17.3 Subatomic Zoo

All right, our new lesson today is what we call the subatomic zoo. The main zoo is kind of a weird title, but the idea is, you know, if you think of people, probably in the old days, they thought there were only a certain number of animals. And they started discovering more and more animals, so when you go to a zoo, you see hundreds of animals instead of just maybe three or four that you would normally see. The same sort of thing happens with atomic particles. So, we originally thought there were electrons, protons, and neutrons, but now we've also added each of those anti-particles. So, we're already up to six different particles. So, our zoo has now gotten bigger and bigger. Over time, scientists have discovered that higher and higher energies can actually get the particles to change into something different. And because we get smaller and smaller particles, the forces are actually stronger and stronger. Have to start using really high energies to be able to break these things apart. So, what happens is, if we use thirteen point six electron volts, we can get a hydrogen atom to lose an electron. We can remove an electron at a few hundred volts. We can start to look at different energy levels in the atom and get more advanced. Rather than use about ten mega electron volts (that's ten million) to be able to blast an alpha particle at a nucleus and got things to be detected that way. By the time we reach two Giga electron volts (or billions of volts), we start to see some pretty weird things going on. What happens is, once we blast particles with these high energies, we actually get new fundamental particles that were never seen. And they only exist for a split second. So, the concept is a good analogy. It's like throwing a golf ball at a vase to break it. Normally, you'd see okay, it's just gonna break up, we're gonna have all these little small pieces of glass, but in the process of it breaking, we get something like a pencil or some other little object that appears just for a split second. So it seems weird, but that's actually what happens when they do this with particles. So it started with cosmic rays. If you look at this diagram, cosmic ray is basically particles that are emitted from the Sun. So we got things like protons and alpha particles, electrons, things like that, but they're mostly all protons. You can see about 90% of them, and they're coming in at 10 to the 14 mega electron volts. This is billions upon billions and ponds billions of electron volts, so massive amounts of energy. And when they hit our atmosphere, they collide with something like hydrogen or helium or nitrogen or whatever, and those collisions cause these protons to split apart. So you can see in this diagram, they actually split apart into a pion a positive and a negative. Neutral, so you can see that it actually breaks into three different ones for a split second. Then, those pions actually split into a muon, and we get some anti-neutrinos in there. You can see we get some gamma radiation and we get another neutron, and we get some electrons, and so on. So, we start getting some of these weird chemicals that are particles that exist upon these extreme high-energy collisions. And you can see, though, eventually they break down into sort of particles that are more normal. So, we get things like electrons, protons, and anti-neutrinos, and things like that. All of these symbols are starting to be identified now as new fundamental particles. A muon, the picture above, is sort of "find" - they find out it acts like an electron, but it's way more massive. So, you end up getting a way larger mass, about 200 times bigger than an electron. And then you also get an… anti-Muon, which is just like positive ions, are just like the same sort of thing. But what's weird about pions is that we actually get three different types: you have a negative, positive, and neutral, which is kind of weird. We'll look at those later on. But now, with all these extra particles, we actually get over 300 different types. So, to keep track of everything, they kind of broke them into different categories based on things like positive and negative. And also, on things like how big they are and how they spin. So, you can kind of think of these things spinning clockwise or counterclockwise. That sort of breaks it up. And if they spin in whole numbers or half numbers and so on. So, what happens is we get basically scientists and they track... so they call them leptons. And hey drones, as you can see in the leptons, we had electrons, muons, and taus. And their opposites, and hey drones are broken into nissons and baryons. You can see the nissons are things like pions, kaons, and so on - quite big objects. And then the baryons are protons, neutrons, and so on. So you can see there's lots of particles listed in here, but that's still not all of them. There's many, many more if you kind of compare them. You can see in the chart, so an electron, we know it's negative, and you can see that its mass in terms of mega electron volts is 0.5 - 1.1. So, if we compare that to a proton, you can see it's positive and its mass is like 900, so quite a bit larger. So, we can do things like look at something like a pion. You can see it's positive, so it's like a proton but a lot smaller. And we can look at something like a muon. You can see it's negative but way bigger than electrons. So you can see they're just sort of comparisons in terms of... Masses and so on. And we can always convert energy and masses in terms of electron volts, and so on. So, we've got one example. It says, "Let's find the mass of an electron in mega electron volts per C squared." So, if we use the equation energy equals MC squared, we can actually solve for the mass in terms of energy per C squared. All we have to do is figure out what the energy of an electron is. If we take its mass, 9.11, let's actually do it this way: Energy equals MC squared. So, our energy would be 9.11 times 10 to the negative 31. Times 3 to the 8th squared. That gives us an energy. It would have to be in mega electron volts. We get 0.511, which is what the last trick showed us. So, if we get 0.51 mega electron volts, that's like 511 thousand. Roughly half a million mega electron volts. So, if we take that number as our energy, now it's all of it for mass. Without mass would equal e divided by C squared. So, we just take that number, 0.551 mega electron volts, divided by C squared because that's a constant number anyway. That's how we can express mass in terms of different units. But Joule still works, but it's just because they're such small objects. It's usually easier to switch them to this kind of unit to be able to compare them a little bit better. And that's it.