Daniel and Kelly’s Extraordinary Universe - Does particle spin affect life on Earth?

Episode Date: January 26, 2023

Daniel and Jorge talk about how the Universe's preference for left-handed particles may have shaped our chemistry.  See omnystudio.com/listener for privacy information.

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It's pretty tricky, yeah. If you're used to doing things with one hand, it's hard to switch. Well, what about driving? Have you ever driven on the left side of the road? You mean on purpose or against the law or following the laws of traffic? Well, you know, there are some places in the world where they drive on the other side. I have driven in Australia and England. Yeah, it's pretty tricky.

But after a while, you get used to it. What would you say is better? Your left side of the road driving or your left-handed drawing. Well, I've fortunately have not had an accident either side of the road. So the data says that I am equally good. Well, I'm glad you're even-handed. That sounds like a left-handed compliment, Daniel. I think that's right.

Hi, I'm Jorge. I'm a cartoonist and the creator of PhD comics. Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I have tried to do math left-handed. You mean you write out math with your left hand. Is that what you mean? Yeah, I try to write out math with my left-hand. or sometimes upside down. Sometimes when I'm teaching math to my kids, I have to write it so that they can see it, which requires a little bit of awkward gymnastics.

But if you use your left hand, then maybe it's normal. If I use my left hand, then my handwriting looks as sloppy as theirs. I know people who aspire to be ambidextrous. So they purposely use the mouths, even though they're right-handed, they use their mouse with their left hand

so that they are able to do both. I would give my right arm to be ambidextrous. Well, if you give you your right arm, then you wouldn't be ambidex. Sounds like you're caught in a paradox. But welcome to our podcast, Daniel and Jorge, explain the universe, a production of IHeard Radio.

In which we try to tickle the right side of your brain and the left side of your brain. We want to understand the entire universe, the top half, the bottom half, the left side, the right side, and everything in between. Even the backside? The backside, the front side.

The dark side and the light side. Every side of the universe deserves to be understood. And we think it's possible. this podcast, we ask those big questions about the nature of reality, the nature of life, why we are all here, what it all means, how long we will be here, and whether we're alone. And we try to explain all of them to you. And today, I want to especially explain things to Walter Bloom, a long time listener of the pod from Switzerland, whose girlfriend Victoria wants to wish him a happy 38th birthday. Happy birthday, Walter. Yeah, it is a big universe to explain. It is a wide universe full of many

sides to it, many different ways that you can look at things and also many different ways that things can be put together. There are almost an infinite way for a matter to arrange itself. And one of the joys of physics is figuring out how the universe works because then we get to ask why. When we discover that we are put together out of tiny little particles, we get to wonder like, hmm, why is the universe arranged out of these tiny little particles? Why does it have these patterns? What does that really mean? The joy physics is really that it's setting us up to ask philosophy questions. Oh, is that the main goal of physics? Just to be a primer, like a trailer to philosophy? Just the opening act for philosophies. That's what you're saying? Physicists are just there to

warm up the crowd. In the end, I think that all science really is motivated by philosophy questions. You know, at the heart of almost every science question we ask, there is a why question, which is in the end, fundamentally philosophical. Yeah, and we ask these questions, not just because it's interesting and fascinating and we understand more about the universe, but sometimes these questions and these issues have a big impact on our daily, everyday lives, even maybe on life itself. Yeah, we notice these patterns in the universe. The universe seems to organize itself in this way and not some other way. We notice sometimes there are symmetries in the universe. Like you could rotate everything and the laws of physics wouldn't change. But also sometimes

we notice that there are not symmetries in the universe, that the universe has a strong opinion about how things should be done and the opposite way just does not happen. Time flows forwards and not backwards. And these are the things that inspire our philosophical musings to wonder what it would be like for a universe where time flowed backwards or what it would be like for a universe in the mirror of our universe. Yeah. And so our universe likes to put things together in a particular way. And you can trace sometimes that to the very properties of the smallest particles in the universe, the things that everything is made out of. And simply these properties can have a pretty big impact on what gets formed.

the universe and even whether we would be here or not. It does seem sometimes like at the smallest level, the universe follows really different rules, really strange quantum rules that don't really affect our lives. Like how a particle moves through space is totally different from how a baseball flies through space. But as you say, sometimes there is a connection. Sometimes we can even find a portal from the tiniest particle to our everyday lives. So today on the podcast, we'll be tackling the question.

Does particle spin affect life on earth? Are we trying to put a positive spin here on life on earth? I'm trying to put a positive spin on particles. I'm like, look, particles are relevant. Give me money, is what you're saying. Well, you know, that's the philosophy that's underlying all of it. Yes, we're trying to make our science relevant. Now, do you share any of your funding with philosophers?

Do philosophers really need funding? I mean, how much does paper and pencil cost anyway? As in that aren't those the tools of your research as well? $10 billion particle colliders, you can't build those out of pencil and paper. Well, you could. You just haven't tried. The paper meshay particle collider. I'll put that on the table next time we're discussing the future of the field. Can you demonstrate mathematically that you cannot build a particle collider with paper meshay?

That's true, the spitball collider. Yeah, let's see what we can learn by colliding spitballs at nearly the speed of light. Yeah, it's possible, right? It is possible. I have to do some pencil and paper calculations to see what kind of experiments we could do and what we might learn about the universe from a paper michet collider. Yeah, I'll fund that. Here's five bucks.

