Daniel and Kelly’s Extraordinary Universe - What is a symmetron?

Episode Date: January 2, 2024

Daniel and Jorge talk about creative ways to explain the accelerating expansion of the Universe. See omnystudio.com/listener for privacy information.

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Brought to you by Novartis, founding partner of IHeart Women's Sports Network. Hey, Jorge, are you a collector? What do you mean? Like a debt collector? I mean, like, do you have a room in your house full of original Transformers still in the packages? I wish, but no, those might be worth a lot of money now. But no, I actually took them out and played with them, although I wish I had those also. So is that the source of your encyclopedic knowledge of Pokemon and Transformers?

What do you mean? Well, you know, every time I describe some new hypothetical particle, you tell me that's actually the name of a transformer. I don't think that's because I'm an expert. I think that's just because all physics names sound like Transformers. Or maybe because we actually stole them from Transformers. What? Do you have to give credit then to Hasbro in your papers? Yeah, we give them a share of the zero dollars we make off of each particle.

What do you mean? You don't work for free, do you? The particles do. They just cost tax dollars. Hi, I'm Horya cartoonist and the author of Oller's Great Big Universe. Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I hope to never have to name a particle. Wait, why not?

Doesn't it mean you discovered it? Oh, I'd love to discover a particle. But then I'm given that huge responsibility of choosing a name, and frankly, after all our conversations, I'm terrified. You're terrified of cartoonists? criticizing your name choices? I'm terrified of legacy, history, man. People who have given particle silly names, history doesn't look kindly on them. Oh, I see.

So that's your excuse for not having discovered a particle? That's one of my many excuses, yes. That sounds a little convenient. No, the truth is I would love to discover a particle. And in that case, you know, I just crowdsource the name. To your kids, maybe? To the internet. So I'd end up with, like, particle face.

Is that a website? Like, is there a website for coming up with particle names? Not yet, but what a great idea. You can find anything on the internet. I wonder what would happen if you asked Chad GPT to come up with a name for a new particle. Let's do it. Naming a new particle is a significant responsibility. It suggests we avoid personal or self-referential names.

We should consider it as properties. We should name after historical figure. We should consult with the scientific community. See, this is serious stuff. I feel like maybe that Chad GPT is trained on your neurovales. It seems to know your anxieties. Maybe it's been learning all this time that you've been talking to it. No, I think chat GPT and I are both trained on the neuroses of the internet.

Well, now you have chat GPT, so you have no excuse for not discovering a new particle. All right, I'll get to work. But anyways, welcome to our podcast, Daniel and Jorge, Explain the Universe, a production of IHeartRadio. In which we are absolutely desperate to understand the nature of the universe, to uncover new particles and forces to reveal the fundamental nature of space and time and to put it all together to explain our experience in this crazy cosmos.

Whoa, well, desperate. I don't know if we could go that far. You make us sound kind of thirsty. I am thirsty for knowledge. Absolutely, yes. You're thirsty to get it on with the particles of the universe. I mean, I've said it before. I would invite aliens to Earth,

even if I knew they were going to zap us from orbit, if they would only tell us the truth of the universe. Boy, you would make that choice for the entire human race? I'm thirsty, man. I've got a thirst and it's got to be quenched. That sounds like a good excuse to put you in a rocket ship and shoot you out of here. You're clearly not on our side.

I'm on the side of knowledge, man. You're on the side of dinner, apparently. But yeah, it is an interesting universe, and we are really at a loss for understanding how it all works, what it's all made out of, and what are the rules that govern, what can happen and what cannot happen in the universe. Though you might feel like the universe is pretty well understood,

scientifically speaking and historically, we're just beginning our journey of understanding it. In 100 years or in 500 years, people will look back on this era of science and say, wow, they were very clueless about how the universe worked. Do you think that's a very optimistic view of humanity? That will be around in 500 years to look back, you mean? Yeah, that we're not going to go into the, you know,

post-apocalyptic healthcape of human beings. and we'll look back at this time as maybe the peak of humanity in our caves in a few hundred years scratching out podcasts for our few listeners we will look back to the golden age of science when Daniel didn't discover anything we're gonna look back and be like what's a podcast was that a particle who had time for that you're right I'm implicitly being optimistic I'm assuming that scientific knowledge will continue to accumulate and the pace will continue to accelerate the way it has over the last decade, 50 years, even 100 years. I'm hopeful, but that requires us to survive and maintain

society and to make science a priority. Yeah, and not to sell us out to the hungry aliens. Hmm, though that would fast forward us into the future of knowledge and dinner. Yeah, but what if the aliens don't have all the answers? Well, what if they have the answers and we just can't grok them? Oof, so frustrating. I just sold the human race for nothing. Yeah, you might want to look at the many first, figure it out before he sell us all out. But we can't rely on those aliens or even those future humans. We got to figure it out. We are working hard today to try to understand the nature of the universe on the largest

scales. How big is it? How much bigger is it getting and how quickly is it getting bigger? That's right. We're on our own trying to figure out the mysteries of the universe. And it all starts with asking questions and coming up with maybe sometimes crazy ideas to try to explain how it all works. We're pretty sure that most of our ideas about how the universe works in the largest scale, the size of it, the shape of it, the rate of its expansion, why it's expanding, why that expansion is accelerating, we're pretty sure those ideas are wrong.

And we'll be looked back on as just sort of like initial explorations, but that's crucial. Science is not a straight line. It's a zigzag wandering through a dark forest, hoping to find the clearing. And so sometimes you have to get creative about it and even come up with things that sound like transformers or Pokemon's. Or maybe come up with transformers. That would be pretty cool. They could help us find the answers to the universe. You think they'll be mad when they discovered

even stealing their names for particles for a few decades? Or maybe they'd be honored to be named after certain particles. Now you're the one being optimistic. Yeah, I am an optimist prime. And so today on the podcast, we'll be tackling the question. What is a scimitron? And what does it transform into? What does it not transform into?

