English subtitles for clip: File:Quantum physicist Juan Maldacena on the new quantum-reality theory-VPRO-The Mind of the Universe.ogv

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Interviewer: I will ask a lot of questions, but I prefer it to be like a conversation, so interrupt me if you like.

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Juan Maldacena: Right, good.

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Interviewer: The first thing, can you introduce yourself?

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Juan Maldacena: Yeah, I'm Juan Maldacena, I'm the Carl Feinberg professor here at the Institute for Advanced Study.

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Interviewer: What exactly is your field of research?

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Juan Maldacena: My field of research is in trying to understand the fundamental laws of nature,

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trying to develop theories that connect space-time and quantum mechanics,

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and the main objective is to understand the beginning of the Big Bang.

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Interviewer: Well, that's a big question.

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Juan Maldacena: Yeah.

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Interviewer: Did you say the laws of nature?

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Juan Maldacena: Yeah. Physics is about studying the laws of nature, so how nature works.

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Through the years we've learned a lot about how nature works,

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and currently we have theories that are incredibly successful.

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One of the theories is the theory that describes gravity.

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It was originally developed by Newton, and then improved by Einstein.

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Einstein gave us the current equations that govern the behavior of space-time.

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We'll discuss perhaps a bit more about what space-time is made of,

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or what the theory of Einstein tells us about space-time. That's one very successful theory.

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It explained things like the expansion of the universe, the formation of black holes..

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Its phenomena that before the theory was introduced, were ..

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People didn't even think about them.	On the other hand we the whole set of theories that describe matter,

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the behavior of matter and the structure of matter.

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These theories were rational,

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especially rational quantum mechanical study being developed in the beginning of the 20th century.

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The quantum is very important for the description of matter.

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It's what keeps matter stable and prevents it from collapsing. Prevents atoms from collapsing, and so on.

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This theory, well, it was further developed through the 20th century

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and it's now come to what we call the standard model of particle physics.

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Interviewer: Particle physics.

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Juan Maldacena: It's basically the basic structures, the basic constituents of matter.

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Matter is made out of little, small particles that behave according to the so-called quantum mechanics.

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What is remarkable is that this list of constituents is very small.

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So a very small number of particles make up all the matter that we see.

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Interviewer: Really? So everything is built up from just a small number of particles?

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Juan Maldacena: Yes, small number of kinds of particles.

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We have the particles, the electron is one of them, and then we have the particles that make up the nuclei,

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the nuclei of the atom. Within the nuclei are some particles called quarks, but they are small, little particles.

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For most of matter they are made out of just two kinds, so-called up and down quark.

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Then there are some particles that mediate the forces within them. The photon, electromagnetic waves, and so on.

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Then the weak force and the strong force.

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The strong force keeps the nucleus together, and with these particles and these forces we can describe all of matter.

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Interviewer: You know that, or you think so?

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Juan Maldacena: No, well we know it experimentally,

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and the latest experiment was the experiment in the large hydro collider, which discovered the so-called Higgs boson,

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which was one of the missing particles in the standard model.

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Now we have whole set of particles that describes everything.

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I briefly told you about the particles that make up most all named matter,

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but there are other unstable particles which are similar, but the structure gets replicated a few times,

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and while so now we have a complete set of particles with a logically consistent theory that uses the structure of

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something called relativistic quantum mechanics.

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[crosstalk 00:04:30] Relativistic quantum mechanics,

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there's quantum mechanics plus the principle of special relativity.	We can discuss perhaps special relativity a little

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more. Let me discuss perhaps these theories a little more.

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Interviewer: Yes, that's okay.

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Juan Maldacena: Then I can go on into discussing perhaps the more current issues.

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First, well we have these notions of space and time. Right?

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In principle space and time seem totally disconnected from each other..

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The very intuitive notion of space, while time looks a little more mysterious to us, and a bit ..

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Certainly different from space.

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The first point I'd like to explain is why physicists talk about space-time, why they put these two words together.

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Why don't they talk about space temperature, space I don't know. Price of [solar 00:05:27] or whatever.

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They talk about these two things because the way you perceive time depends on how you are moving through space.	If you

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have two observers moving relative to each other, the two observers perceive time differently.

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If you have a clock here, another clock that is moving,

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the second clock will appear to this observer as moving slower than the clock here that's at rest.

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The other observer will see the other clock also moving slower.

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This can happen because space and time sort of get mixed by motion.

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This is the consequence of a principle, which is the principle that light,

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the speed of light is constant for these two observers. This is something that is not totally intuitive.

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You have one observer that is stationary and you have a light beam that travels this way,

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and you have another observer that moves in this direction, naively,

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according to your intuition you will expect that this observer should see the light moving slower.	Right?

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If instead of talking about the light beam we were talking about the train, that would be the case.

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But it turns out that experimentally the speed of light is constant, so it is the same for all observers.

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Interviewer: Oh really, so compared to the train?

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Juan Maldacena: Yes, so if instead of a train we had a beam of light, the two observers,

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one is stationary the other is moving, both would see the light going at the same speed,..

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so the light would be moving this way .. This happens because the rate of ..

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How time and space are perceived by the two observers are different.

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The price you have to pay for this constancy of the speed of light is that time is now relative.

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In the theory of relativity the speed of light is absolute, but time is relative.

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Time is relative to who's measuring it.

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Interviewer: I can try to understand what you are saying. What I hear is that you say the speed of light is constant.

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So time is not constant.

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Juan Maldacena: Right, time is relative.

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The flow of time depends on how you are moving through space-time, so it's similar to let's say space, right?

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So we are standing in space, there is some direction we call forward and some direction we call go right.

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But if you have another person who's looking in a different direction what's forward to him

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and what's to the right is different. So it's exactly the same but for two moving observers.

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You have two moving observers but one calls time and space is different from what the other calls time and space.

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That's why is more convenient to think about space-time as something that's both time and space,

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and that thing is the same for both.

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What one calls time and space is different,

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but space-time is the same.	It's the universal structure in which particles move.

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The laws of physics have to have this symmetry of the constancy of speed of light

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and the fact that the laws of physics should be independent of how you're moving.

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When you combine quantum mechanics and this principle of special relativity,

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you get the modern theory of quantum physics.

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Well you get the structure, which is called quantum [field 00:09:21] theory,

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and used in special cases of the structure, putting in which particles you have and the interactions and so on.

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You get the models for particle physics and they are incredibly successful

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and they describe all the experiments that you can do..

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Interviewer: In the beginning you raised the big question, how did the universe ..

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Juan Maldacena: Let me first say a few words about general relativity.

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According to our intuition, so space is sort of absolute and there is some [inaudible 00:10:03]

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in space where particles move and objects move.

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That's probably the theory of [mutant 00:10:13] we learned in school, that planets move and so on.

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They are moving in some space that was preexisting and it's not affected at all by the motion of these planets.

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But in the theory of [inaudible 00:10:25] what Einstein postulates is that space or space

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and time because they have to come together because of the principle of special relativity.

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They are actually structured that is dynamic because it can be bent by the presence of matter.	He further says that the

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force of gravity is due to this bend in our space-time. This is a new, very interesting conceptual idea.

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Again, it describes gravity as we see it, and it describes deviations from Newton's gravity.

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It describes new things that were not known at the time of Einstein, like the expansion of the universe,

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the formation of black holes in extreme circumstances.

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Well, some of it's predictions are have now been confirmed, like the discovery of gravity waves, very recently,

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just a week ago it was announced.

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Interviewer: Yeah, I saw that, were you excited about it.

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Juan Maldacena: Yeah, that's really exciting, very interesting.

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Interviewer: Did you know about that they were going to announce this?

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Juan Maldacena: Yeah, there were rumors that they were going to announce it.

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Of course the experiment had been going for a couple of decades.

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Interviewer: For a couple of billion years.

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Juan Maldacena: Well, the gravity waves were going on for a long time,

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but the the experiments trying to detect them also took a lot of effort.

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We're getting [dramatic 00:11:57] confirmation of both Einstein's theories.

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Moreover, the [seasons 00:12:02] of black holes.

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This theory of special relativity of general relativity, well Einstein the other equations,

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but then there was a lot of research trying to understand the solutions of equations.

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The physical interpretation of the solutions. For example, black holes were really only understood in the ‘60s.

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Even theoretically.

