What's the problem with the Standard Model?

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Speaker 1: Hey, Daniel, are you guys done with physics yet? Done with physics? I mean we're just getting started. Yeah, But then you build that large hattern collider. Didn't that answer all of your questions? Now there's always more stuff to figure out? Man, What do you mean people paid ten billion dollars for that and now you need more money. That was just like the down payment on the project. What was that a defined print? We missed that. Somehow research is exploration. Man, They're never any guarantees about what we're going to find. But I thought the Higgs Boson completed the standard model. I mean it's called the standard model. Aren't you done? It's the standard model. Now we want to upgrade it to like the super standard model. Sounds like you need to go work for Apple. It sounds like we should work for f t X. Sounds like we paid you ten billion dollars for the wrong model. Can we have a hundred billion please? Hi am more hammered cartoonist and the creator of PhD comics. Hi. I'm Daniel. I'm a particle physicist and a professor at U C Irvine, and I will never be done asking questions about the nature of reality. But what if you get the final answer, wouldn't you be done? Well? The lesson from that book is that you're never done that even if you do get the final answer. The next question is, well, why this answer and not something else? Why do we live in a universe where the answer is forty two and not forty seven? What does it mean anyway? The questions multiply. Maybe the ultimate answer is because that's a non answer. It's an answer, it's not a very satisfying answer, and in the end we're looking for explanations, not nonsense. But welcome to our podcast. Daniel and Jorge Explained the Universe, a production of I Heart Radio, in which we try to satisfy your curiosity about the nature of the universe. Why is the world made up of tiny little particles frothing together to build up our reality? How far down do you have to go before you can really understand the universe at its most basic level? And is there even a most basic level? Or is there an infinite tower of questions all the way from galaxies down to black holes, down to particles, down to strings, and then down to whatever strings are made of. Yeah, it's an incredible universe full of gigantic phenomenon like black holes and galaxies and clusters of galaxies, but also with a lot going on at the microscopic level, with atoms and particles and tiny little quantum lips, and somehow it also needs to be ruled by the same rules. The same rules supplies from the tiniest levels to the most cosmic of all levels. It really is incredible how many layers of zoom we have for the universe. Like we can think about the universe on the scale of super clusters of galaxies, objects that are hundreds of millions of light years across, and they follow gravity. We can make predictions about how they swirl around each other, and then you can sort of adjust your zoom knob and think about planets and stars, and you can adjust your zoom knob again and think about rocks and liquids, and you can do it again, and think about atoms, and you can do it again. You can think about protons. You can do it again and think about corks. And we just don't know how many layers of zoom are there, and we don't actually even know the answer to the question of whether they all follow the same rules. You know, our reductionist approach assumes that there is a basic nature to the universe with a certain set of laws from which everything else emerges. But that's sort of a philosophical assumption. We're not even sure that's true. Do you find yourself, Daniel, reading a scientific paper that you print it out on paper and then you're trying to zoom in with your fingers? Does that work? I do sometimes click on blue links on printed out papers, and I'm frustrated that they don't just like print out the right paper for me. That would be awesome if you could click on a link on a paper and your printer would just print the next paper. But it is pretty amazing that we know so much about the universe, from the neest levels to the largest of all stages the entire universe. And I guess the hypothesis, like you said, it, is that there's one set of rules that somehow rules at all. That's certainly one philosophical approach. We call that reductionism, the idea that the tiny dominates the huge. And it sort of makes sense to us intuitively that things emerge from the smallest bits, But if you dig down into it, there's not really a whole lot of justification for it. I mean, why should the small dominate the large? Why can't rules emerge at the larger levels as well and dominate the small? Wait? Who said the tiny dominate the large? I would say that the particles here on Earth pretty much subject to whatever the Sun wants to do. I think the sort of standard philosophical approach to physics is to imagine that there are basic rules at the smallest scale, and those rules somehow weave themselves together to make our reality. And so in order to understand the basic nature of the universe, we should dig deep into the smallest particles to try to find the smallest of the smallest of the small, and a long way we have made a lot of progress, a lot of encouraging results. We've understood the nature of the periodic table based on how protons and neutrons and electrons fit together to make all of those different atoms. We've even understood how protons and neutrons are built out of smaller pieces. So there are a lot of hints that suggest that we should keep digging down into the nature of reality to understand how the bigger things emerge. It's kind of interesting how physics has some I've covered both ends of the spectrum, but not the stuff in between. Like you start on small with the particles and atoms, but then that's when you're like, ah, that's chemistry, and after that biology, and after that you know, political science. We don't care about that. But then once you get to like the size of the planet of the Solar System, and you're like, Okay, now I'm back. Now I'm interested in this again as a physicist will take over from here until the end of the universe. Yeah, that's right. And it's really fascinating sort of from a sociological point of view, because for a long time, those communities, the astrophysics community and the particle physics community were totally separate. The people who worked on galaxies didn't they spent a whole lot of time talking to the people who build colliders and smashed particles together. Though they were in the same department, they didn't really overlap very much. But more recently those communities have come together because there is a common mystery, for example, the mystery of dark matter. We discovered it through astronomical observations that revealed that there's stuff out there that is not made of our kinds of particles, and now we have particle physicists searching for that dark matter. So now we have a new kind of physicist, astro particle physicists that work both on the biggest things and the tiniest things in the universe. But you're right, skipping everything in between. Yeah, I feel like you guys skip over anything that's messy and complicated. I wonder if that says something about your personalities. I do think that I got into physics to avoid all the complications of chemistry and biology. That's certainly true. We like approximating things as simple objects, dots, spheres, circles