this is the Sun I assume you guys have seen the Sun before what we're gonna be mainly talking about today is the structure of the Sun all the different parts of the Sun and we're gonna start with how the Sun makes light ok does anybody happen to know what process the Sun uses to make light the Sun is not on fire ok so does anybody know how the Sun makes light this is kind of a I'm not sure if anybody will know this one but let's see if anybody does let's check this out see somebody's given an attempt right now we're getting some attempts yeah uh-huh ok that is correct that is correct the Sun makes light through a process called fusion ok fusion sometimes called nuclear fusion so this is somewhat related to the way that we make power in a nuclear power plant but it's not exactly the same thing because what we do in a nuclear power plant is something called fission ok fission the Sun uses fusion and we in a nuclear power plant use fission you may have heard that nuclear power plants split atoms so fission is when you take a very large atom and you split it into smaller atoms so if you had one big one fission is to do this that's fission so can anybody figure out what fusion is does he might know what fusion is hint it's related to fission so see if you can figure it out if fission is splitting a larger atom into two smaller ones yeah Fusion is taking two smaller atoms and sticking them together okay so fusion and fission are basically opposites of each other actually I have a slide right here so this is fission you take this big one and split it into two that's what we do in nuclear power plants the Sun is taking small atoms and sticking them together through fusion to make bigger atoms okay so that's what the Sun is doing now if you read the history of the solar system which hit you probably should post it up on canvas we know that in order for fusion to happen like the the gas in this room right now is not fusing if it was I would be dead and that's because the air in this room is not in the right conditions for fusion to naturally happen again if you read that file you know that in order for fusion to happen naturally just on its own then you need the density to be extremely high of whatever gas you're dealing with and you need the temperature to be extremely high so there's only one part of the Sun that has a high enough temperature and a high enough density to bring these few these atoms together to make the fusion happen can anybody does anybody know what part of the Sun would you expect this fusion to be happening if it has to be the hottest part of the Sun and the densest part of the Sun that's correct it's the core so what we're talking about the place where you can think of the power plant of the Sun being is deep down in the center of the Sun where you can't actually see there's too much gas in the way for us to actually see the fusion happening okay so we'll talk a little bit later about how we know that the fusion is actually happening but for now we're talking about the core of the Sun the core uses fusion and if you're gonna be using fusion you're have to fuse small elements together can anybody figure out what element the Sun is probably fusing together it needs to be very small and there needs to be a whole ton of it that's correct that's correct the Sun is fusing hydrogen okay so the sun's process that generates light is hydrogen fusion okay there's a whole ton of hydrogen in the Sun the Sun 75 percent hydrogen give or take and and hydrogen's really small so that's what's gonna fuse so what I'm gonna do is I'm gonna bring up the doc cam that the school let me borrow and what we're going to do is I'm going to show you the details of this hydrogen fusion and why it makes light okay so check this out let me just change my window here here we go okay now this right here I'm gonna go ahead and tell you this is gonna be the most technical thing that that we're probably going to talk about the entire semester it's gonna look really complicated but after we draw it all out I'm gonna simplify it down into a much more compact simple way of thinking about it so let's let's work our way up to it now there are actually a lot of different ways to fuse hydrogen but the Sun uses one particular process most of the time and that particular type of hydrogen fusion is called the proton-proton chain proton-proton chain now why don't let me zoom in a little bit now why do we call it the proton-proton chain well remember the temperature is extremely extremely extremely hot in the center of the Sun and one thing that we haven't talked about yet that tends to happen when you're in these kind of you know million degrees situations remember temperature is a measure of the jiggles in a substance so the hotter something is the more it jiggles and essentially what happens is if you get some atoms in a place that's as hot as the center of the Sun the electrons that are attached are so fast moving they get so much energy that they essentially pop off of the atoms so that means that all of the atoms I'm about to tell you about in this picture in this process have lost all of their electrons okay and technically there's a name for atoms that are missing electrons and it starts with an i it's very short word does anybody know what this word is do is it me know what we call atoms that are that are missing their electrons here ions ions yes these are called ions and so technically this type of gas that's in the center of the Sun here is called a plasma because it's made out of ionic atoms these atoms are missing their electrons here okay so let's take keep that in mind if we had it high and had a hydrogen atom and it lost all of its electrons what's the only thing left in that hydrogen atom what's the only thing left in the nucleus of that that hydrogen atom if the electrons are gone yeah a single proton somebody said neutrons to regular run-of-the-mill hydrogen doesn't actually have