Daniel and Jorge Explain the UniverseElectrons can hang out until the end of time. Physicists think that protons should eventually fall apart. But will they?
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Hey, Daniel, I'm worried about how long I'm going to live?
Oh man, aren't we all these dudes?
I know? But I mean, like down to the particle level, Like, are my Jorge electrons going to be around forever?
Well, we actually have good news there. We do think that electrons can live forever. All right, that's cool. What about my protons? M I got some tough news there.
It don't last very long.
Currently we think protons live for only a trillion trillion trillion years.
Well that's good. I guess even my protons are procrastinators.
They are professional protonic procrastinators.
I am morehand a cartoonist and the creator of PhD comics.
Hi, I'm Daniel. I'm a particle physicist, but I might one day decay into something else.
Oh, into a lighter Daniel or a lower energy state.
Unfortunately, I seem to be violating the laws of physics and decaying into a heavier.
Daniel as to all humans.
Unfortunately that seems to be the direction.
But welcome to our podcast Daniel and Jorge Explain the Universe, a production of iHeartRadio.
In which we take the universe and crack it in half and pour all those little explaineons into your brain. We take you on a tour of all the amazing, the massive, the enormous, the crazy, and all the tiny, mysterious, weird quantum stuff of the universe and explain it all to you.
That's right, so it lives in your head, possibly forever. Hopefully you won't forget us. We'll always be there in.
Your brain, because we all know that once you've understood something in physics, you know it forever. I have never forgotten a single thing I've ever learned.
Oh really, it's hard to unlearn.
Huh No, that's exactly the opposite of true. I'm the kind of person that can learn something fairly quickly and then forget it fairly quickly.
I guess, hmmm, does the information decay in your brain? Or it dissipates, or I.
Think it just gets replaced by all the stuff on Twitter that I scroll through and shows it back out the other side of my brain pushes it out the other ear. That's right, information understanding decay.
Yeah, we like to talk about science and the cosmos and the universe and everything in between, and including all the things that are out there and all the things that are not yet out there and all the things that will not be out there in the future.
That's right because everything that you wonder about the universe are the same things that scientists wonder about the universe. Where did it come from, how did it get here? How long will it last? And how long will you last?
Yeah, so big question is how long do particles stay around? Do they live forever or at some point are they not around?
That's right because particles are these weird, fleeting quantum objects, and I don't always obey the same rules that you and I obey that we're familiar with that makes sense to us, and yet we are made out of them. Everything in the universe is made out of particles. So it's essential that we understand how they work and the rules under which they operate. Because they might very well determine our future, even if you have to wait a trillion, trillion trillion years to find out.
Yeah, because we know that, you know, as humans, we don't live forever, at least not yet.
I don't know. I've never died so far.
How about you, I think, probabilistically speaking, you are unlikely to be around for a few hundred years. Yeah, but it's mostly because the arrangement of our particles and our atoms at some point doesn't work, and it dissipates, and our particles go back into the soil and back into dust, And so I think an interesting question is like how long do your particles last? That's right, Like, there are the particles that you're made out of right now? Are they going to be there at the end of the universe?
That's right? Even if that arrangement that makes you isn't around anymore. With that little bit of your fingernail and that tip of your nose, will it be around inside some star and get fused into a piece of gold someday and get blown out into supernova and have trillions and trillions more cycles, or will it only last a few more years and decay into something totally unrecognizable.
Right, because I guess particles come from nothing, right, Like you know, at some point there weren't any particles and then they suddenly sort of pop down. And we know that particles pop into existence all the time in the vacuum. And so but the question is, once you form a particle, does it stay around forever as a particle or or do things happen to it to make it disappear.
Yeah, particles certainly were formed in the very early universe. We had this hot, dense state, all this energy stored in the fields, and then as the universe cooled, that energy sort of isolated into these discrete packets that we now call particles. And we'd like to play this mental game as particle physicists say, you had just one particle in the universe, what would it do? Would it sit there forever or would it eventually spontaneously break into lighter particles? And so that's the game we played with electrons, and we think a single universe filled with just one electron would stay that way forever. But the open question is that also true for protons.
So to the on the podcast will be asking the question do protons live forever?
And if so, how do they plan for their retirements?
Right? Do they have professional protonic retirement accountant?
I hope they've been proactive in saving.
Yeah, I hope that their fee is paraded.
If you live forever, you would have like an infinite number of grandchildren, which I suppose could support you in your old old age.
Oh, there you go, using they still like you after an infinite number of years.
Great great, great great great Grandpap, die already and give us all your stuff.
No, you'd have to go great great for infinity. Nobody wants to call you.
I ran out of time there.
Yeah, all right, So electrons live forever. We know that. That's like fact number one. H they never what does that mean? They never decay or they never like spontaneously disappear.
