Friday, August 30, 2013
Tuesday, August 13, 2013
A Black Hole Mystery Wrapped in a Firewall Paradox
A Black Hole Mystery Wrapped in a Firewall Paradox
By DENNIS OVERBYE
Published: August 12, 2013 188 Comments
This time, they say, Einstein might really be wrong.
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A high-octane debate has broken out among the world’s physicists about what would happen if you jumped into a black hole, a fearsome gravitational monster that can swallow matter, energy and even light. You would die, of course, but how? Crushed smaller than a dust mote by monstrous gravity, as astronomers and science fiction writers have been telling us for decades? Or flash-fried by a firewall of energy, as an alarming new calculation seems to indicate?
This dire-sounding debate has spawned a profusion of papers, blog posts and workshops over the last year. At stake is not Einstein’s reputation, which is after all secure, or even the efficacy of our iPhones, but perhaps the basis of his general theory of relativity, the theory of gravity, on which our understanding of the universe is based. Or some other fundamental long-established principle of nature might have to be abandoned, but physicists don’t agree on which one, and they have been flip-flopping and changing positions almost weekly, with no resolution in sight.
“I was a yo-yo on this,” said one of the more prolific authors in the field, Leonard Susskind of Stanford. He paused and added, “I haven’t changed my mind in a few months now.”
Raphael Bousso, a theorist at the University of California, Berkeley, said, “I’ve never been so surprised. I don’t know what to expect.”
You might wonder who cares, especially if encountering a black hole is not on your calendar. But some of the basic tenets of modern science and of Einstein’s theory are at stake in the “firewall paradox,” as it is known.
“It points to something missing in our understanding of gravity,” said Joseph Polchinski, of the Kavli Institute for Theoretical Physics in Santa Barbara, Calif., one of thetheorists who set off this confusion.
Down this rabbit hole are many of the jazzy magical mysteries of modern physics: Black holes. The shortcuts through space and time called wormholes. Quantum entanglement, also known as spooky action at a distance, in which particles separated by light-years can still instantaneously appear to remain connected. The reward for going down this hole could be a new understanding of why we think we live in a universe with space and time at all, with suitably unpredictable consequences. After all, if Einstein hadn’t been troubled a century ago by logical inconsistencies in the Newtonian universe, we might not have GPS systems, which rely on his theory of general relativity to keep time, in our pockets today.
Falling Bodies
Black holes are the most extreme predictions of Einstein’s theory, which describes how matter and energy warp the geometry of space and time the way a heavy sleeper causes a mattress to sag. Too much matter and energy in one place could cause space to sag so far that the matter inside it would disappear as if behind a magician’s cloak, collapsing endlessly to a point of infinite density known as a singularity. Einstein thought that idea was ridiculous when it was pointed out to him at the time, in 1916, but today astronomers agree that the universe is speckled with such dark monsters, including beasts lurking in the hearts of most galaxies that are millions and billions of time more massive than the Sun. Many of them resulted from the collapse of dead stars.
General relativity is based on what Einstein later called his “happiest thought,” that a freely falling person would not feel his weight. It is known simply as the equivalence principle; it says that empty space looks the same everywhere and to everyone.
One consequence of this principle is that an astronaut would not feel anything special happening when he fell through the point of no return, known as the event horizon, into a black hole. Like a bungee jumper, he would feel weightless then and all the way until he hit the bottom, which could take seconds or years depending on how big the hole was, and he would be stretched like a noodle by tidal forces and then crushed into a speck. At the event horizon there would be “no drama,” in the lexicon — at least in the physical sense, as opposed to the intellectual trauma of knowing you were not ever going home. Things or people went in, they got crushed to infinite density and disappeared. That was the traditional view of black holes.
Things got more interesting, however, in 1974 when Stephen Hawking, the British cosmologist, stunned the world by showing that when the paradoxical quantum laws that describe subatomic behavior were taken into account, black holes would leak particles and radiation, and in fact eventually explode, although for a hole the mass of a star it would take longer than the age of the universe.
