Daniel and Jorge Explain the UniverseDaniel and Jorge talk about the result of the g-2 experiment at Fermilab and what it means!
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Hey ho, or Hey do you know what today is?
Wednesday?
It's Wednesday, April seventh. Today is like Christmas for particle physicists.
Really, but what if you don't celebrate Christmas.
Well, then it's like Christmas and Hanukkah and Valentine's Day and your birthday all ruled into one.
Nice. Does that mean all particle physicists get a special box of chocolates today?
Kind of? Today's a day we find out the answer to a question we've been waiting twenty years for.
Does that mean the chocolates are twenty years old too?
Lit's is told that particles and chocolates age like fine wine.
I am Poorham, a cartoonists and the creator of PhD comics.
Hi, I'm Daniel. I'm a particle, yes, and I like my chocolates nice and.
Fresh, really fresh off the cocoa tree.
I've actually had cocoa beans themselves. They're pretty intense but tasty.
It's chocolate the universe, and so Welcome to our podcast Daniel and Jorge Explain the Universe, a production of iHeartRadio.
In which we take a bite out of everything in the universe. We sample the flavors of quarks. We talk about the size and the speed of black holes. We talk about how the universe got to be this way and the way it will look in a billion or a trillion or a gazillion years. We have ambitions to take the entire universe and explain every little bit of it to.
You, because there is a lot to understand and to learn about the universe, and the scientists are currently added trying to explore what things are made out of and what things can be made out of.
That's right.
When we're not taking a break to do a podcast, we are trying to unravel the nature of the universe by figuring out what are the smallest bits of it, how do those bits fit together, what are the patterns of those bits, and are there more bits we haven't found yet.
Yeah, because there has been a lot of progress in physics and particle physics and understanding what matter and the forces are all made out of in this universe, but it's sort of an ongoing effort. There are still nooks and crannies and corners we haven't explored, and possibly big areas of physics that still remain totally unknown.
Job security for particle physicists. More nooks and crannies to explore. But no, you're absolutely right. We have found out a lot about the subatomic nature of matter, but there are still lots of questions we don't know the answer to and that tells us that there's probably a lot going on that we don't have any clue about. We don't know if we figured it out like most of the puzzle and we have a few details to wrap up, or if we're just looking at the tip of the particle iceberg.
But then what is that iceberg made out of tenure? And what does it float on? It's all questions embedded in questions.
It floats on a sea of confusion.
Yeah, and a lot of cartoonists are probably drowning in the scene there. But it is a pretty excit time to be in physics. There are a lot of interesting results lately and coming out of the physics community, and so recently there was another big announcement.
Yeah, that's right. We've had this mystery that's been sort of outstanding for twenty years, the result of an experiment that was quite surprising that didn't agree with our theoretical calculations. It suggested that maybe something new was going on, maybe was being influenced by some other kind of particle or force, so we hadn't yet discovered but it wasn't really precise enough for us to know for sure. For us to hang our hats on. So people built a bigger, better, stronger, faster experiment to make a more precise measurement, and those were the results that were just recently revealed.
Yeah, and so today on the podcast, we'll be talking about did Fermilab just discover a new particle?
Whatever Fermi Lab just discovered. They definitely figured out how to trigger a lot of science headlines.
Oh yeah, was this pretty big in the press.
This was everywhere. I don't think there's been a science event recently that triggered as many emails from listeners saying, what is this? Explain this to us, what's going on? I need to understand.
It was everywhere I saw. I was on the front page of the New York Times and people were tweeting about it. So it's kind of an interesting and maybe significant result in physics.
And for me, it was fascinating to see the sort of variety of headlines that people took. Like the New York Times was pretty stately and understated about it, but other places, like Vice, they had a headline that reads government physics experiments suggests something unknown is influencing reality.
Well, that sounds like a pretty good plot for a movie. And I think it's technically true, isn't it. You know, it's an interesting choice of vocabulary, but it is technically every ward in that headline is true government physics experiment suggests something unknown is influencing reality. There you go.
You know, I can fact check it. It's definitely accurate. It was done by government physicists, and there is something out there influencing that experiment. I don't know about all of reality, but it's definitely true with so kudos to that headline writer. They definitely took this sort of like movie trailer approach to writing that headline.
And I have they added government physics experiment? Like, first of all, are there non government physics experiments?
Not many?
Second of all, it just makes it more sinister, doesn't it.
No, I don't know they're going for sinister or like authoritative. You know, this is not your friend Joe's physics experiment. This is like people in lab coats getting salaries. You know, you should believe this.
Does Joe really have any friends? Let's be honest. I think they're going for sinister, you know, like the government is trying to do something crazy.
