Why is the strong force better known as the “color force”? What’s the best way to think about protons and quarks? What do the Three Musketeers have to do with anything? I discuss these questions and more in today’s Ask a Spaceman!
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EPISODE TRANSCRIPT (AUTO-GENERATED)
First off, we're gonna get small. Way small. Smaller than the smallest thing you can possibly imagine. And I know you're thinking, you don't know my thoughts, Paul. I can think of some very small things.
Well, you're wrong. Because we're about to talk about things that are even smaller. We're zooming in. Like, think of think of you. Think of your body.
Your body is made of organs. Your organs are made of tissues. Your tissues are made of cells. The cells are made of molecules. The molecules are made of atoms.
The atoms have cores inside of them called nuclei. That's how small we're gonna get. And a good number to have in your head for small physics, if you wanna think of small physics, this is the number you wanna think of. It's a femtometer. Femtometer, which I will pay you 1 American dollar if you say that word out loud to somebody today.
That is not true, but my my heart is there. Femtometer. Femtometer, that's 10 to the minus 15 meters. That is a millionth of a billionth of a meter. To give you some sense of perspective, instead of going small first on what you think big, imagine inflating yourself, like you just grow so big and you get bigger than your city and you get bigger than your country and you get bigger than your you're inflating, you're inflating, you start to encompass the solar system.
You go out to be the size of the Oort Cloud that is, you know, up to half a light year away. Like, so you're a light year across. That's how big your body is. Imagine being so big that when you want to move your arm, when you thought, hey, arm, why don't you wave? It would take months, even years for the electrical signal to actually reach your arm all the way across the solar system and slowly wave back and forth.
Like, imagine just imagine the difference between you and this size now, your current size, and if you were inflated to be bigger than the solar system. That's the difference between one meter and 10 to the 15 meters. Now imagine running that in reverse so that your current body feels that impossibly big. That is the difference between one meter and 10 to the minus 15 meters. One meter and one femtometer.
That's how small we're gonna get. And at these scales, things are different. At these scales, quantum mechanics rules here, but that's that's another show for a large part. But at these scales, there's a new force. A new force shows its strength, becomes apparent.
We're we're used to in our normal everyday world of walking around here on the Earth and doing our Earthly things to pretty much two forces. We care about gravity, that's what sticks us to the ground, and we care about electromagnetism, that's electricity, light, magnetism, all that stuff. It's just two forces. Really, two forces govern your entire everyday world. But those forces are weak.
They're nothing. They're minuscule compared to this force that shows up at a femtometer. There's a force that is so much stronger than gravity, so much stronger than electromagnetism. And I'm not gonna call it the strong force because that's not quite its name. Instead, I'm gonna call it the color force.
Yeah. The color force. And don't worry. We're gonna get there eventually. The color force is this really, really strongly acting force that only behaves at small scales.
And this color force is a beast. It's complex. It's not intuitive. It doesn't behave like any of the other forces. It's complex.
Did I already say that? Yes. Good. Because it's double complex. As an example of this strangeness of this color force, look look at the proton.
The proton, it's a particle. It's a tiny little thing, and if you didn't already know it, then I'm about to tell you that the proton is actually made of smaller particles. So a proton itself is not a fundamental particle. It's made of something else. These smaller particles that make up a proton are called quarks.
Quarks. Because the guy who figured out that quarks might exist thought that the word quark would be a fun name and he figured out first, so his suggestion stuck and here we are. So we have to call the things that make up a proton quarks. And it turns out that a proton is made of three quarks glued together. Okay, fine.
Here's some questions you might reasonably ask given that bare statement. What does a quark look like? What does the gluing inside the proton do, you know, glue those quarks together? And if a proton is just a bunch of quarks and those are glued together somehow, then how do a bunch of protons glue themselves themselves together to make, you know, a nucleus like an atom? And why is it three quarks, not 10 or one or 42?
These are all good questions. The short answer is because, but let me flesh that out a little bit about why a proton is made of three quarks and what's doing all the work. First, I want you to stop thinking of a proton as, a bag of other smaller particles, even though you may have just started thinking of a proton as a bag of smaller particles because that's how I introduce them. But if you if you just imagine, if you're like, oh, a proton is is like a little case for three other particles and I can crack it open and then there's those three little quarks inside. It's not that.
It's not just three quirks hanging out over drinks having a party. No. A proton is something else entirely. A proton is like the three musketeers. Yeah.
