Transcript

Brian Keating:
One of Einstein’s two strangest ideas, wormholes and quantum entanglement were the same idea. My guest today spent his career proving

Juan Maldacena :
that they are so called Einstein Rosen paper on the fact that the full thrashette solution contains two black holes that are connected and the Einstein Podolsky Rosen paper that talks about entanglement. And we now think that these two things are related.

Brian Keating:
My guest is Juan Maldicena, the physicist who in 1997 wrote the most sided paper in theoretical physics. The claim he just made that wormholes and entanglement are the same thing is called ER equals epr. If he’s right, the structure of space time is built out of quantum information itself.

Juan Maldacena :
The information of the things you threw in is contained in this radiation. According to general relativity it will look like the information is lost. According to quantum mechanics, we would expect it to be preserved. So there is a conflict between the two things. Quantum matter didn’t obey this property then you would be allowed to send signals faster than the speed of light. I think this is a beautiful consistency condition between the two theories.

Brian Keating:
He also told me problem in physics he’d most like to solve before he dies. The answer was not what I expected.

Juan Maldacena :
The most important problem, quantum gravity, is to understand the beginning of the big bang. That’s really the problem that I would like most strongly to solve.

Brian Keating:
Juan Alicena, welcome to UC San Diego for your second appearance on the podcast.

Juan Maldacena :
Yeah, thank you Brian. It’s a pleasure to be here.

Brian Keating:
You’re here giving the Dashen lecture all the way from the Institute for Advanced Study which I think is on Einstein Lane. Is that correct address? I’m not doxing you right to say you’re on one Einstein Lane. Here’s Einstein over here. What do you think he’d be kind of most interested to learn or if you could have 10 minutes alone with him, what would you tell him about?

Juan Maldacena :
Well, I think black holes would be probably something he would be really interested in. I would particularly want to tell him, want to ask him whether he thought that his two papers from 1935 would be related. So called Einstein Rosen paper on the fact that the full threshold solution contains two black holes that are connected. And Einstein Podolsky wrote some paper that talks about entanglement and we now think that these two things are related.

Brian Keating:
This ER equals epr, right? That’s one of the things you’re known for. Many, many things you’re known for.

Juan Maldacena :
One surprising thing would be that they are a consequence of gravitational collapse and that are naturally produced in the universe. Now in the last few years, really, in the last few years, we had lots of experimental evidence for black holes. From collisions that produce gravity waves to imaging the matter near the black hole of the black hole that is near the center of the Milky Way, to, you know, looking at stars that orbit this black hole. Yeah. So we have lots of evidence for these black holes. Now then the other surprise I think would be black hole thermodynamics. I think that would be something really interesting in the sense that there’s a connection between the laws of thermodynamics and black holes, that black holes have an entropy, they have a temperature. I think that would be a lot of fun for him.

Brian Keating:
I mean, gravitational waves, another thing he predicted that he thought would never be observed. And I think he got a paper reading rejected and then he said, I don’t want to deal with a referee. And another thing that he did, well,

Juan Maldacena :
he first predicted gravity waves, then he thought maybe they don’t exist. And then the referee said that no, they do exist. You made a mistake here. And then that’s what I say when

Brian Keating:
people say peer review is bad, it’s harmful to someone else.

Juan Maldacena :
I mean, this case was a good example of useful. Well, I guess you got a good reviewer.

Brian Keating:
That’s right, yeah. That led to multiple Nobel prizes at Halse and Taylor and then LIGO and who knows what else it’ll do. But yeah, I always tell my students aspire so that your blunders or things you don’t think will ever work will lead to multiple Nobel prizes.

Juan Maldacena :
Yeah, yeah. And the cosmological constant, that was his biggest blunder. Yeah. Now it’s a central part of cosmology.