Oh man, I just totally misread this one. I thought it was like, trust us, we discovered something crazy, but instead you're suggesting it's like government about to build doomsday device that will ruin your weekend.
I think that reveals your attitude towards government an you you're like trusting of the government more government.
Hey, I'm a government physicist, so you know.
I see you're one of them. Do you wear like, you know, sunglasses with your lab coats and everything?
Only when I'm trying to influence reality, which is basically all the time. Since I'm part of reality, this podcast is influencing reality.
Is it though? Ors just sound ways in the air.
Daniel, Unless you think our listeners aren't part of reality.
You know, hopefully they're real, but we don't have to be real.
You know, this podcast is generated by an algorithm, a government physics algorithms.
It's unreal. Anyways, it was a pretty big result that a lot of impress out there about it, and I have to admit, Daniel, I didn't know about this weeks before the actual announcement.
Oh wow, is that because you have a link into like the secret science results?
Kind of? I was commissioned to make a comic about it by a journal and so they sent me the secret paper a weeks ago, saying you can't share it with anybody?
Are you telling me you knew this answered one of the biggest questions in particle physics for weeks and didn't tell me.
I sworn of secrecy, Daniel. They would have revoked my cartoonist license. Oh if I've had told anyone. Plus also they're like, they gave me the paper and they're like, you can't tell anyone what it says. I can't even read this paper. I wouldn't be able to tell you tell anyone.
But my friend Daniel could read this paper. All right, Well, I admire your integrity.
Yeah, thank you. At least you admire something about me. But it was a pretty exciting thing in the physics community. And let's talk about whether or not it lives up to the high business, really something that might influence our view of reality or is it sort of another incremental result in the physics endeavor of humans?
Yeah?
Well, you know, it's an important moment in particle physics because we have been desperate for a discovery for quite a long time. You know, I would say decades. We have known for a long time that our theory isn't correct, that isn't complete. At least it can't be the final answer because there's so many unanswered questions in it, so many parts of our theory which just seems sort of like ad hoc or put in by hand or unexplained. So we've been casting about for a new discovery to give us a clue as to how to change our theory or what the new vision of physics should be, and the main strategy for doing that has been things like building big particles accelerators to trying to make new particles that we can add to our table and like give us a sense of the larger patterns. But that's been coming up kind of dry. We haven't found anything at the Large Hadron collider other than the Higgs boson, which we already believed existed. So now we're sort of like looking under every rock. Is there any experiment out there that can find something new? Is there any measurement government physicists can do to find some discrepancy between our theory and nature, because we need that kind of discrepancy in order to find something new. So that's why this experiment is sort of like one of the last best hopes for particle physics, that we can figure out something new, find a clue that reveals a new idea about the nature of reality.
I guess for some of our listeners who maybe we did not see the headlines, let's just talk about the announcement. So this was an announcement coming out of Fermi Lab, which is a particle physics laboratory outside of Chicago, and they've been around for forever, but recently they announced that some new results regarding the muon, which is a particle, right.
That's right, So you're familiar with the electron. It's part of you at orbits, all your atoms. The electron has a heavy cousin. It's much heavier than the electron, but it's otherwise totally identical. And the very existence of the muon is sort of a mystery, like why do we even have a muon? We don't know, but it's like this copy of the electron, and it's a good place to do precision measurements to try to like see if there's anything weird going on because the muon has this little magnetic field. That magnetic field is very sensitive to the stuff going on all around the muon.
Yeah, so they've been studying this particle for a long time, and they just did a new measurement of its magnetic moment and the results are what's kind of interesting with regards to what it means for our view of the eaters.
That's right, And you might be wondering, like, why does a muon have a magnetic field? How does that even work? Well, remember, a muon is this tiny fundamental particle. I don't really know if it's made of anything smaller. We sort of imagine it to be a tiny little dot. But even though it's a tiny little dot, we also think it has this thing called quantum spin, which means that in theory, it has some angular momentum. Because it has electric charge and angular momentum, that means it has a little magnetic field. And that magnetic field is a really nice way to probe what the particle is doing as it flies through space. Is it just flying through space or does it also shoot off other particles briefly? And if it does shoot off other particles, then even though these are virtual particles that only exist for a fraction of a second, they can change the way the muon's magnetic field works. And it's sort of a great way to figure out what kinds of particles can exist, what's out there on nature's menu. Because it's quantum mechanical, every kind of particle that can be shot off the muon will be created and influence the muon's magnetic field. So don't think of the particles out there waiting for the muon. They are like possible particles that the muon briefly creates as it flies. If you like fields instead of particles, then another equivalent way to think about it is that the muon is flying through a bunch of quantum fields and its energy can slide briefly into those fields and then come back. Since that influences the muon's magnetic direction, you can tell when it happens, which gives you a clue if there are fields and particles you don't know about. And so what they do is they take this muon and they spin it in a certain direction so they know the way it's going, sort of like a gyroscope, and then they send it around in a circle a bunch of times until it decays into an electron. Because muons don't actually last very long. They're unstable particles, and based on the direction the electron came out, they can tell how the muon was spinning. So now they know how the muon spin changed from when they created it to when it decayed, and that tells them, basically how all the other little particles out there were pushing on the magnetic field of the muon, which tells you something about what particles are out there.