Maybe it transforms us into aliens that do understand the universe. What is the simatron? I don't think I've heard that word before, but it sounds a little bit like symmetry and tron, so something electronic. You're not far from the truth. Yeah, boom, podcast over. Do you know why the word tron or ending a word with tron somehow implies electricity

or technology or particles? Do you know the origin of that? I'm asking if you know, because I don't know. I think the word ion comes from some Greek word, but I'm not an expert in the etymology of particles. Oh, you're saying like maybe that's where the word electron comes from? Yeah, although you know the electron originally was named something else. The discoverer of it, J.J. Thompson, called it a corpuscule,

and then later it was renamed Electron. But my guess is that all these ons come from ion, which is a Greek word. Well, I guess that was a good thing because otherwise we'd be a associating technology with the word puscal, with the ending puscal, and everything would be named Puscal. The bad guy in Transformers would be called mega puscal. But I'm guessing this is maybe one of those creative ideas that the scientists have come up with to try to explain some deep mystery of the universe.

It is indeed. Well, as usual, we were wondering how many people out there had heard of a simetron or could guess what it is or what it transforms into. So Daniel went out there into the internet again to ask people what is a scimitron? Because this podcast is all about audience participation. You guys can write us questions and we'll answer. You can hear your voice on the podcast speculating about the topic of the day.

If you'd like to join this group, please write to me to questions at Danielanhorpe.com. So think about us for a second. Is it a Pokemon or is it a robot? Here's what people had to say. Well, it's either a transformer or a, quantum particle or both. Symmetron, it obviously has something to do with symmetry. Other than that, I can't really hazard a guess. I'm guessing based on the on at the end of it, that like a photon or a

baryon, that it's some kind of particle that conveys a type of symmetry. Well, symmetry makes me think of cyclotron. And a cyclotron, I think, is the old term for a, well, another term for a particle collider. And symmetron symmetrical would be sort of means that it's the same in some way. Maybe is it a straight as opposed to a ring format particle collider? While I've never heard of a symmetry, it sounds like a particle that exhibits some special symmetry, but lots of particles exhibit symmetry, which makes me think it's probably some theoretical symmetry we haven't seen yet that defines what this particle is. A symmetry is a device that you can set on top of your piano to keep the pace. It goes tick, talk. No, I guess it's a particle and it communicates

symmetry between other particles. I have no idea. Is it a particle a wave that is identical to another particle wave that cancels it out maybe or doubles it? All right, some creative answers here. Well, I mean, you put this name on anything. You could name it your cat, right? The answer to the podcast could be like, Simetron is my cat. Well, there you go. You could name your cat Simetron, yes.

But isn't that a big responsibility also to name your cat? That's true. Although I don't think history will judge you as much because it's probably just between you and the cat mostly. Unless the cat becomes famous. Yeah. Well, also, you don't mind your cat unhappy with you. I hear that's a bad thing.

It'd be a catastrophe. In the end, it's the cat. cats who are in charge. But yeah, it's an interesting idea. And so let's dig into this, Daniel. What is a symmetron? So a symmetron is a hypothetical new particle that, of course, also comes with a field that has really unusual properties. And physicists invent a new field and particles sometimes, not just for fun. We don't just like lie in the grass and be like, hmm, what if there's this kind of particle, we do it to explain something we've seen in the universe. Remember, the whole process of physics is like, go out there, see,

stuff that happens and then try to build a model that explains it. And when the model fails, we add new who's it's it's and what's it's to try to get it to describe the universe. So the simetron is a new thing people are trying to add into our model of physics to explain some stuff that we otherwise can't explain. Although sometimes in the history of physics, it has been the case that you just kind of like tool around in the lab and you discover stuff, right? Oh, there was a golden era of the particle zoo when every time you turned on the accelerator, you saw a new particle. and you could give it a name.

Every time? It was incredible. Every time they cranked up the energy, boom, new particles made. It was amazing. I missed those days. They were decades before I was born, but I still missed them. But I think we're talking about a theoretical particle here, not one that we have discovered or seen or explored experimentally,

just one that we have dreamed of to try to explain something that is happening that we can't explain. Yeah, in the same spirit that, like, the Higgs boson was conceived of, theoretically. Peter Higgs saw this pattern in nature and he thought, hmm, this would be so much prettier. It would make much more sense if we added a new particle and field to the story. And it all worked out mathematically and beautifully. And then we went out and looked for it. So you can add things theoretically, but if they don't actually describe what's happening in the universe, it's not very useful. So in this case, people are again adding a new theoretical particle to try to explain some stuff that otherwise doesn't make sense. Okay. So then what is the mystery that the simitron hope

to resolve. So the Cimetron is here to do battle with a really big question in physics, which is why is the universe expanding faster and faster every year? Like, we know the universe is really big. We can look out there and see stuff that's really far away. We've known for like 100 years that the universe is expanding. You look at in every direction and you see galaxies moving away from us. But a couple of decades ago, we got precise enough measurements about how that expansion is changing over time that we learn something kind of shocking, that the expansion is not slowing down like Einstein thought, but that it's actually speeding up. There's something out there accelerating the expansion of space. Meaning it's getting bigger, faster and faster each time. Yeah,

space between galaxy clusters is getting bigger and every year it's getting bigger at a higher rate. So new space is being created faster and faster. And they're not just running away from aliens that want to eat them. They may be accomplishing that, but it's sort of a secondary thing. And in physics, we give this a name, dark energy. But just because we give it a name doesn't mean we understand what's going on or we can explain what's happening. So far, this is just observational.

