 Greetings and welcome to astronomy at hack as I over the winter break here I'm recording a few little videos for you for some extra extra special topics just some areas that may have some need of a little bit more explanation and I did this over the summer but I recorded all audio this time I'm going to try recording some videos for you and you'll see me writing up on the screen here yeah I could do it I could print them out and type it out and make it look really pretty but I think the better idea is to bring it a little more what it would be like in the classroom if I were writing things up some of this I would be writing up on a board some would be nicely presented on a screen some would be presented on the on the board and would be written like this so you get to see my sloppy little handwriting there but I think it brings a little more of the classroom type feel to the to the videos and what we're going to talk about today is energy generation in the Sun now how the Sun produces its energy is very important because the Sun is the source of all of essentially the source of all energy on earth so this is where all energy on earth comes from almost not quite we can ignore for example nuclear power nuclear power is not generated from the is not generated directly from the Sun it was generated from elements that were produced in stars that formed and exploded long before the Sun even formed but everything else we use coal and oil and gas are really directly related to stored solar energy from plants and animals that died many millions of years ago and have been buried beneath the surface of the earth and their their organic material as it decayed was formed into the oil and the coal that we use today we also use things like solar energy directly which is directly harnessing the Sun's energy wind energy water energy are all driven by the Sun if the Sun had not been there we wouldn't have any of those sources of energy the only thing there would be nuclear power now the Sun produces energy by what we call nuclear fusion now this is also in contrast to what we use on earth in nuclear power plants actually use on earth we use nuclear fission so that's how we produce nuclear power on earth by fission fusion is bringing things together so bringing atoms together and fission is splitting atoms apart so that is how we go about it on earth we can take uranium and split it into smaller elements and that releases energy which we can then use to power things on the earth nuclear fusion is again another method that can be used that brings atoms together under extremely high temperatures and pressures so one of the difficulties with nuclear fusion for us here on earth is that it requires extremely high temperatures and pressures how hot we're talking at the center of the Sun it is about 15 million degrees and requires temperatures of at least 10 million in order to be hot enough to overcome the repulsion that the atoms feel for each other so because they are similarly charged they don't want to combine together and we'll look at that in a little more detail here coming up on the next page but this is why we're studying solar energy production energy generation how do we produce energy in the Sun it is the source of all energy on earth and we can get a better understanding of it now the method that is used for the producing energy in the Sun is what we call the proton-proton chain and that ends up combined that starts off it's a big chain of things and we're going to look at it here but essentially you start off with two protons so this is a proton and a proton now if you recall each of those protons has a positive charge so that's positively charged and that's positively charged like charges do not want to become close together as they try to go close together if we send them close together at a slow speed the repulsion will kick in and they won't combine they'll just move away from each other the positive charges repel we need them moving at extremely high speed so that they can actually collide and have a chance to stick together so so we need them moving at high speeds tells us that we need extremely high temperatures so what we have is that we move them at high speeds we can actually collide them together and form another particle which is called deuterium so we're not very but we're on the long run we're going to take hydrogen and we're going to form it into helium so we should put that up here let's put that up at the top that's our net result that's what we're looking for is we're going to take four hydrogen atoms and convert them into one helium atom but we're only starting out it has it happens in steps you can't just get four hydrogen atoms and smash them all together at once the two atoms is easy you can smash two things together trying to get three to smash simultaneously is even harder and four is nearly impossible even at the pressures and densities that we have at the center of the sun so let's see what we've gotten here we started with hydrogen this is essentially one hydrogen atom this is a hydrogen atom deuterium is a form of hydrogen that is has one proton and one neutron so this is hydrogen with just one proton this has hydrogen with one proton and one neutron now if you remember call here so as deuterium is positively charged one positive charge so we have a positive charge two positive charges going in and one going out well that's not quite possible we can't lose a charge so we have to have some other particle coming out of here and that's what we call so one particle coming out in addition to the deuterium being formed it sends out a positron so another thing in this case this is a positron which is an anti-electron so it sends out a positron and it also has to say it also sends out another particle called a neutrino so it sends out a neutrino which has no charge and it has sends out a positron which has a positive charge and in fact we're going to do one thing here we're going to change that just to make it stand out a little bit better do that here in a different color we'll do the positron there so it's a positive but that's a positron it's an anti-electron now if you recall anti-matter and matter don't like each other so this this quickly meets a traditional electron so it'll almost immediately this combines with an electron and that electron has a negative charge and when those two combine that gives off energy so the positron will annihilate itself almost immediately with an electron and then send out gamma rays so then we will have that will produce right here we'll send off gamma rays gamma rays are extremely high energy so very very high energy particles and that produces a lot of the energy in the Sun right there the neutrino particle escapes it escapes directly from the center of the Sun and heads off to Earth the other the energy the energy that's produced here takes a long time to get out the neutrinos don't interact with anything once they form and they zip right out to the Earth we're going to talk a little bit about those more on the next page but the first step in the proton-proton chain takes two protons smashes them together to form deuterium which is one proton and one neutron stuck together so you stick these two together one of the charges essentially comes off as a positron or an anti-electron which produces energy in the form of gamma rays and the neutrino now we do this two times we do this a couple of times then we can act or we can do this again we formed it we have deuterium so now our next step in the chain is we're starting with the deuterium atom we're going to do this in steps so we start off with the deuterium here with a positive charge so we have our deuterium atom so here's deuterium and now we're going to combine that with another proton so we're going to take another proton here with a positive charge and we're going to combine those two together and we're going to form something else we're going to form a isotope of helium so we're almost to where we wanted to be we're going to form an isotope of helium that we call helium three this has two positive charges and this is what we call helium three which has two protons and one neutron so essentially all we did here was we took the deuterium and