Could some particles have tiny electric charges?

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Speaker 1: Hey, Daniel, you have an electric car, right, Yeah, I drive a Nissan Leaf these days, and last time I had a Chevy bolt, so you bolted from the bolt and to turn over a new leaf, I left it behind. Now, how much does it cost to charge up with one of those electric cars? Well, that's kind of a charged question, but usually less than ten dollars. Actually, oh wow, you only charge you ten bucks to charge your car? You go to one of those charging stations. No, I usually charge it at home where I'm in charge. You can charge ten bucks to charge your car where you're in charge, and charge it on my credit card. You should charge them. I'm positive that won't work. Hi'm for Hammo cartoonists and the creator of PhD comics. Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I actually do sell charges back to the electric company. Nice solar panels. I do have solar panels, but unfortunately the electrons I produced don't end up in my car. They have to go back to the company and then I buy fresh electrons from them. I don't have one of those massive home batteries yet. Yeah, you don't want old electrons? The cool kind of stale, right. The thing, I don't know. I've had some really vintage electrons created during the Big Bang, and they were pretty tasty. Aren't all electrons created in the Big Bang? Some of them might have been, but also electrons are being created all the time, and so some electrons might be very, very fresh, and some of them might have had many, many lives before you. Do you have like an electron summerlier that tells you the vintage of electrons? And how do you taste electrons? Do you just stick your tongue in the electrical outlet or what? What advice are we giving the public here? That's a shocking suggestion, Jorge, sticking your tongue in the outlet. I'm positive that's not a good idea. But it is an interesting philosophical question of whether you could taste the age of an electron or even somehow tell its age. We don't think so, because they're quantum particles, so they're all identical. Every electron is the same as every other electron, and so there's no way to tell if an electron is fourteen billion years old or fourteen billiseconds old. Yeah, it would be kind of rude. To ask anyways, But welcome to our podcast Daniel and Jorge Explain the Universe, a production of iHeartRadio, in which we try to be positive about all the charged questions there are about the age of the universe, how big it's been getting, and what it's been eating. We like to think about everything involved in understanding the universe, from the deep nature of the fabric of space itself, all the way up to the shape and size of the universe, and everything fascinating in between. We want to tickle the curiosity that we know is inside your mind and make you wonder at this marvelous universe. Why is it this way and not some other way. That's right because it is an electrifying universe, full of amazing things happening in it, things coming together, things being pushed apart, And we like to zap all of that knowledge into your brain so that you get a small buzz. And the electricity is one of the oldest topics that humans have been thinking about. After all, it's obviously out there in the world. You don't need a superconducting super collider in order to study electricity and magnetism. You just need to watch a rainstorm and look at lightning or zap yourself as you walk across a carpet. So humans have been aware of this strange phenomena of electricity for a long long time. And wait, wait, wait, wait, they had electricity back in the steam age. How did they power their light bulbs? You know, almost all electrical generations still uses steam. It's incredible how versatile the steam engine really is. That what the electrons are always wet. I don't know what's going on with the plumbing in your house that your electrons are wet. But that does not sound like a good combination. You know, not so much wet as steamy. I get steamy electron. Well, electricity has been something that's been tickling the minds of humans and physicists and proto physicists for a long long time, you know, watching a rainstorm and wondering like wow, what is that crazy? Zapping all the way up to Benjamin Franklin trying to understand, like what's going on. It's been something we've been working on for a long time. We've made a lot of progress, and yet there's still really basic questions about how it works. You know, the origin of the word electricity, Like I wonder when humans started to think of electricity as electricity because I imagine, you know, for millions of years we saw lightning, but we didn't think it was anything different other than light or you know, strips of light. Yeah. I think there's a long history of crazy ideas to explain what we see out there, and it wasn't until a few hundred years ago that people trying to be sort of systematic about it and come up with like something you could describe as a theory to explain what was going on. You know, before that we had basically mythology zoos throwing lightning bolts and this kind of stuff. I see, so Zoos was the first electric company. I wonder if zeus charge for lightning bolts, right, I don't know. They are pretty spectacular to look at. But anyways, electricity is one of those old subjects that humans have been thinking about and wondering about, and apparently it's still something that we wonder about today. That's right. We have graduated from thinking about electricity as the product of an angry god to thinking about it as a strange, invisible fluid that flows through matter, to modern ideas that electricity is carried by tiny, little discrete charged particles, each of which carry this strange quantum label of electric charge. It doesn't sound like we've progressed much there from saying electricity is something that God throws down from the sky to something that little tiny particles have. Well, maybe emotionally we've progressed. You know, we don't think electrons are angry as Zeus was. So you know, maybe it's just a calmer theory of the universe, or maybe you just don't know if your electrons are mad at you. It could be, especially if you ask them their age. But that means that all electrons in the universe would have to be mad at you. That's like a whole universe filled with screaming, mad electrons. That's kind of terrifying. Maybe it's only the ones that you use for your car. They don't like where you're going. The ones we put to work, Yeah, exactly, just because you don't want to walk, Daniel, even if I'm walking, that uses electrons. Right, there's electrons in everything. Anytime you do some work, that's going to be electrons involved. So that's why the electron labor union is so powerful. I wonder how they hold together. But there is a lot we don't understand about the universe. And it's kind of surprising to think about the idea that there are things we don't understand about electricity. I feel like the electricity is something that we use every day. I mean, we're using it right now to record this, and also everyone is using this to listen to this podcast, and yet there are things we still don't know about it. Yeah. Well, you don't actually have to understand the universe in order to use it, right. You took advantage of gravity holding you under the earth surface long before anybody had any understanding of gravity, and even four hundreds of years when we had a pretty deep misunderstanding of