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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. “Exactly in these kinds of thoughts processes in the following way. In the context of string theory, which is the phili study, we have these extra dimensions. And these extra dimensions are compact tiny spaces typically, but they have different shapes and sizes. We have learned that if these extra shapes and sizes have symmetries which are related to the same rotation symmetries that the Greek were talking about, if they enjoy those discrete symmetries, and if you take that symmetry and quotient the space by it, in other words, identify points under these symmetries, you get properties of that space at the singular points which force emanates from them.”

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

2. “Yes, geometry is my favorite part of math as well. And Greeks were enamored by geometry. They tried to describe physical reality using geometry and principles of geometry and symmetry. Platonic solids, the five solids they had discovered had these beautiful solids, they thought it must be good for some reality. There must be explaining something they attached one to air, one to fire, and so forth. So they tried to give physical reality to symmetric objects. These symmetric objects are symmetries of rotation and discrete symmetry groups we call today a rotation group in three dimensions. Now we know now we kind of laugh at the way they were trying to connect that symmetry to the laws of the realities of physics. But actually it turns out in modern days we use symmetries not too far away”

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

3. “Right. So symmetry sometimes is an explanation of being at the symmetric point is sometimes a simple explanation of many things. Like if you have a bowl, Circular ball, then the bottom of it is the lowest point. So if you put a pebble or something, it will slide down and go there at the bottom and stays there at the symmetric point because the preferred point, the lowest energy point. But if that same symmetric circular ball that you had had had a bump on the bottom, the bottom might not be at the center. It might be on a circle on the table. In which case, the pebble would not end up at the center, it would be the lower energy point, symmetrical, but it breaks the symmetry once it picks a point on that circle. So we can have symmetry reasoning for where things end up or symmetry breakings, like this example would suggest.”

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

4. “No, you are going to get hungry, you're going to move towards one of those loaves of bread despite the fact that it breaks the symmetry. So from this way, he tried to argue being at the symmetric point may not be the preferred thing to do. And this idea of spontaneous symmetry breaking is something we just used today to describe many physical phenomena. So spontaneous symmetry breaking is the feature that we now use. But this idea was there thousands of years ago, but applied incorrectly to the physical world, but now we are using it so these ideas are coming back in different forms. So I agree very much that the thought process is more important and these ideas are more interesting than the actual applications that people may find today.”

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

5. “And that's not good because it's not symmetrical anymore. So, therefore, the Earth decides to sit put because it would break the symmetry. So they had the incorrect signs. They thought Earth doesn't move. And they had this beautiful idea that symmetry might explain it. But they were even smarter than that. Aristotle didn't agree with this argument Said, why do you think symmetry prevents it from moving? Because the preferred position? Not so. He gave an example. He said, suppose you are a person and we put you at the center of a circle. We spread food around you on a circle around you. Loaves of bread, let's say. We say, okay, stay at the center of the circle forever. Are you going to do that just because it's the symmetric point”

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

6. “Very brilliant. Very brilliant. So these Greek philosophers are very smart. And so they had taken it to the next step. They asked, okay, so the Earth is round. Why doesn't it move? They thought it doesn't move they were looking around, nothing seemed to move. So they said, okay, we have to have a good explanation. It wasn't enough for them to be there. So they really want to deeply understand that fact. And they come up with a symmetry argument. And the symmetry argument was, oh, if the Earth is a spherical, it must be at the center of the universe for sure. So they said the Earth is at the center of the universe. They said, you know, if Earth is going to move, which direction does it pick? Any direction it picks, it breaks that spherical symmetry because you have to pick a direction.”

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

7. “You know, they have seen the length of the shadow of a meter stick, and they have seen that if you go from the equator upwards north, they find that depending on how far away you are, that the length of the shadow changes. And from that, they had even measured the radius of the Earth to good accuracy.”