any neutrons you can have neutrons in hydrogen but the type of hydrogen that we normally think of the abundant common kind is just proton just one single proton so that means a single proton by itself is a hydrogen atom it's just an ion because it's missing its electron so every single solitary proton by itself is also a hydrogen atom okay so that's why it's called the proton-proton chain because we're sticking together hydrogen atoms we're sticking together protons okay so in this particular type of fusion the Sun starts with four atoms of hydrogen so I'm going to draw that right here there we go that's our four atoms of hydrogen and I'm going to put a plus on them because that's our protons right so that proton is a hydrogen atom that protons a hydrogen atom that protons a hydrogen atom and that protons a hydrogen atom just so that we remember that they're hydrogen atoms I'm also gonna draw a little letter H capital H next to them that's the symbol for hydrogen okay now we're going to fuse them which means because it's so hot and so dense they're going to come together and stick okay they're gonna come together and stick they don't want too big but because it's so hot and so dense they accidentally run into each other and the strong force is able to stick them together okay so let's bring them together like this okay that's them fusing okay and so if we stuck together four protons we're gonna have four little balls stuck together right here let me zoom in a little bit there we go so we stuck together these four protons and so we have a new atom right here made of four balls now don't overthink this how many of these little balls should have pluses on them how many don't draw anything yet but how many of these balls should have pluses on them should don't overthink it and my document cam froze up so give me one second I need to reboot it while you guys are answering that question there we go yeah we would expect all four to have pluses on them because we had four balls with pluses we had four protons coming together so now it seems like we would just have four protons stuck together but it turns out when you fuse atoms sometimes funny business happens and in the proton-proton chain we get a little bit of that funny business it turns out when you stick them together two of those protons lose their charge okay two of those protons lose their charge that's not something that just happens like in this room right here or in your room wherever you're at but it does happen in fusion sometimes so that means if those protons lost their charge what did those protons turn into because of that fusion the two protons that lost their charge turned into two some things what did they turn into yes that's correct that's correct they turned into neutrons okay they turned into neutrons again that's not something that nor Emily happens so that that's switching there as part of this fusion causes some other particles to pop out of this atom okay some other particles are gonna pop out of this atom so we made a new atom but we also here we go we're going to get two photons that's two beams like two little particles of light right there I'm drawing two photons pop out and these are gonna be extremely high-energy photons what is the highest energy kind of light what kind of photons are we making right here the absolute highest energy kind of light that's correct that's correct these are gamma-ray photons okay so these are gamma-ray photons so I'm gonna put the word gamma here gamma gamma and the symbol for gamma rays is this looks like a fish swimming down like this that's just the Greek letter gamma so that just stands for gamma ray so when we make this new atom it releases some high-energy light okay but that's not done it also produces two other weird kinds of particles so here we go popping out also are two neutrinos and I'll explain what these are in a second this is not the same thing as neutrons it's a totally different thing two neutrinos pop out and at the same time I'm gonna put these down here here we go put two little pluses on these two positrons okay like I said this is uh this is a nasty-looking diagram right here but it's almost done okay so let's check this out again we fuse four atoms of hydrogen together and we make a new atom and at the same time all of this stuff pops out of that atom because of the monkey business that was happening during that fusion okay we know what gamma rays are let's talk about what these other things are neutrinos neutrinos are really really really really weird like let's say that I was walking along next to you like yeah like a couple of feet away from you because I'm not uh I'm not obeying the social distance guidelines oh no I got too close to you with my baseball and you're like what what what's going on dude and then I just in response to you I just take my baseball and I chuck it as hard as I can right at your face if I just look just huh baseball right at your face too fast for you to react what's gonna happen what's gonna happen in this situation what's gonna happen when that baseball gets to your face it's gonna hurt yes it's gonna hurt it's gonna bounce off your face it's gonna bounce right off your face come off and yeah you're probably pissed off at me I I probably would have gotten fired okay in this at this case what would the in-class demonstration have been it would have been fun we missed out this would have been this would have been something yeah anyway that's what would happen now let's say instead of that regular old baseball what if I showed up with a a ball made of neutrinos and did that exact same thing I just came up to you violated your personal space and chucked that ball of neutrinos right at your face right at your face if that had happened when the ball and neutrinos hit your face it would go into your head and come out the back of your head it would go right through your face and come out the back okay so would that