They're measuring this magnetic field of a muon, and I guess maybe a more basic question is like why do particles have magnetic fields?
Isn't that weird? Like are particles little magnets? Yeah, it's kind of weird because you think of little particles as these little dots, and you know they have like spin and charge and mass and stuff. But anything that has spin, quantum spin and has electric charge also has a little magnetic field because remember that's where magnetic fields come from, Like the magnetic field of your piece of iron comes from electrons spinning inside of it, and so muons also spin, so they also have a small little magnetic field.
So then I guess the next question is why is this magnetic field of this little particle important? And what could it tell us about other particles that could be out there?
It's really important because the magnetic field tells us about the other particles that are out there, because the magnetic field allows the muon to sort of interact with those particles. As the muon is flying along, then the magnetic field gets sort of touched by all the other particles that are out there. Example, like this magnetic field is carried by photons, so the way that magnetic field information is transmitted is through photons. So a muon can be flying along and it can like pop off a little photon and then reabsorb it, and it could pop off a photon and that photon can interact with other particles that can come out of the vacuum, you know, like pairs of electrons and positrons or any other particle out there, and then get reabsorbed. So sort of what happens to that photon when it gets shot off the muon and then reabsorbed can influence the magnetic field of the muon and also can tell you about the other particles that are out there that can talk to this magnetic field. And remember that by particles out there, we don't mean particles that are already existing and are hanging out waiting for the muon, but possible particles on nature's menu that can be created from the muon's energy. That's what we're looking to explore.
Oh, I see you sort of like the begnetic field of the muon as kind of an antenna almost, like you use it to see how it gets influenced by other particles that are out there in the.
Universe exactly just like an antenna, because all those other particles also can sort of like talk magnetic language to the muon. And if you watch really carefully how the muon is spinning in the direction of its magnetic field, you can tell the signals that it's picking up from those other particles. And it's sort of like a gyroscope. You know, you start a gyroscope spinning, it should keep spinning the same way unless something applies force to it, you know, give it a little push or a little twist or something. If you've got a muon spinning and you know the direction of its magnetic field, you can watch as that magnetic field changes and you can measure the influence of all the particles around it.
Cool. So then that's what this experiment did, is that it's basically like a large tunnel or ring or like a tube, and you have these muons flying around and you're sort of measuring how they get knocked around by the universe, basically, how their little magnetic field gets tweaked by you know, what could possibly be out there in the universe.
Yeah, it's a circle. So the muons go around in this ring and as they go around, they get tweaked by all these particles. And it's a really cool way to try to find something new without knowing what's out there. Anything that interacts with the muon's magnetic field will can give a little effect. So you add up all the different kinds of particles that can give an effect and you get like an overall number. You can compare that to what we calculate from our theory, where we add up the effects of all the particles we know about, and we can compare what nature is doing with all the real particles to what our calculations are doing, you know, with all the particles we know about, and that can give us a clue if there's any particles missing from our list.
Cool. Yeah, you use it sort of like a metal detector, kind of like you're sensing what's out there and if you think you know what's out there, then you should be able to predict what this little antenna will tell you. But if there are new things out there, this this antenna will not do what you expected to do.
Yeah, and the differences are very very small. People have been calculating this stuff for decades and been measuring for decades, and mostly things agree. But if you measure it really, really precisely, then you can see the influence of like very rare, potentially new heavy particles. So we're talking about one of the most precisely known and most precisely measured quantities in all of physics. And the more precise we can make it, the better a test we can do to see if there are any particles out there that we might be missing.
I guess you're looking super closely to see if this little antenna, you know, deviates from your theory, because if it debates from your theory, that means your theory is not complete or there's new things out there.
Yeah, And the experimental challenge is getting all the other sources of uncertainty out of the way, any other transient magnetic fields, or knowing exactly how you started this muon or making sure nothing else is influencing it. It's a lot of work to set this experiment up and make it super duper precise. It's like lots of other experiments like the gravitational wave experiment, where they spent decades figuring out how they get those mirrors to balance and be really really quiet. There's a lot of just sort of like careful work in setting up an experiment like this, And there's also a lot of careful work in doing the calculation and making sure or you're correctly accounting for all the particles that we do know. So it's like a huge project. It's not just like, hey, I have this idea, let's go check this out tomorrow afternoon. You know, this takes decades to design and to organize and like really iron out all the wrinkles.