This was a breakthrough in combining general relativity, the gravity that curves the cosmos, with quantum theory, which describes the microscopic quirkiness inside it, but there was a big hitch. Dr. Hawking concluded that the radiation coming from a black hole would be completely random, conveying no information about what had fallen into it. When the black hole finally exploded, all that information would be erased from the universe forever. “God not only plays dice with the universe,” Dr. Hawking said in 1976 in a riposte to Einstein’s famous doubts about the randomness of quantum theory, “he sometimes throws them where they can’t be seen.”
Particle physicists cried foul, saying that this violated a basic tenet of modern science and of quantum theory, that information is always preserved. From the material in the smoke and flames of a burning book, for example, one could figure out whether it was the Bible or the Kama Sutra; the same should be true of the fizz and pop of black holes, these physicists argued. A 30-year controversy ensued.
It was front-page news in 2004 when Dr. Hawking finally said that he had been wrong, and paid off a bet.
The Firewall Paradox
Now, however, some physicists say that Dr. Hawking might have conceded too soon. “He had good reason,” said Dr. Polchinski, “but he gave up for the wrong reason.” Nobody, he explained, had yet figured out exactly how information does get out of a black hole.
That was the task that four researchers based in Santa Barbara — Ahmed Almheiri, Donald Marolf, and James Sully, all from the University of California, Santa Barbara, and Dr. Polchinski of the Kavli Institute set themselves a year ago. The team (called AMPS, after their initials) found, to their surprise, that following the known laws of physics would lead to a contradiction, the firewall paradox.
Their calculations showed that having information flowing out of a black hole was incompatible with having an otherwise smooth Einsteinian space-time at its boundary, the event horizon. In its place would be a discontinuity in the vacuum that would manifest itself as energetic particles — a “firewall” — lurking just inside the black hole.
Being incinerated as you entered a black hole would certainly contradict Einstein’s dictum of no drama. If this were true, you would in fact die long before the bungee-jumping ride ever got anywhere close to the bottom. The existence of a firewall would mean that the horizon, which according to general relativity is just empty space, is a special place, pulling the rug out from under Einstein’s principle, his theory of gravity, and modern cosmology, which is based on general relativity. This presented the scientists with what Dr. Bousso calls the “menu from hell.” If the firewall argument was right, one of three ideas that lie at the heart and soul of modern physics, had to be wrong. Either information can be lost after all; Einstein’s principle of equivalence is wrong; or quantum field theory, which describes how elementary particles and forces interact, is wrong and needs fixing. Abandoning any one of these would be revolutionary or appalling or both.
Dr. Polchinski was very surprised by the result. “It seemed like such a simple argument that it must have been considered and resolved earlier,” he said. After trying to kill it by talking to colleagues in Santa Barbara, he e-mailed Dr. Susskind of Stanford, an old hand at black holes and information, expecting that Dr. Susskind would point out the error.
“But after a week or two of disbelief,” Dr. Polchinski said, “he was as confused as we” were.
Dr. Susskind said: “The arguments are very clear. Nobody knew what to make of them.”
Quantum Vows
The firewall argument hinges on one of the weirder aspects of quantum physics, the action called entanglement. As Einstein, Boris Podolsky and Nathan Rosen pointed out in 1935, quantum theory predicts that a pair of particles can be connected in such a way that measuring a property of one — its direction of spin, say — will immediately affect the results of measuring the other one, even if it is light-years away.
Einstein used this “spooky action at a distance” to suggest the absurdity of quantum mechanics, but such experiments are now done in labs every day. You can’t use it to send a message faster than light, because the correlation shows up only when the two experimenters get together and compare their respective results. But it plays a crucial role in quantum computing and cryptography — and, it turns out, in explaining how information encoded in the Hawking radiation gets out of a black hole.
Consider two particles (let’s call them Bob and Alice) that have been radiated by a black hole. Bob left it eons ago, as it began leaking radiation; quantum entanglement theory dictates that in order for the black hole to keep track of what information it has been transmitting, Bob out there has to be entangled with Alice, who just left.
But that scenario competes with another kind of entanglement, between particles on either side of the event horizon, the black hole’s boundary. If space is indeed smooth, as Einstein postulated, and if quantum field theory is correct, Alice must be entangled with another particle, Ted, who is just inside the black hole.