But this is an interesting question. We're trying to link life on earth to something as small and maybe seemingly insignificant as the spin of a fundamental particle of nature. That's a pretty big leap. It is a pretty big leap? And you might think it sounds a little bit desperate. Like, is Daniel just trying to be irrelevant to life? But remember that I'm actually doing this research mostly because I think it's irrelevant. honestly because it doesn't affect everyday life on Earth,

which means you can't use it to build weapons. Wait, did you just admit your research is irrelevant to all life on Earth? It's irrelevant in a sense that it doesn't have immediate practical applications. Wait, did you just admit your research has no immediate practical application? Oh, absolutely, yes. Learning about particles has no immediate practical applications. I can't tell you tomorrow that it's going to improve technology or even next year. It's basic research in the sense that we might discover something crazy and new.

about the universe, which down the road, I'm sure, will benefit society. But in terms of like immediate impact and, you know, tomorrow's weapons systems, no, we have no relevance. All right. Well, I guess possible deniability is important for some people. But this is an interesting question to wonder if maybe the spin of particles could have affected how life on Earth evolved or even if life itself evolved at all on this planet. Yeah, it's a fascinating hypothesis with a little bit of evidence to back it up. Well, as usually we were wondering how many people had thought about this question, had thought about maybe the properties of particles having an impact on life on earth. So as usual, Daniel went out there to ask people, do you think

particle spin can affect life on earth? So thank you very much to everybody who participates in this segment of the podcast. We really appreciate hearing your thoughts. And I think everybody out there enjoys it as well. If you'd like to share your thoughts on the topic of the day for future episodes, please don't be shy. Write to us to questions at Daniel and Jorge.com. Usually people had to say, I barely know what particle spin is, but I could surely say that it does not affect life on other planets from the solar system. Well, everything is spinning. Particles are spinning. The earth is spinning.

The galaxy is spinning. Reams are spinning. Everything is spinning. So, yeah, the life is spinning. I'm going to say yes, because it affects the way matter is made up. but I really don't know what would happen if particle spin were to be reversed. I don't know if we would even recognize the effects of that. I think it can be interpreted maybe a couple ways.

Outside of like the necessity of spend to make physics work, I would say probably not very much impact to life. I don't think, I don't think like DNA is interacting with particle spin. All right. Some people said yes. Some people said no. There are strong opinions here. There are positive and negative spins.

On one hand, it does seem hard to imagine that the behaviors of tiny little particles could affect something like life on Earth. On the other hand, if you believe reductionism, if you believe that everything in the universe comes out of how tiny little bits are dancing around and towing and froing, then in principle, everything about life comes down to how particles work. Well, yeah, I mean, I guess if particles, for example, didn't feel the electromagnetic force, I mean, the whole universe would be different. Yeah, I'm sitting here trying to imagine what a universe would be like without electromagnetism. I mean, it would be a dark universe for sure, right? There would be no light at all in that universe. Yeah, or I guess even if the particles had a different mass, it would also change the whole universe, right?

Like planets would form differently, galaxies would form differently. Who knows? And maybe life can or could have or would have formed here on Earth. Yeah, it's a deep mystery why the parameters of the universe seem to be set up to allow life. Although, you know, that's just sort of like life that we can imagine. It's possible that if you tweaked all those parameters, you might have completely different chemistry, but that might allow for different kinds of biology,

different kinds of life, maybe even different kinds of intelligence. So while the universe does sort of seem fine-tuned for us, it might be that other fine-tunings are good for other kinds of beings. All right. Well, the question at hand is, does particle spin affect life on Earth? And so I guess particle spin is something that is a property of particles. Maybe we can get a little bit into that first. Particle spin is a really fun and super weird property of particles.

And it's especially fascinating because the universe seems to have a preference for one kind of spin over another kind of spin. Fundamentally, we don't really know what particle spin is. I mean, you might imagine that it's like a little ball and it's spinning. Problem is that particles are not little balls and they don't really have surfaces. So we don't think that they are physically spinning. But they do have a property which is very similar. to the kind of things we call spin for like the Earth is spinning

and the galaxy is spinning. Particles have properties which have similar mathematical behaviors to spin of like big objects. And so we call it spin even though it's not like technically physically spinning. Right, because quantum particles

are not like little balls, as you said. They're like little dots basically. And so they have this property called spin and if it's not related to it actually spinning, why did you call it spin? Or not use specifically, but you know, the physicist first did it.

Why did they call it spin? They call it spin because even if it isn't actually physically spinning, it is a form of angular momentum. Things in the universe can spin and they can have momentum in the same way that things can have normal momentum. Momentum is just like if you push an object, it keeps going. Or if you don't push it, it doesn't go anywhere. The same thing holds true for spin.

If you spin something, it'll keep spinning, like out in space where there isn't in the air to slow it down. Or if you don't push an object, it won't spin, right? Something floating in space won't spin unless you push it. That's angular momentum. And that's conserved in the universe. That's why if you push something to make it spin, it'll just keep spinning out there in space until something stops it.

But you can transfer that angular momentum to something else, right? You can bump into something else and make that spin. We call particle spin spin because it's a kind of angular momentum. You can take angular momentum and convert it into particle spin and back. So when the universe does its accounting to make sure that angular momentum is conserved, particle spin is part of its balance book. You're allowed to move some angular momentum into that category. So it really is a kind of angular momentum, even if it's a weird quantum kind.

