Daniel and Kelly’s Extraordinary UniverseDaniel and Kelly answer questions about electron spin, quantum fields, and cellular vaults!
Do electrons only spin up and down? Or can they spin sideways too? Our cells contain quadrillions of vaults, What on earth do they do?
Particles are ripples in quantum fields, So can a field exist without them? If you knock on vaults? What does it do to the mouse immune system?
Well, an electron that turns right always turn right? Why is dark chocolate better than whites?
Biology? Physics, immunology, forestry. Uugh, you can never really escape chemistry.
Whatever questions keep you up at night, Daniel and Kelly's answers will make it right.
Welcome to another Listener Questions episode on Daniel and Kelly's Extraordinary Universe.
Oh.
I'm Kelly Wienersmith, and I'm a parasitologist, and I am learning that there's all kinds of biology topics that I just didn't even know existed. And I'm super excited about today's episode.
Hi.
I'm Daniel. I'm a particle physicist, and I always knew there was lots of biology I didn't know anything about.
I guess it's good to know what you don't know.
But my question for you today, Kelly, is when was the last time one of your kids asked you a biology question you didn't know the answer to. Oh, not a daily occurrence over there in the Wienersmith household.
You know, I can't say my kids care about biology that much. I don't. My daughter has been reading these manga books about like cells biology, and like, we keep buying her manga books on physiology and anatomy. And I remember a couple years ago and I was looking through the biology section at Barnes and Noble, and I saw these manga books and I was like, who is the audience for this? Who wants to read mangas about cell biology? And the answer is ten year old girls. And she is absolutely eating it up. But she was explaining to me how cells come from other cells and blah blah blah. And so I know these days I'm asking her the questions, you know, because maybe she knows more about cell biology than I do, as we'll learn today.
That's amazing. I love the idea of educational manca, like manca as a way to teach science. What a great idea. That's fantastic.
She is eating it up. What about you? When was the last time your kids asked you a physics question you didn't know the answer to.
Oh that happens all the time now because my son is taking physics in high school and his girlfriend is taking epiphysics, and so they come to me with tough physics questions all the time. And I got to sit down with a piece of paper and like, Okay, what's going on. You got a bullet hitting a block attached to a swing, which is the whole thing is tied to a squirrel which is running around a bicycle wheel. I mean, like, these problems are insane.
Yikes. Do you usually get the answer?
I always do figure it out eventually, you know there's a method to these problems. I kind of like that actually, And when I teach physics here at you See Irvine, I'm often doing problems in front of like a five hundred person class that I've never seen before because I think it's useful for the kids to see me mess up and make mistakes, or like say, I'm gonna try this with energy. Oh no, that doesn't work, let's back up. Or I'll get the wrong answer and then I'll have to try to figure out why, because I think it's useful for them to see somebody figuring out where things went wrong and backing up.
Yeah, absolutely, And if I don't know the answer, I never pretend. I'm always like, what do we need to do to figure out what the answer is? We'll start with Wikipedia, but then we got to check it, and so here's how you search Google, scholar and blah blah blah.
Exactly, because science is not a list of facts. It's a process for learning, right, and you've got to teach the process exactly. I totally agree.
Yeah, Well, our listeners are teaching us a lot with their questions lately. Today I'm excited. I got a question about an organelle that's founded almost all eu caryotic cells, and I was like, what this exists? Then I had never heard of it before.
So you went and you bought the manga on this thing, and you learned all about it.
Right, it would be a pretty short manga, as we're gonna discover today because actually there's not a lot that we know about this. But you know, maybe manga will be my preferred way of learning about things going forward.
Well, one of my favorite ways to learn about the universe is to get asked a question from a listener that I don't know the answer to, which makes me go and dig into it. In detail, and often when people write us questions, which you are all very welcome to do to questions at danielan Kelly dot org. If I do know the answer, all right, right back. But if I don't, I'll delay the answer by saying, hey, let's talk about that on the podcast, which gives me a week or so to do some research and find the answer. So that's what you can be hearing about today, some questions that either I didn't know the answer to immediately, or questions we thought lots of people might want to hear the answer to.
I feel like you've given our secret away. But that's fine. It's true. Whenever we get a question, I'm like, oh, we'll do it on the show. That does mean I have no idea.
We're sharing the process to Kelly, right, not just the answers. It's all about the process, that's right.
That's right. We'll be transparent.
So send us your questions to questions at Daniel and Kelly dot org, not Daniel and Kelly dot com. That's a very US couple who we hope are having a very nice wedding.
We wish them the best.
Congratulations Daniel and Kelly. All right, but aswer your questions, and on today's episode we have some really fun questions about quantum spin, about little bits of the cell, and about quantum fields.
Let's do it, all right, Daniel, First, once for you.
Our first question is from Bertus, and he's asking a question about the spin of particles, which gives me a great opportunity to try to disentangle a lot of misconceptions about quantum spin. Here's Bert's question.
Hey, guys, I know when you measure the spin of an electron you get up or down. What about if the electrons spins perpendicular to the axis of the measurement, is it still only up or down? Anything in between? Thanks?
Oh, so this is great. So you and I have had multiple conversations about electron spins and you've mentioned many times that the spin is up or down, but it never occurred to me, Well, why is it bupper down? Why can't it be perpendicular? And I just you know, so explain yourself.