But quantum theory forbids promiscuous entanglements. In the language of quantum information, Alice can marry either Bob or Ted, but not both, even if the second marriage happens inside the black hole where most of us can’t see it.
Alice should have a consistent explanation of the universe, Dr. Polchinski explained, “just as we ourselves must, even though we are inside the cosmic horizon.”
And so smoke pours from the AMPS group’s computers and has continued to pour from the particle accelerators of the mind, fueled by coffee and blackboard chalk this last year. Firewall or not? Does information live or die? Is Einstein at last wrong? Experiments would not help, even if we had a black hole in a laboratory, because the putative firewall, if it exists, would be just inside where it can’t be seen safely.
At a firewall workshop this winter, John Preskill, a Caltech theorist who won a bet with Dr. Hawking on the randomness of information from a black hole, declared that physicists were back where they had been 40 years ago.
The Menu From Hell
Dr. Bousso said his first response to the AMPS paper was, “Come on, you gotta be kidding me.” He added, “Everybody goes through their stages of grief.”
About 40 papers have been devoted to firewalls in the last year, and more are on the way. Daniel Harlow of Princeton and Patrick Hayden of McGill University suggested that the issue might be moot; the computation necessary to verify that Alice and Bob are entangled could take longer than the age of the universe and the black hole would evaporate in the meantime, making it impossible ever to go inside and experience the contradiction.
Failing that, which of the items on Dr. Bousso’s “menu from hell” might have to go depends on who is speaking.
In some ways, it would be easiest to give up quantum field theory, which describes what empty space should look like, in the case of someone who is being accelerated, perhaps by gravity pulling him down a black hole. After all, quantum theory, with “virtual” particles flitting in and out of existence and spooky entanglements is already strange. On the other hand, as Ed Witten of the Institute for Advanced Study, who has so far watched the firewall debate from a distance, said, “Quantum field theory is how the world works.” It had a major triumph just a year ago, when the Higgs boson, a subatomic particle responsible for the mass of other subatomic particles, was discovered after a 40-year search, at the Large Hadron Collider at CERN.
Meanwhile, physicists have more reason than ever to think that information cannot be lost. A celebrated 1997 paper by Juan M. Maldacena of the Institute for Advanced Study describes nature as a kind of hologram, in which the information about what happens inside a volume of three-dimensional space, for example, is encoded in quantum equations on its two-dimensional boundary, the way a 3-D image is encoded on the face of your bank card.
Mark Van Raamsdonk, a young theorist at the University of British Columbia, likes to use a spookier analogy to describe this, namely the chip that controls a Matrix-like video game. (Feel free to insert your own woo-woo music here.)
The discovery that the information needed to describe what happens in some volume is proportional to the area enclosing that volume is the strangest and most far-reaching consequence of Dr. Hawking’s discovery that black holes explode, and is still wreathed in mystery.
Dr. Maldacena’s universe is often portrayed like a can of soup, in which galaxies, black holes, gravity, stars and so forth, including us, are the soup inside, while the information to describe them resides, like a label, on the outside. Think of it as gravity in a can. The equations that represent the label are deterministic and there is no room in them for information to be lost, implying that information in the universe inside is also preserved.
Which leaves the firewall as the only way to stop the illegal marriage of Alice and Ted, Dr. Polchinski said — an odious solution because it contravenes the basic principle of general relativity.
He pointed out, however, that in a sense physicists had already thrown Einstein under the bus. In Dr. Maldacena’s holographic universe, considered to be the last word on quantum gravity, the dimensions of space-time do not seem to matter. “We’ve known for years that space-time is not fundamental,” Dr. Polchinski said. “General relativity is not fundamental.”
He went on, “space-time is emergent. Gravity is emergent. Maybe sometimes it doesn’t always emerge.”
Einstein’s Revenge
But if space and time and gravity are not fundamental, what is?
Recently a new way of solving the firewall conundrum and of answering that haunting question has attracted a lot of attention, although no consensus. Dr. Maldacena and Dr. Susskind have proposed that Einstein could come to his own rescue via one more far-out notion in modern physics: wormholes.
