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Cumrun Vafa

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2021-07-26

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2021-07-26

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1. “Fises looked like this one. That's intriguing. It has the symmetry, all right? But what is this? Where is this coming from? Which kind of physics gives you this? So I don't know. A few years later, people saw that, oh, the equation that you write is the process you're writing in the intermediate channels that pargos come together seems to have all the harmonics. Harmonic sounds like a string. Let me see if what you're describing has anything with its strings and people try to see if what he's doing has anything to do with his strings and say, oh, yeah, indeed, if I study scattering of two strings, I get exactly the formula you wrote down. That was the reinterpretation of what he had written and the formula as a strings. but still had nothing to do with gravity. It had nothing to do with resolving the problems of gravity with quantum mechanics. It was just trying to explain a process that people were seeing in hadronic physics collisions.”

   2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

2. “Said, I don't know what it is. What's the reason that these colliders and experiments we're doing seem to have the symmetry? But let me write a mathematical formula. Exhibits that symmetry. He used gamma functions, beta functions, and all that, you know, complete math, no physics, other than trying to get symmetry out of his equation. He just wrote down a formula as the answer for a process. Not a method to compute. Just say, wouldn't it be nice if this was the answer?”

   2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

3. “Because it wasn't like somebody said, Well, let me solve the problem of Einstein that Feynman had with unifying Einstein's theory with quantum mechanics by replacing the point by a string. No, that's not the way the thought process. The thought process was much more random. Physicist, Venetiana, in this case, was trying to describe the interactions they were seeing in colliders and accelerators. They were seeing that some process in some process when two particles came together and joined together and went they were separately in one way and the opposite way they behaved the same way. In some way there was a symmetry duality which she didn't understand the particles didn't seem to have that symmetry.”

   2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

4. “But it turns out having this size, being able to oscillate, get bigger, turn out to be resolving these puzzles that Feynman was having in calculating his diagrams, and it gets rid of those infinities. So when you're trying to do those infinities, the regions that give infinities to Feynman, as soon as you get to those regions, then the string starts to oscillate and these oscillation structure of the strings resolves those infinities to finite answer at the end. So the size of the string, the fact that it's one-dimensional gives a finite answer at the end, resolves this paradox. Perhaps it's also useful to recount of how string tearing came to be.”

   2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

5. “Very small. So we basically think from far away string is like a point particle. And that's why a lot of the things that we learned about point particle physics carries over directly to strings. So, therefore, there's not much of a mystery why park of physics was successful because a string is like a particle when it's not straight.”

   2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

6. “Much smaller. So we think if you let the string to be by itself the lowest state, there will be like fuzziness or a size of that tiny little circle, which is like a point. About could be anything between, we don't know the exact size, but different models have different sizes, but something of the order of 10 to the minus, let's say, 30 centimeters. So 10 to minus 30 centimeters just to compare with the size of the atom, which is 10 to the minus 8 centimeters, is 22 orders of magnitude smaller.”

   2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

7. “So, in other words, it's a loop of energy, so to speak. You can think of it that way. And so there's a tension, like regular string. If you pull it, there's, you know, you have to stretch it. But it's not like a thickness, like you're made of something. It's just energy. It's not made of atoms or something like that.”

   2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

8. “A more massive harmonic. This is a less massive. So, the lightest harmonic, so to speak, is no harmonics, which means like the string shrunk to a point. And then it becomes like a massless particles or light particles like photon and graviton and so forth. So when you look at tiny strings which are shrunk to a point, the lightest ones, they look like the particles that we think they're like particles. In other words, from far away, they look like a point. But of course, if you zoom in, there's this tiny little circle that's there that's trying to almost a point.”

