Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE - Don Lincoln | Lex Fridman Podcast #497

1. 0:00 – 0:49

   Introduction

   1. LFLex Fridman0:00

      The following is a conversation with Don Lincoln, a particle physicist at Fermilab who has spent decades working at the frontier of high energy physics. This was a mind-blowing and inspiring conversation. Don turned out to be one of my favorite people to talk to about physics. Truly a unique mind with that Richard Feynman ability of taking very complicated ideas and explaining them simply without losing any of the essential brilliant insights at the core of those ideas. This is a Lex Fridman podcast. To support it, please check out our sponsors in the description where you can also find ways to contact me, ask questions, give feedback, and so on. And now, dear friends, here's Don Lincoln.

2. 0:49 – 15:20

   Unifying the laws of nature

   1. LFLex Fridman0:49

      In describing the search for theory of everything in physics, you describe the history of physics can be told effectively as a kind of history of unifications. There's this centuries-long quest to show that, uh, these distinct phenomena are actually linked by some unified underlying principles, uh, even starting with Newton, that you can think of the effort of physics as one as trying to unify the laws of nature. So I was wondering if we could talk through the history of unification-

   2. DLDon Lincoln1:25

      Sure

   3. LFLex Fridman1:25

      ... that lens of physics.

   4. DLDon Lincoln1:28

      There are, of course, lots of different ways to do physics, but the, the way that I would say that particle physicists, cosmologists do is they are trying to, to really find basically the underlying principles that govern the laws o- of nature. If we go back, say to the, I don't know, 1650s or so, uh, you're the most brilliant person around and you've noticed two things. One you've noticed is that when you trip, you fall. That is the nature of gravity that, that we all experience day to day. But then there's sort of astronomy where you look out at the heavens and you see the stars march across the sky. You see the planets move through the stars. And there, th- that seems to have absolutely nothing to do with what happens when you drop your sandwich and, and the dog grabs it from you. So-

   5. LFLex Fridman2:20

      [chuckles] Yeah

   6. DLDon Lincoln2:21

      ... the brilliant thing was when Newton looked at that and he thought about maybe the moon is falling, but it's missing the Earth. So what we had is that in maybe 1650 you had what we might call the laws of celestial gravity, the gravity that governs the heavens, and terrestrial gravity, the gravity that is here on Earth. Now, we don't think of it that way anymore. We think of it as just gravity. But at that time, that wasn't at all obvious. And in fact, if you look in the books, Newton's theory is Newton's law of universal gravity. The universal is there and the reason is, is because he realized these two things that seemed to have nothing to do with one another were indeed one and the same. I mean, this is absolutely brilliant. I mean, Newton is arguably one of the most brilliant humans I, of which I'm ever aware. But at any rate, it is the first sort of easily to describe unification of physics that you can state in a way that sort of makes sense to, to modern-

   7. LFLex Fridman3:22

      Mm-hmm

   8. DLDon Lincoln3:23

      ... uh, humans. I mean, you can go back farther than that where people are talking about chemistry, the nature of atoms. You go back to Democritus who was wrong about very many things, but the idea that there was a smallest particulate form of matter is right. So it's kind of funny, you talk-- you, you read the chemistry books and they say that the idea of atoms goes back to Democritus and, you know, he, his idea was that like, um, there was a smallest atom of oil which was smooth and it was smooth of course because, well, oil is smooth. There was a smallest atom of vinegar because vinegar is tart and it pricks your tongue, so therefore atoms were little sharp, pointy things. Um, and so he was wrong about a lot, but he was right about the idea that there was a small particle and, and we now know a very-- we have a very different concept than he did. So you can go back farther than that. But getting the unification, there are more examples. For instance, if you go back to say 1830 or so, scientists were trying to understand electricity, for instance. And, uh, there was a lot going on. People really understood things, but at the time you would have two phenomena that are familiar to us now. One is a magnet, which, you know, at the time mostly magnets were, were simply little pieces of iron that had been magnetized and they could stick to steel. And then you had electricity, which was at the time they were generating little sparks that they could play and, and have fun with, or more broadly a, uh, a lightning bolt blazing across the sky. And so when you think about this, that lightning bolt and that little magnet seem to be really unrelated.

   9. LFLex Fridman5:02

      Mm-hmm.

   10. DLDon Lincoln5:02

       Um, but over the 1800s, a number of scientists were exploring little aspects of it. What happens when you run electricity through a wire? It seems to make a magnetic field. You know, they, they-- there was a whole bunch of experiments and there were a lot of names. But in about the 1860s or so, James Clerk Maxwell took all of those ideas that had been percolating around for the previous 50 years and wrote his laws of electromagnetism. And they're, they're really fascinating. If you look at the laws of electromagnetism, they are-- they're differential equations or inter- integral equations. But basically what they say is on one side you have a bunch of terms that have electricity in them, and then you have equals on the other side a magnetism thing.

   11. LFLex Fridman5:50

       Mm-hmm.

   12. DLDon Lincoln5:50

       So forgetting all of the mathematical symbols, you have electricity side equals a magnetism side. Electricity equals magnetism. And that is a staggering concept, the fact that these two things, a lightning bolt and the magnet that holds your kids' art to the refrigerator are one and the same. And this was another case where electricity and magnetism became unifiedInto electromagnetism. So now we have two examples. One, gravity being unified, terrestrial and celestial gravity, and then electricity and magnetism. So I'll, I'll tell you about some more in a moment, but one thing that's kind of important, because the goal is, of course, to, to unify everything. That if, if I could do what I want to do, I would have some unified theory that would explain all the behavior of all energy, matter, space, and time, which is a grand goal.

   13. LFLex Fridman6:39

       And, and we should say that maybe one of the goals of science more broadly, outside of physics even, is to construct, uh, models that can generalize, uh, the world. So if you look at Darwinian evolution-

   14. DLDon Lincoln6:55

       Mm-hmm

   15. LFLex Fridman6:55

       ... that was a very beautiful theory that captures another layer of reality of, like, how this particular thing that we see here on Earth happens.

   16. DLDon Lincoln7:07

       Right.

   17. LFLex Fridman7:07

       So when we talk about theory of everything in physics, that's capturing a different layer of abstraction about the functioning of the universe.

   18. DLDon Lincoln7:16

       Right. The whole Darwinian evolution, the fact that our genetics has significant overlap with the genetics of a banana is, is pretty staggering, is astonishing-

   19. LFLex Fridman7:26

       Yeah

   20. DLDon Lincoln7:26

       ... that that works. So that is amazing. Um, but for at least the class of, of scientists that I am, what we think of is, well, sure, biology is interesting and all, but when you get right down to it, it's, it's, it's caused-- Whatever happens in biology is caused by the movement of molecules. And then you say, "Well, that's great and all, but molecules, they do what they do because they're made of atoms."

   21. LFLex Fridman7:52

       Mm-hmm.

   22. DLDon Lincoln7:53

       And then the next step is, well, a- you know, atoms, that's great, but atoms work the way they do because of the nucleus and the electrons, and then the nucleus is protons and neutrons. And so s- there are those of us, myself included, who want to dig down to the very, very bottom and find out what is the smallest building block of nature from which all of these other far more complex and interesting and abstract things are. But what is at the very, very bottom? And also, that's great, but if you know, um, what the smallest building blocks are, that doesn't tell you the story. That's like having a whole bunch of Legos, but not knowing how to put them together. You also need to know how they interact, how they work, and so that's what we study forces. So there are the various subatomic forces of which we're familiar and, um, for instance, electricity and magnetism are components of electromagnetism, which then governs the behavior of things like-- This is amazing. Electrici- electromagnetism explains, of course, electricity, magnetism, but it explains how light works. It explains how much of chemistry works. So electromagnetism, 1860 or '70, uh, the wonderful thing about that is if you take Maxwell's equations and you apply a little bit of calculus, it's very easy to see that the laws of electricity and the laws of magnetism combined together make what's called a wave equation, which, that shows that these electric and magnetic fields oscillate. They, they vary, and if you have, uh, something that's varied, that's a wave, and the wave then moves. And if you do the math, you find out that the speed at which these waves move is the speed of light. And so people said, "Wow, the speed of light comes out of those equations." And that had to be, I think, very persuasive. And of course, electromagnetism also plays a really significant role in chemistry because after all, atoms are held together by electromagnetic forces. There's more to how atoms work. There is all the quantum mechanics stuff. But if you did not have electromagnetism, or if electromagnetism was very different, then atoms would be very different. So it plays a very big role in, in holding us together.

   23. LFLex Fridman10:09

       Mm-hmm.

   24. DLDon Lincoln10:09

       So it, it's a, a staggering advance in science to have a good behavior on that. And of course, being able to, to tame electromagnetism is why people can hear you when you do your podcast because through the miracles of the internet just-- or just electricity running the computers. I mean, this is a case, uh, if I can get on a small soapbox-

   25. LFLex Fridman10:35

       [chuckles]

   26. DLDon Lincoln10:36

       ... where people back then said, "Well, why are you messing around with magnets and sparks and who cares?" Well, that very fundamental digging into the laws of nature has spinoffs, and it has spinoffs. One of the big spinoffs is our entire technological society.

   27. LFLex Fridman10:54

       Mm-hmm.

   28. DLDon Lincoln10:55

       Without being able to govern electricity, we'd still be farmers and shoemakers in cities. Uh, we certainly would not have everything that we do. So off my soapbox. But it's really a lovely thing to show how this, this digging into deep, fundamental, not understood, mysterious things can, a hundred or two hundred years later, transform the world. And the type of science I do now, people often ask, "Well, what good is knowing about how the inside of atoms work, how the inside of quarks work?" And I don't know the answer to that. Um, but just being a little more pragmatic, if I go back, say, a hundred years, where people were trying to understand how the protons and neutrons inside atoms held together, how they split, how they, they, how you could combine them and so forth, this has led to nuclear power. Now, whatever you think about nuclear power, and some people like it, and some people don't, but it is powerful. It will generate, uh, energy for humanity. And, and it may be that is the path that, that we take as we move away from digging fossil fuels out of the ground. Humanity is going to need power no matter what. Nobody is going to go back to the way things were in the 1700s. And one-enormous source of energy that is there for us to take if we so choose is the modification of the nucleus of atoms. Seem to have absolutely nothing to do with anything, and yet it provides humanity with an opportunity, which of course requires that we think carefully of how we do that and, and if we want to, but it gives us something that we didn't have before.