But you said that like regular objects in space can have zero angular momentum or a little bit or a lot of angular momentum. Can particles have zero or a lot of angular momentum? And also, why not just call it angular momentum? Yes, particles can have different amounts of spin. Photons, for example, can have spin up or down or zero. Electrons can only have spin one-half or negative one-half. They can't have zero spin.

They're different kind of particles. So matter particles are all either spin up or spin down by one-half, whereas forest particles, those can be up or down or zero. Can the same particle have zero and then I give it a spin and then it starts spinning? Or is it just an inherent property of that particle? That's a really interesting philosophy question, right? Essentially, you're saying a photon moving through the universe with zero spin, if you give it spin, is it still the same photon?

Well, to give it spin, you have to impart angular momentum on it, which means an interaction. And so philosophically, it is changed, right? It's like interacts with some particle. And you think of that as like being absorbed and reemitted. So I think philosophically, you could think of it as like a new particle, or it's at least a new quantum state. But yes, photons can have zero spin.

or they can have spin 1 or they're going to have spin minus 1. And the spin, it's quantized as well. Like you have a photon with like 3.5 spin? No, you can't. And you can't have photons with like half a spin or 0.729 spin. It's absolutely quantized. So photons have three possible states plus 1, 0 or minus 1. And electrons have two states plus a half or minus a half.

And that's true for all fermions. All fermions are either plus a half or minus a half. They have half integer spins. That's why we call them fermions. They'll observe the Fermi exclusion principle, which means they can't be in the same quantum state as each other. Bosons, which have integer spin, they can hang out in the same state.

So you can have like a million photons all in the same state. Now, you said earlier that spin is up or down, right? That's kind of the possibilities of it. But in space, there is no up and there's no down. So what does it mean for a spin to be up or down for a particle? Well, in the same way that you can pick any axis to calculate, an angle of momentum, you can pick any axis to project a spin. So you have a particle, you pick an axis.

You say, here's my axis. I want to know if its spin is up or down along this axis. And you can pick any axis you like and call it up or down. Typically, what we do is we choose the axis of the particle's motion. And we ask, is the particle spin in the direction of its motion or in the opposite direction of its motion? But isn't then the problem the motion and not the spin? Like if I throw a baseball face up or if I talk.

positive frisbee face up or face down. It's not that it's a whole different frisbee. It's the same frisbee. I just threw it upside down. Yeah. And in the case of particles, you can measure their spin along any direction. Or you can measure it along their motion or you can measure it perpendicular to their motion or in any direction.

And you'll always get either plus a half or minus a half for particles. Okay. So it's just sort of like an arbitrary label you're saying. Like particles have this thing called spin and we're going to, there's kind of two kinds of the spin. There's the upspin and there's downspin. Exactly. And the universe seems to have a preference for particles whose spin is pointed away from the direction of their motion. Like an electron is flying through space in the positive X direction,

the universe seems to have a preference for those particles to spin the opposite direction of their motion, for their spin to be sort of like back along the negative X axis if their motion is in the positive X axis. We call those particles left-handed if their spin is the opposite direction of their motion. I guess it's kind of like a clock, like a clock can move through space where it's either the face of the clock is facing where it's going or the face of the clock is facing away from where it's going or facing back. And so you're saying that particles tend to be the kind where the clock face is facing back. Those kind of particles where the clock is facing backwards where the spin is the opposite direction of motion. We call them left-handed particles. In our universe, we have left and right-handed versions of most particles.

But one of the forces, the weak nuclear force, which is responsible for like beta decay, it will only talk to left-handed particles. It does not interact at all with right-handed particles. So that's what we mean when we say the universe seems to have a preference for left-handed particles. The other forces, electromagnetism, the strong force, they don't care. They're happy to talk to right or left-handed particles. But the weak force only talks to left-handed particles. So it's almost like the universe is not. ambitextrous like the universe seems to prefer or at least favor left-handed

particles over right-handed particles yeah and it's a slight preference right because remember the weak force is a feeble force it is not a powerful force does not control the structure of our galaxies it does not control the structure of your body it does not control lightning right it's not a very powerful force and so it's a subtle effect and this was actually overlooked for years and years and years even well after the weak force was discovered people hadn't really checked to see if it was symmetric, if it talked to both kinds of particles. There was this moment in the middle of last century when people realized, wow, nobody's ever

actually checked this to see if the weak force was symmetric and everybody thought, of course it's symmetric. Everything in the universe is symmetric. The strong force is symmetric. Electromagnetism is symmetric. It would be bonkers if the weak force was not symmetric. But nobody had checked. And so very quickly, a famous scientist at Columbia skipped her Christmas vacation to do this experiment and discover the shocking result that the weak force is not just a little bit anti-symmetric, it's completely anti-symmetric. It only talks to left-handed particles. It was a huge shockwave that went through the physics community about 50 years ago. Yeah, I think we had a whole episode about this experiment that demonstrated the universe has

a little bit of a left-handed preference. And so this preference has pretty big implications in how the universe works and maybe even how life on earth developed. So let's get into right and left-handedness of the universe and life on Earth. But first, let's take a quick break. Imagine that you're on an airplane, and all of a sudden you hear this. Attention passengers. The pilot is having an emergency,

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or wherever you get your podcast. All right, we're asking the question, does particle spin affect life on Earth? And so we talked about what spin is. It's the property of particles. Particles can spin up or down. They can be left-handed or right-handed. And this handedness is something we see all throughout, not just the universe, but nature itself, right?

