Daniel and Jorge Explain the UniverseDaniel and Katie reveal the shocking truth about the balance between positive and negative particles.
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Ay, Katie, did we use up all of our electricity puns in the last episode we did together?
I don't know. I mean, you're the one who's in charge.
Yeah, But I'm trying to stay neutral on this.
That's just because you think that puns have such a high potential.
They do, though, they do. They so much capacity for humor in electricity.
It's almost like electricity induces its own jokes.
Let's see, we can get a few more, and it's really down to the wire.
You will find no resistance for me.
Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I'm endless fascinated by electricity and its capacity for puns.
My name is Katie Golden. I host an animal biology podcast called Creature Feature, and I am a particle enthusiast. I like particles, uh so I enjoy learning about them. What's your favorite particle, Daniel?
Oh, my favorite particle? Wow, I feel like now they're all.
Listening to me. Wonder just one?
I guess I gotta go top quark because I studied it from my phdtiss and it's the most massive of all the particles in that way kind of the weirdest.
Oh, okay, Now, which one of the top particles is your favorite? Pick one?
Pick one? Well, that's actually quite hilarious because for my PhD, I studied like six top quarks, like literally or six that we found at the time. But the way particle physics works is that you get more and more collisions. Every year the things ramp up. So folks these days doing their PhD, you have like tens of thousands of top quarks they get to study. Wow, and I have like names for mine. I was like, oh, this is top quark number four. Who I call this number two? Who I call Sally. She's a bit weird, but I love her.
That's it's adorable. It's like the the Seven Dwarfs, except it's the six quarks. Yeah, sleepy grumpy.
I really got to know my top quarks. Well, how about you? You said your pro particle. I'm glad to hear that you're not anti particle.
Yeah, no, I mean I like things existing. I'm pro existence of there being stuff. I like stuff. I like the way that stuff works. I like being able to it's like rainy today, and I appreciate the physics of being able to have some tea. And you know that it's it's just those are the simple things.
Right, Like you're really sticking out a controversial position over there, pro stuff.
Pro existent stuff, pro existence, pro.
Hot and Welcome to the podcast. Daniel and Jorge explain the Universe, a production of iHeartRadio, in which we are pro stuff, We are pro particles, we are pro the universe, and we are especially pro you understanding the universe, because we think that not only is the universe incredible and majestic and kinda crazy and weird, but that it's also understandable that with our tiny little human brains, we can develop mathematical models and intuitive understanding for what's going on out there in the rest of the universe, from the tiniest little particles to the most massive of super massive black holes and everything in between, including me and you and Katie's dog.
Yes, Cookie is a very good physicist because she knows that what goes up comes down when it comes to treats.
When I talk, your dog's name is Cookie, not Biscotti.
She yeah, it's funny. We didn't change her name to Italian when we moved here.
And why is your dog name Cookies? Because she's so.
Delicious it's wow. Well, no, I don't want to eat my canine made out of dog meat. No, No, it's just very very cute. When she was a little puppy, she's very small and cute and kind of cream colored, so she looked like a little biscotti, which is funny because an Italian biscotti is actually just the general term for cookies, like we say a biscotti, but that doesn't really make any sense because it's like biscotti is plural, quick Italian grammar lesson.
And doesn't piscotti actually mean like cook twice?
I think, yeah, I don't know if it just means cooked twice. It really is just a general term for cookies, and it's not necessarily the really hard ones that you have to dunk to actually get any enjoyment out of. It's just any cookie is called a biscato, and you know, any kind of cookie is, you know, like plural biscotti is cookies.
Until somebody invents the next generation of cookies and then they can call it like triscotti or something.
Right right by phosphatest I don't know chemistry stuff, But yeah, let's talk more about particles that are not so visible as the biscotti particle.
That's right, because we're not just here to talk about cookies. We're here to understand the whole universe down to the tiness of the particles it's made out of. And on the podcast we often talk about the mystery of electric charge. What is it? Why do some particles have it, why do other particles not have it? How does it all work? And we usually think about it in terms of the tiniest little individual particles. One is positive, one is negative, one is neutral. But today we actually want to zoom out and ask a much bigger, grander question about the nature of electric charge.
Yeah, you know, I got a fortune cookie message that says you will have an electrifying experience. I'm really glad it meant recording this podcast and not like I was going to need to be resuscitated with those electric paddles.
And it might still happen. I mean, this podcast could be very shocking.
Today we see, well, yeah, see if my heart can take it. But yeah, no, I mean it is interesting, right because like electricity is, it's in everything. It's like in our bodies, the heart rhythm, the cytostism of our heart is determined by electrical pulses our brain activity, Like you are using electricity right now to think for your brain to kind of understand this podcast. But then it's also you know, it is throughout the universe, in everything, in terms of how molecules stick to each other, so it's a very interesting force in that, like, I feel like we kind of only think about it when it's really obvious, like lightning or getting shocked by your toaster. But it is literally almost everywhere. It seems like.