   2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

9. “So string theory is the idea that the fundamental entities are not particles, but extended higher dimensional objects like one-dimensional strings, like loops. These loops could be open, like two ends, like an interval, or a circle without any ends. And they're vibrating and moving around in space. So how big they are? you can of course stretch it and make it big or you can just let it be whatever it wants it can be as small as a point because the circle can shrink to a point and be very light or you can you know stretch it and becomes very massive or it could oscillate and become massive that way so depends on which kind of state you have in fact this trink can have infinitely many modes depending on which kind of oscillation it's doing like a guitar has different harmonics string has different harmonics but for the string each harmonic is a particle so each particle will give you ah this”

   2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

10. “But that cannot be the case because gravity is in our universe, quantum mechanics in our universe, they both together somehow should work. So it's not acceptable to say they don't work together. So that was a puzzle. How does it possibly work? It was left open. And then we get to the string theory. So this is the puzzle of quantum gravity. The particle description of quantum gravity fail”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

11. “Formulas seem to make sense, but he had to do some integrals, and he found that when he does those integrals, he got infinity. Didn't make any sense. Now, there were similar infinities in the other pieces, but he had managed to make sense out of those before. This was no way he could make sense out of it. He just didn't know what to do. He didn't feel that's an urgent issue because nobody could do the experiment, so he was kind of said, okay, there's this thing, but okay, we don't know how to exactly do it. But that's the way it is. So in some sense, a natural conclusion from what Feynman did could have been that gravity cannot be consistent with quantum theory.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

12. “So, what about gravitons? Should be there. No problem. So then you start computing it. What do I mean by computing it? Well, you compute scattering of one graviton off another graviton, maybe with graviton with an electron and so on, see what you get. Feynman had already mastered this quantum electrodynamics. He said, no problem. Let me do it. Even though these are such weak forces, the gravity is very weak. So therefore, to see them, these quantum effects of gravitational waves was impossible. It's even impossible today. So, Feynman just did it for fun. He usually had this mindset that I want to do something which I will see in experiment, but this one, let's just see what it does. And he was surprised because the same techniques he was using for doing the same calculations, quantum electrodynamics, when applied to gravity failed.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

13. “Yes, that's exactly the right point to talk about. So, namely, we have talked about quantum fields, and I talked about electric forces, photon being the particle carrying those forces. So for gravity, quantizing gravitational field, which is this curvature of spacetime, according to Einstein, you get another particle called graviton.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

14. “So, in fact, I was going to get to that when we get to string theory, but maybe I can comment on that now. Duality turns out to be running the show today and the whole thing that we are doing in string theory. Duality is the name of the game So, it's the most beautiful subject, and I want to talk about it”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

15. “I would say so. I would say that viewing the particles this duality that Bohr mentioned between particles and waves, that waves can behave sometimes like particles, sometimes like waves, is one of the biggest leaps of imagination that quantum mechanics made physicists do. So I agree that that is quite remarkable.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

16. “Physics progressed, and so basically we learned that all particles Are in some sense related to particle exchanges. And so, for example, electromagnetic forces are mediated by a particle we call photons. And so forth. And the same for other forces that they discovered, strong forces and the weak forces. So we got a sense of what quantum field theory is.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

17. “This was much more complicated because it's not just one point electric and magnetic fields were everywhere. So you had to talk about fluctuating and a fuzziness of electrical field and magnetic fields everywhere. And the math for that was very difficult to deal with. And this led to a subject called quantum field theory, fields like electric and magnetic fields had to be quantum, had to be described also in a wavy way. Feynman in particular was one of the pioneers along with Schringer's and others to try to come up with a formalism to deal with fields like electric and magnetic fields interacting with electrons in a consistent quantum fashion and they developed this beautiful theory quantum electrodynamics from that. And later on that same formulaism, quantum field theory led to the discovery of other forces and other particles all consistent with the idea of quantum mechanics. So that was how”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

18. “Quote unquote mistake. So again, trying to combine ideas, sometimes the math is smarter than the person who uses it to apply it. And we try to resist it. And then you kind of confront it by criticism, which is the way it should be. So physicists comes and says, no, no, that's wrong, and you correct it and so on. So that is a development of the idea there's particle, there's antiparticle and so on. So this is the beginning of development of quantum mechanics and the connection with relativity. But the thing was more challenging because we had to also describe how electric and magnetic fields work with quantum mechanics.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