I mean, in chemistry, they talk about handedness as well of molecules. Yeah, you can apply this principle in general to anything. You can ask if something is left-handed or right-handed. And basically, you're asking, would it look the same in the mirror, right? If you flipped something in the mirror, would you get something the same? You can literally do this experiment in front of yourself with your hands. Like, take your left hand. It's not the same as your right hand.

There's a different orientation of the fingers relative to the thumb. If you put your left hand in the mirror, then it looks like your right hand. The mirror flips your left hand to a right handed sort of shape. But if you just take your right hand, you can't like turn it around or twist it in any way to make it look exactly like your left hand. They're different. We call that chirality, the one is left handed and one is right handed, that they're not the same. Right.

I guess if you're doing the mirror experiment, you would see that maybe some parts in your body are symmetric. and are not handed, right? Like if you take, for example, your eyeball, if you put it in front of the mirror, you can't tell which eyeball it is, your right one or your left one, right? The one eyeball looks the same in the mirror as it does in you.

Or, for example, I think your nose, right? Your nose is also a symmetric. You can't sort of tell which one is the mirror one and which is the real nose, but like your right hand, you can't tell which one it is. Assuming a spherical eyeball, I think that's true. And my nose actually isn't symmetric, so I could tell the difference.

in the mirror because it leans one way instead of the other. That can be fixed, right? We are in Orange County. I mean, basically everybody's getting some work done these days. In principle, an idealized human nose, you're right, is symmetric. And, yeah, hands are not symmetric, right? The real life version of your left hand looks like a right hand in the mirror. Right.

And the same can be said about molecules, right? Like, you can arrange a molecule in a way that is symmetric, where it looks the same in the mirror, or you can arrange a molecule in a way that does not look the same in the mirror. An example of a symmetric molecule is like water, right? Water is H2O. You have two hydrogens with an oxygen in the middle. If you flip it, like if you make the left side, the right side and vice versa, it looks the same, right? It's exactly the same in the mirror. But you can build much more complicated molecules and chemistry of life specifically is filled with complex molecules built off of these carbon chains. And those do have a chirality. They do not look the same in the mirror. There are left-handed versions and right. right-handed versions of basically every kind of molecule. So if you just say the chemical formula, CH4, for example, that tells you what's in it. It doesn't tell you which orientation is it.

Is it the left-handed or the right-handed version of that object? Right. Like CH4, you can take one carbon and four hydrogen and put them in together in one way or in a way that looks like it's a mirror image. That's what do you mean, right? Actually, CH4 is an example of a molecule that probably is symmetric. you have the carbon and then the hydrogens are arranged around it. So I think it does look symmetric in the mirror.

But as they get more complicated, you know, for example, the amino acids and the building blocks of life, these are much more complicated structures. They're not all the same in the mirror. Yeah, like if you take carbon, a bunch of carbon and a bunch of hydrogen and some other atoms, there are two different ways. You could maybe put them together. You could put them together in one way or in a way that looks like it's mirror image,

which is not the same. Molecule just looks the same in the mirror. and it actually kind of affects how it interacts with other molecules, right? Like a right-handed molecule doesn't do the same things as a left-handed molecule. Yeah, interestingly, you can't just mix them. You can't have a bunch of left-handed molecules and a bunch of right-handed molecules and assume that they will all act the same. Because chemistry is like these little building blocks.

He's like tiny little machines made out of proteins. They have to click together in just the right way to activate certain sites, to cleave off bits of a molecule. It's like trying to shake somebody's hand, but using the wrong hand. It just doesn't sort of fit together or trying to dance where both people are leading. In order for the chemistry of life to happen, everything has to match. It means you need like all the pieces to have the right chirality. So you can't mix and match left and right-handed chemistry of life.

Yeah, that's why I fist upon people when I meet them these days. It's just too confusing. But I was thinking it's sort of like Tetris, right? Like in Tetris, you have pieces. And like every piece in Tetris is made out of four blocks. But depending on how you put them, they're symmetrical or not. Like if you have a two by two block, that's symmetric and you can slide that in anywhere. But if you have it like an L-shaped block, then you got to wait for the right left hand or the right side L block to fit a certain spot in your Tetris pile.

And for the chemistry of life to work, it seems like you need to be either all one chirality or all the opposite chirality. And that's exactly what we see. When you take organic molecules and you sort of like distill them from living objects from plants or whatever, you see all one. chirality. All of life on Earth uses left-handed amino acids and right-handed sugars. There's nothing alive on Earth that uses right-handed amino acids or left-handed sugars. That form of life just does not exist. Right, but it's like it's possible to make right-handed amino acids, but all life on Earth seems to use only left-handed amino acids. And once life got started and life starts to make amino acid, it then only makes left kind, which is the kind it uses.