It is almost everywhere, which makes us inspired to think about it. In the grandest sense. We can often learn something about the universe by trying to zoom out by saying, well, what do all these particles make or how do they come together? To determine the biggest features of the universe. It's it's shape, it's topology, all this amazing stuff. So in today on the podcast, we want to start from the little particles they're electric charges, and zoom out to think about the whole universe. And so today in the podcast, we'll be answering the question what is the total electric charge of the universe?
Twenty? That's my guess. It just feels it feels right, It feels like a good number, twenty charge.
You know, there is something interesting about the numerology of the universe. If you imagine like writing down the final equation of the universe or looking at the final numbers in the final theory, you got to wonder, like why those numbers are not some other numbers. You know, there are some numbers that obviously are just human and not important because they have units on them, and we make up units and so anything with the units on it is irrelevant. But you know, if like the final theory of string theory that explains the universe has like a three in it or eleven in it, then you got to wonder, like why that number is the universe somehow eleven ish?
Right?
M Yeah, it does have kind of an eleveny feeling to it. I think that makes sense.
That sounds like a delicious name for a cookie.
Eleven E sounds like eleven to cookie. So I guess, like when we're talking about like total electric charge, like I don't even know where to start really, because it's like, I mean, it could be positive, it could be negative, it could be neutral. I don't know if they're like if this is something that even could have a number, right, Like, if it's a positive charge, could it have a positive Is twenty even a possible answer?
Tony actually is a possible answer. But we're gonna see that there's a lot of sort of assumptions built into this discussion about what's natural, what makes sense, what numbers we would sort of accept, what numbers need explanation, and what numbers don't need explanation, And so these kind of questions I think are fascinating because they reflect not just our understanding of the universe, but our attitudes about it, are our biases, our presuppositions about what kind of answers make sense. So I was wondering, as usual, what people thought about this question before we dove in. So I went out there and I asked our group of volunteers what they thought about this question. If you'd like to join this not very illustrious, but very enthusiastic group of volunteers, please write to me at questions at Danielandhorge dot com. So think about it for a moment before you hear these answers. What do you think the total electric charge of the whole universe could be? Here's what people had to say.
I would say zero, so that all the charges eventually equal out. That would seem nice and symmetric. But since that's almost certainly not the right answer, I'm gonna go with plus five electron vaults.
Well, I know there's a law of the conservation of energy, so I guess it probably depends on what the charge was of all the energy that existed during the Big Bang. Given that Daniel and Jorge are explainers of the universe, there are two people, and they're both very positive. I'm going to say plus.
Two the electromagnetic field, as far as I understand it can be thought. I was covering the entire universe, and I don't see why that would have been created with a non zero value. So I'm going to say the overall electric charge is zero.
Shouldn't this be zero because all this symmetry of particles and charges and the words for maximizing entropy, is this emulated? I have my dear.
I feel like the net electric charge in the universe must be zero, but that's probably not correct.
I want to guess that it's the same as a single electron, only because if every electron is just an expression of the excitation of a single field, then that whole field represents the charge of a single electron. Oh man, Daniel, I don't know, sounds good.
I love the answer. That's like it seems like it should be zero, like neutral, But knowing that the universe is weird, it's probably like five.
That was basically your answer, right. I think that makes a lot of sense. That basically sums up.
This is typically what I learned from these these recordings with you, is that it's like, well, it seems like it should be something really like neat and precise and tidy, and then it's something like five point seven units of physics.
It's true that the universe is chock full of surprises, and the way that we think things should work isn't always the way things actually work. But I think this already raises that really fascinating issue. Like if I told you the answer was zero, you'd be like, cool, that kind of makes sense, and you might not even need any more explanation because zero is just like a natural answer. But if I tell you the answer is five, then you're like, well, why five? Why not four? Why not seventeen? Right? Then it needs an explanation. It tells us something about the kind of answers we're willing to accept about these deep questions about the universe.
I'm not anti math, but I'm not, like, I don't think is a natural thing for me, and certainly not like the kind of math required to sum up all of the charge of the universe. Which sounds very time consuming. How would you even go about, like, what is the mathematical process here? We're hopefully not counting the atoms and their charges and just summing them up, because that seems like it would take a whole afternoon.
Yeah, that's exactly what we're doing. What when we talk about the total electric charge of the universe, we really just mean put all the protons on one side and all the electrons on the other side, and count them up and add it all up.
It sounds like doing taxes.
Yeah, exactly, we're doing the accounting of the universe. It's just one big Excel file. Actually, that's the way the universe works. It's it's just a big Excel's bridge.
Oh god, that's the darkest outcome.
