Skip to content
Lex Fridman PodcastLex Fridman Podcast

Jim Gates: Supersymmetry, String Theory and Proving Einstein Right | Lex Fridman Podcast #60

Lex Fridman and S. James Gates Jr. on jim Gates explores supersymmetry, string theory, consciousness, and destiny.

Lex FridmanhostS. James Gates Jr.guest
Dec 25, 20191h 34mWatch on YouTube ↗

EVERY SPOKEN WORD

  1. 0:00 – 15:00

    The following is a…

    1. LF

      The following is a conversation with S. James Gates Jr. He's a theoretical physicist and professor at Brown University, working on supersymmetry, supergravity, and superstring theory. He served on former President Obama's Council of Advisors on Science and Technology, and he's now the co-author of a new book titled Proving Einstein Right, about the scientist who set out to prove Einstein's theory of relativity. You may have noticed that I've been speaking with not just computer scientists, but philosophers, mathematicians, physicists, economists, and soon, much more. To me, AI is much bigger than deep learning, bigger than computing. It is our civilization's journey into understanding the human mind and creating echoes of it in the machine. That journey includes, of course, the world of theoretical physics and its practice of first principles mathematical thinking, and exploring the fundamental nature of our reality. This is the Artificial Intelligence podcast. If you enjoy it, subscribe on YouTube, give it five stars on Apple Podcast, follow on Spotify, support on Patreon, or simply connect with me on Twitter @lexfridman, spelled F-R-I-D-M-A-N. If you leave a review on Apple Podcasts or YouTube or Twitter, consider mentioning ideas, people, topics you find interesting. It helps guide the future of this podcast. But in general, I just love comments that are full of kindness and thoughtfulness in them. This podcast is a side project for me, but I still put a lot of effort into it. So, the positive words of support from an amazing community, from you, really help. I recently started doing ads at the end of the introduction. I'll do one or two minutes after introducing the episode, and never any ads in the middle. They can break the flow of the conversation. I hope that works for you and doesn't hurt the listening experience. I provide timestamps for the start of the conversations, you may have noticed, that you can skip to, but it helps if you listen to the ad and support this podcast by trying out the product or service being advertised. This show is presented by Cash App, the number one finance app in the App Store. I personally use Cash App to send money to friends, but you can also use it to buy, sell, and deposit Bitcoin in just seconds. Cash App also has a new investing feature. You can buy fractions of a stock, say $1 worth, no matter what the stock price is. Broker services are provided by Cash App Investing, a subsidiary of Square, member SIPC. I'm excited to be working with Cash App to support one of my favorite organizations called FIRST, best known for their FIRST robotics and LEGO competitions. They educate and inspire hundreds of thousands of students in over 110 countries, and have a perfect rating on Charity Navigator, which means the donated money is used to maximum effectiveness. When you get Cash App from the App Store or Google Play, and use code LEXPODCAST, you'll get $10, and Cash App will also donate $10 to FIRST, which again, is an organization that I've personally seen inspire girls and boys to dream of engineering a better world. And now, here's my conversation with S. James Gates Jr. You tell a story when you were eight, you had a profound realization that the stars in the sky are actually places that, uh, we could travel to one day. Do you think human beings will ever venture outside our solar system?

    2. SJ

      Wow. The question of whether humanity gets outside of the solar system. It's gonna be a challenge. And as long as the laws of physics that we have today are accurate and valid, it's gonna be extraordinarily difficult. Uh, I'm a s- science fiction fan, as you probably know, so I love to dream of starships and traveling to other solar systems, but the barriers are just formidable.

    3. LF

      If we just kinda venture a little bit into science fiction, do you think the spaceships, if we are successful, that take us outside the solar system will look like the ones we have today? Or do fundamental breakthrough, uh, are fundamental breakthroughs necessary?

    4. SJ

      In order to have genuine starships, probably some really f- radical views about the way the universe works is, are going to have to take place in our science. We could, uh, with our current technology, think about constructing multi-generational starships, where the people who get on them (laughs) are not the people who get off at the other end. Um, but even if we do that, the, the formidable problem's actually our bodies, which doesn't seem to be conscious, uh, for a lot of people. Even getting to Mars is gonna present this challenge, because we live in this wonderful home, has a protective magnetic, uh, magnetosphere around it, and so we're shielded from, uh, cosmic radiation. Uh, once you leave, uh, this shield, um, there are some estimates that, for example, if you sent someone to Mars, uh, with our technology, probably about two years out there without the shield, they're gonna be bombarded. That means radiation, probably means cancer. So, that's one of the most formidable challenge, even if we could get over the technology.

    5. LF

      Do you think... So Mars is a harsh place. D- Elon Musk, SpaceX, and other folks, NASA, are really pushing to put a human being on Mars. Do you think, again, let's... Forgive me for lingering in science fiction land for a little bit, do you think one day we may be able to colonize Mars? First, do you think we'll put a human on Mars? And then, do you think we'll put many humans on Mars?

    6. SJ

      So, first of all, we're not... I- I am extraordinarily convinced we will not put a human on Mars by 2030, which is a n- date that you often hear in the public debate.

    7. LF

      What's the challenge there? What do you think?