   29. LFLex Fridman12:38

       Yeah. It's very clear that nuclear fusion and nuclear fission will unlock huge amount of energy that's required for a civilization to flourish, but that's almost like near term.

   30. DLDon Lincoln12:50

       Mm-hmm.
3. 15:20 – 32:27

   Einstein, special relativity, and general relativity

   1. LFLex Fridman15:20

      we talked about Newton. We talked about Maxwell. That takes us in the 20th century in terms of unification. There's a guy named Einstein-

   2. DLDon Lincoln15:27

      Mm-hmm

   3. LFLex Fridman15:28

      ... on whom you wrote a book, who did-

   4. DLDon Lincoln15:30

      Right

   5. LFLex Fridman15:30

      ... quite a lot of progress on the effort of unification.

   6. DLDon Lincoln15:33

      Sure. So Einstein, he's a pretty amazing guy. In 1905, he had his miracle year where he wrote multiple papers. The one that most people know about is special relativity, where he showed something that makes no sense to anybody who's not really dug into it very hard, and that is that two people experience time differently. Time, you know, is a fascinating thing. We don't really understand what time is, which is weird. You'd think that that'd be something we'd understand very well, but we really don't. We know a lot about it, but really understanding it, not so much. But, um, Newton thought that time was just universal for everyone. So my time, your time, some person's time on Mars or on Alpha Centauri, everybody experienced time the same. What Einstein showed was that that wasn't the case, that different people moving at different speeds with respect to one another experience time differently, which is absolutely a mind-blowing concept. Now, most people think that Einstein then said, well, he invented space time, that, that space and time are the same thing, and he was behind that. But that actual insight came from one of his teachers, a guy by the name of Minkowski, who looked at Einstein's equations. Minkowski was a little bit more mathematically inclined than Einstein, and he saw that if you look at the equations, you have basically one person's space and time equals some numbers times this person's space and time. And so that's kind of a, a staggering thing. So, so that is where Einstein and Minkowski really did this unbelievable concept that, that space and time are actually pretty much the same thing. That runs afoul of our understanding of how the world works because time just moves. It's continuous. We, we know what it is at a visceral level and an experiential level. We might not understand it at a formal level, but we know what time is. It's what keeps, makes today today and not yesterday or tomorrow. Space is a little different. You can walk somewhere. You can walk back. You can move around. You have more freedom to move in space than you have to move in time. You can always move forward in time. It's just moving backwards that turns out to be a little more difficult. But yeah, Einstein's understanding that that is the case, it caused everybody to think about the world very, very differently, and that was in 1908 when Minkowski really laid it out in a strict space time.

   7. LFLex Fridman18:14

      Uh, and that also led to the work on special relativityLed to the speed limit, the speed of light

   8. DLDon Lincoln18:21

      Well, it was a premise. He had two premises. One was that the laws of nature are the same for everybody. So if you're moving at some speed, or if I'm moving at some speed, I can say I'm not moving and saying you're moving at some speed. That's not controversial. That is what we call Galilean relativity. It's from hundreds of years ago. But what Einstein said that was controversial was that everybody measures that the speed of light is the same, irrespective of how we're moving with respect to each other. You'll measure the speed of light to be a number. I'll measure the speed of light to a number. And that's very, very different from what Newton would have said or Galilei or any of the old guys. And it was taking those two things together that caused all of the weirdnesses of special relativity. Now, you could then very easily say, well, that second premise that everybody measures the speed of light to the same is just dumb, and that you could test that. So that's where testing relativity comes in. And Einstein's equations, which include those two assumptions, it predicts the behavior of everything perfectly well. Now, we've actually measured, uh, done experiments where we can say that the speed of light is the same for everybody. That's not how that's been in the beginning. It was really that assumption leads to predictions. The predictions are true, so the assumption is true. Now, there is a-- for, for those people, for your viewers who want to say, "Well, how do you measure that the speed of light is the same for everyone?" The particle physicists do this, and the way you do this is the following. There are some subatomic particles that when they decay, they emit light. That's their decay product. And so you collide two things together so you know when the particle was created. Then you have surround your collision point by a detector, and you measure how long it takes for light to get to your detector, and by God, it's the speed of light, which it should be. However, sometimes in these collisions, some of these subatomic particles you make are coming out at very high speed. They might be coming out at ninety-five or ninety-seven or very large fraction of the speed of light, and then they decay into photons. And so you measure how long it takes for the photon to get to your detector, and it says its light travels at the speed of light. Now, if it were that-- if Einstein's conjecture was incorrect, you'd have a particle coming out at near the speed of light. It would be decaying into a particle traveling at the speed of light. Then that particle should have traveled at, say, two times the speed of light or something like that, so it should have taken half as much time to get to the detector, but it doesn't. So this is a hard, serious measurement that shows that something-- you know, we, we can measure the speed at which light comes out of this stationary created particle, and it's the speed of light. Then we can measure what the speed is of it coming out of something that's moving, and it's still the speed of light. So that is an actual measurement, but that is not something that was possible in Einstein's day, but it is now.

   9. LFLex Fridman21:42

      Just to take a small tangent, uh, how weird is it in the full ranking of weirdness that is physics, how weird is it that there's that speed limit of the s- speed of light?

   10. DLDon Lincoln21:53

       Well, I have to tell you, when I first encountered this, it's pretty freaking weird. It's like pegs the weird meter. But as you become more familiar with it, as you become more, more comfortable with the idea, the thing to remember is the speed of light, it's the speed of light through space-time. Once you embrace that, that makes a whole ton of sense. It all of a sudden makes everything fall much more into place. I think that there is an ultimate speed isn't that shocking. It just simply says that it's a property of space in the same way that there is-- you know, space can, can transmit a certain strength electric field. It c- trans-- It can support a certain things. Whatever space is, and we don't know what space is, but whatever it is, it has the capability of, of transmitting these things at that one speed through space or time, and everything else comes from our insisting that we keep space and time different. That's, that's how I view it. And at least for me, that-- o-once I accepted that, it all became very comfortable.

   11. LFLex Fridman23:06

       So the nature of my question actually here-

   12. DLDon Lincoln23:09

       Mm-hmm

   13. LFLex Fridman23:09

       ... that will apply over and over is trying to empathize, trying to put ourselves in the shoes of the people before space and time are unified-

   14. DLDon Lincoln23:17

       Yes

   15. LFLex Fridman23:17

       ... into space-time, and, and really experience and think through how difficult of a leap is that.

   16. DLDon Lincoln23:24

       Huge.

   17. LFLex Fridman23:25

       The, the reason I, I, uh, sort of say that is we are now in the modern day in the twenty-first century, and of course, we're gonna have to make leaps like that in our future.

   18. DLDon Lincoln23:36

       Mm-hmm.

   19. LFLex Fridman23:36

       So what are the unifications we're not seeing in front of our eyes? So for example, there's so many examples through, through your work, through your lectures of, um, uh, Paul Dirac taking antimatter seriously.

   20. DLDon Lincoln23:50

       Mm-hmm.

   21. LFLex Fridman23:51

       Looking at what the math shows and saying, "I really think this thing exists."

   22. DLDon Lincoln23:57

       Right.

   23. LFLex Fridman23:57

       I mean, it just sounds insane.

   24. DLDon Lincoln23:59

       It does.

   25. LFLex Fridman24:00

       And so I think this is a good warm-up. The space-time unification [chuckles] is a good warm-up as we march through the twentieth century because it gets, uh, in my view at least, weirder and weirder, even with Ein-Einstein himself.

   26. DLDon Lincoln24:13

       Well, let me give you an even more basic example, sodium and chloride.Sodium is an explosive metal. You put it in water and, and it's kind of neat. You, you put it in water and it just, it doesn't quite explode, but it gets hot and it pops around. Chlorine, it's a gas, it's going to kill you. So these two things are deadly. They're awful. And yet when you mix them, you put it on your food at night. It's salt, right? And so this is a case where, where this whole, A, unification, and B, this deeper understanding, in this case of chemistry, of how two things that, that are dangerous can be brought together and turned into something not only innocuous, but necessary for human life. And so this is not unusual, the, what, what you're describing. I mean, when you think about it, forget about everything else, just the fact that, you know, we tell little kids, little kids, that the world is made of atoms. Now, that's crazy. Most people have never seen atoms, and yet nobody really doubts it anymore. And I think it's just a, a case of, of familiarity, and then the culture slowly accepts it, and it's then, it's real even without the evidence. In fact, one of the courses you described there, um, how we know what we know, I think that's a valid question. How do we know there are atoms? And, and of course, there are ways we do.

   27. LFLex Fridman25:35

       And by the way, on that front, I would love to go through how we know the building blocks in the universe as we march towards quarks. That, in the course that you mentioned, is one of the most fascinating things of this philosophy of atoms being around for a very long time. Then you concretize and you actually can prove or have s- strong observations that indicate that there is atoms, and then there is a nucleus, there is electrons, there is photons, there is quarks and leptons. I mean, it gets weirder and weirder, and now we're facing the mystery is there's building blocks even smaller than that.

   28. DLDon Lincoln26:12

       Mm-hmm.

   29. LFLex Fridman26:12

       But anyway, Einstein, turns out, didn't just do special relativity. By the way, I, I really think he deserves three Nobel Prizes. He got it for photoelectric effect. The fact that he didn't get it for general relativity is a crime against humanity. I don't understand. Obviously should have gotten it for general relativity and, and special relativity.