Brian Keating:
So I want to talk today about the realities of black holes and of things like the holographic principle, which is one of again, many things you’re known for in your amazing career. I was talking to a non scientist, but a very smart layperson and he was asking me, well, you know, if the holographic principle is correct. You know, some people say, well, we might be living inside of a black hole and things like that. But I always point out, you know, there’s no such thing as isolated hydrogen atom floating around the universe that truly can be solved by the Schrodinger equation. In other words, there’s always perturbation. To my knowledge, there’s no such thing as a Schwarzschild black hole either. Right. That’s perfect.

Brian Keating:
There’s occur black holes, we know of the ergosphere surrounding them. So in what sense is the holographic Principle of the fact or, or proposition that we could be living in is that just pure theoretical. Because of the realities of real black

Juan Maldacena :
holes, the holographic principle as applied to our universe, we don’t know whether it’s correct or not.

Brian Keating:
Could you explain the holographic principle? First?

Juan Maldacena :
The holographic principle is the idea that you can describe quantum gravity in some region of the universe by some theory of ordinary quantum mechanics that lives in the boundary of that region. It remains a big idea formulated this way. Now in some special cases, some special universes, so universes which are infinitely big and so on, then we can go to a surface that is very, very far away and define there a very concrete theory that whose laws of physics we can define. And in that case they are supposed to describe the interior of those universes. Those universes are not the universe we live in. They have slightly different. Well, they have different laws of physics. They have a different value for the cosmological constant.

Juan Maldacena :
But in those universes there is a lot of evidence that this relationship is true. Now there in those universes, you can consider black hol holes that are inside this universe. The black holes can have perturbation matter around. And the idea is that those would be described by the theory that lives on the boundary. And there are some comparisons we can make. One, let’s say catch or one thing that makes it hard is that the theory that lives on the boundary involves strongly interacting particles. And so it’s not completely obvious how to solve this theory. So you have to apply some techniques.

Juan Maldacena :
There are some things you can calculate, but not everything you would like to calculate. So that’s in order to compare the two things. And we are learning more on how the dictionary gets built between this quantum description on the boundary and the gravity description in the interior.

Brian Keating:
When you say lives on the boundary, what does that mean? Is that like a separate Hilbert space

Juan Maldacena :
or lives in the boundary means that these are particles that move on space which has the geometry of the boundary. It doesn’t have the extra dimension. And the idea is that you can think in two alternative waves. Either you have particles that live on that boundary, or you have the gravity description that lives in the interior. And the idea is that these particles are strongly interacting and the gravity description is some kind of emergent property. It’s not something that was there in the very beginning in the formulation of the theory, but looks like it’s an approximation to the underlying dynamics.

Brian Keating:
Does that gravitational theory, does that produce GR or something different?

Juan Maldacena :
So the idea is that when these particles are Strongly interacting and some special cases that we understand and would produce general relativity. In fact, in the examples we understand it produces general relativity plus string theory also at short distance. So there is some approximation where it’s just general relativity with some particular matter content and then also strains and stuff like that. Those are in the cases we understand. We don’t know whether string theory is necessary for this discussion or whether this is valid more generally. Or maybe string theory is the only way to quantize gravity. Those questions we, when we can remain

Brian Keating:
agnostic, will it produce, you know, excitations and things like the fermions, you know, three.

Juan Maldacena :
Yeah, you can have fermions, you can have all that.

Brian Keating:
When you said strongly interacting, does that mean like the strong force or does this mean like short range interaction?

Juan Maldacena :
By strong interaction, I mean that the coupling between the particles is very strong. So that if you have two particles that collide, they very, they will scatter very, very easily. The strong interactions are called strong because precisely they, the interactions are strong at the level of, let’s say, inside the proton and so on. And in addition, the type of particles that we have also have interactions similar to the strong interactions. The so called gauge theory. It’s a type of interactions that involves the property, let’s say, called color, which is a type of charge, but of which the sign is not just plus minus. But there are like three different types of charges in nature. There are three different types in these theories we consider there is a large number of types.

