-
So, in the movie "Interstellar,"
-
we get an up-close look
at a supermassive black hole.
-
Set against a backdrop of bright gas,
-
the black hole's massive
gravitational pull
-
bends light into a ring.
-
However, this isn't a real photograph,
-
but a computer graphic rendering --
-
an artistic interpretation of what
a black hole might look like.
-
100 years ago,
-
Albert Einstein first published
his theory of genral relativity.
-
In the years since then,
-
scientists have provided a lot
of evidence in support of it.
-
But one thing predicted
from this theory --
-
black holes --
-
still have not been directly observed.
-
Although we have some idea
as to what a black hole might look like,
-
we've never actually taken
a picture of one before.
-
However, you might be surprised to know
that that may soon change.
-
We may be seeing our first picture
of a black hole in the next couple years.
-
Getting this first picture will come down
to an international team of scientists,
-
and Earth-sized telescope
-
and an algorithm that puts
together the final picture.
-
Although I won't be able to show you
a real picture of a black hold today,
-
I'd like to give you a brief glimpse
into the effort involved
-
in getting that first picture.
-
So, my name's Katie Bouman,
-
and I'm a PhD student at MIT.
-
I do research in a computer science lab
-
that works on making computers see
through images and video.
-
But although I'm not an astronomer,
-
today I'd like to show you
-
how I've been able to contribute
to this exciting project.
-
If you go out past the bright city lights,
-
you may just be lucky enough to see
a stunning view of the Milky Way Galaxy.
-
And if you could zoom past
millions of stars,
-
26,000 lightyears toward the heart
of the spiraling Milky Way,
-
we'd eventually reach a cluster
of stars right at the center.
-
Peering past all the galactic dust
with infrared telescopes,
-
astronomers have watched these stars
for over 16 years.
-
But it's what they don't see
that is the most spectactular.
-
These stars seem to orbit
an invisible object.
-
By tracking the paths of these stars,
-
astronomers have concluded
-
that the only thing small
and heavy enough to cause this motion
-
is a super-massive blackhole.
-
An object so dense that it sucks up
anything that ventures too close --
-
even light.
-
But what happens if you were
to zoom in even further?
-
Is it possible to see something
that by definition isn't possible to see?
-
Well, it turns out that if you were
to zoom in at radio wave lengths,
-
we expect to see a ring of light
-
caused by the gravitational lensing of hot
plasma zipping around the black hole.
-
In other words,
-
the black hole casts a shadow
on this backdrop of bright material,
-
carving out a sphere of darkness.
-
This bright ring reveals
the black hole's event horizon,
-
where the gravitational pull
becomes so great
-
that not even light can escape.
-
Einstein's equations predict
the size and shape of this ring,
-
so taking a picture of it
wouldn't only be really cool,
-
it'd also help to verify
that these equations hold
-
in the extreme conditions
around the black hole.
-
However, this black hole
is so far away from us,
-
so from Earth,
-
this ring appears incredibly small --
-
the same size to us as an orange
on the surface of the moon.
-
That makes taking a picture of it
extremely difficult.
-
Why is that?
-
Well, it all comes down
to a simple equation.
-
Do to a phenomenon called the fraction,
-
there are fundamental limits
-
to the smallest objects
that we can possibly see.
-
This governing equation says
-
that in order to see smaller and smaller,
-
we need to make our telescope
bigger and bigger.
-
But even with the most powerful
optical telescopes here on Earth,
-
we can't even get close
to the resolution necessary
-
to image on the surface of the moon.
-
Not Synced
In fact, here I show one of the highest
resolution images ever taken
-
Not Synced
of the moon from Earth.
-
Not Synced
It contains roughly 13,000 pixels,
-
Not Synced
and yet each pixel will contain
over 1.5 million oranges.
-
Not Synced
So how big of a telescope do we need
-
Not Synced
in order to see an orange
on the surface of the moon,
-
Not Synced
and by extension, our black hole?