In 1935 Einstein and Rosen found that, mathematically anyway, black holes could come in pairs connected by shortcuts through space — then known as Einstein-Rosen bridges, now known as wormholes. A wormhole would not be traversable by any means we now know about, ruling out time travel and other violations of relativity, despite the dreams of science fiction writers and interstellar pioneers.
In 2010, Dr. Van Raamsdonk of British Columbia suggested that such wormholes were thegeometric manifestations of quantum entanglement. After all, neither of these phenomena, which seemed to transcend local space, could be used for sending direct messages. Brian Swingle at M.I.T. had made a similar suggestion a year earlier.
In effect, what these theorists were saying was that without the phenomenon of entanglement, space-time would have no structure at all. Or as Dr. Maldacena put it, “Spooky action at a distance creates space-time.” If true, this insight would be a step toward a longtime dream of theorists of explaining how space and time emerge from some more basic property of reality, in this case, bits of quantum information. The theorist John Wheeler, of Princeton, who had coined the term “black hole,” called this concept “it from bit.”
Taking this idea seriously, Dr. Maldacena and Dr. Susskind proposed that a similar kind of wormhole arrangement existed between the black hole in the AMPS case and its Hawking radiation. Instead of a tunnel snaking through hyperspace and opening at the maw of another black hole, the wormhole would split into a zillion spaghetti-like strands ending on each of the pieces of Hawking radiation. That would mean that Bob, the Hawking particle in the cartoon version of the theory mentioned above, might be light years away from the event horizon, but he would still be connected to the interior of the black hole, as if there were a doorway in New Jersey that opened up into a basement in Manhattan.
Because of this wormhole connection, Dr. Maldacena explained, “Ted and Bob are the same.” So the result is sort of like the happy ending of one of those screwball romantic comedies that involve mistaken identity and the handsome vagabond turns out to be the prince in disguise; Alice can marry Ted who is really Bob and the bonds of matrimony extend smoothly across the edge of the black hole.
In that case, then, there is no firewall, no contradiction in the laws of physics. And Einstein survives to fight another day.
“If right, this is clearly a major insight into gravity and quantum mechanics,” an enthusiastic Dr. Susskind said. “I think of it as a very dramatic thing,” he said, noting that long after Einstein’s career was presumed to be over, at 56, “he produced these ideas” of entanglement and wormholes having no idea they were connected.
“The man keeps giving.”
But Einstein is not safe yet.
“At first whiff,” Dr. Preskill wrote in a recent blog post, the Maldacena-Susskind conjecture “may smell fresh and sweet, but it will have to ripen on the shelf for a while.” He added, “For now, wormhole lovers can relish the possibilities.”
Entangled Theories
Dr. Maldacena and Dr. Susskind admit that the wormhole hypothesis is still a work in progress. Few of their colleagues are convinced yet that it has been formulated in sufficient detail, let alone that it can solve the firewall paradox. “All I can say,” Dr. Susskind said in an e-mail on the eve of a firewall workshop next week at the Kavli Institute where wormholes and everything else will surely be scrutinized, “is that no one has a completely solid case and that certainly includes me. Time will tell.”
Dr. Polchinski said, “My current thinking is that all the arguments that we are having are the kind of arguments that you make when you don’t have a theory.” We need a more complete theory of gravity, he concluded.
“Maybe ‘space-time from entanglement’ is the right place to start,” he wrote. “I am not sure.”
Dr. Bousso, who has been e-mailing with Dr. Maldacena, is skeptical that the wormholes will eliminate firewalls. “My own view is that it’s time to move on, accept, and actually understand firewalls,” he said. After all, he added, there’s no principle of nonviolence in the universe, except for Einstein’s equivalence principle, which says the black hole’s horizon is not a special place. But maybe it is, after all.
Meanwhile, Dr. Bousso said, the present debate had raised his estimation, “by another few notches,” of the “stupendous magnitude” of Dr. Hawking’s original discovery of the information paradox.
The firewall paradox,” he said, “tells us that the conceptual cost of getting information back out of a black hole is even more revolutionary than most of us had believed.”
The Firewall Paradox An unexpected paradox involving black holes pits two basic tenets of modern science against one another: the theory of quantum mechanics, which governs subatomic particles, and Einstein’s theory of general relativity, which explains how gravity works.