If you synthesize some organic molecule, you like try to make one of the amino acids chemically from basic building blocks, you'll end up with both kinds, left-handed and right-handed. But if you pull it out of life, if you distill it from a living being, you'll only get one chirality. Right. And you're right. We think that life is possible with the other orientation. We suspect that it is, though, of course, we don't have any examples. We think that probably the universe is symmetric in that it would allow for life to have both chirality. but we don't actually know. Well, that's interesting to think about. Like maybe there's a version of humans out there,

maybe in the multiverse or maybe in this universe, that uses only right-handed amino acids. And maybe if we met them, I mean, we could shake hands, but we could have kids together, right? Or even eat their food because our bodies cannot interact with that kind of chemistry. I mean, like some of the artificial sweeteners that are in our foods are really interesting

because they exploit the fact that despite being a sugar and they do interact with your tongue in a way that you can taste them, our bodies can't actually take them apart to use the energy. So we can't metabolize them even though we can taste them because they have the wrong chirality. Interesting. Yeah, artificial sweeteners. You're saying use the wrong handedness of sugar molecules,

which activate our taste buds, but they can't be processed in our stomachs. Yeah, because those are different processes, right? Tasting something, recognizing the sugar. Your tongue doesn't actually break it. down and extract the energy. And so it's like, oh, yeah, that's sugar plus one for you. But then when he gets into your stomach, the little machines down there that take things apart and actually extract the energy and turn it into ATP, they're like, I don't know what to do here. My locks are

not fitting into these keys. So it just passes right through you. Interesting. This is something we've known for a while, right? This was discovered by Louis Pasteur himself more than 150 years ago. He synthesized a bunch of chemicals. And then he also distilled them from life. And he noticed this deference. He noticed that the ones that came from life had only one chirality and the ones that he synthesized himself had both kinds of chirality. So it's been an open puzzle for more than 150 years of why life has this thing. They call it biochirality. But back then, how do we know that a molecule was right-handed or left-handed, right? We couldn't make x-ray it or have super electron microscopes. The way he discovered it was that these chiralities interact with light a little bit

differently. The light can have different polarizations, which is related to the spin of those photons, and that interacts slightly differently with those photons. And so that's how he detected that the chemicals that he pulled out of life were different from the chemicals that he synthesized in the laboratory. And he actually predicted, before we even knew about the weak force or parity violation, he predicted that there must be some sort of cosmic particle asymmetry, which is generating this fundamental asymmetry in life. So like, 100 years before we discovered parity violation, he basically predicted it. Wait, what?

He was thinking maybe the reason that life and earth is mostly left-handed one type of molecule is something like something from space? He was thinking that this asymmetry was revealing a deep asymmetry in the universe itself, right? There must be some sort of cosmic origin to this. So Pasteur wrote, this is in the 1840s, he wrote, quote, if the foundations of life are dysymmetric, then because of dysymmetric cosmic forces operating at their origin, this, I think, is one of the links between life on the earth

and the cosmos. That is the totality of forces in the universe. So that's Pasteur writing in the 1800s before we understood like the quantum nature of these forces or particle spin or parity violation at all. He had the sense that maybe the handedness of life came somehow from the handedness of the universe. Well, it feels like a little bit of a stretch there for the 1800s to make that connection. It might be one of these things where people write a lot and most of their predictions are wrong, but when they do hit the jackpot, people later on dig them out

and like, hey, look how forward thinking they are, you know, the way you can find almost anything you like in the writings of Nostradamus. I wonder if it's sort of like saying like maybe in a way he would say, I mean, I'm sure I know he was a scientist, but maybe in a way he's saying like, you know, maybe God is left-handed and that's why he made humans in a particular handedness or like maybe god is right-handed that's why most humans are right-handed yeah that's another great example of asymmetry right why are humans mostly right-handed and not left-handed we know that it can work both ways obviously but why are humans mostly right-handed and not mostly left-handed it seems like sort of an

arbitrary choice and it makes you wonder like where does that come from is it just random or is there a fundamental reason at the heart of the universe that's creating this asymmetry. That's sort of the philosophy question, right? You always want to know the why, not just the how. Right, right. And we all know we're just here to set things up for the greater discipline of philosophy. But I think, you know, I guess if half of the humans on Earth are right-handed and half of them were left-handed, it would be pretty awkward all the time trying to shake hands with people.

So maybe the whole reason most people are right-hand is just to, you know, make things more social. Yeah, I think that's beyond my pay grade. All right, well, that it's a big question. Why does life on earth prefer one kind of handed molecules and not the other? I guess one reason is that it could have been random, right? Like it just, you know, pick left-handed molecules and went with that? Yeah, it could be basically a coin flip billions of years ago that could have gone either direction. But once you pick one side, it's like symmetry breaking, then you just got to go with it.

Like if a bunch of people are seated at a table and you have like glasses placed between the plates, is your glass on the left side or the right side? As soon as one person picks their glass on the right side, then everybody's going to use the right-handed glass. But they could have picked the left one and everything would have worked just fine. So we don't know if it was just like a random event billions of years ago in the primordial soup that led us to all have this one-handedness or maybe there is a reason. Yeah, I wonder like if there was some competition in the,

in early life billions of years ago, like maybe a bunch of particles started assembling in the left-handed way and a bunch of particles started assembling in a right-handed way. And for a while, maybe there was life could potentially early on. There could have been life with both-handedness. It's just that one

somehow beat out the other. Yeah, it could be. Or it could be that it's selected for, either before life starts or after. It might be that the processes that generate these organic molecules naturally prefer to generate them in a right-handed or left-handed way. Like out there in space, when you have these organic molecules in soups, are there equal amounts of left-and-handed molecules,

or is there an asymmetry there before life even gets started? And then you can also ask afterwards, if life gets started equally often left-and-handed, is there some preference for it? Is one more likely to survive? Is there something about the universe which gives one of them a boost? Right. I think you're asking maybe God is not ampedic.