-
Not Synced
It turns out that by
crunching the numbers,
-
Not Synced
you can easily calculate that we
would need a telescope
-
Not Synced
the size of the entire Earth.
-
Not Synced
(Laughter)
-
Not Synced
And if we could build this
Earth-sized telescope,
-
Not Synced
we could just start to make out
that distinctive ring of light
-
Not Synced
indicative of the black hole's
event horizon.
-
Not Synced
Although this picture wouldn't
contain all the detail
-
Not Synced
that we get to see
in computer graphic renderings,
-
Not Synced
it would allow us to safely
get our first glimpse
-
Not Synced
of the immediate environment
around a black hole.
-
Not Synced
However, as you can imagine,
-
Not Synced
building a single dish telescope
the size of the Earth is impossible.
-
Not Synced
But in the famous words of Mick Jagger,
-
Not Synced
"You can't always get what you want,
-
Not Synced
but if you try sometimes,
-
Not Synced
you might just find
-
Not Synced
that you get what you need."
-
Not Synced
And by connecting telescopes
from around the world,
-
Not Synced
an international collaboration
called The Event Horizon Telescope,
-
Not Synced
is creating a computational telescope
the size of the Earth,
-
Not Synced
capable of resolving structure
-
Not Synced
on the scale of a black hole's
event horizon.
-
Not Synced
This network of telescopes is scheduled
-
Not Synced
to take its very first picture
of a black hole just next year.
-
Not Synced
Each telescope in the worldwide
network works together.
-
Not Synced
Linked through the precise timing
of atomic clocks,
-
Not Synced
teams of researchers at each
of the sights freeze light
-
Not Synced
by collecting thousands
of terabytes of data.
-
Not Synced
This data is then processed in a lab
right here in Massachussetts.
-
Not Synced
So how does this even work?
-
Not Synced
Remember if we want to see the black hole
in the center of our galaxy
-
Not Synced
we need to build this impossibly large
Earth-sized telescope?
-
Not Synced
For just a second,
-
Not Synced
let's pretend we could build a telescope
the size of the Earth.
-
Not Synced
This is would a little bit like
-
Not Synced
turning the Earth into
a giant spinning disco ball.
-
Not Synced
Each individual mirror would collect light
-
Not Synced
that we could then combine
together to make a picture.
-
Not Synced
However, now it's [time to]
remove most of those mirrors
-
Not Synced
so only a few remained.
-
Not Synced
We could still try to combine
this information together,
-
Not Synced
but now there are a lot of holes.
-
Not Synced
These remaining mirrors represent
the locations where we have telescopes.
-
Not Synced
This is an incredibly small number
of measurements to make a picture from.
-
Not Synced
But although we only collect light
at a few telescope locations,
-
Not Synced
as the Earth rotates,
-
Not Synced
we get to see other new measurements.
-
Not Synced
In other words,
-
Not Synced
as the disco ball spins,
-
Not Synced
those mirrors change locations
-
Not Synced
and we get to observe different
parts of the image.
-
Not Synced
The imaging algorithms we develop
fill in the gaps in the disco ball
-
Not Synced
in order to reconstruct
the underlying black hole image.
-
Not Synced
If we had telescopes located
everywhere on the globe --
-
Not Synced
in other words, the entire disco ball --
-
Not Synced
this would be trvial.
-
Not Synced
However, we only see a few samples,
-
Not Synced
and for that reason,
-
Not Synced
there are an infinite number
of possible images
-
Not Synced
that are perfectly consistent
with our telescope measurements.
-
Not Synced
However, not all images are created equal.
-
Not Synced
Some of those images look more like
what we think of as images than others.
-
Not Synced
And so my role in helping to take
the first image of a black hole
-
Not Synced
is to design algorithms that find
the most reasonable image
-
Not Synced
that also fits the telescope measurements.
