YouSaid · the spoken record

Don Lincoln

lines on the record: 207
first: 2026-05-29
most recent: 2026-05-29
sittings or episodes: 1
sources: podcast

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“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. 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. And that field is pushing space apart. That's another conceivability that I'm not sure that we have the instrumentation to distinguish, but that's not what normally people think. People think it is literally a property of space.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“His development of general relativity, but then because at the time, he knew that his theory predicted that the universe would collapse, but he believed the universe was eternal and not unchanging. And so he needed something to counterbalance that collapse. And so he invented dark energy. He didn't call it that. call it the cosmological constant. 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, no need for cosmological constant, took it back out. Thought it was a dumb idea that he put it in and was embarrassed. 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.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“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 find? 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”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“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 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, 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.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“And if the neutrinos oscillate at slightly different rates, then that, along with several other highly improbable things, can tie together and might explain why there is more matter in the universe. So if I was going to bet the farm, I'll bet that they oscillate at the same rate, but I don't know and you don't know till you do the measurement. So that's what we're doing. There are some other experiments trying to measure it right now. So there's a big race between the Fermilab group and another group in Japan to see who gets there first and make this measurement. And we will find out if it turns out, though, that there is a difference in this oscillation rate between matter and antimatter, it will be a huge clue in this very, very difficult puzzle. I wish I could tell you I knew what the answer is, but literally nobody knows. I mean, and that's the thing of being a researcher.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Is called neutrino oscillation. We've known it's been true since 1998. And what we are studying is we're going to make a beam of neutrinos and another beam of antimatter neutrinos. And we're going to study the oscillation behavior of the two of them. And it is possible. It is unlikely, but it is possible that the two of them will oscillate at slightly different rates.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Slight difference between matter and antimatter, but it's not enough. It doesn't explain that. We're not sure. So at Fermilab, we have this idea which kind of turns things on its head, and it's not baryogenesis, it's leptogenesis. So leptons are the electrons. And because Fermi Lab is currently the world's most powerful neutrino accelerator and neutrinos are leptons, there is this idea. Now, leptogenesis is incredibly complicated, but the idea is that it is possible, we know that neutrinos actually change their identity. There are three different types of neutrinos, like, I don't know, cats and jaguars and tigers. And if you have a beam of just cats, if you go along a little while, you find there's cats and jaguars. And then tigers, and then they'll be back to all cats again. And so this oscillation...”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Another possibility is there are various numbers of theories all under the word baryogenesis. Baryo coming from word baryon, which basically means protons in Genesis, meaning the creation of. And we'd say that simply because the protons are the heaviest particles. And so baryogenesis is just the creation of matter. And there are just a number of theories in quantum mechanics that say that matter and antimatter can oscillate back and forth into one another. And there is a slight asymmetry in how that happens. And we know that this is true to a degree. We've measured it in the 1960s with a different form of matter, not protons, but a type of ephemeral matter that only exists in particle accelerators. And so we know that there is a”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Tiny asymmetry so that for every billion, billion with a B antimatter particles that existed in the universe, there were a billion and one matter particles. The billions cancelled, annihilated, destroyed each other, and that extra one that's left over is us. And so what physics mechanism made that ever so slight asymmetry is not understood? There are some thoughts. One thought is that, well, it's just how it was when the universe was formed. There was an asymmetry. It was not made by matter and antimatter.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“However, there are some ideas and there's a lot of thinking on it. And in fact, for me, it's doing an experiment right now with neutrinos, trying to better understand what it was that made the matter and antimatter not be the same. Now, we do have a measurement of how much different it should be. And it's kind of neat. We can do this by counting the number of protons in the universe, just looking at galaxies and so forth. And then we can look at the cosmic microwave background, which is sort of the aftermath of the Big Bang, and we can count the number of photons from the cosmic microwave background with a little bit of math. What we can do is we can then say that somehow in the early universe, something made a very, very”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“There's this thing called Baryogenesis. And as you say, so reiterating a little bit what you just said, these are both Einstein things. Einstein says that when you take energy, you make matter and antimatter in equal quantities. And Einstein says after the Big Bang, there was a lot of energy in the universe, which should have made matter antimatter. We only see matter. Where'd the antimatter go? And the answer is we don't know.