Maybe got this preference for right or left-handed, and could we see that in the laws of the universe? And so let's get into whether or not there is a connection between the left-handedness of life and the right-handedness of quantum particles. But first, let's take another quick break. Imagine that you're on an airplane, and all of a sudden you hear this. Attention passengers. The pilot is having a... An emergency, and we need someone, anyone, to land this plane. Think you could do it? It turns out that nearly 50% of men think that they could land the plane with the help of air traffic control.

And they're saying like, okay, pull this, until this. Do this. I can do it my eyes close. I'm Mani. I'm Noah. This is Devon. And on our new show, no such thing. We get to the bottom of questions like these.

Join us as we talk to the leading expert on overconfidence. Those who lack expertise lack the expertise they need to recognize that they lack expertise. And then, as we try the whole thing out for real, wait, what? Oh, that's the run right. I'm looking at this thing.

See? Listen to no such thing on the Iheart radio app, Apple Podcasts, or wherever you get your podcasts. A foot washed up a shoe with some bones in it. They had no idea who it was. Most everything was burned up pretty good from the fire that not a whole lot was salvageable. These are the coldest of cold cases,

but everything is about to change. Every case that is a cold case that has DNA. Right now in a backlog will be identified in our lifetime. A small lab in Texas is cracking the code on DNA. Using new scientific tools, they're finding clues in evidence so tiny you might just miss it. He never thought he was going to get caught. And I just looked at my computer screen.

And I was just like, ah, gotcha. On America's Crime Lab, we'll learn about victims and survivors. And you'll meet the team behind the scenes at Othrum, the Houston Lab that takes on the most hopeless cases to finally solve the unsolvable. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. I had this, like, overwhelming sensation that I had to call it right then. And I just hit call, said, you know, hey, I'm Jacob Schick. I'm the CEO of One Tribe Foundation, and I just want to call on and let her know there's a lot of people battling some of the very same things you're battling.

And there is help out there. The Good Stuff podcast, Season 2, takes a deep look into One Tribe Foundation, a non-profit fighting suicide in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission. I was married to a combat army veteran, and he actually took his own life to suicide. One tribe, save my life twice. There's a lot of love that flows through this place, and it's sincere. Now it's a personal mission. Don't want to have to go to any more funerals, you know.

I got blown up on a React mission. I ended up having amputation below the knee of my right leg and a traumatic brain injury because I landed on my head. Welcome to Season 2 of the Good Stuff. Listen to the Good Stuff podcast on the IHeart Radio app, Apple Podcast, or wherever you get your podcast. Your entire identity has been fabricated. Your beloved brother goes missing without. a trace. You discover the depths of your mother's illness, the way it has echoed and reverberated

throughout your life, impacting your very legacy. Hi, I'm Danny Shapiro, and these are just a few of the profound and powerful stories I'll be mining on our 12th season of Family Secrets. With over 37 million downloads, we continue to be moved and inspired by our guests and their courageously told stories. wait to share 10 powerful new episodes with you, stories of tangled up identities, concealed truths, and the way in which family secrets almost always need to be told. I hope you'll join me and my extraordinary guests for this new season of Family Secrets. Listen to Family Secrets Season 12 on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. All right, we are doing some of the pre-work here for philosophers.

We're warming the crowd up here with some interesting thinking about the universe and life on Earth, asking the question, can particle spin or did particle spin affect life on Earth? And so we've talked about how fundamental quantum particles have a spin. They have an up or down spin. And we also talked about how life on Earth has a preference for left-handed molecules over right-handed amino acid. molecules. And so the question is, are these two things related? Does the spin of particles affect how molecules form or do somehow the loss of physics, somehow prefer left-handed amino acids? Let's get into that connection. It is a really fun question. And I was reading this

very long and detailed paper about the connections between particle spin and biochiralty. And actually start out with a bit of a rant, a complaint about calling life left-handed or right-handed because there's all sorts of ways you can define it. So they prefer to define the orientation of our chemistry as live, L-I-V-E, and the opposite orientation as evil, live backwards, E-V-I-L. So this whole paper talks about normal life versus evil life. And this is a physics paper? Or is this a block post?

No, this is a science paper published in a prestigious journal. And somehow calling life evil or live is better than calling it left-handed or right-handed? I don't know. It's a philosophy question. So this is all based kind of on a paper that tries to make a connection between quantum particle spin and the corality or the handedness of life molecules. So is there a connection, Daniel, between these two things? So there is a plausible mechanism for connecting the preference of the weak force to produce left-handed particles and life-selecting for this kind of chirality. There's a plausible mechanism. It's very, very thin.

It's a very, very slight preference, and it's not something we've proven, but it is possible. And it comes down to particles from space, right? Cosmic rays are these particles that hit the Earth at very, very high speeds. And they come from like the centers of other galaxies or they come from our sun. And they're just normal particles, protons, electrons, positrons. Sometimes they hit the top of the atmosphere and they create a big shower of particles. Because a particle hits the atmosphere, it's sort of like a meteor hitting the atmosphere. It heats up and slows down and spreads out its energy.

So you get a big shower of particles on the surface. And this is something very normal. It's something we've been experiencing as living beings on the surface of the earth for a very, very long time. Cosmic rays hit the atmosphere and create essentially radiation on the surface of the earth that interacts with us and interacts with our organic chemistry, specifically our DNA. Right. We sort of can't see it on our regular skies, but you can sort of see it in the northern lights, right? That's kind of what the northern lights are.