The three musketeers is my half baked analogy for today and it's awesome. A proton has three quarks. The three musketeers has three musketeers. There are six different kinds of quarks with cool foreign sounding names like up, down, top, bottom, strange, and charm. There's a whole bunch of Musketeers out there, whole armies of them, but we'll use the best three for our example, and they have cool foreign sounding names, Athos, Porthos, and Aramis.
So to make a proton, three quarks must come together as a single unit. To not just be three quarks in the same place at the same time, they have to work together as a team. And to make the three musketeers, you can't just have Athos, Porthos, and Armies in a room together, they have to work together as a team. They have to be bonded. They have to be united by a common will and purpose.
And the Quarks can't just be three Quarks. They have to be one for all and all for one. Seriously, folks, this is my analogy. Okay, so far so good? Good, because it's about to get funkier, and I'm gonna stretch this analogy until it breaks.
Don't think of a proton as being made of three quarks. Think of a proton as the name we give to three quarks joined together. When Athos, Porthos, and Armies join together, they acquire a completely new identity, the three musketeers, a singular unit of awesomeness in swashbuckling adventure. And when two up quarks and a down quark join together, they acquire a new identity, a proton, a singular unit of awesomeness in swashbuckling adventure. Wait a minute.
Hold up. A proton is two up quarks and one down quark? Wait. Hold on. Hold on.
How can two up quarks, which is just a name we give like Athos to a kind of quark, an up quark, how can two up quarks hang out in a proton together? Aren't there, you know, rules preventing this sort of thing? I mean, first off, there's electric charge. Two up quarks have the exact same charge. Shouldn't they, you know, repulse each other and not wanna be next to each other?
And second, isn't there this whole poly exclusion principle thing where I can't have two fundamental particles occupying the exact same state, like being right next to each other doing the exact same thing? That's not allowed. I couldn't make two electrons do that. Why can two up quarks do it? And like our three musketeers it's like it's like if our three musketeers were made up of Athos, Porthos, and Athos again.
That's not how the three musketeers works. You need three different musketeers. What's going on? How could I have two of the same musketeer in the same team? And the only way out of this pickle, and we were recognizing that this was a pickle back in the nineteen sixties and seventies.
Once we found out that the proton wasn't fundamental, it was made of smaller bits, and we found out that two of the bits, two of the musketeers are the same guy. The only way out of this pickle is that there has to be something else going on. There has to be something connecting the quarks together. There has to be something, you know, gluing the quarks together even though they would prefer not to be. It has to be some sort of intangible force of camaraderie that, like, keeps the three musketeers together.
In the quarks, you know, what could it be? What could be this intangible force that keeps the quarks together? I mean, they have electric charge, but obviously the electric force isn't gonna work to keep the musketeers together because two of the musketeers have the exact same charge and they'll repulse each other. So there needs to be a new force. And if you have a new force, you need something to tell you how strongly you respond to that force.
Right? If if there's a Force like, okay, Force, feel me. How how much do I feel that Force? How much does the Force feel me? This is what we call in the physics jargon a Charge.
I'll say that again because it's a weird weird weird bit of jargon. A charge, quote unquote charge, is something that tells you how strongly you respond to a force. So with the electromagnetic force, we have electric charge. With the gravitational force, we have gravitational charge, which is something we more commonly call mass. And if there's a new force down there inside the proton keeping our musketeers together, there has to be a new charge associated with the musketeers so that they can feel this new force.
And so, of course, this force needs a name. Right? I mean, what could it be if it's if it's gluing them together? I got an idea. I got an idea.
This force needs a name. Two up quarks shouldn't be able to occupy the exact same state. They shouldn't be able to sit inside of a proton together. This is the Pauli exclusion principle. So they need they need a new identity, right?
We need something to be able to tell apart the two up quarks. They have to be different somehow. Even if they look the same, they have the exact same charge, electric charge, and they have the exact same spin and exact same mass. There has to be some other way of telling apart the up quark that's over here and the up quark that's over there. Well, what what would the three musketeers do?
I mean, it's you you'd have to tell apart the three musketeers because they all have long flowing locks and and very nicely curled beards, and they have the exact same outfits, and they all have swords. So, like, how do you tell the three Musketeers apart? How do you know which one's Athos and which one's Porthos and which one's Hermes? How do you know? Ah, they have hats, don't they?
Yes. The musketeers have hats, and those hats have different colors, maybe. Listen, folks. Just roll with me here. Each musketeer has a hat.
One has a blue one, one has a red one, and one has a green one. This allows you to tell the Musketeers apart. Like, okay. Okay. Athos is wearing the red hat, so that's Athos, and it's very, very different.
And so even if I had two Athoses on my Musketeer team, two Upquarks on my team, Well, one gets the red hat and one gets the blue hat, and so we can tell them apart. So they're not in the exact same quantum state because one has the red the red hat state and the other has the blue hat state. So it's it's legit. And There are three kinds of hats a blue one a red one and a green one that means there are three different charges that's right. There's only one charge, but we've got three quarks hanging out together, which means we need three different hats.
We can't tell them apart just with their electric charge. And if there is only one charge associated with this new force, we still wouldn't be able to pick them out because there's three of them. We need three different charges. We need three different colors of hats. There are three color charges.
And as with any force, there needs to be a way to carry the force from place to place. Right? We've got this color force associated with its color charges that keeps our musketeers identified, labeled, and glued together. But what's the thing doing the gluing? Well, with the electric force and our electric charges, we have things called photons.
We have light. And with the gravitational force and gravitational charges, aka mass, we have this thing called gravity that does the thing of carrying the force from place to place. Okay. So here we go. The color force, remember these hats have different colors, so we're gonna call it the color force, has a color charge associated with it.
And what keeps the Musketeers together? Camaraderie. True. But also glue, I guess. It's called gluons.
Look. It's just it's just called gluons. The color force associated with the color charge is carried by something called a gluon. It's the carrier of the color force. I know.
Okay. I'm not in charge of naming things. Once again, I didn't make this up because even my lame analogies aren't this lame and nonsensical, just the carrier of the color force is called the gluon. For various math reasons, there are eight different gluons. I was about to say feel free to ask for a future episode, but just let's just not worry about why there are eight different gluons.
I mean, really, if you wanna know, I'll ask, but just I'm saying you're not gonna enjoy the answer. Just we're just gonna accept it and move on. There are eight different gluons. There are eight tiny little particles that carry this color force between the quarks. The gluons are the camaraderie between the three musketeers.
Their hats are how we tell them apart, and they exchange camaraderie to make them a team. The quarks have a color charge to help us tell them apart, and what keeps them together are the gluons. But here's something interesting about colors. Right? You got red, green, and blue.
These colors can be traded. It's not permanent. Right? Like, let's go back to our Musketeers because this doesn't make any sense. If you recall, the Musketeers were named Athos, Patreanos, and Aramis.
And, hey, wait a minute. Patreon.com/pmsutter is how you are able to keep this show going. It is your contributions every single month that keep this show going, that pay my bills. This is this is, like, part of my life. This is part of my job, and it's a privilege to communicate science to you in this way.
Go to patreon.com/pmsudder to learn how you can support the show. The names of the three Musketeers are Athos, Porthos, and Aramis, and they were all wearing different colored hats, one red, one blue, one green. Athos was wearing red. Porthos was wearing blue. Aramis was wearing green.
What if they traded hats? Would anything change? I mean, you'd have to update your list of who's wearing what hat, but Athos would still be Athos. Porthos would still be Porthos. Aramis would still be Aramis.
They're just wearing differently colored silly hats, and they're still the three Musketeers. You know, if they if they all just like, hey. Like, hey. Hey, buddy. You know, you wanna trade hats, which I'm presuming is, you know, how they spoke.
Like, if you wanna trade hats and they trade hats, well, they're still the three Musketeers. You'd have to be like, okay. Okay. Okay. Now now Porthos is in the right.
Okay. Okay. I got it. I got it. They'd still be the three Musketeers.
The quarks can trade colors and still be a proton. They still have that camaraderie. They're still glued together. They're just trading colors. The color of the hats or the color assigned to the quark tells us how to distinguish them in any one moment to make sure that the exclusion principle is not violated.
But it's only for that moment. The the the color hats is just a bookkeeping device so that the rules of physics are obeyed, but they don't stay fixed. Imagine the three musketeers just standing around swashbuckling or whatever, and their hats are constantly switching colors. I don't know. They practice sword fighting or something.
I've pretty much given up on this analogy by now, so we're flying blind here, folks. How about I just tell you what a proton really is? It's three quarks constantly exchanging gluons back and forth and forth and back in a crazy frenzy. And every time an exchange happens, every time a gluon bounces from one quark to another, they swap colors all the time. When three quarks are together like this, they're constantly swapping colors, constantly exchanging gluons, and that's what makes a proton.
The quarks themselves do hardly any work in making a proton a proton. In fact, it's the gluons that really make the proton the proton. The attraction between those three quarks is so dang strong, so overpowering that that attraction itself, that energy of being bound together is almost all the mass of a proton. And the gluon itself doesn't have very long range. It can't travel very far.
That's why we don't see it up here in the macroscopic world. It doesn't really affect us. It has a range. It has a finite range, and that range sets the size of the proton. That's as far apart as the quarks can get.
It's like as if the actual Musketeers weren't all that important to make the three Musketeers. Instead, the real magic of the Three Musketeers isn't the individuals, isn't the people, but it's what's between them. It really is the camaraderie after all. One for all and all for one. That's the key.
The camaraderie is what makes the three Musketeers unique. It's the gluons that make a proton unique. And in fact, the camaraderie is so strong that you never see a musketeer alone. They always fight in a team. Always.
You never see one musketeer. It's always the team. This happens with quarks too. We never see a quark alone ever. Why?
Because this color force doesn't get weaker with distance, which is a very, very weird thing to think about. The color force is just as strong far away as it is up close. And so what this means is that if you try ripping apart to course, like, you find you find two of those three musketeers, you reach into your proton, you you grab them, and you start pulling and pulling and pulling and pulling. Because that force doesn't get weaker, you have to keep adding energy. You have to keep pouring you have to keep pouring more sweat.
Oh, your muscles are straining. Oh, you get the robots in to pull these musketeers. This is fantastic visual, by the way. To keep pulling and pulling, you're adding so much energy into the system that eventually new particles get created. That's how much energy you're pouring in.
You end up putting so much energy in that new quarks get created, which instantly bind up with the quarks you're trying to separate. So instead of having two quarks far apart, you have two pairs of quarks or two triplets of quarks far apart. This is something we call quark confinement. The camaraderie between Musketeers is so strong that if you try to pull them apart, new Musketeers appear out of the vacuum to pair up, always giving you a team. So our three Musketeers never separate.
They always fight together. Our three quarks never separate. They always fight together. I will do a quick aside. I don't wanna get into this too much.
You can have pairs of quarks, and you can have triplets of quarks. And sometimes you can have five quarks together. Math gets a little wiggly here. Feel free to ask more about the quark world if you want. But what if you had other protons hanging around, like other groups of three Musketeers?
What happens then? What if you had two sets of three Musketeers? Well, the camaraderie between the Musketeers is so overwhelmingly strong that two groups of Musketeers can hang out together. They're like, oh, yeah. You're a Musketeer too.
Come on close. Even though we can only be three musketeers because that's our definition, you can be closest. You can be your own three musketeers, and you can be next to us, and we're gonna all fight together. What we call the nuclear force or the strong nuclear force is the residual color force that leaks out of protons and neutrons and allows them to bind together. The attraction between quarks in a proton is so strong that camaraderie is so strong that it leaks out of the proton a little bit and allows the protons to bind together despite the fact that protons would not like to hang out together.
That's how strong the color force is. Like I said at the beginning, the color force is exceptionally complex, and I'm leaving out so many details. And I'd be happy to dig into it in a future episode. But this is what's important to remember, colored hats, of course, and the importance of camaraderie. One for all and all for one.
Thank you so much to Katya and via email and Terby via email for asking the questions about the strong nuclear force. And, of course, go to patreon.com/pm. Start to learn how you can keep these shows going. Thanks. Special thanks to my top contributors this month.
Oh, Robert r, Dan m, Evan t, Matthew k, Helgeby, Justin, Matt w, Justin g, Kevin o, Duncan m, Corey d, Kirk b, Barbara k, and Chris c. It is your contributions and everybody else's that keep this show going. Hey. We got a new Astro tour coming up. It is a star party.
An all stars party in Joshua Tree National Park. It's gonna be so much fun. It's me, Fraser Cain, Pamela Gaye, Skylius, and John Michael Godier for a long weekend of stargazing and fun and general merriment. Go to AstroTours.co. That is gonna be such a fun trip.
If you can contribute, if you can't go on an astrotour, that's cool. Why don't you leave a review on iTunes? I'd really appreciate it. You can also buy my book, Your Place in the Universe, which is out in stores now. Yeah.
There's a lot of stuff. Just, you know, go to askaspaceman.com for links. And keep sending me questions, hashtag ask a spaceman or ask aspaceman@gmail.com, and I'll see you next time for more complete knowledge of time and space and camaraderie.