    8. SJ

      It... So, uh, there are a couple of ways that I could slice this, but the one that I think is simplest for people to understand involves money.So, you look at-

    9. LF

      Mm-hmm.

    10. SJ

      ... how we got to the moon in the 1960s. It was about 10-year duration between the challenge that President Kennedy laid out and our successfully landing on moon. I was actually here at MIT when that first moon land-landing occurred, so I remember watching it on TV. But how did we get there? Well, we had this extraordinarily, like, technical, um, agency of the United States government, NASA. It consumed about 5% of the country's, uh, economic output. And so you say, "5% of the economic output over about a 10-year period gets us 250,000 miles in space." Mars is about 100 times farther. So you have at least 100 times the challenge, and we're s- spending about one-tenth of the funds that we spent then as a government. So my claim is, is that it's at least 1,000 times harder for me to imagine us getting to Mars by 2030.

    11. LF

      And yet that part that you mentioned in the speech that I just have to throw in there of, um, JFK of, "We do these things not because they're easy but because they're hard."

    12. SJ

      Yeah.

    13. LF

      That's such a beautiful line that I would love to hear a modern president say-

    14. SJ

      (laughs)

    15. LF

      ... about a scientific endeavor.

    16. SJ

      Well, one day, uh, we live in hope that, uh, such a president will arise for our nation. But even if, like I said, even if you s- you fix the pro- the technical problems, the biological engineering that I worry most about... However, I'm gonna go out on a li- a limb here. I think that by 2090 or so, or 2,100, should I say 2,120-

    17. LF

      Yeah.

    18. SJ

      ... I suspect we're gonna have a human on Mars.

    19. LF

      Wow, so you think that many years out? Uh, first, a f- a few tangents. You said bioengineering is a cha- is a challenge. Well, what's, what's the challenge there?

    20. SJ

      So as I said, the, the, the real problem with, uh, interstellar travel, aside from the technology challenges, the real problem is radiation and how do you engineer either an environment or a body, because we see rapid advances going on in bioengineering, how do you engineer either a ship or a body so that something, some person that's recognizably human, uh, human will survive the rigors of interplanetary space travel? It's much more difficult than most people seem to take into account.

    21. LF

      So, if we could linger on the 2090, 2100, 2120 sort of thinking of that kind of... You know, and we... Let's linger on money.

    22. SJ

      Okay.

    23. LF

      So, Elon Musk and, uh, Jeff Bezos are, are pushing the cost, trying to qui- push the cost down. I mean, this is... So do you have hope... Is this actually a sort of brilliant big picture scientist, do you, do you think a business entrepreneur can take science and make it cheaper and get it out there faster?

    24. SJ

      So bending the cost curve is, you'll notice that has been an anchor. This is the simplest way for me to discuss this with people about what the challenge is. So yes, bending the cost curve is, uh, certainly critical if we're going to be successful. Now, you ask about, uh, the endeavors that are out there now, uh, sponsored by two very prominent American citizens, Jeff Bezos and Elon Musk. I'm disappointed, actually, in what I see in terms of the routes that are being pursued, so let me give you one example there (laughs) , and this one is going to be a little bit more technical. So if you look at the kinds of rockets that both, uh, these organizations are creating, yes, it's wonderful, reusable technology to see a rocket go up and land on its fins just like it did in science fiction movies when I was a kid. That's astounding. But the, uh, real problem is those rockets, the technology that we're doing now, is not really that different f- than what was used to go to the moon. And there are alternatives, it turns out. There's an engine called a flare engine which... So, a traditional rocket, if you look at the engine, looks like a bell, right? And then the flame comes out the bottom, but there is a kind of engine called a flare engine which is essentially... When you look at it, it looks like an exhaust pipe on like a fancy car that's, you know, long and elongated, and it's a type of rocket engine that we know, uh, that we know, it's, there've been preliminary testing, we know it works, and it also is actually much more economical because what it does is allow you to vary the amount of thrust as you go up in a way that you cannot do with one of these bell-shaped engines. So, you would think that an entrepreneur, uh, might, uh, try to have the breakthrough to use flare nozzles, as they're called, uh, as a way to bend the cost curve, 'cause as we keep coming back, that's gonna be a big factor. But that's not happening. In fact, what we see is what I think of as incremental change in terms of our technology, so I'm not really very encouraged by what I personally see.

    25. LF

      So incremental change won't bend the cost curve enough?

    26. SJ

      I don't see it.

    27. LF

      Just to linger on the sci-fi for one more question.

    28. SJ

      Sure.

    29. LF

      (laughs) Do you think we're alone in the universe? Are we the only intelligent form of life?

    30. SJ

      So, there is a quote by Carl Sagan which I really love when I hear this question, and I, um, I, I recall the quote, and it goes something like, "If we're the only conscious life, uh, uh, in the universe, it's a terrible waste of space." Because the universe is an incredibly big place. And when Carl made that s- uh, statement, we didn't know about the profusion of planets that are out there. Uh, in the last decade, we've discovered over 1,000 planets, and a s- substantial number of those planets are Earth-like in terms of being in the Goldilocks zone, as it's called.... so it's un- in my mind, it's practically inconceivable that we're the only conscious form of life in the universe, but that doesn't mean they've come to visit us.

