34:43,890
It happened during that period.

794
00:34:45,720 --> 00:34:48,310
You can imagine I can remember very well that day.

795
00:34:48,310 --> 00:34:49,143
So it was a Monday.

796
00:34:49,143 --> 00:34:50,300
And I remember that

797
00:34:50,300 --> 00:34:53,760
because that was the day after I ran my first marathon,

798
00:34:53,760 --> 00:34:55,950
so I was thinking that there was enough excitement

799
00:34:55,950 --> 00:34:57,320
for a while, right?

800
00:34:57,320 --> 00:35:00,430
I remember that quite vividly in my office in Glasgow

801
00:35:00,430 --> 00:35:01,790
when our colleague suddenly said,

802
00:35:01,790 --> 00:35:03,619
You do know the signal had just arrived?"

803
00:35:03,619 --> 00:35:05,320
And we were like, "No?"

804
00:35:05,320 --> 00:35:07,180
My colleague came to tell me

805
00:35:07,180 --> 00:35:09,880
that it seems there's been a detection.

806
00:35:09,880 --> 00:35:12,480
I just brushed this comment off.

807
00:35:12,480 --> 00:35:13,890
To me, it seemed, oh,

808
00:35:13,890 --> 00:35:16,630
like we're not even in the observation run yet.

809
00:35:16,630 --> 00:35:18,780
It's too early for this to actually happen.

810
00:35:21,940 --> 00:35:23,320
When that event happened,

811
00:35:23,320 --> 00:35:27,120
it happened seven milliseconds earlier in Louisiana

812
00:35:27,120 --> 00:35:28,313
than in Hanford.

813
00:35:31,420 --> 00:35:33,850
And my first thought was, this can't be real.

814
00:35:33,850 --> 00:35:35,100
This too good to be real.

815
00:35:37,140 --> 00:35:38,020
And you have to imagine

816
00:35:38,020 --> 00:35:41,830
for people who have spent decades measuring noise,

817
00:35:41,830 --> 00:35:44,290
and being very good at mentioning noise,

818
00:35:44,290 --> 00:35:47,090
to have a signal arrive and it be large,

819
00:35:47,090 --> 00:35:49,443
it really did take people by surprise.

820
00:35:51,020 --> 00:35:52,030
The detection made

821
00:35:52,030 --> 00:35:55,240
on the 14th of September, 2015

822
00:35:55,240 --> 00:35:57,040
was calculated to have been created

823
00:35:57,040 --> 00:36:00,070
by the merging of two stellar mass black holes

824
00:36:00,070 --> 00:36:02,773
1.3 billion light years from earth.

825
00:36:05,230 --> 00:36:08,030
We were expecting to have to fight our way

826
00:36:08,030 --> 00:36:11,250
through a lot of justification to convince people

827
00:36:11,250 --> 00:36:13,520
that we really had to think of additional ways,

828
00:36:13,520 --> 00:36:15,610
but that was exactly what you would expect

829
00:36:15,610 --> 00:36:16,523
out of a textbook.

830
00:36:18,780 --> 00:36:21,240
So the first thing I thought is, this is not real.

831
00:36:21,240 --> 00:36:23,000
Somebody did this,

832
00:36:23,000 --> 00:36:23,833
because at the time,

833
00:36:23,833 --> 00:36:26,150
we had a program which was called blind injections

834
00:36:26,150 --> 00:36:27,720
to test if you were actually able

835
00:36:27,720 --> 00:36:29,060
to detect gravitational waves.

836
00:36:29,060 --> 00:36:31,480
Some people, without telling anybody,

837
00:36:31,480 --> 00:36:34,360
would add on purpose fake signals.

838
00:36:34,360 --> 00:36:37,230
So all I could think is that, great,

839
00:36:37,230 --> 00:36:38,860
this is an artificial signal.

840
00:36:38,860 --> 00:36:41,410
But we got word from whoever was in charge

841
00:36:41,410 --> 00:36:43,680
of this blind injection saying, no,

842
00:36:43,680 --> 00:36:45,660
we didn't have time to set up our systems.

843
00:36:45,660 --> 00:36:46,800
Sorry, we're late.

844
00:36:46,800 --> 00:36:48,773
So this is not a blind injection.

845
00:36:51,160 --> 00:36:52,640
But that was not the end of the story.