be good for your face if a ball of neutrinos went right in the front and came right out the back seems like it would be really really bad but it turns out it would actually be totally fine in fact nothing would happen to you in that case you would actually be better off being hit by the neutrino ball going straight through your face and coming out the back because it turns out the main property of neutrinos is that they are and I'm going to put this right here on the diagram they are weakly interacting weakly interacting and that means that they do not like to interact with things they and in hitting you that's an interaction so all of these neutrinos will just go through your face like it's not even there they don't want to interact with your face and if they don't interact with your face then they're not gonna hurt your face either so I'm not saying that it would make a tunnel through your head it would just go in like a ghost and come out like the out of the back like a ghost like if I was let's say it was like driving a neutrino car along and I crashed into a wall the car would continue to go through the wall and I would slam into the wall and then fall down like a cartoon if the neutrinos are just very very very very strange okay think of them as ghost particles they go through everything without really affecting them okay and yeah it's all I really had to say about neutrinos positrons positrons what's something we can say about these positrons what's something you could tell about these positrons probably what's at least one property of them somebody's asking me to explain Dark Matter I I will explain Dark Matter to you in the chat after all this is done give me a second it's it's kind of a long discussion don't worry about Dark Matter right now okay yeah the positrons are positive what are they though it's a little bit weird positrons are antielectrons these guys they are antimatter electrons and if any of you guys ever heard of antimatter probably positrons are antielectrons antimatter is a real thing and it's not super common you know like here on earth but the Sun is constantly making antimatter all the time okay now you probably have heard of antimatter in sci-fi movies do people you people usually like to mess around with antimatter in sci-fi movies is antimatter a good thing to mess around with no now why why is antimatter a bad thing to mess around with why is it so dangerous well it's because of what it is okay antimatter is just like matter but with all of its properties the opposite okay so for every kind of thing we have every type of matter so protons neutrons electrons even neutrinos you can make an antimatter version of it with all of the properties reversed so a positron is like an electron with all of its properties flipped does anybody know what kind of charge a regular electron has what kind of charge is a regular electron has negative yes so a positron is just like an electron but for example it's its charge is positive because a regular electron has a negative charge now someone's asking all of the properties including mass what's the opposite of mass so technically when I said all properties I mean all properties that have an opposite so mass would be something these guys actually had the same there's no opposite of mass so the matter and antimatter would have the same mass but something like charge has two opposite versions so any property that has two opposite versions like that the antimatter will have the opposite of what the matter has and if it's something that doesn't have two opposites then they just share the same okay now here's the thing though remember we said and we're almost done with this diagram we're getting to the end we said that all of the electrons over here because it would sorry all of the atoms over here because it was so hot their electrons fell off but those electrons are not gone there's still all over the center of the Sun okay and so what's going to happen is immediately as soon as these this antimatter gets formed as soon as these positrons form they're gonna run into in the environment a couple of electrons that are just flying by so a couple of electrons that were just trying to mind their own business and I'm going to put a little minus on those will fly by and what happens is that these positrons and these electrons are attracted to each other because opposites attract so the antimatter electrons will be attracted to the regular electrons and does anybody know in a sci-fi movie what happens when matter and antimatter come together what happens in sci-fi movies would matter in antimatter come together yeah it's usually an explosion and it turns out that this is one of the few times where sci-fi movies are basically right the reason you don't want to mess around with antimatter is that when matter and matter comes together with its own type of antimatter they destroy each other they completely destroy each other in a process called annihilation so it's not just explosion its annihilation these positrons and these electrons will annihilate each other okay and when they do they're essentially turning each other into extremely high-energy light so all of the matter and antimatter is destroyed and what's left in their place is photons of very high energy what kind of energy is that gonna be what kind of photons are we going to make if they're the highest energy photons gamma-rays again and here's the thing let's see if we can figure this out how many gamma-ray photons are we going to make every particle that gets destroyed produces a gamma-ray photon so these two positrons destroyed these two electrons so how many gamma rays are we going to get how many gamma ray photons for that's correct so these two positrons and these two electrons each one of them becomes unde a more eight so I'm gonna pop out here on the other side whoa I'll just draw one of them but say for gamma okay and that's the whole process okay