Published: August 12, 2013
The Firewall Paradox
An unexpected paradox involving black holes pits two basic tenets of modern science against one another: the theory of quantum mechanics, which governs subatomic particles, and Einstein’s theory of general relativity, which explains how gravity works. Related Article »
IF INFORMATION IS NEVER LOST ...
According to quantum mechanics, information that falls into a black hole will not be lost forever. Even after the black hole explodes, the information contained in it can still be recovered.
If information cannot be lost, each particle that escapes from a black hole must be linked to another particle that escaped earlier.
AND SPACE-TIME IS SMOOTH ...
According to Einstein’s theory of general relativity, particles pass smoothly over the threshhold of a black hole. If the particle were a person, he or she would experience “no drama” at the border.
In order for space-time to be smooth, each particle that leaves a black hole must be linked to another particle inside the black hole.
THERE IS A PARADOX!
Particles can have only one link. When forced to choose between the two laws, physicists have generally sided with the idea that information is never lost.
If an exiting particle must be linked to a partner outside the black hole, it will have to break the link with its partner inside. The energy released in these breaks would create a “firewall” — a ring of fire around the black hole that violates the theory
of “no drama.”
of “no drama.”
A POSSIBLE SOLUTION?
If each escaping particle remains connected to the black hole through a wormhole, only one link would be required to connect the particles. Both laws of physics would be preserved.
The distant particle and the particle inside the black hole could be the same particle.
Saturday, August 10, 2013
COLOR / into the center and added to the Goethe Newton argument /Beau Lotto: Optical illusions show how we see /
Beau Lotto: Optical illusions show how we see /
I want to start with a game. And to win this game, all you have to do is see the reality that's in front of you as it really is. All right? So, we have two panels here, of colored dots. And one of those dots is the same in the two panels. Okay? And you have to tell me which one.
Now, narrow it down to the gray one, the green one and, say, the orange one. So, by a show of hands -- we'll start with the easiest one -- Show of hands: how many people think it's the gray one? Really? Okay. How many people think it's the green one? And how many people think it's the orange one? Pretty even split.
Let's find out what the reality is. Here is the orange one. (Laughter) Here is the green one.And here is the gray one. (Laughter) So, for all of you who saw that, you're a complete realist. All right? (Laughter)
So, this is pretty amazing, actually, isn't it? Because nearly every living system has evolved the ability to detect light in one way or another. So, for us, seeing color is one of the simplest things the brain does. And yet, even at this most fundamental level, context is everything. What I want to talk about is not that context is everything, but why is context everything. Because it's answering that question that tells us not only why we see what we do, but who we are as individuals, and who we are as a society.
But first, we have to ask another question, which is, "What is color for?" And instead of telling you, I'll just show you. What you see here is a jungle scene, and you see the surfaces according to the amount of light that those surfaces reflect. Now, can any of you see the predator that's about to jump out at you? And if you haven't seen it yet, you're dead. Right? (Laughter) Can anyone see it? Anyone? No? Now, let's see the surfaces according to the quality of light that they reflect. And now you see it.
So, color enables us to see the similarities and differences between surfaces, according to the full spectrum of light that they reflect. But what you've just done is, in many respects, mathematically impossible. Why? Because, as Berkeley tells us, we have no direct access to our physical world, other than through our senses. And the light that falls onto our eyesis determined by multiple things in the world -- not only the color of objects, but also the color of their illumination, and the color of the space between us and those objects. You vary any one of those parameters, and you'll change the color of the light that falls onto your eye.
This is a huge problem because it means that the same image could have an infinite number of possible real-world sources. So let me show you what I mean. Imagine that this is the back of your eye. And these are two projections from the world. They are identical in every single way. Identical in shape, size, spectral content. They are the same, as far as your eye is concerned. And yet they come from completely different sources. The one on the right comes from a yellow surface, in shadow, oriented facing the left, viewed through a pinkish medium. The one on the left comes from an orange surface, under direct light, facing to the right, viewed through a sort of a bluish medium. Completely different meanings, giving rise to the exact same retinal information. And yet it's only the retinal information that we get.