It's an important distinction. Like an electron, you can destroy it. You throw an electron against a positron, you can turn that energy into something else. You can turn it into a photon. Right, that kind of stuff happens.
But so you can kill an electron, yes, but they just don't die on the.
End, that's right. And you know in some superhero movies that is the definition of immortal, Like elves or in fantasy novels, are often immortal but can be killed in battle, which always confused me. But electron are sort of like elves. They will sit around forever. Like you put an electron in its own universe, it will just sit there forever, you know, learning how to sing ballad essentially, but never turning into anything.
Else I see, or not even spontaneously. Like you know, some particles just if they're sitting around, they can split into other particles.
Right, that's right, Almost every particle decays. It's only the ones that are the lightest ones it can't turn into anything else, that are sort of stuck. Those are the ones that we call stables. So an electron is a stable particle. A single electron universe will stay a single electron universe basically forever.
Like it can't break down into something else spontaneously, or it probably won't.
No, if it could, it will eventually. So this is a statement about like not a statement about probability, but about possibility. If an electron is really alone in the universe, if there's not not even any like weird quantum positrons popping out of the vacuum to annihilate it, it will sit there forever. It has zero chance of decaying into anything else, because what could it decay into. There is no particle lighter than the electron that the electron can turn into. That follows all the rules, and we'll dig into all of that.
Okay, So electrons are like elves, probably elron or electron. What would be his elf name or her elf name? Elvin, elvin name sorry, Elfish, Elfish or elvin?
Oh man, I'm way on my depth here.
So we're made out of electrons and also protons. And so the question is do protons live forever?
That's right, and this is one of the deepest open questions in modern physics. Does a proton sitting in the universe by itself eventually turn into something else? Or will it last forever?
So that's an awesome question. And so, as usual, Daniel went out there and asked people on the internet if they thought protons lived forever. So, as usual, before you hear these answers, think about it for a second. Do you think protons live forever? Here's what people had to say.
I don't really understand what living forever means for protons, but I do understand that they are converted into different forms, saying a beta plust k where the proton gets converted into a neutron and a positron is released.
I believe protons, if kind of like left alone, just by themselves, they probably could live till the end of the eternity, till the end of the universe, unless some external effects can either destroy them or change them, like maybe you know fusion or fission. Protons can change from one to another, but they are still protons.
I do not believe they live forever.
I know electrons live forever because you guys covered that in a previous podcast.
But I believe protons can be broken down.
Obviously you guys do it cervened by smashing them and creating new particles.
Interenitally, I would say that we know that like a proton is made up of up quarks or one down quarks. I think so that I would think that a proto may not live forever in a form of a proto.
I have no idea about this.
I would say that they probably do not live forever, because it doesn't make sense that they would not decay at some point.
I would have to assume that protons don't live forever, because before the Big Bang, we think the universe was a big, hot, dense ball of energy, and so I would have to guess that the universe could return to.
Such a state. I guess they're decaying all the time, and if their next holiday destination is Geneva, then they really have a short time left.
I don't think so, all right, I feel like there's a lot of confidence here in these answers. People are like no, and some people are like yes, and some people are like, depends on what you mean, living forever?
Yeah, right, exactly. We got the legalistic answers also, But it's fair because it's a bit of a vague question, Like it's possible, obviously to destroy a proton. We do it every twenty five nanoseconds the Large Hadron Collider by smashing them together. Really, the deep physics question is if you leave a proton alone, will it decay into something else? Can you turn it into something else? And that has deep implications for our understanding of the very beginning of the universe, why are universe is made out of matter? And also for like our understanding of the fundamental theory of everything, how it all links together. It turns out, proton decay is really little lynchpin for a lot of big questions.
Wow, that's a lot of stuff to hang on one simple question.
It's amazing, And it turns out proton decay is really really frustrating for particle theorists.
All right, so it seems like we can kill protons, but the question is do they spontaneously die at some point or break down or do if you have a proton, does it sit around forever? So maybe, Daniel, let's step through it one thing at a time. First of all, let's talk about particles dying in the first place, or I guess you use the term decay.
That's right. We prefer the term decay. Or you have transformed into something else, something lighter and more fhemaral. We don't like to talk about them dying.
We call it passing, not dying.
You're graduating to the next phase of your particle existence. You're leveling up. But yes, in general, particles do like to decay, and that's just a function of time moving forward and entropy. You know, the same way that you can't have a bunch of gas particles in the corner of a box and having stayed there, they like to spread out because energy likes to diffuse. That increases entropy and disorder in the universe. You can't have that much energy isolated in a quantum field, so that a particle is in a really heavy state, they like to decay down to the lowest state. They like to spread that energy out. They give off a photon, or they eject another particle, They turn into multiple particles, and they just essentially step down the ladder as far as they right.