Daniel. That's a great question because it makes an opportunity for a nice teaching moment where you can back up and try to untangle a misconception about how electron spin works. And the thing that birds not understanding. Will dig into this in more detail, is that electrons don't like have a spin, and then you measure it along some axis. There really just are two possibilities for the spin. But let's dig into it and first understand, like, what are we talking about when we say quantum spin, right, And Quantum spin is a strange little property of quantum particles that we don't really understand. It's something that we try to describe using our intuition for other stuff, like how things spin in our world, like you see a ball spinning or the Earth is spinning around the sun, and so we try to describe this weird new property and analogy to something we are familiar with, and we're doing this all the time physics, right, Like photons are weird and new, so we describe them as kind of like a particle and kind of like a wave because they have kind of particle eproperties and kind of wavy properties. Quantum spin is something weird and new we've never seen before, but it does have a lot of similarity to the kind of spin we're familiar with, so that's why we call it spin. But it really isn't the same thing, all.
Right, Where to start from there in what ways is it similar to what we see?
Yeah, great question. The thing that makes us call it spin is that it's similar to spin in that it seems to create magnetic fields. Like when you have a charged particle like an electron, and you move it in a circle, like you have a loop of wire for example, that creates a magnetic field. That's how an electromagnet works. How you can run current through something and create a magnet And that's like the basis of motors and all sorts of stuff. So stuff moving in a circle, charges moving in a circle create magnetic fields. Cool. But then we discovered that little tiny particles also have their own magnetic fields, like electrons. When they're not moving in a circle, they have a little magnetic fields. And we notice this because if you shoot an electron into a magnetic field, it gets deflected either one way or the other way, which means it must have a little magnetic field of its own, and it can't have like a magnetic charge. Right. We talked about on the podcast once how there's no like magnetic charge in the universe. All magnetic fields are created by electric charges moving in a circle. So people thought, well, the electron has an electric charge. Maybe if it's spinning, then that's effectively the same as a charge moving in a circle, and that would create a magnetic field. Like if you took a sphere of metal that had electric charges on it and you spun it, that would create a magnetic field. So an analogy, people are like, well, maybe the electron is spinning. That was the first idea to explain the little magnetic field that particles have.
What are they sitting?
So then people thought, well, that makes a lot of sense, right, and then they sat down to do the calculation. All right, if an electric is spinning, well, how fast is its surface going, Like what's the speed of the surface of the electron? And then they realized, oh, actually that would be going much faster than the speed of light. So hmm, that doesn't quite work. Plus a lot of people are like, electrons are points. Points can't spin. There's nothing to spin there if it's like really zero volume, so it can't be physically spinning. You shouldn't have the image in your mind of like a tiny little beach ball that's actually spinning. But it's something very related to spin because it does create magnetic fields and it participates in conservation of angular momentum. Like we talk about lots of times on the podcast, how anglar momentum is conserved in the universe. Like, if you have something spinning in space, it will keep spinning until something slows it down. The same way if something is moving in space, it'll keep going until something slows it down. Well, that angular momentum, what you can do is you can turn it into particle spin. You can like sap the spin of some physical object and turn it into particle spin. So particle spin really is a kind of angular momentum because the universe allows you to slosh like orbital angular momentum into quantum spin angular momentum. So it behaves a lot like spin, and it is a kind of angular momentum, which is why we feel justified like calling it a spin. But it's not like a physical spin. It's something fundamentally different.
You see what I got? Okay, so it's not spinning. But we need to explain why. When you send an electron at a magnetic field, it goes one way or the other way, and there's only two options. And angular momentum is if you send something off in a certain direction, it just keeps going.
That's linear momentum. Angler momentum is if you spin something, it just keeps spinning.
Thank you. If you spin something, it just keeps spinning. And I'm still not getting the connection between the angular momentum spin and why the electron goes one way or another way when it hits a magnetic field.
So the angular momentum comment is just to convince you that spin is a kind of angular momentum because the universe treats it like that. Like the universe requires that angler momentum is not changed. The amount is the same. Like you can have stuff banging into each other, you can do all sorts of interactions. Whatever anglermentum has to be conserved. The amount before some event is the same as the amount after some event. Cool. But there are different kinds of angular momentum, right, Like you can be spinning in place, you can be running in a circle. All those things are angle momentum, and it can slash back and forth from one kind to the other. And this is just to say that the universe includes particle quantum spin among the possible kinds of angle momentum. So stuff has to be conserved, but it can slash into this category as well. So that tells us the universe considers quantum spin to be a kind of angular momentum when it's doing its accounting, and it requires anglermentum to be the same before and after. Quantum spin is one of the possibilities. So it's like when you put a thousand dollars in your bank account, you expect it to still be there when you come back. Maybe it's moved into checkings, maybe it's moved into savings. Whatever, it's still one thousand dollars. This is saying the universe treats this as the same kind of accounting as it does other things which are legitimate physical spin, like orbits and running in a circle and whatever. The universe treats all these accounts as if it's just dotted lines that are the humans draw between stuff. So that's what makes it say it really is a kind of spin. Now the second bit, it can only go one way or the other. That's the quantum piece, And that's what Burtis is asking about, because when you send electrons into a magnetic field, you don't get a whole spread of outcomes. It's not like, well, if the spin is all the way to the left, it goes one way, and if the spin is all the way to the right, it goes the other way. But you can also get answers in the middle. What they saw when they did these experiments in the nineteen twenties was very clear. They either go left or they go right. There's no electrons that go through the middle and nothing in between. That's what's quantum about the spin. It's either up or it's down. And that's what Birth' question is, like, well, what happens if the spin is perpendicular, which way does it get measured? And that's sort of what Birth's question is.