Are particles hitting the atmosphere? Yeah, particles hitting the atmosphere. And in that case, getting shunted up to the poles by the magnetic fields. One of the reason that we don't have more radiation here on the surface of the earth is our atmosphere. The second reason is our magnetic field acts sort of like a shield. But some of it does get through and gets down to the surface and affects the way life operates. You know, a crucial element of evolution is mutation. You don't want just to copy the genes of the parents.

you want to try something new, which requires either making a mistake when you're transcribing the DNA from the parent to the child or having a mistake introduced from, for example, a cosmic ray. A muon passing through your DNA, for example, could alter the chemistry of it in the same way that radiation can give you cancer by changing the fundamental operation of your cells. It can also change your DNA. Yeah, and that's kind of an essential ingredient in life and evolution, right? like if you didn't have mutations then life would never evolve it would never change like that's how it started but also like you need mutations just to evolve life because of DNA never changed if it copied perfectly from one generation to the other you would just still have the same organism you

started with you would never evolve or come up with a better versions of the species yeah in order to explore the space of all possible organisms effectively right you need a population that has different abilities and the best way to do that is to introduce random mutation. That's essentially what evolution does. So cosmic rays have played an important part in our evolution. We think it's actually key. Like if you could build a perfect shield so we had no radiation on the surface to the earth, then the history of life on Earth would be very, very different. It might not have succeeded. Right. Well, you would still have mutations. You just wouldn't have them from radiation coming from space, right? And we don't really know what would happen in that scenario, right? Life would evolve very

differently changes the conditions of life. And so what we do know is that the conditions we have here on Earth are the ones that gave birth to us, right, to this kind of life. Right. I guess if we had less of a shielding from radiation from space, we would have had more radiation than maybe too many mutations, right? In which case, we wouldn't have evolved either. Yeah, it's a really interesting question. It's sort of like bio philosophy, like what is the best rate of mutation? We just don't know the answer to that. People theorize and run experiments. But, you know, we have a certain level of radiation. We think that that's a key part of how we evolved to be who we are. All right. So then how does left or right-handedness come into it? Well, it turns out that

these cosmic rays that come from space are not equally left or right-handed when we talk about the particle spin. Because what happens when a particle hits the upper atmosphere is it creates this shower of particles. Typically, these particles called pyons, which don't live very long. They tend to decay and they decay into muons. That decay is done by the weak force. The weak force is the thing that breaks up the pions, it turns it into a muon and also, for example, a neutrino. And because the weak force is in charge at that moment, it only makes left-handed muons because that's all it knows how to do. It doesn't know how to make right-handed muons. It ignores right-headed muons. It pretends they don't even exist. So coming from space,

we're overwhelmed with left-handed muons, which means that the cosmic rays all of a sudden are not symmetric, right? So the environment we've involved in is not symmetric because of the weak force. And those left-handed muons tend to interact with our DNA slightly differently than right-handed muons would. Meaning that most of the muons that come down on Earth are left-handed, not right-handed. Exactly. Those muons are left-handed, and that creates a slight preference for left-handed amino acids. We think that left-handed muons have a slightly higher probability of ionizing left-handed amino acids than right-handed amino acids. Wait, what? Why? Why? Why is it that left-handed muons interact mostly with left-handed amino acids?

It's a very subtle effect, but it's again because of the weak force. The weak force has this asymmetry and has very small effects on the chemistry of life. It can, for example, change the electric and magnetic dipole moments of some of these atoms inside these molecules. So their shape is like slightly different if they're left-handed or right-handed, which means that the muons passing through them are like more or less likely to interact with them because they spend like more or less time within that electric or magnetic atomic fields. It's a very subtle calculation.

Wait, are you saying that the left-handed muons showering the earth, coming down on Earth through our atmosphere, are more likely to interact with a certain type of atom or a certain type of electron that you can only see on the left-handed molecules? Yeah, that's right. Left-handed muons will interact with right-handed or left-handed amino acids, but they are more likely to interact with left-handed amino acids than right-handed just by a little bit. It's not like a complete preference.

Why? Because a left-handed amino acid is different than a right-handed amino acid, not because of any spin. It's just how the particles, the atoms are arranged. So why would the left-handed muon, which is a tiny, tiny particle, care about the giant structure of a molecule? Because when the muon is interacting with that atom, it's interacting not just with the electromagnetic force, but also with the weak force. because the muon feels the weak force. And so there is a difference between the left and right-handed amino acids

because of the weak force. It affects the electric dipole moment and the magnetic dipole moments of these atoms. And so that affects how the left or right-handed particles will interact with them. Are you saying that like a left-handed amino acid is made up of different atoms or different atoms with different spins

than a right-handed amino acid? No, it's the same atoms, right? It's just flipped to be left-handed. And so the arrangement is slightly different. And that gives a different pattern of the electromagnetic fields. And this is a very small effect, right? This is really a tiny effect. It's like second order.

This effect is like three parts in 20,000. Most of the time, these things will be treated exactly the same. Because most of the time, it's the electromagnetic interaction that dominates, which is symmetric. But the weak force sometimes is a thing that mediates that interaction. And so it tends to prefer the left-handed version of these amino acids. But again, just a tiny fraction of the time. Oh, it seems to be like a totally different effect.

