Daniel and Kelly’s Extraordinary Universe - Was the Big Bang left handed?

Episode Date: February 4, 2025

Daniel and Kelly dive into the left-right asymmetry of hands, life, particles and the Universe itself. (This version was edited to reflect that 2d space has handedness and methane is non-chiral.)See omnystudio.com/listener for privacy information.

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You have to look very carefully at all the clues, you have to pull really hard on any thread that looks weird as unexplained, because any of them might be the key that solves the whole mystery. Throughout history, whenever we've seen something we didn't understand, it's often turned out to be a big screaming clue about the next deeper layer of understanding reality. When we saw patterns in the periodic table, they were obvious but unexplained for many years Until we were able to dig deeper and discover that they all came out of how electrons arranged themselves in shells around the nucleus.

The similarity of the shape of the coastlines of Africa and South America? A big clue that over millions of years, the continents themselves were in motion, and these two had once been joined. So amazing realizations can come from refusing to ignore little tiny clues that bother you at night. So every time we see something that doesn't make sense, we should dig deeper. and look for a reason. And that's especially true

when there's something that we don't understand about the whole universe. When we think it should has balance, but instead it's out of balance. Why is there more matter than antimatter?

Why are some forces weaker than others? Particle physics is filled with these kinds of mysteries. And today on the podcast we'll be digging deep into one unexplained choice the universe seems to have made billions of years ago

between being righty or lefty. Life is left-handed. Particles prefer to be left-handed, though most humans are right-handed. Today on the podcast we'll be asking, was the Big Bang also left-handed? Welcome to Daniel and Kelly's extraordinary left-handed universe. Hello, I'm Kelly Weiner-Smith. I study parasites, and my family is 50% left-handed and 50% right-handed. Hi, I'm Daniel. I'm a particle physicist, and I'd give my right hand to be ambidextrous. Well, okay, that doesn't really make sense, the more I think about it. But I would love to be ambidextrous, too. How does it fall out in your family? We have one lefty, a bunch of righties, and my mom was ambidextrous. She could write with both hands.

And something she'd like to do with her left hand, like cutting with scissors and other things. she likes to do with her right hand like stirring a bowl of soup interesting i don't do anything with either hand well like pipetting didn't go well my writing's illegible from either hand but you know i can type okay and who in your family is left handed zach and we think ben so zach's a member of the secret society of left handers and the secret society of redheaded people yes so he's involved in lots of secret societies he's maybe in charge of everything i wouldn't mind having cartoonists be in charge of most of I think that would be a great way to run the world. What's the name for that?

You have democracy, oligarchy, cartoonocracy. Yeah, I don't know. But I can tell you that he doesn't run the household because he might not be competent to do that. And so I don't know that we should give him too much more power. And I don't think he wants more power. So I think maybe rule by the cartoonists, this one in particular is maybe not a great idea.

What would it be like if the world were ruled by physicists? We would spend a lot more money on particle colliders. Oh, my gosh. Yes, we would know so much more about the universe. But we'd spend less money on soap. Sorry. Fair, fair. Nobody in office would be wearing a suit, that's for sure.

That's for sure. That's a world I can get behind. Well, we seek to find balance between the physicists and the cartoonists and the left-handers and the right-handers and everything in the universe, which is why on today's podcast, we're going to be talking about symmetry and balance and imbalance in the universe. So I'm super interested in this topic

because I only had a chance to sort of like realize that it existed back when we were writing Soonish, because we wrote a little note of Bene on George Church, who is trying to make organisms where every one of their molecules is the opposite-handedness as it is now. And the ultimate goal, as I understood it, was that if you had a human of opposite-handedness, no pathogens or parasites could recognize our receptors, and they would never be able to infect us.

And so you would be free from all infection, but... You also wouldn't have a microbiome, so you couldn't digest any food, right? So your microbiome would also have to be made opposite-handed, and then all of your foods would have to be made opposite-handed. And that just seems like way too much work for the trade-off. and also like if a global supply chain problem popped up because you never feed anyone because they need the opposite handedness bread, it was complicated. But I remember when I was doing the research thinking, why is there such a trend in handedness for molecules?

Like what caused that? And then I got too busy. And so I never dug in. And today we get to find out about that. That's right. It's always super fascinating when there's an asymmetry in the universe, when the universe seems to have made one choice because then you've got to ask like, why not the other choice? What does it mean?

Is it random? Is there a reason? And could it have been the other way? Are there other universes out there where another choice was made? And does that explain my whole childhood, basically? Wow. Whoa, it got deep. And so this stretches from the mathematics of handedness to the handedness of life,

to the handedness of particles, and even the handedness of the whole universe, and the origin of the universe itself. So I went out there and I asked folks what they knew about this topic, if they thought the Big Bang could have been left-handed. If you'd like to play for future episodes of the podcast, please don't be shy. Write to us two questions at danielandkelly.org. So think about it for a moment.

Do you think the Big Bang could have been left-handed? Here's what people had to say. Okay, this has to do with chirality, but I don't think chirality is at the fundamental particle level that would be manifested there. it's, you know, because you've got flavor, spin, charge, flavor, color, but you definitely don't have chirality built into the core properties. Now, it does come up in chemistry.