  2. 15:00 – 30:00

    But the beautiful, surprising…

    1. SJ

      that I encounter in a number of guises. Uh, a lot of people will raise the question about whether mathematics is the language of the universe, and my response is, "Mathematics is the language that we humans are capable of using in describing the universe." It may have little to do with the universe, but in terms of our capacity, it's the microscope, it's the telescope through which we, uh, it's the lens through which we are able to view the universe with a precision that no other human language allows. So, could there be other universes? Well, I don't even know if this one looks like I think it does.

    2. LF

      But the beautiful, surprising thing is that, uh, physics, there are laws of physics, very few laws of physics that can effectively compress down the functioning of the universe?

    3. SJ

      Yes, that's extraordinarily surprising, and I like to use the analogy with, uh, computers and information technology. Uh, if you worry about, uh, transmitting large bundles of data, uh, one of the things that computer scientists do for us is they allow for processes that are called compression, where you take big packets of data, and you press them down into much smaller packets, and then you transmit those and then unpack them at the other end. And so it- it looks a little bit to me like the universe has kind of done us a favor. It's constructed our minds in such a way that we have this thing called mathematics, which then as we look at the universe, teaches us how to carry out the compression process.

    4. LF

      A quick question about compression. Do you think, uh, the human mind could be compressed, the, the b- biology could be compressed? We talked about space travel. To be able to compress the information that captures some large percent of what it means to be me or you, and then be able to send that at the speed of light?

    5. SJ

      (laughs) Wow, that's a big question, and, um, let me try to take it apart, unpack it into several pieces. I don't believe that wet ware biology such as we are has an exclusive, uh, patent on in- on intellecting consciousness. I suspect that other structures in the universe are perfectly capable of producing the data streams that we use to process, first of all, our observations of the universe and, and an awareness of ourself. I, I can imagine other structures can do that also. So, that's part of what you were talking about which I would, um, have some disagreement with.

    6. LF

      Consciousness.

    7. SJ

      Yes.

    8. LF

      What's the most interesting part of...

    9. SJ

      Consciousness?

    10. LF

      Of, uh, us humans is consciousness is the thing-

    11. SJ

      I think that's the most interesting thing about humans.

    12. LF

      And then you're saying that there's other entities throughout the universe?

    13. SJ

      I could imagine. I can well imagine that the architecture that supports our consciousness, again, has no patent on consciousness.

    14. LF

      Just, uh, in case you have an interesting thought here, there's, uh, folks perhaps in philosophy called panpsychists that believe consciousness underlies everything. It is one of the fundamental laws...... of the universe. Do you have a sense that that could possibly fit into physics model?

    15. SJ

      I don't know the answer to that question. Uh, one part of, uh, that belief system is Gaia, which is, uh, that there's a kind of conscious life force about our planet. And, you know, I've encountered these things before. I don't quite know what to make of them. I... My own ex- uh, life experience, and I'm... I'll be 69 in about two months, and I have spent all my adulthood thinking about the way that mathematics interacts with, uh, nature and with us to try to understand nature. And all I can d- tell you from all of my integrated experience is that there is something extraordinarily mysterious to me about our universe. This is something that Einstein said, uh, uh, f- from his life experience as a scientist. And this mysteriousness almost feels, uh, like the universe is our parent. It's a very strange thing perhaps to hear science say- scientists say, but there are just so many strange coincidences that you just get a sense that something is going on.

    16. LF

      (laughs) Well, I interrupted you. In terms of compressing-

    17. SJ

      Uh, yes.

    18. LF

      ... what, where down till we can send it at the speed of light...

    19. SJ

      Yes. So, so the first thing is I would argue that it's probably very likely that artificial intelligence, uh, ultimately will develop s- uh, something like consciousness, something that f- for us would probably be indistinguishable from consciousness. So, that's what I meant by, uh, our biological, uh, processing equipment that we carry up here probably had... does not hold a patent on consciousness. Because it's really about the data streams. I mean, that's... As far as I can tell, that's what we are. We are s- uh, self-actuating, self-learning, uh, data streams. That, to me, is the most accurate way I can tell you what I have seen in my lifetime about what humans are, uh, at the level of consciousness. So, if that's the case, then you just need to have an architecture that supports that information processing. So, let's assume that that's true, that, uh, that, in fact, what we call consciousness is really about a, a very peculiar kind of data stream. If that's the case, then, uh, if you can, uh, export that to a piece of s- uh, hardware, uh, something metal, electronic, what have you, then, uh, you certainly will... Ultimately, that k- kind of consciousness could get to Mars very quickly.

    20. LF

      Mm-hmm.

    21. SJ

      It doesn't have our problems. You can engineer the body. As I said, it's a ship or a body. You engineer one or both. Um, send it at the speed of light? Well, that one is a more difficult one, because that now goes beyond just a matter of having a data stream. It's n- now the preservation of the information in the data stream.

    22. LF

      Hmm.

    23. SJ

      And so, unless you can build something that's like a super, super, super version of the way the internet works... 'Cause most people aren't aware that the internet itself is actually a miracle. It's based on a technology called message packaging. So, if you could exponentiate message packaging in some way to preserve the information that's in the data stream, then maybe your dream becomes true.