We've seen this in our telescopes and in our measurements. And we've tried to grapple with it. We've like, what could explain this? What possible mechanism could we have that could generate this kind of crazy accelerating expansion? Because I guess the idea that it's accelerating is weird, right? Like if it was expanding at a constant rate, then you might assume that, well, maybe you had some initial velocity from the beginning of the universe and so it's just coasting and getting bigger. But the idea that it's accelerating means there's something going on, right? Something must be powering this acceleration.

Yeah, exactly. It was really shocking in the context of Einstein's general relativity because in his model, if you have a universe with mass in it, that causes no. negative acceleration of the expansion, basically pulls everything together. It curves the universe and it pulls everything together. Basically just gravity should pull the whole universe together. But when Hubble and others discovered that the universe is expanding, then people thought, all right, so we have an expanding universe. As you say, initial velocity, but still should be negative acceleration because all the gravity should be pulling everything together. And we didn't know if there's going to be enough gravity to pull everything back together to

like squeeze it down into a big crunch. Or if there's going to be so much velocity, that it coast forever slowing down but never actually come back. Then we discovered that neither of those are the case and what actually happening is something else, he's giving us positive acceleration, is increasing the rate of expansion every year. Now, back then, do we know that it was space itself that was expanding or did we maybe think that all the galaxies were just moving through space

and getting further apart from each other? How far back then are you talking? You're talking Einstein and Hubble, or are you talking discovery of dark energy 20 years ago? I mean before an hour ago. Before I'm becoming familiar with this topic. Well, ever since we've had general relativity, we've understood that to describe the expanding universe is to describe the expansion of space itself.

Because general relativity tells us that the universe is a shape and it has curvature and so you can't have like a single reference frame for the whole universe. Instead, you should think about it as like a reference frame for each galaxy and then those reference frames are moving relative to each other, and space is expanding between them. So you can't really answer the question, like, what is the velocity of that galaxy and measured in our frame? You really just have to say, they have a frame, we have a frame, and the space between them is expanding.

But back then, did we know that? Like, when we first noticed that the galaxies were moving away from us, did we know that it was space that's expanding, or did we maybe at first thought, oh, they're just moving away from us through space. Well, all this requires is general relativity, which we've had well before we knew the universe was expanding. So the answer is, yes, we've described in terms of expanding space since the beginning. This might sound a little confusing to listeners because we often talk about the recession velocity of galaxies. And when you hear about the expansion of the universe, we talk about these velocities. And for stuff that's really, really far away, you could even say

that recession velocity is faster than the speed of light. That's just sort of a sloppy shorthand that's saying, well, look, we know it's space expanding, but that's hard to think. think about. So let's just pretend we could measure the velocities of those galaxies. If we could do that, what would that velocity be? But those velocities aren't meaningful. We can't actually measure those things because we don't have a single frame that puts both galaxies in it. So the technical way to think about it accurately is to think about separate frames with space expanding between them. You're saying like these velocities are really just the expansion of space getting bigger. Yeah, exactly. And you know that because you can't measure that acceleration. Like if you wanted to

think about it in terms of acceleration, then all those galaxies should be accelerating away from us. You should be able to measure that acceleration. You're like, have an accelerometer in that galaxy. You should be able to measure it. But you can't because there is no real acceleration there. It's just the expansion of space. If you put a ball in the back of a pickup truck, doesn't slant one side because space is expanding in some direction, right? It stays flat because we don't measure any local acceleration because we're not accelerating in our frame, even though the expansion of space between us and other galaxies is accelerating. And all of this happily lives within general relativity, but it requires an explanation the same way like you need mass to bend space. You need

something to provide this negative pressure to expand space. And the big question about dark energy is what is that? What is doing this thing? What is providing the energy to accelerate the expansion of space? Okay. I think you're saying that space is growing. It's not just growing. It's growing faster and faster so that the galaxies look like they're accelerating away from us but really it's just the expansion of space that's kind of like going at double time and so the question now is what's powering all that creation of new space and so that's kind of what dark energy is a placeholder for yeah dark energy says something's doing it we don't know what and the cool thing is you don't have to throw away general relativity general relativity has a knob in it this is called Einstein's cosmological

constant you could just crank this knob up and say what if there's energy and empty space? If all of empty space is filled with potential energy, then general relativity says exactly this would happen. The question is, is that what's happening? Is the universe filled with this potential energy? Where does it come from? What field would that be?

So you can incorporate it into general relativity if you have like a field that has a lot of potential energy, but we don't and we can't explain that. So there's like a mechanism within GR to do this, but we don't know how to turn that mechanism on. Meaning like you have your equations, and you put a number in, there's a term in the equation that explains or that would account for this acceleration of space growing.

And so now the question is like, what is that number? What's costing that number? Is it a field? Is there a particle associated with it? Are there Pokemon's hidden inside of there? Yeah, that's exactly right. General relativity says, if you have a field with high potential energy, then that translates to a number in these equations,

and that creates accelerating expansion. But what is that field with potential energy? We look around to all the fields we know, like the Higgs field, which actually does have significant potential energy. And we try to calculate what number we should put into the equations. And we get some number. But the number we should put in from our calculations is different from the number we need to explain the acceleration by a huge amount, by 10 to the 100. So if there's potential energy out there in the universe, it's not from a field we know about. All right.

Well, let's get into those discrepancies. And let's go deeper into this mystery that might be soft. called by the Cimetron. So let's think into that. But first, let's take a quick break. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed.