Right. You get to wait for the chocolate to you know, age, and you get to wait for everyone to sign the Valentine's Day card, and it just takes a long time. All right, Well, let's get into the theory of this experiment and also the experiment, and how those two are not quite the same and what that means for our understanding of the universe. But first, let's take a quick break.
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All right, we're talking about fermilabs recent announcement of a new interesting result regarding the muon, which is one of the fundamental particles, and they measured something about it and they predicted something about it, and it's not quite the same Daniels. So maybe step us through what some of the theory calculations are and what they're actually calculating.
So what they're trying to do is understand what happens when a muon is flying through space. And this is a quantum mechanical particle, and so you have to consider not just like the boring option that a muon just like flies through space and does nothing, but all the other possibilities. For example, a muon might also fly through space but emit a photon and then reabsorb that photon. That's one possibility that's not very unlikely. We think the particles are doing that all the time, And like we talked about in the episode about renormalization and like what's the electron's actual charge, what we measure is sort of like the combination of all the possibilities that the muon can do all at once. We don't just ever measure like a single particle doing one thing. So this kind of stuff is happening all the time. There's lots of different things the muon can be doing when it goes from A to B, and we try to consider like all those possibilities. So possibility one is just going a straight line. Possibility two is emit just a single particle and then reabsorb it. Possibility three is emit two particles and reabsorb them. Possibility four is emit a photon and then that photon turns into two other particles, which then collapse back into a photon and then get reabsorbed by the muon, and you can imagine how it's easy to imagine lots and lots of different scenarios for what can happen for a muon when it goes from A to B, and all those scenarios affect the muon's magnetic moment just the same way all these kind of quantum interactions with the vacuum affect the electrons charge or it's mass. This is all part of like what makes the muon. So when you're calculating the overall magnetic moment of the muon, you need to account for all the things that it could be doing, including these little brief interactions it has where it interacts with magnetic fields and creates other particles.
Right, So, I guess it's kind of this idea that a particle isn't just like a particle like alone in the universe. It's like it's constantly doing stuff, doing quantum mechanical stuff. It's it's constantly you know, maybe popping off other particles and then reabsorbing them, and it's not just like sitting there and doing nothing.
Yeah, there's this difference between like the bare particle, which is sort of the simplest concept you can have in theory, then the actual particle in reality, which is part of the universe and interacting with all these quantum fields around it. And that's sort of like the thing we measured, the thing we observe. So the bare particle really only sort of exists in our minds like a single isolated particle doing nothing. In reality, these particles are constantly buzzing with all sorts of other virtual particles. And that's really what the muon is. Don't think of it like a muon surrounded by a cloud of other particles. The muon is that whole cloud. It's got like a bare particle at its core, but the whole thing together is the muon, And so it's sort of part of what the muon is is to have this cloud of other particles all part of it.
Yeah, and it's kind of like a quantum mechanical cloud of other particles it's constantly making, right, Like, it's not just the bear particle. It's also at the same time simultaneously existing as all these other sort of with all of these other particles that are created and virtually exists for tiny moments of time.
Yeah, And I think to quibble on the quantum mechanics of it. It's not really true that they all simultaneously exist, but that the possibilities of them all exist. And so there's a superposition of all those wave functions for the particle to be doing this or for the particle to be doing that, and if you're not measuring it, then all those options can exist at the same time. It doesn't really have a philosophical meaning to say, like they all actually do exist, but you know, that's a whole other digression. We can talk about quantum wave functions another time.
So it's kind of like the cat, Like the cat is both live and dead and that so that it's usually put, and so the meon is both alone and also has all these other friends around it.
Yeah, well you might not be surprised to hear that I have an objection to how it's usually put. I would say the cat is a possibility of being alive and a possibility being dead. I don't know what it means for it to be alive and dead at the same time. That's the whole idea of classical physics that somehow these wave functions do collapse before we measure them. But in this case, there's an infinite number of things that muon can do, and the more particles you add, the more options, the more times like a particle emits another photon or turns into something else, the less likely those things are. So the most likely thing to happen is that the muan just sort of like goes for A to B and then you can add a correction to that by adding one particle. You can add another correction to that by adding two particles. If you want to get like a rough idea, you just need to do a few these calculations. If you want to get it like really really accurately, then you need to sum over like thousands and thousands of these different possibilities.
It's kind of like these are all different possibilities of what it can do, but somehow they all effect it's magnetic field. And so like if you know, like it could do ABC and D, you can add up ABC and D and to get sort of like what the theory predicts what the magnetic field demeon is going to be?
