Scientists work on the boundaries of the unknown, where every new piece of knowledge forms a path into a void of uncertainty.
And nothing is more uncertain– or potentially enlightening– than a paradox.
Throughout history, paradoxes have threatened to undermine everything we know, and just as often, they’ve reshaped our understanding of the world.
Today, one of the biggest paradoxes in the universe threatens to unravel the fields of general relativity and quantum mechanics: the black hole information paradox.
To understand this paradox, we first need to define what we mean by "information."
Typically, the information we talk about is visible to the naked eye.
For example, this kind of information tells us that an apple is red, round, and shiny.
But physicists are more concerned with quantum information.
This refers to the quantum properties of all the particles that make up that apple, such as their position, velocity and spin.
Every object in the universe is composed of particles with unique quantum properties.
This idea is evoked most significantly in a vital law of physics: the total amount of quantum information in the Universe must be conserved.
Even if you destroy an object beyond recognition, its quantum information is never permanently deleted.
And theoretically, knowledge of that information would allow us to recreate the object from its particle components.
Conservation of information isn’t just an arbitrary rule, but a mathematical necessity, upon which much of modern science is built.
But around black holes, those foundations get shaken.
When an apple enters a black hole, it seems as though it leaves the universe, and all its quantum information becomes irretrievably lost.
However, this doesn’t immediately break the laws of physics.
The information is out of sight, but it might still exist within the black hole’s mysterious void.
Alternatively, some theories suggest that information doesn’t even make it inside the black goldenmary@example.net.
Seen from outside, it’s as if the apple’s quantum information is encoded on the surface layer of the black hole, called the event horizon.
As the black hole’s mass increases, the surface of the event horizon increases as well.
So it’s possible that as a black hole swallows an object, it also grows large enough to conserve the object’s quantum information.
But whether information is conserved inside the black hole or on its surface, the laws of physics remain intact– until you account for Hawking Radiation.
Discovered by Stephen Hawking in 1974, this phenomenon shows that black holes are gradually evaporating.
Over incredibly long periods of time black holes lose mass as they shed particles away from their event horizons.
Critically, it seems as though the evaporating particles are unrelated to the information the black hole encodes– suggesting that a black hole and all the quantum information it contains could be completely erased.
Does that quantum information truly disappear?
If not, where does it go?
While the evaporation process would take an incredibly long time, the questions it raises for physics are far more urgent.
The destruction of information would force us to rewrite some of our most fundamental scientific paradigms.
But fortunately, in science, every paradox is an opportunity for new discoveries.
Researchers are investigating a broad range of possible solutions to the Information Paradox.
Some have theorized that information actually is encoded in the escaping radiation, in some way we can’t yet understand.
Others have suggested the paradox is just a misunderstanding of how general relativity and quantum field theory interact.
Respectively, these two theories describe the largest and smallest physical phenomena, and they’re notoriously difficult to combine.
Some researchers argue that a solution to this and many other paradoxes will come naturally with a “unified theory of everything.”
But perhaps the most mind-bending theory to come from exploring this paradox is the holographic principle.
Expanding on the idea that the 2D surface of an event horizon can store quantum information, this principle suggests that the very boundary of the observable universe is also a 2D surface encoded with information about real, 3D objects.
If this is true, it’s possible that reality as we know it is just a holographic projection of that information.
If proven, any of these theories would open up new questions to explore, while still preserving our current models of the universe.
But it’s also possible that those models are wrong!
Either way, this paradox has already helped us take another step into the unknown.
♫ Jill Sobule: At a conference in Monterey by the big, big jellyfish tank, ♫ ♫ I first saw you and I got so shy. ♫ ♫ You see, I was a little paranoid 'cause I might have been high. ♫ ♫ And I hadn't done that in ages and I won't do that again. ♫ ♫ But that's another story. ♫ ♫ Loved you forever and I've been a big fan, ♫ ♫ the one-woman shows, I even rented "Pat." ♫ ♫ I got enough nerve to come up to you, ♫ ♫ but little did I know one year later we'd be doing this show. ♫ ♫ I sing.
Julia Sweeney: I tell stories.
Together: The Jill and Julia Show. ♫ ♫ Sobule: Sometimes it works.