Juan Maldacena :
There are theories somewhat similar to the theories we have in nature, but not exactly the theories we have in nature. What we have are some examples of this involving this, let’s say the aershast theories and models. You could say it’s a model of quantum gravity. And one of the advantages of this description and the reason that it was developed was that it could give a full quantum description of the gravitational space time. So we don’t just get general relativity, but the quantum version of general relativity. And we hope that by having these models we will understand the quantum gravity more. And then eventually, of course, the objective is in the end to understand quantum gravity in our own real world. So somehow to extract lessons from this, to be able to apply them to our real world, you know, just at

Brian Keating:
a basic layperson level, you know, not going to do this, but you know, take your laptop, you’re going to be speaking later. Throw it into a black hole. What happens and does it depend on what type of black hole it is?

Juan Maldacena :
If you throw anything into a black hole? Well, Your laptop and so on, it will fall and you will lose sight of it. So the time it takes light for going a distance of order the size of the black hole, all the information about that laptop is effectively lost to you. So in the sense that you will not see it anymore, and any perturbation you had of the metric that was due to the fact that there was a laptop will be lost. So the influences decrease exponentially fast. Okay, this is fine. This is what happens with classical black holes. But as we were saying before, black holes have some entropy. And entropy in physics, we interpret it as arising from statistics.

Juan Maldacena :
And it’s a measure of how many states the black hole can have, how many, if you wish, bytes can be stored in this, or qubits can be stored in this black hole on the

Brian Keating:
surface or on the volume.

Juan Maldacena :
Well, the formula for the entropy is just the surface. So then you might be tempted to say it’s in the surface, but in the classical solution, the matter falls in and goes into the black hole. So you could be free to say it’s in the interior. What that somehow suggests, this picture, that the black holes have a finite amount of entropy, is that that information is not completely lost somehow. In fact, when you throw in the computer into the black hole, the area, the mass of the black hole grows a little bit and the area grows a little bit, and the entropy becomes larger. It becomes larger by an amount which is bigger than the entropy that was, than the amount of information that was in the, in your laptop. And you can use the laws of physics to show that this is always the case. Whenever you send something into the black hole, the entropy always increases.

Juan Maldacena :
The question is, is this lost forever or not? In principle, you could say it’s lost forever. And you might think because the, you know, goes into the black hole and then, well, never come out, according to classical physics. But the new aspect is that these thermal effects in particular, Hawking radiation, implies that the black hole will emit something, emits some radiation that in the first approximation is thermal and carries no information. But it’s saying that the black hole will start losing mass, so it will get smaller, and eventually the black hole might perhaps disappear completely and become get some radiation. And you could wonder whether the information of the things you threw in is contained in this radiation. Now, if it is contained, it will be contained in a very subtle way. But the question is whether, in principle, it’s contained. The reason we’re asking this question is not because we are desperate to find this information, but we are a little bit Desperate, but the reason we are desperate is just that, because it’s a problem that will force us to understand quantum mechanics and gravity together and how things work.

Juan Maldacena :
Because quantum, according to general relativity will look like the information is lost. And according to quantum mechanics, we would expect it to be preserved. And so there’s a conflict between the two things. And we hope that by solving this conflict, we will learn better quantum gravity. The most important problem of quantum gravity is not the black hole information problem. No, the most important problem, quantum gravity, is to understand the beginning of the Big Bang. So understand what happened in the very beginning. That’s really the problem that I would like most strongly to solve.

Juan Maldacena :
Right. But the black hole information problem has the advantage of in more concrete problem and that we have some tools to address it. So that’s why there is effort and progress in this problem.

Brian Keating:
And getting back to my question about real black holes that aren’t static, that have charge, that spin, is that true? Is it also true that, you know, you get the exact same Hawking radiation, or if not in a maximal Kerr black hole. So we should say what that is. But in a black hole with an ergosphere like interstellar, you know, think about gargantua, real black holes, do they have the same phenomena?