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Then understanding them better then led to understanding what things you should look for in the sky,

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and some objects in the sky were recognized as probably endings of black holes,

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and now we have this guy with the world detection which appears to come from the coalition of two black holes.

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Interviewer: You think so?

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Juan Maldacena: That’s a model to describe it. The only announce one coalition.

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Probably they see more, it will become more and more convincing..

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Interviewer: Yeah. Because this is the first one. It’s a question of time that more of this [crosstalk 00:13:04]

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Juan Maldacena: You would hope.

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Interviewer: Yeah.

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Juan Maldacena: That’s all about Einstein theory of relativity.

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Einstein theory of general relativity is a theory where space time is dynamical. It’s something that moves.

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It’s not the starting thing. It’s an actor in physics. It’s not the stage in which physics happens.

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It is the stage for all particle physics. For all the matter and so on.

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You have the space time and then matter moves in that space time.

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Also space time reacts to the presence of matter, and it moves itself.

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Through cosmology, this expansion of the space time is very important.

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Space time expands and it cools because of that expansion.

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Expansion of space time is very important for getting to the universe.

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What it is and structure of matter to what it is.	This expansion is important for cooling the universe

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and then further the force of gravity creates the structures that we have in the universe.

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Such as galaxies and planets and so on. It’s important for explaining nature as we said..

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Theory of relativity in some sense is incomplete. Because it [crosstalk 00:14:21]

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Interviewer: Incomplete?

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Juan Maldacena: Incomplete.

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In the sense that if you start out with some initial conditions which are reasonable, the system evolves

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and creates so called singularities. You can solve the equations.

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You find situations where the curvature of space time becomes infinite.

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This happens for example when black hole collapses.

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In the interior of the black hole, there’s a region with infinite space time curvature.

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Space time becomes so curved, and so … The force of gravity somehow becomes infinite there.

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If you were to fall in there, you would be ripped apart.

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We don’t have a theory that … The current theory is like general theory

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and particle physics do not explain what happens in that situation.

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Interviewer: Are you looking for the explanation?

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Juan Maldacena: Yeah. Those are the theories we have..

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I think maybe we can make a small bit of smile [crosstalk 00:15:25] Maybe I want to tell them to be quiet.

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Interviewer: We were at the point that you were trying to connect the theories.

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Juan Maldacena: Yeah. The Einstein theory works very well for many, many things we observe.

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The equations themselves fail in some situations. One situation is when matter collapses in a black hole.

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The interior of the black hole, we got the region with very high curvature.

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If you were to fall in there, you would be ripped apart.

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The equations don’t allow us to [the eye 00:16:02] what happens to matter when that happens.

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Another interesting situation is if you evolve the equations backwards,

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and you try to find out what happened in the very beginning of the big bang. Also the current theories don’t explain.

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It cannot explain what happened.	Again the expansion would be so rapid,

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that space expanding so rapidly you couldn’t … You cannot … The eye what happens.

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The equations themselves, the curvature becomes infinite, and the equations fail. The reason … Yeah?

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Interviewer: If I try to imagine of course what’s happening inside your head trying to connect these theories,

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what happens?

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Juan Maldacena: The main reason for these inconsistencies is the fact that they … Einstein’s theories so called

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Classical Theory, which is a good theory when things are very big.

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Basically very short distances, you have to take into account the quantum.

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The same way that matter of long distances can be described, also classically.

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When you go to short distances, you have to describe it using the quantum mechanical description.

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Space time is similar.

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When you go to very short distance in space time, you also would need quantum mechanical description.

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For matter, when we go to short distances, we go to the atoms, the elementary particles and so on.	For space time,.

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we should go again to something that will be atoms of space time. I think that the [crosstalk 00:17:35]

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Interviewer: What is that?

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Juan Maldacena: We think that we went to such a theory, we could do this. We could perhaps understand the big bang..

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Or, the situations which we cannot understand [crosstalk 00:17:46]

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Interviewer: Define the atoms of space time.

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Juan Maldacena: I can’t define the atoms of space time. We’re trying to find what they are.

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One idea that is wrong, is the idea that there would be atoms at each different locations in space, and so on.

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Space time is not like continuing matter.

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Because, one important property that was understood theoretically is that,

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when you have the number of configurations in original space time, that number configurations,

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does not grow like the volume. As it would with only matter.

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The number of atoms somehow wherever they are, of space time,

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we know that their number grows like the area of the surface.

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Rather than the volume.	That’s an interesting property of this so called atoms of space time.

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By atoms of space time I mean, well basically vague idea but I try to motivate it in this way.

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The search for a theory that describes space time at the quantum mechanical level. Using the laws of quantum mechanics.

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The laws of quantum mechanics are laws which are intrinsically probabilistic.

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That’s the main difference from the laws of classical physics.

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Classical physics, if you know the initial conditions, you can then calculate what would happen in the future..

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[crosstalk 00:19:17]

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Interviewer: Because you cannot do an experiment you mean?

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Juan Maldacena: No, in quantum mechanics you can do experiments.

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The results you can prepare the initial conditions always in the same way.

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The results of the climates will be different each time you experiment, you’ll get a different answer.

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All you can predict according to quantum mechanics is not the precise answer of the experiment,

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but the probabilities for the different answers. You do an experiment, it’s like flipping a coin.

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You can calculate and you can say, maybe I’ll get 50% one result. 50% of the time one result and 50% the other.

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Or maybe it’s 30, 70 and so on. Quantum mechanics allows you to calculate those percentages.

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Quantum mechanics doesn’t allow you to give definite answers to some questions. It is intrinsically this way.

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Interviewer: That’s a rather big question you ask yourself.

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Besides the part that you are this scientist trying to research this.

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I’m also interested why is it you asking this question? What’s your … Why do you ask this question?

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Why do you do this?

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Juan Maldacena: Certainly I’m not the first to ask this question. This question was asked many years ago.

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Probably Planck was the first to realize that there was a connection between the quantum and gravity.

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At some point gravity would fail, and calculated what distance scale you would [inaudible 00:21:01] was a century ago.

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Since then, people have had various ideas by thinking about this problem.

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It’s a problem that is hard to access it fundamentally directly.

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This distance in which the quantum is important is super tiny.

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It’s much smaller than the smallest distances we can see today will accelerate this.

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By a group of people who are trying to investigate this from the theoretical point of view,

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trying to find the structure of mathematical theory that would put these two things together.	We’re trying to do

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something similar to what Einstein did when he joined special relativity with Newtonian gravity.

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He realize that the theory of Newton was not consistent with this idea that the speed of light is the maximum speed of

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propagation of signals. That it should be the same for all observers.

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Putting those two things together, he managed to create the structure. The structure of general relativity.

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Here we are trying to replicate that from theoretical points of view,.

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try to find the connections between the quantum and space time, and [crosstalk 00:22:17].

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Interviewer: Are you sure you’re going to find the answers or [crosstalk 00:22:20]

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Juan Maldacena: No. We’re not 100% sure, but we’re confident that we have a high probability.

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The equation is so interesting, that we should try to investigate it.

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Interviewer: You know that you’re on the right path?

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Juan Maldacena: Yeah.

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What gives us some confidence that we’re in the right path is that, we’re not investigating this in the vacuum

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or without … We now have some very concrete theories. The nicest one is the theory of strength theory.

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That is a theory based on the construction that works very nicely in some situations.

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That manages to join the quantum with space time.

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Is a theory under construction, and a theory which is continued to be developed and we’re trying to understand it.

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Interviewer: Strength theory.

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Juan Maldacena: Yeah. Strength theory. It seems to connect the quantum with space time in a very interesting way.

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By investigating strength theory, people have found very interesting mathematical relations. That are true mathematics.

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They found the connections between different physical theories.

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For example, between the theory of strong interactions and some theories of space time.

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The fact that the disconnections were found,,

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gives us some confidence that at least the structure that we’re investigating is interesting and [great 00:23:56]

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and it could be the answer to this question of quantum gravity.

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Which is really the main question we’re trying to answer.

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Interviewer: Do you work in a group of people who are on the same level theoretically?

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Juan Maldacena: Yeah.

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Interviewer: How is it for you to … Now you have to explain it to me, and I don’t understand.

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You have to transfer your thoughts or your ideas to people who don’t understand.

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Because it’s so difficult even for yourself, it’s difficult. How is that?