But you know, that's really how we define things. The charge of an object is the sum of the charge of things it's made out of. Like if you have a cloud of hydrogen gas, it's made of protons electrons, one proton per electron, so the whole cloud is neutral. If you added like one proton in there without an electron, then the whole cloud would have an overall positive charge. So that's really fascinating because the charge of an object really is just the sum of the charges. There's nothing else going on in there. It's very crisp, very clean to calculate the charge of an object.
So I noticed in a lot of the answers, which I also kind of understand and agree with, that there is this and what you said earlier, which is there's this comfort with the idea of it being zero because that seems balanced, right, Like this intuitive feeling that there should be for every positively charged particle there should be a negatively charged particle that they're for every proton there should be an electron. Essentially, Why do you think there is this assumption which I'm not necessarily disagreeing with. I just think that's interesting saying that that's that is a comfortable stance for people to take. Like, what is it about that neutrality that we like so much?
Yeah, I think that's a great question and a deep one. I think it just reflects our biases, you know. I think we like to imagine that the universe makes sense, that it runs on laws, and those laws are reasonable and they make sense, and that they're not arbitrary, and having the overall universe have it's sort of just an arbitrary number for its charge. It needs an explanation, you know why eighteen? Why sixteen? And it takes a sort of different philosophical approach to ask, like, well, doesn't zero also need an explanation, Like if you have exactly the same number of protons and electrons in the universe, doesn't that also need some explanation. It's sort of an amazing coincidence. Anytime you see a coincidence in nature, you wonder like, hmmm, is there a reason for that? Is there some underlying process we're not aware of that's making that happen. And sometimes it does, and sometimes it's not. Like you know, there's a huge coincidence in our sky, the Sun and the moon are almost exactly the same size in our sky, which makes for very dramatic eclipses. Is that a coincidence? Yeah? Absolutely, there's no reason why the Sun and the moon should be the same size at all. Like, they're very differently sized objects, very different distances away from the Earth. It's just a literally cosmic coincidence that they balance each other in the sky and appear to be the same size. Other times, we think that there might really be an underlying reason why the universe would have some cosmic coincidence. So in the case of its total charge, we're just adding up the protons and the electrons and counting them. And I just want to go back to this for one minute, because I think it's kind of amazing that you can calculate the whole charge of the universe just by adding up its bits, because you know that's not true for other stuff, like for mass, right, you can't just say, well, what's the mass of the universe. I'm going to add up the mass of all the quarks and the electrons. Because we've talked about lots of times on the podcast, like the mass of the proton is not just the mass of the things it's made out of. There's also energy in its bonds which contributes to its man So mass is much more slippery of a concept than electric charge. Electric charge is incredibly crisp and clean, and so you actually can measure the electric charge of the universe on an Excel spreadsheet. It's really just very simple map, but the numbers are staggering, Like how many protons are there in the universe is something like ten to the eighty protons in the universe, And that's of course, just the observable universe, just the part that we can see and interact with, and that life has had enough time to travel to us since the origin of the universe. We think they're like ten with eighty zeros after it protons in that chunk of the universe. What lies beyond, of course, we can't know.
Yeah, this seems like the trickiest part, right is obviously we cannot have a bean counter go throughout the whole universe counting every single electron and proton, but we would need to sort of, you know, almost like average out like what our expectations are, like, take a slice of the universe, figure out like if it's a representative sample of the universe, and then scale that up or something. I don't even know. Look, I'm thinking in terms of sort of like biology studies and statistics and stuff, but I don't even know if those kinds of things work for the universe, right, because you could have you could take a reasonably large slice of the universe and try to assume it's a representative sample of the whole universe. But you know, then you could have an entire, massively large area of the universe where you know, the density of stuff, or there's a presence of a black hole and things are completely different.
No, this is a really good point, and I think that fundamentally we need to talk about the universe as a whole, even beyond what we can see, because imagine the universe is infinite, right, it's still possible that it has an equal number of electrons and protons, that the total universe charge is neutral. But then you know where any individual particle is going to be is going to be a little bit random. So if you take an observable universe scoop of that infinite universe, you could take lots of different scoops one here, when they're one exactly where we are, you might get exactly the same number of electrons and protons, but that's actually quite unlikely. You're very likely to get a slight difference in the protons and electrons. For any random scoop. Overall, they would average out, but any observable universe scoop would probably have a very small difference. And that's not something we can practically measure, because, as you say, you have to go touch every proton and every electron. But we can think about the overall universe and we can extrapolate from what we've learned about the laws of physics and what we've observed about the behavior of charges in our scoop to think about what the overall charge of the universe is.
Okay, so it's all about sort of trying to figure out some underlying rule that we might be able to safely assume applies to the rest of the universe, rather than trying to get sort of a representative sample, like we are looking for something that seems like a consistent rule that should apply and scale up.
Yeah, I think we can actually do both. We can think about what would make sense, what the rules of electricity and magnetism are, and whether we think the universe should be neutral, and then we can do our best to go out there and look to see if that actually works, look for any evidence of deviation from that, see if we can find hints that we could be wrong about the nature of the universe.