gravity. So it's just sort of part of the process of science to develop these descriptions of what we see, try to explain them, and then refine them as time goes on. There will always be open questions things we don't understand. What I hope that listeners appreciate is that some of these questions, some of these things we still don't understand, are really pretty basic and have to do fundamentally with the nature of electricity. What is it anyway? Yeah, And so today on the program, we'll be tackling Could there be particles with different electric charges? That's right. We know about a few different kinds of particles with a few different kinds of electric charges. But the curious person always wonders, like, well, why is that? It? Is there more on the list? Is the universe capable of doing other things? And it just isn't? Or are there other particles out there with really weird electric charges? Yeah? I guess when we say different electric charges, we mean different charges than the electron, right, Like, could there be a particle out there with a charge that's not the same as the electron? Yeah, we actually do have a few examples of that, right, Like quarks have strange charges like two thirds and minus one third, and the electron is this charge negative one. But it's interesting to think about, like could there be particle with charges of like one millionth or one billionth or like pi or other strange numbers. There seems to be like a pattern to the electric charges, or they seem to prefer these sort of discrete units, But we don't really understand why that is. Oh, I mean we're asking today whether you can have a particle with like point zero zero zero one of the charge of the electron. Yeah, is that possible to do those particles exist? What would it mean for the universe if they did or they didn't? But you said that, we know about particles that have one third of the charge of the electron. That's a quart or some of the courts. That's right, Some of the quarks have charged one third, and some of the quirks have charged two third. Basically, every particle we've ever seen either has zero charge or some multiple of one third of the electrons charge. Nicee. So today we're asking if you can go smaller than that? Could there be particles with less than a third of the electron charge? Yeah? One fifth, one ninth, one billionth even are there limits? Is there a rule that prevents a particle from having some super tiny electric charge but not zero? And I assume that's not a question with a small answer, and maybe even answer that will shock us. That's right, it's a small question with big consequences for the philosophy of electric charges. Was usual. We were wondering how many people out there had thought about this question or wondered whether particles can have tiny electric charges. Thank you very much to our list of volunteers who answer these questions for everybody else's enjoyment and education. If you would like to contribute to your voice to this segment, please don't be shy. We don't describe. We let everybody participate. Right to me to questions at Daniel and Jorge dot com. So think about it for a second. Have you heard or think that electron can have tiny electric charges? Here's what people had to say. Yep, why not. I will accept particles of any coolure. I'm sure there's no discriminating against fractional electric charges. I would guess that particles with fractional electrical charges would be possible, given that in chemistry they have certeometry, and so it maybe does not real out the fact that this could be the same for sometime a particles. I have heard health spin as a quantum property, but never health electrical charge. So I will say no, But since you are asking it, maybe yes, my guess would be probably. I'm sure there's a law physics it says no, you have to be a plus or minus or no charge. But I don't see why you couldn't have a fractional charge. I suppose, so, yeah, I think that is the case. Today. I think we have quarks with like one third charge or two thirds charge, And I think the actual charge of an electron is some crazy fractional number and we've just chosen to assign it the value of one for convenience. So yeah, I think that's possible. Well, isn't charges caused by particles like electrons considered particles? Am I getting that wrong? I'm guessing no. Well, I'm going to walk into the obvious trap here and say that I think no particles cannot have tiny fractional electric charges. I think that an electric charge is either present, positive or negative or absent, and is an indivisible quality. I'm hoping, of course, that, true to the nature of this podcast, this obvious trap will turn out by the end of the podcast to have been an a double bluff and vindicate mind ignorance. All right, A lot of people said yes, because, of course, maybe we asked the question wrong. I think that most people don't even imagine the existence of like particles with one millions of the electric charge. Yeah, that's not something nice they open night usually wondering about. I mean, maybe one thousands, but not a million. There's some limit there. You're like, one thousands is reasonable. One millions. This crazy. Yeah, yes, that is what I think about at night. Well, you know, a way to explore the universe is just to try to be creative, to think about, like what assumptions are we making because we've only seen certain examples, what conclusions are we drawing because we've only seen a subset of what the universe can actually do. So sometimes it takes a little bit of creativity to like break out of the box we've been living in and wonder what could be outside that box. Sometimes we don't even realize the boxes that we are in. So I love this question precisely because a lot of people are like, huh, that's interesting. I never even consider that there could be other kinds of particles with weird electric charges in them. And that's what makes it exciting, because that's the best moment in physics, when we realize we've been overlooking something and maybe it shows us something new about the real universe out there. I wonder if maybe what we're asking here really is like, are there maybe particles with weird electric charges that we didn't know how weird electric charges? Is that kind of what we're asking, like, maybe there are things there are particles out there which just haven't seen them or known about them, that actually have these weird charges we just haven't noticed. Yeah, exactly. One possibility is that there's a new kind of particle out there with weird electric charges we just haven't noticed yet. The other possibility is that maybe some of the particles we do know don't actually have zero electric charge, they have very very very very small electric charges. All right, well, let's jump into this topic, Daniel. Let's start with the basics. What is an electric charge? Well, we don't really know. All thanks for joining us. See you next time. It's fun to joke about that, because that really is the answer. We don't actually know what an electric charge is physically. It's part of our description of what we see happen in the universe. So we notice that some particles that accelerated if you put them in an electric field, and other particles don't. Right, And we even have an equation that describes it. Right. Force is equal to charge times the field strength. So if a particle is accelerated when you put it in an electric field, we say that particle has charge. If a particle ignores the electric field, we say the particle has no