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

8. “I completely agree. In fact, I believe that almost, well, I believe that none of the principles or laws of physics we know today are exactly correct. All of them are approximations to something. They are better than the previous versions that we had, but none of them are exactly correct, and none of them are going to stand forever. So I agree that that's the process we are heading. We are improving. And yes, indeed, the thought process and that philosophical take is common. So when we look at older scientists or maybe even all the way back to Greek philosophers and the things that the way they thought and so on, almost everything they said about, you know, nature was incorrect. But the way they thought about it and many things that they were thinking is still valid today. For example, they thought about symmetry breaking. They were trying to explain the following. This is a beautiful example, I think. They had figured out that the Earth is round and they said, okay, Earth is round.”

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

9. “Questions and looking for things. And it has guided scientists, I think, through many centuries, and I think it continues to do so today.”

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

10. “They may not state that they are philosophers or they may not like to be labeled philosophers, but in many ways what they do is like what is philosophical takes of things, looking for simplicity or symmetry is an example of that, in my opinion, or seeing patterns. You see, for example, another example of the symmetry is like how you come up with new ideas in science. You see, for example, an idea A is connected with an idea B. Okay, so you study this connection very deeply. And then you find the cousin of an idea A, let me call it A prime, and then you immediately look for B prime if A is like B and if there's an A prime, then you look for B prime. Why? Well, it completes the picture. Why? Well, it's philosophically appealing to have more balance in terms of that. And then you look for B prime and low and behold, you find this other phenomena, which is a physical phenomenon, which you call B prime. So this kind of thinking motivates asking.”

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

11. “In a sense, scientists are a lot like philosophers. Sometimes I think, especially modern science seems to shun philosophers and philosophical views. And I think at their peril, I think, in my view, science owes a lot to philosophy. And in my view, many scientists, in fact, probably all good scientists, perhaps amateur philosophers.”

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

12. “Well, these are good questions. We don't have a deep understanding of why we get attracted to symmetry. Why do laws of nature seem to have symmetries underlying them? And the reasoning or the examples of whether if it wasn't symmetry, we would have understood it or not. We could have said that, yeah, if there were things which didn't look that great, we could understand them. For example, we know that symmetries get broken and we have appreciated nature in the broken symmetry phase as well. The world we live in as many things which do not look symmetric. But even those have underlying symmetry when you look at it more deeply. So we have gotten maybe spoiled perhaps by the appearance of symmetry all over the place. And we look for it. And I think this is perhaps related to the sense of aesthetics that scientists have. And we don't usually talk about it among scientists. In fact, it's kind of a philosophical view of why do we look for simplicity or beauty or so forth. And I think”

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

13. “And so I think the same is true in physics, that if we find a principle which looks ugly, we are not going to be, that's not the end stage. So therefore, beauty is going to lead us somewhere. Now, it doesn't mean beauty is enough. It doesn't mean if you just have beauty, if I just look at something is beautiful, then I'm fine. No, that's not the case. Beauty is certainly a criteria that every good physical theory should pass. That's at least the view we have. Why do we have this view? That's a good question. It is partly, you could say, based on experience. Partly is a philosophical view of what reality is or should be. And in principle, it could have been ugly and we might have had to deal with it, but we have gotten maybe confident through examples after examples in the history of science to look for beaut”

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

14. “Yes, I would say that mathematics can lead us astray as much as all physical ideas can lead us astray. If you get stuck in some thing, then you can easily fool yourself that just like the thought process. We have to free ourselves of that. Sometimes math does that role. Like say, oh, this is such a beautiful math. I definitely want to use it somewhere. And so you just get carried away and you just get maybe carried too far away. So that is certainly true. But I wouldn't say it's more dangerous than old physical ideas. To me, new math ideas is as much potential to lead us astray as all physical ideas, which could be long-held principles of physics. So I'm just saying that we should keep an open mind about the role the math plays, not to be antagonistic towards it and not to overwhelming it. We should just be open to possibilities.”