Juan Maldacena :
The question is whether real black holes are emitting Hawking radiation. The problem is that the temperature for real black holes that we’ve known, we know they exist. They have masses of order solar mass or higher. Those black holes have a temperature which is very small, many orders of magnitude smaller than the temperature of the cosmic microwave background. So even if the black hole didn’t have any matter swirling around, which they do, and that matter is at even higher temperatures, even then, even just the cosmic microwave background would be swamping the Hawking radiation in the sense that the cosmic microwave background would be falling into the black hole and the Hawking radiation would be a tiny effect. So the answer is no. For the big black holes. Hawking radiation is an irrelevant phenomenon.

Juan Maldacena :
And it of course hasn’t been observed and there is little. Well, it’s probably not going to be observed anytime in the foreseeable future for astrophysical black holes. This would make you think why people think about Hawking radiation if it is such an irrelevant thing. But I would like to point something out which is that this phenomenon of Hawking radiation inspired the theoretical development of discovery of some other phenomenon, which is the generation of fluctuations in an expanding cosmology. So in a black hole, there is a horizon or there is a region. You can’t observe and can access. And that’s somehow ultimately responsible for this thermal effects. If you live in a universe that is expanding fairly rapidly, like as we think it was during the early epochs of inflation, then you expect a similar thermal effect.

Juan Maldacena :
And that temperature and the associated phenomenon will change the properties of the inflaton and will produce fluctuations in the shape of the inflaton. And we think that that’s the leading theory for the generation of the primordial fluctuation. So the fluctuations that make the universe not perfectly uniform. So the universe is somewhat uniform at large scales, but not perfectly uniform. Well, as you know very well, you’ve been studying this in homogeneities for. During your whole career and made wonderful discoveries. But it’s ultimately a similar. We think they also arose from quantum fluctuations, and it’s the same phenomenon as Hawking radiation.

Juan Maldacena :
So in this case, learning something for black holes. So Hawking’s paper was earlier than the papers that discussed this phenomenon in inflation, helped us understand something about cosmology that now forms part of more or less standard cosmology, I would say. And we similarly hope that understanding these other aspects of black holes will help understanding, you know, earlier epochs of cosmology.

Brian Keating:
Right.

Juan Maldacena :
So in some sense, the idea that phenomena discovered for black holes could be helpful for cosmology has already happened and we hope to repeat this. That’s our hope.

Brian Keating:
Hold on to that, because what Juan just said about black holes accidentally gave cosmologists the equation explains what the universe has structure at all. That’s not a small footnote. And that’s where I come in.

Brian Keating:
We’ve only discovered black holes with much more large masses than the sun, and yet the ones that are most likely to produce observable Hawking radiation are the small ones. And I kind of always meant to me, you know, for people that conjecture that, say, primordial black holes could be dark matter or could have truly existed since the dawn of time, basically, that sort of is hard to reconcile. So what do you make of attempts to solve the missing matter problem and even recently solve some dark energy phenomena using black holes, basically, which may or may not be primordial from the particle

Juan Maldacena :
physics point of view and from the model building point of view, they are not the most. I would say they are not the most natural thing or not the simplest thing you could think about. And for dark matter. So there are maybe other particle physics ideas that might seem more likely, but. Well, we’ll see. I mean, maybe, maybe they are. And of course, if dark matter is black Holes in the range where they are allowed, then Hawking radiation would be relevant. So I mean would be present and would be bigger, the temperature would be higher than the CMB temperature.

Brian Keating:
You are known and kind of remarkable to me because you study things at the forefront of theoretical physics, but you also aren’t afraid to take on philosophical kind of discussions. And one of the papers I think read from 2024 is called real Observers Solving Imaginary Problems paper. What is that? What was the purpose of that paper? And I want to talk later about your, your Beauty and the Beast paper. You have such great titles.