charge. And the bigger the charge of the particle, the greater the force that it feels. But it's just sort of like our description of what we see. We put this into our mathematical story about the universe. That doesn't mean we know like what it is, right, But it's even more confusing than that, because it's kind of like, how do you define an electric field? Isn't an electric field defined as how the or this change on a particle that has charge? Yeah, exactly right. We say the fields are generated by charged particles. We don't ever even see the fields themselves, right, you can't observe a field. The only thing you can observe is the field pushing on particles. So if you want to get down to the nitty gritty, what do we actually see is that some particles push on each other, and we have this intermediate thing we call a field, which allows particles that are far away from each other to push on each other. But fundamentally, we say, some particles push on each other and some particles pull on each other, and the charges in the fields. It's just sort of like our mathematical story of what's happening there that to describe what we see. So maybe you would define a charge more accurately. As you know, if you have an electron here and an electron there, they're going to push against each other, and that push sort of depends on this thing that you call a charge. Yeah, you can put a label on every kind of particle and that label tells you how to predict whether the particle will be pushed by another particle or it's field equivalently, and that works, and it works really, really really well. It works incredibly well. It's one of the best tested theories we have in physics. We can do pages and pages of calculations to predict how electrons will push on each other and how they will shoot photons at each other, and we can do experiments to test those predictions, and the experiment and the prediction agree to like eight or nine decimal places. It's really extraordinary how accurate it is. And so you look at that theory and you're like, hm, well, if it's so accurate, maybe it's really describing what happens in the universe. Maybe this thing we invented, this idea of charge, is a property of the particle itself, not just part of our story about the particle. Right, it's sort of like mass is for gravity, Right Like, if you have two particles out there in space, they're going to attract each other depending on this thing about them called mass, And that's kind of the same for charge, right Like, if you have two particles, they're going to either attract each other or repel each other by a certain amount, pending on whether they have this thing called charge. Yes, excellent, exactly, And in particle physics we generalize this concept of charge. Do not just refer to electromagnetism, as you say. You can think about gravity in terms of gravitational charges or masses, and you can think about the strong force in terms of strong nuclear charges on quarks. Those are even more complicated because instead of having two values like plus or minus, have three values red, green, and blue. The weak force also has a kind of charge that we call weak hypercharge. So in a more general sense, charge tells you whether a particle feels a force. Like the electron has an electric charge, but it has no strong nuclear charge. It doesn't feel the strong nuclear force. A quark has both an electric charge and a strong nuclear charge, and so it feels both forces. So really, charge in general is a label about saying whether or not a particle feels that force, and it's something philosophically we like attached to the particle. We say, this is a property of this particle. The electron has the charge physically, I don't really know what that means, like where in the electron is it. It's just sort of this like ineffable quantum label we attached to it. We don't really know where it comes from, like what generates the actual charge itself? Well, I think in quantum theory and correct me if I'm wrong. But it also because it sort of has to do whether a particle interacts with certain quantum fields or done right, Like maybe that's another way to define it. If the electron doesn't interact with the strong force field, then it just doesn't have a strong charge. Yeah, I think that's another way of saying the same thing. You can think about all these quantum pictures of the world either in terms of particles that are pushing on each other or in terms of fields, because remember, these particles are actually just little wiggles in quantum fields, and those fields can sometimes talk to each other. So, for example, the electromagnetic field for which the photon is a particle can interact with or talk to any field that has charges. So the electron field of which the electron is the wiggle is the particle, right, that will interact with the electromagnetic field, and so will the field of the w boson because it has electric charge. So as you say, the fields that interact with a certain force, we say their particles have that charge, and the fields that don't, we say the particles don't have that charge. So, for example, the neutrino field, neutrinos have no electric charge. Neutrino fields and electromagnetic fields totally ignore each other. Right, So then maybe you can define charges being like whether or not auto particle interacts with the electromagnetic field. Yeah, for the electric charge, And in terms of like particle theory, they often talk about it as coupling. The electric charge is the way that the photon field couples to the electron field. How those two fields sort of like let energy slide back and forth between them. I feel like we're getting a little steaming out there. Are we back to talking about steamia not steaming a not safe for workway? You know, we're just talking about connections. We're just talking about energy sliding from one kind of feel to the other. All right, well, what sounds like we kind of have a definition of what charge is. We just don't know where it comes from kind of right, That's the thing, like, we don't know why some particles interact with the electropicnet feels and why some don't. That's right. We have a very effective description of it, but we don't know why some particles have it, what the rules are for what charges you are allowed to have, and where it comes from at all. Yeah, I guess some particles just have that spark and others some particles just have a positive attitude. All right, Well, let's get into a little bit of the history of this idea of an electric charge. Where did it come from? How did humans start to figure this out? And then let's get into the bigger question of whether electrons or things with electrical charge can have tiny, almost imperceptible charges. But first let's take a quick break or I we're talking about charges, and we're charging ahead here with this topic, talking about whether electrons or charged particles that have the fuel electricity can have electrical charges that maybe have been escaping our notice for thousands of years. So Daniel, maybe step us through here a little bit on the history of charges. When did we start noticing that some things have electrical charge? So we certainly had noticed the properties of electricity for a long long time, right, static electricity and lightning, these are things everybody was aware of, and until around the mid seventeen hundreds, the idea to explain these things was dominated by concepts like effluvium or this basically this two fluid theory of electricity and magnetism. It was like