And again, we're not talking about like particles disassembling, you know, like if I build a lego in my house, you know, with my kids, it's not gonna last very long. It's kind of eventually get dissembled. We're talking really about like quantum transformation, like a particle literally like transforms into other things.
Yeah, let's take an example of the muon. The muon is a heavy version of the electron, and the muon turns into an electron and then a couple of neutrinos to satisfy some conservation laws. But the muon doesn't last very long at all, lasts for microseconds and it just turns into the electron. And as you said, it's not like the muon is just the electron with a couple of neutrinos bound together, and then it breaks apart and those little internal pieces fly out. This really is like alchemy, Like the muon is an excited state of the muon field and then it transforms into an excited state of the electron field and two neutrino fields. And so that's our current understanding of how this muon decay happens. You have isolated heavy particle turns into three lighter particles, right, it's not a rearrangement, right.
And it just does it spontaneously, like it's just sitting there. A muon is just sitting there and then suddenly pop, it just turns into an electron and two neutrinos.
Yeah, it's one of the real quantum illnesses in our universe, Like it has a probability at any moment to decay. When an individual muon actually decays is determined by some random quantum toss of the dice. If you have like a thousand muons in a bottle, then half of them will decay after a certain time, then another half after another certain time, etc. On average. But each individual one is determined by a random toss of the dice. It's just like radioactive decay of a nucleus, which is exactly the same kind of process. I see.
It's not that it's delicate and like you know, you're stacking blocks and then suddenly when passes by or you push a little bit and it topples over. It's literally like, you know, in its fabric of its existence, to just spontaneously turn into something else.
Yeah.
The picture I have in my head is that it's like you know, flipping a coin or rolling a die every microsecond, and if it gets the right answer, boom, it decays, and if it doesn't, it sticks around it anon for a while. And so it's just like keeps rolling that die or picking a random number until it gets the right one, and then it decides, all right, now it's time for me to become an electron and a couple of neutrinos.
Right, But you're telling me that it needs to have like a path for to decay, Like it has to have, you know, kind of a solution for its decay.
Yeah. You can't just turn into anything, right, A muan can't just like say hey, I'm going to become a photon. Cool, that sounds like fun. The universe has rules, and these rules determine what particles can decay into other particles. But the important thing to understand about these rules is that mostly we have no idea where they come from. They're just like our description. It's like you watch a bunch of particles, you see what happens. You try to notice patterns, and you codify those patterns into rules. That doesn't mean you know why that rule exists. So when we say, like, you know, charge is conserved, doesn't mean we know why it's conserved. It just means that we've never seen this rule broken, so we think it's a fundamental rule of the universe. And so that's one of them. Right, Why can't just turn into a photon? Well, a muon has electric charge and a photon doesn't, So to do that would break that rule of conserving electric charge.
Right, it has to be a decay that makes sense to the universe. Okay, it's not like a total magic like an elf can just turn into a dwarf.
That's right. You have to like fill out a big application and submit it to the universe's lawyers and they have to check all the boxes and they say, all right, approved, it's more like getting a bank loan than magically transforming.
All right, And if there's nothing for you to decay into, like according to the laws of the universe, then you can't decay. You're like stuck.
That's right. And that's a situation with the electron. There's nothing lighter than the electron. Like the muon can decay into electron. Because the muon is heavier than the electron, it can go down, but to go up it is not spontaneous decay. The electron can't decay up into the muon. There's nothing for it to go down too. It's the lightest thing on its ladder. Now, there are other lower mass particles, like a photon, for example, but again, an electron can't get to be a photon because that would violate the conservation of electric charge.
Okay, so then there are rules. And if there's no step down for you to go down too, then you're stuck.
That's right. And you know, there's another particle that's very similar to the proton. It's the neutron, and the neutron is almost the same as a proton. It's a slightly different arrangement of quarks. Like the proton is made out of these smaller particles called quarks, and the proton is two ups and a down. The neutron is two downs and an up. Now, the neutron is slightly heavier than the proton, a tiny bit more mass, so the neutron can turn into a proton, no problem. And it also shoots off an electron to conserve electric charge. So that happens. And if you have like a neutron sitting around and on average, after about nine hundred seconds, it will turn into a proton. But because the proton is lighter than the neutron, there's nowhere for the proton to go. Because there's this weird rule we've observed that says you have to keep constant the number of quark triplets, the number of particles made out of three quarks cannot change, all.
Right, And there's kind of a rule that says that if when you decay down into something, you need like a force to help you do it.
That's right. All these decays happen through some force, right, Like when the muon decays then through the electron, it uses the weak force.
What does that mean, Like, like the weak force has to be involved or you actually need to like inject some weak force into it.
It means that the weak force is involved. What actually happens when it decays is that the muon turns into a muon neutrino and a w boson, and that w boson then turns into an electron and a second neutrino. So it like mediates the decay. It's like every time you feel a force, the wall is pushing back on you, for example. Really that's happening by the exchange of energy from photons and so all interactions. Every time particles talk to each other, it happens through one of the forces.