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Juan Maldacena: Well, for us it’s difficult to find the equations,

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but I think what I’m trying to compare is the problem we’re trying to understand

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and I think the problem is understandable.

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It’s just joining two theories of physics that are out there, and putting them together.

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They are not completely compatible with each other.

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In the history of physics, when there were two kinds of theories that were not quite compatible,

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and you find a structure that puts them together, it might be the right structure.

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Interviewer: This theory might be the strength theory?

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Juan Maldacena: Yeah. The strength theory is the main tool and the main thing that we’re investigating.

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We think that it is not the right structure. It’s probably close to the right structure..

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It could be the stepping stone to the right structure. [crosstalk 00:25:25]

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Interviewer: For a lot of people, the strength theory is un-understandable,

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but you all have to understand this theory just to use it as a possible?

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Juan Maldacena: Yeah.

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Strength theory might sound complicated,

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but it’s something that someone who’s doing his PhD in physics can learn in a year, a couple of years,.

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and they can [crosstalk 00:25:47] That’s right...

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Interviewer: Maybe [crosstalk 00:25:54] Can you explain to me what [crosstalk 00:25:56]

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Juan Maldacena: There is … It’s like playing the piano.

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You’re not going to be able to play the piano in five minutes.

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Someone can tell you, oh you have to press keys and so on but you won’t be able to play the piano

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or to produce nice music.

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Interviewer: It sounds awful.

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Juan Maldacena: Here also, it takes a while to get familiar. To familiarize yourself with the ideas.

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One reason we have this is because you really have to learn a lot of the physics that precedes it.

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You have to learn well general relativity, you have to learn well particle theory of interacting particles.

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You have to do this.

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Interviewer: Isn’t it a fact that if different people from different backgrounds come together

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and discuss this strength theory, that in the event that they all know what you’re talking about,

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or understand the strength theory, doesn’t make it then true?

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Juan Maldacena: No. What makes a physical theory true, as a physics theory of physics is comparison with experiment.

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Interviewer: If you all understand the strength theory and then you think it’s true, you understand what it means,

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it took some years but different other people took some years and they understand strength theory.

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Juan Maldacena: Strength theory today is a mathematical structure.

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It’s a mathematical structure which has some physical interpretation.

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We don’t yet know whether it’s the right theory of physics.

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We think it’s in the right track, and we’re motivated enough to continue stirring it. That doesn’t make it true.

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That just makes it a very interesting mathematical theory.

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Interviewer: Can you explain to me what is meant by this strength theory?

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Juan Maldacena: Well,

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mainly strength theory is a theory which some laws that can describe space time at the quantum mechanical level.

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Using the laws of quantum mechanics. That it reduces to Einstein theory for big distances. That’s its main advantage.

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Now, maybe you are asking why is it called strength.

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Well, this comes in the fact that [man 00:28:18] formulation of the theory,

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you have little tiny vibrating loops of strength.

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Instead of having particles which are point like, as we have in theory of particles, or innate particles,

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the elementary objects are a little strengths. One dimension objects.

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That’s … Using those,

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you can describe ripples of space time interacting.	All those gravity waves that we discussed before in the experiment,

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when they interact in a quantum mechanical way. They can do so in a way that’s not generating any inconsistency.

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Interviewer: Is there a theory of your own which you are investigating or researching?

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Juan Maldacena: I’ve been researching some relationship between strength theory and particle physics.

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There’s a relationship which is part of this connections that I was describing before.

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That the strength theory led to.

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This is a connection between theories of gravity in the interior of the space time,

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and the theory of particles on the boundary of the space time.

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In this relationship, the idea is that the so called atoms of space time in the interior,

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are like particles on the boundary. That’s roughly one way to say.

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Another analogy people make sometimes is the idea of the hologram.

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That you can … A hologram is a two dimensional photographic plate.	That when you illuminate it in the light,

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you see three dimensional picture.

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The idea is that you can have the dynamics of this particle on the boundary or space time so far away.

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Can have an alternative description as objects moving in the interior. Subject to the force of gravity.

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Interviewer: The atoms of space time are reflected or projected?

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Juan Maldacena: Yeah. The real atoms would be on the boundary. The real elementary particles, another thing.

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Then we’ve got some effective description … approximate description in terms of a space time in the interior.

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In this picture, space time is … This is just an approximation.

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It’s an approximation to the dynamics of lots of particles.

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In the same way that properties of microscopic objects come from similar approximations, like the scarcity of water

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or just the behavior of water waves and so on.

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It comes from the collective motion of many of the concentrated molecules.

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Interviewer: The thing you’re explaining to me how it works this hologram again? As simple as possible.

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Juan Maldacena: This idea is the idea that you can describe gravitational physics,

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or dynamics of space time at the quantum level. Which is something we don’t understand too well how to do it.

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In terms of theory of particles. That lives on the boundary of that space time.

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The theory of particles is very similar to the theory of particles we use for particle physics.

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Or, some similar to the theory we use in the quantum mechanics. That’s a disconnection.

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It connects for example black holes, to come on systems of particles that find the temperature.

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If you assume … It’s a conjecture that these two things are related.	It’s a conjecture that people work a lot on

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and they found lots of ideas that this correct at least in very specific cases.

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It’s a conjecture a conjecture between two let’s say mathematical theories.

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One is the mathematics of strength theory in the space times, or quantum mechanical dynamical space times.

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That’s described through strength theory, and ordinary theories of particle physics.

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Many cases we can approximately describe each of the two sides, and then check mathematically that they’re correct.

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The idea is to understand this further.

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To understand better how space … What this implies for space time,

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and how to build better theories of space time.	In particular how to solve some of the problems we have with black

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holes.

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Black holes are understood reasonably well with the theory of Einstein’s … With Einstein’s theory of relativity.

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Black holes have also give rise to some quantum mechanical effects.

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More precisely once you take into account quantum mechanics.

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Black holes can start to emit some kind of radiation Hawking discovered.

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He discovered this theoretically, and it’s called Hawking radiation.

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This implies that black holes are they form, and then they start emitting this radiation.

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They emit a kind of soft glow.

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Just to highlight how surprising this radiation is,

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black holes were called black because they don’t emit any light.	Anything that goes in has to fall in

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and nothing can be emitted.

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Interviewer: Can get out?

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Juan Maldacena: Cannot get out. This radiation is something that is somehow getting out.

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You can even have the [inaudible 00:33:58] situation of having a white black hole.

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You have a black hole which is very tiny.

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The size of the wave length of light, or the size of a bacteria roughly speaking.

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That black hole will look white to our eyes. These black holes don’t form naturally in nature.

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Black holes that form naturally in nature, are very big and have a very low temperature.

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If you could form such a tiny black hole, theories predict that it should look white.

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Here you see that there’ll be little conflict between Einstein’s theory of relativity,

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in the beginning of a conflict you see it. One says it should be black, and the other one says it should be white.

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Interviewer: White hole.

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Juan Maldacena: Yeah. This is different from what people call a white hole, but this is a white black hole.

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Here you see the beginning of some slight conflict between the two, and if you go deeper in,.

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there are some laws of thermodynamics that should apply to any option that emits thermal .. This radiation is thermal.

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It gets emitted at a certain temperature. That’s why you needed to make it very small, to make it look white.

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Because the temperature becomes higher. The smaller the black hole is.

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Small black hole is hotter than a bigger black hole.

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I should make the black hole smaller,

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it gets hotter.	If you apply it with the laws of thermodynamics as we usually understand them,

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they seem to hold for such black holes.

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They are … They seem to be in some conflict with another fact that we know from general relativity.

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Which is that if you solve the Einstein’s equations in black hole, there is a surface that we call the horizon.

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Which is a surface basically right on the outside, and the inside. It’s an imaginary surface.

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It’s not a real surface. It’s kind of point of no return.

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If you cross the horizon, in the interior, you cannot send anything to the outside. You cannot even escape.

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You’ll be doomed to fall in the singularity.	You don’t feel anything when you cross the horizon.

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It’s a perfectly reasonable surface. That’s what Einstein’s theory predicts.

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This fact seems to somehow be in some conflict with this thermal properties of black holes,

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and how to fully resolve this conflict. Is one of the things I and some other people are working on.

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Interviewer: Is it something that you can call your life work?