this invisible fluid that flowed through objects, two different kinds of invisible liquids flowing through objects, one positive, one negative, that could cancel each other out right, Because as you said, I imagine that this is something we've noticed for maybe hundreds of thousands of years. Imagine, you know, even caveman would get you know, static electricity in their hair would stand up right, But for them it was probably just you know, magic, or they had no way to grant that there would be a reason for that exactly. And the process of science is want to try and develop like an explanation for these things. How can we unify different phenomena that we see, the static electricity in your hair and the lightning in the sky, Which of these things are related and which of these are totally different phenomena. So that's the process of physics, right sorting out all the phenomena we see and trying to coalesce them, boil them down into a few simple explanations, and try to find the relationship between those to give, like, you know, a single description of everything that's happening. And so this really is an ancient process. It's a great example of the whole process of physics of trying to coalesce many different things down into one explanation. But I think you're saying that maybe we did have sort of some idea that it was something that flowed between things, right, Yeah, it was sort of considered to be a liquid. We didn't have the idea of particles yet. It wasn't until you know, the late eighteen hundreds when J. J. Thompson discovered the electron that we thought of it is like isolated to a little particle. It was sort of more similar to early concepts of heat. You know, this liquid that flowed between things. And it's really fascinating because the original idea was of two liquids, one positive and one negative, which could flow between things, and they could cancel each other out. It was mostly trying to explain like electrical attraction and repulsion and that theory. You know, it sounds right because we know that there are protons and there are electrons, which is actually not quite right because the protons don't really flow. Right. What happens with electricity in objects, It say it's the electrons that are moving. And so it was actually in the mid seventeen hundreds with Ben Franklin, came up with the one fluid theory of electricity. Basically, there's just one kind of thing that's moving around. Now we know, of course those are electrons, and that's a more accurate description of what's actually happening, but it sort of ignores the protons and the positive charge. So it's sort of fascinating from that point of view. Historically, I think you're saying that maybe like our early ideas about electricity was that it was sort of like a fluid. I guess I'm sort of like magical fluid in a way, and that maybe at first we thought there were positive fluids negative fluids, but more actually, when you see electricity on an everyday basis, it's usually the negative electric charges that are flowing around exactly in immaterial it's the electrons that are moving. The protons are usually in the crystal and can't really move very well. The nuclei don't flow, so it really is the electrons that are moving. And Ben Franklin did all these experiments with cloths and glass rods, and of course his famous experiments with lightning. He's one of the first people to try to explain all these things in terms of a single phenomena. Did he use hundred dollars bills? Also? He was all about the Benjamin's for sure. But then it was in the late eighteen hundreds that J. Thompson did his experiments with cathode ray tubes and he showed that there were these tiny little dots of matter that carried charge with them. He showed they could be deflected by electric fields. We have a whole episode about the discovery of the electron which want to dig into the details of that one. But it was a really interesting moment because he showed where the charge was. It went from being like this weird invisible not quite magic but imperceptible fluid, to being isolated to these little bits. There was something out there that was carrying these charges. We'd like identified a little bit of matter. It had mass and it had electric charge to it, So that made it like concrete in a new way. So wait, he could actually see individual electrons. How do you see an electron? Well, he couldn't see an individual electron, but he could see them land on a screen in his cathode ray You know, cathode ray tube is basically the way TVs used to work. They have a little gun of electrons that would shoot at the screen, and you would have fields that bend them, so they would shoot at different places at the screen it would scan across. And that's not very different from his original setup where he had a little hot bit of metal that boiled off electrons and then they were accelerated by a field and then bent by another field. So what he showed was that you could bend their path using fields, which meant that they were carrying the charge, and he could change where they landed by changing those fields. A really clever set of experiments. Right, But I wonder if he thought maybe there were just droplets of this fluid right, Like he maybe didn't think of them as particles necessarily, did he? Because the quantum idea wasn't around yet, that's right. But he actually is the one who came up with this concept that these things were all isolated on these tiny little dots. He didn't use the word particle. He invented this other word called the corpuscule, which he hoped was going to take off and that we'd all be corpuscular physicists by now. But fortunately that name was dropped later by other people. But he definitely identified these things as tiny little dots with mass and with charge bundled together into the same physical location. It's really the first moment where we started putting these labels on tiny dots of matter, sort of the invention of the concept of a particle. There. Did he call it an electron or when did the name come into use? He definitely called them corpuscules. The name electron came later, which I don't know. I'd prefer the word electron two corpuscule. It's really amountable. And it was Milliken a few decades later who did his famous oil drop experiments where he showed that the charge is discreete that you couldn't have like one and a half charges or two point seven charges but you could have like one, two, or three these very precise experiments that were balancing various forces and showing that they were integer quantities of them. So at that point we knew that charge was a thing, that it was attached to these tiny little particles, and that their charges were discrete. You didn't have like some particles running around with one point two seven charges and other ones with zero point eight nine. You either had one electron or two electrons or three electrons. You know, this is around the same time that quantum mechanics was being developed, when we had the understanding that light was packets of photons. You couldn't have like one point two of them. So the whole idea of discretization was sort of taking over physics. Sounds indiscreet, but I guess my question is how did Milliken figure this out? I mean, you're talking about the early nineteen hundreds. How did they have experiments that can measure things down to the one electron level? This is a really hard experiment to do. He took little drops of oil and he sprayed them out of a little sprayer, which basically strips them of some