whenever we can. Planets, right, Planets are also just circles to you. So sons right, basic kindergarten, She's as long as you stick with that than your physicist. I think kindergarten is probably too advanced. I mean, I wouldn't want a triangle shaped planet or anything. Wouldn't that be interesting though, I'd be like that sounds like chemistry to me. I'll focus on the spears. It sounds like geometry. Forget about it exactly. We do have a pretty interesting view of the universe now, and an interesting model that describes how things work at the tiniest levels and that we are hoping extends to the largest of levels. But we do have a model about the universe, and we've been building it over centuries. Right. Physics builds our concepts of the universe sort of on these levels. Right. We have like the atomic level where we think about the elements, and then we zoom in and we think about the nucleus, and then we zoom in and we think about the quarks. And at the level of the quarks and the electrons. You're right, we have a very nice picture of all those particles, how they interact, what they do. And that model also explains all the experiments that we can do smashing particles together at very high energies and all sorts of other very detailed, exhaustive experiments. The picture we have of those particles we've been putting together for about a hundred years. It's sort of all clicks together very nicely. Now. Yeah, it's a pretty good theory that describes what we can see and it works pretty well. However, we sort of know it's not the final theory or the ultimate theory of the universe. That's right. Physics is never done asking questions. And even if we have a beautiful concept which clicks together and explains experiments, this is will always come up with ways to keep the project going. Conveniently, you'll figure out a way to keep your job going. You think being driven by curiosity, staying up late at night wondering about the nature of the universe is convenient. It's almost like an obsession. And so to the end of program, we'll be asking the question, what's the problem with the standard model? I think I know the answer, Daniel, is it me? Am I the problem? Well, that's one problem, yes, But maybe your main problem is that you call it the wrong thing. I mean, you call it the standard model. Not everyone thinks it's the standard one. But now you're saying it's not standard. Yeah, you'll be amazed to discover that we can't even actually agree about what is the standard model. Some people think the standard model is one thing, other people think it's something else. So it turns out the standard is not actually standard. It sounds like you guys have no standards when it comes to naming things, especially models. It doesn't surprise me that we didn't impress you on this one. But really, maybe the question we are asking here today is what are the problems with the standard model? Right, because there's not just one problem with it, there are many. There are many problems, There are unanswered questions, there are cracks in it, there are missing pieces, there are things we know the standard model cannot describe. All of these things are vital hints and clues laying the path for the next generation of physicists, who we hope will reveal a deeper understanding into the nature of reality. So maybe a better name would have been the model issue or the sort of model, the non standard sort of model. Well, usually were wondering how many people have thought about this question and have wondered what are the missing pieces of the standard model? What's wrong with it? So thank you very much to everybody who answers these questions for this segment of the podcast. We thoroughly enjoy hearing your thoughts and we would love for everybody else to have a chance to participate. If you would like to put your voice on the podcast answering these questions, please write to me two questions at Daniel and Jorge dot com. I will set you up. So think about it for a second. What do you think are the problems with the Standard Model. Here's what people had to say. I feel like we're confident about how gravity works, like on the microscope or macroscopic level, and then we're confident about like quantum mechanics, but we don't know how to relate the two. And that's the problem. As I understand that the Standard Model describes a proton and the nucleus and electrons, and the problem with it is that it describes them as little actual points in space as opposed to excitations of various quantum fields. Uh. Therefore, I remember you saying actually in the podcast that it's actually an incorrect interpretation to imagine these little things as particles or a little discrete points in space. Maybe the problem is that it doesn't have anything for the dark matter and dark energy. But my problem is that standard model has many things to remember and it's too difficult for me. I think the main bron with the Standard Model is that there's no room for gravity, and I think, especially with the Higgs, it kind of almost finalized. It snowork kind of stuck. Well. I think that the problem with the Standard Model might be that it is incomplete. It may not have the particles to describe, for example, quantum gravity, so it can be reconciled with general relativity. Well, I think the problem with the standard model is that a people are unsure about the missing pieces in the pattern, missing holes in the periodic table type deal of the standard model. And people are curious if there is on some sort of emergent or if it's some sort of an emergent phenomena of smaller particles, even smaller than those that we observe in the standard model. All right, a lot of awesome ideas here. There seemed to be a lot wrong with the Standard model. I think this might be the first time we can say that every single answer is correct. Wow, that's amazing. So we're done. It turns out the listeners are answering the questions for themselves. We have trained everybody so well that we have worked ourselves out of a podcast. Sorry, we have reached the singularity. Thank you everybody, it's been great. What sounds like maybe you need some different standards or the standard model, you know, like they have the Gold standard, the Platinum Standard, Green Standard, the tin Can Standard. Well, you know, I do think it's a strange name for a theory, The Standard model it's like calling something modern physics. You know, what we teach as modern physics these days is physics as we knew it about a hundred years ago. So when they started calling it modern physics, they sort of painted themselves into a corner. And that happens every time you give something a name like that. It's like calling the draft of your paper final final, ready to submit. You know, that's not the one you're going to submit. It's going to be ready to submit virgin seven before you actually turn that paper in. So then what do you teach at the graduate level? Postmodern physics, deconstructive is physics, impressionist physics. Yeah, now we have avoided giving an updated name like supermodern physics or actually modern physics. We just teach whatever it is we know. Now, well, I guess there's a classical physics, so you've got to figure out how to distinguish it from that, right, Yeah, Well, we usually think about classical physics and quantum physics, and quantum physics obviously more recent than classical physics. What do you call this podcast physics? Light diet physics? No, this is the juice man. This we