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Juan Maldacena: I would say that I’ve been mostly investigating this relationship between the interior

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and the boundary. Also, trying to understand these problems with black holes. These problems with black holes.

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The aspects of black holes.

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Interviewer: Is this like your life researching this? Or is this just a job?

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Juan Maldacena: It is a passion and I would like to really find the problem, and find a solution to the problem.

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I hope it gets solved soon.

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Interviewer: Are you close?

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Juan Maldacena: Yeah. We seem to be close. Hopefully yes.

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Interviewer: What I try to imagine, is because it’s also theoretical. You must have a big imagination.

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When you think about it, what do you see?

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Is it … And I don’t want you to explain the theory, but how do you represent this in your head? In your brain?

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In colors, or in shapes, or in?

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Juan Maldacena: Yeah.

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Probably in terms of …By the way, we imagine formulas and their properties,

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and we make a little mental image for these formulas.

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We … For example, already for Einstein theory of relativity you have to imagine space time as some kind of membrane.

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Interviewer: How do you imagine that?

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Juan Maldacena: I imagine it same for classical space time for example, as a membrane

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and the quantum one a membrane that is fluctuating. Those are the kind of mental images that we …

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Interviewer: Sorry, a membrane?

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Juan Maldacena: Well, space time is like a membrane that has certain shape. Has some dynamics of the shape can change.

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If you get very close, this membrane has some oscillations and some structure.

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That’s what we have at short distances. That’s a picture of the smallest standard for how to think about this.

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One of the interesting things that we’ve been trying to understand and many people have begun to notice is that,

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there is some connection between a certain property of quantum mechanics called entanglement.

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Entanglement is a funny kind of correlation you can have in quantum mechanical systems.	Which in some sense stronger

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than classical correlations.

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Before we discuss the fact that in some quantum mechanical systems you cannot predict the answer to certain experiments.

418
00:39:45,05 --> 00:39:54,61
You might sometimes find 50% chance of one, or 50% chance of the other.

419
00:39:54,61 --> 00:40:00,08
You’re going to have systems where you have two particles, and they’re separated.

420
00:40:00,08 --> 00:40:03,97
You’re going to experiment here and you have 50% chance of each outcome.

421
00:40:03,97 --> 00:40:09,44
You can do another experiment here and it’s again 50% chance of any outcome.

422
00:40:09,44 --> 00:40:18,64
It might turn out that the outcomes of the two experiments are correlated.	Let’s say the experiment is like flipping

423
00:40:18,64 --> 00:40:21,17
a coin, it comes out heads here and it also comes out heads here.

424
00:40:21,17 --> 00:40:26,19
If it comes tails here, it also will come out tails here. They’re perfectly correlated.

425
00:40:26,63 --> 00:40:28,73
That’s an example of a classical correlation.

426
00:40:28,73 --> 00:40:35,44
Entanglement is the fact that you can also measure another property at the same time.

427
00:40:35,55 --> 00:40:39,72
If this coin which is not heads or tails but it’s the color, this is another analogy.

428
00:40:39,72 --> 00:40:45,16
If the property is quantum mechanical that cannot be measure at the same time as the original property.

429
00:40:47,17 --> 00:40:49,64
That’s one of the features also. Quantum mechanics.

430
00:40:50,15 --> 00:41:01,37
That sometimes you can have two properties which you cannot measure at the same time.	You can ask this coin whether

431
00:41:01,37 --> 00:41:02,55
it’s heads or tails.

432
00:41:02,55 --> 00:41:08,02
Or whether it says it’s black or white but you cannot ask where it’s black, and where it’s heads or tails.

433
00:41:08,02 --> 00:41:16,33
It’s not a perfect analogy, or a classical variables are not of this kind. They’re mutually incompatible.

434
00:41:16,33 --> 00:41:24,69
You can do that with this quantum let’s say properties, and again you can have two particles so that,

435
00:41:24,69 --> 00:41:29,64
if you now measure, not only whether it’s heads or tails, but also black or white,

436
00:41:29,98 --> 00:41:32,73
you have the same perfect correlation with the other.

437
00:41:34,15 --> 00:41:41,32
That some kind of correlation that is not possible in classical physics, but it’s possible in quantum physics..

438
00:41:40,81 --> 00:41:41,28
We think that [crosstalk 00:41:43]

439
00:41:41,32 --> 00:41:42,35
Interviewer: Even though there’s a big distance?

440
00:41:42,35 --> 00:41:45,02
Juan Maldacena: Yeah. Even though there is a big distance.

441
00:41:45,02 --> 00:41:51,33
Again, with classical correlations, we can have these correlations because the two … You prepare the two kinds first,

442
00:41:51,33 --> 00:41:56,56
and then you take them apart. Then you look at it. In classical physics, there’s no problem with this correlation.

443
00:41:58,05 --> 00:42:04,64
What is interesting is that you can have correlation between variables that are mutually incompatible locally.

444
00:42:04,64 --> 00:42:10,56
By compatible I mean that you either measure one or the other, but nevertheless you have a correlation.

445
00:42:10,56 --> 00:42:19,07
Sometimes [inaudible 00:42:17] surprising property quantum mechanics, when it was noticed,

446
00:42:19,07 --> 00:42:26,44
it was noticed in that paper by Einstein [inaudible 00:42:22] in the 1930s.	Then while this was property,

447
00:42:29,75 --> 00:42:38,24
and now it’s quite central notion for quantum information theory and people are using it in more practical ways.

448
00:42:39,31 --> 00:42:44,09
To build … I mean, it would be essential for building quantum mechanical computer systems.

449
00:42:45,51 --> 00:42:50,69
It also seems to be connected with the connections in space time.

450
00:42:50,69 --> 00:42:56,67
Things that are closer to getting space time are more entangled with each other.

451
00:42:57,92 --> 00:43:06,07
In some sense when you have the quantum field theory vacuum. The vacuum in the theory of particle physics.

452
00:43:06,07 --> 00:43:08,63
If you want to split it in two parts,

453
00:43:08,63 --> 00:43:19,45
the fundamental degrees of freedom are quantum variables that describe it.	Are quite entangled with each other.

454
00:43:19,45 --> 00:43:25,84
We think that in some circumstances if you take two separate systems, and you entangle them very strongly,

455
00:43:26,23 --> 00:43:32,63
so you could also generate some kind of quantum connect. You can generate geometric connection between them.

456
00:43:32,64 --> 00:43:47,04
In some cases. In some sense, through the entanglement is connected to the connectivity of space time. You can, yeah.

457
00:43:47,04 --> 00:43:54,8
Interviewer: I want to try to get back to the beginning again.

458
00:43:58,14 --> 00:44:10,43
Because it’s rather difficult and I doubt you told me a lot about it. I try to recapture a little bit if I’m right.

459
00:44:13,05 --> 00:44:31,39
I would like to ask you to give definitions of the ingredients. Definitions for normal people.

460
00:44:31,39 --> 00:44:35,71
What is time, what is space and what is relativity?

461
00:44:35,71 --> 00:44:44,6
Juan Maldacena: Okay, good. Let’s start with time. Time is what the clock measures.

462
00:44:44,6 --> 00:44:48,15
Now, this sounds like a circular definition,

463
00:44:48,16 --> 00:44:54,53
but of course what’s not obvious is that different blocks made in different ways measure the same time.

464
00:44:54,53 --> 00:45:01,65
It turns out if you have different kinds of clocks, and you make them,

465
00:45:01,66 --> 00:45:05,26
they will all measure the same … They’ll measure the same … They’ll give the same answer.

466
00:45:05,26 --> 00:45:10,9
That you can synchronize clocks and they stay synchronize and so on.

467
00:45:10,9 --> 00:45:14,27
It looks like there is something that is being measured by these clocks.

468
00:45:14,27 --> 00:45:17,37
This something is the abstraction we call time.

469
00:45:17,93 --> 00:45:21,83
We have the time we feel psychologically which is not a perfect clock,

470
00:45:21,83 --> 00:45:30,57
but certainly agrees with more precise physical clocks.	All clocks that measure time are made of physical particles,

471
00:45:30,57 --> 00:45:35,45
and that’s how we measure time. That’s how we define it.

472
00:45:35,45 --> 00:45:44,89
It’s an abstraction but this is the thing that all these clocks are measuring. What is space?

473
00:45:44,89 --> 00:45:54,7
Space is somehow the distance between the … Let’s say the nothingness that exists between two objects.

