Hello and welcome to the fourth episode of Ask a Physist. And again we have a very interesting question to answer this time from the sensei, who seems to be quite interested in antimatter. He asks, does antimatter exist? How does it contain it? And what is it used for? These are great questions of course. However, I think here it will be more appropriate for me to start by actually explaining what antimatter is. And to do that, I think it's best to start by explaining what matter actually is. As you probably know every solid liquid and gas around you consists of atoms, which are basically the building blocks of matter. At the center of the atoms, there is a nucleus made out of two different particles called protons and neutrons. This nucleus is surrounded by shells of smaller particles known as electrons. So essentially all matter around us consists solely of protons, neutrons and electrons. The interesting thing about electrons and protons though is that they both have charge. Protons have positive charge and electrons have negative charge. Well, what you need to know about charge is that opposite charges attract each other, whereas the same charges propel each other. If you have ever rubbed a balloon against your hair and noticed your hair rising up or even made it stick to a wall, well that's because of charge. As you do the rubbing, protons and electrons will be distributed unevenly over the balloon and your hair. The balloon will end up being either positively or negatively charged and you will be able to make it stick to anything that has an opposite charge on it. So now to antimatter. Antimatter is essentially the same as normal matter except that consists of anti protons, anti neutrons and anti electrons. Anti electrons are also known as positrons. The difference between these particles and their corresponding antiparticles is that their charge is reversed. Antiprones have negative charge and anti electrons or positrons have positive charge. Another property that's reversed for antiparticles is their spin, but that's something I'm going to get into another time. Anyways what's really interesting here is what happens when particles and antiparticles collide. But for instance a particle like an electron and its corresponding antiparticle, a positron, come in contact, the tube will annihilate, leaving by nothing but gamma radiation or a gamma photon. In other words the mass of the tube will be converted into pure energy. This is exactly what Albert Einstein's formula E equals MC squared is all about. You see the energy released in such a collision will be equal to the mass of the two particles times the speed of light squared. And that's quite a lot actually. So that's what anti matter is. Does it exist? Yes. But there's not much of it around. We sometimes get positrons naturally from radioactive decay or from cosmic rays from outer space. Also we can create an artificially in the laboratory by sending high energy electromagnetic radiation like gamma rays on an atomic nucleus resulting in a particle and its corresponding antiparticle. This process is called pair production. Basically it's a reverse of the annihilation process of particles and antiparticles. The reason why there's such a low amount of antimatter in this universe compared to normal matter as opposed to equal amounts of both is still a mystery to science. So how do we contain antiparticles? Well, obviously we can't just put antimatter in mere boxes. Since upon contact with ordinary matter they would annihilate. And well, give out lots of radiation. However, there is a solution to this. Charge particles are influenced by magnetic and electric fields in such a way that we can control their motion. Hence we can set up a combination of magnetic and electric fields in such a way that it would trap a charge particle. For instance an antiparticle. In such a way that it does not have to come in contact with any ordinary matter. Devices creating such fields are known as penning traps. However of course these traps only work for charge particles. So in other words they wouldn't work for neutrons or antinutrons. Only for protons and protons, atoms and positons. Now for the last question, what is antimatter used for? Well at the moment I'd have to say not much. There is use of positron emitting radioactive materials in medicine, namely positron emission tomography or PET. This is a method to produce 3D images of a process happening in your body by injecting the earth with a positron source, letting the positrons annihilate with electrons in your body and looking with a resulting radiation strikes. More interestingly in the future we may be using antimatter as a fuel. As I've explained when matter and antimatter come in contact the mass can be transformed into pure energy. If you look at this in comparison, 1kg of antimatter colliding with 1kg of normal matter would release an amount of energy equivalent to that of more than 40 million tons of TNT. So that's quite a lot. If we were able to use antimatter as fuel for the propulsion systems of spaceships we could reduce the size and weight of the fuel required to a fraction of its current extent. If we got spaceships of this sort of work it would be a big step closer to interplanetary travel. The only problem here of course is that there is not much antimatter around and that it takes a lot of energy to produce it in the first place. But well I'm sure we get to eventually. Well I'm afraid that's pretty much all I can say about antimatter for now. I hope the sensei is pleased. At this point I'd also like to point out, well some of you may be wondering why your questions haven't been brought up in episode yet. Although they've been posted long before this one. Well there is a good reason for that. As you see some of the stuff I'm bringing up in the episodes to come will be based on stuff I've been covering already. Like for instance gravity. I'm going to explain that again. Or charge. As I explained today I'm afraid I'm going to bring that up again too. So I'm really just trying to get these questions in an order that makes sense. Also since pretty much all episodes so far have been based on an astrophysics topic. I thought it would be interesting to get some particle physics in here finally. So don't worry if your question hasn't been answered yet. I hope I will get to answer them all eventually. So that's all for this episode of Ask a Physiist. I hope you enjoyed it. As always please feel free to leave a comment and to post a question yourself. And I'll see you next time. Take care.