electrons, which basically ionizes them, and so now they have electric charge, and let them fall through this little chamber until they reached terminal velocity, and then he turned on electric field to try to make them levitate, and by tweaking the electric field, he could find exactly the right force he needed to balance the downward going velocity. You could make these particles float. Essentially, and what he noticed was needed a certain field or like twice that field or three times that field, which he hypothesized told him like how much each drop had been ionized. So essentially he was measuring like how much electric force you needed to levitate these drops, and he noticed that it always came intoger quantities, So he wasn't studying individual electrons. You couldn't see individual electrons, but he was studying the overall electric charge of these little drops of oil. But that sort of only works if the each drop is the size of one electron, right, Like if you have a whole cluster of things with electrons, would you still notice that kind of discrete electric field. Yeah, you can have a whole oil drop. But what he's measuring is the ionization of that drop, like essentially, how many non neutral particles are in that drop, Because that's what's going to affect the force that the drop feels when you put it in an electric field. So he was noticing that you could ionize these drops by one unit, or two units, or seven units, but not by three point two units. Interesting. All right, well, I think that's kind of the general history of electrons, right, And that's where the idea of the electron took off, right as a discrete thing. And then the rest is history. The rest is history. And now we regularly produce electrons and ar collider and study them in gory detail. In the mid nineteen fifties, we had quantum electrodynamics, this theory of photons and electrons as oscillating quantum fields, which is basically the modern story of electromagnetism. All right, well, let's get to our question of whether electrons or other particles can have charges that are smaller than one third of the charge of an electron. I guess, Daniel, why are we asking this question? Or I guess what do we know about charge in general? So what we know is that electrons have charged minus one, which is just something we assigned, right, We could have given electrons any charge. It's really just totally arbitrary, and that protons have the opposite charge. Protons, of course, are made of quarks, and those quarks have the weirdest charges we know. They have charges like plus or minus two thirds or plus or minus one third. There are also particles out there neutrinos that have charged zero. So all the fundamental particles that we know about have charges zero one thirds, two thirds, or like the electron, they have effectively charge one. These units are arbitrary, but everything seems to have a charge that a multiple of one third of the electric charge. That seems to be the minimum charge out there. Of the zero, of course, which you can consider still a multiple of one third. There's no particles out there that we've seen that have charged like two sevenths or fourteen ninety firsts or you know, pie times the electron. I guess, just to be clear, there's only four particles that we know about that have electric charge. Is that true? Well, there are the four kinds of fermions, right, electrons, neutrinos, of quarks, and down quirks. There are also the other generations like the charm, the top, the muon the towel. Those all have the same electric charges as the base particles. So yeah, there are four kinds of fermions, and each one has a different charge. Right, So I guess what I mean is that we haven't found any other particles other than these four and their generational cousins that have electric charge, right that we The only other particle with electric charge is the W. The W is one of the first particles of the weak force, and interestingly, it also has electric chart. So there's two of those. There's the W plus and the W minus, So those sub charges plus one and minus one. Those are the only other charge particles out there. The other particles like the Higgs boson and the photon and the gluon and the z boson, all of those have zero electric charge. Wait, the W particle also has electric chart, and it's exactly the same as the electron. It's exactly the same or opposite of the electron. And that's important because the W and the electron interact with each other. For example, a W can decay to an electron and a neutrino, and that conserves electric charge. You start out with charge minus one, you end up with an electron with charge minus one and a neutrino with charge zero. So electric chart starts at minus one ends at minus one. It's conserved. That's something else really fascinating that we know about electric charge is that it can't be created or destroyed. It's always conserved in the universe. Now, is that a cool incidence that the W happens to have the exact same charges the electron? I don't think we know the answer to that. But if it didn't have exactly the same charges the electron, then it wouldn't be able to interact with the electron. Like the W had a charge of one point two, then it couldn't decay to an electron and a neutrino because charge is conserved. And so basically it would mean that it couldn't interact with our kind of matter, and then it wouldn't participate in anything that we knew about, And so it might exist in the universe but not be something we could see or interact with. Right, And so the fact that the W has the same charge as the electron is what allows it to participate in our part of the universe, and so that's the reason we know about it. So it might be that there are particles out there with weird charges that don't interact in the same way as our particles, and that's exactly what people are looking for. M I see. That's I think this gets into kind of the heart of what we're asking here today and why maybe we may have observed other particles that have different terms. Because I know we talked about before, how the idea that the proton has exactly the opposite charge of an electron. It's sort of a coincidence in the universe, and if that was any different, we wouldn't have all those things we have today like us. That's right. It's sort of explained and sort of not explained. Right, It's not explained in the sense that, in principle it could have been something else. Right. It could have been that the quarks don't have exactly one third and two thirds the charge of the electron, so when you put them together you get a proton that's not exactly the opposite charge of the electron. That could work in physics, but it's explained in the sense that that universe would be so different from ours that it's sort of impossible to even imagine what that would be like. Would be very different from the universe we experience. So to have a universe like ours, requires that balance. That doesn't mean we know why that balance exists, right, So it's a really fascinating question philosophically. Yeah, all right, Well, let's get into this question of whether charges can be different than the ones from the electron, and specifically much smaller than one third the charge of an electron, Like maybe there are particles out there with that kind of charge, we just haven't seen them. So let's get into that question. But first, let's take another quick break. All right, we're talking about charges in the universe, and Daniel were saying that, you know, the electron