Okay, well, I'm going to go get my big old chalkboard on wheels, do some goodwill hunting style, like suddenly I'm good at math inexplicably, and then maybe I'll come up with the number. But we'll take a quick break and We'll see what Daniel thinks of that number I come up with.
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So, Daniel, I did some I just wrote some random fractions, but I'm not really getting anywhere. I think that I need more stuff to work with here in my math exploration, because this is the thing, like with theoretical math and theoretical physics, I have such a hard time understanding where one even begins to try to understand, like I would assume perhaps for this like there would be some you would start with some like experiments to see if there is some kind of rule that it's consistent in terms of the average charge of a system and.
So we can start theoretically and think about like how electromagnetism works. And as you say, thinking about the rules is really important because it helps us understand like, also, can the electric charge of the universe change? Is it possible for it to go up and down? Because if it is, then it's very difficult to imagine the electric charge of the universe is zero, or even to know what the number is. But something that's super fascinating and super important about electric charge, and the real clue that it's deeply fundamental to the nature of the universe and matter itself, is that electric charge is conserved. That means that the total electric charge we think can never change. Whatever that number is. Add up all the pluses and all the minuses, and you get some number zero or seven or whatever that cannot change. Is no physical process in the universe that can change that number. There's a wrinkle there. It doesn't mean you can't create and destroy charged particles, right Like you can have a photon which has no charge, and it can turn into an electron and its antiparticle the positron, so that you have created new charged particles. But you created a plus one and a minus one so the total charge hasn't changed photon of a zero the positron electron pair total charge is still zero. So that kind of stuff can happen. You can create and destroy charge particles, but for some reason, the universe doesn't let you just make an electron or just make a positron. You have to keep those charges balanced.
Interesting, So when I rub my feet real fast against the carpet, I'm wearing socks, and I have changed my charge slightly, and so I assume though then I have potentially also changed the charge of the carpet or something, right like, It's not like I don't just produce a positive. Well, actually, I guess I don't know what my charge is. Once I rubbed my socks real fast against the carpet. All I know is that I have changed my state somewhat so that when I touch a doorknob, I get a little zapp. But my assumption is that this is not coming out of nowhere. There's some exchange happening exactly.
That's a really deep insight right there, that if something is conserved, then there has to be a current of it that in order for you to get some of it, it has to come from somewhere. It has to flow. So if you're going to get a bunch of electrons, you can't just create them from nothing. They have to come from somewhere. Somewhere else has to lose electrons. If you're going to gain electrons, or more specifically, if you're going to gain negative charges, something else has to gain positive charges, either by losing electrons or creating positrons or something. So this is like a conserved current in the universe. You cannot just create charge out of nothing. If you're getting it, it comes from somewhere, and that tells you that it's like deeply ingrained in the nature of reality itself. And there's lots of things in the universe we see are almost conserved, like energy is mostly conserved, and this is hard for people to grasp because they think of that way of energy, that energy has to come from somewhere and go to somewhere. But actually we know that energy increases in the universe as it expands, So energy is oldly concerned, but not actually it's not an exact symmetry or conservation of the universe. Same with lots of other things we talk about, like left don number or other symmetries we have in particle physics, but this one is exact. This one in the universe will never ever let you violate. It's like down to the wire. It will not give an inch on charge conservation.
I don't want to go on a tangent. But you said that the energy increases as the universe expands.
Yeah, energy is only conserved if space is constant. But if space is expanding, then it's creating more space, and that new space always comes with energy built in. It's like the dark energy of the universe. So the total energy of the universe is actually increasing if space is expanding. We have a whole podcast about that.
It's really fun, that's really cool. Yeah, I'm gonna listen to it.
But that's not true for electric charge. And I want to disentangle two concepts here. We're talking a lot about particles and antiparticles, and it's true that if you make an electron, you also have to make its antiparticle. But charge conservation is not the same same thing as like matter conservation or antimatter conservation. Matter particles can be positive or they can also be negative. Antimatter particles can be positive and they can be negative. So for example, electron we call matter and it's negative. Proton we call matter and it's positive. Antiproton would be negative anti electron, the positrone would be positive. And it's a whole other question about like matter antimatter symmetry in the universe. Like we think that the universe treats matter and antimatter almost exactly the same way, but not quite right. But charge conservation is a different thing than matter antimatter conservation matter antimatter is another example of one where the universe is almost conserved, almost symmetric, but not exactly. But charge conservation the universe respects exactly.
That's so interesting. It's like it makes it feel like like electricity in charge is like much more. I mean, I guess everything is fundamental, but it's like that this is like the sort of one of the you know, most fundamental aspects or causal aspects of the function of the universe.