    24. LF

      Can we, um... You mentioned with artificial intelligence, sort of, uh, us human beings not having a monopoly on consciousness. Does the idea of artificial intelligence systems, computational systems, being able to basically replacing us humans scare you, excite you? What do you think about that?

    25. SJ

      So, I'm gonna tell you about a conversation I once had with Eric Schmidt.

    26. LF

      Mm-hmm.

    27. SJ

      I was sitting at a meeting with him and he was, uh, hmm, a few feet away, and he turned to me and he said, uh, something like, "You know, Jim, in maybe a decade or so, we're gonna have computers that do what you do."

    28. LF

      (laughs)

    29. SJ

      And my response was, "Not unless they can dream." Because there's something about the c- human, the way that we humans actually generate creativity. It... it's somehow... I g- I get this sense of my lived experience in watching creative people, that it's somehow connected to the irrational parts of what goes on in our head.

    30. LF

      Yes.

  3. 30:00 – 45:00

    And many people have…

    1. SJ

      it out to the kind of technological development we're seeing now outside of nuclear physics, but I, I picked the example of biology. Uh, I could well imagine that, uh, there would be material science sorts of equivalents that across a broad front of technology, you, you take that experience from nuclear weapons. And the picture that I see is that it will be so... There will, it will be possible to develop technologies that are so terrible that you couldn't use them.... because the costs are too high. And that might cure us.

    2. LF

      And many people have argued that actually it, um, prevented... Nuclear weapons have prevented more military conflict than...

    3. SJ

      It certainly froze the, um, conflict domain. Uh, it's interesting that nowadays, uh, it was with the removal of the threat of mutually assured destruction that, uh, other forces took over in our geopolitics.

    4. LF

      Do you have worries that, um, of existential threats of nuclear weapons or other technologies like artificial intelligence? Do you think we humans will tend to figure out how to not blow ourselves up?

    5. SJ

      I don't know quite frankly. Um, this is something I've thought about (laughs) and, uh, y- I'm not... I, I mean, uh, eh, so I'm a spectator in the sense that as a scientist I collect and collate data. And so I've been doing (laughs) that all my life and looking at my species, and it's not clear to me that we are going to avoid a cata- a catastrophic self-induced ending.

    6. LF

      (exhales) Are you optimistic? As a... Not as a scientist, but as a, uh, single-

    7. SJ

      I would, I would say-

    8. LF

      ... elf, speaking-

    9. SJ

      ... I wouldn't bet against us.

    10. LF

      Beautifully put. Let's dive into the, the world of the very small if we could for s- for a bit.

    11. SJ

      Certainly.

    12. LF

      What are the basic particles either experimentally observed or hypothesized by physicists?

    13. SJ

      So as we physicists look at the universe you can... First of all, there are two big buckets of particles, that is the smallest objects that we are able to currently mathematically, um, conceive and then experimentally verify that these ideas, uh, have an acc- uh, a sense of accuracy to them. So one of those buckets we call matter. Uh, these are things like electrons, uh, things that are l- like quarks, which are particles that exist inside of protons, and there's a whole family of these things. Uh, uh, there are in fact 18 quarks and apparently six electron-like objects that we call leptons, so that's one bucket. The other bucket that we see both in our mathematics as well as in our experimental equipment are what are a set of particles that you can call force carriers. The most familiar force carrier is the photon, the particle of light that allows you to see me. In fact, it's the same object that, uh, carries electric repulsion between like charges. Uh, from science fiction we have, uh, the object, uh, called the graviton which is talked about a lot in science fiction and Star Trek, but the graviton is also a mathematical object that we physicists have known about essentially since Einstein wrote his theory of general relativity. Uh, there are four forces in nature, the fundamental forces. There is the gravitational force. Its carrier is the graviton. There are three other forces in nature, the electromagnetic force, the strong nuclear force, and the weak nuclear force, and each one of these forces has, uh, one or more carriers. The photon is the carrier of the electromagnetic force. The strong nuclear force actually has eight carriers, they're called gluons, and then the weak nuclear force has three carriers, they're called the W-plus, W-minus, and Z bosons. So those are the things that both in mathematics and in experiments, the most... By the way, the most precise experiments we're a- ever as a species able to conduct is about measuring the accuracy of these ideas. And we know that at least to one part in a billion these ideas are right.

    14. LF

      So first of all, you've made it sound, um, both elegant and simple, but is it crazy to you that there is force carriers? Like is that supposed to be a trivial idea to think about? If we think about photons, gluons, that there's four fundamental forces of physics and then those forces are expressed... There's carriers of those forces. Like, um, is that a kinda trivial thing?

    15. SJ

      It's not a trivial thing at all. In fact, it was a puzzle for Sir Isaac Newton because he's the first person to give us basically physics. Before Isaac Newton, physics didn't exist. What did exist was called natural philosophy, so discussions about using the methods of classical philosophy to understand nature, natural philosophy. Uh, so the Greeks, uh, we t- call them scientists but they were natural philosophers. Physics doesn't get born until Newton writes the Principia. One of the things that puzzled him was how gravity works because if you read very carefully what he writes, uh, he basically says, and I'm paraphrasing badly, but he basically says that someone who thinks deeply about this subject would find it inconceivable that o- an object in one case, place, or location can magically reach out and affect another object with nothing intervening. And so it puzzled him.