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“And remember, we're talking concentrating it into volumes the size of a proton. I mean, if you concentrate it to the size of your thumb, well, then it's really the density that matters, the local density. And so when you smash two protons together, all of that's occurring in a tiny, tiny volume. So it's the local density of energy that matters. If you had a lot of energy in a thimble or something. It's probably not dense enough. It really has to be in close proximity for that to happen. And then when it does, It's okay. So if there's another way, we know how to do it to make that density thing with accelerators. If someone has a bright idea on how to make highly dense energy, then yeah, making antimatters a piece of cake. But that's the crux, concentrated energy.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“I mean, we know how to do this. We know you take energy, you make antimatter. You have to contain it. You have to store it. You have to do all the hard things. But I would be shocked if there was some new addition to the theory that made antimatter production easier.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“So the short answer is yes, antimatter as in principle we could make and use as a source of energy. But there are probably far less expensive sources of energy. It depends on what you need to do. If the Voyager probes are still chugging along with plutonium now they're running out of energy at this point, but we could presumably do a somewhat better job if we needed to. So I like the idea of antimatter, but the reality is the danger, not the obvious danger of weapons, but the danger of if you wanted to be in a ship run by antimatter, if it ever got loose, well, you would never know it. That would be that.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Right. So, if you were unable to contain your trip to Alpha Centauri for even a millionth of a second, boom, that would not be good. You know, it reminds me of the Star Trek where Scotty Sing Kipton, you know, the antimetropods are about losing containment. It's going to blow. And that's exactly what would happen.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“If you are able to assemble it and store it, sure, it would be able to take that antimatter, heat up matter, and shoot it at the back of a rocket, and it would do what rockets do. It would make us go quick. And that would be fine.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Very powerful. So the short answer is it is not a physics problem, it's an engineering problem. So I have people for that. Okay, but no, no. The truth is that antimatter”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“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 a reasonable estimate. So a nanogram, one billionth of a gram. So that means 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 megaton, you need about 25 times more. So you would have to run for 25 billion years to get a megaton of explosive power.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“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 ten to the twenty three antiprotons. So that means over the course of a day, we were able to create something like 100 billionth of a gram.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“It's freaking hard. Okay. All right. So here's the deal. So at the time until 2011, Fermilab was the most powerful anti-proton production facility on the planet. Every 2.3 seconds, we would smash 10 to the 13 protons into a target. 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”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Plus or minus 0.16 due to 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 1, which means it's consistent with 1. So they are improving their measurements.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Of the hydrogen atoms would fall through the bottom of the bottle and 20% would go through the top just because 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 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.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“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 twenty twenty three, 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 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. 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%”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“In 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 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, does the light coming out of antimatter hydrogen atoms?”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“And his student, Seth Nedermeyer, they saw an antimatter electron. And that was pretty cool. So 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 to make it, and that was done at Berkeley. And a year later, the antimatter neutron was discovered. So at this point, and now jumping ahead to now, we can make using 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 anti-neutrons combined them together to make”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“So, antimatter was predicted in 1928. Paul Durac was trying to merge quantum mechanics in relativity because the original Schr ⁇ dinger 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. You didn't know what it was. 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 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.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“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.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Quantized the electric fields. And so in this quantized field, it predicts that surrounding a bare, say electron, which is spinning and has a charge, there is 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 that you can measure for the subaton 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.