Yeah, it seems like a deep clue about the nature of reality itself. And you might ask, like, well, where does it come from? Right, why is it this way? What does it tell us about the nature of reality? And about one hundred years ago, a mathematician Emmy Nuther told us that everything that's conserved in the universe, anytime there's a quantity that doesn't change, like momentum, is conserved. In a similar way, it tells you about some symmetry in the universe that every conservation law, like conservation of electric charge or conservation of momentum, comes from some symmetry. And that's a Nuther's theorem that every symmetry leads to a conservation law. If there's a symmetry, means some quantity is conserved. In the case of momentum, the reason momentum is conserved in the universe is because there's no absolute location in space. Every place in the universe has the same laws of physics. We think, it doesn't matter if you do your experiment here or somewhere else, or an alpha centauri, like, the fundamental laws of the universe are the same. It's called translation invariant. And you do a little bit of math, and out of translation of variance comes conservation of momentum. So then you might ask, well, what symmetry is it that creates conservation of electric charge? Why do we have that? What does it tell us about the universe? And it's a little bit mathematical. It tells us something about the phase of the electromagnetic field. The electromagnetic field are these numbers that feel all of space, right, and like do you have an electric field here? Do you have a magnetic field here? But those numbers also have directions, like everywhere in space. The electromagnetic field isn't just a number, it's an arrow. It points in a certain direction, and the phase of that arrow, like which direction it's actually pointing in, turns out to not really matter. You can change that without changing the dynamics of electromagnetism. And so it's a little bit mathematical and abstract, but this is the quantity whose symmetry leads to conservation of electric charge. And actually there's a whole set of these symmetries, of these fundamental fields of the universe that lead to conservation life. We have an episode about these gage symmetries and how they lead to conservations and how they're really deeply fundamental to the way the universe works. So it's a little bit abstract, but the conservation of electric charge is telling us something about the nature of the electromagnetic field and the symmetries of that field.
If you changed the direction of an electromagnetic field. Would that have an impact on the direction of other electromagnetic fields or would it just simply change direction and have no impact on anything else.
It absolutely would have an impact if you didn't have photons. So photons are the things that actually preserve this symmetry. Without photons, you can't have this symmetry in the universe. Photons like zip around transmitting this information about the direction of electric field changing from here to there. You can actually deduce the existence of photons just by saying I want an electromagnetic field and I wanted to have this weird particular symmetry. For that to happen, you have to have photons. And so that sort of like explains why we have photons, why we have forces. In general, all of the forces are actually there to preserve these symmetries. So it's a really fascinating and deep new way to think about the nature of forces. Encourage everybody interested in this stuff to check out our episode about gauge symmetry. But this tells us something about the nature of electric charge, but it's still not something we really understand. Like we kick the can down the road a little bit, we say, okay, so charges conserve in the universe. Why well because of this other weird symmetry of the universe. Why does it have that other weird symmetry. We don't know. That's just like something we observe, and this is the process of science, right, We're like, why is this oh because of that?
Well?
Why that? Oh?
Because of this other thing? Well why that other thing?
Right?
And so we're sort of at that stage and we're like, we don't know what that really means, but we do think the universe preserves it.
Yeah, I mean that's interesting. I think it's also interesting the sort of way you phrased it, which is that like photons are here in order to maintain this neutrality or this conservation. And look, I'm totally here for the ride, so I believe you. But I also think it's interesting that, like, uh, I think that sometimes, like we have as humans, we are extremely causal, right, Like we love a thing that like had like this causes this, right, X causes why I push a ball, That's what causes the ball to roll down the hill. I wonder if like if you know there's something I mean, it's it certainly seems like everything is interlocking in this extremely precise way. But it's like, well, could one option be like everything sort of happened all at once, right, like in terms of like everything maybe interlocking, but one thing doesn't necessarily cause another thing. Or could it be like that you have this fundamental rule about charge being conserved and then somehow, like photons became this like uh, I mean in biology, it's like called spandrel where it's like this thing that doesn't at least initially have any purpose, but it is just because of the structure of the organism. This structure has to exist. Like an architecture, you'll have a spandrel being like a section of the wall when you have an archway like that is sort of between the rectangle of the opening and then the arch. There's like those little kind of like curvy pizza slices which are the spandrels, and they don't actually serve any structural purpose, but they just have to exist because the arch is there. And so like I find that kind of interesting of like how do we, like, what are some of the ways that we think about these Like could photons just obviously we have use for photons now and they fit in with everything in all the other particles in the universe, But just like, are these things just happening because of some fundamental rule basically forced everything else into place? Or did everything just kind of into place all at once? And now my brain hurts.