846
00:36:52,640 --> 00:36:56,620
That was the beginning of maybe six months of very hard work

847
00:36:56,620 --> 00:37:00,183
to try and prove that we didn't do anything wrong.

848
00:37:02,320 --> 00:37:03,990
Because you don't want to cry wolf

849
00:37:03,990 --> 00:37:07,070
the first time that you detect a gravitational wave

850
00:37:07,070 --> 00:37:09,550
'cause that had happened in the history in the past.

851
00:37:09,550 --> 00:37:10,700
So we don't want to do that

852
00:37:10,700 --> 00:37:12,950
because then you lose credibility, of course.

853
00:37:13,960 --> 00:37:18,110
I think for many people, justifiably, after many years,

854
00:37:18,110 --> 00:37:20,160
they had a eureka moment.

855
00:37:20,160 --> 00:37:22,353
And I had a moment of panic.

856
00:37:23,330 --> 00:37:26,983
All I could do is figure out how we had gone wrong.

857
00:37:28,800 --> 00:37:30,480
There then followed a frantic

858
00:37:30,480 --> 00:37:33,810
and intensely busy period of forensically analyzing

859
00:37:33,810 --> 00:37:36,113
whether they believed their own data.

860
00:37:37,580 --> 00:37:40,100
After a month, we met and we decided it was real

861
00:37:40,100 --> 00:37:41,400
and I thought it was real.

862
00:37:42,260 --> 00:37:44,070
That moment of looking at the data

863
00:37:44,070 --> 00:37:46,190
really kind of made me jump.

864
00:37:46,190 --> 00:37:48,610
We kept it quiet even though we have 1,000 people.

865
00:37:48,610 --> 00:37:51,417
We had one office with several students in it

866
00:37:51,417 --> 00:37:53,250
and all of them apart from one

867
00:37:53,250 --> 00:37:54,920
were in the LIGO collaboration.

868
00:37:54,920 --> 00:37:58,370
So this poor one student for about six months,

869
00:37:58,370 --> 00:37:59,990
every time he walked into the office,

870
00:37:59,990 --> 00:38:01,540
everybody stopped talking.

871
00:38:01,540 --> 00:38:03,690
And he would just must've been wondering

872
00:38:03,690 --> 00:38:05,160
what he had done wrong.

873
00:38:05,160 --> 00:38:06,533
Was it him, was it me?

874
00:38:08,710 --> 00:38:10,130
Barry and his team agreed

875
00:38:10,130 --> 00:38:12,440
that they would publish their results in the journal,

876
00:38:12,440 --> 00:38:15,623
Physical Review Letters, before Christmas 2015.

877
00:38:17,010 --> 00:38:19,100
We had our final meeting to decide

878
00:38:19,100 --> 00:38:20,430
that it was ready to go,

879
00:38:20,430 --> 00:38:22,310
but it hung up in that meeting.

880
00:38:22,310 --> 00:38:24,120
We couldn't agree to publish it.

881
00:38:24,120 --> 00:38:25,447
So, why?

882
00:38:25,447 --> 00:38:27,890
Basically, we argued over adjectives.

883
00:38:27,890 --> 00:38:30,850
Is the title discovery of gravitational waves?

884
00:38:30,850 --> 00:38:32,840
Is a title evidence for?

885
00:38:32,840 --> 00:38:34,400
Anyway, we hung up on this.

886
00:38:34,400 --> 00:38:37,170
And so it took another, I don't know, week.

887
00:38:37,170 --> 00:38:41,240
And then we call Physical Review Letters and they said,

888
00:38:41,240 --> 00:38:42,700
oops, it's too late.

889
00:38:42,700 --> 00:38:44,520
It's too close to Christmas.

890
00:38:44,520 --> 00:38:45,353
So we said, okay then,

891
00:38:45,353 --> 00:38:48,750
we're not giving it to you until after Christmas vacation.

892
00:38:48,750 --> 00:38:52,720
I tell this story because on December 26th, Boxing Day,

893
00:38:52,720 --> 00:38:54,093
we saw our second event.

894
00:38:55,500 --> 00:38:56,980
Only three and a half months

895
00:38:56,980 --> 00:38:58,270
after the first one,

896
00:38:58,270 --> 00:39:02,060
another black hole merger has been detected.