474
00:45:55,23 --> 00:46:07,95
Now, it’s what’s missing when you go into a crowded bus. That’s space. What’s this relativity?

475
00:46:08,05 --> 00:46:09,78
Let’s first discuss special relativity.

476
00:46:10,21 --> 00:46:15,14
Before when I was discussing time, I said that all clocks measure the same time.

477
00:46:15,44 --> 00:46:19,79
That is only true for clocks that are stationary. If you have a clock here.

478
00:46:19,79 --> 00:46:23,4
Another clock here, and both stay at rest relative to each other,

479
00:46:23,42 --> 00:46:31,54
then they will measure the same time.	If you have a clock here. Another clock moving, they will measure different time.

480
00:46:32,07 --> 00:46:37,93
Relativity, special relative that’s how different is this other time the clock measures.

481
00:46:37,93 --> 00:46:43,82
It’s a simple law for how to find out how to.

482
00:46:46,1 --> 00:46:54,1
The theory of relativity is the theory that postulates the speed of light. It’s constant. It’s absolute.

483
00:46:54,1 --> 00:47:00,62
If you could also have call it absolute something.

484
00:47:00,62 --> 00:47:05,23
What’s relative is time, but that doesn’t mean everything is relative.

485
00:47:05,23 --> 00:47:07,48
Interviewer: This envisioning what is light?

486
00:47:07,48 --> 00:47:14,8
Juan Maldacena: Well, you could replace light by other things like gravity where it’s also propagated the speed.

487
00:47:15,25 --> 00:47:20,75
More precisely, I should have said it’s the maximum speed of propagation of signals.

488
00:47:20,75 --> 00:47:26,11
The idea is that there is a maximum speed for the propagation of signals.

489
00:47:27,09 --> 00:47:29,03
So happens that light propagates at this speed.

490
00:47:29,03 --> 00:47:34,78
If you had a massive particle, it would generally propagate at a lower speed.

491
00:47:35,24 --> 00:47:38,69
If you try to push a massive particle to move it faster and faster and faster,

492
00:47:39,05 --> 00:47:45,62
you could not make it move faster than this maximum speed. Which is also coincides with the speed of light.

493
00:47:45,62 --> 00:47:47,7
Interviewer: That’s why it’s absolute?

494
00:47:47,7 --> 00:47:52,23
Juan Maldacena: Yeah. Different observers would measure exactly the same speed.

495
00:47:52,23 --> 00:48:05,1
Interviewer: Why do you want to have an explanation for how life started?

496
00:48:05,1 --> 00:48:11,32
Juan Maldacena: Well, it’s not an explanation about how life started, but how the beginning of space time started.

497
00:48:11,91 --> 00:48:18,12
How time originated and what happened at the beginning of the big bang.

498
00:48:18,12 --> 00:48:22,64
We’re trying to understand it because that’s something we don’t know.

499
00:48:22,64 --> 00:48:25,53
Science is always about pushing the boundaries.

500
00:48:26,49 --> 00:48:31,85
We don’t … It’s not just the fact that we don’t know how it happened,

501
00:48:31,86 --> 00:48:36,76
but even we don’t have a theory that is [self 00:48:36] consistent that could describe it.

502
00:48:36,76 --> 00:48:44,71
We are even trying to find theories that could in principle describe the big bang,.

503
00:48:43,26 --> 00:48:47,28
then we’ll have the problem of finding .. That’s the way the big bang actually happened.	Yeah.

504
00:48:50,02 --> 00:48:55,16
That’s why we think the problem may be solved by thinking about it, and finding the theory

505
00:48:55,16 --> 00:48:59,19
and then perhaps making some new predictions that we could test experimentally.

506
00:48:59,19 --> 00:49:06,87
Interviewer: Yeah, but all the time the same question arises again. What happened before the big bang?

507
00:49:07,1 --> 00:49:11,92
Questions like that. How do you deal with this almost impossible …

508
00:49:11,92 --> 00:49:21,41
Juan Maldacena: The idea is to make a theory, and maybe you can make a theory which has a time before.

509
00:49:21,41 --> 00:49:26,47
Maybe you can make a theory where time actually starts in the big bang,

510
00:49:26,72 --> 00:49:32,12
and does not have any meaning before … Sort of the question doesn’t have a meaning.

511
00:49:32,65 --> 00:49:38,63
We don’t know what the right answer is. That’s what we’re trying to find out with this concept.

512
00:49:38,63 --> 00:49:45,98
People imagine now maybe there was a time before, and somehow we went through a big bang. These are just words.

513
00:49:45,98 --> 00:49:52,32
They are not self-consistent equations where you can have such a thing.

514
00:49:52,4 --> 00:49:58,46
If you try to make a theory where the universe was contracting, and then expanding again for example,

515
00:49:58,87 --> 00:50:04,57
they violate some principles that we think should be true in the theory of quantum gravity.

516
00:50:04,57 --> 00:50:09,86
Interviewer: When did yourself ask this question for the first time?

517
00:50:09,86 --> 00:50:16,54
Juan Maldacena: I guess as I started learning more about physics.

518
00:50:16,54 --> 00:50:24,44
I started recognizing where the boundaries of physics were, and there are boundaries of physics in many directions.

519
00:50:24,44 --> 00:50:28,33
In the direction of very complex systems, in very different directions.

520
00:50:28,63 --> 00:50:36,6
This is one of the directions in which we see a boundary. I wanted to go to the frontier in this direction.

521
00:50:38,73 --> 00:50:44,83
I guess the physics they’re trying to roll was expanding. Push the frontier further and further away.

522
00:50:44,83 --> 00:50:47,3
Interviewer: Right now you are as a frontier?

523
00:50:47,3 --> 00:50:50,02
Juan Maldacena: Yeah. This is certainly one of the frontiers.

524
00:50:50,02 --> 00:50:53,36
Interviewer: What do you see when you look ahead?

525
00:50:53,36 --> 00:50:59,83
Juan Maldacena: I see confusion. I see lack of understanding.

526
00:50:59,83 --> 00:51:07,5
The idea is to find patterns in this confusion, and to move forward.

527
00:51:07,5 --> 00:51:12,82
To understand things that we currently don’t understand [crosstalk 00:51:11] bit by bit.

528
00:51:12,92 --> 00:51:19,94
Usually you advance one step at a time, and get a little further, and a little further, and.

529
00:51:19,94 --> 00:51:23,38
Interviewer: Do you feel something like a competitor?

530
00:51:24,46 --> 00:51:34,00
Or, something like a challenge or something which challenges some things … Some works.

531
00:51:34,63 --> 00:51:41,95
Somebody who challenges you to try to find it. Something like that.

532
00:51:41,95 --> 00:51:47,67
Juan Maldacena: Yeah. Certainly we were trying to find this answer, and we really want to get the answer.

533
00:51:48,24 --> 00:51:51,4
Sometimes you feel, sometimes its close.

534
00:51:51,4 --> 00:51:58,44
Then you realize maybe I made a mistake, and you … It’s all happening also personally,

535
00:51:58,45 --> 00:52:01,9
but within a community of researchers who’s trying to find this.

536
00:52:02,54 --> 00:52:08,21
You criticize the ideas of others, and others criticize your ideas and this way you make progress.

537
00:52:08,55 --> 00:52:10,65
Because it’s a difficult problem

538
00:52:10,65 --> 00:52:20,11
and you need the … You need insights from many people that know different aspects of theoretical phases of physics in

539
00:52:20,11 --> 00:52:22,03
general and can inform this.

540
00:52:22,03 --> 00:52:32,29
Interviewer: Is it possible to think of something like an entity who is on the other side of this frontier?.

541
00:52:29,67 --> 00:52:32,16
Or, maybe not an entity but [crosstalk 00:52:33]

542
00:52:32,29 --> 00:52:36,5
Juan Maldacena: Well, there might be another intelligence in our universe who has already figured out this.

543
00:52:36,5 --> 00:52:43,65
He has figured this out, and has understood these problems. At least it’s not known to us.

544
00:52:43,65 --> 00:52:58,84
Interviewer: When you are on the frontier like the west was [won 00:52:58] here in the United States.

545
00:52:59,12 --> 00:53:02,23
You don’t know what’s out there, but you go there and you find things.