are squeezing physics to extract all of the core ideas and understanding. This is like a shot of physics. This is like the frozen concentrate kind of physics. This is like that protein powder man. This will beef you up in your physics knowledge. Your brain might not be great for your kidneys, but it will make your mind strong. All right, Well, let's dig into this, Daniel. I guess first of all, what is the standard model and is it really standard? So the standard model is our description of nature at the deepest level that we have seen so far. You know, we have six quarks, we have six leptons, we have forces that tie them all together. The standard model is what we call our theory of how all of that works. And it really has emerged from a piece of work that started like about a hundred and fifty years ago with Maxwell, as he tied together electricity and magnetism into a unified concept of electromagnetism. That was really like the first step towards having any sort of holistic understanding of various phenomena in physics and like one big idea. Right, But then this sort of this was after Newton, right, Like Newton had an idea of how forces and masses and things interacted and worked. This is more about, like, let's break it down and think about all the different kinds of forces that are out there. Yeah, Newton was thinking about how masses move and the effects of gravity, but there are lots of other phenomena out there that can't be explained by gravity, right, like electricity and magnets and all sorts of other stuff. And Maxwell brought a bunch of things together and put them sort of under one umbrella. He developed sort of the standard model of electromagnetism, and that's sort of like the founding kernel of today's standard model. He explained how forces operate in terms of fields and how a bunch of different forces really were part of one bigger picture, right. And he was looking at specifically at electrical things like you said, and magnetic things, but not gravity. But it's still kind of using Newton's equations to think about like, hey, if I put this magnet in this field, how is it going to move and why does it move? Like that? It's Newtonian in the sense of F equals m A. He was calculating the electric force, for example, on an electron, and you can use F equals m A to deduce how the electron accelerates. So it's part of mechanics in that sense, but really he was digging deeper, was wondering just like, what is the source of these forces? Why are there forces in the universe? And can we explain all of them in terms of a single idea rather than having like a long list of different ones. And is that where the name the standard model came in. The Standard Model as a name didn't really appear until much much later, like a hundred years later. So we have electromagnetism from Maxwell, and then that was turned into a quantum theory when we developed quantum mechanics, and it's sort of fine men and a bunch of other folks that turned electromagnetism into a quantum field theory, which is the more modern version of it. That was about the nineteen fifties ish, and he and some other folks won the Nobel Prize for that. So then we had a quantum version of electromagnetism. But we also have these other forces we had, like the weak force, and Steve Weinberg, who won a Nobel prize, figured out how to bring the weak force together with electromagnetism. And that's the first time people really called this sort of the standard model. And he wrote a paper called a Theory of Leptons, which is what brought the weak force together with electromagnetism. And around then is when people started calling it the standard model. I see, I guess what do you mean by the standard model. It's like, hey, we have all these different ways that particles and things can be pushed in, all these different forces that they seem to experience. Can we put all of these forces into like one umbrella or one you know, equation or theory, and we can? And that's kind of standard because it covers everything. Yeah, although of course the standard model doesn't cover everything yet. Right, even the standard model we have today does not describe everything, as we'll dig into in a minute. So we should think of it as like sort of our current best work in progress description of all the particles that we can't explain so far. But it's sort of like, you know, we're all building a barn together. Let's all work on the same project at least and try to put the whole thing together into one edifice. But it's sort of like how far we've gotten. It's like working draft underscore seven. Now, when you say that you're putting all these different forces under one theory, what does that mean. Does that mean that all these forces are somehow related to each other, they somehow interact with each other, or are they separate. It's just it's just about, you know, putting them under the same grouping. Yeah, that's a really great question. I think there's two ideas there. One is putting the forces in the same mathematical language, like can we describe these things in terms of the same basic concepts? And the basic concept we have for the standard model are these fields that fill space and carry information and momentum around. And that's the basis for why electromagnetism can push on things, and why the weak force can push and pull on things, and also why the wrong nuclear force can. So we have a mathematical sort of formula for how that happens. And the Standard model is cool because it puts all these things sort of in the same mathematical language. For those of you who know some physics and math, it means we can describe everything as a quantum field theory just by specifying its lagrangin, just by saying, here's where the fields are here's how they wiggle, and also here's how they talk to each other. That's sort of like the language we've developed for the standard model. But there's another level to it, which is deeper, which is that sometimes we can see symmetries there. We can say, oh, look this piece of the math over here and that piece of the math over there. If you bring them together, they actually clicked together into something simpler. So that's what we've done, for example, with electromagnetism and the weak force, we've combined them into one mathematical structure we called the electroweak force. So sort of two levels to that. One is just writing it in the same language, and the other is noticing patterns and simplifying things by bringing them together. M Because I guess it could have been that that wasn't the case, right, It could have been that, you know, you study electromagnetism, it's like, oh, it works in this way, and there's this math to describe it. Then when you look at how particles pull on each other through a different force, like the strong force or the weak force, you know, you study that and then it turns out that you need a totally different kind of mas for that and the tooth mass are not compatible. That could have been the case. That could have been the case exactly, and in fact, that is the case for gravity. We have no way currently to bring gravity into this mathematical framework. That's one of the problems we'll talk about later. And so it hasn't succeeded in every single case, but it has succeeded for these fundamental forces, the strong force, the weak force, and electromagnetism. All right, so then that's the standard model. It's something that describes all the known forces except gravity, and all of the particles except a whole