Juan Maldacena :
That paper had to do with computations in the cetar space. More precisely, it is sometimes useful to consider the Euclidean version of some space times. Euclidean version is basically you take the usual universe and you make the time, you change the sign in the metric in the time direction and that makes a space which is purely spatial. And in the case of an expanding the cetar universe, that is a sphere, so you can consider Einstein gravity on a sphere, we would expect that type of universe to be computing the thermodynamics of the sitter space. The reason is the following, that evolution in imaginary time, or this procedure I’ve just mentioned is useful because if you solve that evolution, you are basically calculating the thermal partition function or you’re calculating thermodynamic properties of the system. This is something that is true for any physical system. And if you do that for the sitter space, you would expect that it should be telling you about the thermodynamics of the sitter. Now, this is not a new idea.

Juan Maldacena :
This idea, well goes back to Gibbons and Hawking. If you do that, then you get that this theater space has some entropy, which is the area of the horizon. So formula very similar to the black hole entropy formula in that paper was the same time as they discussed also the same thing for black holes. Now all of this is perfectly nice and so on, but if you calculate the first quantum correction, so calculate not just the Einstein action for the sphere, but also the quantum fluctuations, including the quantum fluctuations. The quantum fluctuations they would give a negative value for the partition function. So the number of states would be negative and depending on the dimensions. In some cases it’s imaginary I to the power of the number of dimensions of space time. So this was something confusing that was found by.

Juan Maldacena :
But I think Hawking already noticed that there were some issues with some sign. Polchinski calculated more precisely what the sign is. More recently with trying to understand better the physics of the sitter space. It was understood that in order to construct the Hilbert space, it was useful to include an observer, so that you include an observer. And the degrees of freedom of the observer were important, some of the degrees of freedom to define the Hilbert space. And so what that paper did was notice that if you don’t consider just a sphere, but the sphere with the trajectory of a particle, then there are some other minus signs from the trajectory of these particles or some other I’s that cancel the. And then you get something nice and positive. Well, actually, in the paper, I originally got something positive.

Juan Maldacena :
Then Victor, I was a student of mine, pointed out a mistake. Then I got something negative. And then eventually a group from Stanford, with Douglas Stanford and collaborators, they found another mistake. And so now it’s positive. So it’s a triple negative. Yeah, triple negative. Well, that’s how many things work in science.

Brian Keating:
I remember reading A Brief History of Time. I started reading it in high school. I couldn’t finish it until I. In fact, I didn’t finish it until about five years ago. But it was a good thing I didn’t because I don’t think I could have understood kind of what he was doing in that book until much, much later. But one of the things, when he brings up this, you know, kind of what’s called a wick rotation, right?

Juan Maldacena :
Yeah.

Brian Keating:
He brings it up and he says, well, imagine we’re just going to build this as a trick. You know, we’re just going to do a trick. We’re going to introduce imaginary time, you know, the number square root of negative one in front of the time component. And when we do that, it’s called a wick rotation. And then we can solve all these things as if it’s taking place in Euclidean space. So it’s, it’s. But don’t worry, dear reader, it’s just a simple. And then the rest of the book is just basically assuming that’s true.

Brian Keating:
And then he goes on to say, and then we’ll have the mind of God. What do you make of this? I mean, what is the reality of it? I guess I’m asking Wigner’s question, why is math so useful? One thing that always blows my mind, and I try to impress it on my students, is in classical mechanics, we have Lagrangians, we have Poisson brackets. You can do all sorts of things. If you take a Poisson bracket and commutation bracket, you get the product of these things and they cancel out. The Poisson bracket for classical observers is zero. But if you, if you say it’s quantum mechanical you do the commutation relation, you get the square root of negative one and all of a sudden all of quantum mechanics can emerge from it. It’s sort of bizarre, right? At what level are these things tricks? I mean, when you see the imaginary number and you talk about in this paper, is it real? Maxwell’s fields have imaginary solutions too. They’re not real, but we can observe only real things.

Brian Keating:
So where does a person go with this?