-
Not Synced
Just as a forensic sketch artist
uses limited descriptions
-
Not Synced
to piece together a picture using
his knowledge of face structure,
-
Not Synced
the imaging algorithms I develop
use our limited telescope data
-
Not Synced
to guide us to a picture that also
looks like stuff in our universe.
-
Not Synced
Using these algorithms,
-
Not Synced
we're able to piece pictures
from this sparse, noisy data.
-
Not Synced
So here I show a sample reconstruction
done using simulated data
-
Not Synced
where we pretend to point our telescopes
-
Not Synced
to the black hole in the center
of our galaxy.
-
Not Synced
Although this is just a simulation,
-
Not Synced
reconstructions such as this
give us hope
-
Not Synced
that we'll soon be able to reliably
take the first image of a black hole,
-
Not Synced
and from it determine
the size of its ring.
-
Not Synced
Although I'd love to go on about
all the details of this algorithm,
-
Not Synced
luckily for you, I don't have the time.
-
Not Synced
(Laughter)
-
Not Synced
But I'd still like
to give you a brief idea
-
Not Synced
of how we define what
our universe looks like,
-
Not Synced
and how we use this to reconstruct
and verify our results.
-
Not Synced
Since there are an infinite number
of possible images
-
Not Synced
that perfectly explain
our telescope measurements,
-
Not Synced
we have to choose
between them in some way.
-
Not Synced
We do this by ranking the images
-
Not Synced
based on how likely they are
to be the black hole image,
-
Not Synced
and then choosing the one
that's most likely.
-
Not Synced
So what do I mean by this exactly?
-
Not Synced
Let's say we were trying to make a model
-
Not Synced
that told us how likely an image
were to appear on Facebook.
-
Not Synced
We'd probably want the model to say
-
Not Synced
that it's pretty unlikely that someone
would post this noise image on the left,
-
Not Synced
and it's pretty likely that someone would
post a selfie like this one on the right.
-
Not Synced
The image in the middle is blurry,
-
Not Synced
so even though it's more likely
that we'd see it on Facebook
-
Not Synced
compared to the noise image,
-
Not Synced
it's probable less likely when you see it
compared to the selfie.
-
Not Synced
But when it comes to images
from the black hole,
-
Not Synced
we're posed with a real conundrum.
-
Not Synced
We've never seen a black hole before.
-
Not Synced
In that case,
-
Not Synced
what is a likely black hole image,
-
Not Synced
and what should we assume
about the structure of black holes?
-
Not Synced
We could try to use images
from simulations we've done,
-
Not Synced
like the image of the black hole
from "Interstellar,"
-
Not Synced
but if we did this,
-
Not Synced
it could cause some serious problems.
-
Not Synced
What would happen if Einstein's
theories didn't hold?
-
Not Synced
We'd still want to reconstruct an accurate
picture of what was going on.
-
Not Synced
If we bake Einstein's equations
too much into our algorithms,
-
Not Synced
we'll just end up seeing what
we expect to see.
-
Not Synced
In other words,
-
Not Synced
we want to leave the option open
-
Not Synced
for there being a giant elephant
at the center of our galaxy.
-
Not Synced
(Laughter)
-
Not Synced
Different types of images have
very distinct features.
-
Not Synced
We can easily tell the difference between
black hole simulation images
-
Not Synced
and images we take
every day here on Earth.
-
Not Synced
We need a way to tell our algorithms
what images look like
-
Not Synced
without imposing one type
of image's features too much.
-
Not Synced
One way we can try to get aroun this
-
Not Synced
is by imposing the features
of different kinds of images
-
Not Synced
and seeing how the type of image
we assume effects our reconstructions.
-
Not Synced
If all image's types produce
a very similar looking image,
-
Not Synced
then we can start to become more confident
-
Not Synced
that the image assumptions we're making
are not biasing this picture that much.
-
Not Synced
This is a little bit like
giving the same description
-
Not Synced
to three different sketch artists
from all around the world.