bunch of parts. You make it sound like such an amazing achievement, but really this is the accumulation of a huge amount of knowledge and effort and ideas by so many smart people over decades. You know. It really does represent an incredible side into the nature of the universe. But of course there's a lot of work left to be done. Yeah, just the story is left. But let's call it the standard model. Anyways. All right, well, let's dig into the problems that we have with this standard model. What are the missing pieces, what are the things it can't describe, and what are the things that may never describe. But first, let's take a quick break. All right, we're having a standard conversation about the standard model, which is to say that the standard model is not so standard. You don't sound very impressed. I am a pressed. Yeah, describing you know, four percent of the universe or less is pretty good achievement. Yea, what great would you give somebody if they got a four percent on their test? You're the professor, Well, why would you give one of your students of the four percent on a physics test? Yeah? Well, you know, I have to say, what's the curve? Think about all the other alien species out there that have been working on physics for the same amount of time, how far have they gotten? And really you've got the greatest on that curve. I see. You're all about lowering your standards. Is that what you're saying. I'm all about calibrating, man, Well, calibrating this case, lower ring or standards. Maybe maybe it could be that alien species out there basically figured it all out in about twenty minutes and we've been struggling with it for hundreds or thousands of years, depending how you count, and we've hardly made any progress. Or maybe there are aliens out there that have been working on these problems for millions of years and having gotten as far as we have, we just don't know. So then what gray would you give us a for effort? I'd have to go with incomplete, but that's gonna look bad at my transcript. Then, Yeah, I don't think anybody should hire us until we have a sensor whether we're good at this or not. Are the human race all right? Well, let's talk about the problems with the standard model, which I guess is the shining achievement of physics. Right. It described most of the forces that we know about, the strong force, the electoral weak force, and it describes most of the particles that we know about, including all of the ones that were made out of it. Yeah, and before we reveal all the chinks in its armor, let's just spend a moment to appreciate it, because it means something kind of cool about the human experience. It means that basically everything you interact with, every event in your life, everything that happens to you, is mostly explainable, Like there isn't really any magic left in your experience of the universe. Every experience you have, we can mostly explain in terms of the fundamental physics that we do so far understand, you know, lightning and stomach aches and all sorts of things. We think we mostly understand the basic physics of that, even if we can't always make it practical. We can't predict the path of hurricanes that we don't think that. There are mysteries in physics that actually affect your everyday life. And that's a new experience for humanity, right, most humans over the years have lived in a world that was fundamentally not understood by them. Yeah, it's pretty amazing what how much we can describe now although we were sort of they're all already kind of like a hundred years ago, right, Like stomach as we could have predicted the hundred years ago. You don't need quantum physics for that. Yeah, I'm not sure if doctors even now understand the stomaching. Maybe I shouldn't give them too much credit. But you know, there were lots of interesting puzzles about the way the world worked and the particles that were out there that we hadn't figured out yet until we brought them together into this picture of the standard model. But now we mostly understand the world that is around us. So as we dig deeper, of course, there are lots of holes and questions that come up. All right, well, let's dig into some of these holes and and missing pieces of the standard model. And let's start with the big one, the heaviest one, the most massive one. Gravity. Gravity really is the most missing piece of the standard model. Like all the forces that we do experience in our everyday life, the strong force, the weak force, electromagnetism, gravity is the one that we cannot describe yet using the Standard Model, which is in the end, a quantum mechanical description of the nature of the universe. But gravity we have a classical theory. We have general relativity, which ignores quantum mechanics and describe spaces a bending place where particles can move smoothly. Yeah. I know we've talked a lot in the on the podcast about the problems with marrying quantum mechanics and gravity. But maybe it gives a sense of why that's so Hardlet like, I can calculate the gravity between the Sun and the Earth. Why can't I calculate the gravity or gravitational force between you know, an electron and a proton. Well, if you knew exactly where the electron and the proton were, then you could calculate them. You know the distance, you know the masses, all that stuff, But you can write it's possible to know the location of a particle. Electrons are quantum objects, right, so they don't always have a specific location. They have like a probability of being here in a probability of being there. And one question about gravity is like, well, how does that work? Is the gravity of the electron also probabilistic, like the space bend a little bit where the electron might be and a little bit somewhere else with the electron might be. The orders gravity collapse the electron's wave function, requiring it to be in one place, so that it sort of it knows how to bend space the right amount and exactly where. I guess. Maybe the question is like, we can calculate the force between an electron and a proton, right, and as I understand it, it involves like exchanging a photon. But when you can calculate that force and what happens to those two particles, why can I do the same with gravity? Think? If I have an electron a proton, why can't I just calculate how much force they put on each other. So if you're thinking about the electromagnetic force between a proton and an electron, you're right. You can calculate that force and you can think about in terms of photons. And that's a quantum mechanical theory that allows the electron to have a probability being here and probability being there. That's all cool because electromagnetism is a quantum theory. It allows all of that. It treats its objects as quantum objects. But gravity, so far is not. Gravity is a classical theory, and in order to know how much space bends, you have to know where something is and you have to know it's trajectory through space and time, and that's not possible for quantum objects. So people have tried what you suggested, like, well, let's build a quantum theory of gravity and think about exchanging little particles for those forces. They call them gravitons, and so people certainly have worked on that. They have tried to add gravity to the standard model to make it a quantum theory. The problem is those calculations don't work, like, we don't know how to do it yet. Gravity is a different kind of force than electromagnetism is it requires a slightly different sort of mathematical