Right, that's right, And we use something called perturbation theory, which tells us that like we do the biggest contributions first, and then the more ones that we add sort of we're just refining the smaller and smaller decimal places. So it's not like when we get to diagram number forty seven thousand, we're going to find something that totally changes the answer in the first decimal place. As we add diagrams that are more and more complex, we're getting smaller and smaller corrections, and so we're sort of like asymptotically approaching what we think is the true value. But these calculations get harder and harder because the later diagrams have more particles, and they have loops, and they have crazy stuff, and most importantly, some of these create particles that have the strong nuclear force in them, and those calculations are particularly tricky to do. And that's really at the heart of why this is so hard, right.
And I guess the problem is that the neon is not just doing ABC and D. It's doing like abc D dot dot dot to like you know, infinite number of possibilities, right, Like it's almost like a fractal I think it's like it can be turned into a photon and then but then the photon can turn into two things, and then those two things could turn into other things, and you know, the effects get smaller, but like the possibilities are endless, right.
Yeah, And there's a really interesting question there, like is it really have an infinite number of possibilities or is it just the way that we are organizing in our minds requires an infinite number of ideas because in reality there's just a number. Like nature doesn't do an infinite number of calculations every time a muon goes from A to B. It just does its thing. So it could be like that our mathematics isn't expressed in a way that makes this kind of idea simple and compact. Or it could be that there really are an infinite number of things possibly going on there, we just don't know. It's a really fun philosophical question. Philosophy.
Yeah, we need a longer podcast for them, all Right, So you can sort of predict what the mio sponetic field is supposed to be from all these other like virtual articles, and then you can also go out and measure the magnetic field using an experiment exactly.
And that's what they did like twenty years ago at Brookhaven. They did this experiment where they line up a bunch of muons, they get them all spinning in the right direction and then they shoot them into their machine which zips them around in a circle using a big magnetic field. So they built this really big, very precise, very expensive magnet and they did this measurement. This is twenty years ago at Brookhaven, and they found that the answer didn't really agree with their theoretical calculations. And that's sort of what set up what we're doing today because people were wondering about, like, why doesn't this agree. So they decided they needed to do another experiment. They need to get more data, they need to like, you know, refine this answer. So they actually took that same magnet from Bookhaven and they shipped it over to Fermu Lab where they set up a whole new experiment using the same magnet. And they have like much much more data and they've been analyzing that and that's what the announcement was all about.
Do you think they used the regular like US mail or do they fedexit or how does one ship a giant physics magnet?
You just put a lot of stamps on it and you hope that they pick it up. Now there's some great pictures. They had to take it on a boat for a while they have it on this like double wide trailer crawling across the Fermi Lab. It's pretty cool. It's not an easy thing, this ship. It's definitely some additional charges.
And I think the idea is that twenty years ago, like they found that the theory and the experiment are not the same, but it's sort of like borderline, right, Like it was three point five sigma difference, meaning it's like it's different, but it could be still kind of a statistical fluke, right.
Well, it's funny because we do all these things really quantitatively. We're very careful about the number when we're calculating it, and then we're very careful about the theoretical value that we do really quantitative statistics to understand, like what's the probability that these two numbers are actually different versus that we just had like a random fluctuation in our experiment that makes them look different because we don't want to get fooled, but just like having a random fluctuation. So we do all these really careful calculations, and then in the end it's still subjective because three point five sigma tells you, like the probability for this to not have been just a fluctuation, and it says it's pretty small, but it's not convincing, Like particle physicists don't find that level of discovery enough to believe the result. So three point five sigma is kind of impressive, but sort of not enough. So I guess you could call it borderline.
Yeah, it's kind of like flipping a coin and trying to see if it's like a loaded coin and you get seventy or seventy five heads in a row or out of one hundred, and you're like, does that mean that it's a loaded coin or does it mean that I just got lucky and got seventy five heads, Yeah, out of one hundred.
And that's where the subjective element comes in. At what point do you declare this coin is fair? At what point do you declare the coin is not fair? And so in our field, we have this standard of five sigma, which is like one in three and a half million chants of it being a random fluctuation, and so three and a half sigma sounds like it's close to five sigma, but it's a whole Gaussian tail kind of a thing, and so it's actually not that.
Close, all right, So they put these muons inside of a magnetic ring, and they're growing around, they're spinning, and you're sort of measuring also what happens to those muons, right, and of what happens to them tells you the value of the muon's magnetic field.