So you've got an electron. You look at the electron before you send it to the magnetic FID. Can you predict if it goes left or right or no? Because you've observed the electron and something collapses and physics is impossible, you.
Can predict if you measure it spin. If you measure it spin and the spin is to the left, then you know it's spin is going to be to the left. When it goes to the magnetic field, it's going to go to the left. So yes, you can measure the electron spin beforehand and know it. You can also leave it uncertain and maybe it's left or maybe it's right, and then you'll know when you send it into the magnetic field. That's when the universe decides, Oh, this one's going to be left or this one's going to be right. So yes, you can observe it.
But if it's not spinning, how do you know if it's up or down? If you don't send it into the magnetic field and then see what it does.
Sending it into a magnetic field is the only way, right. Oh yeah, So if you have like two of these in a row right, and say, for example, you send it through one who goes left, you're like, okay, now I know it's left. You send it through another one of those same devices, it's still going to go left because you're measured it left, it is left.
Got it all right? And angular momentum is concerned exactly, always go exactly. Okay, got it? I'm with you. What's the answer that.
The answer is that you shouldn't think about the electron is having some true spin direction the way the Earth does. Like the Earth has an axis around which it's spinning right, call it the north pole. And you might ask, look, well, I'm going to measure it spin along this axis. Is it more up or is it more down? And that's going to give you my answer. The electron doesn't have some true spin angle and you're just measuring the projection of that along some axis. There's only two possibilities for it. It's either up or it's down. That's what it means to be quantum, not that there is some true continuous set of values that are hidden from you and you're just getting a discrete answer. It's not like electrical engineering where you have like analog waveforms that you're then digitizing into zeros and ones. It is either zero or it is one, and the in between state is having a probability of being zero and a probability of being one. It's not like there some arrow there that you're projecting along the axis. True spin state can't be perpendicular. It's just not an option. It's either up or it's down, or it's a mixture of those two possibilities.
Not a lot of options front.
And you might think, Okay, well, I'm just gonna measure the spin state along the X axis, and then i'll measure along the Y axis. Then I'll measure along the Z axis and then I'll sort of know it in three D. The amazing thing is the universe doesn't let you do that because you can't know the spin direction in two axis simultaneously, the same way you can't like no position and momentum simultaneously. The universe prevents you from knowing that it's like undetermined thanks to the uncertainty principle. If you measure the spin along X, you get either up or down, right, left or right. If you then measured along Y, it scrambles it in X. So let's go back to that experiment we talk about. Say you send it through the magnetic field and it goes left. Now you have another set of those magnetic field devices, but you've rotated in ninety degrees, so it's like selecting along a different axis, and now it goes like up or something. So it's gone left and then it's gone up. Now send it through the original device again, and you might think, well, I know it's left right. It was left before. It's got to be left again. But no measuring it along the up down axis has scrambled the left right information, and so now it might go right.
So that doesn't sound very conserved, Daniel, what happens.
What happens is that the interaction has scrambled the angler momentum, so the machine itself has absorbed some of that angler momentum.
Physics is trippy.
Physics is trippy. So the bottom line, Bird is that you can't think about the spin of this particle number one. It's a physical spin. It's a quantum weird thing which is similar to spin, but not really exactly the same. And you shouldn't think of it as being like some true vector that you're then projecting into X or y and that has some like true valley that could be perpendicular. It can never be perpendicular. It's either up or down or some mixture of those two. There is nothing in between.
All right, Wow, a rare instance where physics has a clear answer. Ooh oo oooh slice. But let's see if it's it's intelligible, all.
Right, brut tell us if we clarify that or just confused you.
Hey guys, as always, thanks for the great explanation. Love listening to your podcast.
All right, So onto something completely different. We got this amazing question from Ryan about an organelle that I didn't even know existed. So let's hear Ryan's question.
Hi Kelly, Hi Daniel, Thank you both so much for your wonderful show. I've just become aware of the existence of this cell organelle called the vault. I'm so surprised and fascinated that a structure that's apparently so common in cell biology should be so mysterious to us still, and that it was discovered so recently. Also, what a name for something so mysteriou is the vault? It'd be great if you guys could bring us up to speed on the state of the science and the understanding in relation to this crazy little thing. What do we think therefore, how did they get there? And how did they avoid our detection for so long?
Thank you so much, Daniel. Have you ever heard of the vaults?
I've never heard of the vault. I've never heard of a part of the cell that started with the before, like the mitochondria. I guess the nucleus. It seems especially important. But I'm also just not one hundred percent clear on what an organelle is. Is it a miniature piece of the cell in analogy to like how my liver is an organ in my body. It's like a specialized component of my body is an organelle, like a specialized part of the cell that does one particular job.
Yes, yeah, that's a great definition.
So why they call it organelle? Is it like organito or something like that?
I think yes, I think it is like organito.
I think organito is cuter.