I know that all chemistry on Earth is a certain chirality. I can't remember if it's left or right, but it's one type. And if we get a meteor that comes, that has a different type, that shows some type of organic biological life, then we would know that it's alien and not something, you know, that came from Earth. Let's say, in molecules you can have handedness, based on the arrangement of the atoms in the same way your hands are left-handed and right-handed based on the arrangement of fingers. But in a soup of particles like protons, surely there's

no way their arrangement can be left-handed or right-handed. Considering the Big Bang was everywhere all at once, and we ended up in a universe with both right- and left-handed fundamental force particles, then maybe it was both. So I feel like the intuition here from the answers, tends to be that folks think the big bang was probably not left-handed. It produced an equal amount approximately of left-and-handed molecules. That totally matches my intuition as well, but is not actually the answer, right? Yeah, it reveals something about our prejudice, what we think is natural, what makes sense. And I think it's super fascinating in science. What answers people will accept without further explanation because it aligns with their intuition?

And they're like, oh, yeah, that makes sense. And what answers require more explanation? And for a lot of people hearing, oh, it was symmetric. It was a balance between left and right-handed. And they're like, yeah, cool, of course it was. That doesn't require any more explanation. But if you tell them, no, who's left-handed, or no, it was right-handed, then they ask why. And I think all the possible outcomes need a why.

You know, why should it be symmetric? But we have this innate preference for symmetry, for balance in the universe, which I think says something about us, but I'm not sure exactly what it says. I think I would like to have you on the next panel that judges my grants. I like the way you think about this stuff. It all needs answers. It all needs answers. Exactly.

Every question is worth asking. But yeah, it does make me wonder what questions we should be asking that would like have amazing impacts on how we view the world, but we just don't think to ask them because our gut says they make sense. Exactly. To me, this tendency suggests that there probably are questions we should be digging into more deeply or just accepting the answers because they seem right to us without really understanding what's going on.

And maybe in a hundred years or maybe when the aliens come, they're going to be like, why didn't you think about that more deeply? And we would be like, I don't know. It just made sense. Felt right. It felt right, man. Exactly. Yeah.

All right. Well, I think for anyone who hasn't thought of this concept yet or anyone who was lucky enough to not have to go through chemistry is maybe a little confused about what we mean by this handedness thing. So let's start at the beginning. What does it mean for something to have a handedness? Yeah. Left or right handedness really.

is a mathematical thing. It's a geometric thing and super fascinating. So let's start in two-dimensional space. Imagine that you take two arrows, right? So you know, they have a tip and a tail and then stick their tails together and have their tips be 90 degrees apart. So now you have like two arrows

that are pointing perpendicular to each other, right? Now in two-dimensional space, just like on a sheet, any pair of arrows you make are always going to be essentially equivalent. And by equivalent, I mean that you could line them up on top of each other, like move them and spin them and put them on top of each other. They're always gonna line up perfectly.

There's no way to make a pair of arrows that follow those rules where they're perpendicular to each other where you can't then line them up. So that's two-dimensional space, right? There's no handedness. But if you label one of the arrows X and the other one Y, so they're no longer two totally symmetrical, identical vectors, but they have these labels on them,

now there are two ways to arrange these two arrows. Like if the X arrow is straight up in front of you, then the Y arrow can be to its left or to its right. And because you have these labels, there's now no way to spin the left version of it to make it look like the right version. To do that, to have one lay on top of each other so the X is aligned and the Y's align, you'd have to flip it over, essentially reflect it, make a mirror image, go from left to right. It's analogous to notions of clockwise and counterclockwise on the surface of a clock also two-dimensional. Now expand our universe, add a third dimension above and below the plane, and add another arrow.

Take your two arrows that are perpendicular to each other. You could think of them as like the x-axis and the y-axis, or you could think of them as like your thumb and your pointy finger, right, that are perpendicular to each other. And now add a third arrow that comes out from where the first two were joined. Now you have to make a choice. Do you go up above the plane or down below the plane? And you might think, oh, it doesn't matter. If I stick it above the plane, I can just rotate it to make it below the plane, right?

But it actually does matter. If you choose the arrow that goes up above the plane and then you rotate the whole thing so the error goes below the plane, you'll find that the other two don't line up to the first two. There's no way to take that set where the arrow is above the plane and rotate it to match the error that was below the plane. You can see this very easily with your hands. Your hands, one is left-handed, one is right-handed. That's why we call them that. If you take your thumb and your pointy finger and you make them 90 degrees apart,

then you have your middle finger stick perpendicular to your palm. So it's perpendicular to the other two. Then you have like an X, Y, Z axis. But there's no way to orient them. So they line up on top of each other. There's one is left handed and one is right handed. All right. So I get that.

But when I think of handedness, I feel like I'm thinking of my hands in the X and the Y direction and not the Z direction. Yeah. It still doesn't work in those two dimensions is the point that, Kelly, your hands. are actually three-dimensional. You're an idiot. Stop thinking about this like they're two-dimensional. No, you're not an idiot. Your hands are three-dimensional.

You're exactly right. And the reason that you make your hands flat, you're thinking, I make my hands flat, I lay them on top of each other. They're still not the same, right? Even in sort of flat hand, two-dimensional world. The thing is that you're right, they're not two-dimensional. And if they were, you could make them lying on top of each other and be exactly the same. The reason that they can't is because they have a top and a bottom, right?

They have a thickness. If you try to put your hands together, then you meet your palms together, then they're inverted in that third dimension. So you still are working in a three-dimensional world. If you squeezed your hands in a hydraulic press so they were infinitely flat, then you could make them identical and lay them on top of each other. I don't think it's worth it for this purpose. That's why we have thought experiments.

You don't have to actually do it. You can just think of it that way. So that's what handedness is. And that's where it comes from. It comes from our hands, right? One hand is left-handed. One hand is right-handed. Amazingly, these words actually make sense, and the technical definition lines up with your knowledge.