897
00:39:02,060 --> 00:39:05,290
And even though I had gone through all this intense fall

898
00:39:05,290 --> 00:39:08,680
and was absolutely, I thought, convinced,

899
00:39:08,680 --> 00:39:12,850
seeing the second event was a sigh of relief in me.

900
00:39:12,850 --> 00:39:15,000
I didn't anticipate it,

901
00:39:15,000 --> 00:39:16,920
but there's something about confirmation,

902
00:39:16,920 --> 00:39:18,610
no matter how much you look at something

903
00:39:18,610 --> 00:39:20,060
and believe what you've done.

904
00:39:21,540 --> 00:39:23,881
In February, 2016,

905
00:39:23,881 --> 00:39:27,880
LIGO, in collaboration with Virgo, told the world.

906
00:39:27,880 --> 00:39:29,030
{\an8}Ladies and gentlemen,

907
00:39:30,910 --> 00:39:35,080
{\an8}we have detected gravitational waves.

908
00:39:35,080 --> 00:39:35,913
{\an8}We did it.

909
00:39:42,770 --> 00:39:44,740
The discovery of gravitational waves,

910
00:39:44,740 --> 00:39:46,300
probably the brightest discovery

911
00:39:46,300 --> 00:39:49,710
since we first learned that the universe was expanding.

912
00:39:49,710 --> 00:39:51,870
Not only do we now have to believe in black holes,

913
00:39:51,870 --> 00:39:54,350
we have to believe that they collide too.

914
00:39:54,350 --> 00:39:56,810
Seeing the first detection of gravitational waves

915
00:39:56,810 --> 00:39:57,980
while we were still in the thick

916
00:39:57,980 --> 00:40:00,190
of doing the Event Horizon Telescope observations

917
00:40:00,190 --> 00:40:02,490
was awesome, was remarkable.

918
00:40:02,490 --> 00:40:04,560
There's always been a little bit of friendly competition

919
00:40:04,560 --> 00:40:07,150
with the LIGO team,

920
00:40:07,150 --> 00:40:08,380
although I would say that I think

921
00:40:08,380 --> 00:40:10,823
people didn't appreciate how close we came.

922
00:40:12,610 --> 00:40:14,980
We accreted new partners in Europe,

923
00:40:14,980 --> 00:40:16,900
new partners even from Asia,

924
00:40:16,900 --> 00:40:18,600
and we all began to work together.

925
00:40:19,450 --> 00:40:22,023
And finally in 2017, we were ready.

926
00:40:23,100 --> 00:40:25,820
But a telescope that covers the whole planet

927
00:40:25,820 --> 00:40:28,850
has some uniquely frustrating problems.

928
00:40:28,850 --> 00:40:29,930
With normal astronomy,

929
00:40:29,930 --> 00:40:31,860
you need good weather at just the telescope

930
00:40:31,860 --> 00:40:32,760
that you're observing with.

931
00:40:32,760 --> 00:40:34,970
But for very long baseline interferometry,

932
00:40:34,970 --> 00:40:37,320
you need weather to be good all over the globe.

933
00:40:38,340 --> 00:40:42,597
{\an8}And I was going up to the 30 meter dish at IRAM,

934
00:40:42,597 --> 00:40:44,113
but it was perfect weather.

935
00:40:46,350 --> 00:40:48,560
And it was perfect weather all around the world

936
00:40:48,560 --> 00:40:49,930
in the other places.

937
00:40:49,930 --> 00:40:51,330
And I said, this can't be.

938
00:40:51,330 --> 00:40:53,040
We have good weather here.

939
00:40:53,040 --> 00:40:55,430
And I was just nervously looking at the hard drives

940
00:40:55,430 --> 00:40:56,310
and the equipment,

941
00:40:56,310 --> 00:40:58,387
but all the equipment was working.

942
00:40:58,387 --> 00:41:00,520
(people cheering)

943
00:41:00,520 --> 00:41:02,190
At each of these telescopes,

944
00:41:02,190 --> 00:41:04,050
we have what's called a hydrogen maser

945
00:41:04,050 --> 00:41:05,600
that time tags the data.

946
00:41:05,600 --> 00:41:08,060
It's digitized, stored on a hard disk drive.

947
00:41:08,060 --> 00:41:09,510
And they're sent by trucks,

948
00:41:09,510 --> 00:41:13,320
by planes to a central facility where they're played back.