There's been a bombing at the TWA terminal. Apparently, the explosion actually impelled metal, glass. The injured were being loaded into ambulances, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and order, criminal justice system is back. In season two, we're turning our focus to a threat that hides in plain sight that's harder to predict and even harder to stop listen to the new season of law

and order criminal justice system on the iHeart radio app apple podcasts or wherever you get your podcasts my boyfriend's professor is way too friendly and now i'm seriously suspicious oh wait a minute sam maybe her boyfriend's just looking for extra credit well dakota it's back to school week on the okay story time podcast so we'll find out soon this person writes my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone. Now, hold up.

Isn't that against school policy? That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor, and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet.

So, do we find out if this person's boyfriend really cheated with his professor? or not. To hear the explosive finale, listen to the OK Storytime podcast on the Iheart radio app, Apple Podcasts, or wherever you get your podcast. A foot washed up a shoe with some bones in it. They had no idea who it was. Most everything was burned up pretty good from the fire that not a whole lot was salvageable. These are the coldest of cold cases, but everything is about to change. Every case that is a cold case that has DNA. Right now in a backlog will be identified in our lifetime. A small lab in Texas is cracking the code on DNA. Using new scientific tools, they're finding clues in evidence so tiny you might just miss it. He never thought he was going

to get caught. And I just looked at my computer screen. I was just like, ah, gotcha. On America's Crime Lab, we'll learn about victims and survivors. And you'll meet the team behind the scenes at Othrum, the Houston Lab that takes on the most hopeless cases to finally solve the unsolvable. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. I had this overwhelming sensation that I had to call her right then. And I just hit call. I said, you know, hey, I'm Jacob Schick. I'm the CEO of One Tribe Foundation.

And I just wanted to call on and let her know there's a lot of people battling some of the very same things you're battling. And there is help out there. The Good Stuff Podcast Season 2 takes a deep look into One Tribe Foundation, a nonprofit fighting suicide in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission. I was married to a combat army veteran,

and he actually took his own life to suicide. One Tribe saved my life twice. There's a lot of love that flows through this place, and it's sincere. Now it's a personal mission. I don't have to go to any more funerals, you know. I got blown up on a React mission. I ended up having amputation below the knee of my right leg

and a traumatic brain injury because I landed on my... Head. Welcome to Season 2 of the Good Stuff. Listen to the Good Stuff podcast on the Iheart Radio app, Apple Podcasts, or wherever you get your podcasts. All right. We're talking about the Cimetron, which is so far an imaginary or imaginative particle that scientists have thought of to try to explain why the universe is getting bigger, faster and faster. And Daniel Lieber saying that we have, equations for the universe, there's a number there that maybe explains or that would give you a universe that's expanding faster and faster. But now the question is, what is that number? Is it a field like our other

fields or is it just a fudge factor or is it just the finger of God? Yeah, we actually know what the number is, right? We know exactly what number you need in the equations to get the accelerating expansion that we see. The question is, where does that number come from? And there's a bunch of possible explanations. One is like, look, every universe just sort of has a number and ours is generated with this one. That's sort of like give it up, shrug it off, anthropic explanation and say, there is no answer. It just is what it is. Move on, nothing to see here.

Meaning it doesn't correspond to anything physical. It's just that the equations of our universe don't balance out to zero. They balance out to some random number. Yeah, Einstein's cosmological constant can come from a field with potential energy. But you can also just put a number in say, oh, these are the equations. of our universe. They have this number in them. Why that number? Well, you know, every universe gets a random number and there's an infinite number of universes and this is the one that we're in. It's not a great explanation, but it's unexplination.

I mean, like, why does the universe have to balance out to zero? You could ask that question too, right? Like, why doesn't it balance out to 3.47? Or 42, right? That's the best number anyway. Right. Yes. That's the answer. Exactly. And now we finally found the question. But those of us who are curious about the universe aren't satisfied with just being told, I don't know, it is what it is, move on. We want to know if there is an explanation. And so many times in the history of science, we found things that looked weird and we dug deeper. And we have found explanations, reasons why it had to be this and not something else. And so some people have explored this idea of like, let's create new fields that have high potential energy that maybe could explain why we have this number and not some other number that we need to put into Einstein's equation.

Meaning, like, we need this number to make the equations balance out or to match what we see out there in reality. And so let's pretend that this number actually represents or maybe it comes from some kind of physical field of the universe. Yeah, exactly. Because then we get to kick the can down the street and say, oh, the expansion is due to this potential energy from this field. And then we can ask, what's this field all about? Why does it have to exist? How does it fit in with the other fields? And we get to, you know, keep asking questions.

Yeah, stay employed. Stay curious. Stay curious. Don't be so cynical. All right. Well, so then the idea is that this constant, this number in the equations, represents a field. And is this the symmetron field then? No. So the symmetron field is a slightly a weirder version of this. The simplest idea is to just use a constant, but there is no field out there that we know about that provides this constant. So instead, people are trying another idea.

Instead of having a constant, they add a different term. But wasn't the Higgs field a constant too? They put in a number which isn't constant. The Higgs field is a constant. It's just not enough, right? The Higgs field provides a tiny little bit, but doesn't provide enough to explain the accelerating expansion. So people thought, oh, well, let's try adding a different kind of term.

Instead of just adding a number, let's add something which has a derivative, right, which doesn't disappear when you ask about the changes. Meaning something that's changing with respect to time, for example. Yeah. Like a variable, like a variable instead of a constant. Exactly, a variable instead of a constant. Now, for a long time, this has not been a very popular idea, because that does more than just explain the expansion of the universe and its

acceleration, it also creates new forces. It says, oh, well, if you have something which varies, it basically changes how gravity works in a way that creates a new force on things, so like a fifth force. So this has not been a very theoretically popular way to go because it creates a fifth force and, you know, we don't see any fifth forces. But I guess the question is, if a constant explains the expansion of the universe, why do you need a variable?