546
00:53:03,77 --> 00:53:10,58
It’s because you didn’t know that there were Indians, and there was another Coast and another ocean.

547
00:53:10,58 --> 00:53:17,09
There is some awareness on the other side of the frontier. Only we don’t know.

548
00:53:17,21 --> 00:53:20,75
What kind of awareness is on the other side of your frontier?

549
00:53:20,75 --> 00:53:23,66
Juan Maldacena: Well, by awareness you mean the Indians.

550
00:53:23,66 --> 00:53:30,09
Well, you’re putting too many anthropomorphical things that were not present in this discussion.

551
00:53:31,32 --> 00:53:38,96
We only known intelligence in the universe, only known being that is trying to understand the universe.

552
00:53:38,96 --> 00:53:40,62
We are just expanding.

553
00:53:41,69 --> 00:53:43,17
When I say expanding the frontier,

554
00:53:43,17 --> 00:53:47,46
it’s just understanding the questions that they’re understanding laws of physics better.

555
00:53:47,46 --> 00:53:50,08
These entities are very simple things.

556
00:53:50,23 --> 00:53:54,58
One of the features of physics is that I think is amazingly interesting,

557
00:53:55,06 --> 00:53:58,32
is how simple the fundamental physics laws are.

558
00:53:58,32 --> 00:54:05,25
Of course you might say, if it takes a couple of years to understand it, and you need to study or maybe more,

559
00:54:05,25 --> 00:54:08,02
maybe you need to understand, study physics for five years to understand.

560
00:54:08,02 --> 00:54:08,41
Then,

561
00:54:08,41 --> 00:54:13,63
why are you saying they are simple?	They are simple in the sense that the actual laws that govern the emotional zone,

562
00:54:13,63 --> 00:54:20,79
are really simple. You don’t have to come up with rules and lots of books and so on.

563
00:54:20,79 --> 00:54:27,47
It’s been very different than the laws that you find in the senators,

564
00:54:27,47 --> 00:54:32,00
and people produce where there are exceptions here and there.

565
00:54:33,84 --> 00:54:40,00
Here there’s a very simple statement, and this is followed by everything we know.

566
00:54:40,00 --> 00:54:40,71
Interviewer: It’s true?

567
00:54:40,71 --> 00:54:45,65
Juan Maldacena: It’s true to the extent that we’ve been able to experimentally verify,

568
00:54:47,21 --> 00:54:53,47
and the statements have simple learning language which is unfamiliar. A language which takes a long time to learn.

569
00:54:53,69 --> 00:55:03,33
That’s what takes a long time. It’s just to learn this language in which the formula is the laws..

570
00:54:58,55 --> 00:55:03,27
Once the laws are formulated, they’re in a very simple way. Once you [crosstalk 00:55:04]

571
00:55:03,33 --> 00:55:04,73
Interviewer: Which one do you like the most?

572
00:55:04,73 --> 00:55:08,97
Juan Maldacena: Well, I think the general relativity is the most beautiful theory.

573
00:55:09,42 --> 00:55:16,64
Because it translates physics into geometry. This is a very nice theory.

574
00:55:16,64 --> 00:55:27,86
We don’t know how to make such a beautiful theory out of quantum mechanics. Maybe it will exist at some point.

575
00:55:27,86 --> 00:55:38,82
Interviewer: For you as a child for example, what led to this position you have right now on this frontier?

576
00:55:38,82 --> 00:55:40,41
Where did it start?

577
00:55:40,41 --> 00:55:47,02
Juan Maldacena: Well, as a child I was watching my father for example fixing the washing machine,

578
00:55:47,27 --> 00:55:56,32
and trying to learn how to do it myself. Again, understanding how everyday objects work.

579
00:55:56,32 --> 00:56:01,34
Like the washing machine, the car, the radio and so on.

580
00:56:01,34 --> 00:56:08,42
You learn a little bit about technology and how technology exploits the laws of physics.

581
00:56:08,83 --> 00:56:21,08
That got me interested in understanding the laws of physics which underlie technology. Seeing how far they understood..

582
00:56:17,27 --> 00:56:21,06
What things are known, what things are not known, and [crosstalk 00:56:22]

583
00:56:21,08 --> 00:56:22,72
Interviewer: How did you do that as a child?

584
00:56:22,72 --> 00:56:27,83
Juan Maldacena: Well, as a child I was mostly interested in technology and how things worked.

585
00:56:27,83 --> 00:56:36,1
Then, when I was in high school I got a little more interested in the laws of physics and chemistry.

586
00:56:35,5 --> 00:56:35,9
and [crosstalk 00:56:37]

587
00:56:36,1 --> 00:56:40,05
Interviewer: What did you do to explore as a child?

588
00:56:40,05 --> 00:56:48,83
Juan Maldacena: Mainly taking things apart and seeing how they worked. That’s basically the process.

589
00:56:48,83 --> 00:56:50,08
Interviewer: Yeah? Putting them together again?

590
00:56:50,08 --> 00:56:52,61
Juan Maldacena: Yeah. I was taking them apart, putting them together.

591
00:56:52,96 --> 00:56:56,38
Just learning how to fix the household appliances.

592
00:56:56,38 --> 00:57:09,91
Interviewer: That’s practical. I mean, if you try to find out how it’s made and why it works. Of course, I guess?

593
00:57:09,91 --> 00:57:15,58
Juan Maldacena: Right. I was always curious in understanding how things work. I mean, how does a TV work?

594
00:57:15,58 --> 00:57:21,26
How does a radio work? What’s the actual principle it uses.

595
00:57:21,26 --> 00:57:22,88
Interviewer: Do you know now?

596
00:57:22,88 --> 00:57:30,55
Juan Maldacena: Yeah. I think I know the basics. I wouldn’t know all the details..

597
00:57:27,34 --> 00:57:30,22
I guess the technology which I again [crosstalk 00:57:30]

598
00:57:30,55 --> 00:57:40,36
Interviewer: You know, you can … You know how a television works because you understand the physics inside?

599
00:57:40,36 --> 00:57:52,15
Or is it like comparing it to the laws of physics?

600
00:57:52,15 --> 00:57:58,1
Juan Maldacena: Well, the TV or any simple … Any machine,

601
00:57:59,02 --> 00:58:02,82
even simpler perhaps is better to think out the simpler machine first.

602
00:58:02,98 --> 00:58:07,78
Has different parts, and they work together to … Each part is there for a reason,

603
00:58:08,32 --> 00:58:19,18
and they work together to make the machine work.

604
00:58:19,18 --> 00:58:22,18
Most of our everyday machines are … Television is made out of electronic circuits.

605
00:58:22,18 --> 00:58:34,27
They’ll move currents around, and they do … They show the light on the screen and so on..

606
00:58:29,83 --> 00:58:33,97
That makes a television work, and you have to understand how this [crosstalk 00:58:35]

607
00:58:34,27 --> 00:58:38,54
Interviewer: Does a child who was your age did that?

608
00:58:38,54 --> 00:58:45,25
Juan Maldacena: Well, maybe I was perhaps from eight to 12 would be doing this thing of taking machines apart

609
00:58:45,25 --> 00:58:47,42
and putting them together

610
00:58:47,42 --> 00:58:51,95
Interviewer: What did your parents say about that? Don’t do it again?

611
00:58:51,95 --> 00:58:57,1
Juan Maldacena: No. My dad liked to do this himself, so.

612
00:58:57,1 --> 00:58:59,29
Interviewer: Taking things apart you learned from your father?

613
00:58:59,29 --> 00:59:01,69
Juan Maldacena: Yeah. That’s right..

614
00:59:00,34 --> 00:59:01,35
Interviewer: What [crosstalk 00:59:02]

615
00:59:01,69 --> 00:59:10,25
Juan Maldacena: My mother liked to give things fixed, so. My dad always liked to fix things.

616
00:59:10,25 --> 00:59:14,5
He was very practical, and he liked the challenge of fixing.

617
00:59:14,5 --> 00:59:14,64
Sometimes,

618
00:59:14,64 --> 00:59:22,46
you don’t know how it works so it’s nice to have to fix something that you don’t know exactly how it works..

619
00:59:19,82 --> 00:59:22,4
Then you manage to understand how it works [crosstalk 00:59:23]

620
00:59:22,46 --> 00:59:26,51
Interviewer: When you are on the road, and your car has a problem you can fix it?