Okay, so then when you decay, you need this force to kind of like pass the energy around between the resulting bits.
Yeah, exactly, And so you know. Another example is a particle called the pion. Pion is two quarks, a quark and an antiquark, and this thing can turn into two photons, and that happens via electromagnetism. Essentially, the quark and the anti cork and decide to annihilate each other and turn into these two photons. And so that there's something for it to turn into doesn't break any of the rules, and there's a force to make it happen.
All right, So we know that particles can decay if there's something you know, less energetic that they can decay into, and if you follow the rules of the universe. So now the question is do protons decay? So mostly you and I are in how to protons and electrons and neutrons, and so the question is do protons decay? So let's get into that. But first let's take a quick break.
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All right, Daniel, we're talking about whether Protons live forever? And I feel like that's like an eighty song or something. Do Protons live forever? That sounds sounds like a heavy metal, you know, hairband.
Sounds like a love ballad, The protons of My Love will be here to the end of the universe. Give your own. That's probably in the next Villa Tech movie.
There you go, Yeah, yeah, give a rock band in your garage with other physicists.
No, definitely not, and if I did, I would not admit it here on the podcast.
You do it under an alias another particle name.
That's right, exactly. The rock and electrons, all.
Right, So we're all made out of electrons, protons and neutrons, and so the question is do protons that get because we know electrons cannot decay spontaneously into something else, but do protons decay? So the protons are different than electrons because protons are made out of other particles.
That's right. Protons are made out of quarks. And so you take a proton, you look inside it, deep inside it, and you find three particles. You find two up quarks and a down quark, and that means that like, it's made out of these three particles. It's just an arrangement of those particles. Right. But we have this rule in the universe that we don't understand, and this rule says that there's a fixed number of these quark triplets. We call this a baryon. It's just three quarks together, and you can make three quarks together and lost of different arrangements. And for some reason, every time you have an interaction, the number of baryons doesn't change.
What do you mean like interactions, but quarks always happens in three.
But if you do have a triplet of quarks involved, then you'll have the same number of triplets when you're done. So, for example, a neutron decays to a proton. You started with one triplet the neutron, which is an up down down, and you ended up with one triplet the proton up up down. Like you can't go from one baryon to zero baryons or from ten baryons to eight baryons. You have to have the same number of baryons when you start and when you finish, which is not something we understand at all.
So it's not related to threes, like if I start with two, I have to end up with two as well.
No, there's no conservation on quark pairs. Cork triplets have this special property. If you have a quark triplet, you have to end up with a quark triplet, And so for example, when we smash protons together at the large hadron collider, two protons come in. We destroy those two protons. We always make at least two baryons that come out.
I see, okay, So then neutrons, which we're also made out of. Those don't live forever. You're saying, Like a neutron, if you just leave it alone in the universe, it's gonna not be a neutron for long.
That's right. It only lasts about eight hundred and eighty seconds on its own. Now, the neutrons in your body are much more stable because the environment in your body keeps them sort of stuck together. But if you had a neutron by itself in the universe, after about eight hundred and eighty seconds, it would turn into a proton and an electron. And you notice that keeps the number of baryons the number of quark triplets constant, because the neutron is one and the proton is one.
Oh, I see all right. So a neutron by itself can decay, but it turns into a proton.
Basically, it turns into a proton plus an electron to carry off the other half of the electric charge to follow that one rule.
And so what happens there for the neutron, like the quarks inside just kind of flip and then it becomes something else.
Yeah, one of the down quarks becomes an upquark, and it gives off a w boson, which is where you get the electron and actually a little neutrino, which is how neutrinos were discovered. But these arrangements of quarks, like one arrangement of quarks an up down down that gives you a neutron, a different set of quarks up up, down that gives you a proton. The proton is the lowest mass arrangement of quarks, Like, there's no way to make an arrangement of quarks that has a lower mass in the proton. So it's sort of like lightest thing on the ladder of baryons.
But for quark triplet, Yes, for quark trip you can make something out of two quarks.
You can make something out of two quarks like a pion as lower mass. But the quark triplet ladder, for some reason, it's on its own. It's like a special thing in the universe, and if you're on that ladder, you have to stay on that ladder, and the proton is the bottom rung of that ladder. There's no lighter arrangement of three quarks than the proton. So that's why the proton seems to be stuck unless you can somehow jump off this ladder.
Oh, I see, it's like once you have three quarks, you're stead of stuck having three.
Quarks exactly, you can do something, make a different arrangement of three quarks. You can move up or down the ladder by injecting energy or waiting for it to decay, but you have to have something on the ladder. Once you have something on the ladder.
But couldn't I like, you know, split up that triplet. Can't three quarts and make up a proton, which is like you know, when they decide to go their separate ways, then you destroy the proton.