we smashed a proton into it and they all stuck together so we don't need a lot of other things we don't need there's no charge difference we have two charges two positive charges coming in two positive charges coming out so we don't need anything else as we did needed our positron forming in this case so we form helium but this isn't helium this isn't the normal helium the normal helium is helium four so we're going to do that we're going to take two of these helium three nuclei and we're going to smash them together so our final step is to take two of these helium three nuclei which is you recall had two positive charges and we're then going to smash them together and form helium four this is the traditional helium that we're used to again it has two positive charges so it's still two plus and it has two protons and two neutrons so let's see what's happened here we've had four charges go four positive charges going in and only two coming out we still need two more positive charges coming out of here so coming away from this we also have two protons so we're going to have two protons come back out at very high speeds to begin the process again so these will be able to go be able to take these two protons and go back and begin the process once again and we formed helium so the net result is that we have taken four hydrogen atoms and smashed them together we had we had a couple hydrogen tier to form the deuterium the deuterium added another hydrogen to form helium three then the two helium three smashed together to form helium four and then we have our nice stable helium there that's not going to do much of anything else for right now and that's the helium right here that we found so we've taken in a number of steps I know this can be a confusing process I tried to explain it here a little bit differently and hopefully watching as I go through it helps with looking at the material in the textbook when it's just a static picture there give you something a little bit more dynamic to look at and try to understand this a little bit better and then these the protons that come out at the end form go back into the cycle and continue forming again so we'll continue form of more deuterium and continue this process this process on the sun will last 10 billion years this will take 10 billion years for the sun to convert all of its hydrogen into helium so it'll take 10 billion years for all of the hydrogen to be converted to helium then the sun will have to go on through its evolution we'll talk about that at another time but for 10 billion years this process this proton proton chain is able to serve but provide energy to the sun now I want to come back to one more topic that we mentioned and that was this little neutrino here neutrino little neutral one as it's called and that is a very interesting topic and I want to go and talk about a little bit about what we call have called or used to call the neutrino problem what the neutrino problem was was that was I told you the neutrino escapes directly from the center of the Sun so it gets right out from the center of the Sun that is a good test it does not interact with anything so it does not like to interact it just zips through all that all that Sun and just blazes right through it and goes right through and right to the earth or to wherever it happens to be heading in space so it escapes directly it's a look in it's essentially a look into the core so we can see if we can detect some of these neutrinos you know one in a billion one in a trillion even less we can learn something about the core of the Sun that we can't see the other the energy the gamma rays that were produced can take many million can take thousands millions of years to work their way out through the layers of the Sun it can take a very long time for them to work their way out here is a direct look into the core of the Sun and experiments were set up to detect these neutrinos I told you they don't interact well they interact on very rare occasions most of them will blaze through things very very quickly but every once in a while they interact so large tanks of cleaning fluid were set up to detect these neutrinos and they were put well below the surface of the earth and when we detected them we found that we were only detecting we were only detecting a small fraction we only detected one-third of the neutrinos expected wow that's a problem we only detected one-third of what we expected that's a big difference it's not like saying we expected detect 100 we only detected 99 or we detected 101 we were expecting to detect 100 we only detected 33 that's a big difference so that gave us possibilities one of two possibilities and one was maybe we don't understand how the Sun generates it and energy maybe our model of the soul of the Sun is wrong maybe that is the problem or number two maybe we don't understand the neutrino maybe we don't understand the neutrino exactly and maybe there's something with that that we could better understand and it was found out a little bit later that the neutrino actually oscillates and it oscillates between what we call three different flavors so it was three flavors no they don't taste different but three different flavors and our experiments were only detected only set up to detect one of these three so three flavors but the experiment that we used was only detecting one type once we understood that better then that means we would expect to only detect a third of the neutrinos so these are then correct so we were actually did understand it no our understanding of the solar energy generation was not wrong we believe we now do understand how the Sun generates its energy and that our models of the temperatures and pressures of the Sun are correct we what was the problem was we didn't completely understand the neutrino at the time and the neutrino changed between these three different flavors we were only set up to detect one type we couldn't detect the other two so they went through undetected therefore leaving us only detecting one third of the type but I like to use this even though this problem this former problem has been solved and we now do understand it it's still an interesting study in how we learn about objects how science works in terms of trying to understand the different methods what different methods we can use and how we can understand different processes that are occurring so this video again was to talk to you a little bit about the energy generation in the Sun and we talked about that is the source of all the energy on the earth in terms of except for the nuclear power and the main portion of this was trying to give you a basic a little bit sort of an emphasis on the proton proton chain how does the Sun actually produce how does it actually take four hydrogen atoms and smash them together to form one helium atom when we talk about that in general you tend to think take four hydrogen atoms smash them all together and make a helium in reality it actually goes in steps and that's what you're seeing here that's what I was showing you here and then finally just sort of as a study in the scientific method looking at the neutrino problem so how how the neutrinos and the understanding of neutrino that was produced in that very first step of the proton proton chain that's why it was a very big concern we couldn't detect the right number of neutrinos it was telling us we were concerned that this maybe was not going the way we thought it was but it turns out that neutrinos have a pattern of oscillation they can change different types and we were only detecting one of them so there was no neutrino problem the neutrinos were perfectly normal we just didn't understand them completely so I hope this has helped you a little bit with the proton proton chain especially I know that can be a confusing topic and it is an interesting one it's good to try to understand exactly the method by which the Sun does generate its energy so again I'll be recording a few more of these videos on several other different topics to try to help and better understand them as we go through as you go through the course and you can use them to come back to a review so hopefully they've been helpful and until next time I will see you in class