621
00:59:26,51 --> 00:59:33,63
Juan Maldacena: Well, I was able to do that in the past. Now, cars got more complicated. I don’t know.

622
00:59:33,75 --> 00:59:37,68
This car hasn’t broken down recently, so I can’t tell for sure.

623
00:59:37,68 --> 00:59:48,7
Interviewer: It all started at a young age, and it’s almost you inherited from your father.

624
00:59:50,98 --> 00:59:52,55
Now you are here at Princeton Advanced Studies Institute.

625
00:59:52,63 --> 01:00:08,57
In a position where you are allowed to think as much as you can?

626
01:00:08,57 --> 01:00:14,14
Juan Maldacena: Right. I’m encouraged to think and do research all the time.

627
01:00:14,14 --> 01:00:21,33
Interviewer: Is it too simple to say that your job is thinking?

628
01:00:21,33 --> 01:00:23,66
Juan Maldacena: Yeah. It’s thinking. It’s discussing.

629
01:00:23,66 --> 01:00:30,71
Its learning what other people are thinking and reading what other people write. Trying to make a progress.

630
01:00:30,71 --> 01:00:31,64
Interviewer: Are you thinking all the time?

631
01:00:31,64 --> 01:00:38,51
Juan Maldacena: Well, I mean no. I’m reading what other people write.

632
01:00:38,51 --> 01:00:48,48
I’m listening to other people’s ideas and presentations, and discussing with my colleagues..

633
01:00:45,62 --> 01:00:48,14
We are writing formulas, and [crosstalk 01:00:51]

634
01:00:48,48 --> 01:00:56,85
Interviewer: Can you decide, now I start thinking? Or does it happen? Or, how does it work? This thinking process.

635
01:00:56,85 --> 01:01:04,44
Juan Maldacena: I guess the thinking normally you try to … This problem sounds very vague and grand.

636
01:01:04,61 --> 01:01:08,01
We try to think on very concrete problems where we can make progress.

637
01:01:08,01 --> 01:01:12,61
There are the questions that are extremely interesting, but almost impossible to solve.

638
01:01:12,61 --> 01:01:15,99
There are questions which are perhaps too easy to solve. We try to be in between.

639
01:01:16,09 --> 01:01:20,56
Try to find the most difficult or interesting questions that you can actually say something useful about.

640
01:01:20,56 --> 01:01:24,94
Lots of thinking is trying to focus on such questions.

641
01:01:24,94 --> 01:01:31,6
Try to imagine very simple toy models, or simple models where we can say something new.

642
01:01:31,6 --> 01:01:37,32
Interviewer: Maybe a few easy answers together might solve a more difficult answer?

643
01:01:37,32 --> 01:01:41,07
Juan Maldacena: Yeah. This thing that I was saying before. You do a step at a time.

644
01:01:41,23 --> 01:01:43,5
We have to figure out where we do the next step.

645
01:01:43,75 --> 01:01:48,1
Next step is in something we more or less know, but moves us in the right direction.

646
01:01:48,65 --> 01:01:52,58
From which we can get a better view of what the next step would be.

647
01:01:52,58 --> 01:02:00,94
Interviewer: When do you do your best thinking?.

648
01:01:55,94 --> 01:02:04,08
Juan Maldacena: Well, I think during the day and [crosstalk 01:02:03].

649
01:02:00,94 --> 01:02:07,7
Interviewer: Is all that you are the way [inaudible 01:02:04] For example, when you’re outside, or.

650
01:02:06,79 --> 01:02:07,58
when you’re in the shower [crosstalk 01:02:10]

651
01:02:07,7 --> 01:02:12,88
Juan Maldacena: It’s mostly I would say in my office, talking to other people.

652
01:02:14,11 --> 01:02:25,08
Normally when you talk to other people, you get new ideas.

653
01:02:20,12 --> 01:02:24,83
and usually many times ideas come together in this [crosstalk 01:02:25]

654
01:02:25,08 --> 01:02:30,81
Interviewer: Those colleagues are gone and then you have to write down the idea?.

655
01:02:29,03 --> 01:02:30,47
Or, do you have to [crosstalk 01:02:32]

656
01:02:30,81 --> 01:02:38,2
Juan Maldacena: We write them together, and we certainly write articles with other people. This is important.

657
01:02:38,71 --> 01:02:42,8
Most of my … Are with other people. We are collaborators.

658
01:02:42,8 --> 01:02:57,3
Interviewer: Yes. Once someone said it’s hard to sit. It’s hard to sit and not to think.

659
01:02:57,3 --> 01:03:03,96
It’s so hard to shut down your thinking. How do you think about that?

660
01:03:03,96 --> 01:03:04,96
Juan Maldacena: Well,

661
01:03:04,96 --> 01:03:10,99
it’s something … I guess you have to be a little obsessive sometimes to work on these problems.

662
01:03:11,23 --> 01:03:14,59
Because you want to think of these problems and you have to know other things.

663
01:03:14,59 --> 01:03:18,76
It’s easy to get distracted and think about something else. When you’re not making progress.

664
01:03:18,76 --> 01:03:25,38
If you’re trying to solve a problem and you’re not making progress, it’s easy to get distracted.

665
01:03:25,38 --> 01:03:31,66
Sometimes you need to keep trying to find solutions to that problem you initially set out to do.

666
01:03:31,66 --> 01:03:35,64
Being slightly obsessive about it. Then you can make some progress.

667
01:03:35,64 --> 01:03:36,94
Interviewer: You are obsessive?

668
01:03:36,94 --> 01:03:41,07
Juan Maldacena: Slightly, yeah.

669
01:03:41,07 --> 01:03:46,81
Interviewer: When there’s something distractive, what is your distraction?

670
01:03:46,81 --> 01:03:54,56
Juan Maldacena: Well, it could be some other interesting idea in some other slightly different field.

671
01:03:54,56 --> 01:04:06,57
Sometimes it’s good to be distracted. Maybe the problem you’re trying to solve was bad, and so it’s a balance.

672
01:04:06,57 --> 01:04:16,14
Interviewer: Or, you can say this is what you’re good at, and you make progress and solutions or answers.

673
01:04:16,14 --> 01:04:31,83
Is there also an area in which you are able to find the answers? The opposite of your talent?

674
01:04:31,83 --> 01:04:49,75
Juan Maldacena: Yeah. I’m not sure. Fashion..

675
01:04:43,14 --> 01:04:49,42
Interviewer: Yeah. You cannot describe that into one [crosstalk 01:04:50]

676
01:04:49,75 --> 01:04:51,09
Juan Maldacena: That’s right.

677
01:04:51,09 --> 01:04:56,17
Interviewer: I mean in your character.

678
01:04:56,17 --> 01:05:04,02
If you are obsessive in finding answers in this theoretical field, but it’s also

679
01:05:04,02 --> 01:05:18,09
when you find it you can write it down in one line. Then it’s true..

680
01:05:09,09 --> 01:05:17,9
Unlike political laws with all the kinds of … What is the area in which [crosstalk 01:05:17]

681
01:05:18,09 --> 01:05:21,86
Juan Maldacena: I think the process is not that you write down a formula and then it is true.

682
01:05:21,86 --> 01:05:30,01
Normally in physics, the process is that for some physical theory to be true, you have to be compared to experiment..

683
01:05:28,34 --> 01:05:29,68
Interviewer: I’m sorry [crosstalk 01:05:30]

684
01:05:30,01 --> 01:05:36,16
Juan Maldacena: It’s checked against experiment. Then we become more sure that it’s probably true.

685
01:05:36,16 --> 01:05:39,46
Can always be some other experiment that contradicts it.

686
01:05:40,02 --> 01:05:47,57
As many experiments that agree with it, you feel more and more confident..

687
01:05:43,18 --> 01:05:48,81
Interviewer: Yeah. I’m sorry to say that, then I say that it’s true [crosstalk 01:05:47] They agree on it.

688
01:05:48,81 --> 01:05:49,55
Juan Maldacena: Yeah.

689
01:05:50,04 --> 01:06:00,85
Many times … A lot of our work sometimes is to … There are some mathematical relations like … The reason for this

690
01:06:00,85 --> 01:06:08,09
is that some of our work is mathematics, is because the laws of physics are written in this mathematical language.

