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B1 Intermediate US 1024 Folder Collection
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Chris Anderson: Shep, thank you so much for coming.
I think your plane landed literally two hours ago in Vancouver.
Such a treat to have you.
So, talk us through how do you get from Einstein's equation to a black hole?
Sheperd Doeleman: Over 100 years ago,
Einstein came up with this geometric theory of gravity
which deforms space-time.
So, matter deforms space-time,
and then space-time tells matter in turn how to move around it.
And you can get enough matter into a small enough region
that it punctures space-time,
and that even light can't escape,
the force of gravity keeps even light inside.
CA: And so, before that, the reason the Earth moves around the Sun
is not because the Sun is pulling the Earth as we think,
but it's literally changed the shape of space
so that we just sort of fall around the Sun.
SD: Exactly, the geometry of space-time
tells the Earth how to move around the Sun.
You're almost seeing a black hole puncture through space-time,
and when it goes so deeply in,
then there's a point at which light orbits the black hole.
CA: And so that's, I guess, is what's happening here.
This is not an image,
this is a computer simulation of what we always thought,
like, the event horizon around the black hole.
SD: Until last week, we had no idea what a black hole really looked like.
The best we could do were simulations like this in supercomputers,
but even here you see this ring of light,
which is the orbit of photons.
That's where photons literally move around the black hole,
and around that is this hot gas that's drawn to the black hole,
and it's hot because of friction.
All this gas is trying to get into a very small volume, so it heats up.
CA: A few years ago, you embarked on this mission
to try and actually image one of these things.
And I guess you took --
you focused on this galaxy way out there.
Tell us about this galaxy.
SD: This is the galaxy --
we're going to zoom into the galaxy M87, it's 55 million light-years away.
CA: Fifty-five million.
SD: Which is a long way.
And at its heart,
there's a six-and-a-half-billion- solar-mass black hole.
That's hard for us to really fathom, right?
Six and a half billion suns compressed into a single point.
And it's governing some of the energetics of the center of this galaxy.
CA: But even though that thing is so huge, because it's so far away,
to actually dream of getting an image of it,
that's incredibly hard.
The resolution would be incredible that you need.
SD: Black holes are the smallest objects in the known universe.
But they have these outsize effects on whole galaxies.
But to see one,
you would need to build a telescope as large as the Earth,
because the black hole that we're looking at
gives off copious radio waves.
It's emitting all the time.
CA: And that's exactly what you did.
SD: Exactly. What you're seeing here
is we used telescopes all around the world,
we synchronized them perfectly with atomic clocks,
so they received the light waves from this black hole,
and then we stitched all of that data together to make an image.
CA: To do that
the weather had to be right
in all of those locations at the same time,
so you could actually get a clear view.
SD: We had to get lucky in a lot of different ways.
And sometimes, it's better to be lucky than good.
In this case, we were both, I like to think.
But light had to come from the black hole.
It had to come through intergalactic space,
through the Earth's atmosphere, where water vapor can absorb it,
and everything worked out perfectly,
the size of the Earth at that wavelength of light,
one millimeter wavelength,
was just right to resolve that black hole, 55 million light-years away.
The universe was telling us what to do.
CA: So you started capturing huge amounts of data.
I think this is like half the data from just one telescope.
SD: Yeah, this is one of the members of our team, Lindy Blackburn,
and he's sitting with half the data
recorded at the Large Millimeter Telescope,
which is atop a 15,000-foot mountain in Mexico.
And what he's holding there is about half a petabyte.
Which, to put it in terms that we might understand,
it's about 5,000 people's lifetime selfie budget.
(Laughter)
CA: It's a lot of data.
So this was all shipped, you couldn't send this over the internet.
All this data was shipped to one place
and the massive computer effort began to try and analyze it.
And you didn't really know
what you were going to see coming out of this.
SD: The way this technique works that we used --
imagine taking an optical mirror and smashing it
and putting all the shards in different places.
The way a normal mirror works
is the light rays bounce off the surface, which is perfect,
and they focus in a certain point at the same time.
We take all these recordings,
and with atomic clock precision
we align them perfectly, later in a supercomputer.
And we recreate kind of an Earth-sized lens.
And the only way to do that is to bring the data back by plane.
You can't beat the bandwidth of a 747 filled with hard discs.
(Laughter)
CA: And so, I guess a few weeks or a few months ago,
on a computer screen somewhere,
this started to come into view.
This moment.
SD: Well, it took a long time.
CA: I mean, look at this.
That was it.
That was the first image.
(Applause)
So tell us what we're really looking at there.
SD: I still love it.
(Laughter)
So what you're seeing is that last orbit of photons.
You're seeing Einstein's geometry laid bare.
The puncture in space-time is so deep
that light moves around in orbit,
so that light behind the black hole, as I think we'll see soon,
moves around and comes to us on these parallel lines
at exactly that orbit.
It turns out, that orbit is the square root of 27
times just a handful of fundamental constants.
It's extraordinary when you think about it.