construction to describe it, and those constructions sort of fail. When we try to do those calculations, we get crazy numbers, we get infinities and negative infinities. It just sort of hasn't worked out yet. The crucial way that gravity is different is that it couples to itself. Like a photon doesn't feel other photons because photons only feel things that have electric charges and photons don't have electric charges. But gravity feels everything because gravity feels everything with energy, and so it's sort of a much crazier system to try to describe using this onto mechanical apparatus, and so far it just hasn't worked. You mean, like maybe the idea of a graviton itself feels gravity like gravity, graviton has energy, and therefore it also affects the particles through its gravity exactly whereas a photon doesn't feel the electromagnetic force, and so it's just simpler to do those calculations. That doesn't mean it's impossible to have a quantum theory of gravity, just means it's going to need sort of new mathematical tools that we just sort of haven't invented yet. The tools that we have used so far haven't worked. Can you just invent the graviton that doesn't feel its own gravity. You can do that, And that's sort of actually the first step in an approximate theory of gravity, you know, like a perturbative theory. We say, let's try to describe part of gravity and assume that the graviton has negligible effect on the gravitational shape. Why can it have zero effect? Well, that would be inconsistent with what we think about general relativity and how gravity works. General relativity says that space bends in response to energy density, and so if gravitons carry that energy, then they should also bend space. Well, maybe just don't apply general relativity at the quantum level. Yeah, some people are building new theories of gravity. The tricky thing is that we have a lot of measurements of gravity already. So if you develop a new theory of gravity, it has to also describe everything we've observed so far about how planets orbit each other, and about black holes and all these things that happened at the big scale, you know, the scale of planets and stars and galaxies. General relativity is past all of these tests with flying colors. So if you develop a new theory has to reproduce all of those calculations as well, and so far you haven't been able to do that. So far, we haven't been able to do that. All of our mathematical attempts has sort of blown up in our hands. Sounds like a heavy situation there, But let's get to some of the other things missing in the standard model, because some of them are pretty big. For example, the universe is not covered by the Standard model. Yeah, the Standard Model is really good at describing the kind of stuff that we are made out of, atoms and molecules and quirks and leptons and all these kinds of things. But in the law asked a few decades, we've discovered that that's not what most of the universe is made out of. We know that if you take a random chunk of space like a cubic light year, and you ask how much energy is in there, it turns out that the energy devoted to quarks and leptons and all the kind of things that we do understand and they are described by the Standard Model is only about five percent of the energy in that cube, and then another like twenty five percent is due to dark matter. So weird new kind of matter that we know is out there. We can see it's gravity and all sorts of other effects. We just don't know what it is and what kind of particle it's made out of, except that we're sure it's not made of our kinds of particles, or at least we know or we think it's not made out of the particles that are currently tallied up by the Standard Model. It's possible that is, it is made of a particle, a different kind of particle or something that then you could add to the Standard Model. That's right, that would be the new Standard Model, Standard Model Underscore Final or Update version two or whatever. But none of the particles that are only in the Standard Model, the quarks, the electrons and nuance, the towns of new trinos, none of those can explain what dark matter is. And that's a whole, really fascinating topic. People can dig into a bunch of podcast episodes about why isn't dark matter neutrinos or how do we know dark matter is not some weird clump of quarks floating out there or primordial black holes or something like that. But we're pretty sure that dark matter is not made out of anything that's currently described in the Standard Model, which means it's something new, something weird, And you're right, if we figured out what that was, we would have to add it to the Standard Model, right. But it could also be the case that maybe dark matter is made out of something that is not described by the mathematics of the Standard Model, right, just like gravity could be something not even compatible with the Standard Model. Absolutely, And it's a sort of extraordinary bit of extrapolation to even assume that it might be right, because we've looked at a tiny fraction of the stuff in the universe, and we developed mathematics that works to describe mostly that, and then we imagine that, oh, maybe the rest of it also, you know, even though we know the rest of it is different and important and fundamental ways from the bit we have studied. So it's sort of a leap to say, maybe we can use the same tools to describe the rest of the universe. Maybe right, but also maybe not. It might be that dark matters not made of particles at all. Their theories, a matter that don't have a sort of scale that as you zoom in, always look the same. Right, These things are called unparticles. There's all sorts of other crazy bonkers ideas that are not particle based dark matter. If you ask me, that's what I would love for us to discover because instead of just like adding a new piece to the standard model and building on quantum field theory, it would point to us a new way that the universe operates, a completely different sort of foundational construct that can describe reality. That would be pretty exciting. But also the standard model doesn't describe dark energy, which is like sixties seven of the universe. Right, two thirds of the universe is also unexplainable by the standard model. Yeah, and when we say two thirds again, we're thinking about a sort of fictional chunk of the universe and accounting for the action of the energy. Right, we don't know how big the universe is, and we say two thirds of the universe, some people might be confused about what are you talking about? The universe is infinite. Two thirds is also infinite. So that's why we think about in terms of energy density, Like take a chunk of the universe and ask how much energy is in that chunk, and how is it apportioned. Well, two thirds of the energy of any chunk of the universe we think is devoted to this thing called dark energy, as you say, And dark energy is just our description of the fact that the universe is expanding, and that expansion is accelerating. That every year, space is getting bigger, and it's getting bigger faster every year, and that requires some energy. And as space gets bigger, it makes new space, and that new space has dark energy in it. And so dark energy is a sort of runaway effect that keeps creating more of itself, which creates more of itself to create more of itself. And so actually the dark energy fraction in the universe is growing. It's now the dominant fraction, and unless something