19. “By that time, Dirac himself was getting a little bit worried about his own equation and his own crazy interpretation. Until a few years later, Anderson, in photographic place that he had gotten from these cosmic rays, he discovered A particle which goes in the opposite direction that the electron goes when there's a magnetic field and with the same mass, exactly like what Iraq had predicted. And this was what we call now positron. And in fact, beginning with the work of Dirac, we know that every particle has an antiparticle. And so this idea that there's an antiparticle came from this simple math, you know, there's a plus and a minus from the Dirac's.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

20. “And so Dirac said, okay, you know what? All these negative energy states. Filled orbits occupied. So according to you Mr. Polly, there's no place to go. So, therefore, they only have to go positive. Sounded like a big cheat. And then Polly said, Oh, you know what? We can change orbits from one orbit to another. What if I take one of these negative energy orbits and put it up there? Then it seems to be a new particle which has opposite properties to the electron. It has positive energy, but it has positive charge. What Dirac was a bit worried. He said, Maybe that's Proton because Proton has plus charge. He wasn't sure. But then he said, oh, maybe it's Proton. But then they said, no, no, no. It has the same mass as the electron cannot be proton because proton is heavier. Iraq was stuck. He says, Well, maybe another park we haven't seen.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

21. “And when he did this, he originally didn't notice this, didn't pay attention to this plus or minus sign, but later physicists pointed out to Dirac says, look, there's also this minus sign. And if you use this minus sign, you get negative energy. It was very, very annoying that somebody else tells you this obvious mistake you make. Pauli, famous physicist, told Dirac, this is nonsense. You're going to get negative energy with your equation, which negative energy without any bottom. You can go all the way down to negative infinite energy. So it doesn't make any sense. Dirac thought about it. And then he remembered Pauli's exclusion principle just before him. Pauli had said, you know, there's this principle called the exclusion principle that, you know, two electrons cannot be on the same orbit.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

22. “Yes, I was talking about Dirac. Right. So Dirac was trying to now combine this shorting as equations, which was described in the context of trying to talk about how these probabilistic waves of electrons move for the atom, which was good for speeds which were not too close to the speed of light, to what happens when you get to the near the speed of light. So then you need relativity. So then Dirac tried to combine Einstein's relativity with quantum mechanics. So he tried to combine them and he wrote this beautiful equation, the Dirac equation, which roughly speaking take the square root of the Einstein's equation in order to connect it to Schrodinger's time evolution operator, which is first order in time derivative, to get rid of the naive thing that Einstein's equation would have given, which is second order. So you have to take a square root. Now, square root usually has a plus or minus sign when you take it.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

23. “No, the beauty about science is that we are not dogmatic and we are willing to, in fact, we are encouraged to be skeptical of what we ourselves do.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

24. “Improves it or replaces it, and so on. But as I mentioned before, I don't believe any of the laws of physics we know today are the end of the exactly correct. It doesn't bother me. I'm not like dogmatic saying, I have figured out this is the law of nature. I know everything. No.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

25. “Well, I think that reality is fuzzy at that level, but I don't think quantum mechanics is necessarily the end of the story. So quantum mechanics is certainly an improvement over classical physics, that much we know by experiments and so forth. Whether I'm happy with quantum mechanics, whether I view quantum mechanics, for example, the thought, the measurement description of quantum mechanics, am I happy with it? Am I thinking that's the end stage or not? I don't. I don't think we are at the end of that story. And many physicists may or may not view this way some do, some don't. But I think that it's the best we have right now, that's for sure. It's the best approximation for reality we know today. And so far, we don't know what it is the next thing that...”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

26. “And the deviation from that is very, very unlikely and probabilistically very minuscule. So, in everyday experiment, we don't see anything deviated from what we expect. But quantum mechanics tells us that things are more fuzzy. Things are not as precise as the line you draw. Things are a bit like cloud. So if you go to microscopic scales, like atomic scales and door, these phenomena become more pronounced. You can see it much better. The electron is not at the point, but the clouds spread out around the nucleus. And so this fuzziness, this probabilistic aspect of reality is what quantum mechanics describes.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