has a charge of negative one because that's what we gave it, and we know that the proton, which is made out of quarks, has an overall charge of plus one, and the fact that they're exactly the opposite is sort of the reason that we can't have atoms and things like that. Right, if it was any different, what would happen If it was any different, then you couldn't get neutral hydrogen, for example. Right, there was this moment in the universe very early on, when electrons and protons cooled down. They slowed down enough that their mutual electrical attraction action could make them warm neutral hydrogen, and the universe suddenly became transparent. Right, this is the moment when the cosmic microwave background radiation was created and flew through the universe. And neutral hydrogen is essential for basically the formation of the whole universe. It's basically what makes up the universe, neutral hydrogen. Wait, wait, why is that important? I guess if let's say the proton had like one point one the charge of an electron plus one point one, you would still get hydrogen, but the hydrogen would just have an overall charge of plus point one, wouldn't it. Yeah, you could get hydrogen, it wouldn't be neutral hydrogen. And I think that has a lot of downstream effects for how chemistry happens and how life is formed and everything else that we rely on. But yeah, I'm not an expert on chemistry and biochemistry. But you could still have a universe way with suns and planets and stuff, couldn't you. You could have a universe. And I imagine that fusion could still happen because fusion fundamentally is really just a process between proton You don't really need the electrons. Like inside the heart of stars, protons are anyway ionized to you don't really have the electrons around when you do fusion, So you can still have fusion if protons don't have exactly the opposite charge of electrons, so you can still have light in the universe. Right, that's good. Remember that electromagnetism is much stronger than gravity, So for gravity to take over and to tug things together into dense objects probably requires everything to be electrically neutral. Nothing is electrically neutral, and everything is repelling each other. Gravity might not be able to overcome that and form dense objects like planets and stars and ice cream. Well, I wonder if that's true. One you could still form them, they would just maybe be different proportions of the different elements, right, Like you know, if hydrogen was like plus point one, then maybe you could have other materials that are like negative point eight, and then you could have you know, two of these and one of these. Yeah, it might be possible to still form neutral objects. But for that to work, then the charge can't just be arbitrary. They have to be like some rational fraction of each other. You know, the proton is charged pi and the electrons charged negative one, then no, arrangement of protons and electrons will give you a neutral object. It's just impossible. But if they are a rational fraction of each other, if the proton is like five fourths or nine eighths or something, then yeah, you can have a certain relationship. You can make weird atoms out of eight protons and nine electrons or something like that, Right, And I wonder if that would be okay, right, Like, like we can have molecules in our body that have an overall charge, right, we certainly could, Like a molecule in our body can lose an electron in one of its atoms and it would still be a molecule. Like maybe I wonder if biology or nature needs neutral particles. I know that a lot of our biological processes rely on charges, right, Like our entire nervous system is basically electrically charged and uses ions. So probably things like that could function. But I think the whole structure of the universe would be very different if you had these different kind of chemicals. But even this is relying on an assumption, right, It's an assuming that you could still build something neutral so that gravity could take over. If instead charges could have any value, then there's no guarantee you could put particles together to make things that are neutral. And I think that's one of the deepest questions, like why are these particles rational fractions of each other's charge one third, two thirds, five fourths even, you know, these kinds of things instead of zero point eight seven two or irrational numbers. Yeah, I guess that's the main question we're asking today, is like, why can't that be because as far as we know, the particles that we do know about have these multiple charges of each other. Right, that's kind of the idea exactly. And so if you ask theoretical physics, like what prevents us from having particles with charge zero point oh one or zero point one seven nine two, or you know, just keep going, and the answer is nothing, like there is no theoretical prohibition against it. But that's mostly because we don't really understand where charge comes from and how these labels get us signed, and so we haven't invented rules that say you can't do it. We just haven't seen any particles like that in the universe. Right. And the weird thing I guess is that you know, an electron, it comes from the electric quantum field and a quark comes from the quantum quark field, and yet they seem to have charges that are kind of multiples of each other. That's the weird thing too about the universe, right, Yeah, that is definitely a weird thing because as far as we know, those fields are not that closely related, Like there are similarities there between the electron, the neutrino, and the quarks are either paired together in similar ways, Like the W for example, can decay to an electron and a neutrino. It can also decay to a pair of quarks because that pair of quarks have a charge difference of plus or minus one. So there's definitely relationships between them, but we don't really understand all those relationships. What this suggests is that there's some deeper relationship between the electron and the quarks than we even understand. Like maybe the electron and the quarks are all made out of some tinier little particle, and some arrangement of those little tiny particles, which each have their own electric charge, is what gives you the electron with charge one or the quark with charge minus one third, the same way that like atoms are built out of the same building blocks and you get all sorts of different behavior and overall charges and whatever. Maybe electrons and quarks and neutrinos are all built out of the same tiny little building blocks, and that would explain all the relationships between them, including this strangely fortuitous relationship of their electric charges. Maybe there are puscals out there in the universe, and maybe you are corpuscular particle, I mean, opuscular physicist. It's so much fun to say. But there are theories out there about these so called milly charged particles, particles that have really really tiny electric charges. We're talking about things down to like a thousands or less of the charge of the electron, and there are experiments out there searching for them as well. Well. I feel like there's maybe two possibilities, right, Like, there's a possibility that there is a whole new kind of particle that we don't know about that has a charge that's one thousands of the electron or you know, a point nine to infinity charge. That's one possibility, is that you have a whole new kind of particle that we hadn't seen before. And then there's the other possibility. Then