Inside the black hole image that made history Sheperd Doeleman
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)