   30. DLDon Lincoln26:33

       Mm-hmm.
4. 32:27 – 44:09

   Electroweak force

   1. DLDon Lincoln32:27

      Right.

   2. LFLex Fridman32:28

      And the unifications continue that as we, uh, take steps towards the standard model-

   3. DLDon Lincoln32:33

      Yeah

   4. LFLex Fridman32:33

      ... which is such an incredible part o- of physics in the 20th century. So can you describe that unification?

   5. DLDon Lincoln32:39

      So, you know, we're sort of jumping forward here now to the 1930s or thereabout, and at, by that time, people had realized that there are four distinct forces that do not seem to be connected. One is gravity, two is electromagnetism, and those are things people are relatively familiar with. But there are two other forces that only have any real importance inside the nucleus of atoms, which is why most people have no experience with them. One is the strong nuclear force, which holds the nucleus of the atoms together, and the other one is what we call the weak nuclear force, which is responsible for some types of, of radioactivity. And since most people don't play around with nuclei, and most people don't play around with radioactivity, they don't know what that is. But, um, by the '30s, scientists had done enough experiments, done enough theorizing to, to say that there were these four forces, and that was already a triumph. I mean, we, in our goal for a theory of everything, we'd like to think that there is one force, which is what we're talking about, the unification. Maybe these four forces are, are just different ways of looking at a single underlying force. But in the '30s, that's where we were. There were the four forces. So we move ahead, and in the late '50s and early '60s, some people were thinking that maybe the weak nuclear force and electromagnetism actually were the same. So they were working on trying to bring together these two forces to show that they're connected, and it came true. They were able to show that electricity and magnetism were actually two different facets of a single force that we now call the electroweak force.

   6. LFLex Fridman34:36

      Mm-hmm.

   7. DLDon Lincoln34:37

      Now, the story that you're told in, in articles about this, about what you- people have called the Higgs boson or the God particle, the story is very, very simplified because in 1964, the, um, there were three groups with six individuals who came up with important papers talking about what's called the Higgs field, and I'll get to back-- get to what that is in a minute. But the Higgs field is important. But it wasn't until 1967, so three years later, that Steven Weinberg and, and some others actually unified electromagnetism and the weak force.

   8. LFLex Fridman35:18

      Sheldon Glashow, Abdus Salam, and Steven Weinberg successfully unified ele- electromagnetism and the weak nuclear force that, uh, showing that at high energies-

   9. DLDon Lincoln35:30

      Right

   10. LFLex Fridman35:30

       ... uh, these two forces were merged into a single electroweak force.

   11. DLDon Lincoln35:34

       Right, and that was in '67. All right? Um, everybody talks about this thing happening in '64, but it, it really wasn't. It happened over quite a few years, actually. But all right, so now let's-- what, what you said is true. So, um, uh, Weinberg, Glashow, and Salam showed that electromagnetism and the weak force at high energies were the same. There was a problem, however, and the problem is that electromagnetism has an infinite range, um, and we know that because we can see stars that are millions of light-years away. I mean, that shows you that the range of that force is essentially infinite.

   12. LFLex Fridman36:15

       Mm-hmm.

   13. DLDon Lincoln36:15

       The weak force, however, um, basically becomes nonexistent on distances much smaller than the size of a proton.

   14. LFLex Fridman36:24

       Mm-hmm.

   15. DLDon Lincoln36:25

       So that, you know, to say, "Oh, they're the same," and yet one can reach across the universe and one can't reach out of an atom, well, that's just dumb. I mean, the obvious-Thought here is, well, w- we just proved that that whole idea is stupid, so throw it away. Ridiculous. And that is where these ideas from 1964 came in and saved the day. So how can it be true that the electroweak force is real and electromagnetism and the weak force act so differently?

   16. LFLex Fridman37:01

       Mm-hmm.

   17. DLDon Lincoln37:02

       The way that could happen is if these forces were transmitted by a particle moving from one subatomic particle to the other. In the case of electromagnetism, it's the photon. In the case of the weak force, we call them now the W and Z particles. So the idea is that, that Higgs and his colleagues came up with is saying, "All right, electroweak force is real. The way we make it so that there is now an electromagnetic force and a weak force is the force-carrying particle of electromagnetism has no mass. The force-carrying particle of the weak force has a mass." And so what was done is a field was postulated that there was this additional field that was kind of distinct from this electroweak field, and we call it the Higgs field. And the Higgs field permeates all of space. And, and here's the kicker, some particles interact with the field, and some particles don't interact with the field. The ones that interact with the field get mass, and the ones that don't interact with the field don't have mass. And so that's the idea, is that the Higgs field gives the weak force particles mass. However, the photon laughs at the Higgs field, doesn't see it, and it has no mass.

   18. LFLex Fridman38:40

       And I should say here, going to Perplexity, the big picture view, the Higgs field is the quantum field that fills all of space and gives many elementary particles, just as you're saying, their mass through their interaction with it. The Higgs boson is the particle associated with ripples or excitations of this field. In modern particle physics, every type of particle corresponds to a field that exists everywhere. The Higgs field is one such scalar field, meaning at each point in space, it has a single numerical value rather than a direction. The Higgs field differs from most other fields because even in empty space, empty in quotes, by the way, empty space, its, uh, average value is not zero. This non-zero vacuum value is what enable it to endow particles with mass.

   19. DLDon Lincoln39:31

       Right. So let's talk about something a little more familiar, just to, to try and hang some, some intuition on those words.

   20. LFLex Fridman39:38

       Awesome.

   21. DLDon Lincoln39:39

       All right. So right in front of us, there is a gravitational field. Now-

   22. LFLex Fridman39:42

       Mm-hmm

   23. DLDon Lincoln39:43

       ... you can't see it, but right there.

   24. LFLex Fridman39:45

       Mm-hmm.

   25. DLDon Lincoln39:45

       Right there. Check it out.

   26. LFLex Fridman39:46

       Yep.

   27. DLDon Lincoln39:47

       If I were to take something, a pen or whatever, and put it there, it feels a force and it falls.

   28. LFLex Fridman39:53

       Mm-hmm.

   29. DLDon Lincoln39:53

       Very insightful, I know. So we have the gravity field, and we have the pen that has a mass, and the mass and the gravity field interact, and it drops. Now, if we had another-

   30. LFLex Fridman40:07

       I have a-
5. 44:09 – 1:02:12

   How particle colliders work

   1. DLDon Lincoln44:10

      So the Higgs boson idea was predicted in '64. It became useful in '67, and then scientists started looking for it. So in the early 2000s, people were starting to think that we had built part of, particle accelerators more powerf- or powerful enough to actually to be able to create these vibrations and detect them. So the accelerator that was working at the time was a large particle accelerator outside Chicago at Fermilab called the Tevatron.

   2. LFLex Fridman44:43

      Mm-hmm.

   3. DLDon Lincoln44:44

      And we were colliding protons and antimatter protons at near the speed of light at very high energy, and that was the accelerator at which the top quark was discovered in '95. But we had upgraded our apparatus. We had 10 times the number of collisions per second. We had slightly more energy, and we were banging the protons and the antimatter protons together, hoping that we would actually find the Higgs boson.

   4. LFLex Fridman45:09

      Can you actually back up a little bit and, uh, look at the bigger picture? So Fermilab has this legendary accelerator that there's also a personal story with you connected to it because, I mean, there's a million questions I'll, uh, I wanna ask you, and we'll ask you about some aspects of that. So this idea of an accelerator, the design and the physics of an accelerator, how is that productive for understanding and discovering, uh, different aspects of particle physics?

   5. DLDon Lincoln45:37

      Well, I'm so glad you asked. [chuckles] I mean, this is fascinating. All right.

   6. LFLex Fridman45:42

      Yeah.

   7. DLDon Lincoln45:42

      Everybody has heard Einstein's equation, E equals MC squared. Nobody knows what it means. Maybe they heard that energy equals mass and mass equals energy. I don't know, you know, but they heard the equation, the most famous equation in all of science. But buried inside that equation is a really thoroughly fascinating concept, that energy and matter are equivalent. And you can, in fact, convert movement energy into mass. And so this is something that we've known for a long time. This was predicted back in basically 1928, so a long time ago, actually almost 100 years ago. And it is not in the slightest bit controversial. We can do this all the time. So the simplest thing is to take two particles that have no, no structure, so, you know, the closest thing you can have to BBs that are just true mathematical BBs. If you smash those two things together, it's coming in with a huge amount of energy from one direction, a huge amount of energy from the other direction. The directions cancel, so the net momentum, the net energy of this has no motion. So you have these two things coming in with a, a, you know, exactly balanced energy, and if they collide, they could stop. Well, that energy has to go somewhere, and that energy can literally create mass, create particles. Now, there are special rules about what happens. If you have two things coming together and it creates a particle, it has to create an antimatter particle to balance it. That's just kind of the rules of the laws of nature. Why is that the case? Well, we have some ideas, but in many respects, the answer is because those are the laws of the universe, and that's the things that we try to understand.

   8. LFLex Fridman47:33

      Mm-hmm.

   9. DLDon Lincoln47:33

      But this is absolutely true. So what, what particle accelerators do, among other things, is simply transform energy into particles. And so basically, any, uh, uh, particle that doesn't exist in nature, we can make in this way. You can make the antimatter electron by taking two particles, smashing them together. The energy sits there, and it will make an electron and an antimatter electron, and it just does. And we know that. The antimatter electron was discovered in 1932. This is all pretty easy. The antimatter proton was discovered in 1955 at the Berkeley Bevatron. And so this is just what you do. You can convert energy into a matter-antimatter particle. Now, the converse goes true, and that's something we might talk about. You can take matter and antimatter and bring it together, and it'll make energy. It's the, uh-The process can go th- both ways. Energy can make matter and antimatter. Matter and antimatter can make energy, and this is just true. We do it all the time. There's no question that this is the case.