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

15. “Yes, the amplitude means if you sum up all these paths with exponential it times the action, if you sum this up, you get a number, complex number. You square the norm of this complex number, gives you a probability to go from one to the other.”

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

16. “An average correct And the particle going from one to the other doesn't take exactly one path. It takes all the paths. With the amplitude, which is proportional to the exponential of the action times an imaginary number i. And so this fact turned out to be the reformulation of quantum mechanics. We should start there as the basis of the new law, which is quantum mechanics. And Newton is only an approximation on the average correct.”

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

17. “So you take this integral, and each path will give you some quantity. And the path it actually takes, the physical path, is the one which minimizes this integral or this action. Now, this sounded like a backward step from Newton's. Newton's form that seemed very simple. f equals to ma and you can write f is minus the gradient of the potential so why would anybody start formatting such a simple thing in terms of this complicated looking principle you have to study the space of all paths and all things and find the minimum and then you get the same equation so what's the point so euler and logarange's formulation of newton which was kind of a recasting in this language is just a consequence of newton's law f equals to mm gives you the same fact that this path is a minimum action now what we learned later last century was that when we deal with quantum mechanics Newton's law is only”

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

18. “Is the following you take all possible paths connecting this particle from going from the initial point to the final point and you compute the action and what is an action? Action is the integral over time of the kinetic term of the particle minus its potential.”

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

19. “Perhaps I'll give an example to see how it goes. And in fact, a historical example is Newton's work on classical mechanics. So Newton formulated the laws of mechanics, you know, the force f equals to ma and his other laws, and they look very simple, elegant, and so forth. Later, when we studied more examples of mechanics and other similar things, physicists came up with the idea that the notion of potential is interesting. Potential was an abstract idea which kind of came. You could take its gradient and relate it to the force. So you don't really need it a priori, but it solved helped some thoughts. And then later, Euler and Lagrange reformulated Newtonian mechanics in a totally different way in the following fashion. They said, if you take, if you want to know where a particle at this point and at this time, how does it get to this point at the later time?”

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

20. “Of a hypothesis actually the reason that's true is the opposite. And so we reverse the order. And so this switching back and forth between ideas makes us more fluid about deductive fashion. Of course, it sometimes gives a wrong impression like physicists don't care about rigor. They just say random things. They are willing to say things that are not backed by the logical reasoning. That's not true at all. So despite this fluidity in saying which one is a primary thought, we are very careful about trying to understand what we have really understood in terms of relationship between ideas. So that's an important ingredient. And in fact, solid math being behind physics is, I think, one of the attractive features of a physical law. So we look for beautiful math underpinning it.”

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

21. “Part of the reason is that we have learned in physics that the ideas are not sequential, and if we think that there's one idea which is more important and we start with there and go to the next idea and next one and deduce things from that like mathematicians do, we have learned that the third or fourth thing we deduce from that principle turns out later on to be the actual principle. And from a different perspective, starting from there leads to new ideas, which the original one didn't lead to. And that's the beginning of a new revolution in science. So this kind of thing we have seen again and again in the history of science, we have learned to not like deductive reasoning because that gives us a bad starting point to think that we actually have the original thought process should be viewed as the primary thought and all these are deductions, like the way mathematicians sometimes does. So in physics, we are learning to be skeptical of that way of thinking. We have to be a bit open to the possibility that what we thought is a deduction.”

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

22. “Well, that's a difficult question because in many ways math and physics are unified in many ways. So to distinguish them is not an easy task. I would say that perhaps the goals of math and physics are different. Math does not care to describe reality. Physics does. That's the major difference. But a lot of the thoughts, processes, and so on, which goes to understanding the nature and reality are the same things that mathematicians do. So in many ways, they are similar. Mathematicians care about deductive reasoning. And physicists or physics in general, we care less about that. We care more about interconnection of ideas, about how ideas support each other, or if there's”

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