949
00:41:13,320 --> 00:41:15,610
The first data was coming back to Haystack

950
00:41:15,610 --> 00:41:17,380
and they were doing the first correlations

951
00:41:17,380 --> 00:41:19,750
and the first success messages came.

952
00:41:19,750 --> 00:41:21,180
These two telescopes work together,

953
00:41:21,180 --> 00:41:23,130
these two telescopes work together.

954
00:41:23,130 --> 00:41:25,060
And after a few weeks and months,

955
00:41:25,060 --> 00:41:27,380
we knew it probably worked.

956
00:41:27,380 --> 00:41:29,323
We didn't know what it was showing us.

957
00:41:30,680 --> 00:41:34,210
That moment of joy and epiphany came

958
00:41:34,210 --> 00:41:38,770
when we saw the data making this ringing pattern.

959
00:41:38,770 --> 00:41:41,620
And it was the curve of data going down,

960
00:41:41,620 --> 00:41:42,750
going up again.

961
00:41:42,750 --> 00:41:45,950
Just looking at it, we thought we have a ring.

962
00:41:45,950 --> 00:41:48,270
If that's true, we're really lucky.

963
00:41:48,270 --> 00:41:49,973
Oh my God, this worked.

964
00:41:51,520 --> 00:41:52,810
Once all the data

965
00:41:52,810 --> 00:41:55,310
from all the radio telescopes are collected,

966
00:41:55,310 --> 00:41:57,993
the process of creating an image can begin.

967
00:41:59,690 --> 00:42:01,360
And so what they do is they take the light

968
00:42:01,360 --> 00:42:04,040
that has been frozen at every one of these telescope sites

969
00:42:04,040 --> 00:42:05,800
and they play them back together,

970
00:42:05,800 --> 00:42:08,310
and they average it and average it down so much

971
00:42:08,310 --> 00:42:10,450
because there's only a tiny little signal

972
00:42:10,450 --> 00:42:12,220
riding on a huge amount of noise.

973
00:42:12,220 --> 00:42:14,150
You get a little nugget of information.

974
00:42:14,150 --> 00:42:16,010
It's passed onto the imaging algorithms.

975
00:42:16,010 --> 00:42:18,910
And that little nugget is what we use to make the picture.

976
00:42:20,220 --> 00:42:21,130
But the problem is,

977
00:42:21,130 --> 00:42:23,260
we're not collecting light from everywhere.

978
00:42:23,260 --> 00:42:24,810
There's a lot of holes now.

979
00:42:24,810 --> 00:42:27,510
And so the big challenge was taking that sparse

980
00:42:27,510 --> 00:42:29,700
and noisy data,

981
00:42:29,700 --> 00:42:31,690
and using it to recover an image.

982
00:42:31,690 --> 00:42:33,390
It's very similar to,

983
00:42:33,390 --> 00:42:35,820
if you're listening to a song being played on a piano

984
00:42:35,820 --> 00:42:37,450
that has a lot of broken keys.

985
00:42:37,450 --> 00:42:39,370
And even though a lot of the keys are broken,

986
00:42:39,370 --> 00:42:40,203
a lot of times,

987
00:42:40,203 --> 00:42:42,470
you can still try to make out what the song is.

988
00:42:42,470 --> 00:42:44,430
The problem is what we call (indistinct).

989
00:42:44,430 --> 00:42:46,550
There are many different kinds of images

990
00:42:46,550 --> 00:42:49,080
that correspond to the same data that we measure.

991
00:42:49,080 --> 00:42:51,570
And so we wanted to put all that aside and just say,

992
00:42:51,570 --> 00:42:54,450
ignoring all of our ideas of general relativity

993
00:42:54,450 --> 00:42:57,020
and all the ideas that we believe right now

994
00:42:57,020 --> 00:42:59,640
as far as what we think a black hole should look like,

995
00:42:59,640 --> 00:43:01,940
and just see, what is the data telling us?

996
00:43:01,940 --> 00:43:03,850
Does the data say that there should be a rig?

997
00:43:03,850 --> 00:43:04,683
How about a disk?

998
00:43:04,683 --> 00:43:06,290
How about, you know, an elephant?