Another example of how humans sort of take the way that we see and experience the world and overlay it on our science. Yeah, exactly, right? And what would aliens call this kind of stuff? Tenticalness. It's fascinating because this is a basic property of geometry, right? And it's totally arbitrary. There's nothing special about left-handed or right-handed, right? It's just how do you orient these three vectors? And it would be really weird if the universe, for some reason, preferred one or the other. Mathematically, they're totally equivalent. They're completely symmetrical. There's no reason for one to be more fundamental or more basic.

There's just two choices to make here. And not everything in the universe has a handedness, right? We're talking about this combination of three vectors or your three fingers have a handedness. But take a sphere, for example. The sphere has no handedness. There's no choices to make there. A way you can tell us something is handtiveness. is put it in front of a mirror. A mirror flips the handedness. Like if you put your left hand in

front of a mirror, it looks like a right hand. If you put your right hand in front of a mirror, it looks like a left hand. Put a sphere in front of a mirror. What do you get? A sphere, right? There's no handedness to a sphere. So some things have handedness and some things don't have handedness. So that's the sort of mathematics of handedness. And you might imagine a perfect universe, everything would be symmetric. There's no reason to choose one or the other. But as we already talked about on this episode, nobody is really symmetric. Like I use my right hand, right hand, right hand. It's a part of me that breaks this symmetry that for some reason prefers to use my right hand

to need dough and to write doodles and to point at things and all sorts of stuff. And some people are left handed. So the symmetry is broken sort of at two levels, right? One level is every individual person prefers one or the other and the population has way more righties than lefties. So this symmetry is already broken even from the place we've defined it. Fun fact, this happens in the animal kingdom too. I remember a talk, oh my gosh, this was two decades ago. But they were looking at blind cave fish and they put them in an environment with

Legos in the middle and it was a circular tank. And the fish to explore the environment, they like get, you know, the vibrations or the water currents. They feel them on one side of their body to figure out where things are. And so they'd swim around and you could tell that they had figured out like what their environment was like because they eventually slowed down and like stopped swimming. But as soon as you moved the Legos in a different configuration, they'd start swimming around again a lot. They could tell the environment had changed and they wanted to understand how it had changed. And they

specifically would swim with one side of their body facing the Legos because they had a body side that they preferred to collect information on. And so like even Fish exhibits something like a preference for one side over the other. Anyway, I always remembered that it was like amazing. blind cavefish were responding to changes in their environments. Animals are incredible. We've noticed that our dog seems to have a preference. Like when we ride in the car, he will stick his head fully out the window, but only on the right side. On the left side, he will stick his nose out the window, but he won't like all the way climb up on the armrest and get his whole shoulders out the window. So he seems to prefer the wind on the right

side of the car. And that makes me wonder, like, is he more comfortable with his right paw and looking out that window requires more strength from that leg or something? Or, you Is he fundamentally a righty? I mean, have we done a lot of experience on animals to determine, you know, if they're right or left-handed? Like, do chimpanzees use their right or left-hand more? Do you know? I don't know. I think we need to get Katie Golden on the show from Creature Feature, and she'll let us know.

But I do not know the answer to that. So the left side is the side that the other cars are coming from. I wonder if it just feels safer to stick your head out farther on the opposite side than, like, towards incoming traffic. Oh, we'll have to do some experiments with folks in England to see if they're done. prefer the opposite side. There you go. That's a good experiment. We're doing the natural experiment right here on Earth, folks.

So you see that pop up in your daily life and in your own experience and in your family, but it turns out to also be important in the biochemistry of life and later on, more fundamentally, in physics itself. And yes, we said chemistry, but stick with us. This is exciting. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal.

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or wherever you get your podcasts. Presented by Capital One, founding partner of IHeart Women's Sports. All right, so we're back. We've talked about handedness. And I remember from organic chemistry and biochem that organic molecules are left-handed and right-handed. And actually, when we were researching soonish, Zach discovered that spearmint and caraway, which are very different tastes are molecules with opposite handedness.

Whoa. And so like those opposite handedness results in completely different ways that it interacts with our body. So anyway, molecules have handedness and our chiral. And why? Yeah. So we don't fundamentally know the answer. And you might be wondering like what does handedness mean for a molecule? Well, it just means that if you put it in front of a mirror, you don't get the same molecule.

So a molecule is more like the three first fingers on your hand or the XYZ axis than it is like a sphere, right? They're not symmetric. They have a handedness to them. So you can't just like spin a left-handed version of amino acids into a right-handed version of methane. It's like fundamentally a different molecule. You can tell which one is left and which one is right. And as Kelly mentioned earlier, life is built out of only one of these things. Life has chosen one of these.