maybe there are electrons out there with one point one electrical charge. So which which one are we talking about here? We're talking about both of those possibilities, but we're also talking about a third possibility. Maybe there's another kind of particle out there. They call it a para electron, and it's got plus or minus para charge. So like some whole new kind of charge the way we were talking about, like the strong force has its own charge. Now I'm badge in a new force with a new charge and a new particle with that force, and it has its own new particle, like the photon. So you have a para electron with its para charge and its para photon. If, however, that new photon and the paraphoton talk to each other a little bit, if they mix a little bit, that can exchange information a tiny bit, then that para electron would look to us as if it had a tiny electric charge. So it would really have its own parrot charge of plus or minus one, but we would see it as having a tiny electric charge because we would only capture a little bit of it through this photon para photon mixing. Wait, I don't get it. So we're imagining a whole new particle a whole new kind of force, and you're saying that maybe that new fours leaks a little bit or interacts a little bit with ours in that it's its own force. But it's sort of to us, it looks like it's like it overlaps with the electromagnetic forces that we're saying a little bit. Yeah, you've got it exactly, that's exactly right. So it has the same strength as electromagnetism, but we mostly can't see it. So we see it as if it was a tiny little version of electromagnetism, like electrons with a tiny charge. Now, why do you need this whole setup to imagine a particle with point o one charge? Can I just imagine a particle with point on one charge? You can? Theorists don't like that. I was reading some papers about that, and theorists always just dismissed that possibility as not very esthetic. I think that they want a reason why a particle would have some arbitrary, tiny little chart rather than just like putting the number in by hand. You know, often theoretical physicists don't like to add parameters to the universe that don't have an explanation, and so they look for a reason why it would have to be this way, So it's a little bit more indirect. But theoretical physicists preferred like sits better in their minds for reasons. Honestly, I don't totally understand. I see they prefer to think about it coming up with a whole new fours in a whole new particle that has a little bit of coupling with the electromagnetic force, rather than just coming up with a whole new particle that has a little bit of an electromagnetic Yeah, that's exactly right, you know. And a lot of things that happen in theoretical physics are guided by a sense of aesthetics, like what would be a pretty way for this to work mathematically? What would give us a beautiful description of the universe? And that in the end is subjective, you know. We like to think about science as objective and based in fact and making progress in lockstep as we approach the truth. But a lot of it really is also a search for beauty and elegance in the universe, and that's kind of controversial. There are some folks out there who think that's misguided. The universe doesn't have to be beautiful and other folks that think that the search for elegance and beauty in our theoretical description of the universe has led to great discoveries. So it's a very controversial approach, but anyway, it's part of the literature of milli charged particles. Now, you said this is one kind of possible millicharged particle, having this whole new particle with whole new force. But then they're the other two that I mentioned, which is like, maybe there are particles with just a little tiny bit of electric charge, or maybe like the electrons we know sometimes have a little bit or a little bit more or less electric charge. And you're saying we're looking for all of these things, or just we're only looking for the new force, new particle model, we're looking for all these things. Is a lot of different experiments searching for these things. Some people are looking for these para electrons. Other people are looking to see if maybe the neutrino doesn't have zero charge, maybe it has a tiny, tiny, tiny charge. Remember, whenever we measure something in physics, it's never exact right. You can't measure something to be exactly zero. You know, we've just set a limit on it, you can say, well, if neutrinos had a charge, it would be less than some tiny value, or we would have seen it. So people are trying to like nail that down. Is it possible that the neutrino might have a tiny little charge. There's a whole broad set of experiments looking for these things. No, I guess, maybe walk us through how do you even look for these things? So first of all, to discover one of these particles, you have to see it by itself. You need to isolate it and demonstrate that it really has its own electric charge, sort of like the way we have seen quarks inside the proton. Right, you can say, oh, maybe quarks have a charge two thirds, but until you see them operating on their own, you can't really say that you have found it. And so we try to do this in accelerators. For example, we smash protons together and we see new stuff that comes out. And everything that's created in the accelerator is immersed in a magnetic field that bends its path. So electrons fly out of the collision and they curve, and how much they curve depends on their charge. So one thing you can do pretty easily is look for particles that bend weirdly in your magnetic field because they have a tiny electric charge, they'll bend a tiny little bit. If they have some huge electric charge, they'll bend a lot. And so that's one quick thing that you can do is just like look for weirdly bending particles created in accelerators. But I guess the hard thing is, like we mentioned earlier, is that the universe is quantum, right, Like, if something has point o one electric charge, that doesn't mean it's going to interact with something that has one electric charge, right Like the universe only likes to make exchange. It if you have exact change, that's right, But some of those interactions are still allowed. Like if you have a particle flying by with zero point zero one electric charge, it can radiate a photon that doesn't violate conservation of charge, and then that photon can knock off an electron in your material can it can it generate a photon, but they aren't photons also quantized. Photons are quantized, but they're not electrically charged. So an electron can generate a photon or this para electron could also generate a photon, wouldn't break any of the rules. Yes, you have to quantize them. You have to generate one electron or two electrons. But having a tiny electric charge doesn't prevent you from generating an integer number of photons. But they would have to be really tiny photons, right like point or one of a photon. Kind of Now, you would still generate one photon, you just have a smaller probability of generating photons. So particles with smaller electric charge generate basically fewer photons, so they ionize material less. This is actually another way people are looking for these things. It might be that we are generating these millicharged particles in our accelerators, but we're not seeing them because they just don't leave a trace in our detectors, which mostly require particles to ionize the material to knock things out of the way as they fly