999
00:43:11,252 --> 00:43:14,290
It would be very easy within a collaboration of this size

1000
00:43:14,290 --> 00:43:16,850
to have three different imaging techniques, for example,

1001
00:43:16,850 --> 00:43:19,560
and to decide that one of them was the way to go,

1002
00:43:19,560 --> 00:43:21,300
but that would have created a problem

1003
00:43:21,300 --> 00:43:23,240
because proponents of the other two methods,

1004
00:43:23,240 --> 00:43:25,220
which might be also very, very good,

1005
00:43:25,220 --> 00:43:26,720
would have felt left out.

1006
00:43:26,720 --> 00:43:28,780
So we adopted this method

1007
00:43:28,780 --> 00:43:31,600
of using all of these different techniques

1008
00:43:31,600 --> 00:43:33,170
as checks and balances.

1009
00:43:33,170 --> 00:43:35,360
We allowed everyone to proceed

1010
00:43:35,360 --> 00:43:37,380
with their particular algorithm,

1011
00:43:37,380 --> 00:43:40,280
their particular imaging method.

1012
00:43:40,280 --> 00:43:43,510
And we worked in isolation with our teams for seven weeks,

1013
00:43:43,510 --> 00:43:45,960
trying to make what we thought was the best image

1014
00:43:45,960 --> 00:43:47,230
from the data.

1015
00:43:47,230 --> 00:43:48,560
And after those seven weeks,

1016
00:43:48,560 --> 00:43:50,230
we actually all gathered together

1017
00:43:50,230 --> 00:43:51,720
in Cambridge, Massachusetts,

1018
00:43:51,720 --> 00:43:53,920
and we revealed those images to each other.

1019
00:43:53,920 --> 00:43:55,590
But no matter what,

1020
00:43:55,590 --> 00:43:56,500
even though the different teams

1021
00:43:56,500 --> 00:43:58,620
resulted in slightly different images,

1022
00:43:58,620 --> 00:44:01,200
the same underlying structure was there.

1023
00:44:01,200 --> 00:44:03,210
This ring of roughly 40 micro arcseconds

1024
00:44:03,210 --> 00:44:05,460
that was brighter on the bottom than the top.

1025
00:44:05,460 --> 00:44:08,470
But even at that point, we weren't sure.

1026
00:44:08,470 --> 00:44:11,040
And so what we did is then we spent the next couple months

1027
00:44:11,040 --> 00:44:13,430
essentially trying to break our images.

1028
00:44:13,430 --> 00:44:16,610
So we took the data and we trained our methods.

1029
00:44:16,610 --> 00:44:18,810
We figured out, what were the hyper parameters?

1030
00:44:18,810 --> 00:44:20,890
What were the knob settings of our methods

1031
00:44:20,890 --> 00:44:23,470
to recover things like disks instead?

1032
00:44:23,470 --> 00:44:25,380
So we'd generate a disk on the sky

1033
00:44:25,380 --> 00:44:27,690
as if the Event Horizon Telescope were seeing a disk

1034
00:44:27,690 --> 00:44:29,590
with no hole in the center.

1035
00:44:29,590 --> 00:44:31,680
And then we'd transfer those exact parameters

1036
00:44:31,680 --> 00:44:34,260
onto the real M87 black hole data.

1037
00:44:34,260 --> 00:44:35,940
And although we had tried our hardest

1038
00:44:35,940 --> 00:44:36,880
to find parameters

1039
00:44:36,880 --> 00:44:39,260
that would recover a disk with no hole in the center,

1040
00:44:39,260 --> 00:44:41,130
we saw that when we used those parameters

1041
00:44:41,130 --> 00:44:43,210
on the real black hole data,

1042
00:44:43,210 --> 00:44:45,330
the data forced us to put a hole there.

1043
00:44:45,330 --> 00:44:48,200
Although each individual image looks slightly different,

1044
00:44:48,200 --> 00:44:51,480
that ring structure is consistent across all of them.

1045
00:44:51,480 --> 00:44:52,900
That's when we knew

1046
00:44:52,900 --> 00:44:56,150
that we could then come with a real scientific publication

1047
00:44:56,150 --> 00:44:58,530
and a real press release to announce

1048
00:44:58,530 --> 00:45:00,823
that we'd seen the first image of a black hole.

1049
00:45:04,050 --> 00:45:06,890
The image had to be released all around the world

1050
00:45:06,890 --> 00:45:07,830
at the right moment.

1051
00:45:07,830 --> 00:45:11,100
It was all timed to the second.