We are all built out of left-handed amino acids. The things that make up all living creatures on Earth, including the microbes that infect us, are all made out of one of these things and not the other one, which is really peculiar. Yeah, wouldn't we have a lot more options for the kinds of amino acids and stuff we could make if we had both chiralities? But I guess we already could make more amino acids than are typically used by organisms. So maybe we don't need that many more amino acids. Yeah, because the different chiralities don't work. together. Like these things have to fit together really precisely. I think of these little molecules as little machines, you know, that do something biochemically. This one builds that,

and this one builds the other thing, and this one rotates this thing. They're all like, you know, I imagine the little Legos in my head because I'm not very good chemistry. And they have to have their particular arrangement to do their job. You can't just replace it with the opposite chirality and expect it to do the same thing, especially if everybody else is the different chirality. It might work if you flipped all of it, right? We took all of life from left to right, and you can make a right-handed version. I think that's one of the questions Eric Church was hoping to answer. Like, is it really arbitrary? Could life work? If everything was right-handed, it seems like it should. But it's fascinating that you can't mix them, right? Like a left-handed

person can't eat right-handed food or couldn't have a baby with a right-handed person. You know, like their biochemistries just don't interact. It's fascinating. Yeah, you said Eric Church, but I think you meant George Church. Oh, sorry. Yeah. That's all right. So is this kind of like, if you have an iPhone, you can't use the apps made for Android. Could it just be that life sort of started in one direction and then some piece of machinery for life came into existence that was really good, but only the right-handed molecules could be used with that piece of machinery. And that just kind of got the ball rolling and the left-handed ones could never compete. Sorry, Android users. And that's why we have this preference for one. It was like some early machinery used one chirality and not the other.

Yes, so we actually don't know the answer to that question. We don't know like, does it have to be this way? Is there something about left-handed molecules that are better at forming life or something fundamentally by the biochemistry of life that prefers left-handedness? That would be weird, right? Because there isn't really a difference. It's just reflection. Fundamentally, the universe shouldn't prefer one or the other, but it kind of seems to. And you're right that once you choose one, you're stuck, right? It's sort of like everybody sits down at a dinner party. Are you taking the silverware that's on your left or on your right? Once somebody takes one, everybody's got to make the same choice or you get clashes, right? Or as you say, once you're in the Apple

ecosphere, then you've got to have all Apple devices where they don't work together. So we think that once you choose one, you're stuck with it. We don't know if it was just like a random choice. Like that first living thing could have been left or right and it was just randomly left and now all stuck left or if there's a reason it has to be left or more likely to be left and just everything has followed from that. Yeah, but it feels to me like there's no reason why you couldn't have had a branch of life that started right and that a branch of life that started left like, you know, the same trick could have been come upon for both chiralities and then you sort of radiate out from there.

And then there was an epic battle right versus left. Yeah. I'm sure the right-handed would win. But this is not something we even knew until like 150 years ago. And it was Louis Pasteur who discovered this. He was studying this byproduct of wine fermentation, tartaric acid. And he noticed that there were two types of crystals that were made. There were mirror images of each other.

So he was trying to synthesize this thing because you can synthesize these chemicals and you can make right or left. But then you discover out in the natural world you only ever find left. So he discovered, oh, this is a difference. If I make it myself in the left. lab versus if I like find it from nature and he was able to pin this down using polarized light to figure out what the chemical structure of these things were. So this is something we've only known about for 150 years and people have been trying to figure out like what is the cause of it for much longer than that. There are some speculative answers. I read a paper that suggested that there

could be something about how magnets formed in the earth that prefers left-handed chirality like the magnetic field of the Earth generates some preference for the left-handed versions versus the right-handed versions, but it's very speculative. And this is super cool. We just learned from an amazing mission that went out and sampled an asteroid, Benu, brought stuff back to Earth so we could study it. In that sample, there are equal mixtures of left-and-right-handed organic chemicals. So huge clue because life on Earth prefers the left-handed ones, but the basic ingredients for left or right-handed life seem to be out there in the universe. So when you do industrial processes like Pasteur was doing, you get both kinds. Do you get both

kinds evenly? Because if so, it feels like the magnet's answer doesn't work. You're right, but I think the idea is that there could be these magnetic surfaces essentially that are made that better bind to the left-handed bits and then essentially bring them together, gather them together so that they can make more complex molecules. So you might get more complex left-handed structures faster than you get complex right-handed structures, even if you have the same relative abundance of the precursors. That basically creates a playground where the lefty bits come together to make the complex structures you need for life.

I mean, that feels testable. Yes, this is totally testable. I read an article from Science in 2023 where they do experiments and they can produce this kind of effect. That doesn't mean that it's the reason why life is. is left-handed. It's just like, oh, there is, in some sense, something that prefers left-handed chemistry to right-handed chemistry, right? And we do see other hints of that in the universe, like there are other parts of the universe that seem to prefer left-handedness over right-handedness,

like particle physics. Particle physics has a basic preference for left-handedness over right-handedness, and after we dig into it, we can come back and make the connection. People think that maybe high-speed particles from space could have influenced the left or right-handedness of life on Earth. We talked about amino acids being left-handed. Amino acids come together to form proteins. Are there other things that are important to biology that also have a handedness? Well, I think the left-handed nature of the amino acids means that the sugars they make are right-handed, because that's the kind of thing that a left-hand amino acid will make. So those bits are sort of complex. So there are some parts of our life biochemistry that are right-handed, that the amino acids are all left-handed. So we call it left-handed, if that makes sense.

Because the amino acids are the building blocks, you expect the things that the amino acids make, like proteins and sugars, to be the opposite-handedness because of how they all get put together. Yeah, exactly. And you can actually exploit that. As you were talking about earlier with flavors, some artificial sweeteners exploit this fact. despite being a sugar and tasting sweet, they can go through your body without being metabolized because they have the wrong-handedness. So that's kind of cool. That is kind of cool. I feel like there's a little voice in the back of my head saying, wasn't there a study about how maybe they're not so good for your body? But I'm not an expert on that. Anyway, it might be worth looking up. And we are not making any medical recommendations here,

folks. Amen. All right. So we've discussed that amino acids are building blocks of other things and that the left-handed building blocks produce right-handed other things. So let's go down another level before amino acids or maybe multiple levels before amino acids, down to particles. Like, if you knew that amino acids were left-handed, could you predict the handedness of particles

because it alternates between levels? Oh, it's a great question. We don't know the answer to that. And we knew 150 years ago that amino acids were left-handed, but physicists were confident that the universe, fundamentally at the particle level, had to be balanced.

that it would be crazy if the universe itself was left-handed in some way. Like, why would it prefer one direction over the other? That was nonsense. And people did some tests early on, like, let's see if electromagnetism is symmetric. Is there any preference for photons to go in one direction or the other? And they're like, no. And they did tests on another force as well, the strong force. But people were very confident that the universe didn't prefer left or right-handed.