    16. LF

      Does it puzzle you?

    17. SJ

      It doesn't-

    18. LF

      Action at a distance. I mean, not as a phys-

    19. SJ

      It, it would, it would, it would except that I am a physicist and we have long ago resolved this issue, and the resolution came about through a second great physicist. Most people have heard of Newton, most people have heard of Einstein, but between the two of them there was another extraordinarily great physicist, a man named James Clerk Maxwell. And Maxwell, between these two other giants, uh, taught us, uh, about electric and magnetic forces, and it's from his equations that one can figure out that there's a carrier called the photon. So this was resolved for physicists around 1860 or so.

    20. LF

      So what are bosons and fermions and hadrons-

    21. SJ

      Sure. (laughs)

    22. LF

      ... elementary and composite?

    23. SJ

      Sure. So earlier I said, uh-

    24. LF

      Two buckets.

    25. SJ

      ... you have got two buckets if you wanna try to build the universe. You gotta start off with, uh-

    26. LF

      Okay.

    27. SJ

      ... things from these two buckets. So you gotta have things, and that's the matter, and then you have to other, have other objects that act on them to cause those things to cohere to, uh, fixed finite patterns because you need those fixed finite patterns as building blocks. So that's the way our universe looks to people like me. Uh-Now, the building blocks do different things. Uh, so let's go back to these two buckets again. Let me start with the bucket containing the particle of light. Let me imagine I'm in a, a dusty room with two flashlights, and I have one flashlight which I direct directly in front of me, and then I have you stand over to s- say my left, and then we both take our flashlights and turn them on and make sure the beams go right through each other. And the beams do just that. They go right through each other. They don't bounce off of each other. The reason the room has to be dusty is because we wanna see the light. (laughs) If the li- the room... dust wasn't there, we wouldn't actually see the light until it got to the other wall, right? So you see the beam because there's dust in the air.

    28. LF

      Yes.

    29. SJ

      But the two beams actually pass right through each other. They literally pass right through. They don't affect each other at all. It... one acts like the other one's not there. Things... there are... the particle of light is the simplest example that shows that behavior. That's a boson. Now, let's imagine that I have to, uh... we're st- in the same dusty room, and this time you have a bucket of balls and I have a bucket of balls, and we try to throw them so that they pas- so that we get something like a beam, throwing them fast, right? Uh, if they collide, they don't just pass through each other. They bounce off of each other. Now, that's mostly because they have electric charge, and electric charges, like charges, repel. But mathematically, I know how to turn off the electric charge. If you do that, you'll find they still repel. And it's because they are these things we call fermions. So this is how you distinguish the things that are in the two buckets. They are either bosons or fermions.

    30. LF

      Which of them... and maybe you can mention the Hi- the, the most popular of the bosons. Just-

  4. 45:00 – 1:00:00

    And not just, I…

    1. SJ

      like humans and objects like planets and stars. So, although they are a scaffold for reality, they cannot be the entirety of reality. So I- I'm kind of naturally, uh, attracted to parts of science and technology where symmetry plays a dominant role.

    2. LF

      And not just, I guess, symmetry, as you said, but the, the magic happens when you break the symmetry.

    3. SJ

      The magic happens when you break the symmetry.

    4. LF

      Okay, so diving right back in, you mentioned four quadrants.

    5. SJ

      Yes.

    6. LF

      Two, two are filled with stuff we can...

    7. SJ

      We've measured.

    8. LF

      Two buckets.

    9. SJ

      Yep.

    10. LF

      And then there's crazy mathematical thing, ideas for filling the other two.

    11. SJ

      The other two.

    12. LF

      What, what, what are those things?

    13. SJ

      So, uh, earlier, the way I described these two buckets is I g- gave you a story that started out by putting us in a dusty room with two flashlights.

    14. LF

      Yeah.

    15. SJ

      And I said, "Turn on your flashlight, I'll turn on mine. The beams will go through each other." And the beams are composed of p- of force carriers called photons. They carry the electromagnetic force, and they pass right through each other. So imagine looking at the mathematics of such an object, which you don't have to imagine. People like me do that. Um, so you take that mathematics, and then you ask yourself a question. You see, mathematics is a palette. It's just like, uh, a musical comp- a musical composer is able to const- uh, to construct variations on a theme. Well, a piece of mathematics in the hand of a physicist is something that we can construct variations on. So even though, uh, the mathematics that Maxwell gave us about light, uh, we know how to construct variations on that. And one of the variations you can construct is to say, suppose you have a force carrier for electromagnetism that behaves like an electron in that it would bounce off of another one. And so that's changing a mathematical term in an equation. So if you did that, you would have a force carrier. So you would say, first, it belongs in this force carrying bucket, but it's got this property of bouncing off like electrons. So you say, "Well, gee. Wait, no. That's not the right bucket." So you're forced to actually put it in one of these empty quadrants. So those sorts of things, we g- uh, basically, we give them a... So the photon, uh, mathematically, can be accompanied by a photino. It's the thing that carries a force but has the rule of bouncing off. Uh, in a similar manner, you could start with an electron. And you say, "Okay, so write down the mathematics of an electron." I know how to do that. A physicist named Dirac first told us how to do that back in the 19 late '20s, early '30s. So take that mathematics, and then you say, "Let's, let me look at that mathematics and find out what in the mathematics causes two electrons to bounce off of each other, even if I turn off the electrical charge." So I could do that. And now let me change that mathematical term. So now I have something that carries electrical charge, but if you take two of them... Uh, I'm sorry. If you turn their charges off, they'll pass through each other. So that puts things in the other quadrant, and those things, we tend, we tend to call... We put the S in front of their name. So in the lower quadrant here, we have electrons. In this now newly, uh, filled quadrant, we have selectrons. In the quadrant over here, we had, um, quarks. Over here, we have squarks. So now we've got this balanced pie, and that's basically what I understood as a graduate student, uh, in 1975 about this idea of supersymmetry, that it was going to fill up these two quadrants of the pie in a way that no one had ever thought about before. So I was amazed that no one else at MIT found this an interesting idea. So that's, uh, it led to my becoming the first person, uh, at MIT to really study supersymmetry. Uh, this is 1975, '76, '77.... and in '77, I wrote the first PhD thesis in the physics department on this idea, uh, because I just, I was drawn to the balance.