So how on Earth do we even see? So, if you remember anything in this next 18 minutes,remember this: that the light that falls on to your eye, sensory information, is meaningless,because it could mean literally anything. And what's true for sensory information is true for information generally. There is no inherent meaning in information. It's what we do with that information that matters.
So, how do we see? Well, we see by learning to see. So, the brain evolved the mechanisms for finding patterns, finding relationships in information and associating those relationships with a behavioral meaning, a significance, by interacting with the world. We're very aware of this in the form of more cognitive attributes, like language. So, I'm going to give you some letter strings. And I want you to read them out for me, if you can.
Beau Lotto: "What are you reading?" Half the letters are missing. Right? There is no a priori reason why an "H" has to go between that "W" and "A." But you put one there. Why?Because in the statistics of your past experience it would have been useful to do so. So you do so again. And yet you don't put a letter after that first "T." Why? Because it wouldn't have been useful in the past. So you don't do it again.
So let me show you how quickly our brains can redefine normality, even at the simplest thing the brain does, which is color. So, if I could have the lights down up here. I want you to first notice that those two desert scenes are physically the same. One is simply the flipping of the other. Okay? Now I want you to look at that dot between the green and the red. Okay? And I want you to stare at that dot. Don't look anywhere else. And we're going to look at that for about 30 seconds, which is a bit of a killer in an 18-minute talk. (Laughter)
But I really want you to learn. And I'll tell you -- don't look anywhere else -- and I'll tell you what's happening inside your head. Your brain is learning. And it's learning that the right side of its visual field is under red illumination; the left side of its visual field is under green illumination. That's what it's learning. Okay? Now, when I tell you, I want you to look at the dot between the two desert scenes. So why don't you do that now? (Laughter) Can I have the lights up again?
I take it from your response they don't look the same anymore. Right? (Applause) Why? Because your brain is seeing that same information as if the right one is still under red light,and the left one is still under green light. That's your new normal.
So, what does this mean for context? It means that I can take these two identical squares,and I can put them in light and dark surrounds. And now the one on the dark surround looks lighter than the one on the light surround. What's significant is not simply the light and dark surrounds that matter. It's what those light and dark surrounds meant for your behavior in the past.
So I'll show you what I mean. Here we have that exact same illusion. We have two identical tiles, on the left, one in a dark surround, one in a light surround. And the same thing over on the right. Now, what I'm going to do is I'm going to review those two scenes. But I'm not going to change anything within those boxes, except their meaning. And see what happens to your perception.
Notice that on the left the two tiles look nearly completely opposite: one very white and one very dark. All right? Whereas on the right, the two tiles look nearly the same. And yet there is still one on a dark surround and one on a light surround. Why? Because if the tile in that shadow were in fact in shadow, and reflecting the same amount of light to your eye as the one outside the shadow, it would have to be more reflective -- just the laws of physics. So you see it that way.
Whereas on the right, the information is consistent with those two tiles being under the same light. If they are under the same light, reflecting the same amount of light to your eye,then they must be equally reflective. So you see it that way. Which means we can bring all this information together to create some incredibly strong illusions.
This is one I made a few years ago. And you'll notice you see a dark brown tile at the top,and a bright orange tile at the side. That is your perceptual reality. The physical reality is that those two tiles are the same.
Here you see four gray tiles on your left, seven gray tiles on the right. I'm not going to change those tiles at all, but I'm going to reveal the rest of the scene and see what happens to your perception. The four blue tiles on the left are gray. The seven yellow tiles on the right are also gray. They are the same. Okay? Don't believe me? Let's watch it again.
What's true for color is also true for complex perceptions of motion. So here we have -- let's turn this around -- a diamond. And what I'm going to do is, I'm going to hold it here, and I'm going to spin it. And for all of you, you'll see it probably spinning this direction. Now I want you to keep looking at it. Move your eyes around, blink, maybe close one eye. And suddenly it will flip, and start spinning the opposite direction. Yes? Raise your hand if you got that. Yes? Keep blinking. Every time you blink it will switch. Alright? So I can ask you, which direction is it rotating? How do you know? Your brain doesn't know. Because both are equally likely. So depending on where it looks, it flips between the two possibilities.
