JUDY WOODRUFF: Unlikely as it sounds, we now have an image of that invisible space anomaly,
a black hole, a cosmic abyss with gravity of such intensity that nothing, not even light,
escapes it.
A team of astronomers made the image public at a press conference in Washington, D.C.,
this morning.
We start our report tonight with this background video from the World Science Festival and
voiced by its co-founder, Brian Greene.
He's professor of physics at Columbia University.
It's the latest in our weekly science and technology series, the Leading Edge.
BRIAN GREENE, Columbia University: About 100 years ago, Albert Einstein gave us a new description
of the force of gravity, in which gravity exerts its influence through warps and curves
in the fabric of space and time.
Just a couple of years later, Karl Schwarzschild -- he was a German astronomer -- who was stationed
on the Russian front during World War I and charged with tackling artillery trajectories,
he somehow gets ahold of Einstein's manuscript and realizes something amazing.
If you take a spherical object and you squeeze it down to a sufficiently small size, according
to Einstein's math, the gravitational pull will be so enormous, that nothing will be
able to escape, not even light.
And that is what we mean by a black hole.
Now, when Einstein caught wind of these results, he didn't believe it.
He didn't think that these objects would actually be out there in the universe.
And yet, in the ensuing decades, theoretical developments began to mount showing that black
holes were the inevitable outcome of massive stars that had used up their nuclear fuel,
undergone a supernova explosion, and the resulting core would have no ability to withstand the
pull of gravity, and would collapse down into a black hole.
And the observational case had also began to mount.
Studies of the center of our Milky Way galaxy showed stars whipping around the center at
such enormous speeds, that the only explanation for the object that could exert the powerful
gravity responsible for that motion would be a very massive black hole, perhaps four
million times the mass of the sun.
And perhaps the most convincing observational evidence to date actually comes from gravitational
waves.
When we received the first ripples in the fabric of space back in 2015, the only explanation
for the pattern of those waves was two black holes very distant that collided, setting
off this tidal wave in space that we were able to detect.
JUDY WOODRUFF: And Brian Greene of Columbia University joins us now.
So, tell us.
It's clear from what you just were reporting scientists have known about black holes, suspected
about black holes for a long time.
What does it mean that we now have an actual photograph of one?
BRIAN GREENE: Well, now we know for the first time that they are actually real, that Einstein's
mathematics described a real monster that exists out there in the universe, where mass
is crushed at such a fantastically small size, that the gravitational pull exceeds anything
that we have ever encountered anywhere else in the universe.
So it is a wonderful moment of confirmation.
JUDY WOODRUFF: So let's look at that picture again, the black center and the red and yellow
circle, if you would, and tell us what we're looking at here.
BRIAN GREENE: Yes, so the center is the blackness, the black hole.
That's where the name comes from.
And the light that you see around the edge of the black hole, that is light that is emitted
by hot gas as it swirls around the black hole, and just before it falls over the edge into
the abyss, it emits light that is able to swirl around and ultimately reach us.
Now, you're looking at a black hole that is 53 million light-years away in a galaxy called
M-87.
So that reddish-orange light has been traveling toward us for about 53 million years.
And yet this wonderful team of astronomers has been able to capture those photons and
recreate the image, recreate the environment from which they originated their journey.
JUDY WOODRUFF: So now that the scientists, the astronomers have this image, what do they
do next?
What are the next questions about a black hole?
BRIAN GREENE: Well, there are so many questions.
But, briefly, we really want to understand, what happens when something falls over the
edge of a black hole?
Einstein gave us one story, but it didn't take into account quantum physics.
So the next step of the journey is to really understand how the laws of the small quantum
mechanics meld with Einstein's law of the big, his general theory of relativity.
And these kinds of images may take us the next step toward finally understanding how
to marry those two theories together.
JUDY WOODRUFF: Does this change what children will learn in elementary school about space?
BRIAN GREENE: One day, I think it absolutely might, because gravity is the most important
force governing the largest things in the universe.
And when we can finally take images of gravity in the most extreme environments, those are
the environments we theorists love.
Those are the laboratories where can push our theories to the limit.
And when we can finally take imagery in those domains, it ultimately will probably find
its way into the textbooks.
JUDY WOODRUFF: And remind us again, how close to Earth is the nearest black hole?
BRIAN GREENE: Well, we know of one in the center of our Milky Way galaxy, which is 26,000
light-years away.
So it's not as though these things are right next door.
But it's wondrous that we can build machines that can take a photograph as if they were
nearby.
I mean, how amazing is it that the black hole that was 53 million light-years away looks
like it's something that is right out there that you could touch?
JUDY WOODRUFF: And, finally, when people hear, read about something that can suck everything
around it into it because of the powerful forces of gravity, do people on Earth have
anything to be afraid of when it comes to a black hole?
BRIAN GREENE: Oh, well, it's a natural thought.
No, we have nothing really to be afraid of.
These are just wonderful laboratories in which we can push our understanding.
In fact, I would turn it around.
You know, we live in this fractured world.
And how wondrous is it that 100 scientists on four continents using eight radio telescopes,
that their work now allows every citizen on planet Earth to look up and recognize that
there are these deep, fundamental truths that transcend everything that divides us?
To me, that is the real message of this breakthrough.
JUDY WOODRUFF: That's a wonderful way to look at it.
Brian Greene, thank you very much, Columbia University.
We appreciate it.
BRIAN GREENE: Thank you.