27. “Oh, yes, sure. So quantum mechanics, I discussed briefly when I talked about the connection between Newtonian mechanics and the Euler-Lagrangi formulation of the Newtonian mechanics and interpretation of this Euler-Lagrange formulism in terms of the paths that the particle take. So when we say a particle goes from here to here, we usually think it classically follows a specific trajectory, but actually in quantum mechanics it follows every trajectory with different probabilities. And so there's this fuzziness. Now, most probable, it's the path that you actually see.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

28. “Exactly. So, this is the next step. So, Einstein's developed general relativity and he's beginning to develop the foundation of quantum mechanics at the same time, the photoelectric effects on others. And so quantum mechanics overtakes, in fact, Einstein in many ways because he doesn't like the probabilistic interpretation of quantum mechanics and the formulas that's emerging, but physicists march on and try to, for example, combine Einstein's theory of relativity with quantum mechanics. Dirac takes special relativity, tries to see how is it compatible with quantum mechanics”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

29. “In a sense, the conception of space time already was part of speciality when you talk about length contraction. Generativity takes that to the next step, but beginning of it was already space link contracts, time dilates. So why don't you talk about those, then you can dilate more or less different places than it's curvature. So you don't have a choice. So it kind of started just with that same simple thought. Speed of light is the same for all.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

30. “I would say that's it. Even though he says the most beautiful moment for him, he says that is when he realized that if you fall in an elevator, you don't know if you're falling or whether you're in the falling elevator or whether you're next to the Earth gravitational field. That to him was his aha moment, which inertial mass and gravitational mass being identical. Geometrically and so forth as part of the theory, not because of some funny coincidence for him. But I feel from outside at least it feels like the speed of light being the same is the really a homo moment.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

31. “In my opinion, it's special relativity. The idea that speed of light is the same for everybody is the beginning of everything he did.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

32. “Would show that math and physics have this symbiotic relationship which kind of reinforce each other. Here I'm using, I'm giving you examples of both of them, namely Newton's work led to development of mathematics calculus. And in the case of Einstein, he didn't develop Riemannian geometry, just used them. So it goes both ways. And in the context of modern physics, we see that again and again. It goes both ways.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

33. “But the contrast between the special relativity and general relativity is very interesting because one of them has almost trivial math and the other one has super complicated math. Both are physically amazingly important. And so we have learned that the physics may or may not require complicated math. We should not shy from using complicated math like Einstein did. Einstein willn't say, I'm not going to touch this math because it's too much tensors or curvature and I don't like the four-dimensional spacetime because I can't see four dimensions. He wasn't doing that. He was willing to abstract from that because physics drove him in that direction. But his motivation was physics. Physics pushed him. Just like Newton pushed to develop calculus because physics pushed him that he didn't have the tool. So he had to develop the tools to answer his physics questions. So his motivation was physics again. So to me, those are examples.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

34. “Iceland's theory. And in fact, so much, so much harder that Einstein himself couldn't solve many of the cases he thought, for example, you couldn't solve the equation for a spherical symmetric matter, like if you had a symmetric sun, you didn't think you can actually write the solve his equation for that. And a year after he said that it was solved by Short Child. So it was that hard that he didn't think it's going to be that easy. So yeah, the formism is hard.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

35. “So then going back to your question about the path of the history of the science, so I was saying about the electric magnetism and the special relativity were simple idea led to special relativity. But then he went further thinking about acceleration in the context of relativity and he came up with general relativity where he talked about the fabric of spacetime being curved and so forth and matter affecting the curvature of the space on time. So this gradually became a connection between geometry and physics namely he replaced Newton's gravitational force with a very geometrical, beautiful picture. It's much more elegant than Newton's, but much more complicated and mathematically. So when we say it's simpler, we mean in some form it's simpler, but not in pragmatic terms of equation solving. The equations are much harder to solve.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