Like a left-handed muon, it could have been that a left-handed muon prefers to interact with a right-handed molecule, right? It's just that it just so happens that the molecules that left-handed meons like to interact with a little bit more are the ones we call the left-handed amino acids. Yeah, that's right. Or in this paper, they call them the live choice. And the paper, they go through this very complicated calculation, and they come out with this prediction. They say, we predict that there is a difference. And it has to do with the time the particle spends traversing the electromagnetic field and how the weak force interacts with it. And so they predict this very slight effect.

Again, really, really tiny effect. But the idea is that maybe over millions and billions of years, these cosmic rays introduced more ionization effects in our kind of chirality and not in the evil, the alternative kind of biochirality, which give us a boost, which let us explore these things faster, create more mutations and sort of like adapt more rapidly to changing conditions. And that may be over billions of years led life to have this chirality instead of the opposite chirality because we get more mutations from left-handed cosmic rays. I think it's all making sense now. Because there are many different kinds of amino acids, right?

Like, I think maybe what this writer is saying is that there's lots of different kinds of amino acids, but the ones that are used by life right now, he wants to call those like A. And the versions that are not used by us, he wants to call those B. And so he wants, he's trying to say, or she's trying to say that left-handed muons can, you can prove that maybe that left-handed muons somehow like to interact more with A kinds of amino acids than B kind of amino acids. They're saying that using left and right for the mons and left and right for the molecules is confusing.

Let's just call the molecules A or B. A being the ones that life prefers seems to have preferred here on Earth. And then let's stick to left and right hand for the mons. We're in the article they call A live and B evil. But yeah, we can go with A versus B. Yeah, it sounds a little more benign. I mean, if we do meet like humans from another place and they have the other handiness of their biochirality,

you're not going to let me call them evil humans. No, because how do you know, you're not the evil one. Maybe left-handed humans are better than right-hand humans. I think I've just realized we are the baddies, aren't we? That's right. The enemy is us. We've met the enemy and it is us.

Yes, exactly. So that's the idea. And nobody knows if this effect is big enough to actually have an impact on life at all. There's a lot of dot, dot, dot, dots here. It's like almost the same as Pasteur is saying, like, maybe somehow the universe prefers one kind of chirality. This is a way that the universe does seem to prefer one side of a symmetric pair. You can draw some dots between that and how it might have influenced life.

It's not conclusive to say that this is definitely why life has this chirality. But maybe the idea here is that the kinds of amino acids that flourished here on Earth, flourish because they're more likely to be affected by left-handed nuance, which is what the universe prefers to make. And so in a way, the universe kind of preferred to make the A-com. kind of amino acid or the kind that led to us. At least here on Earth, you know, in our solar system, Earth is the only planet that has an atmosphere which creates these muon showers that come all the way down to the Earth's

surface. Muons don't last very long. They last for microseconds. But because they're going so fast, they actually do penetrate down to the Earth because their clocks are time dilated due to special relativity. So they tend to die off right around the Earth's surface. If the Earth's atmosphere was thicker, for example, they would make a lot of the Earth's all the way down to the ground.

Right, but that's just our solar system. This preference for left-handed muons is universal, right? It's basically a lot of the universe. And so if there are other planets like ours with an atmosphere, and if maybe the very existence of life depends on having that kind of atmosphere, in that planet, the conditions may also prefer the A kind of amino acid that we're made out of because the universe prefers left-handed muons. And so over there, also, the universe will prefer the A kind of amino acid.

Yeah, that's the hypothesis, right? Not yet proven, but that's the idea that maybe this is the reason that we have the A kind of amino acid and not the B kind. So you're saying we're less likely to meet evil twin versions of us out there. We're more likely to meet people who are just like us. Yeah, maybe particle spin will make for happy reunions with aliens. Yes, with non-awkward handshings. Maybe we should just fist bump the aliens when they get here just in case.

Yeah, that always works. I'm up for that. That way, you don't have to have that awkward question when you meet an alien. Hey, are you right-handed or left-handed? Fist bump. All right, well, that's an interesting idea that maybe the universe does have a preference for the kind of life that we're made out of and that we were maybe destined to be the way we are right now.

And maybe particle physics is actually relevant to our life and your life and all life in the universe. enjoyed that, thanks for joining us. See you next time. Thanks for listening and remember that Daniel and Jorge Explain the Universe is a production of IHeart Radio. For more podcasts from IHeartRadio, visit the IHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. Why are TSA rules so confusing? You got a hood of you on take it off?

I'm Manny. I'm Noah. This is Devon. And we're best friends and journalists with a new podcast called No Such Thing, where we get to the bottom of questions like that. Why are you screaming at me? I can't expect what to do. Now, if the rule was the same, go off on me.

I deserve it. You know, lock him up. Listen to No Such Thing on the IHeart Radio app. Apple Podcasts, or wherever you get your podcast. No such thing. Your entire identity has been fabricated. Your beloved brother goes missing without a trace.

You discover the depths of your mother's illness. I'm Danny Shapiro, and these are just a few of the powerful stories I'll be mining on our upcoming 12th season of Family Secrets. We continue to be moved and inspired by our guests and their courageously told stories. Listen to Family Secrets, Season 12 on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts.

I'm Dr. Scott Barry Kaufman, 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, you'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. This is an IHeart podcast.