   10. LFLex Fridman48:45

       And we should also mention that, uh, this is the reason why Fermilab had a nice stash of antimatter particles. Uh, so as, as a side effect, you can also collect antimatter in this kind of way.

   11. DLDon Lincoln48:56

       Sure.

   12. LFLex Fridman48:57

       You can produce antimatter, but it's an extremely costly-

   13. DLDon Lincoln49:00

       Oh, very, very costly. Um, in order-- at, at the Fermilab machine, we would have to smash 100,000 protons into something to make one antimatter proton. So I mean, it, it, it took some work. [chuckles]

   14. LFLex Fridman49:14

       Is there some extremely precise recipe of, uh, of being able to produce particular kinds of particles and all this kind of stuff when you smash two things toget- uh, together? Is there, like, s- how can you control accurately which kind of particles you're trying to produce?

   15. DLDon Lincoln49:32

       If you wanna make antimatter electrons, you smash together energy n- at a certain-- It's just easier with electrons because the electrons, to the best of our knowledge, have nothing inside them, so they're simple. They have a certain mass, and that's that. So if you smash t- particles together with the right energy, you can make them very, very easily because you can-- it's like a, uh, old style radio back in the day where you had to dial it in. You could get right on the station, and you could hear the, the signal, and if you were off a little, it didn't work. The problem for things like protons and so forth is they're not point-like particles. They're kind of like garbage cans full of stuff, and so it's very difficult to make antimatter protons. Now, you can get more of them by increasing the, um, energy at which you collide two particles together. If you're at below a certain energy, the-- and you collide, say, you collide two protons together at kind of low energy, you just don't have enough energy to make an antiproton.

   16. LFLex Fridman50:32

       Mm-hmm.

   17. DLDon Lincoln50:33

       And so it doesn't happen. You get to a certain energy, and you can just barely make them. The more energy you collide them together, the more you make. So that is just sort of how it works. M- more is better.

   18. LFLex Fridman50:45

       And then, uh, with, with CERN, if you compare s- maybe CERN and Fermilab, going to Perplexity here, CERN's accelerator, the Large Hadron Collider, LHC, is the world's highest energy proton collider, while Fermilab's current and planned accelerators focus on intense proton beams for neutrino physics-

   19. DLDon Lincoln51:05

       Correct

   20. LFLex Fridman51:05

       ... rather than pushing the absolute energy frontier. Absolute energy frontier meaning highest possible energy smashing of protons together.

   21. DLDon Lincoln51:16

       Correct. So one, we were talking about, like, accumulating antimatter.

   22. LFLex Fridman51:20

       Yes.

   23. DLDon Lincoln51:21

       All right? And so, um, there, that is typically making antiprotons, as opposed to making all particles in general. So let's focus on the antiproton side to begin with.

   24. LFLex Fridman51:32

       Mm-hmm.

   25. DLDon Lincoln51:32

       All right? So Fermilab doesn't make antiprotons anymore. We stopped making them in 2011, and it's because we shut our big accelerator down to concentrate on a different facet of particle physics. However, at the time, we would smash, um, protons with a, an energy of 120 GeV, and in that, we would make antiprotons. So that's a ton of energy. It's true that the CERN accelerator, the big accelerator, is now much higher energy than the Fermilab accelerator was. No problem. But that's not how they make antiprotons. The-- A- all of these big beam, uh, big laboratories, it's not one accelerator. At Fermilab, there were five distinct accelerators, and it was basically like shifting an old standard car 'cause you couldn't just go zero to super speed in one accelerator. You had to go from one to another, getting higher and higher. Well, at CERN, they use one of the, basically their second gear in their very big accelerator complex to make antimatter protons, and their accelerator is only 26 GeV compared to the 120 GeV at Fermilab.

   26. LFLex Fridman52:47

       Mm-hmm.

   27. DLDon Lincoln52:47

       Fermilab's not operating, but when it was operating, it operated at an energy about four times higher than what CERN is doing now. And why is that? Well, it's because what CERN needs to do is to not make as many antiprotons as Fermilab did. They are doing a very different current experimental program. They're doing a fascinating experimental program, including trying to figure out does antigravity fall up or down, which is kinda neat. And we sort of know the answer to that. Different q- That, that's separate. But anyways, so getting back to the antiproton business-

   28. LFLex Fridman53:20

       Yeah

   29. DLDon Lincoln53:21

       ... while Fermilab doesn't do it now, it was top dog. It's not anymore. Um, the only really big antiproton accelerator creator is a small accelerator at CERN.

   30. LFLex Fridman53:31

       Mm-hmm.
6. 1:02:12 – 1:12:32

   Higgs boson discovery

   1. LFLex Fridman1:02:12

      Uh, so take me to, uh, July 4th, 2012, the discovery of Higgs boson.

   2. DLDon Lincoln1:02:19

      So this is really fun because the people searching for the Higgs, it's a, it's a community, and the entire community knew that the LHC was coming online. So even though many of us had been working on the Fermilab accelerators, a lot of us were transitioning to the CERN, uh, accelerator. So we were in the very funny business of wearing our Fermilab detector people hats, trying desperately to find the Higgs boson at Fermilab-

   3. LFLex Fridman1:02:51

      Mm-hmm

   4. DLDon Lincoln1:02:52

      ... while simultaneously wearing our CERN hats, knowing that CERN was going to be able to find it if existed. And so, you know, we were a little neurotic, s- kind of wanted, you know, our, our old stuff to work and, and there was an awful lot of people on both experiments.

   5. LFLex Fridman1:03:08

      Did you, um, have a sense that one of the two places would be able to find the Higgs? First, did you think the Higgs boson existed? And second, did you think that these accelerators have the chance to find them?

   6. DLDon Lincoln1:03:22

      So I was cognizant of the fact that the Higgs boson might not exist, but there was a lot of evidence pointing in the direction that it might be. I knew that both experiments, the Fermilab accelerator and the CERN accelerator, would either find or rule out the Higgs if it existed.

   7. LFLex Fridman1:03:42

      Rule out?

   8. DLDon Lincoln1:03:43

      Well, that's a possibility. I mean-

   9. LFLex Fridman1:03:44

      Yeah

   10. DLDon Lincoln1:03:44

       ... maybe the Higgs theory was wrong.

   11. LFLex Fridman1:03:46

       Yeah.

   12. DLDon Lincoln1:03:46

       Right? Until you, till you know it's there, it might be wrong. It's like dark matter. People talk about dark matter, it might not be real.

   13. LFLex Fridman1:03:52

       Mm-hmm.

   14. DLDon Lincoln1:03:52

       I mean, I-- it probably is, but it might not be.

   15. LFLex Fridman1:03:55

       So you knew at these energy levels you would be a- you should be able to find-

   16. DLDon Lincoln1:03:58

       Yes

   17. LFLex Fridman1:03:58

       ... the Higgs boson.

   18. DLDon Lincoln1:03:59

       Yes. So that's the nice thing about this kind of physics, because there was a theory, that theory made predictions. Now, there were parameters in the theory we didn't know. If the mass was this, we'd get this thing. If the mass was this, we'd get this thing. But we could do the, the calculation for every conceivable Higgs mass, and so then we could search. Look, well, let's say the Higgs mass is 100 in some units. Did we see it there? No. Then it's not 100. Well, let's look at 103. Is it there? No. So we could do that. Both accelerators could either find it or definitively rule out the predictions of simple Higgs theory, 100% guaranteed.

   19. LFLex Fridman1:04:44

       Mm-hmm.

   20. DLDon Lincoln1:04:45

       However, the CERN accelerator had 10 times the collisions per second and three and a half times the energy. So remember when I said it-- with the top quarks, it was like six months for 19 versus one a second? There's no question. The writing is on the wall. The Hi- the, the LHC was gonna have an easier time of it-

   21. LFLex Fridman1:05:08

       Yeah

   22. DLDon Lincoln1:05:08

       ... if it was real. However, so but, you know, I'm a Fermilab scientist, and we wanted Fermilab, you know, come on, we want Fermilab-

   23. LFLex Fridman1:05:15

       Yeah, of course

   24. DLDon Lincoln1:05:15

       ... to win, not, you know.

   25. LFLex Fridman1:05:16

       Yeah.

   26. DLDon Lincoln1:05:16

       So we were busting our butt, and we had done what I said. We had ruled out this region. We had certain ra- mass ranges. We knew it wasn't there. And we finally said, if there was a Higgs boson, if it existed, which we didn't know at the time, its mass was somewhere between, if I recall, between, like, 120 and 145. All right? We'd ruled out all the other stuff. And so wearing our, our CERN hat, we said, "Okay, we're gonna find that." But we were really, really, really trying to do it. Now, if we had had another two years or maybe three years of running the Fermi accelerator, Fermilab would have discovered or ruled out, or in this case, turned out, discovered the Higgs boson, 'cause it's a real thing. We would have found it without a question. But we didn't have enough data in July of 2012. We needed a couple more years. Unfortunately, in 2008, or fortunately, the LHC had turned on. It broke. They had to fix it. Turned on again in 2010. It ran poorly in 2011. In 2012, they pushed up their sleeves and said, "Let's do this," and it turned on. And so, you know, there was this-- the Fermilab knew if it didn't have it now, it wasn't-- it, it, it was too late. Anyways, come-- 2012 rolls around and, um, like two days before, uh, the, the announcement at CERN was July 4th, so two days before that, Fermilab made a measurement and said, "We can rule outCertain regions, but certain regions we can't rule out. But what we know, and this is important, if the Higgs boson exists, it must be in this region for which we are not capable yet of ruling out.

   27. LFLex Fridman1:07:08

       Yeah.

   28. DLDon Lincoln1:07:08

       So that's where we were two days before the LHC said, "We got it." That was, uh, July 4th, 2012.

   29. LFLex Fridman1:07:20

       So detecting the, the Higgs boson confirmed the existence of the Higgs field, the mechanism through which fundamental particles like electrons and quarks acquire mass in the standard model.