36. “Yes, I think they do actually. I would not be able to do my research if I don't have an intuitive feel about geometry. And we'll get to it, as you mentioned before, that how, for example, in Stringthe, you deal with these extra dimensions, and I'll be very happy to describe how we do it. Because without intuition, we will not get anywhere. And I don't think you can just rely on formalism. I don't. I don't think any physicist just relies on formalism. That's not physics. That's not understanding. So we have to intuit it. And that's crucial. And there are steps of doing it. And we learned it might not be trivial, but we learn how to do it similar to this Galileo picture I just told you. You have to build these gradually. You have to connect the connects.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

37. “He says, okay, what if we move these bricks around with the same height? Does it change the time they hit the ground? They said, if it's the same height, again, by the symmetry principle, because the height translation horizontal translation is symmetry, no, it doesn't matter. They all follow the same rate. Good. Doesn't matter how close I bring them together. No, it doesn't. Okay, suppose I make the two bricks touch and then let them go. Do they fall at the same rate? Yes, they do. But then he said, well, the two bricks that touch are twice more mass than this other brick. And you just agreed that they fought the same rate. They say, yeah, yeah, we just agreed. That's right. That's strange. So he deconfused them by this symmetry reasoning. So, this way of repackaging some intuition, a different intuition, when the intuitions clash”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

38. “The experiment was not enough. Didn't think that they have toar their hands in doing experiments to get to the reality. They said, why is it the case? So, Galileo had to come up with an explanation of why heavier and lighter objects fought the same rate. This is the way he convinced them using symmetry. He said, suppose you have three bricks, the same shape, the same size. Same mass everything. And we hold these three bricks at the same height and drop them. Which one will fall to the ground first? Everybody said, Of course, we know it, symmetry tells you they're all the same shape, same size, same height. Of course they fall at the same time. Yeah, we know that next, next is triv”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

39. “Kind of makes sense, and you know, people say about feather and so on, but that's because of the air resistance. But you might think like if you have a heavy stone and a light pebble, the heavy one will fall first if you don't, you know, do any experiments. That's the first gut reaction. I would say everybody would say that's the natural thing. Galileo did not believe this and he kind of did the experiment. Famously, it said he went on the top of Pisa Tower and he dropped these heavy and light stones and they fell at the same time when he dropped to that same time. The same height. Okay, good. So he said, I'm done, you know. I've showed that the heavier and lighter objects fought at the same time. I did the experiment. Scientists at that time did not accept it. Why was that? Because at that time, science was not just experimental.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

40. “As you are just feeling the same way. It is. Is but we kind of replace it by an intuition. And actually, there's a very beautiful example of this, how physicists do this, try to replace their intuition. And I think this is one of my favorite examples about how physicists develop intuition It goes to the work of Galileo. So, you know, again, let's go back to Greek philosophers or maybe Aristotle in this case. Now again, let's make a criticism. He thought that objects, the heavier objects fall faster than the lighter objects.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

41. “And part of it is because we live in a situation where we don't go with very high speeds. There are speeds that are small compared to the speed of light. And therefore, the phenomena we observe does not distinguish the relativity of time. The time also depends on who measures it. There's no absolute time. When you say it's noon today now, it depends on who's measuring it and not everybody would agree with that statement. And to see that you will have to have a fast observer moving closer to speed of light. So this shows that our intuition is at fault. And a lot of the discoveries in physics, precisely is getting rid of the wrong old intuition. And it is funny because we get rid of it, but it's always lingers in us in some form. Like even when I'm describing it, I feel like a little bit like, isn't it funny?”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

42. “It sounds ridiculous until you learn that our intuition is at fault about the way we conceive of space and time, the way we think about space and time is wrong, because we think about the nature of time as absolute”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

43. “That's the basic, that's the guts of it. That's the core of Einstein's theory. That statement underlies the whole thing. Speed of light is the same for everybody. It's hard to swallow and it doesn't sound right. It sounds completely wrong on the face of it. And it took Einstein to make this daring statement. It would be laughing in some sense. How could anybody make this possibly ridiculous claim? And it turned out to be true.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