Yeah, I no, I agree. I don't know who we write to submit these recommendations to, but let's get on that all right.
So tell us about the organito called the cell? What does it do? Why does nobody know anything about it? How come I've never heard of it before?
It's all amazing, Okay, So you find it in u caryotic cells. So these are cells specifically that have nuclei that have a membrane and like so inside the DNA is sort of stored inside these nuclei. So like when we talk about prokaryotic cells, we're talking about bacteria and Archaea and just about like everything else is eukaryots. So it's like everywhere, and it's bigger than a ribosome. So like I think most of us learned about ribosomes in biology.
I don't know if I should be impressed by that, because I don't know how big a ribosome is.
I don't really have a good like gut intuition for how big a ribosome is, but I do know that in cell biology or in biology, I was taught the thing that looks like sort of like a big thick squiggle, you write ribosome next to that. The point that I'm trying to make is that it is bigger than a thing that we have known has existed for a really long time, and so it's surprising that we didn't also know that this existed for a really long time.
So not really crazy tiny. It's not like it's hiding because it's super small. It's like kind of a big component. It's like not understanding what a toaster is in your kitchen.
Yeah, exactly, that's right. It's big enough to see and there are lots of them. So there's like ten thousand in each cell. Whoa, yeah, so in our body you might have as many as one hundred and sixty quadrillion vaults in you.
What that blows my mind.
I know they're huge, and so what they are. So it looks like if you've ever been in a cathedral and you've looked up at the ceiling. The folks who discovered this organelle felt like the ceilings of a cathedral, which are sometimes I think called vaults, kind of looked like this organelle, but it would be like two of them put together. So to me, it kind of looks more like a barrel and the inside is empty and it's mostly made out of three proteins, and then it has a little bit of ribonucleic acid in it, so a little bit of RNA.
So hold on, I have to totally adjust my mental picture here because when you said the vault, I was thinking of a safe that there's some like deep secret about life in the universe stored inside ourselves, and today we're gonna crack al Capone's vault or something like that. Now you're telling me I have to replace it with like the idea like a little capsule. It's like a little thing that holds stuff. So it was a little bit like a container.
Yeah, and it's empty in the inside. So yes, you're your thought. I mean, we are not going to crack al capone safe today. That is for a bit of a spoiler, we have not really cracked the vault yet.
Let's get Heraldo on the show and maybe you'll help us out.
Oh yeah, yeah, let's definitely recommend Heroldo's shows to our listeners. All right, So you've got this like compartment. You have loads of them, and it was discovered for the first time in nineteen eighty six, Wow, by Nancy Kadersha and Leonard Rome. And the reason they discovered it was an accident. So they were looking at vesicles, which are these little things that you find in cells. They're another organito that sort of moves things around. And while they were trying to like get a bunch of vesicles together for their experiments, they looked in their sample and they were like, oh, there's all of this like contamination, and it was a little bit hard to see, but they were like, okay, well, let's try to get the contamination out. And then they realized like, oh wait, this isn't contamination, this is something else that was in the cell. And they realize the reason it had been missed for so long is because when you're trying to look at the inside of the cell, you often put stains inside of a cell that binds the RNA, and the vault is only about four percent RNA, so it's staining, but it's staining in a very like light and easy to miss way. So a bunch of people had been looking at the stuff that stained with the RNA, like the vesicles and missing the vaults. So this group just got lucky that they happened to like get the vaults with the rest of their samples of vesicles, and that they noticed this like junk in the background.
And they weren't using staining, so they didn't miss the vaults.
They were using staining, but they looked at the sample close enough, and instead of ignoring what looked like junk in the back background, they were like, wait, that junk all has like the same shape and there's a lot of it. What is that? And then they were like, holy crow, a whole new organelle.
Wow. I think that says something really powerful about science, that you know, often what we do is imperfect, and we tried like the only possible thing first because we can get some information, but then we sometimes forget that that's limited or that it's made some assumptions, and we don't always go back and like re explore that understand like what are we missing if this is the only thing we're doing. You know, it's sort of like the example of like, well this works in mice yeah, yeah, we can do it in mice, doesn't mean that it's going to work anywhere else. And we've learned something universal, Right, it's fascinating to then crack these doors open. What was that moment like for them? Do you think that they realized, like, wow, all of this is actually something fascinating.
It sounds like they were pretty excited by that moment, And yeah, I agree, like what we know about biology is limited by the tools we have, and sometimes we don't even realize that our tools are limiting what we know about But my sense is they were pretty excited, and they actually had the lab members they all sort of like pitch different names for what to call it, and they had a little bit of a contest.
Do you have the alternatives? That would be amazing.
I wasn't able to find the alternatives.
Organito face wasn't up there.
Oh man, society has been robbed of that opportunity. But the vault is a pretty sweet name.
I think it's very cool, Yes, very dramatic.
Yeah, And so, as I mentioned, it's found in eukaryotic cells, and it's found in like very similar ways in all of these eukaryotic cells. So often when you find something in biology, and you find it in lots of places, and in all of those places it looks exactly the same. That suggests that evolution is doing something to stabilize it. Like, this has a really important function. We're not going to tinker with it because tinkering with it can break it. You need this, it can't.
Be broken, and it's common across eu caryots. Means it provides something really basic. Right. This isn't like, hey, this makes the wings on a hummingbird really really light. This is like essential to some foundational part of life. Right.
That was the initial hypothesis, which to me seems totally reasonable. And there are some places where it's been lost. So for example, fruit flies, which are like, you know, a model that's studied in biology all over the place, and yeast, which is also studied a lot, they don't have vaults for reasons we don't understand. So it's got a bit of a spotty distribution, but most organisms do have it. Okay, so what do we think done?
Yeah, tell us Colleen, crack the vault open for us.
Yeah. So the answer is, actually, we don't know. So biology biology, I know, it depends. So one hypothesis is that it's important for transporting toxic stuff that's in a cell out of a cell. And the reason we think that is because there are people who have tumors and when they've gotten their chemotherapy or there are various drug treatments, it looks like the vault isn't involved in making those drugs work less well by shuttling it out of the tumor cells. And so the thought was that this vault is going around and anytime there's something bad in the cell, and chemotherapeutic drugs can be pretty toxic, you know, they're trying to kill cancer cells, the vault would like put it in the middle of the vault, shuttle it to the outside of the cell, and then dump it back outside of the cell. But you know, chemotherapeutic drugs were not like a common part of our evolutionary history and they exist not in the rest of the animal kingdom for the most part. So the idea is that maybe anything toxic they move. There's some thought that they're important for like the immune response, like maybe they could encapsulate a virus and shuttle that outside of the cell. There was an observation that the vault connects to the inside structure of the cell. So the cell has like essentially what you'd think of as like a lumber structure that sort of like holds it up. It's got scaffolding, and it was attached to it, and so there was some idea that maybe it attaches to that and moves around the cell and transports things like take it from the nucleus and bring it to another organelle orgin eto. But at the end of the day, we don't actually have a good answer. And so one of the guys who helped to discover it, whose last name is Rome, he joked that actually the purpose of the vault is to fund his lab because he had spent fifteen years trying to figure out a function. And they have some like tantalizing associations, but at the end of the day, no one has been able to pin down this is what the vault does, and we're sure and this is his main function.
Well, help me understand why it's so hard to figure out. I mean, I understand, like when we're talking about quantum particles, one of the challenges is that you can never really zoom in and see them and watch them. But here we're talking about like kind of big biological things that you could, in principle see under a microscope. Why can't we just like watch as sell in action and say, like, oh, I see what the vault is doing. Like imagine you come into a city as an alien, You're like, what are all these male people doing. Oh, they're going from house to house delivering letters. You'd figure it out by watching what they're doing. Is that not possible for some reason or oversimplifying it? Why can't we just watch the vaults and figure it out?
Yeah, So here's my best guess as someone who doesn't do cell biology. So a lot of times what's important is important in the system that it's found. And so for example, if you're studying this in a mouse, you can't watch what's happening inside of a mouse cell while it's still inside of the mouse. And so if you really want to understand what it's doing. Often if you just take a mouse sell out, for example, and you put it in a dish, then it can't do a lot of the stuff that it usually does, Like if it's involved in the immune system, it's you know, can't signal with the other cells.
And then native question because to image a mouse sell you have to remove it from the mouse. You can't like put a whole mouse under a microscope and say, like, I'm going to look at this cell on the surface and see what its vaults are doing.
That's right. Yeah, So to stain and see what's happening inside of a cell at that level, I think we still need to put it under very specialized microscopes and cameras, and it can't be inside of the mouse while it's happening.
Well, there's your answer. We need to develop technology for a whole mouse microscope.
There you go, there, you get right, and then if we could see that, then maybe we'd have all of our answers.
All right, So you've got to take the mouse sell out do specialized stuff. Then that changes what the cell is doing, which makes a lot of sense. So we don't necessarily get a clear picture of the cell in its actual action.
And I don't actually have enough experience with imaging to know how easy it is to stain things inside of a cell that are this small and then still watch what's happening inside of cells like in live time. It's possible we might have to indirectly do things like somehow make a cell or figure out a cell line that makes more vaults than another, and then expose those two different cell lines to chemotherapeutic drugs, and then you can say like, Okay, this cell line split the chemo therapeutic drugs out more than the other cell line, and this one had more vaults. And so you know, you're indirectly trying to figure out what's happening based on the responses without being able to actually like be in there watching everything happening in lifetime.
Wow, So out, what are people doing right now to study it? What is the room lab writing grants about right now?
According to an article that I read that came out through the Royal Society, the answer is pretty much funding agencies have gotten tired of paying for trying to figure out what the vault does when they have no answer. And so doctor Rome, I think, is emeritus now, so he's retiring and trying to get other people excited about it. I'm going to step back really quick and mention some mouse works. So you wanted to know, like, how do you study this? So one of the ways that we've studied it is we knock out the information needed to make the proteins in the vaults, and then you look to see what happens to the mice that are missing these proteins. And this is what I think was the most interesting when I was doing the research. So when you like knock out one of the proteins, maybe tumors grow a little bit more in those mice if they have cancers.
And just to be clear, knocking out means removing the genetic code so that the cell doesn't know how to make the vaults anymore.
Exactly or make a component. So we mentioned at the beginning that the als are made out of three main proteins, So if you're knocking out the code to make those proteins, then maybe you'd get a vault that is like you know, it's like a basket that's missing some of the weaving because one of those proteins is missing. So it was a little bit associated with tumor cell size. There was another one that was a little bit associated with immune system functioning, and when you knocked it all out, maybe the mice grew a little bit more slowly. But like you know, the initial prediction was that this must be crucial for life because you see it everywhere and it's so conserved by evolution, but you knock it out and the animals seem okay, And so what is this doing? And so I don't know what the answer is. No one does. But you know, I wonder, is there's something that we haven't done to these mice in the lab yet, Like, you know, if you expose them to radiation, do they all just like die immediately? Is there something that we haven't tested yet? And under those conditions vaults are crucial. But at the moment you can knock this stuff out and the animals seem to do okay without them.
Well, here's the sort of basic evolutionary biology questionesting that it's conserved, which you must mean it has an important function. I think the implicit argument is out there in the wild is probably getting knocked out cosmic rays or random mutations. And if it didn't serve a function, then those knockout animals would thrive. But would they necessarily be selected for? Like, is there an advantage to not making the vault? If there's no cost to making the vault, can't you just sort of stick around and hang out as part of our genetic code?
Yeah, okay, so let me see if I understand the question. So, first, I'll note that if you make one hundred and sixty quadrillion of these, there's probably some cost to making that many of them, and there's something we're not understanding. So maybe something that I'm about to say is wrong and we just don't realize it. But if you make that many, it seems like there's got to be a cost, and if they weren't producing some function that was pretty regularly needed by organisms, you would expect them to not keep paying that cost, right, Okay, So for radiation to knock the vault out, it would have to mess up cells that are inside of the new gleist that code for the proteins in the vault. Like, I don't know how often that's happening, so I'm not quite sure I'm a understanding the radiation part of your question.
I was just wondering if nature has done these experiments essentially removing the vault from animals through random mutation or radiation or whatever, and then competed those no vault organisms against the vault organisms, And I was wondering why, if there's no benefit to the vault, the no vault organisms, which must exist also in nature, hadn't outcompeted everybody else.
Yeah, that's a great question, and that might be where the vaultless fruit flies and the vaultless yeast came from. And I think there's plants without vaults. So I think an important question for biologists to ask is do we actually need these All these organisms can live without them, and why are the rest of us holding onto them if they seem so inconsequential. Why are we making one hundred and sixty quadrillion of these things if we don't really need them? And I don't think we know.
And maybe that's why I'm so tired of the evenings, right because I spent my day building all these vaults.
That's right, that's right. Wait, give it a break, body. We don't need these things, and they're not even good when you have cancer. Sometimes you asked what are people working on now? I did come across a variety of papers where people are trying to figure out how to take advantage of the fact that you have this organelle that's empty in the inside, that is maybe able to move around the cell and deliver things from place to place. Could you use it as a way to deliver drugs if you could sort of hijack its use. So folks are now trying to figure out if vaults can be used to our benefit in some way, even though we don't know what their initial purpose is supposed to be.
I'm imagining like those little capsules that you can send through the hydraulic tubes or I guess the air pressure tubes at banks and stuff like that. That'd be pretty cool to take advantage of that.
I loved those so much when I was a kid. I'd have my mom pull up a little farther so that I could be the one to press the button. And oh man, it was better in the eighties and the nineties. No, it wasn't.
So if we're still discovering essential components of the cell that make up a significant fraction of its volume, are there still things that we haven't figured out their discoveries in the future, like big parts of the cell that we have never seen. For whatever reason, I.
Feel like there's gotta be Like I have this vague memory of not that long ago, there was like another major nerve that was discovered, and I think the idea was that we had like mapped out the nerves in rodents, and so we thought we knew where they all were. But turns out humans have another one that we had sort of missed until recently, and which is not too surprising. But I do think there's still surprises left to be uncovered.
Yeah, well, that's what makes biology exciting, right. Not only is it super relevant, but there's lots of unanswered questions.
Right. And speaking of unanswered questions, Rian, is this giant shrug that we're sending your way sufficient to answer the question that you sent us?
Let's find out, ah, Kelly, Wow, as far as shrugs go, that was spectacular. Yes, if you're gonna have a non answer, it can be a non answer full of so much interesting information. I think that's even better than knowing what it is. What an incredible mystery. We have quadrillions of these things, and the answer so far is maybe they don't do much at all.
Wow.
Wow, that's gonna keep me thinking for ages. Yeah. That's brilliant. Thanks so much. I knew you guys would make something great out of this, and I'm so glad I found something that was new to you as well. I'm definitely gonna refer to them as organitos from now on too. That's adorable.
Thank you, Okay, we are back and we are answering questions today from the tiny little things in your cell to the tinier little things that they.
Are made out of. And now we have a question from Kurt about particles and fields and what's possible out there in the universe.
I know in quantum mechanics there are fields and can become excited to form particles, like you got the electromagnetic field with the photon, the Higgs field with the Higgs boson. Could there be a quantum field where it's not possible to form a particle. I've never heard of such a thing, so was wondering if there always must be at least one particle for each field. Thanks.
Ah, this is another one of those great questions where it made me think, oh, yeah, I've heard Daniel say stuff over and over again and never thought, oh, well, what about blah blah blah. So I guess I had always thought of quantum fields as being sort of like a wave, and I guess that makes me think of the ocean, and ocean waves have ripples. Is a field more like a blanket held taut without ripples? Like what does a field look like?
Yeah, that's a great question. And the answer depends on the temperature. Like in the early universe, when all the fields were totally filled with energy, a big, frothing mess. It was more like the ocean, and you wouldn't think about like individual drops to it didn't really make sense. But now the universe is old and cold and dilute, and the energy is mostly spread out, and for most of the universe the fields are empty. It's more like a dried up sea bed with a few droplets on it, right, And those droplets are what we call particles, And so it sort of depends a little bit what phase of the universe we're talking about. But I want to congratulate Kurt on asking this question for exactly the reason that you just mentioned. I think to really understand something, you have to ask yourself questions about it. You're like, all right, you're telling me it works like this, but then what about this scenario or what about the opposite, or does this have to be true? And it's that process of like turning it around in your head and poking it from all sides that builds that model in your mind that lets you then manipulate it and then become fluent in it and that's what doing physics is. So congrats Kurt, and I want to encourage everybody out there when you hear an explanation on the show, really try to do that. Say does this connect with this other understanding or what are the limitations or in what situations does that break down? And if it's not connecting in your head right to me, I will help you sort it out, or.
We will sort it out for other people, because I think a lot of times when the listener has a question, that's a question that a lot of people have either thought or if they didn't think it themselves, when you say it, they're.
Like, oh yeah, what about yeah exactly.
Which was certainly my response when I read this question.
So let's dig in by reminding ourselves what we mean when we say particles are ripples and quantum fields? What is that anyway? And it's sort of a historical tour through what we've thought about particles, And check out our whole episode on what is a particle anyway? The short answer to which is we're really not sure, but we have some models for it that are probably wrong. But you know, his hysics somehow a head of biology, but still getting nowhere. So intuitively, you might think of a particle as like a tiny little dot of matter, and that's what we thought, like one hundred and fifty years ago discovery the electron. We're like, okay, there's something inside matter that has spin and charge and mass and all this kind of stuff, So start with a little dot of manner. But then we saw that these things were actually controlled by wave like mathematics, you know, we saw interference effects. We're like, it doesn't really make sense to think of this as a tiny speck. It's really more like a wave. Then we introduce this quantum wave function, which is controlled by the Schrodinger equation and tells particles where to go essentially, and we have this confusing particle wave duality, which I think is more misleading than clarifying, because really it's all about the wave. The particle is the observation where you see the wave, but the wave controls everything. It tells you where the particles can go. Like in relation to quantum smin as we were talking about earlier, the wave function tells you do you have a forty percent probability of going left or sixty percent probability or a zero percent probability? The wave controls everything. We discovered like fifty years ago that there was also sort of an important limitation there, which is it really only lets you think about one particle, Like you have an electron flying through space. You can describe the wave function of it and what's going to happen whatever, And it's hard to talk about two electrons or twenty electrons, and what about electrons that are being created and destroyed constantly. It's sort of like trying to tell a story about one electron, but it's really just part of a larger tapestry. And now you have lots of stories you're trying to all tell. People found a way to unify all those individual stories together into a field theory. So rather than talking about any individual particle, they're like, let's think about all these different waves as part of one bigger sheet there. Instead of having this wave over there and that wave over here, let's integrate them into being ripples in one unified field.
So when I'm trying to picture a ripple, should I picture a bunch of electrons? And like, you know, so I'm thinking about like a sine wave even like the amplitude, is it a bunch of them coming together? To form an amplitude or is each wave a separate particle? What constitutes a ripple?
I think the closest description is that each wave is a separate particle, and art with a classical field theory like electromagnetism, we say that photons are ripples in electromagnetic fields. And Maxwell understood this long before we had quantum mechanics, and he thought about photons as like, Okay, you have a ripple propagating through the electromagnetic field. But let's be clear about what that means, because a lot of people are imagining something moving like a sign wave, like it moves up, it moves down, it moves up, it moves down. That's not what's happening, right. A photon moves in a straight line. What's oscillating is the field. What is a field anyway? Exactly? A field is a number at every point in space. So imagine a cube of blank space, right. All you have in your mind right now is just a black cube, and then at every point in that space, put a number. There's a seven here, there's a zero there. It's mostly zeros, right, So put all zeros in your field, and put a one in one spot and then how that one move through the field. That's a ripple in a field. Right now, you can describe the relationship between numbers of different points in space using a mathematical function. So instead of having a one, have like a one and then a zero, and then a minus one, and then a zero, and then a one and then a zero and then a minus one. That's like a sine wave right now. It's not moving up and down. It's the values of the field itself that are described by the mathematical function. So that's the ripple. It moves along the line like a photon moves in a straight line. It doesn't go up and down or side to side or anything like that. But the values of the field along that line are changing. And a photon is more complex than just one number. It's a vector, so at every point in space it has a direction as well as a magnitude. You don't need to understand that in all of its detail. But the point is the particle is a ripple in the values of the field. It's not physically wiggling through space.
Got it, all right? I feel like I have a much better visualization now.
All right, So that's classical electromagnetism and understanding the photon is a ripple in that field. But what we do now are quantum fields. We say, all right, the field can't just have any value, like at that point in space you could have a zero or one, or a zero point seven, two nine, or a one point four to twenty seven. There are only certain values allowed. There's a ladder of possible values, and so you can have like a zero, or you can have a one point seven, or you can have a three point four, you can have a fourteen point one. There's a certain set of values there that are allowed, and those are the ones that are solutions to the quantum equations. Like quantum equations don't have solutions for every value. They have a ladder and that comes out of the mathematics of quantum field theory, and it comes from constraints and boundary conditions. And you know, we don't have to necessarily get into why quantum field equations have only certain values, but they do. And when you take a classical field theory and you quantize it, what that means is you're imposing the mathematics on it that generate only a certain spectra of solutions. So now you have your quantum field, and it can either be zero or it can have the first solution or the sex and solution or the third solution, and we call that having zero particles or one particle, or two particles or three particles. So the number of the step you are in the latter is the number of particles we consider in the field.
Okay, so inside of that box, there's a finite number of ripples that could happen because there are steps and you can only take certain steps. And it's a big number.
Not necessarily a finite number. You could have an infinite number, but they're discrete, right, There's not any possible number could be a solution. There might be an infinite number of solutions, right, but there are gaps between the solutions.
All right, got it?
And so that's what we say. Like the field is in state two, that means there are two particles. The field is in state nineteen, there are nineteen particles there. So that's what we mean when we say the particle is a ripple in the field. It means that there are solutions to the field equations, and they're just like the Schrotinger equation, but they're sort of generalized to describe more than one potential particle, and they can describe multiple particles moving through the field, like photons. The electromagnetic field can have lots of photons. There are lots of photons in the universe. There are all ripples in the same field.
Right, What is a particle, It's a state in the field. So state in the field just tells you how many particles are in the box, or how many particles are possible at a particular location in the box.
Yes, so at any particular place in the field, there are solutions, and those solutions are localized because particles aren't the whole universe. Some of them are actually bigger than others. Depends a little bit on their momentum, Like if you know it's momentum really really well, then it's uncertain over space, and particles can actually be spread out across really vast distances in the field. That's a whole other confusing thing. But essentially you can have particles at different locations, but at each location you can say I have one particle or two particles, And some fields can have multiple particles in the same place on top of each other, like you can have nineteen photons in the same place the field is fine with that. You can't do that for electrons because electrons are different kind of particle. They're fermions. They don't like to occupy the same place at the same time unless they have something else about them that's different, like their spin is different or something. So they obeyed different sort of quantum rules because the field itself is different and so the solutions come out differently. So some fields you can only have zero one particles. Other fields you can have like as many particles as you want, okay, And there's lots of different kinds of fields. Like the simplest field is the Higgs field. The Higgs field is just a number in space. You might hear described as a scaler field. That's what it means. It means just a number. Scaler is a fancy way of saying a number. Other fields are spinner fields, which are like numbers, but they also have another dimension which can be up or down, like electrons we talked about, kind of spin up or spin down. There's spinner fields they have two possible numbers there, and there's vector fields like photons have three possible numbers. And there's even more complicated fields that you can have a tensor. A tensor is like a vector, but more like a matrix, right, So it's like many possible values there, So it gives very complex behavior. And if gravity, for example, is a quantum field, people think it has to be a tensor field, which makes the graviton a very complicated particle with five possible spin states, et cetera.
No wonder, y'all haven't figured that out yet.
Gravity is hard anyway. Fields can do all sorts of really complicated stuff. They can interact. You can get energy going from one to another, which is how we describe particle interactions. But at the end of the day, when we say a particle is a ripple, we mean that there is a field there with a ladder of solutions, and the number of particles is sort of like which solution are you on? If you're on the fourth solution from the bottom, we say there are four particles there.
All right, So it sounds to me like in order to have anything that qualifies as a field, there has to be some particles there, right. The answer can't be zero in every location.
Yeah, it's a great question, Kurt asks, and your answer is actually really cool. One I mean, I think Kurt is asking if there's a field where you couldn't possibly have particles. It's totally possible to have a field that's empty of particles, where there's possibilities for particles, you just don't have the energy, right, there's just not enough energy to make any particles. That's totally possible. I think Kurt's asking a different question, which is, could you have a quantum field where no particle is even ever possible, where just can't do that kind of ripple. It's a really interesting question because you might think, like, well, particles are a special kind of ripple in these fields, and it has to solve the equation, and could you have a field whose basic properties prevent there from ever being any solution like that? Like are there fields with no solutions at all? And it's a really good deep question about quantum field theory. The answer is basically no, because the simplest field you can imagine like the Higgs boson, but then even remove all of its interactions, the simplest field has to have some kinetic energy, has to be able to wiggle. That's what fields can do. And as long as you have a field that can have kinetic energy, and it basically motion, and then you can find quantum solutions. So essentially every quantum field, by its nature, has quantized solutions, and steps on that ladder are particles, and so essentially every possible quantum field has particle solutions to it. Even the very simplest scenario, even the most basic, minimalized, bare bones field, would have particles in it.
What I love about this question is that it seemed like it was going to be very simple. Even simple questions can be deceptively sort of complicated to really understand them completely. But I learned a lot. Let's see if Kurt did.
I also learned a lot. Thank you so much for the response. I found it quite interesting and thought provoking. I haven't thought about how quantum field theory generalizes from the simpler classical field description with Turner's equation, the idea that each solution to the field equation corresponds to the number of particles. That makes perfect sense. Your answer helped. Thank you.
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