Juan Maldacena :
I like a story that apparently Lorentz, so that’s the same person of the Lorentz transformations, he was tasked with calc how water gets into the various canals and how to design some dams and so on. So some people, they wrote a report on how this should be calculated. And in the beginning of this report he says, well, we are going to use complex numbers, but it’s just a trick at the very end, all the heights of the water and so on are going to be real, don’t worry about it. And I guess at the time it was thought it would be necessary to explain this point. Now, any engineering student that uses complex numbers to solve these type of problems with oscillations and so on, and yeah, well, it’s a trick, but it’s a trick that simplifies. In that case, it’s a trick that simplifies the calculation. And in this case maybe similar. So everything we measure, we always measure real numbers.

Juan Maldacena :
And so the imaginary numbers, that’s how they were invented for discussing the roots of polynomials and so on. But they are useful tricks. And I. Yeah, but it’s true that it’s a trick that is used so often and so much that it seems that there is something deep about it

Brian Keating:
when we think about all the other mathematical structures. So you start off with the square root of negative one, you get quantum mechanics, you get all sorts of interesting phenomena. Then you have spin 1/2 particles can be described by these SU 2×2 matrices that are complex. And then later you can have su, you can have quaternions, and then I think there are octonians. But then nothing like people obviously could keep going, right? All powers of two. But does anything correspond to whatever hexasexadecimal D?

Juan Maldacena :
Well, the problem is the complex numbers have many of the properties of ordinary numbers. And once you start going to these other ones, they don’t have all the properties of ordinary numbers and you start losing some of the properties. So they become, I would say they become less useful. I mean, quaternions were invented and they could be useful for describing rotations in space, but they are not used that much. I mean, it’s not something I. I’m not sure whether engineers use it, for example, for this purpose.

Brian Keating:
I think they’re using like AI and some AI applications, I guess for rotation.

Juan Maldacena :
Yeah. Well, maybe they’re used for some things. I wouldn’t.

Brian Keating:
I want to talk about one of the things you’re most known for. When I was getting my PhD, you know, in late 90s at Brown, I remember some conference and everyone’s so excited and at the end they did the Macarena, but they called it the Maldicena. Take us back to those times. About this ADS cft, what is it? How did you come upon it? Give us the origin story.

Juan Maldacena :
Well, adsft is this connection between universes which are large and with negative cosmological constant. So that’s an ADS anti de sitter space time. So the CETR is the one with positive cosmological constant. This is with negative cosmological constant. And CFT is a type of field theory. So field theory is theories that we use to describe relativistic particles and conformant means it has some scaling symmetry. And the idea is that these two are connected. It’s this instantiation of this holographic idea.

Juan Maldacena :
So it’s a concrete example. Yeah. So that conference took place after this paper and after people had well worked on it and there are many other interesting properties. And so Jeff Harvey wrote this song. I mean the Macarena was the song that was popular at the time.

Brian Keating:
What do you say to people that often have said the mathematics like with string theory is beautiful, but we certainly don’t seem to live in ADS space. So is it just pure again, like a wick rotation? Is it something that we should use as a useful tool or could it describe reality and we just haven’t found evidence for it?

Juan Maldacena :
Well, we made a sign error, of course.

Brian Keating:
Okay, typo. We got to retract it. Paper is zero citations.

Juan Maldacena :
Yes, yes. So the cetar space is much closer to our universe. And I would very much like to have something. I mean everyone would very much like to have something like this in the Cedar space. And hopefully understanding the anti de sitter case will be useful for understanding the de Sitter case. I hope that the understanding of the de Sitter case would have happened already and I hope it will happen soon. But maybe we’ll need maybe a new conceptual idea. So people who say that this is not the physical universe are correct.

Juan Maldacena :
But you know, we hope it’s close enough that we can extract some lessons.

Brian Keating:
The other thing we talked about briefly in our last conversation four years ago. I can’t believe it was wormholes and even humanly traversable wormholes. What is a human traversable wormhole? What good is it other than for solving a lot of issues in Hollywood, where you’re off to tomorrow.