691
01:06:09,01 --> 01:06:16,38
Sometimes even laws which are in principle simple like this equations of Einstein, which are simple to write down,

692
01:06:16,38 --> 01:06:18,95
but they’re very difficult to solve.

693
01:06:18,95 --> 01:06:27,67
You need your computers, and with time engineers, ideas to solve the questions,

694
01:06:27,67 --> 01:06:31,78
and …Once you find for example some solution of the equation, you can check that it is the solution.

695
01:06:31,78 --> 01:06:38,92
Then it becomes a true solution. That’s an example way.	That’s where you could say, well its mathematics.

696
01:06:38,92 --> 01:06:43,2
It’s within the … If you assume the questions are the correct description of physics,

697
01:06:43,49 --> 01:06:45,36
this is a solution of the equations.

698
01:06:45,36 --> 01:06:48,72
Interviewer: Correct me if I’m wrong,

699
01:06:48,99 --> 01:06:56,41
but mathematics is like an instrument for you to understand what you need to understand. What you want to understand?

700
01:06:56,41 --> 01:07:00,7
Juan Maldacena: Exactly. Before we were talking about the language in which these laws are written.

701
01:07:00,82 --> 01:07:07,9
This is a language that is fairly mathematical..

702
01:07:04,32 --> 01:07:07,66
You need to know enough mathematics to be able to understand the [crosstalk 01:07:08]

703
01:07:07,9 --> 01:07:13,98
Interviewer: I can imagine that this mathematics, you are talented for using it.

704
01:07:15,26 --> 01:07:21,17
It’s a way to look around you and follow your obsession.

705
01:07:22,04 --> 01:07:29,11
There are also very much a lot of areas in which mathematics just doesn’t work.

706
01:07:30,47 --> 01:07:40,52
Then you … Which areas are that, that you cannot use math?

707
01:07:40,52 --> 01:07:45,17
Juan Maldacena: There are many areas I really like where we don’t necessarily use math.

708
01:07:45,17 --> 01:07:50,16
If I want to learn the piano, math is not very useful.

709
01:07:50,16 --> 01:07:56,93
Or if I want to play soccer, I learned to play soccer but math is not very useful.

710
01:07:56,93 --> 01:07:58,2
You just have to practice playing soccer.

711
01:07:58,52 --> 01:08:08,22
If I want to cook [data 01:08::01] in my lunch or cook a nice meal, math is also not very useful..

712
01:08:06,21 --> 01:08:08,01
There are lots of areas but [crosstalk 01:08:08]

713
01:08:08,22 --> 01:08:11,76
Interviewer: What are the things which you are not good at?

714
01:08:11,76 --> 01:08:17,95
Juan Maldacena: Playing soccer, and sports.

715
01:08:17,95 --> 01:08:20,92
Interviewer: Do you like it?

716
01:08:20,92 --> 01:08:22,92
Juan Maldacena: I do it sometimes.

717
01:08:22,92 --> 01:08:31,25
Interviewer: Is that an aspect of mathematics as well? That you can like it?

718
01:08:31,25 --> 01:08:36,16
Juan Maldacena: If I like mathematics because of some aspect?

719
01:08:36,16 --> 01:08:43,32
I like some aspects of mathematics because first it’s a nice tool to describe physics and,

720
01:08:44,25 --> 01:08:47,17
I certainly like it’s interesting.

721
01:08:47,17 --> 01:08:53,24
While mathematics is also a subject on its own and it’s huge, I know a little bit of mathematics,

722
01:08:53,24 --> 01:08:57,43
and I write down the mathematics I think would be useful for this problem.

723
01:08:59,53 --> 01:09:05,1
Sometimes people need to learn, invent some new mathematics to solve these problems.

724
01:09:05,1 --> 01:09:15,69
Interviewer: Yeah. For example, I’m much more comfortable when I talk to people, trying to understand people.

725
01:09:17,44 --> 01:09:20,96
I’m not comfortable when I talk with other people about mathematics.

726
01:09:21,71 --> 01:09:32,98
Because it’s not my thing, or my talent, or … I choose the things in which I’m comfortable,

727
01:09:33,32 --> 01:09:34,92
and that’s what I’m doing right now.

728
01:09:34,92 --> 01:09:39,86
I’m [firmly 01:09:36] interviewing people, trying to have that person at work.

729
01:09:39,86 --> 01:09:43,56
Juan Maldacena: Right. That’s true.

730
01:09:44,35 --> 01:09:51,41
We all know what our strengths are, and we try to do an activity where we can really use our talents.

731
01:09:51,41 --> 01:09:59,12
Yeah, certainly I would be a very bad interviewer. To know what the other person is thinking or trying to guess it.

732
01:09:59,12 --> 01:10:02,12
Yeah, we all do these various talents.

733
01:10:04,31 --> 01:10:11,5
Our natural … Well, we develop some talents and I guess through part of our lives, we continue developing them

734
01:10:11,51 --> 01:10:13,72
and we get better at those areas.

735
01:10:13,72 --> 01:10:28,27
Interviewer: Anna, told me about … Because I don’t want to forget that one.

736
01:10:29,48 --> 01:10:37,85
Two stories she told about the mountain and a valley, and about Romeo and Juliet.

737
01:10:37,85 --> 01:10:41,54
Juan Maldacena: Okay.

738
01:10:41,54 --> 01:10:52,49
Interviewer: Do you think it’s interesting to tell that? For understanding your theory?

739
01:10:52,49 --> 01:10:56,92
Juan Maldacena: Yeah. I’m trying to remember what the story about the mountain and the valley was.

740
01:10:56,92 --> 01:11:06,12
Interviewer: That if you live in a mountain … a valley,.

741
01:11:01,27 --> 01:11:05,96
and you have no reason to go up on the mountain because you cannot go [crosstalk 01:11:07]

742
01:11:06,12 --> 01:11:12,59
Juan Maldacena: Oh, yeah. This was … I think the original question was, was this useful for anything?

743
01:11:12,59 --> 01:11:19,53
Or, what are the technological applications of this research, or this area of research?

744
01:11:22,43 --> 01:11:27,04
This area of research doesn’t have a direct technological application that we know of.

745
01:11:29,76 --> 01:11:33,22
We do it because we want to know wand we want to understand.

746
01:11:34,49 --> 01:11:39,46
An analogy is that to think that we have, let’s say, a town that lives in a valley.

747
01:11:39,46 --> 01:11:44,23
The valley’s fertile and they grow corn, and their grow food in the valley.

748
01:11:44,23 --> 01:11:49,34
There’s a nearby mountain and there’s mountains surrounding the valley.

749
01:11:49,82 --> 01:11:56,19
Someone might decide to go up the mountain just to see what’s there.	The expedition of going up the mountain might be

750
01:11:56,19 --> 01:12:01,65
totally useless for growing better corn, or you’ll not plant anything nice in the mountains.

751
01:12:01,65 --> 01:12:07,74
Certainly going up the mountain might give you better view of the valley.

752
01:12:07,74 --> 01:12:12,61
Might help you understand where this valley is located. It might allow you to see another valley.

753
01:12:13,11 --> 01:12:16,51
This is not guaranteed. Maybe there are all mountains, and there are no other valleys.

754
01:12:16,51 --> 01:12:21,4
It’s certainly part of the curiosity of seeing where we are,

755
01:12:21,54 --> 01:12:32,19
and to extend the frontier to really understand better where we are sitting in the universe.

756
01:12:32,19 --> 01:12:36,21
This is one direction in which we can go and certainly that’s where we … I mean,

757
01:12:36,45 --> 01:12:39,27
it’s like a mountain that it’s there.	We’re trying to go to the summit

758
01:12:39,27 --> 01:12:49,24
and try to understand the summit is understanding the big bang singularity..

759
01:12:43,36 --> 01:12:49,14
Is understanding the beginning of the big bang. I will try to climb this mountain the whole way. [crosstalk 01:12:50]

760
01:12:49,24 --> 01:12:52,84
Interviewer: Are you on the mountain?

761
01:12:52,84 --> 01:12:55,32
Juan Maldacena: Well, we don’t know. Because we don’t have a view of the mountain from outside.

762
01:12:55,32 --> 01:13:00,02
We only know that we are climbing. I think we are confident we are climbing. We are not going down.

763
01:13:00,02 --> 01:13:02,02
There must be a summit.

764
01:13:02,02 --> 01:13:03,69
Interviewer: It’s a nice one.