   30. DLDon Lincoln1:07:31

       Correct. Although, let's be very specific of what we did then. We found a particle consistent with the existence of the Higgs boson. There were alternative theories at the time that predicted not one, but multiple Higgs bosons. So there's a th- theory called supersymmetry, which said that there was not one, but five Higgs bosons. The standard original 1964 Higgs theory says there were one. And so all we really knew at the time was we found a theory. We did not necessarily confirm that Higgs was right. We found data that said that it looked like Higgs was right. But until we ran for longer, we were unable to rule out other alternative theories.
7. 1:12:32 – 1:42:17

   Theory of everything

   1. LFLex Fridman1:12:32

      We did a whirlwind tour [chuckles] of the history of physics and took a little tangent on this incredible discovery of the Higgs boson. Uh, but we didn't go all the way yet. There's this dream of the grand unified theory, the GUT, that, uh, is a step towards the ToE, theory of everything. So can we talk about the GUT first? So what, what, what's, what's entailed in the GUT?

   2. DLDon Lincoln1:12:58

      So the GUT is short for Grand Unified Theory. We talked about that there were four known subatomic forces, the, um, electromagnetic force, gravity, the strong force, and the weak force. And electroweak symmetry unification merged the weak force and electromagnetism into the electroweak force. So what GUT hopes to do is to merge the electroweak force and the strong force into one grand unified force. Now, that leaves gravity outside because gravity is seemingly fundamentally significantly different.

   3. LFLex Fridman1:13:32

      Mm-hmm.

   4. DLDon Lincoln1:13:32

      Then subsequently, it is hoped that a higher energy, we will be able to blend the theory of everything together with all of the known subatomic forces, the strong, weak, and electromagnetic forces, and then gravity. But so as you say, GUT is sort of a, a, a way station along the way. That's the goal and, uh, at this point, I would have to say that I do not see a fast progress in the immediate future. I think we're a ways away from that at this point.

   5. LFLex Fridman1:14:02

      You mean on the gravity front?

   6. DLDon Lincoln1:14:04

      Maybe we'll come up with something really cool. We certainly had some ideas back in the early '80s that we tested, and they didn't pan out.

   7. LFLex Fridman1:14:12

      Uh, speaking of which, string theory is the thing you're referring to.

   8. DLDon Lincoln1:14:16

      Mm-hmm.

   9. LFLex Fridman1:14:16

      Uh, [chuckles] so string theory posits that particles are tiny vibrating strings, and by tiny we mean extremely tiny at the scale of a Planck length. Uh, then there's, there's other leading candidates like loop quantum gravity. Um, maybe there's some alternate theories in the works. So can you, uh, link on that a little bit more? Do you think a theory of everything exists?

   10. DLDon Lincoln1:14:42

       So I hold personally that there are rules that govern matter and energy, space, time, and they probably are rules that I don't know. There are probably phenomena I'm not aware of. But I do believe that something, there are, is a rule that governs reality. And so in that sense, once we understand the rules that govern reality, the fundamental rules, that would be a theory of everything. You know, there are things that are unknowable, like for instance, inside black holes, we don't know what's inside there, but that doesn't mean that there's not something inside there. So there's a distinction between what we can know and truth.

   11. LFLex Fridman1:15:20

       Mm-hmm.

   12. DLDon Lincoln1:15:20

       So I, I, I do believe that there are the rules, and I do believe that with sufficient time, technology, effort, we will be able to figure this all out. Now, this isn't a thing in my lifetime. It's not a thing in my grandchildren's lifetime or even their grandchildren's lifetime.

   13. LFLex Fridman1:15:38

       Whoa, whoa, whoa. That's a pretty strong statement, right?

   14. DLDon Lincoln1:15:40

       Yeah.

   15. LFLex Fridman1:15:40

       That's a pretty strong statement saying we're, we're 50 to 100 years out from finding a theory o- of everything.

   16. DLDon Lincoln1:15:48

       It took 200 years to go from unifying gravity to unifying electromagnetism. It took 100 years to go from unifying electromagnetism to unifying the electroweak force. Now you could say, well, gee, that's went from 200 to 100, so it's getting faster, but it's also getting harder because the unification scale is of order 10 to the 15, which we can do the math. That's a quadrillion times higher than the highest energy accelerator we can build today.

   17. LFLex Fridman1:16:19

       Mm-hmm.

   18. DLDon Lincoln1:16:19

       And it was one thing to, you know, we are reaching diminishing returns. We get something like a factor of seven increase in particle accelerator energy every 20 years, and so we have to get to a quadrillion times. Now, you know, if you really did believe, uh, a factor of seven every 20 years, then that's, we're talking like 500 years. But, you know, this is like Moore's law, that it doesn't continue forever. We're not going to every seven year-- I mean, every 20 years get another factor of seven. So yes, I, I think it's a very long time. That's my prediction. Um, you know, some people are far more optimistic, and we can talk about that.

   19. LFLex Fridman1:17:00

       We should also, I should mention that I guess your intuition behind that is not just the part where you come up with a theory that's beautiful and seems to be internally consistent, but you have to have a theory that's making falsifiable, testable predictions.

   20. DLDon Lincoln1:17:19

       Correct.

   21. LFLex Fridman1:17:20

       And you have to have a, a feasible engineering construction, a methodology for creating an experiment that tests that prediction. So I think a lot of your, this is 50, 100, 200 years from now, intuition is maybe about the second part of that, which is like you need to have an experiment.

   22. DLDon Lincoln1:17:41

       Ye- y- yes. Yes. But, you know, let's say, I mean, w- w- you alluded to superstrings. I haven't answered that question. I'll table that for a moment. Superstrings is a fascinating idea. I don't believe it, um, but I love it. I hope it's true. And there's a real, you know, uh, aphorism, and it says, "You should absolutely never believe what you think." So even if you think superstrings is true, you shouldn't believe it because it hasn't been tested.

   23. LFLex Fridman1:18:06

       Mm-hmm.

   24. DLDon Lincoln1:18:06

       Now, let's say superstring is correct. I mean, hypothesis, it's correct, 100% correct. I don't know it's correct, so w- I don't care. I mean, you know, it could be correct, but I don't, you know, until it's validated, it's just a wild ass guess. You know? So I, we have to have a way of validating it. So yes, the, the, the empirical side of it is important. I mean, you could wake up tomorrow and have the theory that is the perfect theory, but if I can't prove it, I don't care.

   25. LFLex Fridman1:18:39

       If we were to think, this is going back to the Great Courses on the evidence for modern physics-

   26. DLDon Lincoln1:18:44

       Mm-hmm

   27. LFLex Fridman1:18:44

       ... we're talking about energy levels and tiny particles to the degree where the kind of prediction we would be making is not accelerator-type predictions. So it's probably going to be impossible to build an accelerator that detects something like a string.So you have to make predictions about macro scale behaviors

   28. DLDon Lincoln1:19:13

       That's another alternative

   29. LFLex Fridman1:19:15

       It's a different kind of prediction

   30. DLDon Lincoln1:19:17

       Sure
8. 1:42:17 – 1:49:41

   Physics of empty space

   1. LFLex Fridman1:42:17

      Speaking of which, since we brought up antimatter, we'll have to talk about it. Uh, you've talked about it in several of your lectures from different angles, including, uh, the dark energy crisis and including, uh, empty space and vacuum and so on. So let's look at the empty space angle. So, uh, you know, it turns out that empty space is not empty.

   2. DLDon Lincoln1:42:40

      It's true.

   3. LFLex Fridman1:42:41

      [laughs]

   4. DLDon Lincoln1:42:41

      Which is kind of bizarre.

   5. LFLex Fridman1:42:42

      Can you, can you speak about what do we know about what makes up empty space?

   6. DLDon Lincoln1:42:47

      That's a hard, hard question because we don't know what space is. But let's start out.

   7. LFLex Fridman1:42:51

      [laughs] Yeah.