And when we talk about particles, we have to be a little bit careful what we mean by left-or-right-handed particles, because the definition we gave earlier, you have like three directions. That makes sense for building molecules, right? You're putting these things together. You can imagine like balls and sticks and you're making something which doesn't reflect in the mirror. But particles we don't think about as having extent, right?

They're just like dots. So what do we mean by left or right-handed when it comes to particles? Well, particles don't have an extent, but they do have two different arrows. You can have particles that can be moving in one direction, so that's the momentum of the particle, right? Imagine an electron is flying through space,

You could put an arrow from where it was to where it's going. That's one arrow. The other arrow of the particle is its spin. Electrons can be spin up or spin down. So you can think of that as another little arrow. And that arrow can either be aligned with its motion, in which case we call it a right-handed electron or not aligned. So pointing away from the direction it's moving.

So if your two arrows of your spin and your momentum point in the same direction, we call you a right-handed particle. And if they're not aligned, we call you a left-handed particle. Does it change the way we think about this when we think about electrons as waves instead of particles? Yeah, that's a great question. And we should always keep in our minds that electrons are not tiny little balls or even dots, but they are guided by the wave function, right? So what happens to a particle is determined by this wave, its outcome,

which makes some of this stuff probabilistic, right? Like an electron might not have a defined spin. It might be maybe this or maybe that, right? But some processes have to produce left or right-handed electrons, which means you know in advance, like this one doesn't have a probability to be left or right. It has to be left or it has to be right in order to balance with other bits. So, for example, if you have two electrons produced opposite each other, you know their momentum point opposite to each other. And you know their spin also have to be opposite to each other, which means they're either both right-handed or they're both left-handed.

And you might not know that in advance. So in that case, for example, your electrons are going to be 50% left-handed. 50% right-handed. But they have to be the same, right? If they're produced the same. So yeah, the wave nature gives you a probabilistic aspect to all these particles for sure. All right. Got it. And so this is what we call handedness for particles. Sometimes they call it helicity. And one important caveat here is that this isn't actually something that's exact because the momentum of particle depends on your velocity. Like you can imagine flipping the direction of a particle by zooming past it in a spaceship. So now instead of moving one direction, it looks.

looks like it's moving the other direction. That basically flips its momentum. So we actually only talk about the handedness of particles that have no mass or very, very, very low mass, precisely because then you can't pass them in a spaceship. To be very technical, this handedness is actually an internal label. It's not a physical thing.

So the direction of the two arrows is like an approximate way to think about the handedness of the particles. But fundamentally, it's some internal label we don't understand the way like charge is. So I just think about these. particles is having like a little label on them. Some of them have an L and some of them have an R. And we thought for a long time, like the universe shouldn't predict either one. Like, if you have some particle physics process, it should make the same number of right and left-handed

electrons. In the early universe, you should have gotten an equal mixture, right? In the same way, we talked earlier about preferring symmetry. And then it was in the 1960s that people realized, hey, you know, we think that the universe is balanced. We think that there is a symmetry here. And we've checked it for a couple of things, but nobody's actually gone and done the test to see if the weak nuclear force prefers left or right-handed particles equally or not. I'm just going to point out that the biologist had figured out the importance of this 100 years earlier, apparently. I'm glad you guys caught up, though. So go ahead. That's right. Physics is always 100 years behind biology. That's the way it works. So there was this exciting moment in the late 50s where people realized, oh my gosh, nobody's test.

did this before, and it's not actually that hard to do. So then this amazing scientist, Chan Chen Wu, realized in the late 50s, actually this wasn't difficult to test. This is something you could figure out. So she decided to skip her Christmas holiday. She sent her husband on along and said, I'm going to stay in the lab and figure this out. You know, when you get excited about something. And she put the experiment together.

She got a bunch of cobalt atoms to spin only in one direction. and then she measured the angles that the electrons came out. And this was a great test of whether the universe preferred one direction or another because the electrons were made purely by the weak force. And she discovered not only was it out of balance, but it was completely out of balance. It wasn't like the electrons were 5149 one direction. It was like a hundred zero.

Like the electrons would only go in one direction. It turns out that the weak force only makes and interacts with left-handed particles. It like completely doesn't feel. play with right-handed particles at all. So all the other forces don't care. Electromagnetism, the strong force, no preference. But the weak force only plays with left-handed particles. This was a really shocking discovery. And after the break, we are going to 100% explain to you why that is. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed.

There's been a bombing at the TWA terminal. Apparently the explosion actually impelled metal, glass. The injured were being loaded into ambulances, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and Order Criminal Justice System is back. In Season 2, we're turning our focus to a threat that hides in plain sight. That's harder to predict and even harder to stop.

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

Now, he's insisting we get to know each other, but I just want her gone. Now, hold up. Isn't that against school policy? That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor. and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them.