Sweeney: Sometimes it doesn't. ♫ ♫ Together: The Jill and Julia Show. ♫ ♫ Sweeney: At a conference in Monterey next to the big, big jellyfish tank, ♫ ♫ I first saw you and I wasn't so shy. ♫ I made a beeline for you and told you what a huge fan I was ever since I was writing that pilot for Fox, and Wendy and I wanted you to do the theme song.
And then the pilot didn't go and I was so sad, but I kept remaining a fan of yours.
And then when I went through that big, horrible breakup with Carl and I couldn't get off the couch, I listened to your song, ♫ "Now That I Don't Have You," ♫ over and over and over and over again.
And I can't believe you're here and that I'm meeting you goldenmary@example.net.
And also, I can't believe that we're eating sushi in front of the fish tank, which, personally, I think is really inappropriate.
(Laughter) (Applause) And little did I know that one year later ... ♫ we'd be doing this show. ♫ ♫ Sobule: I sing.
Sweeney: I tell stories.
Together: The Jill and Julia Show. ♫ Sobule: Hey, they asked us back!
Sweeney: Can you stand it?!
♫ Together: The Jill and Julia, the Jill and Julia, the Jill and Julia Show. ♫ ♫ Sobule: Why are all our heroes so imperfect? ♫ ♫ Why do they always bring me down? ♫ ♫ Why are all our heroes so imperfect? ♫ ♫ Statue in the park has lost his crown. ♫ ♫ William Faulkner, drunk and depressed. ♫ Sweeney: Mmm.
♫ Dorothy Parker, mean, drunk and depressed. ♫ Sweeney: I know.
♫ And that guy, "Seven Years in Tibet," turned out to be a Nazi. ♫ Sweeney: Yeah.
♫ Founding fathers all had slaves. ♫ Sweeney: I know.
♫ The explorers slaughtered the braves. ♫ Sweeney: Horribly.
♫ Sobule: The Old Testament God can be so petty. ♫ Sweeney: Don't get me started on that.
(Laughter) ♫ Sobule: Paul McCartney, jealous of John, even more so now that he's gone. ♫ ♫ Dylan was so mean to Donovan in that movie. ♫ ♫ Pablo Picasso, cruel to his wives. ♫ Sweeney: Horrible.
♫ Sobule: My favorite poets took their own lives. ♫ ♫ Orson Welles peaked at twenty-five, below before our eyes. ♫ ♫ And he sold bad wine. ♫ ♫ Together: Why are all our heroes so imperfect?
Yeah ♫ ♫ Why do they always bring me down? ♫ ♫ Sobule: Heard Babe Ruth was full of malice. ♫ Sweeney: Oh.
♫ Lewis Carroll I'm sure did Alice. ♫ Sweeney: What?!
♫ Plato in the cave with those very young boys. ♫ Sweeney: Ooh...
♫ Sobule: Hillary supported the war. ♫ ♫ Sweeney: Even Thomas Friedman supported the war. ♫ (Laughter) ♫ Sobule: Colin Powell turned out to be ...
Together: ... such a pussy. ♫ (Laughter) (Applause) ♫ Sobule: William Faulkner, drunk and depressed, ♫ ♫ Tennessee Williams, drunk and depressed. ♫ Sweeney: Yeah.
♫ Sobule: Take it, Julia. ♫ Sweeney: Okay.
Oprah was never necessarily a big hero of mine.
I mean, I watch Oprah mostly when I'm home in Spokane visiting my mother.
And to my mother, Oprah is a greater moral authority than the Pope, which is actually saying something because she's a devout Catholic.
Anyway, I like Oprah -- I like her girlfriendy-ness, I like her weight issues, I like how she's transformed talk television, I like how she's brought reading back to America -- but there was something that happened the last two weeks that was ...
I call it the Soon-Yi moment: it is the moment when I cannot continue supporting someone.
And that was that she did two entire shows promoting that movie "The Secret."
Do you guys know about that movie "The Secret"?
It makes "What the Bleep Do We Know" seem like a doctoral dissertation from Harvard on quantum mechanics -- that's how bad it is.
It makes "The DaVinci Code" seem like "War and Peace."
That movie is so horrible.
It promotes such awful pseudoscience.
And the basic idea is that there's this law of attraction, and your thoughts have this vibrating energy that goes out into the universe and then you attract good things to happen to you.
On a scientific basis, it's more than just "Power of Positive Thinking" -- it has a horrible, horrible dark side.