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Discovered in 1948. So if you take old school standard quantum mechanics, 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 the Shelter Island Conference in New York. And on the way home, someone who saw 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,”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Between the two plates because the particles cannot extend outside the plates. So the short wavelength particles can exist inside 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 muon, and so forth. And so this was...”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“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 these virtual particles exist, then in between the plates, these particles appearing and disappearing and outside the plates the particles are 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.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“We think space is. There is all of these fields. They are 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 the particles, I mean, the fields are there and they are vibrating. So those vibrating vibrations are what we called virtual particles. Now your viewers may have heard of virtual particles in other ways, in which case it says that 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 re-emerge back into the field. And so these are both correct. So what happens 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”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“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 simpler way to help. But right now, that's the important thing is that there are these fields, specific vibrations or the known particles, vibrations that are a little different. Are these virtual particles? They're particles that don't truly exist. And so that is what”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“That's a hard, hard question because we don't know what space is. But let's start out 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've got to 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 all the fields.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Gravitational wave astronomers saw the ripples of spacetime. It was one hundred and forty million light years away, which means light would have traveled 140 million years to get here. And the two incidents, light and gravity, both arrived within 1.7 seconds of one another. And that tells you that gravity travels at the speed of light. That was a brilliant, fantastic measurement. Now we thought gravity traveled at the speed of light, but now we have a measurement. We proved it. And damn it, I am impressed.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“There was another brilliant observation recently. Love it. The observation of gravity waves. And it was from two neutron stars orbiting and coalescing. And so they made gravitational waves, fantastic, but they also, because they were not black holes, they were neutron stars, they hit and exploded, gave off a tremendous bright flash of light. And so astronomers saw the flash.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“That old prediction of loop quantum gravity is no longer valid. And so that observation of the uniformity of the speed of light no longer kills the new loop quantum gravity. It would have killed the old one, but it didn't kill the new one.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Had to do with the wavelength of light basically interacting with the structure of space. And so that was an issue with loop quantum gravity. And so if you look at gamma ray bursters, which are super explosions of astronomical events that are a billion light years away or more, and they spit out light in all wavelengths. And if that loop quantum gravity prediction were correct when you saw one of these gamma-ray bursters, you would see the wavelength of one light appearing on Earth at a different time than another wavelength because of the different speeds. And that wasn't the case. They appear at the same time. And so I went on to say, well, this pretty much killed loop quantum gravity, only to get a prickly note from Dr. Ravelli saying, you know, we've disproved that. We've changed the theory. That's no longer true. And now that prediction.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Have a candidate for dragging gravity in. And then, oh my gosh, people got terribly excited because now this theory, which was working in the direction of the other quantum forces, brought in gravity, and now it was a candidate theory for everything. But that's not what loop quantum gravity is. Loop quantum gravity is simply trying to understand the nature of space itself, which is already a fantastic thing. And I talked to Raveli every so often. I write about his theory and I point out some of the issues with the theory, but I'm usually about like two months behind as he and his colleagues are developing and so forth. Because one of the things is originally loop quantum gravity predicted that the speed of light would not be universal. The speed of light would depend on the frequency of the light, so high frequency would travel at one speed and low frequency would travel at a different speed.