-
Not Synced
If they all produce
a very similar looking face,
-
Not Synced
then we can start to become confident
-
Not Synced
that they're not imposing their own
cultural biases on the drawings.
-
Not Synced
One way we can try to impose
different imaging features
-
Not Synced
is by using pieces of existing images.
-
Not Synced
So we take a large collection of images,
-
Not Synced
and we break them down into
their little image patches.
-
Not Synced
We then can treat each image patch
a little bit like pieces of a puzzle.
-
Not Synced
And we use commonly seen puzzle pieces
to piece together and image
-
Not Synced
that also fits our telescope measurements.
-
Not Synced
Different types of images have very
distinctive sets of puzzle pieces.
-
Not Synced
So what happens when we take the same data
but we use different sets of puzzle pieces
-
Not Synced
to reconstruct the image?
-
Not Synced
Let's first start with black hole
simulation puzzle pieces.
-
Not Synced
OK, this looks reasonable.
-
Not Synced
This looks like what we expect
a black hole to look like,
-
Not Synced
but did we just get it
-
Not Synced
because we just fed it little pieces
of black hole simulation images?
-
Not Synced
Let's try another set of puzzle pieces
from astronomical, non-black hole objects.
-
Not Synced
from astronomical, non-black hole objects.
-
Not Synced
OK, we get a similar looking image.
-
Not Synced
And then how about pieces
from everyday images,
-
Not Synced
like the images you take with
your own personal camera?
-
Not Synced
Great, we see the same image.
-
Not Synced
When we get the same image from
all different sets of puzzle pieces,
-
Not Synced
then we can start to become more confident
-
Not Synced
that the image assumptions we're making
-
Not Synced
aren't biasing the final
image we get too much.
-
Not Synced
Another thing we can do is take
the same set of puzzle pieces,
-
Not Synced
such as the ones derived
from everyday images,
-
Not Synced
and use it to reconstruct many
different kinds of source images.
-
Not Synced
So in our simulations,
-
Not Synced
we pretend a black hole looks like
astronomical non-black hole objects
-
Not Synced
as well as everyday images like
the elephant in the center of our galaxy.
-
Not Synced
When the results of our algorithms
on the bottom look very similar
-
Not Synced
to the simulation's truth image on top,
-
Not Synced
then we can start to become
more confident in our algorithms.
-
Not Synced
And I just really want to emphasize here
-
Not Synced
that all of these pictures were created
-
Not Synced
by piecing together little pieces
of everyday photographs,
-
Not Synced
like you take with your
own personal camera.
-
Not Synced
So an image of a black hole
we've never seen before
-
Not Synced
may be eventually created by piecing
together pictures that we see all the time
-
Not Synced
of people, buildings, trees cats and dogs.
-
Not Synced
Imaging ideas like this
will make it possible
-
Not Synced
for us to take our very first
pictures of a black hole,
-
Not Synced
and hopefully verify those famous theories
-
Not Synced
for which scientists rely
on a daily basis.
-
Not Synced
But of course getting imaging ideas
like this working
-
Not Synced
would never have been possible
without the amazing team of researchers
-
Not Synced
that I have the privilege to work with.
-
Not Synced
It still amazes me
-
Not Synced
that although I began this project
with no background in astrophysics,
-
Not Synced
what we have achieved
through this unique collaboration
-
Not Synced
could result in the very first
images of a black hole.
-
Not Synced
But big projects like
the Event Horizon Telescope
-
Not Synced
are successful due to all
the interdisciplinary expertise
-
Not Synced
different people bring to the table.
-
Not Synced
We're a melting pot of astronomers,
-
Not Synced
physicists, mathematicians and engineers.
-
Not Synced
This is what will make it soon possible
-
Not Synced
to achieve something
once thought impossible.
-
Not Synced
I'd like to encourage all of you to go out
-
Not Synced
and help push the boundaries of science,
-
Not Synced
even if it may at first seem as mysterious
to you as a black hole.
-
Not Synced
Thank you.
-
Not Synced
(Applause)