    16. LF

      (laughs) Drawn to the symmetry. So what, uh-

    17. SJ

      To the symmetry.

    18. LF

      ... (sighs) what does that... First of all, is this fundamentally a mathematical idea? So how much experimental... And we'll have this theme, it's an really interesting one, when you explore the world of the small, and in your new book, uh, talking about, uh, proving Einstein right, uh, right, that we'll also talk about. There's this theme of kinda starting at, exploring crazy ideas first in the mathematics, and then seeking for ways to experimentally validate them.

    19. SJ

      The-

    20. LF

      Where do you put sup- supersymmetry in that ?

    21. SJ

      It's closer than string theory. Uh, it has not yet been validated. In some sense, as you mentioned Einstein, so let's go there for a moment. Uh, in our book, Proving Einstein Right, we actually do talk about the fact that Albert Einstein, in 1915, wrote a set of equations, which were very different from Newton's equations in describing gravity. These equations made some predictions that were different from Newton's predictions, and it actually made three different predictions. One of them was not actually a prediction, but a post-diction, because it was known that Mercury was not orbiting the sun in the way that Newton would've told you.

    22. LF

      Mm-hmm.

    23. SJ

      And so Einstein's theory actually makes, uh, describes Mercury orbiting in a way that it was, it was observed, as opposed to what Newton would've told you. So that was one prediction. The second prediction that came out of the theory of general relativity, which Einstein wrote in, uh, 1915, was that if you, uh, if you... So let me describe an experiment and come back to it. Suppose I had a glass of water-

    24. LF

      Mm-hmm.

    25. SJ

      ... and I filled it up, uh, filled the glass up, and then I moved the glass slowly back and forth between our two faces. It would appear to me like your face was moving-

    26. LF

      Hm.

    27. SJ

      ... even though you weren't moving. I mean, it's actually... And what's causing it is because the light gets bent through the glass as it passes from your face to my eye.

    28. LF

      That's right.

    29. SJ

      So Einstein, in his 1915, uh, theory of general relativity, found out that gravity has the same effect on light as that glass of water. It would cause beams of light to bend. Now, Newton also knew this, but Einstein's prediction was that light would bend twice as much. And so here's a mathematical idea. Now, how do you actually prove it? (laughs) Well, um, you've got to watch-

    30. LF

      Just-

  5. 1:00:00 – 1:15:00

    Do you think such…

    1. SJ

      bizarre and strange idea, and something I've wondered about from time to time since making these discoveries.

    2. LF

      Do you think such an idea could be fundamental or is it emergent throughout all the different kinds of systems?

    3. SJ

      I don't know whether it's fundamental, um, and I probably will not live (laughs) to find out. This is gonna be the work of probably some future either mathematician or physicist to figure out what these things actually mean.

    4. LF

      We have to talk a bit about the magical, the mysterious string theory.

    5. SJ

      (laughs)

    6. LF

      Super string theory.

    7. SJ

      Sure.

    8. LF

      There's still maybe this aspect of it which is, there's still for me, from an outsider's perspective, this fascinating heated debate on the status of string theory. Can you clarify this debate, perhaps articulating the various views and say where you land on it?

    9. SJ

      So, first of all, I doubt that I will be able to say anything to clarify, clarify the debate around string theory for, um-... for a general audience. Part of the reason is because string theory is, uh, has done something I've never seen theoretical physics do: it has broken out into consciousness of the general public before we're finished.

    10. LF

      (laughs)

    11. SJ

      You see, string theory doesn't actually exist, because when we use the word "theory," we mean a particular set of attributes. In particular, it means that you have an overarching paradigm that explains what it is that you're doing.

    12. LF

      Mm-hmm.

    13. SJ

      No such overarching paradigm exists for string theory. What string theory is currently is an enormously large mutually reinforcing collection of mathematical facts in which we can find no contradictions. We don't know why it's there, but we can certainly say that without challenge. Now, just because you find a piece of mathematics doesn't mean that this applies to nature. And in fact, there has been a very heated debate about whether string theory is some sort of hysteria among the community of theoretical physicists, or whether it has something fundamental to say about our universe. We don't yet know the answer to that question.