Why don't just stay with a constant? Because we don't have an explanation for that constant. So the idea is just make it more complicated? The idea is to make it more complicated. Say maybe a constant is the wrong way to go. We couldn't make it work with a constant. We have no way to explain that constant. So instead, let's choose a different term that's not constant, that's variable.

It's like let's look under a different kind of rock because we ran out of the original kind of rock. I guess maybe explain to our listeners, what does it mean to explain it? How does the constant fail to explain the expansion? The constant on its own wouldn't fail to explain it. Like, we know what constant you would need to put in there to explain the accelerating expansion. We just don't know how to justify that constant. Like, where did it come from?

There's no field we know about that can explain that constant. But then if you put a variable, couldn't you also ask the same question? Like, why is it there? Absolutely. If you put in a variable, you also need to justify it. It's just another idea. And then you need to explain, like, where is that come from? The answer is, oh, it comes from a new field that we haven't seen yet.

Well, let's talk about what that field is and how we might see it and what it would look like. Oh, I see. No, actually, I don't see. It sounds like maybe you're just making it more complicated, just to make it more complicated to see if maybe the universe is actually more complicated. But it sounds like it's not, though, because it sounds like a constant, you know, matches what we see experimentally. You know, when you're in the early days of scientific ignorance, you try lots of things. You try the simplest thing first, usually, and that's like just put in a constant that hasn't really worked because we don't have any way to explain those constants. So And now we're trying the second simplest thing.

We're like, well, let's put in something which changes a little bit, which has features and wiggles and is a little bit more complicated. And let's just see what that predicts. And if that's the universe we live in, yeah. Maybe we do live in a more complicated universe. Maybe there isn't a constant in this equation. Maybe there is something that changes. I see.

You're just kind of exploring what these things can be. Like maybe what you're measuring is more complicated than what you're actually seen. Yeah, exactly. It's like if you notice cookies disappearing from your kitchen counter, simplest explanation is your kids eat it. But, you know, maybe there's some new animal out there you never discovered before that only eats kitchen cookies. And so you should consider the hypothesis and it might take you new places like let's go look outside to find evidence for this new crazy cookie eating animal. Because maybe it does exist in your universe.

In the same way, here like the simplest explanation hasn't really panned out. So some people are like, well, let's look for a slightly more complicated cookie eating universe. But did you ask your kids if they took the cookie first? In this hypothetical scenario, I have somehow alibied them out of the cookie. Yes. I see. Well, why not even go further? It was aliens that ate the cookies.

Yeah, exactly. You could go further. And there are people doing that, right? There's no limit on what you can do in theoretical physics. It's just a question of like, is it a good idea? Is it compelling? Does it lead to something we can test? Is it an interesting thing to explore?

And it's just up to the individual. Like, I'm sure there's some theoretical physicist out there going like, oh, yeah, I have an even more complicated theory that's really cool. I guess what I'm really asking is you're saying that you can't really explain a constant for that equation. So are you saying that maybe adding a variable will lead you to an explanation of that variable? Yeah, exactly. Let's put in a variable and see if we can explain it. Let's explore the consequences of that variable. What does it mean for other things in the universe?

What predictions does it make? Can we go out and test those? If you predict that there's some new cookie-eating lizard in your backyard, then you have something to go look for, you know, scratches on your window or something. So in the same way, we're like, let's add a slightly more complicated theory of the universe to explain this accelerating expansion and also see what else it predicts that maybe we could find. All right. So then the symmetron field is a special new kind of field, which has a variable and not a constant in the equations of the universe. Tell me about this field. So mostly these fields are really not mainstream theoretical physics for one important reason, which is that the variable nature of them produces this extra force.

And people are like, well, we've never seen this extra force. So that's out. So if you're going to build this kind of theory and you really want to make it work, you have to come up with an explanation for why we haven't seen it yet. Wait, why does it predict the force? Because when you put that number into Einstein's equation to figure out how things move, you end up having to take a derivative of it. If it's a constant, that goes away. If it's not a constant, if it's a variable, then its derivative doesn't go away. Its rate of change with time is non-zero, and that changes how things move. And effectively, that's like a force. It sticks around. It, like, influences the acceleration of other things in the equation. And so, therefore, that's what you call a force. Yeah. Basically, it's like it changes how gravity works as if there was another force out there.

Right, but we haven't seen a force like that. And so now the question is, like, how do you contort your theory so that it explains why we haven't seen its force? Yes, exactly. And so the simitron is one of a category of theories like this. There's another that's called the chameleon theory, another that's called the Galileon. theory and this one is called the symmetry and has a particular way to avoid being ruled out by all these experiments as a symmetry field and this symmetry field behaves differently when there's a lot of stuff around when it's like high density materials and when it's low density materials so in high density regions like within galaxies and in our solar system etc etc there's a symmetry in this field is like basically two parts of it that balance out and you get no force so it basically doesn't exist

within the galaxy, which is cool because it doesn't change how the solar system works, and we've measured that very precisely. We would have noticed if something was weird. But out past the edges of the galaxy where things are very, very low density, the symmetry in this field breaks. And the broken symmetry there is what creates that force. So basically, the symmetry field behaves differently. When there's a lot of mass around, it goes away.

And when there's no mass around, that's when it really starts to take effect. That seems very convenient. I think contrived is the way to think about it. Yeah, contorted. Made up. And that's not something to be ashamed of. Like, this is how theoretical physics works. So, like, here I have an idea, that conflicts with what we know about the universe.

Can I avoid that somehow? Can I add some bells and whistles to my theories to avoid this experimental measurement? I literally hear theorists doing that all day long. And how often does that work? Never so far, I guess. Never so far. Well, why not keep doing it then? No, no.