Like if you get ill, it's because you've just been thinking negative thoughts.
Yeah, stuff like that was in the movie and she's promoting it.
And all I'm saying is that I really wish that Murray Gell-Mann would go on Oprah and just explain to her that the law of attraction is, in fact, not a law.
So that's what I have to say.
(Laughter) (Applause) ♫ Sobule: I sing.
Sweeney: I tell stories.
Together: The Jill and Julia Show. ♫ ♫ Sobule: Sometimes it works.
Sweeney: Sometimes it doesn't. ♫ ♫ Together: The Jill and Julia, the Jill and Julia, the Jill and Julia Show. ♫ (Applause)
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.
A hundred years ago, Albert Einstein first published his theory of general 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, an 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 hole today, I'd like to give you a brief glimpse into the effort involved in getting that first picture.
My name is Katie Bouman, and I'm a PhD goldenmary@example.net.
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 tonight, 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 light-years 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 spectacular.
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 supermassive black hole -- an object so dense that it sucks up anything that ventures too close -- even light.
But what happens if we were to zoom in even further?
Is it possible to see something that, by definition, is impossible to see?
Well, it turns out that if we were to zoom in at radio wavelengths, we'd 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 would 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, that 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.
Due to a phenomenon called diffraction, 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.
In fact, here I show one of the highest resolution images ever taken of the moon from Earth.
It contains roughly 13,000 pixels, and yet each pixel would contain over 1.5 million oranges.
So how big of a telescope do we need in order to see an orange on the surface of the moon and, by extension, our black hole?
Well, it turns out that by crunching the numbers, you can easily calculate that we would need a telescope the size of the entire Earth.
(Laughter) If we could build this Earth-sized telescope, we could just start to make out that distinctive ring of light indicative of the black hole's event horizon.
Although this picture wouldn't contain all the detail we see in computer graphic renderings, it would allow us to safely get our first glimpse of the immediate environment around a black hole.
However, as you can imagine, building a single-dish telescope the size of the Earth is impossible.
But in the famous words of Mick Jagger, "You can't always get what you want, but if you try sometimes, you just might find you get what you need."
And by connecting telescopes from around the world, an international collaboration called the Event Horizon Telescope is creating a computational telescope the size of the Earth, capable of resolving structure on the scale of a black hole's event horizon.
This network of telescopes is scheduled to take its very first picture of a black hole next year.
Each telescope in the worldwide network works together.
Linked through the precise timing of atomic clocks, teams of researchers at each of the sites freeze light by collecting thousands of terabytes of data.
This data is then processed in a lab right here in Massachusetts.
So how does this even work?
Remember if we want to see the black hole in the center of our galaxy, we need to build this impossibly large Earth-sized telescope?
For just a second, let's pretend we could build a telescope the size of the Earth.
This would be a little bit like turning the Earth into a giant spinning disco ball.
Each individual mirror would collect light that we could then combine together to make a picture.
However, now let's say we remove most of those mirrors so only a few remained.
We could still try to combine this information together, but now there are a lot of holes.
These remaining mirrors represent the locations where we have telescopes.
This is an incredibly small number of measurements to make a picture from.
But although we only collect light at a few telescope locations, as the Earth rotates, we get to see other new measurements.
In other words, as the disco ball spins, those mirrors change locations and we get to observe different parts of the image.
The imaging algorithms we develop fill in the missing gaps of the disco ball in order to reconstruct the underlying black hole image.
If we had telescopes located everywhere on the globe -- in other words, the entire disco ball -- this would be trivial.
However, we only see a few samples, and for that reason, there are an infinite number of possible images that are perfectly consistent with our telescope measurements.
However, not all images are created equal.
Some of those images look more like what we think of as images than others.
And so, my role in helping to take the first image of a black hole is to design algorithms that find the most reasonable image that also fits the telescope measurements.
Just as a forensic sketch artist uses limited descriptions to piece together a picture using their knowledge of face structure, the imaging algorithms I develop use our limited telescope data to guide us to a picture that also looks like stuff in our universe.
Using these algorithms, we're able to piece together pictures from this sparse, noisy data.
So here I show a sample reconstruction done using simulated data, when we pretend to point our telescopes to the black hole in the center of our galaxy.
Although this is just a simulation, reconstruction such as this give us hope that we'll soon be able to reliably take the first image of a black hole and from it, determine the size of its ring.