44. “Discovered. Michael Snar and Morley's experiments show there is no ether. So the Einstein was courageous enough to say, you know, light is the same speed for everybody, regardless of whether you're moving or not. And the interesting thing is about special theory of relativity is that the math underpinning it is very simple. It's linear algebra. Nothing terribly deep. You can teach it at a high school level, if not earlier. OK. Does that mean Einstein's special relativity is boring? Not at all. So this is an example where simple math, linear algebra leads to deep physics. Einstein's theory of special relativity, motivated by this inconsistency at Maxwell's equation would suggest for the speed of light depending on who observes it.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

45. “Get one speed light who measures this light speed? And he asked the question, are you moving? Are you not moving? If you move, the speed of light changes. But Maxwell's equation has no hint of different speeds of light. It doesn't say, oh, only if you're not moving you get the speed. It's just you always get this speed. So Einstein was very puzzled and he was daring enough to say, well, you know, maybe everybody get the same speed for light. And that motivated his theory of special relativity. And this is an interesting example because the idea was motivated from physics, from Maxwell's equations, from the fact that people try to measure the properties of ether, which was supposed to be the medium in which the light travels through. And the idea was that only in that medium the speed is speed of if you're at rest with respect to the ether, the speed is speed of light. And if you're moving the speed changes and people did not.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

46. “But then he was courageous enough to say, Well, maybe light is nothing but these electric and magnetic fields moving around. And he didn't, he wasn't alive to see the verification of that prediction and indeed was true. So this mathematical inconsistency, which we could say, this mathematical beauty drove him to this physical, very important connection between light and electromagnetic phenomena, which was later confirmed. So then physics progresses and it comes to Einstein. Einstein looks at Maxwell's equation. He says, beautiful. These are nice equations except”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

47. “Little term there it works at least it's consistent what is the motivation for that term said I don't know have we seen it in experiments no why did you add it well because of mathematical consistency so he said okay math Forced him to do this term. He added this term, which we now today call the maximal term. And once he added that term, his equations were nice, you know, differential equations mathematically considered. Found that because of that term he could now get electric and magnetic waves moving Through space at a speed that he could calculate. So he calculated the speed of the wave, and lo and behold, he found it's the same as the speed of light, which puzzled him because he didn't think light had anything to do with electricity and magnetism.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

48. “Sure. So I mentioned the classical mechanics and the Euler Lagrangian formulation. One of the next important milestones for physics were the discoveries of laws of the electrician magnetism. So Maxwell put the discoveries all together in the context of what we call the Maxwell's equations. And he noticed that when he put these discoveries that Faraday's and others had made about electric and magnetic phenomena in terms of mathematical equations, it didn't quite work. There was a mathematical inconsistency. Now, you know, one could have a two attitude. One could say, okay, who cares about math? I'm doing nature, you know, electric force, magnetic force, math I don't care about. But it bothered him. It was inconsistent. The equations he were writing, the two equations he had written down did not agree with each other. And this bothered him. But he figured out, you know, if you add this jiggle this equation by adding...”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

49. “Shrinking to zero size, that gives you strong forces. If you have one of them, it gives you the weak forces. If you have this, you get that. And if you want to unify forces, do the other thing. So these geometrical translation of physics is one of my favorite things that we have discovered in modern physics in the context of string theory.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source

50. “What forces? Forces like the ones we have seen in nature today, like electric forces, like strong forces, like weak forces. So these same principles that were driving them to connect geometry and symmetries to nature is driving today's physics now much more modern ideas, but nevertheless, the symmetries connecting geometry to physics. In fact, often sometimes we ask the following question. Suppose I want to get this particular physical reality. I want to have this particles with these forces and so on. What do I do? It turns out that you can geometrically design this space to give you that. You say, oh, I put the sphere here. I would do this. I would shrink them. So if you have two spheres touching each other.”

    2021-07-26 · Lex Fridman Podcast · #204 – Cumrun Vafa: String Theory · IDENTIFIED FROM THE TRANSCRIPT · source