   8. DLDon Lincoln1:42:52

      Let's just start out with something simple. We'll assume that space is not quantized, okay? Now, it probably is. I don't know. But, you know, we gotta start with somewhere. So let's start out with sort of the space of calculus, the space that you can divide forever. The modern version of quantum mechanics is called quantum field theory, and it postulates that, A, space exists. Then it postulates that within space there exist fields for every known subatomic particle. So there is a photon field, there's an electron field, there's an up quark field, there's a down quark field, there's, uh, all the fields.And those fields can vibrate. And when they vibrate, those are the subatomic particles. So an electron field vibrating in a characteristic way is an electron. Now, it's also possible for the electron field to vibrate not in the characteristic way, but in a way that's still vibrating, but it's not an exact electron. So this is what we call virtual particles. Now, virtual particles, there are lots of ways to talk about them, and the way I'm talking about now is the most correct and the most sophisticated way that we can talk about them. I will talk about them briefly in a m- in a simpler way to help. But right now, that's the important thing is that there are these fields, specific vibrations are the known particles. Vibrations that are a little different are, are these virtual particles. They're particles that don't truly exist. And so that is what we think space is. There is all of these s- these, these fields, they're all vibrating a little. If you insert the right amount of energy, you can get it to vibrate in the characteristic way and make that subatomic particle. But even when you don't, there is, um, the particles, I mean, the fields are there, and they are vibrating. So those vibrating vibrations are what we call virtual particles. Now, your viewers may have heard of virtual particles in other ways, in which case it says that em- space is just empty, and what happens is matter and antimatter particles briefly appear for a very short period of time before they coalesce back again and disappear and, and re-emerge back into the field. And so that-- these are both correct. So what happens is, is that's what quantum field theory says, is it says that these ripples are hearing or these particles are appearing and disappearing. And so that just sounds nuts. You look at empty space, you're not seeing anything happening. But they're happening fast enough that they can't be seen, but they do have consequences. And there are two experimental measurements that I can think of that validate that this thing that sounds crazy is really happening, and one is called the Casimir effect. So in the Casimir effect, you take two metal plates that, parallel plates, and you put them near one another, very, very close. Now, if this is the case, if, if these virtual particles exist, then in between the plates, these particles appearing and disappearing, and outside the plates, the particles are disappear- appearing and disappearing. However, because these plates are close to one another, this puts a constraint on the wavelength of the particles that can occur between the two plates because they, the particles cannot extend outside the plates. So the short wavelength particles can exist inside the, between the plates, but the longer ones cannot. However, outside the plates, there is no constraint, so short wavelength and long wavelength particles can exist there. And the net effect is there are more particle, virtual particles outside and less particles inside, and therefore you have a net pressure which would then push those two plates together. That is a prediction we've been talking about, and guess what? It happens. Those plates push together. So that is a validation for the existence of these particles in empty space. Now, there is another measurement, and this changes the magnetic properties of particles like the electron, the mu- muon and, and so forth. And so this was, uh, discovered in 1948. So if you take old school standard quantum mechanics, um, you know the spin of an electron, you know its charge, you can calculate its magnetic moment, and it comes out to a number. If you do the measurement, what you find is the measurement disagrees with the quantum mechanics, the 1930s quantum mechanical prediction by 0.1%, and that was measured in 1948. And people went, "Huh?" So this happened at Shelter Island Conference in New York, and on the way home, someone who saw the, this measurement thought about it, and they invented what we now call quantum electrodynamics. So old quantum mechanics quantizes matter. The second quantization quantizes both matter and the fields, in this case quantized the electric fields. And so in this quantized, um, field, it predicts that surrounding a bare, say, electron, which is spinning and has a, has a charge, there is this, this bath of particles, virtual particles appearing and disappearing all around it. And the ensemble of all of those particles appearing and disappearing will alter the magnetic properties, uh, that you can measure for the subatomic particle, and it changes it by 0.1%. And we have measured this, and we have not measured this imprecisely. We have measured the magnetic properties of both the electron and the muon to 12, count them, 12 significant figures, and the theory and the data agree number for number for 10 places. And then once you get out to the very end where both the theory and the data have some imprecision, they then disagree. And so maybe there's some interesting stuff going on there. But 10 figures, it's just staggering.

   9. LFLex Fridman1:49:31

      So virtual particles refer to matter and antimatterParticles coming to life

   10. DLDon Lincoln1:49:37

       Correct

   11. LFLex Fridman1:49:38

       Can we just talk about the, the antimatter part of, of that?

9. 1:49:41 – 2:10:31

   Antimatter

   1. LFLex Fridman1:49:41

      So starting with Paul Dirac, one of the most legendary examples of math leading to physics. So the math suggesting that, uh, so something like an an- antimatter should exist, and Paul Dirac taking it seriously, and then eventually showing that it does exist. So what evidence do we have for antimatter?

   2. DLDon Lincoln1:50:02

      So antimatter was predicted in 1928. Paul Dirac was trying to merge quantum mechanics and relativity because the original Schrödinger equation did not, was not relativistic. And in doing so, he basically, the equations were complex, but in the end it came down to something like equation squared equals one. You take the square root of both sides, you get equation equals plus one or minus one. Plus one was the electron, minus one was something. He didn't know what it was. Um, there was some conversation for a while, thought maybe it might be the proton, but that didn't seem to work out. And so he insisted that his equations were right and that there was an antimatter, he didn't call it an antimatter, but a positively charged, uh, sibling of the electron, what we now call the positron, the antimatter electron. So it was predicted. It was discovered in 1932 by Carl Anderson and his student, uh, Seth Neddermeyer. They saw an antimatter electron, and that was pretty cool. So that right there, they knew it was real. Antimatter was predicted, it was observed, that's that. In 1956, the antimatter proton was created, and that required a large particle accelerator, high enough energy, um, to, to, to make it, and that was done at Berkeley. And a year later, the antimatter neutron was discovered. So at this point, and now m- jumping ahead to now, we can make, using, uh, the energy by smashing particles together, we can make antimatter protons, we can make antimatter electrons. We have gone so far to make antimatter helium nuclei. So we have made two antiprotons and two antineutrons, combined them together to make an antimatter helium nuclei. This has been done, been observed, no question. At CERN, they have gone so far as to make antimatter hydrogen. They take a beam off one of their lower energy accelerators. They make antimatter protons. They collect them, they slow them down, they cool them to almost absolute zero. They take, um, uh, sodium 22, which makes antimatter electrons. They slow them down, they bring them together, they coalesce them, and they make literal antimatter hydrogen atoms with an antimatter proton surrounded by an antimatter electron. And they have done incredible measurements. They have agitated the atoms and caused it to emit light. They have looked at the light that comes out of antimatter atoms. And the question is, is does the light coming out of antimatter hydrogen atoms have exactly the same spectral characteristics as ordinary hydrogen, which we predict that it does? And the answer is it does. So the tests have been staggering. We now know a great deal about antimatter hydrogen. Recently, recently like 2023, I believe it was, one of the experiments called Alpha at CERN made antimatter hydrogen, put it in a bottle, and released it and watched which way it would go. Did it fall up or did it fall down? Because, um, while it kind of makes sense maybe to think that maybe antimatter falls up in the same way that we have Coulomb's Law, you've got electric charges and they might attract or repel. Um, however, there was lots of ample theoretical reasons to believe that antimatter also would fall down. So they did this fantastic measurement, and they first they put in hydrogen, and they calculated that some-- if they did this, something like 80% of the hydrogen atoms would fall through the bottom of the bottle, and 20% would go through the top just because, um, gravity is very weak and the atoms will escape wherever they do, but there will be a bias pulling hydrogen atoms down. So they did the exactly the same thing, and what did they find? They find that antimatter falls down. Now, they do not have a good enough measurement at this time to say that the gravity that antimatter experiences is 100% that of matter. What they have measured is that antimatter fell down with a 75% the strength of regular matter, but there were big uncertainties. There was plus or minus 0.13 due to the experiment, which was good but imperfect, and plus or minus 0.16 due to their, um, their theoretical model. So it's like 0.75 plus or minus something like 0.29. And that means there's a good chance it's between 0.5 and one-

   3. LFLex Fridman1:54:57

      Mm-hmm

   4. DLDon Lincoln1:54:57

      ... which means it's consistent with one. So they are improving their measurements.

   5. LFLex Fridman1:55:02

      Well, if I can, I would love to take a bit of a tangent on that topic 'cause I, I went down a rabbit hole watching some of your vi- uh, videos on antimatter, and I mean, Fermilab was the hub for the production of antimatter for quite a while.

   6. DLDon Lincoln1:55:17

      It was.

   7. LFLex Fridman1:55:18

      I saw that NASA said that the global estimate for the current rate of production of antimatter is one nanogram per year. Can you speak to how hard was it to make antimatter? And also, you did mention in a video that, you know, if matter and antimatter meet, they produce a lot of energy.

   8. DLDon Lincoln1:55:37

      Mm-hmm

   9. LFLex Fridman1:55:38

      I think 20 grams of antimatter is equivalent to a one-megaton nuclear warhead in terms of explosive energy. Yeah, so all of those questions together. So how hard is it to produce antimatter?

   10. DLDon Lincoln1:55:52

       It's freaking hard [laughs] . Okay. All right, so here's the deal. So at the time, uh, until 2011, Fermilab was the most powerful antiproton production facility on the planet. Every 2.3 seconds, we would smash 10 to the 13 protons into a target, and we would get out 10 to the 8th antiprotons. So basically, in order to get a single antiproton, we needed to smash 100,000 protons into material. So every 2.3 seconds, we would get of order 10 to the 8th antiprotons, and what we would do is we would collect them over the course of 12 hours or so, and we would get, in the end, we would have to collect them and cool them down and so forth, of order 10 to the 12th antiprotons every 12 to 24 hours. So 10 to the 12th sounds like a lot. It really does. That is a trillion. But you need to remember that a gram of antimatter is 10 to the 23 antiprotons. So that means over the course of a day, we were able to create something like 100 billionth of a gram, and so if we did that for a year, then that would be about a nanogram. So about a nanogram a year, give or take. That's, that's a reasonable estimate. So a nanogram, one billionth of a gram, so that means w- at that rate, with that facility, it would take a billion years running with very little downtime to make a single gram of antimatter. If you combine one gram of antimatter and one gram of matter together, the energy release is equivalent to the combined Hiroshima and Nagasaki explosions. So that tells you if you wanted a, a megaton, you need about 25 times more, so you would have to run for 25 billion years to get a megaton of explosive power.

   11. LFLex Fridman1:58:00

       Let me, uh, lay it all out, because I think it's pretty interesting actually. This is a NASA estimate of how much it costs to produce antimatter. So looking at all the, the, the cost of the accelerator, all, everything combined together, to do enough for a one-megaton antimatter bomb, if such a thing, uh, would be even possible, on the order of 25 grams, like we mentioned-

   12. DLDon Lincoln1:58:24

       Mm-hmm

   13. LFLex Fridman1:58:24

       ... will cost about, based on the NASA estimate, uh, $1.5 quadrillion. By the way, uh, NASA wasn't talking about a bomb. It's just me adding.

   14. DLDon Lincoln1:58:34

       [laughs]

   15. LFLex Fridman1:58:34

       NASA was talking about the estimate, the cost of 62 to $63 trillion per gram of antihydrogen, actually is what they're referring to. Uh, so compared, I was looking at estimates, the current best estimate is how much it takes to produce a one-megaton nuclear warhead. Everything combined is about 10 to $50 million in the United States. So you're talking about difference in terms of a weapon with equal power, $50 million versus $1.5 quadrillion. To me, what's interesting, weapons is just one, uh, indication of this. One other possibility, and NASA also writes about this, is the use of antimatter in propulsion systems.

   16. DLDon Lincoln1:59:19

       Right.