Basically, you can do that if you create a larger system, right, so you like involve it in some other bonds and some other configurations, then you can destroy a proton, for example. But a proton on its own will never decay. We think it might be stable. We've never seen a proton jump off the ladder, and every interaction we've ever seen keeps the same number of these burials.
I see, But I mean, like, can quarks exist on their own?
You can't have quarks on their own. They have such a strong interaction with other quarks, and the strength of that interaction gets stronger and stronger as quarks get further and further apart, which creates so much energy around them that they create particles out of the vacuum to make these pairs and triplets. So you never see quarks by themselves. They're always in these pairs or triplets, or maybe in weird exotic larger combinations tetra quarks and hexa quarks. But there's a special relationship that the universe has with these triplets of quarks that we don't understand. We've never seen a proton decay, and so we think there might be some special rule that protects these quark triplets. On the other hand, we have very good reason to think that protons might decay I see, or that they should.
Oh, so it's not for certain.
It's definitely not for certain. No, it's something we don't understand. It's a core mystery at the heart of physics, all right.
So you've never seen a proton spontaneously decay And what does that mean? Like, have we actually like put a proton on their microscope and left it there for a couple of hours, for days or years?
Yeah? Actually we put like ten to the thirty four protons under a microscope and we waited a few years to see if any of them decay.
What do you mean like you actually put them in a little container and left them there.
A really big container. Right. One way to do this. One way to ask like does a proton decay and can we measure it? Is to take a single proton and wait. But if you think that a proton might take like a trillion trillion trillion years to decay, then your experiment's going to take a trillion trillion trillion years. Instead, what you can do is say, well, I'm going to take a trillion trillion trillion protons, which is not that hard to make because every piece of matter has a lot of protons, and see if any of them decay. Because if none of them decay within a year or two years, then I can make a statistical argument about how long they live.
Oh, I see. So that's what you have in the in the large Hadron collider.
Not in the large Hadron collider. That's not where we study proton decay, but in big underground experiments like Supercomeo Conda and the upcoming Dune experiment are perfect for looking for proton decay.
All right, So you don't think that they can decay, but you think they might. What makes you think they might decay.
Well, the universe sort of doesn't make sense if protons can't decay. Like, if protons could decay, the whole universe would make a lot more sense, which makes us want them to decay even though we've never seen them. And the reason is that, well, you know, we have more baryons in the universe than anti baryons. Well, we talked about earlier how you have to have the same number of baryons in the universe. That's the opposite for anti baryons. Like you can actually create a baryon and antibaryon together because it keeps the number of baryons the same because anti baryons count for minus one.
Right, and again, a baryon is a triplet of court that's right.
Yeah, And so we think that the universe started off with no particles, as you said, and then particles were made, which must have made the same number of baryons and anti baryons, but somehow we ended up with a lot more protons than antiprotons. Like, we think there are almost no anti baryons out there, so there must be something out there which lets us either create baryons on their own or destroy anti baryons preferentially. There's something out there to explain why we have so much more matter than antimatter. Something allows us to make these baryons.
Right, But isn't it just sort of like electrons do? Like you know, you can create and destroy electrons. What makes us think that then electrons can't decay, but protons might be able to.
So you're right, the same argument mint gooes for electrons that we think, you know, why do we have more electrons in the universe than positrons? Right? This is this whole question of antimatter. But there are other reasons that we think that protons might decay, and that comes from like looking at the patterns of the forces. We have the electromagnetism, which is a force. We have the weak force, we have the strong force, and we have gravity. And people like to try to put these together. They say, well, it's weird to have like four different forces or five different forces. Can we fit these together into a larger pattern that like has just one overarching you know, ring to rule them all sort of force. And every time the theorists do this, every time they put those pieces together, it always ends up predicting a new little force that we haven't seen very much anymore, that hasn't been around since the beginning of the universe that can decay protons. It turns protons into a pion and a pository a what.
So when you try to you know, kind of squish all the forces together, like you're seeing theoretically, like if I try I come up with a like a super mega force that includes all the other forces, you're saying, I have to come up with a new fifth force.
Yeah, well, it's sort of like it's a part of this mega force that doesn't happen very much anymore. So put all these forces together into one mega force, and that mega force because it was around in the early universe, before the universe cooled and the forces broke into these different forces that we know today, it would have treated all the particles equally, like quarks and electrons and all those stuff, and so this force should be able to turn quarks into leptons for example, and back and forth, and currently our forces can't do that, Like, none of the forces that we have today are capable of turning quarks into leptons. They aren't capable of doing that. But this leftover force, there might be a particle which exists in the universe but requires so much energy to create that we hardly ever see it, which means it's very unlikely for it to do anything. But it might very occasionally, every trillion trillion trillion in years, be responsible for the decay of a proton.