Yeah, we don't know the answer to that question. We're struggling to figure it out. We think that maybe understanding the nature of reality at a deeper level, you know, quantum gravity, that might explain where all of these fields come from and why we have them and why they have these symmetries could help us understand why this exists in our universe. And there's some people exploring theories that suggest that maybe charge isn't conserved, like maybe it's almost conserved ben we've never seen it be broken, but at some very tiny level, like very very rarely can be broken. And most of these theories suggest that our universe exists in higher dimensions, that like it's more than just the three dimensions of space plus one dimension of time that we're used to, but that it's like five dimensional or six dimensional or ten dimensional or whatever, and that maybe it's neutral in that ten dimensional space, but in our like four dimensional subspace, maybe it's not. You know, if you imagine the whole universe is neutral, but you have like a random slice of it, then articles can move in and out of that slice, and that would look to you like charge is not conserved. There's no data to support these ideas, but it's the kind of thing people are thinking about. You could create charge non conservation in our universe by sort of expanding the concept of the universe to something with more dimensions in it. But if the universe does respect charge conservation, that means that the total charge of the universe now is the same as it was a minute ago, is the same as it was an hour ago, is the same as it was a billion years ago, Which means that to figure out what the charge of the universe is today, we only need to think about what the charge of the universe was at the Big Bang or when it began, right, and that will tell us what the charge of the universe is still today. And that relies really crucially on the charge never changing. So that's why that's such an important part of this argument.
Well, I'm excited to see a video of the Big Bang, which Daniel clearly has, but let's take a little bit of a break. So I can hydrate. Butfore my mind is and then when we get back, Daniel's going to explain exactly what happened during the Big Bang, leave no detail undescribed.
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Now, all right, Daniel, you promised, you promised this big Bang? What happened there? What was up with that?
I think you may have overstold this maybe a little bit, So you're right that The argument is if we know the charge of the universe when it began, then we know the charge of the universe now because it hasn't changed. So do we know the charge of the universe when they began? Well, do we know how the universe began? Unfortunately we don't, right, and people think about the Big Bang, is this moment fourteen billion years ago when the universe began? But really things are much fuzzier than that. What we do know is fourteen billion years ago the universe was in some very hot, dense state. We know that because we see how the universe is progressing over time. The further back we're looking in time, so we can see the history of the universe. It's literally written in the night sky.
This is because light takes time to reach us, and so we know based on the distance that it was, like if stuff is closer, it's coming to us more recently in time. And if stuff is further away. It's coming to us further back in time.
Right, light from that direction is arriving now. That left a long long time ago. So the images we are seeing when we look really really far away are in the deep, deep past. And what they tell us is that the universe is getting colder. As it gets older, it gets more spread out, more dilute, it gets chiller. And if you run that clock backwards in time, then the universe is getting hotter as you get backwards, and more dense. So the universe started in some very hot dense state and then spread out over time. And people often think of the Big Bang as some dot of matter spreading out into empty space. But the more accurate picture is that the universe was already infinite, already filled with an infinite amount of hot dense stuff everywhere, and the Big Bang is the expansion of that space, space being created between those particles spreading out to make those things colder and more dilute. That's our picture of the Big Bang, and that's as far back as we can go. Our theories of physics work really really well back to that hot dense state, understanding how it expanded and cooled and formed stuff. Kittens and ice cream and lava and hamsters and all that good stuff before that. We just really don't know.
They don't mix particularly well those things anyway.
Kitten ice cream, oh my gosh, really.
And hamsters they don't love lava.
You could put a nice biscatti right on top of that scoop of kitten ice cream perfectly. You should name your kitten cookie instead of your dog. But the point is that we don't know where that came from, right, And so there's ideas, you know, it could be that it caid from some other unknown field like the Inflanton field, or it could be as a bubble of exotic stuff which turned into our universe. We don't really know. And here's where we get sort of like philosophical, and we say, well, probably it was born and neutral, because what else makes sense?
Well, so if it's if we know it was super hot and dense, is there something about heat and density that could like tell us about the charge, right, Like do we know like if when when we have really hot dense stuff, do we know the charge of those things? And like could we somehow extrapolate like what is the likely charge of like the it's like super super soup of the initial universe.
Yeah, so here's where we get into the evidence. The only theoretical argument we have is the universe should be neutral because it only makes sense for it to be born neutral, and we're pretty sure that if it was born neutral, it's still neutral. Well, do we have any evidence to back that up. We can't actually look at pictures from the very very early universe and look for hints to see if there was any overall positive or negative charge, because that really does affect how things oscillate. So the oldest images that we have, the earliest measurements we can make of the early universe, are from about three hundred and eighty thousand years after that very very hot, dense state. That's when things cool down enough that like protons and electrons started to hang out together into neutral atoms, and then the universe became transparent. Before that, it was hot and dense and opaque like the center of the sun. After that moment became more transparent like the air which let's light through. So we can still see light from that last moment of opacity still shining around the universe. That's the cosmic microwave background radiation. We talked about a lot on the podcast, and by looking at patterns in that light, we can tell how that gas or how that last moment of plasma was oscillating, was slashing around. We see all sorts of cool patterns in that plasma that tell us like how much dark matter there was in the universe, how much normal matter, how many photons. The imprint of the ripples and the cosmic microwave background radiation are an extraordinarily precise way to understand the dynamics of that early plasma, and we can actually use that to answer the question of whether there was any overall charge very very far back in the early universe.