Are we the only ones that see illusions? The answer to this question is no. Even the beautiful bumblebee, with its mere one million brain cells, which is 250 times fewer cells than you have in one retina, sees illusions, does the most complicated things that even our most sophisticated computers can't do. So in my lab, we of course work on bumblebees.Because we can completely control their experience, and see how that alters the architecture of their brain. And we do this in what we call the Bee Matrix.
And here you have the hive. You can see the queen bee, that large bee in the middle there. Those are all her daughters, the eggs. And they go back and forth between this hive and the arena, via this tube. And you'll see one of the bees come out here. You see how she has a little number on her? Yeah there is another one coming out. She has another number on her. Now, they are not born that way. Right? We pull them out, put them in the fridge, and they fall asleep. And then you can superglue little numbers on them. (Laughter)
And now, in this experiment they get rewarded if they go to the blue flowers. And they land on the flower. They stick their tongue in there, called a proboscis, and they drink sugar water. Now she is drinking a glass of water that's about that big to you and I, will do that about three times, and then fly. And sometimes they learn not to go to the blue, but to go to where the other bees go. So they copy each other. They can count to five. They can recognize faces. And here she comes down the ladder. And she'll come into the hive, find an empty honey pot and throw up, and that's honey. (Laughter)
Now remember -- (Laughter) -- she's supposed to be going to the blue flowers. But what are these bees doing in the upper right corner? It looks like they're going to green flowers. Now, are they getting it wrong? And the answer to the question is no. Those are actually blue flowers. But those are blue flowers under green light. So they are using the relationships between the colors to solve the puzzle, which is exactly what we do.
So, illusions are often used, especially in art, in the words of a more contemporary artist,"to demonstrate the fragility of our senses." Okay, this is complete rubbish. The senses aren't fragile. And if they were, we wouldn't be here. Instead, color tells us something completely different, that the brain didn't actually evolve to see the world the way it is. We can't. Instead, the brain evolved to see the world the way it was useful to see in the past.And how we see is by continually redefining normality.
So how can we take this incredible capacity of plasticity of the brain and get people to experience their world differently? Well, one of the ways we do in my lab and studio is we translate the light into sound and we enable people to hear their visual world. And they can navigate the world using their ears.
Here is David, in the right. And he is holding a camera. On the left is what his camera sees.And you'll see there is a line, a faint line going across that image. That line is broken up into 32 squares. In each square we calculate the average color. And then we just simply translate that into sound. And now he's going to turn around, close his eyes, and find a plate on the ground with his eyes closed.
He finds it. Amazing. Right? So not only can we create a prosthetic for the visually impaired, but we can also investigate how people literally make sense of the world. But we can also do something else. We can also make music with color. So, working with kids,they created images, thinking about what might the images you see sound like if we could listen to them. And then we translated these images. And this is one of those images. And this is a six-year-old child composing a piece of music for a 32-piece orchestra. And this is what it sounds like. So, a six-year-old child. Okay?
Now, what does all this mean? What this suggests is that no one is an outside observer of nature. Okay? We are not defined by our central properties, by the bits that make us up.We're defined by our environment and our interaction with that environment -- by our ecology. And that ecology is necessarily relative, historical and empirical. So what I'd like to finish with is this over here. Because what I've been trying to do is really celebrate uncertainty. Because I think only through uncertainty is there potential for understanding.
So, if some of you are still feeling a bit too certain, I'd like to do this one. So, if we have the lights down. And what we have here -- Can everyone see 25 purple surfaces on your left,and 25, call it yellowish, surfaces on your right? So, now, what I want to do: I'm going to put the middle nine surfaces here under yellow illumination by simply putting a filter behind them. All right. Now you can see that changes the light that's coming through there. Right?Because now the light is going through a yellowish filter and then a purplish filter. I'm going to do this opposite on the left here. I'm going to put the middle nine under a purplish light.
Now, some of you will notice that the consequence is that the light coming through those middle nine on the right, or your left, is exactly the same as the light coming through the middle nine on your right. Agreed? Yes? Okay. So they are physically the same. Let's pull the covers off. Now remember, you know the middle nine are exactly the same. Do they look the same? No. The question is, "Is that an illusion?" And I'll leave you with that. So, thank you very much. (Applause)
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