1052
00:45:11,100 --> 00:45:14,193
And for that, Professor Heino Falcke is here.

1053
00:45:18,900 --> 00:45:21,600
We all knew in July of 2018 what we had.

1054
00:45:21,600 --> 00:45:25,640
Dr. Shep Doeleman, EHT's director.

1055
00:45:25,640 --> 00:45:28,870
And from that time until April of the following year,

1056
00:45:28,870 --> 00:45:30,660
nobody breathed a word of it.

1057
00:45:30,660 --> 00:45:33,000
{\an8}We all kept the results secret.

1058
00:45:33,000 --> 00:45:34,590
{\an8}Now, I have to fill the time actually

1059
00:45:34,590 --> 00:45:36,480
{\an8}until we are allowed to actually, you know,

1060
00:45:36,480 --> 00:45:38,070
start the unveilings.

1061
00:45:38,070 --> 00:45:39,710
Despite all the struggle,

1062
00:45:39,710 --> 00:45:41,280
all the exhaustion,

1063
00:45:41,280 --> 00:45:43,430
we'd kept it under the lid

1064
00:45:43,430 --> 00:45:46,448
until we were able to really release it.

1065
00:45:46,448 --> 00:45:49,130
And even up to the day we made the announcement,

1066
00:45:49,130 --> 00:45:51,050
everyone thought that we were going to say something

1067
00:45:51,050 --> 00:45:52,520
about Sagittarius A star,

1068
00:45:52,520 --> 00:45:55,160
{\an8}when in fact we had imaged M87.

1069
00:45:55,160 --> 00:45:58,080
{\an8}In April of 2017,

1070
00:45:58,080 --> 00:46:00,950
{\an8}all the dishes in the Event Horizon Telescope swiveled,

1071
00:46:00,950 --> 00:46:05,420
turned, and stared at a galaxy 55 million light years away.

1072
00:46:05,420 --> 00:46:07,763
It's called Messier 87 or M87.

1073
00:46:08,690 --> 00:46:11,750
And there's a super massive black hole at its core.

1074
00:46:11,750 --> 00:46:15,530
And we are delighted to be able to report to you today

1075
00:46:15,530 --> 00:46:19,260
that we have seen what we thought was unseeable.

1076
00:46:19,260 --> 00:46:23,293
We have seen and taken a picture of a black hole.

1077
00:46:24,460 --> 00:46:25,293
Here it is.

1078
00:46:28,320 --> 00:46:31,240
This is the first ever image of a black hole.

1079
00:46:38,300 --> 00:46:41,930
We all expected a lot of good reaction from the public,

1080
00:46:41,930 --> 00:46:44,640
but I think we're all extremely surprised

1081
00:46:44,640 --> 00:46:47,660
by how quickly it became a classic.

1082
00:46:47,660 --> 00:46:50,053
It became the iconic image of the black hole.

1083
00:46:52,190 --> 00:46:53,570
And this is the strongest evidence

1084
00:46:53,570 --> 00:46:56,653
that we have to date for the existence of black holes.

1085
00:46:58,360 --> 00:46:59,740
When I saw that picture,

1086
00:46:59,740 --> 00:47:03,000
I just thought that that was the most beautiful photo

1087
00:47:03,000 --> 00:47:04,003
I've ever seen.

1088
00:47:07,380 --> 00:47:10,450
I picked up the New York Times, as I do every morning,

1089
00:47:10,450 --> 00:47:12,960
and there was this beautiful picture of a black hole.

1090
00:47:15,050 --> 00:47:18,220
But I just didn't see it coming.

1091
00:47:18,220 --> 00:47:20,140
And then suddenly, there were these pictures,

1092
00:47:20,140 --> 00:47:21,140
and I was like, wow.

1093
00:47:29,850 --> 00:47:31,783
Nobody had ever seen a black hole.

1094
00:47:33,010 --> 00:47:34,793
At some point, seeing is believing.

1095
00:47:39,420 --> 00:47:41,910
Some people think of black holes as being frightening

1096
00:47:41,910 --> 00:47:43,340
and confusing objects,

1097
00:47:43,340 --> 00:47:44,640
but I don't.

1098
00:47:44,640 --> 00:47:45,770
I'm in love with them.