Juan Maldacena :
Yeah. Before I discuss what the wormhole is. So, in Einstein theory, the structure of space time is dynamical and curves. So the space time can be deformed, Right? Okay. So it can be deformed a little bit. And, you know, when Einstein developed his theory, he thought, okay, these deformations will be small. Then there were some even larger deformations, like black holes. And, okay, that’s more drastic thing.

Juan Maldacena :
But then you can have some other types of deformations where you drill a hole in space time and you connect to another region of space. So you can have, for example, a space time like this. Imagine a membrane. You dig a hole in these two portions of the membrane, and you somehow connect them, but you connect them through a tube that is not embedded in this spacetime. It’s just a very short tube.

Brian Keating:
My Klein bottle over there.

Juan Maldacena :
Yeah. Something exotic like this. So, and the question is, are these configurations allowed? Are they possible in general relativity? Science fiction authors love it because you could go in one end and come out in the other, and you could travel faster than the speed of light, for example. This is something that they could allow if they were possible. But it would be a little funny because the structure of special relativity and general relativity is based on the idea of a maximum speed for propagation of signals. In general relativity, you are not allowed to put any space time. So you’re not allowed to say, oh, I have this space time. You have to obey certain equations.

Juan Maldacena :
And the equations roughly say that the curvature of your space time should be equal to the density of matter. Then you can say, okay, fine, if I want to build some space time, I just put appropriate matter, and then I will be able to have any space time I want. But then there is a catch. Because matter has to obey certain properties, you cannot have matter, let’s say, with negative energy or things like this. At least in classical physics, you can’t have that. And once you put in that constraint on the types of matter you are allowed to have, then you forbid this type of worm. The wormhole’s attack would allow you to propagate faster than the speed of light. That is also forbidden in the full quantum theory.

Juan Maldacena :
In the quantum theory, we think that in quantum mechanics, you are allowed to have a little bit of negative energy, but not Enough to have a wormhole that would allow you to travel faster than the speed of light. So those type of science fiction wormholes are not allowed according to the laws of physics as we know them. And this is not something that depends on the detailed structure of the standard model, but is something that depends on relativistic quantum field theory. So the principles of relativity, which are the principles on which this whole picture of space time is based, and the principles of quantum mechanics, they do not allow such a thing. I think this is a beautiful consistency condition between the two theories because the, and this issue with this wormholes, which is some property of general relativity, they depend on some quantum property of matter. If quantum matter didn’t obey this property, then you would be allowed to violate the, you would be able to send signals faster than the speed of light, creating these wormholes. So those are not allowed. And this is a nice theoretical result, important theoretical result, but this does not forbid wormholes that, where it would take longer for you to go, right? So you could imagine a non trivial topology where there are two holes and they’re connected by a long tube.

Juan Maldacena :
And it takes you longer to go through the tube, at least I’ve seen from someone outside, than the time it takes to go between the two mouths. And recently it became possible to construct some solutions that are of this kind. So they require certain types of matter, in particular charged fermions, which are massless and so on. So they could exist as solutions at very microscopic scales where you can approximate the Fermi of nature as being massless. Those would be very tiny. Or you could say, well, I have some very special type of dark matter that is dark matter specially designed to make wormholes. And then you could have a very, very big wormhole that could be humanly traversable, that the person can traverse meter scale, Right? Yeah. Well, to make them this way, you need them to be actually much bigger than meter scale.

Juan Maldacena :
And, and the reason is kind of interesting. It’s because. So these are structures where there is some space time curvature and we are quite sensitive to tidal forces. So you need them to be roughly the size of the Earth for it not to kill you when you are traveling.

Brian Keating:
Well, that’s beneficial. We could transport whole planets. Why stop at astronauts when you can have all people?

Juan Maldacena :
That size is just so that the curvature is small enough that they would not kill you.

Brian Keating:
Ah, right, I see. If you and Einstein were together in 1983, 1913 or 1911, say after his happiest thought about falling on an elevator and experiencing no gravitational field, and you gave him an LLM and a GPT and a gpu and you had the most powerful system. Do you think he could have come to? Or you guys together could do stuff that you couldn’t do without an AI? In other words, someone operating at the highest levels of theoretical physics. What level of. I mean, I use LLMs all the time, but I don’t see them creating new physics anytime soon.