I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. I'm Dr. Joy Harden Bradford. And in session 421 of Therapy for Black Girls, I sit down with Dr. Othia and Billy Shaka

to explore how our hair connects to our identity, mental health, and the ways we heal. Because I think hair is a complex language system, right? In terms of it can tell how old you are, your marital status, where you're from, you're a spiritual belief. But I think with social media, there's like a hyper fixation and observation of our hair, right?

That this is sometimes the first thing someone sees when we make a post or a real. It's how our hair is styled. You talk about the important role hairstylist play in our communities, the pressure to always look put together, and how breaking up with perfection can actually free us. Plus, if you're someone who gets anxious about flying, don't miss Session 418 with Dr. Angela Neal-Barnett,

where we dive into managing flight anxiety. Listen to Therapy for Black Girls on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Get fired up, y'all. Season two of Good Game with Sarah Spain is underway. We just welcomed one of my favorite people, and an incomparable soccer icon, Megan Rapino to the show, and we had a blast.

We talked about her recent 40th birthday celebrations, co-hosting a podcast with her fiancé Sue Bird, watching former teammates retire and more. Never a dull moment with Pino. Take a listen. What do you miss the most about being a pro athlete? The final, the final, and the locker room. I really, really, like, you just can't replicate,

you can't get back. Showing up to the locker room every morning, just to shit talk. We've got more incredible guests like the legendary Candice Parker and college superstar A.Z. Fudd. I mean, seriously, y'all. The guest list is absolutely stacked for season two.

And, you know, we're always going to keep you up to speed on all the news and happenings around the women's sports world as well. So make sure you listen to Good Game with Sarah Spain on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Presented by Capital One, founding partner of IHeart Women's Sports. And we're back. Just kidding. We never have 100% explanations for anything. What is our current state of not understanding this phenomenon, Daniel?

It's not something that we understand. It's something that we describe. Something we see in the universe, we can incorporate it into the mathematics of our theory, like the standard model of particle physics. It describes how particles interact and how they're created and all this kind of stuff. naturally has left and right-handed particles, and the mathematics of the weak force allow it to only interact with left-handed particles. But again, we don't know why that is. You know, the other forces treat the particles completely equally.

And the Higgs force unifies these things. Like the Higgs force combines the left-handed and right-handed version of particles into one that we see and know and love and has mass. Where does it get the right-handed versions if it's combining them? So it gets the right-handed versions from other forces and combines them. Okay. Yeah. So you can make right-handed electrons.

You just can't use the weak force to do it. You can use the electromagnetic force to make right-handed electrons. No problem. Oh, but those will not interact with W bosons and Z bosons and stuff like that. It's really weird. And if we didn't have the weak force, we never would have discovered that our universe, for some reason, seems to be left-handed at a particle level. If you were to like rank the forces in terms of like how common they are in the universe,

I actually don't know the right way to rank these. Like how important is the weak force? Amazing question. Well, you know, the most powerful force is a strong force and then electromagnetism, then the weak force, then gravity, if it's a force at all. But the weak force in some way is so much more complex and fascinating than any of the other forces. It's got extra particles, like it has the W and the Z particles. all these particles needed to do its stuff.

And it's so much more complicated, and it's responsible for the Higgs boson. So it's pretty important and weird. And in that sense, it's valuable because it gives us insight into the nature of the universe. You know, it does its weird stuff. If everything was simple and clean, we wouldn't learn as much about the universe. It's the ugly messes that teach us something about how the universe is actually working. I feel like that's a lesson for my life somehow. But go ahead.

There's such a shocking discovery that the theorist that suggested it won the Nobel Prize just like a couple of years later. Unfortunately, Chin Chen Chen Wu, who did the experiment, she didn't get the Nobel Prize. Another example of the Nobel, not treating lady scientists equally, unfortunately. There's an imbalance for you. Yeah, that sucks. She's still alive? She is no longer alive. But we're going to have a whole episode about her next year.

And we're going to talk to her granddaughter, who I grew up with. Oh, fantastic. All right. I'm looking forward to that. So the weak force produces left-handed electrons, and then somehow we end up with left-handed amino acids. Let's talk about the intermediate scale there. How do we think scale up between left-handed electrons and left-handed amino acids? Yeah, we don't know.

There's a lot of speculation because this smells like a weird coincidence. Like how is it that the universe produces more left-handed particles and right-handed particles and life is made out of left-handed amino acids? Is that a coincidence or is there a reason? So there's a theory that particles from space, when they smash into the atmosphere, cosmic rays, they produce a shower particles and the weak force is involved, which means that it makes more left-handed particles than right-handed particles. And then dot, dot, dot, dot a bunch of stuff that's not really plausible. Maybe that makes more left-handed amino acids. And, you know, there are papers I've read about this, and I always come away from them going like, I don't think so.

So it's like a real effort to draw a line between these things because it's hard to imagine how a left-handed muon is going to somehow make more amino acids that are left-handed. Like yes, the muons come in and they smash into stuff and there's still an important part of life today. You know, breaking amino acids and creating mutations and all sorts of stuff is important for evolution. But we don't have a microphysical explanation for why having more left-handed muons could create more left-handed amino acids or encourage them to form life or whatever, make them

more resilient, I don't know. Because the weak force is very, very weak. You know, most of the time when a muon interacts with you, it interacts electromagnetically. So it would be a very subtle effect if it even did exist. So really still an open question. We don't understand whether there's any connection between the fundamental left-handed preference of the weak force and the left-handed nature of life on earth. Okay, so there's an important question that one of our listeners can answer, one of our young listeners. Okay, so we know we have handedness in some cases. We don't know why we have it. We don't know the implications as you scale. Is there important symmetry in other areas that gets broken? Yes, a great question. This inspires us to look for violations of symmetry

elsewhere in the universe, right? And we know already that the universe isn't always in balance. Like, for example, we know that there are two different kinds of matter in the universe, matter and anti-matter. Antimatter is like the reflection of matter where everything has the opposite charge. So we have electrons. We can also make positrons, which are just like electrons, but they have the opposite charge. And you can make antiprotons and anti-neutrons. And there's nothing really anti-about them, except that they're not our kind of matter. So, you know, you could, we think, maybe build life out of anti-electrons and anti-protons to make anti-people or whatever. We don't really know that for sure, but the laws of physics so far suggest that that's possible.