    14. LF

      Mm-hmm.

    15. SJ

      What those of us who study string theory will tell you are things like, string theory has been extraordinarily productive in getting us to think more deeply even about mathematics that's not string theory, but the kind of mathematics that we've used to describe elementary particles. There have been spinoff from string theory, and this has been going on now for two decades almost, that, uh, have allowed us, for example, to more accurately calculate the force between electrons, e- with the presence of quantum mechanics. This is not something you hear about in the public. There are other similar things. Um, the kind of, that kind of property I just told you about is what you call weak/strong duality, and it comes directly from string theory. There are other things such as, um, a property called holography which allows one to, uh, to take equations and look at them on the boundary of a space, and then to know information about inside a space without actually doing calculations there. This has come directly from string theory. So there are, there are nu- a number of direct mathematical effects that we learned as string theory, but we take these ideas and look at math that we already know, and we find suddenly we're more powerful. This is pretty good indication there's something interesting going on with string theory itself.

    16. LF

      So it's the early days of a powerful mathematical framework.

    17. SJ

      That's what we have right now.

    18. LF

      What are the big... First of all, th- for most people will probably, th- which as you said, most general public would know actually what string theory is, which is a, uh, at the highest level, uh, which is a fascinating (laughs) fact.

    19. SJ

      Well, string theory is what they do on the Big Bang Theory, right?

    20. LF

      (laughs) One, can you maybe describe what is string theory, and two, what are the open challenges?

    21. SJ

      (laughs) So what is string theory? Well, le- uh, the simplest explanation I can provide is to go back and ask, what are particles? Which is the question you first asked me.

    22. LF

      What's the smallest thing?

    23. SJ

      Yeah, what's the smallest thing? So particles, one way I try to describe particles to people is start, I want you to imagine a little ball, then I want you to let the size of that ball shrink until it has no extent whatsoever, but it still has the mass of the ball. That's actually what Newton was working with when he first invented physics. He's the real inventor of the massive particle, which is this idea that underlies all of physics. So that's where we start. It's a mathematical construct that you get by taking a limit of things that you know. So what's a string? Well, in the same analogy, I would say now I want you to start with a piece of spaghetti, so we all know what that looks like, and then I want you to let the thickness of the spaghetti shrink until it has no thickness. Mathematically... Uh, I mean, in words this makes no sense, but mathematically this actually works, and you get this mathematical object out. It has properties that are like spaghetti, it can wiggle and jiggle, but it can also move, uh, collectively like a piece of spaghetti. The, it's the mathematics of those sorts of objects that constitute string theory.

    24. LF

      And does the multidimensional, 11-dimensional, however many dimensional, more than four dimension, is that a crazy idea to you? Is that, is that the, the stranger aspect of string theory to you?

    25. SJ

      Not really. And also, partly because of my own research... So earlier we talked about Adin- uh, these strange symbols that we've discovered inside the equations.

    26. LF

      Mm-hmm.

    27. SJ

      It turns out that to a very large extent, Adinkras don't really care about the number of dimensions. They kind of have an internal mathematical consistency that allows them to be manifested in many different dimensions. Since supersymmetry is a part of string theory, then the same property you would expect to be inherited by string theory. However, another little-known fact which is not in the public debate is that there are actually strings that are only four-dimensional. This is something that was discovered, uh, at the end of the '80s by three different groups of physicists working independently. Uh, I and my friend Warren Siegel, who were at the University of Maryland at the time, were able to prove that there's mathematics that looks totally four-dimensional and yet it's a string. There was a group in Germany that used slightly different mathematics, but they found the same result. And then there was a group at Cornell who using yet a third piece of mathematics found the same result. So the f- the fact that extra dimensions is so widely talked about, uh, in the public, is partly a function of how the public has come to understand string theory and how it's, the story has been told to them, but there are alternatives you don't know about.

    28. LF

      If we could talk about maybe experimental validation and, uh-

    29. SJ

      Yes.

    30. LF

      ... you, you're the co-author of a recently published book, Proving Einstein Right, the, the human story of it too, the daring expeditions that changed how we look at the universe. Do you see echoes of the early days of general relativity in the 1910s to the more stretched out, to string theory-

  6. 1:15:00 – 1:25:39

    Mm-hmm. …

    1. LF

      Mm-hmm.

    2. SJ

      So this is in our book. So, putting myself in that time, I would want to, like you said, I think I would feel excitement. I would wanna know what the mathematics is and then I would want to do the calculations myself, because one thing that physics is all about is that y- you don't have to take anybody's word for anything. It's, you can do it yourself.

    3. LF

      It does seem that mathematics is a little bit more tolerant of radical ideas, or mathematicians, or people who, uh, find beauty in mathematics. W- why... all the why questions have no good answer, but let me ask. Why do you think Einstein never got the Nobel Prize for general relativity? He got it for the photoelectric effect.

    4. SJ

      That is correct. Well, the first of all, the, that's something that is misunderstood about the Nobel Prize in physics. The Nobel Prize in physics is never given for purely giving, uh, for purely proposing an idea. It is always given for proposing an idea that has observational support. So, he could not get the Nobel Prize for either special relativity nor general relativity because the provisions that Alfred Nobel left for the award prevent that.