I see, maybe protons have this secret weakness, that there's this hidden force that hasn't been around since the beginning of time.
Yeah, and maybe that's the key, right, because every time they put one of these theories together, it always predicts that protons will decay. It's just like a natural consequence of making this mega force. It has this symmetry where it treats the quarks and the leftons in the same way. It always predicts this new X particle, the X particle will take like the two up quarks inside the proton and turn them into like a positron and a down cork, and that gives you a proton turning into a pion and a positron, And so it's just inescapable. And every time the theorists make one of these theories, they're like, darn it, my theory predicts proton decay. It's very frustrating for them. They like, can't escape this prediction.
I see. All right, Well, let's get into how we might be looking experimentally for evidence that the proton decays and and when we can expect an answer. But first, let's stick another quick grete.
When you pop a piece of cheese into your mouth, or enjoy a rich spoonful of Greek yogurt, you're probably not thinking about the environmental impact of each and every bite. But the people in the dairy industry are us. Dairy has set themselves some ambitious sustainability goals, including being greenhouse gas neutral by twenty to fifty. 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. Take water, for example, most dairy farms reuse water up to four times the same water cools the milk cleans equipment, washes the barn, and irrigates the crops. How is US Dairy tackling greenhouse gases? Many farms use anaerobic digestors that turn the methane from maneuver into renewable energy that can power farms, towns, and electric cars. So the next time you grab a slice of pizza or lick an ice cream cone, know that dairy farmers and processors around the country are using the latest practices and innovations to provide the new, intense dairy products we love with less of an impact. Visit usdairy dot com slash sustainability to learn more.
We're just days away from our twenty twenty four iHeartRadio Music Festival, precedent by Capitol On.
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Year this Friday and Saturday, starting at ten thirty pm Eastern seven thirty Pacific.
Hi.
I'm David Eagleman from the podcast Inner Cosmos, which recently hit the number one science podcast in America. I mean neuroscientists at Stanford, and I've spent my career exploring the three pound universe.
In our heads.
We're looking at a whole new series of episodes this season to understand why and how our lives look the way they do. Why does your memory drift so much?
Why is it so.
Hard to keep a secret, When should you not trust your intuition? Why do brains so easily fall for magic tricks?
And why do they love conspiracy theories?
I'm hitting these questions and hundreds more because the more we know about what's running under the hood, the better we can steer our lives. Join me weekly to explore the relationship between your brain and your life by digging into unexpected questions. Listen to Inner Cosmos with David Eagleman on the iHeartRadio app, Apple Podcasts or wherever you get your podcasts.
All right, Daniel, do protons and love live forever? It is the question, But I guess we're only tackling the proton party here today.
Yeah. Don't come to a particle physicist for questions about love unless it's about love of particles. All right, So there are re s to think maybe the proton does decay. One is that, you know, it might explain antimatter, and the other one is that the theory sort of point to maybe a possible kind of new force which would allow protons to decay.
Is that kind of the idea?
Yeah, And remember this is all theoretical. This is like, we look at the way the universe has arranged and we think it would make more sense if we added this one other piece. But that piece would mean that protons should decay. So then we go when we look for it, we say, well, maybe they do. Maybe we just haven't noticed. Maybe it takes a long long time, and so we just need to be really patient.
Yes. See, it is that theoretically we don't think that the proton can decay, but if it does, it kind of means the existence of a new force. Is that kind of the significance of this decay.
Yeah, so we had to invent this rule, this number of baryons is fixed rule, which we don't really like because it doesn't really make any sense and it violates our understanding of matter and antimatter asymmetry, and it keeps us from having this new mega force et So we'd love to get rid of that and replace it with this new force and allow protons to decay. But for that to be true, we have to actually see one decaying. We have to prove that they can, because nobody's ever seen one.
So if you see one decay, then it's like you have to break the laws of physics.
Kind of Yes, if you see one decay, that's guaranteed Nobel prize because you get to rewrite the laws of physics in a way that makes much more sense to everybody, that like fits together with some real symmetry and beauty. And so everybody's sort of hoping that protons will decay. I mean not your protons, not my protons, but some protons somewhere we hope will eventually decay.
Did they already print that Nobel Prize? Like Nobel Prize for the decay of the proton, it's just sitting on the shelf waiting for people to claim it.
You know. It's one of those experiments out there that if you make it work, if you see this thing, it's basically a guaranteed Nobel Prize. There are a few things like that, you know, find the Higgs boson, see gravitational waves, find a magnetic monopole. These things that people have been looking for forever they think should exist, but nobody's ever seen one. If you found and it would really you know, fill in a missing box and our understanding of the universe.
So yeah, go look for one, expose the proton, get a prize.
That's right, This is particle physicist ten most wanted lists, right.