   17. LFLex Fridman1:59:20

       Uh, just like you can use, uh, nuclear fission and maybe even nuclear fusion down the line. In, uh, propulsion systems, I saw that one gram can help get us to Alpha Centauri star system if we can get to 0.2 times the speed of light in 20 years, uh, meaning it would take us 20 years to get to Alpha Centauri. Is any of this a possible future, the use of antimatter for generation of energy? Because we should mention that it's extremely compact. It has the obvious downsides that it's extremely costly to produce. We don't know how to do that kind of scale.

   18. DLDon Lincoln1:59:58

       Right.

   19. LFLex Fridman1:59:59

       The upside is it's compact.

   20. DLDon Lincoln2:00:01

       It's very powerful. So the short answer is it is not a physics problem, it's an engineering problem, so I have people for that [both laughing] .

   21. LFLex Fridman2:00:09

       Right. Yeah.

   22. DLDon Lincoln2:00:10

       Um, okay, but no, no.

   23. LFLex Fridman2:00:12

       Yeah.

   24. DLDon Lincoln2:00:12

       Um, the, the truth is that antimatter, if you are able to, uh, assemble it and store it, sure, it would be able to take that antimatter, heat up matter, and shoot it out the back of a rocket, and it would, you know, do what rockets do, and it would make us go quick, and that would be fine.

   25. LFLex Fridman2:00:31

       And we should mention the thing that you just mentioned is, is correct, one of the hugest challenges is the containment-

   26. DLDon Lincoln2:00:37

       Oh, 100%, yeah

   27. LFLex Fridman2:00:38

       ... because antimatter, when it comes in contact with matter-

   28. DLDon Lincoln2:00:42

       Right

   29. LFLex Fridman2:00:42

       ... uh, is a, is a problem.

   30. DLDon Lincoln2:00:43

       Right. So if you were unable to, uh, to contain your trip to Alpha Centauri for even a millionth of a second, boom, that would not be good.
10. 2:10:31 – 2:14:20

    Dark energy

    1. LFLex Fridman2:10:31

       Okay. So, uh, can we pull at that thread a little further? Let's talk about our intuition of what is, uh, dark energy as it connects to empty space and everything we've been talking about. Uh, what's, what's the cleanest definition of dark energy?

    2. DLDon Lincoln2:10:46

       So dark energy is either energy of space or energy in space. The most common statement is the energy of space, and it is essentially a repulsive form of gravity, and we believe this is real, and the reason we believe this is real is from observation. This is one of those things where we talked about a while ago where I said that, you know, you can think about things up this theoretical stuff and try to come up with a measurement, or you can make measurements and see where they disagree with predictions and lead that in a direction. So back in the late 1990s, some astronomers were looking at the expansion rate of the universe. So the, the Big Bang occurred, the universe is expanding, the universe is full of matter, matter attracts, so the gravity due to the matter of the universe should slow the expansion of the universe, and the only question was h-how much. There were three possibilities. The possibilities were there was so much gravitational force that the expansion of the universe would slow, stop, and be pulled back together in a big crunch. Number two was that the universe would continue expanding, slowing down, but never really stopping. And then the third possibility was the exact critical case, where expansion would slow forever and approach zero only at infinity, never quite stopping or reversing. So those were the possibilities, door number one, two, or three. So they did the measurement, and what did they found? It was door number four. The universe was not only expanding, but the expansion was speeding up, and the only way that could happen, given that gravity slows it down, is there was a repulsive force, and the name we give to that repulsive force is dark energy. This is something that Einstein postulated early on in his, um, his development of, of general relativity, but then be-because at the time, he knew that his theory predicted that the universe would collapse, um, but he believed the universe was eternal and unchanging, and so he needed something to counterbalance the, uh, that, uh, collapse, and so he invented dark energy. He didn't call it that, called it the cosmological constant. Um, but then a few years later, Edwin Hubble discovered that the universe was indeed expanding, and so since the universe was no longer static, Einstein said, [chuckles] "No need for cosmological constant," took it back out.

    3. LFLex Fridman2:13:23

       Mm-hmm.

    4. DLDon Lincoln2:13:23

       Thought it was a, a dumb idea that he put it in and was embarrassed. Um, however, in 1998, it became clear that his original idea that there should be some sort of repulsive form of gravity was real, and it's put back in the theory.

    5. LFLex Fridman2:13:37

       Mm-hmm.

    6. DLDon Lincoln2:13:38

       And so that's what it is. We are pretty confident at this point that the expansion of the universe is speeding up, and the thing driving it is dark energy. Now, what is dark energy? I don't know. Um, as I said, the most common thought is that it is the energy of space itself. But-It is at least conceivable that there is a field in space where space exists-

    7. LFLex Fridman2:14:04

       Mm-hmm

    8. DLDon Lincoln2:14:05

       ... and that field is pushing space apart. That's another conceivability that I'm not sure that we have the, the instrumentation to distinguish, but that's not what normally people think. People think it is literally a property of space.

    9. LFLex Fridman2:14:19

       But,

11. 2:14:20 – 2:42:56

    Dark matter

    1. LFLex Fridman2:14:20

       but there is the [laughs] what, what you call the worst prediction in physics, which is a nice-

    2. DLDon Lincoln2:14:26

       Oh, yeah, that's another one

    3. LFLex Fridman2:14:27

       ... a nice little insight about the complicated n-nature of dark energy. So the observations, as you describe, say that empty space has a tiny energy density that, to accelerates expansion of the universe. But quantum field theory's prediction for what vacuum energy should be when coupled with gravity is much larger.

    4. DLDon Lincoln2:14:51

       Mm-hmm.

    5. LFLex Fridman2:14:52

       Uh, so this is what makes for the, uh, quote, you have a video on this worst prediction in physics. [laughs]

    6. DLDon Lincoln2:14:58

       It is.

    7. LFLex Fridman2:14:58

       Can you, can you explain this crisis?

    8. DLDon Lincoln2:15:00

       Well, the, the-- there's a measurement, and you can measure how fast the universe is expanding, and from that you get a measurement f-of dark energy. However, if you then say, well, suppose the dark energy is due to fields in space. So that's quantum field theory. Hey, I know a lot about quantum field theory.

    9. LFLex Fridman2:15:20

       Mm-hmm.

    10. DLDon Lincoln2:15:21

        And so we can take the quantum field theory, and we can calculate what the density of energy is due to quantum field theory. And basically what you do is you take within a volume the, uh, all of the wavelengths, the, the longer wavelengths, the shorter wavelengths, the shorter wave-- shorter and shorter, and you can add them all up. And each wavelength adds a certain amount of energy, and if you add that all up, then you get a number, and that number is the rather embarrassing ten to the one hundred and twenty power times, that's a one with a hundred and twenty zeros after it, bigger than the measurement of dark energy.

    11. LFLex Fridman2:16:07

        Yeah.

    12. DLDon Lincoln2:16:08

        So you go, "Yuck, that is not fun at all."

    13. LFLex Fridman2:16:13

        Mm-hmm.

    14. DLDon Lincoln2:16:13

        And that is because the equation comes to the highest energy or the smallest wavelength particle that you can imagine to the fourth power, since anything to the fourth power is a big deal. So that's where you get that awful number. Now, if it turns out that there is some new physics that's just about at the energy scale we can measure using our biggest particle accelerators. Remember I told you that that was a factor, the maximum energy scale, Planck scale, is ten to the fifteen times bigger than what we can measure now. So let's say that we don't have to calculate up to the Planck scale because something happens, something changes at the energy that we know right now. Well, then that means we don't have to integrate to Planck scale, we integrate to ten to the fifteenth less than the Planck scale, and this thing is to the fourth power, so ten to the fifteenth to the fourth power is sixty. So now even if we say, you know, Don, he's brilliant, he's gonna find something at the LHC tomorrow, it's gonna solve all this problem, now we've solved it, it's much better. It's only different by ten to the sixty power, [laughs] which is still pretty bleeding big. So the short answer is there is very clearly something going on, something wrong, very badly wrong in the quantum field theory. You know, we have to have-- maybe there's another field that balances out the energy, that cancels it down. And even that, you know, that, that's not so, so outrageous. You know, you could imagine that there's another, you know, like we have matter and antimatter, they balance pretty well. Okay, maybe there's something going on, you could cancel that out, that'd be perfect. But canceling something to zero is easy 'cause, you know, plus one and minus one, zero. Plus two, minus two, zero. But we still have dark energy. Dark energy is a little bit, so if it cancels, it doesn't cancel exactly 'cause it left over that little bit of dark energy. So that is its own curiosity. Perfect cancellation, pretty easy. Theorists do that, you know, eight times before breakfast. Imperfect cancellation, much harder.

    15. LFLex Fridman2:18:27

        Just to elaborate that a little bit, what, what do you think solving, in quotes, solving dark energy would look like?

    16. DLDon Lincoln2:18:33

        Well, you could-- What you would do is you would hypothesize that there existed some other field that had the, the, the reverse, uh, effect of existing quantum fields.

    17. LFLex Fridman2:18:44

        But not to zero.

    18. DLDon Lincoln2:18:45

        But not to zero. So but if you had it to go to zero, you know, uh, sure, maybe there's a field that, that exists at really high energies that we haven't seen yet. I don't know, but it canceled things out, and we're cool.

    19. LFLex Fridman2:18:58

        How would we then demonstrate the existence of that field?

    20. DLDon Lincoln2:19:00

        Uh, well, that would depend on the, the prediction.

    21. LFLex Fridman2:19:03

        How do you even come up with a f- new field?

    22. DLDon Lincoln2:19:05

        Like all theorists do. Well, let's add something to my equation and see what happens. I mean, and, and that's okay. I mean, I, I-

    23. LFLex Fridman2:19:12

        Yeah

    24. DLDon Lincoln2:19:12

        ... I'm being glib about that, but that is precisely what you do. You say, what change-- We, we have this thing that works quite beautifully, except it fails here. What is the addition that we need to make that changes very little in the s- realm that we measured and yet fixes this hard thing?