Oken So, how do we look at the charge of this sort of background radiation that we can actually observe on Earth.
Well, the lucky thing is electromagnetism is super duper powerful, Like it's so much more powerful than gravity that if there was any positive charge or any negative overall charge in those clouds of gas, we would see it because it would overwhelm gravity. Mostly when we look at the cosmic bac roway background radiation and use it to think about like the sloshing and the oscillation of that gas in the early universe. We see gravitational effects. We see dark matter pulling it in, We see particles passing through each other. We can think about the acoustic waves of pressure in that gas, so we can see the gravitational effects. If there was any charge left over, any positive or negative, we would see a really strong effect because it would overwhelm all that gravity. And yet when we look at the data, we only see gravity effects. We see no indication there that there's any positive or any negative charge in the early universe.
Clouds of gas that would indicate that maybe it is zero right, that it's neutral.
You can't actually pin it down all the way to zero. You can do is set a limit and say, look, if there is an excess of protons or electrons, it's got to be a tiny fraction, because if it was any bigger, we would have seen it. And numerically what that means is that, like, if there's an overall positive or negative charge, it has to be less than one part in ten to the twenty nine, which means like for every ten of the twenty nine protons, there's ten to the twenty nine electrons plus one.
I may not know math, but I know that that's tiny. That's very small.
It's very small.
If you put that in like as like a thing, I couldn't see that thing.
That's true, it is very very small. It's not exactly zero, and ten to the twenty nine is a big number, but it's actually small compared to the total number of electrons and protons, which remember is like ten to the eighty. So it's possible that the universe has a slightly positive.
Or negative actould be infuriating, that would be so aggravating.
And it could actually be that they're like ten to the fifty more protons than electrons in the universe, which would still be a tiny fraction of the ten to the eighty protons and electrons in the universe. So that's what we can learn from the consic microwave background radiation. But we can keep fast forwarding in time for the universe and look for effects in other dynamics, other structure that was formed in the universe. That's actually a little bit more precise.
Okay, I like this because I hate the idea that we would just leave it at like it could be zero or maybe you know, ten to the twenty ninth ish, we don't know.
If you want to definitive answers, cosmology is the wrong place to look. So what happens next in the universe, the protons and electrons have formed together to make hydrogen, then that hydrogen fuses together very briefly, like we're used to thinking about fusion happening at the hearts of stars, which formed hundreds of millions of years later. But for a couple of minutes in the very early universe, things were hot and dense enough that hydrogen could fuse together to make heavier elements. It's like, briefly, the whole universe was like the heart of a star. So that hydrogen made some helium and very trace amounts of lithium. It didn't last long enough to make anything heavier than that. And the rate at which that happens tells us a huge amount about the nature of reality at that moment, Like we can measure the density of the protons at that moment by the ratios of like how much helium was made and how much lithium was made. Because fusing two protons together is really hard. You got to really push them together with a lot of force. You need a huge amount of density in high temperature because protons don't like to get together. They're both positively charged. They were tell each other. So you can learn a lot about the density. And this is really precise science called Big Bang nucleosynthesis that tells us a lot about the nature of the universe back then, just by measuring these ratios, the helium to hydrogen to lithium ratios, and it also tells us about the positive and negative charges, because if there was a bunch of extra protons flying around, that would really change the rate of fusion, or if there are a bunch of extra electrons flying around, because again the electric force is really powerful and it would disrupt or enhance the rate of the production of these heavier elements in that moment. So by measuring these ratios, we can get a limit on the total electric charge of the universe now to one part inten to the thirty two So it's like a thousand times more powerful than the limit we get from the costaic microwave background radiation.
Okay, so intellectually I understand this is amazing and that the science behind this is I mean, it's incredible right to be able to do this kind of like deduction and to do this calculation to this level of precision, and that ten to the thirty two is a lot more than ten to the twenty ninth because that is the nature of exponential growth. And yet to my little monkey brain, I'm like, these numbers are essentially the same, and I like, it's just real small. But the uncertainty is still there. It's just real small.
No, that's fair. I mean, on one hand, these are very very precise studies, really incredible that we can learn this much about the early universe from this trace information. And on the other hand, it's nowhere near getting us close to zero to understanding, you know, whether the universe is actually overall neutral. But we can do even better. We can look in the modern day universe to see if there are currents flowing in the whole universe, Like if the universe had a bunch of positive charge here, a bunch of negative charge there. If there was an imbalance in the protons and electrons, that would create huge electric fields throughout the whole universe, just the way like electrons and protons can create electric fields in the atom, or in materials or between like your sock and the floor. If you have an overall excess of electrons or protons somewhere, which you'd have to have if there was an imbalance, then you'd have electric fields, and we think we could see that because those electric fields would steer cosmic rays. Cosmic rays are just charged particles that hit the Earth like tiny little asteroids like protons or sometimes heavier elements hit the Earth, and we can measure them in our atmosphere and using all sorts of cool technology, and by studying the patterns of those cosmic rays, we can use them as probes of these cosmic electric fields and try to figure out whether there is an overall positive or negative charge to the universe.