But the universe has made more of matter than antimatter. Have I watched too many sci-fi movies? I'm under the impression that if matter and anti-matter interact, they explode or consume each other in some way. Like, could both of these things exist in the same universe, or does one have to win? They can't exist near each other because they interact very strongly. And so, for example, if you have an electron and a positron near each other, they will attract each other and they will annihilate and give you photons. And it's a very efficient conversion of energy from mass to radiation. So for example, if you have a gram of matter like a raisin and a

gram of antimatter, like an anti-raison, you bring them together, you get about as much energy as a nuclear bomb, just out of two grams of matter and antimatter. So yes, you can't have matter-based life and antimatter-based life on the same planet, but you could have, for example, matter galaxies and anti-matter galaxies, right? They don't have to touch each other. They're just floating in space saying hi. But we're pretty sure that all the galaxies in the universe are matter galaxies, not anti-matter galaxies. And we can actually test this a little bit because galaxies shoot out particles. All the stars and the black holes are emitting radiation. And they shoot out electrons, for example. And if there were anti-galaxies, they would shoot out anti-electrons.

And where those meet, you would see these great flashes of light where the electrons and the anti-electrons were meeting. And we don't see any of that. We don't see like huge curtains of light between galaxies, which would suggest that at least as far as we can see, everything is made of matter. So that's an important asymmetry in the universe. Again, one we don't understand. We think probably in the Big Bang, there was an equal amount of matter and antimatter. But something preferred matter, because otherwise it would have all just gone away and turned into, a universe filled with light and no matter.

So there's a preference there for matter. It's just an example. We don't know that it's connected to right or left-handed. We call one matter and the other anti-matter. It's just an example of how the universe sometimes seems to make one choice and not the other for reasons we don't understand. All right. Well, so first of all, I think it's important to note that I'm on team anti-raison.

But you like the golden raisins instead? I don't like any raisins. No reasons. No raisins. Okay. Yeah. Team anti-raison. But how do you feel about grapes?

Do you like grapes, but no raisins? I'm pro grapes. Really, interesting. Are you anti-dried fruit in general? No, dried mangoes. Those are great. Oh, man, we've got to convert you. This is really, really important.

Is it just because you think raisins ruin oatmeal cookies? Because you'd be right about that. Yeah, that's like 90% of why I have trust issues. So the Big Bang had to have resulted in a preference for one or the other, right? Because otherwise it would have all just, like, blown up at that point when it was all compressed. Well, either more matter was made in those early moments than antimatter, and then when they annihilated, you get some matter left over. So either there's some early baked-in preference for matter over antimatter, or it was symmetric at the beginning, and there's some process which then prefers matter to antimatter. And we have a few clues.

We've discovered one or two little processes that prefer making matter to antimatter, and that was sort of fascinating and surprising and led to more Nobel prizes. These things are called CP violation, if anybody wants to dig deeper into them. But they're not enough to explain it. They're like tiny little effects. They can't explain the size to the effect that we see in the universe. So this basic question, this asymmetry in the universe, we still don't have an answer to. But just to be clear, again, it's not directly connected to left-handed versus right-handed, whether the universe is symmetric.

It's just whether the universe is symmetric in a mirror. It's just another example of how the universe doesn't have to be balanced, right? it can pick one or the other, we think, and we just don't understand why it does or whether it did. But we can think about whether the universe and the Big Bang itself was symmetric from a left versus right-handed point of view. Like when we talk about making those three vectors, is there something in the universe that really prefers those fundamentally at the level of the structure of the universe itself,

not just the particles or the amino acids or dogs or this kind of stuff? And we can think about this by looking at the relationships between galaxies. There's this really amazing study people did last year where they basically just looked at groups of four galaxies and decided whether they would call them left-handed or right-handed. So remember the example of your fingers, right? You have three fingers, so three tips, and there's also the point where they all meet. So you have sort of like four points there. So if you have four points, you can say, is this a left-handed grouping or right-handed grouping?

So they looked at all the galaxies that they could find over a number one. could find over a million examples in this one study, and they grouped them into clusters of four and then decided, is this a left-handed grouping or a right-handed grouping? And they figured, like, hey, this is just galaxies strewn out in the universe. We're just assigning left- or right-handed to these clusters. It should be balanced, right? There should be no reason why you would get, like, more right-handed or left-handed clusters. But what they found is a huge bias towards left-handed clusters of galaxies. When you group these things together,

I know it makes no sense. Like, why would you prefer one or the other? But, you know, they had groups check their results. This is the kind of result you sort of hope for in science, but then you're terrified of because then you're like, what? This has got to be wrong. This has been delayed my paper.