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Interesting to the theoretical community, string theory was not being developed as a theory of everything. It was being developed as a theory of the strong force. And it was in competition with QCD, which is the currently accepted theory of the strong force. And it turned out that the two groups, the string theory groups and the QCD groups, competed for a while, and string theory basically failed the race and people paid attention to quantum chromodynamics, QCD. But then somebody noticed in string theory that one of the things it predicted was a zero mass spin-to particle. And you can prove that any zero mass spin-to particle is the graviton. And so if you see a theory that has a zero mass spin-2 particle, you are now”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Apply. However, it is possible that at a small enough scale, space is no longer divisible in the same way that you can take a cup of water out of a swimming pool and then a quarter a cup and so forth. But eventually, once you've taken out”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Many of those theories are espoused by passionate people. They have fans. People love them, but they don't do what science needs to do, which is make predictions. Now loop quantum gravity is a little different. That one is better developed. And that one is not a theory of everything. So we should make that clear. Loop quantum gravity is not a theory of everything. It is simply a theory of quantum gravity. Period. It does not aspire to include all of the known forces. It simply tries to take gravity, which is currently intrinsically, it treats space as smooth and continuous for those of your viewers who are mathematically inclined. In Einstein's theory of general relativity, gravity is infinitely divisible. There is no smallest bit. And so essentially the laws of calculus.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Do I want to spend my life working in this direction with a very likely possibility that 30 years from now will be not much farther along than we are now? It's a lot like back in the 1940s when people started thinking about the meaning of quantum mechanics. And I wanted to do that when I was a kid in the 70s. But then when I went to grad school, I realized that people, very smart people, people smarter than me, had been working on that for most of their lives and made no definitive progress. And so you have to decide as a scientist who wants to answer questions, do I really want to take on a question that is so hard that it will not be answered in my lifetime? And I think that's what's happening with a lot of super string theories. People are saying it's really neat. It might be right, but I don't want to devote my life to something that I might not see progress forward in my lifetime.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“Until we can validate this, we can't. Now you ask, is it dead or not? In my opinion, it is very difficult to kill such a theory. I mean, really, truly kill it. Because kill it means make a prediction and it fails. But what can happen and what is happening is people have been working on it since the 70s. So we're talking of order 50 years. People have been working on it and it has not solved the problem. And so I think what's happening is people are looking at that and saying,”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“An extremely large number of possible universes. But if we were able to take those predictions and somehow connect it to a physical measurement, then what we would do is we'd lop off those alternatives, we'd throw them away as saying, well, you know, those are like in equation x plus 5. I can put in any number I want in there. It doesn't matter. But if x plus 5 equals 9, then I've ruled out a whole bunch of numbers except four. And so this is a case of string theory does allow for many predictions. But if we could rule them out by connection to a measurement, then it would no longer do it. We would modify string theory and we would retain the vibrating string concept, which I really, really like. I mean, I really like it.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“I agree to a degree, but I bring it back to my prior objection. It is absolutely true that super string theory in its current manifestation, aside from the extra dimensions, which are at some level small potatoes, it allows for”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“I'm not sure. So that's another option to simply look at many measurements that are very precise and find ones where the outcome and the prediction of established theory disagree. And that is a clue.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“There are two directions. You're talking a top down. Someone comes up with this big idea that's testable, but you also have the other way that science advances, and it's not with a theory that is then tested. It's with the weird. For instance, either in the 1930s with Fritz Zwickier in the 1970s with Vera Rubin, she did a simple thing. She said how fast are galaxies rotating? Because it's an easy thing to calculate. You could literally calculate that with high school physics. And you get an answer, and then you measure it, and it's wrong. And so that's the, wow, huh, I don't know what that is. And that led to the hypothesis of dark matter. Now, dark matter is not a theory of everything, but it's a clue. It's a powerful clue. We should tug at that thread. Maybe our entire theoretical edifice unravels, or maybe it doesn't. Maybe it's just a snag and we can fix what we have now.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“That was a cool idea. I mean, but that's the point you have these lovely, cool, interesting ideas that constantly die. And so, you know, I would love for a new nifty idea to be the idea, but I don't know how to pick it out of the hurricane of wrong ideas.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source
“One that was recently I liked and might still be true was that dark matter, that our simple model of dark matter is that there's a subatomic particle out there that's heavy and it's floating around and it's causing gravity. But someone said, well, you know, maybe there's complex dark matter, which means there's a whole dark sector. So there are dark atoms, and they interact with one another. And that is a nifty idea. And I love it. That was all the rage for a while. And we looked at it, and it may still be true, but the simple ideas have been mostly invalidated because we've tested it and it doesn't work. Same thing. There was a talk about large extra dimensions. The reason that gravity is so much weaker than the other forces was, well, maybe gravity can sneak into more dimensions than the other forces.”
2026-05-29 · Lex Fridman Podcast · #497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln · IDENTIFIED FROM THE TRANSCRIPT · source