Okay, that I mean, that makes sense, right, You've got if you have an imbalance, that would cause this sort of like sloshing of fields, and then we would see that from here in cosmic rays that we receive.
Yeah, and we've studied these cosmic rays. They're super interesting for lots of other reasons, like what's even making them, how they get such high energy. The patterns of them in the sky are very strange. We've analyzed them carefully, and there's no evidence for an overall positive or negative charge of the universe from cosmic rays. And we can set a limit of one part in ten to the thirty nine, So this is jumping up like seven more orders of magnitude, improving this result by factor of ten million. I hope that impresses you, Katie.
Look again, intellectually, this is incredible, nothing but respect for these scientists. And I understand that it is significant that we keep increasing the precision of this estimation, meaning that it looks more and more like it could probably be zero or neutral. And yet you know, again there's a little uncertainty, and the part of my brain that is still a monkey does not like it.
Well, you're right, we still don't actually know the answer, and that's about as good as we can do so far. We have other ways to look for electric fields, like to look at the gravitational structure of the universe. You know, if galaxies were overall positive or overall negative, it would change the way they pull and tug on each other, the way they move in galaxy clusters. And that's a powerful way to look for excess charges, but it's not as powerful as the cosmic ray limits. So those are our best measurements so far about the overall neutrality of the universe, about one part in ten to the thirty nine, which is only like, you know, forty orders of magnitude away from having a definitive answer to this question.
I feel like at a certain point it's going to be less of a math problem and more of a problem to solve in therapy or I learned just to accept uncertainty.
Well, I think this is a really fascinating question because we have a very strong answer from the theoretical side. There's a very strong bias that says the universe should be neutral when it was created, because again, no other answer makes sense, and that's really just very philosophical. There's no like, very strong theoretical argument there other than just like a preference for zero is the most natural answer if you have to pick one. But then the theory tells us that once you picked one for the early universe, once you create a universe, its charge is fixed. That will just never change. And that's really cool experimentally because it means we can measure the charge of the universe anytime. We can measure it today. We can look for evidence in the early universe. We can look for a thousand years after the universe which created We have lots and lots of opportunities to make these measurements. So far, these measurements tell us that the universe is mostly neutral down to about one part in ten to the thirty nine, which I think is pretty good, but Katie's unimpressed. Maybe one day we'll come up with another technique that lets us push these measurements even further so we can get a deeper answer to this question.
Yeah, I mean, you know, And it's also a good lesson, like, think real hard before you create your own universe, because once you pick that charge, you can't change it later.
That's right, you are literally stuck with it. There's no changing the electric charge of the universe. But that's also not something we understand, right, we don't understand how the universe has made or what it's charged was in the beginning. We also still don't really understand why charge is conserved. This, again, is just something we've observed. We've done a zillion particle physics experiments looking for violation as this rule and never seen one. That doesn't mean that it doesn't happen occasionally, Right, We have these theoretical reasons that suggest that photons exist to preserve electric charge, but again, we don't really understand why that is. And so it's possible that sneakily the universe is changing it's little bits of charge here and there, very occasionally under our noses.
My therapist is going to be so confused when I talk to her about like and then Daniel said that we can't know if the charge doesn't change. I don't know what to believe anymore. Who do I trust?
I think you should just sit with your dog Cookie and have a nice cookie and you have the therapy right there.
That is the best theraapy, the byicookie therapy.
All right, Well, thanks everyone for joining us on this exploration of the nature of the universe, not just its size, not just its structure, but it's overall charge and what that tells us about the nature of reality and what's important to the universe. For reasons we still don't understand. The charge seems to be a fundamentally conserved quantity in the universe, but we still don't actually know what the total charge of the universe is. Thanks very much Kennie for joining us today, and thanks everybody for listening.
Yeah, thanks for having me.
Tune in next time for more science and curiosity. Come find us on social media where we answer questions and post videos. We're on Twitter, Discorg, Instant and now TikTok. Thanks for listening and remember that Daniel and Jorge Explain the Universe is a production of iHeartRadio. For more podcasts from iHeart Radio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. When you pop a piece of cheese into your mouth, you're probably not thinking about the environmental impact. But the people in the dairy industry are. That's why they're working hard every day to find new ways to reduce waste, conserve natural resources, and drive down greenhouse gas emissions. House US dairy tackling greenhouse gases. Many farms use anaerobic digestors to turn the methane from manure into renewable energy that can power farms, towns, and electric cars. Visit you as dairy dot COM's Last Sustainability to learn more.
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