changes, we think it's going to forever dominate our destiny. It seems like maybe the problem with the standard model is that it doesn't talk about space itself right, like it talks about particles and quantum fields, and it assumes a fixed, non changing space. But there's all these other theories like gravity and dark energy and the expansion of the universe that assumes that space itself is changing. Whereas in the Standard model it's it's it's almost like a constant or an assumption. Yeah, I wouldn't say that standard model doesn't talk about space, but you're right, it certainly makes certain very crisp assumptions about space that are in conflict with what we know to be true. Right. Usually, quantum field theory operates on what we call like a flat backdrop. We assume that space exists, and that it always has existed, right, and that it always will exist. The basic way the quantum field theory thinks about space and time is not to think about them together the way relativity does, but to think about them separately. And space is something that exists in time is just how things change in space, and so it thinks about space and time quite separately. And turning there's a equation can describe the universe all the way back infinitely in time and all the way forwards infinitely in time. So quantum field theory is consistent with the universe always having existed and always existing into the future. Whereas when we look at space, as you say, we see that it's changing and that it's expanding, And if you think back far enough in time, it's consistent with some crazy event that we don't understand that might even be the beginning of space. So you're right, there basic questions about the Standard model's treatment of space itself that we don't know how to answer. And that's really connected to this question of general relativity, because general relativity is basically a description of what space is, but we don't know how to unify that with our understanding of quantum mechanics. Is there even a room in the Standard Model for expanding space, Like, is there even a lever you can pull there or a mechanism that allows space to expand In the Standard Model. You can do quantum field theory on curved space or on expanding space, but what we don't know how to do is how to have those fields themselves create that curved space, which is what you sort of need for quantum gravity. So it's possible to do quantum field theory on other funny spaces or other dimensions or expanding spaces, that it gets very very complicated. Can it even then explain the Big Bang? Or not at all? So quantum field theory can't explain the Big Bang as like a singularity, right, Quantum field theory can describe what happens in space after that. But it certainly cannot accommodate a singularity. Quantum mechanics that phoors a singularity, right, because there's a fuzziness to information into the universe. You can zoom everything down into a tiny, dense little dot. You can't even have a singularity at the heart of a black hole according to quantum mechanics. So absolutely not. Our description of quantum field theory is not consistent with a singularity at all. And so that's why when we talk about the Big Bang, we talk all the way back to very very early universe, and we say, well, before that, we need some picture of quantum gravity. Quantum effects and gravitational effects are both important, and we just don't have that theory, and so we don't even know how to think about what happened before that time. Well, sort of sounds like maybe quantum mechanics and the stand model will never maybe even be able to explain why space expanded so fast during the Big Bang, right, why the Big Bang happened at all? Yeah, the standard model as we know it has no explanation for that and may never write if it can handle space expanding or ever explain space expanding. Yeah, well, we imagine that there's some future theory, some quantum theory of gravity, which can explain that. And then when you take the version of that theory and ask what happens when space is mostly flat and mostly cold, then you get the Standard model sort of the same way that, like Newton's theory, is a limiting case of Einstein's theory. Right. Einstein's theory of relativity, we think, is a more accurate description of space. But when gravity is weak and there aren't black holes nearby, it reverts to Newton's theory, right, And so we think that probably quantum gravity is a super version of the Standard model, or the other way around, that the standard model is like a limiting case of some deeper theory of quantum gravity. All right, well, those are the two big gaping holes in the Standard model gravity and also dark matter and dark energy. But the holes don't stop there. There are still other gaps in the Standard Model to bring everything from antimatter to neutrinos. And so let's dig into these mysteries. But first let's take another quick break. All right, we're talking about the I guess it's not so standard model or the standard lead incomplete model the current best theory of physics so far that we're pretty sure is wrong. It needs to be updated asap. That's your standard star. No, it's wrong, but we will press on. Standard really just means work in progress, like every theory in science is always a work in progress. Oh, I see you're using that definition of the word standard, like the current model. It's really just the current model. It's just the latest update Standard Model version six, as downloaded onto your phone last night by Apple. We're still on data, is that what you're saying, or and like we're always beta testing science. All right, Well, as we heard, there are still big things missing about the Standard Model, which is exciting to physicists, And there are some big things missing, but there are also other things that maybe people don't think about are missing from the Standard Model. Even if there weren't questions about dark matter and gravity just zooming in on the particles that we do know about, there are lots of questions that we don't have answers to. So you can look at the Standard Model and you can say, like, why is it this way not some other way? And also does it actually explain everything we see? One of the deepest mysteries that remain in explaining the universe that we have is why it seems to be made of matter and not anti matter. In the Standard Model, we have all the particles we've been talking about, but there's also a shadow particle for every single one. Every quirk has an antiquark, every electron has an anti electron, every tow has an anti tow. There's this beautiful symmetry to all the particles. They have their anti part nticles. And yet when we look out into the universe, we see that I'm made of matter. You're made of matter. Our solar systems made of matter, our galaxies made of matter. We think the nearby galaxies are made of matter. It seems like the universe is basically matter. So if the theory of particles is symmetric, how do we get this asymmetry in our universe? Where does that come from? This sort of the big question. I think what you're saying is that the Standard Model does have antimatter in it right, like anti matter itself. It's not a mystery like that, It's actually part of the Standard Model. Every particle in the model has its antimatter particle. But I think maybe what you're saying is that the model predicts that is, there should be the same amounts of matter and anti matter, right like, according to the theory, there's nothing in it