Although I'd love to go on about all the details of this algorithm, luckily for you, I don't have the time.
But I'd still like to give you a brief idea of how we define what our universe looks like, and how we use this to reconstruct and verify our results.
Since there are an infinite number of possible images that perfectly explain our telescope measurements, we have to choose between them in some way.
We do this by ranking the images based upon how likely they are to be the black hole image, and then choosing the one that's most likely.
So what do I mean by this exactly?
Let's say we were trying to make a model that told us how likely an image were to appear on Facebook.
We'd probably want the model to say it's pretty unlikely that someone would post this noise image on the left, and pretty likely that someone would post a selfie like this one on the right.
The image in the middle is blurry, so even though it's more likely we'd see it on Facebook compared to the noise image, it's probably less likely we'd see it compared to the selfie.
But when it comes to images from the black hole, we're posed with a real conundrum: we've never seen a black hole before.
In that case, what is a likely black hole image, and what should we assume about the structure of black holes?
We could try to use images from simulations we've done, like the image of the black hole from "Interstellar," but if we did this, it could cause some serious problems.
What would happen if Einstein's theories didn't hold?
We'd still want to reconstruct an accurate picture of what was going on.
If we bake Einstein's equations too much into our algorithms, we'll just end up seeing what we expect to see.
In other words, we want to leave the option open for there being a giant elephant at the center of our galaxy.
(Laughter) Different types of images have very distinct features.
We can easily tell the difference between black hole simulation images and images we take every day here on Earth.
We need a way to tell our algorithms what images look like without imposing one type of image's features too much.
One way we can try to get around this is by imposing the features of different kinds of images and seeing how the type of image we assume affects our reconstructions.
If all images' types produce a very similar-looking image, then we can start to become more confident that the image assumptions we're making are not biasing this picture that much.
This is a little bit like giving the same description to three different sketch artists from all around the world.
If they all produce a very similar-looking face, then we can start to become confident that they're not imposing their own cultural biases on the drawings.
One way we can try to impose different image features is by using pieces of existing images.
So we take a large collection of images, and we break them down into their little image patches.
We then can treat each image patch a little bit like pieces of a puzzle.
And we use commonly seen puzzle pieces to piece together an image that also fits our telescope measurements.
Different types of images have very distinctive sets of puzzle pieces.
So what happens when we take the same data but we use different sets of puzzle pieces to reconstruct the image?
Let's first start with black hole image simulation puzzle pieces.
OK, this looks reasonable.
This looks like what we expect a black hole to look like.
But did we just get it because we just fed it little pieces of black hole simulation images?
Let's try another set of puzzle pieces from astronomical, non-black hole objects.
OK, we get a similar-looking image.
And then how about pieces from everyday images, like the images you take with your own personal camera?
Great, we see the same image.
When we get the same image from all different sets of puzzle pieces, then we can start to become more confident that the image assumptions we're making aren't biasing the final image we get too much.
Another thing we can do is take the same set of puzzle pieces, such as the ones derived from everyday images, and use them to reconstruct many different kinds of source images.
So in our simulations, we pretend a black hole looks like astronomical non-black hole objects, as well as everyday images like the elephant in the center of our galaxy.
When the results of our algorithms on the bottom look very similar to the simulation's truth image on top, then we can start to become more confident in our algorithms.
And I really want to emphasize here that all of these pictures were created by piecing together little pieces of everyday photographs, like you'd take with your own personal camera.
So an image of a black hole we've never seen before may eventually be created by piecing together pictures we see all the time of people, buildings, trees, cats and dogs.
Imaging ideas like this will make it possible for us to take our very first pictures of a black hole, and hopefully, verify those famous theories on which scientists rely on a daily basis.
But of course, getting imaging ideas like this working would never have been possible without the amazing team of researchers that I have the privilege to work with.
It still amazes me that although I began this project with no background in astrophysics, what we have achieved through this unique collaboration could result in the very first images of a black hole.
But big projects like the Event Horizon Telescope are successful due to all the interdisciplinary expertise different people bring to the table.
We're a melting pot of astronomers, physicists, mathematicians and engineers.
This is what will make it soon possible to achieve something once thought impossible.
I'd like to encourage all of you to go out and help push the boundaries of science, even if it may at first seem as mysterious to you as a black hole.
Thank you.
(Applause)