1099
00:47:45,770 --> 00:47:50,230
I have no problem cozying up to black holes

1100
00:47:50,230 --> 00:47:52,980
but for the simple reason that they are the one way

1101
00:47:52,980 --> 00:47:55,530
we'll be able to understand how gravity

1102
00:47:55,530 --> 00:48:00,530
and quantum mechanics ultimately have to join forces.

1103
00:48:01,330 --> 00:48:03,510
Physics is a terribly embarrassing field.

1104
00:48:03,510 --> 00:48:05,500
We've got two wonderful theories

1105
00:48:05,500 --> 00:48:06,960
and never the twain shall meet.

1106
00:48:06,960 --> 00:48:08,420
One works very well,

1107
00:48:08,420 --> 00:48:09,480
predicts almost anything

1108
00:48:09,480 --> 00:48:11,760
that you can do with short distances.

1109
00:48:11,760 --> 00:48:14,290
And the other one predicts almost anything we see

1110
00:48:14,290 --> 00:48:16,133
in relativistic astronomy.

1111
00:48:17,670 --> 00:48:18,670
Most of the time,

1112
00:48:18,670 --> 00:48:21,600
gravity is completely separate from quantum mechanics.

1113
00:48:21,600 --> 00:48:23,250
Gravity is so much weaker

1114
00:48:23,250 --> 00:48:26,000
than the quantum forces on the nuclear level.

1115
00:48:26,000 --> 00:48:28,440
The black hole is the one place where gravity

1116
00:48:28,440 --> 00:48:31,040
plays with all the other forces on an equal footing.

1117
00:48:32,277 --> 00:48:34,050
You're getting close to the singularity,

1118
00:48:34,050 --> 00:48:36,970
maybe you actually never get to the point

1119
00:48:36,970 --> 00:48:39,310
where you have an infinite density

1120
00:48:39,310 --> 00:48:41,410
because in quantum mechanics,

1121
00:48:41,410 --> 00:48:43,140
you can not have something which is more

1122
00:48:43,140 --> 00:48:45,180
because it will always have space-time

1123
00:48:45,180 --> 00:48:47,640
kind of fuzzy around that size.

1124
00:48:47,640 --> 00:48:50,540
But maybe what's happening there

1125
00:48:50,540 --> 00:48:54,250
have some effect at the level of the event horizon.

1126
00:48:54,250 --> 00:48:58,040
And that's where we can probe with gravitational waves

1127
00:48:58,040 --> 00:49:00,300
because when two black holes collide,

1128
00:49:00,300 --> 00:49:02,470
the two event horizons, they merge,

1129
00:49:02,470 --> 00:49:06,270
and they are very excited and are shedding a lot of energy.

1130
00:49:06,270 --> 00:49:08,570
The shape of the gravitational waves that come out

1131
00:49:08,570 --> 00:49:10,970
might carry a little bit of information

1132
00:49:10,970 --> 00:49:12,640
of what's going on inside.

1133
00:49:12,640 --> 00:49:13,473
Might.

1134
00:49:13,473 --> 00:49:16,863
We don't know, but maybe we will find out soon.

1135
00:49:17,860 --> 00:49:19,080
Einstein didn't think

1136
00:49:19,080 --> 00:49:21,690
we could detect gravitational waves,

1137
00:49:21,690 --> 00:49:24,670
and he didn't believe black holes existed at all,

1138
00:49:24,670 --> 00:49:27,410
even though they were born from his own theories.

1139
00:49:27,410 --> 00:49:30,460
Now, we know for sure that they do exist

1140
00:49:30,460 --> 00:49:34,710
and they may reveal the inner workings of the universe.

1141
00:49:34,710 --> 00:49:36,830
And that's why black holes draws

1142
00:49:36,830 --> 00:49:39,087
because they represent what we don't know

1143
00:49:39,087 --> 00:49:41,443
and they represent what we could know.

1144
00:49:45,060 --> 00:49:47,492
If I were to meet Einstein today,

1145
00:49:47,492 --> 00:49:51,260
I would tell him, "Hey, Albert, I'm sorry,

1146
00:49:51,260 --> 00:49:53,124
we proved you wrong."

1147
00:49:53,124 --> 00:49:56,707
(intense orchestral music)

1148
00:50:26,442 --> 00:50:29,942
(twinkling ambient music)

1149
00:50:30,937 --> 00:50:33,985
(soft orchestral music)