that says, oh, clearly matter is the best matter. Yeah, and there's no reason we call one kind of matter matter the other kind of antimatter except that we are made of one kind, right, There really is no difference between matter and antimatter. No, No, if you're not with us, your anti us. If you're not made of us, you're made of the anti us. Yeah. If you're not, if you're not part of us, you're not us. There you go. If you're not particles of us. Yeah, that's the interesting mystery. And you imagine, for example, the very beginning of the universe. We think probably matter and antimatter were made at the same rates, because why not, Because the theory of particles is basically symmetric with respectum matter and antimatter. There's antimatter quantum fields for every matter quantum field. So then the mystery is, how do you go from a universe that has the same amount of matter and antimatter to our universe, which is almost entirely matter. And that's the unanswered question. We're looking for asymmetries. We're looking for ways the Standard model prefers matter to antimatter, or like processes forces something which produces matter preferentially over antimatter, and we have not explained that yet. Well, there are some hints in the Standard model, right, Like, according to the Standard Model, there is a slight little preference for one kind of matter, isn't there There are some process the seas that do seem to prefer matter to antimatter in the Standard model. Yes, in the Standard Model there are some. Right, it's not perfectly symmetric, but these are pretty small. They're not nearly big enough to explain the asymmetry that we see. It's a hint because it's a crack in the perfect symmetry. It says, maybe the universe prefers matter to antimatter, but the effects that we have discovered cannot explain what we see in the universe. Yet we're missing like a huge chunk of it. Like most of the asymmetry is not explained. But I guess if there was an effect that was so large that it preferred a matter over antimatter to the degree that we see in the universe today, wouldn't they be, you know, kind of a big obvious hole in the theory, or is it possible that what it prefers matter or antimatter is external to the standard model like gravity. Yeah, that's exactly the question. And we're looking for those holes in the theory, and people are doing searches for new processes that prefer matter to antimatter, and recently they have some interesting hints for discoveries at CERN. These are called the flavor anomalies, where like quarks change from one flavor to another, and they tend to do it to matter a little bit more often than antimatter. And people are wondering if this is like the thread we're going to pull on that reveals the universe's preference for matter or antimatter. But nothing is certain yet. But you're also right, it could be something else, something external to the standard model. It could be that the universe wasn't created symmetrically with matter and antimatter at the beginning because of some theory of quantum gravity that prefers matter to antimatter. We just don't know. It's a huge question. Mark. Well, I am pro finding the answer to that. I'm not anti that. Now, what are some of the other things that are missing from the standard model. There are also just a lot of missing explanations for the patterns that we see. Like if you look at the patterns of the particles, you see that there's a four basic particles, the up, the down, and the electron and the neutrino. But each one has two copies, right, The up has the charm and the top, the electron has the muon and the tow And this is sort of nice consistency there where each of the four based particles has exactly two copies. But the question, of course is why, right, why should particles have any copies? You know, there's like matter and antimatters, the particles have like a single reflection. Why do these particles have these weird, heavier copies and why two of them? That's totally unexplained. It's just sort of like what we see, and to me, it's like a hint. Is suggests that there's something happening underneath out of which this emerges, but we just don't understand anything about what that is. We do we know for sure there are only two or three generations of particles, or is that just what we've found, or it can find with our colliders. Is it possible that there's an infinite number of generations we just can never get to them because they require too much energy. It's a really cool question. We're pretty sure that there are only three kinds of each of these particles, and the reason actually is the Higgs boson, because the Higgs boson interacts with all of these particles. So when we make the Higgs boson at the large Hagon collider, we sort of make it out of these particles. We throw corks and gluons together and make a sort of a frothing mass of energy g and the Higgs boson pops out of that frothing mass. And it does so because it interacts with all of those particles. And so the rate at which interacts with those particles determines how often it's made. And if there were more of these kinds of particles, if there was like a super top cork, or like a heavier bottom cork than the theory predicts, the Higgs boson would be made much more often. So by measuring how often the Higgs boson is made in our collisions, we can actually measure how many generations of particles there are. Because the number of generations determines how often we make the Higgs boson. So we're really pretty sure there are three. But we don't know is why there are three. What could there be maybe uh, super higgs boson or heavier higgs boson, or another generation of Higgs bosons that we don't know about. There definitely could be We did a whole podcast about other Higgs bosons and it might be there. And there might also be other kinds of corks. They just would be different, like they don't talk to our Higgs boson or they're different in some way. So precisely, the statement we can make is these kinds of corks, the quirks we have found so far, we're pretty sure there are only three of them. But there could be other kinds of weird corks that don't talk to the Higgs the same way and do other stuff that are out there. And there's no limit on how many other weird heavy particles could exist that we just haven't found yet. MM. But I think what you're saying is if you look at the math, if you look at the math of the Standard model, it doesn't prevent you from having more generations or have your cousins of the electron. It's just that experimentally, you haven't seen any or seen any evidence that more could be there. Yeah, directly, we haven't found a name. We've looked, and indirectly we have some constraints because we think if they exist, they would influence how often the Higgs boson is made, the large Hagon collier. But mathematically there's no limit, that's right. Mathematically there's no limit. Yeah, there's no reason the Standard model couldn't have four or seven generations or ninety thousand generations and particles. Mathematically there's no reason why not. But it's an interesting clue, and people wonder, like, what does it mean that there are three is the universe? Like three? Ish? Is this just what it is? Or is there a reason for it? All? Right? What else is unexplained? Another really fund mystery is neutrinos. Right, Neutrinos are part of this basic list, and we know they exist and they're out there and that there are three kinds of them, but we really don't