Oh, my gosh. Did I pick the galaxies arbitrarily? I feel like that would have to be a hard, hard to pick them. Yeah, exactly. Where they tried every combination. And out of a million galaxies, you get a trillion trillion combinations. They make these pyramids, right? Like four galaxies make this pyramid and you can decide whether it's a left or right-handed pyramid. And the chances of this being a random

fluctuation is one in 300 billion. So either it's a crazy fluctuation or it suggests that there's something about the universe, something about the topology, the structure, the nature of space and time itself that aligns these galaxies in a more lefty way than a right-handed way. It's really a fascinating clue, and it's just like adds to the story, like life is left-handed, particles are left-handed, something about the structure of galaxies in the universe itself is left-handed. No wonder, Zach thinks he's so great.

Turns out he's right. Science has proved him right. There's got to be something we don't understand in between there. All right, reviewer number two over there. So this is just like a collection of clues that all point towards something. something that smells suggestive, but it could just be nothing. It could just be, here's a bunch of coincidences, you know, left versus right, whatever. The universe just picks randomly, and we live in a multiverse with all different kinds of

universes, and some of them have right-handed life and right-handed particles and left-handed galaxy structures, or maybe there's something deep in the mathematics, which really prefers left-handed structures and can only work this way. It's just we haven't puzzled it out yet. We haven't found the connections between these different layers of leftiness. And we haven't understood what about the nature of the universe requires things to be left-handed. It's a fascinating puzzle. And the kind of thing I think in a hundred years, I hope we have much more clarity on.

Are we currently at the just like scratching our head and pulling out our hair phase? Or are there like four competing hypotheses and we're just waiting for the LHC to give us the answer? Like, where are we right now? I think we're in between those two different outcomes. We have some crazy ideas. Like people think maybe the thing that came before that early moment of hot density, you know, inflation and the inflaton field and sort of pre-Big Bang theories. And everything that's pre-Big bang, very speculative.

And that doesn't mean worthless, right? It just means like, hey, we don't really know. We're still in the building phase or trying stuff out. Some of those maybe were seated by something that prefers left-handedness. people are trying to build left-handed ideas into that Infloton field with varying success. So we don't have solid predictions that we can use to test any of these ideas. We're just sort of like, maybe this is something and maybe this is something we should be building into our theories of the pre-Big Bang universe.

We can try to look deeper into the history of time to try to understand it. Like we hope that gravitational waves from the very, very early universe will help illuminate what was going on. You know, we could only see the early universe back to about 380,000 years after that first understood moment because that's the first time the universe was transparent. But there's a lot of stuff going on before the universe was transparent when it's hot and dense and opaque. And we hope that gravitational waves will give us a window into those moments. And maybe there's some clue there in the polarity of those gravitational waves to see they prefer left-handed physics to right-handed physics or maybe not right maybe they're perfectly in balance

so there's a possibility that we could learn something but that's very subtle physics and seeing gravitational waves from the very early universe is notoriously tricky there was an experiment bicep two a few years ago that thought it had seen them and had evidence for inflation then it turned out to just be dust yeah oh that's frustrating it's always pigeon poop or dust exactly science is hard people. It's hard. It is. But the mysteries are deep and they are fascinating and all of these clues tell us like maybe this is a thread we should pull on that's going to unravel our whole understanding of the universe or maybe it's just a coin toss and beginning of the universe and it means nothing. People will spend entire careers trying to figure it out. And maybe one of you out there

will be the one to pull back the veil and help us understand the nature of our own universe. Please do that. Soon, please. I'd love to know the answer. Yeah, same. Daniel and Kelly's Extraordinary Universe is produced by IHeart Radio. We would love to hear from you. We really would. We want to know what questions you have about this extraordinary universe.

We want to know your thoughts on recent shows, suggestions for future shows. If you contact us, we will get back to you. We really mean it. We answer every matter. email us at questions at danielandkelly.org or you can find us on social media we have accounts on x instagram blue sky and on all of those platforms you can find us at d and k universe don't be shy write to us i'm dr scott barry coughman host of the psychology podcast here's a clip from an upcoming conversation about how to be a better you when you think about emotion regulation we're not

going to choose an adaptive strategy which is more effortful to use unless you think there's a good outcome avoidance is easier ignoring is easier denials easier complex problem solving takes effort listen to the psychology podcast on the iHeart radio app apple podcasts or wherever you get your podcasts get fired up y'all season two of good game with sarah spain is underway we just welcomed one of my favorite people and incomparable soccer icon megan ripino to the show, and we had a blast. Take a listen. Sue and I were like riding the lime bikes the other day and we're like, we're like, people ride bikes because it's fun. We got more incredible guests like Megan in store, plus news of the day and more. So make sure you listen to Good Game with Sarah

Spain on the IHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Brought to you by Novartis, founding partner of IHeart Women's Sports Network. How serious is youth vaping? damage serious, one in ten kids vape serious, which warrants a serious conversation from a serious parental figure, like yourself. Not the seriously know-it-all sports dad, or the seriously smart podcaster? It requires a serious conversation that is best had by you. No, seriously. The best person to talk to your child about vaping is you. To start the conversation, visit talkaboutvaping.org. Brought to you by the American Lung Association and the Ad Council. I'm Simone Boyce, host of the Brideside podcast, and on this week's episode, I'm talking to Olympian, World Cup champion, and podcast host Ashlyn Harris.

My worth is not wrapped up in how many things I've won, because what I came to realize is I valued winning so much that once it was over, I got the blues, and I was like, this is it. For me, it's the pursuit of greatness. It's the journey. It's the people. It's the failure. It's the heartache. Listen to the bright side on the IHeart radio app, Apple Podcasts, or wherever you get your podcasts. This is an IHeart podcast.