    25. LFLex Fridman2:19:31

        Mm-hmm.

    26. DLDon Lincoln2:19:31

        And so you literally just go, da, da, da, okay, what do I need? Plus six or something. And as long as it makes no changes where it would hurt our measurements and fixes the big thing, then that is at least a candidate theory. Now, that doesn't mean it's right, but it at least gives you an understanding of what the right answer should look like.

    27. LFLex Fridman2:19:58

        Mm-hmm.

    28. DLDon Lincoln2:19:58

        And so that's the first step, is what should the real answer look like, or what is a possible real answer? And then once you kinda know that, then other people can look and say, "Well, let me think about a theory that kind of has the required propertiesTo do what we need it to do. So it's, it's a multi-step process, but the first step is how do we tame this problem without coming up with really terrible predictions that we've already ruled out.

    29. LFLex Fridman2:20:30

        Hmm.

    30. DLDon Lincoln2:20:31

        And, and so that's what you do. And, and, you know, that, that is literally a, a, a sensible, viable, theoretical thing, you know, 'cause you have to explore cool ideas.
12. 2:42:56 – 2:53:31

    Future of physics

    1. LFLex Fridman2:42:56

       [sighs] What a grand mystery. We've covered so many of them. I could talk to you for a thousand more hours, Don. Let me, if I can, uh, ask you about a little bit more of a, uh, on the personal side, um, you have a really inspiring life story. Your folks didn't, uh, go to college. Can you just tell me about your childhood and where you found the love for physics and science, and maybe how you found your journey to, to, to become a physicist, given the, the context of where you came from?

    2. DLDon Lincoln2:43:31

       Well, uh, [sighs] you know, I grew up a poor kid in the boondocks, great parents, but not ones that could guide me terribly academically, but very, uh, very nurturing. You know, my mom would laugh that she could stop helping me math after like sixth or seventh grade, you know? Um, but they were supportive and there were a couple of things that-- a couple, three things I think that folded into it. One is I was a voracious reader as a kid. I loved science fiction. I would read a book a day. It drove my mother nuts 'cause she would try to be nice. She'd buy me a book and I'd say, "Thank you," and the next day it'd be done. You know, it just drove her completely nuts. But anyways, but science fiction is good for fostering imagination, and so that's precisely what it did. In addition, um, and this is where the more serious science came along, there were lovelyScience communicators that were popular in the 1970s, Isaac Asimov, Carl Sagan, a guy by the name of George Gamow, they wrote books about science aimed at a layperson. You know, I was a kid. I surely couldn't read a, a textbook and understand it, but I could read and, and, you know, get a, a hint of what science was. And on top of that, you know, I was, as most scientist-- people who became scientists, irrepressibly curious about everything. Um, and I had sort of a quasi-philosophical mind. I mean, I was interested in things that, questions that have in the past been theological and then philosophical and now are more scientific, questions about how did the universe come into existence? Um, why is the universe the way it is? Why are the laws of the universe what we f- see them to be? How will the universe-- Was it created? How will it be destroyed? These are, you know, big questions that have bothered humanity for, well, thousands of years. And so, you know, I did. You, you said I had, uh, um, you know, philosophy and religion minors in college, and I did 'cause I was curious about that. Um, I was hoping that learning that history might help me understand these questions. Um, and it was in college where I came to realize that the answers that I was searching for were not to be found in those directions, but I still learned about how those questions have been asked in the past. Um, and so I became a, a scientist, and the only question was, was I going to be a, a cosmologist/astrophysicist-

    3. LFLex Fridman2:46:09

       Mm-hmm

    4. DLDon Lincoln2:46:10

       ... or a particle physicist? And when I m- had to make that decision, it was the mid-'80s, and at the time, there were a lot fewer cosmology measurements. There was an awful lot of thinking about the universe and not enough measuring, whereas with, uh, particle physics, by God, you could do experiments. And so the, what attracted me was the ability to actually get an answer and not just mull over what an answer might be. And so I became a particle physicist. Um, it was difficult without having, you know, uh, family mentors or anything like that, but, but, you know, I managed. And that actually is why, well, I'm here and why I've spent a fair bit of my time writing books and so forth because I figure that there has to be some other kid out there in Iowa or Kansas, Montana, somewhere out in some little town without a lot of access to the kinds of thing that people, you know, who have highly educated parents do. And I'm hoping that, you know, some of them will have read some of the things I've written and will find their own path forward because I found it very rewarding over the years. And, um, you know, I've been doing this long enough that I'm, I'm sure this is true. I've had kids come up to me at the lab and say, "Hey, I'm a summer intern because I saw your video or read your book," or, you know, whatever. Um, so I know that at least I've made a small impact. I mean, always would like to do more and, you know, I appreciate the, uh, opportunity that your, uh, audience affords me, um, 'cause I, I think it's important to talk about these things. These are really cool, fascinating questions. They are unanswered, and they are just waiting for youngsters to come and spend some time thinking about them 'cause one of your viewers might be one of the people who answer these questions that have stymied very smart people for decades.

    5. LFLex Fridman2:48:18

       And we sh- we should also say that you're a legit scientist. So w- we'll mention Sean Carroll, who's a legit scientist, legit physicist, but is also a good science communicator. Anyway, I did wanna mention, I don't know if this is true, but I, I kind of heard you talk about this, that when you first showed up to Fermilab, you were, like, working crazy hours, working extremely hard-

    6. DLDon Lincoln2:48:41

       Mm-hmm

    7. LFLex Fridman2:48:41

       ... 8, 8 AM to midnight.

    8. DLDon Lincoln2:48:43

       I did.

    9. LFLex Fridman2:48:44

       Uh, first of all, I love that. [chuckles] Uh, c- can you speak to what drove you and maybe the value of hard work in those contexts in your, in the early career when you discover a thing you're passionate about?

    10. DLDon Lincoln2:49:00

        Well, yeah. I mean, obviously being smart, you know, if you're Einstein, then maybe you can slack, I guess, although even he didn't do that. But I'm not Einstein. But the fact is, when I was young and I was unencumbered, no, no family, no kids or something, I couldn't imagine anything I wanted to do more. I mean, some people, they wanna go out to the club. They wanna, I don't know, play soccer or something. But I wanted to make measurements, and I wanted to understand and, and, and learn, and that was fantastic. And so as a graduate student, and this isn't for everybody, but I worked outrageously. I would, from Monday through Saturday, I would be at the lab voluntarily because I wanted to be from 8 AM to midnight, and on Sunday, I would work from 8 until about 5, and that's because from 5 to midnight, I had to wash clothes and buy groceries and things like that. And I loved it, you know. Uh, and I still love it. I can't do that anymore, um, but, but that's simply because I have other obligations. But had I been rich, I would've done the same thing.

    11. LFLex Fridman2:50:09

        Mm-hmm.

    12. DLDon Lincoln2:50:09

        You know, it's, it's something I truly, truly loved. And the-- I mean, there is absolutely nothing more fascinating to me than having a hard problem and figuring it out. And that, you know, that work ethic-- Well, there's a couple of things that separate smart people from no-kidding scientists 'cause all scientists are smart, but the thing that, that separates, that, that, that many scientists have is, A, a drive and, and a real grit. The, um-- For me and for so many scientists that I know-Trying to measure something and having it not work just kind of ticks me off, and I am not going to let the universe in my lab or whatever beat me. And, you know, some people they, you know, if the thing breaks, it's like, "Oh, man, that didn't work." And a lot of people, "Well, I'm gonna go home. I'm fed up." Nah, it would just kind of make me mad, and I'd put more effort into it.

    13. LFLex Fridman2:51:11

        [laughs]

    14. DLDon Lincoln2:51:11

        And, you know, not every-- I mean, okay, I was crazy. I worked long hours. But, but I think-

    15. LFLex Fridman2:51:16

        Yeah

    16. DLDon Lincoln2:51:17

        ... the people who are really good at this will do maybe not that much, you know. Some people have to have a better life than that. But, but a lot because it, it's just you can't imagine not knowing the answer.

    17. LFLex Fridman2:51:29

        Mm-hmm.

    18. DLDon Lincoln2:51:30

        And that if-- when, when you see that a-as an older guy, you don't-- maybe not to that degree, but when you see that kind of drive, that, that, that intensity of trying to get the answers, you know that person's a winner. And, and so if, you know, some student out there, if it doesn't, you know, bring you joy, as, uh, uh, what's her name? The Japanese girl says, "If it doesn't bring you joy, then it might not be for you." And then you could be a person who reads about it and, you know, is involved. But if you wanna be a real scientist, it, it has to be just part of what you are here.

    19. LFLex Fridman2:52:06

        And by the way, it is a hard life, but it is also s- a very fulfilling one. So working hard towards the thing you love is a really fulfilling way to, to be.

    20. DLDon Lincoln2:52:19

        I think that's true for an artist or something. You know, anybody, a, a musician, you know. Musician, they just keep practicing because it is who they are.

    21. LFLex Fridman2:52:27

        Mm-hmm. Well, I'm glad there's people like you at a place I admire, like Fermilab, uh, one of the many places in the United States and the world that, uh, is carrying the beacon of great science and great engineering forward. Uh, Don, thank you so much for everything you do, for all the teaching you do, uh, online, for all the incredible physics work that you do at Fermilab, and, uh, thank you so much for talking today.

    22. DLDon Lincoln2:52:59

        Thank you for having me.

    23. LFLex Fridman2:53:01

        Thanks for listening to this conversation with Don Lincoln. To support this podcast, please check out our sponsors in the description, where you can also find links to contact me, ask questions, give feedback, and so on. And now let me leave you some words from Marie Curie, a two-time Nobel Prize winner, first in physics, second in chemistry: "Nothing in life is to be feared. It is only to be understood." Thank you for listening. I hope to see you next time.

Episode duration: 2:53:42