Yeah, So they get these muons spinning a certain way, they shoot them around in this ring, this big magnet, and the magnet forces the spin to change a little bit, because the spin will change in the presence of a magnetic field. And they zoom around a few hundred times, and only a few hundred times because the muon doesn't live forever. Eventually muon will decay into an electron and a couple of neutrinos. But that's good because that lets you measure the direction of the magnetic field to the end, because the direction of the electron tells you the direction of the muon spin in its magnetic field. So when the muon sort of dies, you can measure how much was its spin affected by this magnetic field, and that tells you what the muon's magnetic field was by itself.
They've spent twenty years sort of refining this experiment just to get more and more precise, and finally we got a number. So now we have two numbers. We have the number that the theories perdiction based on all of the things that demean can do of what this magnetic field should be, and we have a number that experimentalists spent twenty years measuring and they're not the same.
And you know, they did this in a really cool way. They did it in a blind search way because this is a very important number and a lot of sort of careers rely on this. Folks want the number to be interesting. They're hoping it's going to deviate from the theory, but they definitely want to get it right, and so they do this in a blind way by sort of scrambling the data a little bit. They add like a random offset to all of the numbers that's sort of hidden. It's like a hidden key to the data, so they don't bias the way they do the analysis to try to push it in the direction that they maybe subconsciously want. And so they held the key like in a secret office until just six weeks ago. So even the people working on this experiment for the last decade or so didn't know the answer until six weeks ago when they cracked open this key and they typed it in and then they finally saw the answer.
Wow, it sounds like a spy novel, you know, like there's a hidden key and yeah, nobody knew the secret until the very end.
Well, I think it's actually really exciting because it makes it climactic. There's a moment when you're asking Nature a question and you're getting the answer right. Otherwise it sort of creeps up on you and like when you actually learn or here's a correction, or let's change this, and the answer is sort of like evolving as you're improving your techniques. It's nice to have a definitive moment, a crisp time, when you say, Nature, what is the answer to this question? And then you get an answer back from the universe.
All right, Well, they announced this result which everyone got very excited about recently, and so let's talk about what the result was and what it could mean about the universe. But first, let's take another quick break.
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All right. So did a government physics experiment suggests something unknown is influencing reality?
Daniel?
Did shady government physicists distort our understanding of the universe and reality.
I'm trying to influence reality by eating boxes of chocolates. It seems to affect the reality of the size of my being.
Trying to increase your magnetic field or decrease your magnetism.
Just influence my effect on the universe, my personal gravity.
It might be shrinking your magnetism. We'll have to ask your family. Yeah, so they found that the theoretical on the experimental results do vary. They're different as it was sort of suggested twenty years ago, but now we know kind of more for certain.
Yeah, these numbers have improved. Both the theoretical numbers have been improved and the experimental numbers have been improved. So the uncertainties on these two numbers have shrunk, but the gap between them has not. So there's still like this opening between these two numbers. And you know, I'd read this number, but it's sort of crazy. It's just like a very specific number and the differences are in the last couple of digits of the like this twelve digit number. But you know, the scale of it is, like the theoretical value is too ten thousands of one percent smaller than the experimental value. That's like, how precisely we've calculated and measured these quantities.
Wait wait, wait, so then you're saying that the difference between the theoretical and the experimental is two ten thousands of one percent. That's the difference.
Yeah, it's a really tiny difference. So you need really precise experiment and really careful calculations to even be sensus to this. That's why it's so impressive that they can even ask this question.
It's almost like you flip the coin and you got heads, you know, fifty point one times more than you've got tails, And normally that would be like you know, in the noise, but maybe you flip the coin like a gazillion times to know that it like, yeah, there's something a little bit biased about this coin.
That's right, And if you're going to do that measurement, you have to ask, well, do I expect fifty percent I mean, the shape of the heads is not exactly the shape of the tails, and maybe that influences it with the air currents. And you've got to be like really precise about all of those calculations if you want to claim that it's unfair or that it's fair. And so you know, that's what they've done. They've done like a tour to force of these theoretical calculations and the experimental calculations, and so both of these results have changed, Like the experimental result we now have a new number from Fermulab as of yesterday, but also the theoretical results have changed. For example, they found like a mistake at one point where they made up the wrong sign, like they changed a plus to a minus accidentally, and that changed the result. And so they're constantly like improving and doing these things better because neither of these things are easy.
It's a pretty tough thing. Like even the theory that it takes like supercomputers to compute these numbers.
Yeah, well there's actually a big controversy about how to do that theoretical calculation, and some folks are using supercomputers to try to like calculate this thing from scratch out. Of all of these diagrams and include what happens when the hadronic particles that feel the strong force are created out of the vacuum and all this kind of stuff. And there's another group that are trying to just like not do those calculations explicitly, but take them from other measurements, like other experimental results, and extrapolate from there to figure out like what are the bits and pieces and then use theory to sort of glue them together into a measurement. So there's sort of two different approaches to doing this calculation, and there's some controversy there because the sort of traditional approach where we extrapolate from other experimental measurements and use theoretical glue, that's the one that has the discrepancy with the observed value. But there's a new result that uses like pure computation and these crazy supercomputers in Europe, and it actually agrees with the experimental result pretty closely.