through with their electric charge. So some folks have set up dedicated experiments far away from the collider, like near the collider, but through like meters and meters of rock. They stead of special detectors, hoping that a millicharged particle will fly all the way through that rock, not ionize anything because of it's low electric charge, and then suddenly decay in their detector, and nothing else basically could survive all of that rock. So if they see something there, they'll be pretty convinced they see something that can survive all that rock and also decay into photons, and so probably a particle with very low electric charge. I feel like this gets a little bit into the idea that maybe charge is really or of a probability which we probably can't deep too deep into, but maybe talk to us a little about the other ways that we're looking for these particles. Another way to look for these things is in cosmic rays. A lot of discoveries have been made just by looking at the particles that come from space because they smash into our atmosphere and are basically like little particle collisions that can produce all sorts of crazy stuff and so muans, for example, we're discovered by looking at particles coming from the upper atmosphere. And if you use a cloud chamber, this is just a chamber where the air is super saturated with water, so charge particles flying through it will tend to create droplets, so you can see the path of particles. You might have seen one in a museum sometime. You can see muons flying through it. Well, the drop density, like how many drops you make per centimeter, for example, depends on the charge because it depends on how often you're shooting out photons. And so if you saw a particle flying through there with very low drop density, that would tell you that you have a particle with low electric charge. So people are using cloud chambers to study cosmic rays and see if they can spot some of these very low electrically charged particles cool and how else are we looking for these? There's really fun experiments that are basically the successors of Milican's oil job experiment. They're taking a blob of matter and they're looking to see if there's basically the kind of atom that you were talking about earlier somewhere inside this blob of matter. Like imagine some other particle with a tiny charge orbiting a proton right bound to the nucleus, making some new kind of atom. And if it's also very massive, if this low charged particle has a high mass, it would be like bound to the nucleus and very very close to the nucleus. So people are looking for this like weird kind of stuff embedded in matter, and they theorize that it might have been formed early in the universe. But because these things would be very heavy, they were on Earth, they might have sunk down through the Earth's crust and all have pooled up near the center of the Earth. So you can't just like scoop up a chunk of dirt and look for these weird objects inside of them because they probably aren't any So what they're doing is they're looking for asteroids. They take like a slice of an asteroid and they see if they can find these weirdly charged heavy objects inside an asteroid slice. And they use an experiment similar to Milligans. It's called a leavetometer, where they have like a blob of the stuff magnetically suspended in this oscillating an eclectric field, and they watch the motion of it to see if they can detect something which can't be explained by an integer number of charges, very similar to the oil job experiment. Like maybe there is this kind of new kind of material here on Earth. Is that what you're saying with the new forest and the new particles, is that what you're looking for, You're looking for like regular asteroid rocks that somehow have this new kind of matter somehow stuck to it. Yeah, exactly, maybe deep within it there's one of these things. And they can try to figure out if a huge blob of matter has one or maybe two of these things by oscillating in an electric field and seeing it behaves strangely. It's a lot of details there we don't have time to get into, but the basic version is that you can take a chunk of matter and study its behavior in electric fields to see if it has any of these new weird atoms in it that might have milli charged particles within them. So you're you're basically looking for a new kind of matter, right, yeah, exactly that we had never seen before. And you're wondering, I wonder if it's in this rock or this rock, or how about that rock? Is it in this rock? No? How about there? Yeah that's exactly right, And that seems crazy, but you know, it could be that it's everywhere, that it's in all the rocks, and so might as well check. And so what they can do is they can say, look, oh, well we didn't find it, and so maybe it's just rare, and that they can do bigger and bigger experiments and check more and more rocks. You know, but imagine the universe where they're in every rock and nobody bothered to check. Right, What a crazy discovery that would be. All right, well, good luck finding this magical kind of matter in every rock out there in the universe. I guess we give us a sense of you know, why we're looking for this stuff. I mean, it sounds kind of impossible because we haven't seen it doesn't need to affect the rest of the universe in any strong way, otherwise we would have discovered this new kind of matter. Are we just trying to check the box that it doesn't exist. We're trying to check the box that it doesn't exist, but also we're trying to get a little bit of an answer to the question like why is there charge? And why does it have these properties? Why does it all seem to come in these rational fractions of each other. It's just not something that we understand, and so if we could find this thing, it would be a huge clue. Tell us, Oh, that's not a rule in the universe. It's not required to have that. That's just the examples you happen to discover early on. You know, there's lots of times in the universe when we drew big conclusions based on incomplete information. All of Newtonian physics, for example, is based on not ever seeing things go really fast or not ever seeing space get bent really really hard. So we want to be careful not to jump to conclusions based on the small amount of information we have. We want to check and see if it's possible well to do other things, and that'll tell us like, oh, this is a rule in the universe, or Nope, that's not a rule in the universe. Don't worry about it. I feel that this idea wouldn't really help you, right, Like if there is a new kind of matter with its own force and its own particle and field and everything, and that only sort of tinggently interacts with our that only looks like it has a small electric charge, that still wouldn't help you understand why electrical charges are the way they are, right, It would just open up a new question, like why does it only interact a little bit with this new magical field. But if that other field exists and it does interact with the photon, that means it has some connection to charge itself, and so it would shed some light on the nature of charge. But yeah, absolutely would opened up a whole bunch of other questions. All right, well, stay tuned, and in the meantime, I guess keep driving those electric cards because it's putting those electrons to work. And don't overcharge your credit card. All right. 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 podcast from my heart Radio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.