I mean, you can go back to the Higgs theory. Like Higgs had to come up with some new particle and new field, which explained this puzzle and didn't violate any of the other experiments people had done. And so I'm sure that ruled out all sorts of other simpler explanations that people first considered. All right. So then the Cimitron field is this theoretical field. And it just so happens that you can see it around us, but maybe in between galaxies you're saying where there's some.

less stuff, maybe that's when you would see it. Yeah, exactly. And between galaxies is where you need to explain how it wakes up and accelerates the expansion of the universe, because really between galaxies and galaxy clusters is where the dark energy is happening. Oh, so you're saying like the scimitron field is a force, and maybe it's the force that's accelerating the expansion of the universe. Loosely speaking, that's accurate.

We can't really think of it as a force because gravity isn't a force. It doesn't generate measurable acceleration in that way. So you can't do like F equals MA for things generated by gravity. And this is something generated by general relativity. And so it is sort of like a modification of gravity. But loosely speaking, you can think of it as like an effective force. We would see it as a force the way we see gravity as a force in our measurements. Meaning it's not really pushing that the galaxies to move away from us.

It's just kind of like acting there to create more space between us. Yeah, exactly. All right. So then how could we prove whether the symmetron field? exist or not. Yeah, it seems difficult because it's very conveniently impossible to detect this thing within the galaxy, which is where we live, right? But there's a recent paper where people were speculating about mimicking the environment outside the galaxy by creating very low density experiments. Essentially try to do an experiment inside a vacuum, low density, where you could see

this force in action where you could detect the symmetron field at work. Whoa, well, so let me picture this experiment you create a chamber like a box you suck out all the air to create a vacuum and if this symmetry on field exists it would maybe cause the space inside the box to expand we get bigger in principle yes your box would get bigger but remember that dark energy is really a tiny effect over short distances like fractionally speaking it's very very small it's only really measurable over very very large distances like between galaxies so you'd never be be able to measure the box getting bigger, though I love that idea. Would the box be bigger or would the space inside of it get bigger, but then it will go through

the box? Well, then you have a philosophical question of what's the difference, right? If there's more space inside the box, isn't the box bigger? No, I mean, like the space that the box is in gets bigger, but the box remains the same. Well, I think the space inside the box would get bigger, though the box would remain the same. But what do you mean by the space inside the box gets bigger? you mean you measure the distance from one side of the box to the other, that would definitely grow. But this isn't the experiment they're proposing. That's impossible to measure. You could never

measure that tiny growth of space. Yeah, let's stick to only things that are possible. Sure. Go. They've come up with a way to detect the symmetry field inside that vacuum. Okay. How do they do that? Or how do they propose to do that? They propose to do it basically by doing very, very precise tests of gravity. If this symmetry field exists. It's like a distortion of how gravity works. And so do very precise tests of gravity. Take two masses, bring them closer together and further apart, measure the forces on them very precisely and see if you see any deviation from general relativity without the symmetry. That's very, very tricky to do because gravity is very, very weak, right? It's like 10 to 30 times

weaker than any other force. So these experiments have to be super duper precise. But we have some techniques to do them. So you can do this experiment. You can do this experiment. And people have been interested in deviations from gravitational predictions over small distances for a few decades because there are other theories that predict that also. Like if there are extra dimensions to space and time more than just the three we know about, then gravity would work differently. But maybe those dimensions are really, really small. So a lot of these experiments were motivated by looking to see if gravity changed when things got within like a millimeter or a centimeter apart. And until 20 or 30 years ago, nobody knew the answer to that because we could only really do gravitational measurements on like planets and stuff interacting with planets.

Two rocks pull on each other with gravity, but it's very difficult to measure. So people came up with these ingenious devices to measure gravity on short distance scales. They're basically souped up versions of the original torsion pendulums that we talked about once in the podcast for how people would measure the gravitational constant. In this case, you have two rotating disks and the disks have holes drilled inside of this. them and you rotate one of the disks and let the other one free, then you measure how the free disc is pulled by the rotating disc. Because if gravity is strong, then it'll try to line up those two disks to line up the places where there's more mass and line up the places where there isn't as much mass. So if you slowly rotate one of these disks and measure the rotation

of the other disc, you can measure the force of gravity between these two objects that are just like kilograms of mass. Sounds a bit complicated. So maybe let's dig into the details of this experiment and how it might or might not show the existence of the simetron field and what it could mean for our theory of the universe and the future employment of all physicists. So let's dig into that. But first, let's take another quick break. Parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal.

Apparently, the explosion actually impelled metal glass. The injured were being loaded into ambulances. Just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and order criminal justice system is back. In season two, we're turning our focus to a threat that hides in plain sight. That's harder to predict and even harder to stop.

Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Oh, wait a minute, Sam. her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone.

Now, hold up. Isn't that against school policy? That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet.

So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. I had this, like, overwhelming sensation that I had to call her right then. And I just hit call, said, you know, hey, I'm Jacob Schick. I'm the CEO of One Tribe Foundation. And I just wanted to call on and let her know there's a lot of people battling some of the very same things. you're battling, and there is help out there. The Good Stuff Podcast, season two, takes a deep look into One Tribe Foundation, a non-profit

fighting suicide in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission. I was married to a combat army veteran, and he actually took his own life to suicide. One Tribe saved my life twice. There's a lot of love that flows through this place, and it's sincere. Now it's a personal mission. Don't have to go to any more funerals, you know.

I got blown up on a React mission. I ended up having amputation below the knee of my right leg and the traumatic brain injury because I landed on my head. Welcome to Season 2 of The Good Stuff. Listen to the Good Stuff podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Your entire identity has been fabricated. Your beloved brother goes missing without a trace. You discover the depths of your mother's illness, the way it has echoed and reverberated throughout your life, impacting your very legacy. Hi, I'm Danny Shapiro, and these are just a few of the profound and powerful stories

I'll be mining on our 12th season of Family Secrets. With over 37 million downloads, we continue to be moved and inspired by our guests and their courageously told stories. I can't wait to share 10 powerful new episodes with you, stories of tangled up identities, concealed truths, and the way in which Family Secrets almost always need to be told. I hope you'll join me and my extraordinary guests for this new season of Family Secrets. Listen to Family Secrets Season 12 on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. All right, we are inventing fields left and right here to try to explain the expansion of the universe, which is pretty inexplicable.

The universe is getting bigger and bigger, faster and faster. We're trying to come up with an idea. Physicists have come up with the idea of a scimitron field to try to explain it. But Daniel, you're saying it requires us to measure gravity at a really, really tiny small scale, which I always thought, because you've said it several times, is that it's almost impossible. It's difficult. It requires real experimental bravado to figure out how to remove sources of vibration and anything else that might influence your experiment.

In principle, these effects are happening all the time, right in front of you. They're just drowned down by other much bigger effects. And so in order to reveal them, you need to remove those effects. It's like if somebody's whispering the secrets of the universe, but really, really quietly, and you can't hear it because your neighbor is pumping some crazy death metal. In order to hear it, you have to isolate yourself from all that noise. So in the same way, these experiments are set up really cleverly, sort of similarly to how LIGO is done

to be isolated from everything else so that you're measuring the right thing, this tiny little effect that you're looking for, and not being drowned out by the other much bigger effects that are more common. Okay, so then you're saying that to maybe discover whether the symmetron field exists or not, we're going to take two disks,

we're going to place them facing each other really close together, but not touching. We're going to spin one of them, and I guess these disks are not perfectly symmetrical, right? You're saying that maybe they have like a weight on either side or something. For example, yeah. And so if you twist one of them, does the gravity from that twisting disk make the other disc twist as well? And the answer to that is definitely yes. And the question is by how much?

Wait, what do I mean? It's definitely yes. But the other disc can't be symmetrical then. Neither of them are totally symmetrical. You could think of them as like, you know, rods with masses on the ends. In practice, what they actually do is disks with holes drilled out of them. But either way, it's not totally symmetrical. And so gravity will pull on them to try to align them. Right. And you have to kind of rule out the effects. Any other effects that might be,

like maybe the static electricity between the two plates or maybe the VanderWalt forces maybe. Exactly. Or the tides of the moon or anything, right? Everything else is basically bigger than this. You have to remove every possible other effect. And then you want to bring them closer and closer and closer so you can see how gravity varies with distance.

Because one big clue is to see if we understand how gravity gets weaker and stronger as the distances get larger or smaller. Because that's a crucial prediction of both Newton's and Einstein's theories of gravity. Right, because famously, like, the force of gravity between, like, the Earth and the Moon, is equal to the mass of the Earth times the mass of the moon, divided by the square of the distance between the two things, right? Mm-hmm. Exactly.

The square of the distance, or is it maybe more like the square point two of the distance? Yeah, exactly. Or maybe does it change when you get down to really small scales? Exactly. Any deviation from the classical prediction means something new has happened. And gravity works differently, which could be the symmetry field. In this paper, they predict that if you get these two disks really, really close to each other, like tens of microns apart from each other,

then you could be able to detect the effect of the symmetry field. In what way? Like, how does the symmetry field change gravity? The answer to that is very unsatisfying because there's actually lots of versions. of the symmetron field. And so you can get lots of different kind of deviations. So basically any deviation from this, you could explain using the symmetron field. Wait, meaning like if you find that the actually gravity works as the distance squared point two,

then you're saying like the point two, that's the symmetron. Yeah, exactly. The summitron feels like a category of theories with a bunch of knobs and parameters. And if you find some deviation, then you can explain it in terms of the symmetry field in almost every sense. Couldn't we just be wrong about gravity? Why does it have to be a symmetron? Yeah, we could just be wrong about gravity.

And that's one thing people are looking at, right? And the answer could be that we're wrong in some other way, that we're wrong about the assumption that space has three dimensions or we're wrong about how gravity works over short distances. General relativity breaks down. This is just an effort to explain it in terms of general relativity. Because if you find this and you measure a certain value, then it also explains the accelerating expansion of the universe.

So that would be kind of cool. But it wouldn't prove or disprove the symmetron. I feel like you're saying it could be anything. Yeah, lots of theories in particle physics have that problem, like supersymmetry, can predict almost anything. So you find some new particle. Can you explain it using supersymmetry? Yeah. Does it mean it's supersymmetry?

No, but it's still some new particle. So in this case, you find some deviation from gravity. If you've ruled out like experimental effects and you know gravity is working differently, then yeah, either space is different from what you expected or general relativity is broken or general relativity is broken or generally. relativity isn't broken and space has three dimensions and there's some new bit added to it like the symmetry field. There's always going to be a variety of explanations. But hey, we'd be happy to be in that situation of trying to understand some weird deviation of gravity. I see. So like if you find a deviation, maybe a symmetry is the reason, but maybe not. And so this is just this experiment you just described. It isn't to prove the symmetry. It's just to poke holes at gravity. It's to poke holes at

gravity. This experiment is interesting in the context of symmetrons because until recently we haven't thought that any of these kinds of theories that have like variable additions to Einstein's equations could be tested at all because all of them basically disappeared within the galaxy. So this is a cool way to say, oh look, this is one we can actually test. You're right, it's not conclusive. But there are other ways we could also test the symmetry field, not just in these laboratory experiments of gravity. So there might be ways that we could discover it in different contexts so that it pulls together into a coherent idea. But I guess, you know, if you put these disks closer and closer together, aren't you then violating this cluge that you made about the symmetry that it has to exist

and it only exists in empty space? Yeah, that does get tricky. It gets tricky experimentally because having disks rotating really, really close together like 50 or 10 microns is hard. And it also breaks down this assumption of low density. So then you have to make these things lighter. You have to make them smaller and smaller. So then you're playing this game of because you're bringing them closer together, which makes gravity stronger, and then you're removing mass to maintain the low density threshold, which makes gravity weaker. All right. So stay tuned, I guess, is the answer here.

Are they actually doing this experiment? Have they found anything yet? People are doing this experiment. It's a whole successive generations of these at the University of Washington, where people started out. They could test gravity at centimeter scales and then millimeter scales. Now they're pushing down even further, just like a whole series of graduate students, each coming up with some new clever way to make it slightly more sensitive.

And over decades, it's really establishing the frontier. And what have they found so far? That gravity does work as the distance squared or maybe not? Oh, yeah. So far, they found exactly zero deviations from Einstein's gravity. Now, we'd be talking about the Nobel Prize if somebody found a deviation from general relativity. So far, it perfectly confirms GR.

So like the 20 years of PhD thesis all with the same title, Einstein was right. Einstein still right. Einstein was right. Kama, sigh. Einstein's still going strong. Yeah. No, that's true.

We keep confirming Einstein. We keep hoping to see a deviation, not because we don't like the guy, but because a deviation from the theory is an opportunity to learn something. It gives theorists an opening to add new bells and whistles to the theory that might also correspond

to bells and whistles in the universe. All right, well, let's talk about that then. Like, if we do discover the symmetry and the symmetry field, what would that mean? about our understanding of the universe. It would mean that general relativity is still right. Einstein was right, but that there's this term we have to add to his equations.

That the universe has more than just mass and energy density, that there's something else going on, this weird symmetry that changes how the universe grows. It's like a new conception of gravity. Wait, I thought you said gravity would stay the same. It's just that we have this new thing called the symmetry field. Yeah, you don't have to overthrow general relativity. The symmetry plays nicely with general relativity.

field plays nicely with general relativity, but it does change how the universe expands. It would explain basically why that expansion is accelerating. Because the simetron is the force that would be pushing the universe to get bigger and bigger. Yeah, the symmetry is that field which enters in Einstein's equations, which generates this accelerating expansion of the universe. And that's more satisfying than the constant explanation. That would be more satisfying than the constant because the constant is totally unexplained. The only explanation for the constant is, that's just the number, eat it. That's all. There's really nothing there. As opposed to, that's just the symmetron, eat it. Well, the symmetron gives us a handle. We can ask more questions about it.

Like, why this symmetryon field? Why does it have these numbers in it? Where does it come from? How early in the universe did it appear? It gives us something to ask about. You know, it's more specific. Like, who came up with that name? Come on. Tisk, tisk. Not me. That's for sure. you wish it had been you maybe i wish it had been me okay finally i admit yes yes all right well um what else does it say about the universe and how it's expanding it could actually have impacts on the way that galaxies form we see galaxies forming an ellipses and galaxies forming in the early universe as the symmetron field was created and then cooled it could have broken its symmetry in different ways between different galaxies creating these like barriers between them

And those barriers might create like effectively walls between galaxies that are invisible that could affect how galaxies form. And so there's this other prediction that if a Cimetron field is there, you could explain why we tend to see fewer satellite galaxies than we expect. So there are predictions we can make inside our laboratories and also out deep within galaxies. And it could just give us another insight into how the universe works. Like what else invisible is out there shaping our universe? Wow. Because the mysteries aren't just in the expansion of the universe. it's also sort of like how the universe ended up the way it is.

Yeah, there's lots of open questions about the universe. And, you know, physicists just like listeners like to tie them together. Ooh, what if this mystery is explained by that mystery and I can simultaneously solve a couple of open problems? That's really a juicy idea. Yeah, like what if you're missing cookies? We're taken by a new particle called the Pikachu Tron. Done.

Noble prize. Boom, cookie prize. Give me tenure. All right. another interesting idea in the field of physics and particle physics that has consequences not just at the microscopic level, but maybe at the biggest level of them all, the entire universe, how it came to be, and what keeps it growing bigger and bigger? And if this whole process of theoretical physicists inventing crazy bells and whistles to add to the universe seems a little out of hand or bonkers to you, then don't take that as criticism.

Take it as inspiration to think of your own crazy ideas about the universe. You're in good company. Yeah, I mean, I'm a cartoonist. I think of crazy things all the time. Well, you have a PhD in podcast physics, so. Yeah, that's right. It's not a PhD, it's a POD. I have a POD in podcast physics.

All right, well, we hope you enjoyed that. Thanks for joining us. See you next time. For more science and curiosity, come find us on social media where we answer questions and post videos. We're on Twitter. Discord, Insta, and now TikTok. Thanks for listening, and remember that Daniel and Jorge

Explain the Universe is a production of IHeartRadio. For more podcasts from IHeartRadio, visit the IHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. December 29th, 1975, LaGuardia Airport. The Holiday Rush. luggage, kids gripping their new Christmas toys. Then everything changed. There's been a bombing at the TWA terminal. Just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, terrorism. Listen to the new season of Law and Order

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Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. I'm Dr. Scott Barry Kaufman, host of the secretary. psychology podcast. Here's a clip from an upcoming conversation about how to be a better you. When you think about emotion regulation, you're not going to choose an adaptive strategy which is more effortful to use unless you think there's a good outcome. Avoidance is easier. Ignoring is easier. Denials easier. Complex problem solving takes effort. Listen to the psychology podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. This is an IHeart podcast.

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