All right, But we're talking about this result from Firmulavin. They sort of confirm that it's the theory and the experiment are different, and so you know, assuming that they're right or that it gets further confirmed and all the theory checks out, what could it mean about our model of the universe.
Well, you're right that the fermu Lab experimental result is the new shiny thing, and nobody's suggesting that it's wrong. But it's only interesting and it's only suggestive of new physics if it's different from the prediction. And we have two predictions, one that agrees with the Fermilab result and one that doesn't, and that's what the four point two sigma is. So the picture is a bit cloudy on the theoretical side. As usual, there's a spectrum of possibilities, you know, from like the most boring to the more interesting to the totally crazy and potentially bonkers idea. As you said, the most boring possibility is that it's just a mistake somewhere, you know, maybe one of these theoretical groups has made an error or they've forgotten to include something, or this is a minus sign wrong. You know, this is really really hard. So personally I like this calculation done by the European supercomputers because it was done by the collaboration called BMW, because they're in Budapest, Marseille and Whoopertal, and it's sort of like independent they like start from scratch and they're just doing the calculation, so we'll just have to see what progress is made there in the future. But they're comparing to this same experimental results. So it really is sort of like a blow to this discrepancy to have a new theoretical calculation that doesn't show the discrepancy.
Interesting, So, like they use some supercomputers and they found that there is no discrepancy with the experimental result.
Yeah, the prediction they made, which came out well before the experimental result, is bang on to the new experimental result. So we don't know which of these two theoretical calculations is correct. But sort of muddies the water. It's harder to claim that this discrepancy is the side of new physics, new particles influencing reality when we don't exactly know if it's correct.
All right, So that's the vanilla possibility. What's the chocolate chip possibility?
Chocolate chip is that there are some new particles out there influencing reality. You know, we strongly believe that there must be more particles out there. The story can't be complete. We look at the particles that we've discovered so far in nature and they just don't answer all of our questions, and we suspect that there are lots more really heavy particles out there. The problem with really heavy particles is that it takes a lot of energy to make them. You got to smash particles together at the Large Hadron Collider with enough energy to actually create these things so you can study them and explore them. But if we don't have enough energy in our machines, that doesn't mean those particles don't exist. It just means we can't make them at the Large Hadron Collider, and the only way to study them is to see these little hints. So it's possible that this is a hint of those new particles that are out there that are influencing the Muon's magnetic field because they appear in some of these diagrams some of these calculations that change the Muon's magnetic field. But that doesn't mean we know what they are, right. It's sort of like unspecific. It's like saying we know there's something out there, we just don't know what it is. It's a more indirect way of looking for new particles.
Right, because you're sort of like seeing how they influence other particles, which is not a direct measurement, all right, So then that's the chuckolate chip possibility. Maybe there are new particles or heavier versions of our particles out there, and maybe the meon is going through space and it sometimes creates these heavy particles which kind of tweak its magnetic fas. Right, that's the idea, and.
Then there's some even crazier ideas. People have specific theories for what might be influencing the muon's magnetic field, and these other theories we can test because they're very specific. For example, my friend Dan Hooper at Fermula, he has this idea for a new particle. It's called a Z prime prime because it's sort of like the existing Z particle, but it's different. So it's a little bit of a twist on the Z particles, like the Z particle's evil twins.
Like Z would flare. It's like the Z particles with the littletail or something.
It's a spicy version of the Z particle, and it's sort of like the Z but it would influence the muon's magnetic moment in just this way. Because when the muon is flying along, it doesn't just create photons. Sometimes it creates z's and w's and all sorts of other particles, So it would also create the z prime, and it would explain this discrepancy. But the cool thing about it is that if this z prime is real, it also would have been created in the early universe. It would have changed how the universe expanded, specifically because this z prime, if you create it, would probably decay mostly into these new trino particles, which would boost the energy density of the radiation portion of the universe. And right now, there's a lot of questions about how the universe expanded in the early days. You can check out our podcast about the Hubble tension. In this question of like how fast was the universe expanding, we have all these measurements that again don't agree. So this z prime theory would explain not only the muon's magnetic moment, but also this weird question about the expansion of the universe in its early days. So it's sort of like really nice because it would solve both of these problems at the same time.
That's a new proposed particle, But would it also explain the difference between the theoretical and experimental measurements of the muon.