understand their masses. We know that they do have mass, and those masses are very very small, but our theory, the Standard model, actually doesn't allow them to have any mass. The theory requires that they have zero mass, and we go out there and we measure them and we see that they do have mass. And so this is actually where people disagree about what is the standard model. The sort of official, official standard model has neutrinos with no mass, and now people have like a new version of the standard model where they've incorporated neutrino mass, and some people say that's the standard model. Wait, what do you mean the standard model doesn't allow the neutrino to have mass. What does that mean? Well, this sort of old school standard model has a bunch of rules for what these particles can do. Like you have to keep track of the number of electrons. You can't just create or destroy electrons. You have to keep track of them and conserve number of electrons in the universe. It's like a hard and fast rule in the old school standard model. But if the electron neutrino has a little bit of mass, then it can do something tricky to sort of break this accounting. We had a whole podcast episode recently about sterile neutrinos and and all this kind of stuff, and so it breaks that rule in the old school standard model. So if neutrinos have mass, and that hard and fast rule, and the old school standard model doesn't really hold up anymore as a hard and fast rule. It's like approximate now. So we have that sort of an updated version of the standard model where you give neutrinos mass and it breaks these rules a little bit. Some people consider that the standard model, and some people consider that beyond the standard model. What happens if you do allow mass in the standard model for neutrinos? Are you're saying, other contradictions pop up? Yeah, we don't really understand how that works yet. There's a bunch of experiments to try to measure those neutrino masses and they don't agree with each other. There's a question about are there actually just three neutrinos or is there like a sly fourth neutrino out there, the sterile neutrino that's been messing up a few experiments that are out there. We don't understand if neutrinos get mass the same way the other particles do through the Higgs boson, or if they're a really weird particle, like maybe they are their own anti particle particle called a maorona. Particle which would get mass in a completely different way, not from the Higgs boson. So neutrinos are so of the next frontier, like a part of the standard model that we've only really just begun to explore and really haven't nailed down very well. Interesting. Well, we don't have a lot of time left, but there are still some interesting things missing from the standard model. Maybe you want to step of studies pretty quick. There's so many things we couldn't even cover them all. One of my favorites is a question of whether there are particles out there that have just a north or just a south magnetic charge, Like there are particles out there that have a positive or negative electric charge, but so far, every particle we've seen in the universe has a balanced magnetic charge, like you see particles with north poles and south poles. You never see particles with just a north pole or just a south pole. That would be called a magnetic monopole. And actually the theory prefers that they do exist, Like if they do exist and the the theory is more symmetric, it's more balanced than if they don't exist. So it's kind of a mystery why we don't see them in the universe, and a lot of physicists believes that they must exist somewhere out there in the universe, but we've never found one. But probably the deepest question that's open and remaining for the standard model is what's next. We look at all these particles and we wonder, like, is this the base description of reality? It can't possibly be there all so many weird patterns we don't understand. And you know, a hundred years ago we looked at the periodic table, we saw these weird patterns we didn't understand. Turns out all those patterns were clues that said, oh, there's something deeper going on. All these patterns are just complexity that arise from how the little bits that things are made out of fit together. So now we're looking at the periodic table, the fundamental particles, and we're seeing all these patterns that we don't understand, trying to explain them and wondering if they're made out of some smaller bits that we haven't yet seen, and maybe those bits are made of smaller bits, and those bit are made of smaller bits, and maybe this like a hundred levels between us and the base layer of reality, or maybe just one or two, or maybe there's no bottom. Yeah, I guess it's kind of tricky because at some level you have the standard model and you're seeing these patterns and maybe hinted something deeper. But at the same time you also know that the standard model is not correct, right, Like you know they has hu mongous gaps in it and lots of things missing. Kind of makes you wonder how much you should read into these patterns, or whether even exploring those patterns is going to be useful. Yeah, we don't know what the best way forward is. When you read the history of physics, it's written to sound kind of linear, like we did this, and then we figure that out, and then we figure this other thing out. But remember that at the same time, there were lots of other branches. People were exploring other crazy ideas which made sense to them at the time when they were at the forefront of human knowledge. But we mostly erased those other zigzags and those other branches from our history of physics to give you a description of sort of the theory we ended up at. But now we're here at the forefront of human knowledge right now, we just don't know what is the right way forward. Should it be quantum gravity, Should it be anti matters, Should it be magnetic monopoles? Should it be cracking open the electron to see what's inside. We don't know what's going to yield some inside, so we're all just sort of like being curious and exploring and hoping to figure something out. So the basic answer is that we've given you all this money and still wide open question. It's still a wide open question, which makes for a wonderful, mysterious universe that we get to keep talking about on the podcast. It sounds like maybe the answer to getting are great as a species in the giant physics exam of the universe is to ask for an extension. Daniel, what's your policy and given students extensions. I'm pretty lenient. Actually, yeah, I'm pretty lenient. What if they come to you say, hey, instead of doing physics, I've been spending all my money making Marvel movies and creating Netflix. Can I get an extension? Yeah? Sure? Can I get some free tickets? I see you're open to being bribed as a greater No. I think people should go out there and explore their passions and discover who they are, and everybody can contribute in some way to this incredible journey we call life and the exploration of the universe. It sounds like a standard answer, Danny, Well, stay tuned as we keep exploring the universe and discovering more about what we know and when we don't know about this amazing cosmos. We hope you enjoyed that. Thanks for joining us, See you next time. Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of I Heart Radio. For more podcast from my Heart Radio, visit the i heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows.