 Hi, I'm Zor. Welcome to a new Zor education. We continue talking about particles. The previous lectures actually were about main particles, nucleus consisting of protons and neutrons and electrons. They are present in every atom of matter whatever we are dealing with right now. And today we will talk about some other particles and basically their composition. Now, this is much more advanced level of contemporary physics, actually, than whatever we were dealing with previous. And it's still developing part of physics. Nevertheless, I think it's very important just to give you a flavor of what many physicists are actually doing right now and what they're dealing with as far as the theory is concerned. So this lecture will not contain any particular mathematics or anything like that. It's more about just discussion about what exactly is happening right now in particle physics. Okay, now this lecture is part of the course called Physics for Teens. It's presented on Unisor.com. I do suggest you to watch this lecture from the website because every lecture has a textual supplement right next to it which basically is like your textbook. The website contains exams which you can take in a number of times until you feel that you have mastered the contents. The website is totally free. There are no advertisements, so no distraction, no strings attached. Sign-in is not necessary. There is certain functionality of the website related to signing in. That's about supervisory education. If you just do it yourself, you don't have to do it. And what's important is the website contains a course. So it's a set of lectures. There is a menu, there is a sub-menu. The lectures are related logically to each other because I'm using in a subsequent lecture whatever we were talking about in the previous lecture. So it's a course. Whereas if you find this lecture somewhere on YouTube, you'll just have this single lecture without much of the textual explanation or whatever else. Okay, now, so today we will talk about things called quarks. Okay, so let me just start from the beginning. How the progress of the physics which basically is dealing with what is the matter we're dealing with, what is matter. Well, again, very, very briefly, you divide a drop of water, you split the water into two smaller drops and then smaller and smaller until you will reach basically the smallest part of the water which still retains its qualities, chemical qualities and physical qualities. That's the molecule, right? H2O, for instance, for the water. Or if you have, let's say, a copper wire and you cut it and you cut it and smaller and smaller pieces, you will reach a molecule of copper. Fine, okay, now what molecules contain? So that's basically the first factor because you see there are so many different molecules, chemical compositions of atoms and all that. So people actually were thinking that they needed certain theory, certain system to basically understand how all these molecules are constructed. So the next level was atoms. Now we have thousands of different molecules but we have something about 100 different atoms. So that's simplification. I can make an analogy between hieroglyph-based language, like Chinese, for example, and alphabet-based language, something like Latin. In Chinese language you have like 60,000, 70,000, whatever, different glyphs, so to speak, right? And it's kind of difficult to deal with them, difficult to remember them, etc. In Latin you have like 26 different letters and the combination of letters combined basically makes up all the different words. Same thing here. The combination of 100 atoms made thousands and thousands of different compositions which we call molecules. It's kind of a systematization, if you wish, maybe simplification as well in a way. It's easier to deal with 100 atoms in different combinations than with many, many thousands of molecules which we just deal as given, so to speak. Plus it gives you an inner structure of the molecules. So the atomic model was very, very useful. Great. Now we have 100 atoms to deal with and their combinations. What atoms consist of? Well, let's go deeper. And the first thing we found was the main compositions, which is nucleus and electrons. And nucleus in turn contains neutrons and protons. Okay, so we have three main particles from which seems to be all the matter consist of. Well, that's significant simplification. And it's much basically easier to systematize, to construct all the different atoms from all these three components, protons, neutrons and electrons. Well, the problem is it doesn't really encompass everything whatever physicists deal with. There are many, many other particles, not only protons and neutrons and electrons. Well, actually the number is something like about 200, which they have discovered in the course of experiments. So the system needs to be, again, put into some kind of a nice theory. So in as much as we constructed molecule from atoms from main particles, now the main particles and not so main other particles like mesons, muons, whatever, which have been discovered, they have to be somehow put into a nice theory. And the problem is that there was no nice theory, so to speak, at least not now. All right, so let me just give you an example of how people were thinking about the need for this more elementary structure, which basically is supposed to be the inner structure of protons, neutrons and other particles. If you remember, when we were talking about isotopes, that was a previous lecture, we were talking about conversion of nitrogen into the isotope of carbon, carbon-40. Now, that's exactly from the previous lecture. There was a neutron, which was a result of bombardment of upper layers of atmosphere of the cosmic radiation. So they bombarded the atoms in the upper layers of atmosphere, basically broke the atoms in pieces, and neutrons were flying, and protons probably also and electrons. These particles were flying somewhere. Now, the neutron hit nitrogen atom. Neutron has a mass of one and charge, electric charge zero, it's neutral. The nitrogen has mass, atomic mass 14, and atomic number seven. So it has seven protons and seven electrons. Now, as a result, what happens? The neutron kicked off the proton, converting into 14, 6, which is carbon isotope. Now, there is an extra proton, and it also kicked electron as well, because there are only six protons, so the seventh electron also goes away. So that will be proton here, which is mass one, and electron. And then these two combined into atom of hydrogen. So that's how carbon 14 was created. Now, do we understand physically how it happened? Well, yes, I think so. It's like neutron and proton, these are like billiard balls, if you wish. You hit one ball with another, so the first one takes its place, and so if you have a ball, you have another ball hitting this one. Now, this goes away somewhere, and this takes its place, right? So that's what happens with neutron, which kicks off the proton and replaces it inside the atom. So atom is converted from 14, 7 to 14, 6, because proton goes out, neutron is replacing it, so the mass is the same. Instead of proton, you have neutron, both have atomic mass one. But the electric charge is decreasing by one, so it's only six protons now. And that releases another electron, and that's how it goes. It seems to be like billiard balls, basically. So we understand how it happens. Now, what happens after that? How the carbon decays, carbon 14 decays. That's a different thing. It decays in the following way. First of all, one of the neutrons inside this atom of carbon 14 is magically converted into proton and electron. We're not talking about how, magically, okay? Now, what happens then is the following. Since it's converted into proton, the charge is increasing. So as a result of this, this C14, 6, is converting into N14, 7. So we are increasing the charge by one. And electron is released out of the atom. And some other things as well happens, which I don't want to touch. Like neutrino, et cetera, somehow. It's a complicated reaction. But anyway, this is based on this magical conversion of neutron into proton plus electron. But we don't feel that this is kind of understandable. And in as much as understandable the first reaction, well, the neutron just kicks off the proton. We see how it goes physically. We see how the billiard ball actually is hitting another ball. That's understandable. How this reaction happens, it's not really understandable. Magic. People don't like magic. Physicists don't like magic. And they would like to explain it in some way. Okay. And here it is. In some way, people were so much dissatisfied with this and many other things in physics of particles. They wanted to come with some kind of a theory. Okay. What is the theory? Obviously, the theory is that maybe neutron and proton should actually have something inside. And this reaction is also something like a replacement of one piece of inside with another piece. Now, here is just one particular model, which can be thought about. Let's consider we have two different things. X, which has a charge plus one-half. And Y, which has charge of minus one-half. Then X plus X gives you charge one. And maybe that's the proton. Now, X plus Y, these two parts will give you charge zero, right? So, that may be a neutron. Which means that converging neutron into proton means basically a replacement piece of the neutron, which is called Y, with another piece called X. Is it possible? Yes. I mean, in theory, it's a nice theory, whether it's true or not is a different question. But it's a nice theory to satisfy the electric charge of proton and neutron. Well, we don't have only electric charge, which is a characteristic of proton and neutron, which we have to satisfy. For example, we have to satisfy mass. So, sum of X plus X mass should be almost equal to the mass of proton. And sum of these two should be more or less equal to this. Well, again, not exactly because there is some kind of a relationship between energy and mass. And if they are together in an atom, there is a certain amount of energy which holds them together. And there is a famous Einstein's equation that E is equal to mc squared, which we are not talking about right now. But that means that masses are not exactly sum of this is equal to this. But approximately. All right. How about other particles? I mean, if we are talking only about X and Y, two different elementary particles, let's call it this way, from which everything else is comprised, we cannot possibly comprise from only these two things 200 different particles, which we have basically known about, which have their own charge, their own masses, etc., etc. We need something more complex, actually. Well, in 1964, if I'm not mistaken, that was in 1964. And who was that? It was Genman and Zweig, I believe. They have offered something significantly more complex, but it looks like it satisfied different combinations. And we can satisfy the equality between charge and mass and some other properties of different particles with the combination of whatever was actually suggested as a theory. So they have suggested the existence of little elementary particles called quarks, from which other particles actually are constructed. Now, as I was saying, we have something like 200 different particles. Well, the number of quarks is actually, well, it's six, but then there are anti-quarks. So it makes it 12, and then there are some other particles. So altogether, it's significantly less than 200. It's something like a couple of dozens, whatever, from which we can construct other things. And let me just concentrate on quarks, because I would like to talk about only the proton and neutron as the big particles, which basically seem to be constructed from other particles, which we call quarks, which they call quarks. So here is their theory. There are six quarks, and they call it up and down, strain, charm, and strange, and top and bottom. Now, these are just names. So instead of this, call it U, D, C, S, C, and B. Just the first letters. Now, they have certain electric charging. Let's talk about electric charge only. So the up and down have plus two-thirds and minus one-third. Again, plus two-thirds, minus one-third. Plus two-thirds, minus one-third. Now, only these two are used to construct a proton. So the proton can be constructed from U plus U plus D. So two-thirds plus two-thirds is four-thirds, minus one-third is three-thirds, which is plus one. And neutron is U plus D plus D, which is two-thirds, minus one-third and minus third, which is zero. So electric charge is satisfied. Now, mass is also chosen in such a way that some of these three will give you the mass of proton and some of these three will give you a massive neutron. Now, others have also similar characteristics, different masses. The charges I just specified, masses I did not specify, they all have different masses. But again, using the combination of these, you can actually construct other known particles like mesons or whatever else. So that was a very big step forward and it allowed to put lots of different particles into a system which basically explains that these bigger particles like proton and neutron contain these particular elementary particles and some other like mesons have some other combination of these guys. So that was apparently sufficient to satisfy the construction of many particles. Now, in addition to this, something like electron is considered to be an elementary particle, so it does not contain anything inside it. And there are some other like nuance, for example. So physicist came up with something which is called standard model. So the standard model is specifying that there are quarks and there are some other elementary particles like electrons, for instance, and there are some yet other elementary particles which are responsible for the forces. For example, photon, you know, it's kind of sometimes it behaves like a particle, sometimes it behaves like a wave, but in any case, as a particle in this system, it's a particle which is a carrier of electromagnetic force. And there is another one which is gluon, for example, which is a carrier of strong forces which keep proton and neutron together in a nucleus. So the combination of quarks and some other particles may meet up as standard model, which is considered right now as, well, we just accept it, let's put it this way. Now, experimental confirmation, well, that's not so simple. There are certain experiments which hints that the quarks actually were observed. But what's probably more important is that certain properties which result in this particular theory were confirmed. So it's not the existence of quarks themselves, which kind of, well, it looks like it was really kind of observed, but not everywhere, not so consistently. I'm not sure myself quite frankly. But what definitely was observed was that the results of explaining this, using this particular theory, using the standard model, it predicted certain properties of certain particles, and these properties were actually observed really in experiments. That's what's very important. So the standard model seems to satisfy whatever the experiments are observed. What's also interesting is that the standard model, as I was just presented, you just view, the first view onto this standard model, it has a lot of theory behind it and a lot of calculations and the theory is a theory, it must be mathematically expressed. And mathematical expression is extremely complex. Also, what would be interesting is to combine them into some kind of a picture which explains the relationship between. Now there were many kind of tables, like these are quarks, these are leptons or something else, a very simple kind of a view. But this view doesn't really explain the relationship between these particles and how everything else is constructed. There is one very interesting picture which I have found on internet. I put it into, on the website, so if you will, I cannot reproduce it here. It's just completely impossible. But there is something on the website at the end of this lecture, at the end of the textual part of this lecture, I put this picture in. A couple of more words about different properties of quarks and other particles participating in the standard model. Not only charge is a characteristic of a quark, not only mass, we spoke about mass, there are some other characteristics using which we have combining them together, obviously, we construct the corresponding characteristics of more complex particles. So, one of the characteristics of the quark is color. Again, it's not the color which we observed. It's just red, green and blue names which we assign to different quarks and the combination of them is similar to the combination of colors. Like, for example, if you combine red and green, you will have what, yellow if I'm not mistaken, something like this, right? Or red and blue, you will have magenta. Again, combination of different properties. A property is a color, so let's say some particle has a color of magenta. Then, most likely, it's combined from the quark which has color. Again, color includes red and another quark which has a color of blue and that's how you get magenta. So, the combination of these colors gives the color of the particle in as much as the combination of charge gives the charge of the particle. And there is another characteristic, it's called spin, which we are not really talking about. But again, there are many characteristics. Every particle has a certain set of characteristics like charge, mass, color if you wish, spin, whatever else. And there is corresponding characteristics for elementary particles from which we combine them together, we get the particle. So, that's the complexity of the whole thing. And to tell you the truth, the complexity is scaring. Well, no matter what it is, that's how it is accepted at the moment. And I do suggest you to take a look at the picture which I presented at the end of this lecture at Unisor.com. So, you go to the website, you choose the Physics 14 course, you go to Atoms, that's the part of the course bearing. And then among particles, among elementary particles, you will see the first lecture about quarks and that's where you have this picture at the very end. I mean, I think it's just beautiful. I do suggest you to take a look at this picture. It's really very nice. I mean, I can put it on the wall actually. Okay, anyway, so that was an introduction into strange world of particles. It's significantly more complex than whatever I'm talking about, but it's for specialists. I mean, if you will choose as a profession, then you will definitely have to go through this. As just a general knowledge, quarks is a good name, actually. There are other elementary particles, like leptons, for example, but maybe they're kind of less interesting or something like this. I don't know. But I just wanted to know that there is such a word, which is quark, and from the quarks we comprise the bigger particles, like proton and neutron, which are the most important particles. So that's what it is right now. Read the notes for this lecture. Maybe there are some other facts, which I forgot actually to mention. The physics of particles is very, very interesting, but very, very complex. So that's for only those who really like the challenge of this. That's it. Thank you very much, and good luck.