Absolutely would, Yeah, it would solve both of those problems simultaneously. That doesn't mean that it's real, you know, but it's nice if there's another handle you can have on it. Because remember the muon's medagnetic field is very indirect. It sounds like a clear way to know what's responsible. So what you want to do is have like another way to test this thing. Say, if it really is a Z prime, can I see it somewhere else to confidence that it's a Z prime and not like a G prime or a D prime or some other weird particle. So he has a more specific prediction for another way we can test this particle. But that doesn't mean that it's right.
Could it also be because I've heard in the news and from some of the scientists that you know, this could maybe also point to maybe explaining things like dark matter or why the Higgs boson has them as it has, Like it could maybe even open it up further to like crazy new kinds of other particles.
Yeah, it's harder to know whether it can tell us something about dark matter, because we don't know whether dark matter interacts at all with the muon. It's true that this method can tell us about any particle that will interact with the muon. But it might be that dark matter only feels gravity. Now, the dominant theory of dark matter has a sort of interaction between dark matter and muons and other particles at a very very low level. So for some theories of dark matter, yes, this could explain it, but again, we don't really know what would be doing this. It just tells us there's some new particle out there that does interact at the muon. It doesn't tell us what that is. So dark matter is a favorite idea because it's another big, unexplained mystery.
Well, I think maybe the overall big headline is that maybe what we think can happen in the universe is not what is actually happening in the universe, Like maybe there are things that we haven't accounted for or that maybe makes our theory incomplete. That we are seen in this muon magnetic field that is not in our theory. That's I think that's sort of the general exciting.
Part, right, Yeah, it's always exciting to find a place where our theory does not predict our experiments because it means it's a place to learn, it's a place to improve our theory. It's a place to add something new to our understanding of the universe for a long time. All the experiments we do, like all the ones at the Large Hadron Collider, are very very well predicted by our theory, which means that it's working, which is exciting, but also means there doesn't provide any clues for how to improve it, or expand it, or go to the next level of the theory. So any discrepancy like this is a wonderful clue that points us to maybe figuring out a deeper idea by the nature of the universe. But now let me maybe toss a bit of cold water on that. Remember that this is only exciting if the theory is right, and that's a bit of a fuzzy picture. Still. I actually think the other discrepancy in the b particles with Penguin diagrams at the Large Hadron Collider is much more promising and exciting because the theoretical issues are better controlled, and there are several other experimental results that suggest the same thing. So if I had to put my money on something, I guess that this discrepancy in the Fermulab muans will turn out to be a problem in how the theory calculations were done, not actually a new particle, And I'm more excited that the LEDC Penguin diagrams could be showing us new particles.
So always good to double check, you know, Like if you think this twenty year old chocolate's gonna taste good, maybe you should try it first, right.
Yeah, and you should keep trying it. And that's what they're going to be doing. This is just the first batch of results from this Firmulab experiment. They actually have a lot more data that they've all already taken. It's like on a computer somewhere. They just haven't finished analyzing it. And they have ideas for how to improve the quality of their measurement, to make it more precise, to shrink these errors even on the data they already have analyzed. So we should expect to see sometime in twenty twenty two or twenty twenty three more announcements about even more precise measurements of these quantities, and also progress on the theoretical side, as these two different groups try to figure out like why they're getting different answers and who is correct, and maybe they can learn from each other. So this is a story we should keep following.
Yeah, because this big announcement, as big as it was, it's really just like the first bun out of the oven, right, Like this is like their first batch of data, and they're expecting to get like, you know, twenty sixteen times more you know, Meulon spins detections, and that their estimates are just going to get better.
Yes, absolutely, As they get more data, the statistical uncertainly will fall. And in this case, the statistical uncertainties just from like not having an infinite number of measurements is still a dominant source of uncertainty. As they get more data, they're gonna have to worry about other sources of uncertainty, systematic uncertainties and things about like how they're calibrating their experiment. But again, these are clever experimentalists and they have ways of reducing those things. So as time goes on, all of the uncertainties will shrink and our knowledge of this quantity will improve, and maybe it will reveal something new in the universe influencing reality.
Awesome, like maybe a new flavor of ice cream or that's chocolate. All right, Well, I guess as always the answer is stay tuned. If you're still a little bit confused about this whole topic. You can read the comic that I drew for Physics DAPs Journal at phdcomics dot com. Slash you on m u N and check that out. But 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 iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. When you pop a piece of cheese into your mouth, you're probably not thinking about the environmental impact. But the people in the dairy industry are. That's why they're working hard every day to find new ways to reduce waste, conserve natural resources, and drive down greenhouse gas emissions. House US dairy tackling greenhouse gases. Many farms use anaerobic digestors to turn the methane from manure into renewable energy that can power farms, towns, and electric cars. Visit you as dairy dot COM's Last Sustainability to learn more.
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