    5. LF

      Uh, but after it's been validated, can he not get it then or no?

    6. SJ

      Yes, but remember the validation doesn't really come until the 1920s.

    7. LF

      Yeah, but that's why they invented the second Nobel Prize. I mean, uh, Marie Curie, you can get an second Nobel Prize for one of the greatest w- so-

    8. SJ

      So, let me-

    9. LF

      ... theories in physics, right?

    10. SJ

      So let me, let's be clear on this. The theory of general relativity had its critics even up until the '50s. So if you had w- if we had, if the committee had wanted to give the prize for general relativity, there were vociferous critics of general relativity up until the '50s. Einstein died in 1955.

    11. LF

      Yeah. What, what lessons do you draw from, from the story you tell in the book from general relativity, from the radical nature of the theory, t- to looking at the future of string theory?

    12. SJ

      Well, I think that the string theorists are probably going to retrace its path, but it's gonna be far longer and more tortuous, in my opinion. Uh, string theory, uh, is such a, uh, a broad and deep development that m- in my opinion, when it becomes acceptable, it's gonna be because of a confluence of observations. It's not gonna be a single observation. And I have to tell you that, um... so I gave a seminar here yesterday at MIT, and it's, it's on an idea I have about how string theory can leave signatures, uh, in the cosmic microwave background, which is this astrophysical structure. And so, if those kinds of observations are borne out, uh, if p- perhaps, uh, other things related to the idea of super symmetry are borne out, those are gonna be the first powerful observationally-based pieces of evidence that will begin to do what the Eddington expedition did in 1919. But who... that may take several decades.

    13. LF

      Do you think there will be Nobel Prizes given for string theory?

    14. SJ

      No.

    15. LF

      Because...

    16. SJ

      Because I think the orig- uh, because I-

    17. LF

      ... decades, decades-

    18. SJ

      It'll be, it'll be... I think it will exceed normal human lifetimes. And, but there are other prizes that are given. I mean, there is something called the, uh, Breakthrough Prize. Um, there's a Russian émigré, a Russian-American émigré named Yuri M- M- Milner, I believe is his name, started this wonderful prize, uh, called the Breakthrough Prize. It's three times as much money (laughs) as the Nobel Prize and it gets awarded every year. And so, something like one of those prizes is likely to be garnered at some point far earlier than a Nobel award.

    19. LF

      Jumping around a few topics...While you were at Caltech, you've gotten to interact, I believe, with Richard Feynman? I have to ask.

    20. SJ

      Yes. Uh, Richard Feynman, (laughs) indeed.

    21. LF

      Do you have any stories that stand out in your memory of that time?

    22. SJ

      Well, I have a fair number of stories, but I'm not (laughs) prepared to tell them. They're not- not all politically correct, (laughs) let me say.

    23. LF

      (laughs) But what-

    24. SJ

      Let me just say, I'll say the following. Richard Feynman, if you've ever read, uh, some of the w- books about him, in particular there's a book called Surely You're Joking, Mr. Feynman! Mm-hmm. There's a series of books that starts with Surely You're Joking, Mr. Feynman! And I think the second one may be something like, what Do You Care What They Say? Or something like, I mean, the titles are all... and there are three of them. When I read those books, I was amazed at how accurately those books portrayed the man that I interacted with. He was irreverent, he was fun, he was deeply s- intelligent. He was deeply human, and those books tell that story very effectively.

    25. LF

      Even just those moments, how did they affect you as a physicist?

    26. SJ

      Well, one of the thi- well, it's funny because one of the things that I didn't hear Feynman say this, but one of the things that is repu- re- reported that he said, is if you're on a bar stool... as a physicist, and you can't explain to the guy on the bar stool next to you what you're doing, you don't understand (laughs) what you're doing. And there's a lot of that that I think is correct, that- that when you truly understand something as complicated as string theory, when it's in its fully-formed final, uh, development, it should be something you could tell to the person on the bar stool next to you, and I, uh, that's something that, uh- affects the way I do science, quite frankly. It also affects the way I talk to the public about science, I- I- it's one of the, sort of my mantras that I keep deeply, uh, and try to keep deeply before me when I appear in public fora, uh, speaking about physics in particular, and- and science in general. It's also something that Einstein said in a different way. He- he said, uh, he had these two different formulations. One of them is when the answer's simple, it's God speaking. And the other thing that he said was that what he doe- what he did in his work was simply the distillation of common sense, that you distill down to something. And he also said you make things as simple as possible, but no simpler. So all of those things, and certainly this attitude for me, first sort of seeing this, was exemplified by being around Richard Feynman.

    27. LF

      So in all your work, you're always kind of searching for the simplicity, for the simple, clear-

    28. SJ

      I am, ultimately.

    29. LF

      ... fundamental idea.

    30. SJ

      I- ultimately, I am.

Episode duration: 1:34:59

Install uListen for AI-powered chat & search across the full episode — Get Full Transcript

Transcript of episode IUHkhB366tE

Get more out of YouTube videos.

High quality summaries for YouTube videos. Accurate transcripts to search & find moments. Powered by ChatGPT & Claude AI.

Add to Chrome