CA: When ...
In my head, initially, when I thought of black holes,
I'm thinking that is the event horizon,
there's lots of matter and light whirling around in that shape.
But it's actually more complicated than that.
Well, talk us through this animation, because it's light being lensed around it.
SD: You'll see here that some light from behind it gets lensed,
and some light does a loop-the-loop around the entire orbit of the black hole.
But when you get enough light
from all this hot gas swirling around the black hole,
then you wind up seeing all of these light rays
come together on this screen,
which is a stand-in for where you and I are.
And you see the definition of this ring begin to come into shape.
And that's what Einstein predicted over 100 years ago.
CA: Yeah, that is amazing.
So tell us more about what we're actually looking at here.
First of all, why is part of it brighter than the rest?
SD: So what's happening is that the black hole is spinning.
And you wind up with some of the gas moving towards us below
and receding from us on the top.
And just as the train whistle has a higher pitch
when it's coming towards you,
there's more energy from the gas coming towards us than going away from us.
You see the bottom part brighter
because the light is actually being boosted in our direction.
CA: And how physically big is that?
SD: Our entire solar system would fit well within that dark region.
And if I may,
that dark region is the signature of the event horizon.
The reason we don't see light from there,
is that the light that would come to us from that place
was swallowed by the event horizon.
So that -- that's it.
CA: And so when we think of a black hole,
you think of these huge rays jetting out of it,
which are pointed directly in our direction.
Why don't we see them?
SD: This is a very powerful black hole.
Not by universal standards, it's still powerful,
and from the north and south poles of this black hole
we think that jets are coming.
Now, we're too close to really see all the jet structure,
but it's the base of those jets that are illuminating the space-time.
And that's what's being bent around the black hole.
CA: And if you were in a spaceship whirling around that thing somehow,
how long would it take to actually go around it?
SD: First, I would give anything to be in that spaceship.
(Laughter)
Sign me up.
There's something called the -- if I can get wonky for one moment --
the innermost stable circular orbit,
that's the innermost orbit at which matter can move around a black hole
before it spirals in.
And for this black hole, it's going to be between three days and about a month.
CA: It's so powerful, it's weirdly slow at one level.
I mean, you wouldn't even notice
falling into that event horizon if you were there.
SD: So you may have heard of \"spaghettification,\"
where you fall into a black hole
and the gravitational field on your feet is much stronger than on your head,
so you're ripped apart.
This black hole is so big
that you're not going to become a spaghetti noodle.
You're just going to drift right through that event horizon.
CA: So, it's like a giant tornado.
When Dorothy was whipped by a tornado, she ended up in Oz.
Where do you end up if you fall into a black hole?
(Laughter)
SD: Vancouver.
(Laughter)
CA: Oh, my God.
(Applause)
It's the red circle, that's terrifying.
No, really.
SD: Black holes really are the central mystery of our age,
because that's where the quantum world and the gravitational world come together.
What's inside is a singularity.
And that's where all the forces become unified,
because gravity finally is strong enough to compete with all the other forces.
But it's hidden from us,
the universe has cloaked it in the ultimate invisibility cloak.
So we don't know what happens in there.
CA: So there's a smaller one of these in our own galaxy.
Can we go back to our own beautiful galaxy?
This is the Milky Way, this is home.
And somewhere in the middle of that there's another one,
which you're trying to find as well.
SD: We already know it's there, and we've already taken data on it.
And we're working on those data right now.
So we hope to have something in the near future, I can't say when.
CA: It's way closer but also a lot smaller,
maybe the similar kind of size to what we saw?
SD: Right. So it turns out that the black hole in M87,
that we saw before,
is six and a half billion solar masses.
But it's so far away that it appears a certain size.
The black hole in the center of our galaxy is a thousand times less massive,
but also a thousand times closer.
So it looks the same angular size on the sky.
CA: Finally, I guess, a nod to a remarkable group of people.
Who are these guys?
SD: So these are only some of the team.
We marveled at the resonance that this image has had.
If you told me that it would be above the fold in all of these newspapers,
I'm not sure I would have believed you, but it was.
Because this is a great mystery,
and it's inspiring for us, and I hope it's inspiring to everyone.
But the more important thing is that this is just a small number of the team.
We're 200 people strong with 60 institutes
and 20 countries and regions.
If you want to build a global telescope you need a global team.
And this technique that we use of linking telescopes around the world
kind of effortlessly sidesteps some of the issues that divide us.
And as scientists, we naturally come together to do something like this.
CA: Wow, boy, that's inspiring for our whole team this week.
Shep, thank you so much for what you did and for coming here.
SD: Thank you.
(Applause)
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B1 Intermediate US

【TED】Sheperd Doeleman: Inside the black hole image that made history (Inside the black hole image that made history | Sheperd Doeleman)

1024 Folder Collection
林宜悉 published on May 10, 2019

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