So then there are a couple of experiments out there that are actually trying to win this noble prize or trying to see if protons decay, and and so what's involved here, Daniel? Are they just put a bunch in a box and then stare at them? Or or do you shake it? Do you shake the box? What do you have to do?
You try not to shake the box. And in fact, you know, you can play a sort of simple calculation with any blob of protons like you. You know, you, for example, have like ten to the twenty eight protons, something like a trillion quadrillion protons in your body. So you know already that protons live for more than you know, one hundred years, because people don't tend to die of proton decay, right, you know, like people just like suddenly disintegrate like theanos snapping his thumb, right.
But also, I mean you said that the protons in my body are kind of bound together with other protons and neutron and that helps them live longer.
Yeah, But unfortunately that's the only kind of proton we can really study. Like we can take pure individual free protons and study them on their own. All we can do is study protons that exist in matter, which are in bound states. And so that's a big asterisk on all of the results that we're going to talk about today that none of them actually involves studying free protons.
Okay, so then stem me through. What are these experiments and what are they doing.
Well, the most powerful result right now, the one that tells us the most about proton decay, comes from this experiment in Japan. It's super Commeoconda, and they basically have a thirteen story stack of water and it's just a huge container filled with water, and it's surrounded by cameras essentially, and it's totally dark and it's underground. And this is an experiment that's mostly designed to look for neutrinos coming from the sun or coming from deep space or from supernovas. But it's also good for looking for proton decay because if proton decays in this tank, they think they will see.
Oh, I see, so, but it's filled with water. I guess water has hydrogen oxygen, and those all have protons, and.
They have something like ten to the thirty two protons basically sitting in a tank. And so if none of them decay in a year, then you know that the half life of the proton is more than ten to the thirty two years. I see.
But these are not isolated protons. Y'reing these bound states within the atoms. That does that protect them?
It does protect them potentially, And so, as we were saying earlier, like this is a big asterisk in all of these results. We would love to have ten to the thirty two free protons in a container that we could study and then we could directly understand this question. But we don't. All the protons we have are inbound states. We don't have ionized hydrogen gas in large enough containers that we build cameras around, and so we just have to sort of like make the measurement on bound protons and assume that it also works for free protons. But it's a big assumption, but it's also all we can do currently.
All right, Staring at water one experiment that.
You make particle physics sound so exciting.
I mean, look for variations and the laws of physics in violations of a symmetry of matter and antimatter, otherwise known as staring at water.
If it happened, it would be kind of dramatic because you would have this special signature because you would get a pion on one side, which turns into two photons. You get these two little splashes in your camera, and on the other side you would get a positron, which makes a little splash. So they've simulated exactly what this would look like in their cameras and it's very weird and unusual and different from anything they've ever seen before. And so they've been running this thing for years and years and years and they've never seen a single one. And so that means that they can pretty confidently say that the lifetime of the proton is more than ten to the thirty four years, which is a huge number because remember the universe, the entire universe is only thirteen billion years old, so like this is many orders of magnitude longer than the history of the universe.
So woa.
But again, these are in bound states or do you calibrate for that as well?
These are in bound states. No, we can't really calibrate for that. We don't really know how to extrapolate from bound state protons to unbound protons to free protons. We just sort of like assume it's going to be something similar.
Okay, So then that's one experiment, the super Cameo super Cameo Condaconda, all right, sounds like a superhero or something.
It's an awesome experiment in Japan. And then we're building one here in the United States that we talked about on our recent episode called Dune Deep Underground Neutrino Experiment. And these neutrino experiments essentially for free, you get a proton decay experiment because the same thing they can be used to look for neutrinos in Dune's case, from a neutrino beam or from the Sun or from supernova's can also look for decays of protons.
And this is kind of a similar idea too, right, Like you have a big vat of stuff and you wait for it to change.
Yeah, exactly, and in the case of Dune, it's not water, it's liquid argon. They're pioneering in new technology. They take this noble gas argon and they cool it down until it's a liquid. But it has the same property that it's very quiet. So mostly if you have a huge several ton container of liquid argon underground and you put cameras on it, it'll stay dark. But if you see an interaction like a neutrino or a proton decaying, you should be able to spot that because it's like taking a picture of a single tiny flash of light in a very dark room sensitive camera. You can pick that up.
Cool, and so far they haven't seen it. But again this one is also you're looking at argon, so you're looking at protons in a bound state inside of the nucleus of the argon at them.
That's right, But hey, that's all we can do. Dune hasn't turned on yet. They're still building it. It's going to be turning on in a few years. But because it's a much larger volume, they have many more tons, it will provide even more stringent limits on the lifetime of the proton. Or maybe they'll get lucky, maybe they'll see one decay but I.
Guess, why can't you just like isolate a proton and look at it. Is that hard? I mean you guys do it at the large pattern collider.