Juan Maldacena :
Well, we’ll see. We’ll never say never. The field is advancing quickly and we’ll see. We’ll see what happens.

Brian Keating:
Yeah, I was an altar boy in the Catholic Church in Westchester county, actually in Chappaqua, New York, where the Clintons now live, as it turns out. And I loved it. I thought it was awesome. It was 1984, 1985 and. And then the Pope, John Paul II, who was in my opinion the greatest Pope in history, maybe I loved him. They came out with a decision that Galileo was right, but they never really forgave him. And I understand that you remember that Catholic Scientist Society. How do you reconcile.

Brian Keating:
Do you feel like there’s a tension? I always thought they should just say he was right, he was pardoned. How do you reconcile the so called kind of tension between science and religion?

Juan Maldacena :
I think, yeah, the Galileo was a very. Galileo thing was a very unfortunate case. But there are, well, there are many other cases of scientists that reconcile their faith with their. And we’re talking about cosmology, for example. Lemaitre, who was one of the people who created the Big Bang theory, he was a priest and he reconciled. So I think there isn’t a fundamental issue, but as science progresses, we have to change how we understand religion or we. And also religion can illuminate some scientific. Well, not some scientific questions, but some issues that arise because of science.

Juan Maldacena :
Right, Yeah, I know we have now very powerful weapons and we have some responsibilities that are very important. Very moral responsibilities.

Brian Keating:
Yeah. And how to adapt. People are so obsessed with artificial intelligence, but I kind of feel like we need artificial wisdom. Like intelligence is in plentiful, but somehow it’s more important to get wisdom. And I don’t see science providing wisdom. It provides knowledge. I mean, that’s what science means in Latin. Right.

Brian Keating:
But it doesn’t mean wisdom. So yeah, from my perspective, they can be partners, you know, science and religion, I don’t see them as foes or in opposition. But yeah, people that try to derive one from the other, like prove that the Big bang happened using the Torah, you know, using the Bible. I think that’s not great.

Juan Maldacena :
When the cosmic microwave background was detected. So the pope wanted to say actually that now we saw the beginning of the universe, the hand of God and so on. And Lemaitre told him, don’t wade into this. Just don’t say anything because,

Brian Keating:
yeah, that’s right, it could change. And back then they thought the earth was older than the universe. That was quite embarrassing. Well, let’s see. We got to get you to your talk, but before we do, I have a gift for you. Not a Nobel prize, but it’s called the Keating Prize. It’s not too arrogant of me. So it has Arthur C.

Brian Keating:
Clarke on the front because the podcast comes from him and it says the Keating Prize for impossibly good imagination. And then a meteorite which is a fragment of the early solar system that somehow magnetically attaches to the monolith on the back and has your name on the side. Juan Maldivesena. Thank you so much for coming to see you.

Juan Maldacena :
Enjoy. Thank you very much.

Brian Keating:
And then you’ll add it when you win the Nobel Prize. You could add them together.

Juan Maldacena :
Right, Right.

Brian Keating:
Great. Thank you so much for being on. And stay tuned. Watch the lecture on black hole entropy and thermodynamics coming up next.

Brian Keating:
Juan told us today that he thinks the structure of space time is built out of quantum entanglement and that the deepest problem in physics isn’t black holes, it’s the big bang. Now, if that changes how you think about reality, reality. Hit subscribe and turn on notifications. Drop a comment, let me know what problem you think Einstein would most like to see solved if he came back. And you’ll want to go deeper. And check out Juan’s two part lecture on my second channel, Keating Experiments. I’ll link down here. And if you want to go deeper, you’re going to want to watch my conversation with Leonard Susskind talking about the black hole wars using the language that he and Juan invented.

Brian Keating:
The link is right here. Don’t forget to like, comment and subscribe and I’ll see you next time.