Yeah, you can isolate a proton and you can look at it. But a single proton will not tell you much about the lifetime of the proton unless you wait a very very long time. So you either need a lot of protons or a lot of time. And a lot of protons are very hard to keep isolated. I mean, you could have a gas of protons. We do that at the hydron collider, but you know we have like ten to twelve protons, ten to thirteen protons. You need to keep these things isolated. You need to watch them and then you need to instrument it, right. You need to be watching for them to decay. And so that's much easier to do when you have a neutral substance, something which is quiet, which doesn't otherwise make lots of flashes of light.
Oh, I see, you can isolate a whole bunch of protons, but then you actually have to notice if like one of them decays.
Yeah, because a bunch of protons together is called the plasma, and a plasma is not a quiet thing to instrument, right, that's like where we try to do fusion and stuff like that. So it's a pretty tricky experiment to do for actual free protons, which is why we only ever do it for protons in a bound state. But you're right, that doesn't actually tell us about free proton all right.
So there are people looking for this decay of the proton. Then there's people staring at water and are gone waiting for one of these protons to suddenly die.
That's right, staring at water waiting for a Nobel prize to pop.
Out out of a little tiny proton.
Hey, if I told you stare at this tank of Nobel prize might appear, you know, you might devote a couple of years to that, Yeah, shorter than a phg.
A couple of trillion years went on. Or you might not see anything.
Unfortunately, that's usually the case in particle physics. You're looking for something crazy, you're hoping you might see something spectacular, but to see nothing. But the good news is that most of our experiments are still interesting even if you don't see anything, because you can still say something. You can say we didn't see the proton decay therefore we know it doesn't decay on average in less than ten to the thirty four ten to the thirty five years. So you still get to say something interesting about physics.
So I see, all right, So it sounds like you're pretty confident then that we can say that the proton does not decay or won't die, or will live for at least ten to the thirty four years. Yeah, which is pretty much forever, right.
It's almost forever. I mean, it's a lot longer than our universe has been around so far. But it's also still a real problem for theoretical physicists when they try to construct their grand unified theories, their theories of everything, when they want to understand what happened at the very beginning of the universe, they have to do it in a way that keeps the proton from decaying, and that's theoretically very tricky. It's like, you know, they have to pass through the eye of a needle to keep the proton from decaying in their theory. And so everybody would be very happy to see a proton decay.
Oh, I see, because it would make the equations easier to solve.
It would mean that all the theories which predict proton decay might actually be correct, and those equations are beautiful and they make a lot of sense, and they answer a lot of other questions about like matter and antimatter and the forces being unified. But those equations can't be right if the proton doesn't decay. If the proton doesn't decay, those equations are just wrong, even though they're beautiful and they're simple and they're attractive. So then we need to find some other way to solve those problems. And theoretically that's just much harder without proton decay.
So it's not just a whole bunch of physicists looking staring at water. You're staring at water waiting for the proton to die, hoping, hoping. You're hoping for the proton to die here.
That's right, that's the big twist. You thought we would be rooting for the proton to live forever, but instead we hear anti protonites.
You're like, just die already.
We're cheering on its demise.
I want to retire and win.
That's right. Somebody in a very future universe will finally see a proton decay in a trillion trillion trillion years. Hope they're still giving out Nobel prizes.
Then I hope our protons are still around. All right, Well, we hope you enjoyed that and got a little bit of a sense of how long things live in the universe. Apparently some things do, some things don't.
And it's amazing the cosmic importance of one little proton, a single proton in a vat of water in Japan decaying could crack open the answer to these deep mysteries about the beginning of our universe, the balance between matter and anti matter, how everything fits together. It's incredibly important, and it just really highlights the connection between particle physics and cosmology and astrophysics, and really particle physics is basically the whole universe. That's what I'm saying.
You're saying, give us more money. We're studying everything.
That's right. That's what everything I say translates to effectively.
All right, Well, I hope that give you some stuff to think about. The protons in your body and the electrons might live.
Forever, but particle physicists are hoping they don't 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. How is 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 asdairy dot COM's Last Sustainability to learn more.
We're just days away from our twenty twenty four The Art Radio Music Festival, presented by Capital On.
The biggest headliners in live music will be taking over to Mobile Arena, Las Vegas.
Lost some special surprises at moments you are not gone to want to miss. Stream only on Hulu the iHeartRadio Music Festival.
And listen on iHeartRadio the most anticipated live music events of the year.
This Friday and Saturday, starting at ten thirty pm Eastern, seven thirty Pacific.
Hi.
I'm David Eagleman from the podcast Inner Cosmos, which recently hit the number one science podcast in America. I mean neuroscientists at Stanford, and I've spent my career exploring the three pound universe in our heads.
Join me weekly to explore the relationship.
Between your brain and your life. Because the more we know about what's running under the hood, better we can steer our lives. Listen to Inner Cosmos with David Eagleman on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.
