 Greetings and welcome to the Introduction to Astronomy. In this video we are going to go through the simulator used for the Lunar Phases Lab and demo a little bit about how that works. Now what you need to do is to go through and there is a lab worksheet that will be provided and the first few questions actually require you to go through the background material so make sure that you are not ignoring this. You do need to go through that to answer some of those questions. If you try to just jump into the three simulators you will have some difficulty. So go ahead and follow through the instructions it will tell you when you need to access each of the specific three different simulators that you will use in this lab. So what I want to take a look at here is a little bit about each of those simulators and how they work. So the first one we use is the moon bisector demo and that will load here and then what we'll see is there are a number of controls to use and really what you're using for this one is the set of controls up here for the phase determination. You'll want to click on each of those in turn and for example it will show you where the sun direction is and it will label that. It will then show the sun bisector and then it will show the shadows meaning that you can now see what part of the moon is illuminated by the sun. This half pointing towards the sun is illuminated and this half pointing away is not. However that does not just tell us the phase we also need to look at what the phase determination is and we can click on those four buttons. We can show the earth and moon line between them. We can show the bisectors and then we can determine the moon's phase and we do that by looking at the part of the moon. What we can see from the earth is the part of the moon that is facing us and looking at the sun bisector this only this quarter section of the moon that is illuminated is actually facing the earth. So you can do that for what you're asked to in the lab exercise to kind of emphasize that. Now one of the main things that you'll use in this as we'll go back to the area here we'll go to the lunar phase simulator which you will use for a lot of the lab. This has a number of different windows. First of all it has the moon phase window over here which will show you the phase and you can use the drop down menu to select different phases. It will show you the horizon diagram which you can turn around. It will give you a few options if it will let you know if you need to do those and then the time controls and then the main window really showing what you see here. So what you're going to do on these various sections it will go give you through the instructions but let's look at an example of the first quarter phase. So we can then take this to first quarter and it will adjust everything here for you. And you can then look at what the time is. So where our observer is happens to be located. Their location on the earth tells you what the time is. So with this case with the sun being as high in the sky as it can be and we can see that also here on the horizon diagram that this time would be local noon or 12 p.m. At that point we can see where the different phases of the moon would be located. In this case we've gone to first quarter. The moon has moved from the new phase one quarter of the way around and we see that it is 50% illuminated. And we also see then that where it will be in the sky. So at noon the sun is high in the sky but where is the moon? And we can see it very far off here on the eastern horizon. So depending on the location you can then look at where the moon will be relative to the sun. And for the first quarter moon it will just be rising around noon time. Now you can do a number of different activities with this. It will ask you to rearrange some of the coordinates and then look at what you find for the phases of the moon. You can also run the animation straight through if you like and start the animation. It will allow you to go through and you can watch how the moon phases work over time. And you can look at the horizon diagram here. You can even turn that and watch the sun and the moon in their relative positioning to each other. Here as we approach full moon it will be exactly opposite each other in the sky. The sun setting is the full moon rises and now the moon will be catching up to the sun again. And we will approach head back towards the new phase. And we're not going to let that run the whole way. You can play with that as you like to take a look at it. But you can watch it in different areas so that you can see as the demo runs. You can see the actual orbital view that you would see here. Where is the moon located in its orbit? We can see the phase as it's now approaching third quarter. And you can see the relative positions compared to the horizon. So let's go ahead and stop that and look at the last simulator that we want to look at. And that would be, as we go back here. That would be the moon phase and horizon diagram simulator. So as we load that, we will see that this is a little bit simpler. And this has a couple of different things. And it really comes down to the fact that if you know two of three things, you can figure out the third. If you know the phase of the moon, the time, and the location in the sky. And one of the things that you'll look at is be given two of these three. And then ask to determine what the third one is. So as the example, as this is set up right now, we are at first quarter phase. So if we know it is first quarter phase, and we know the time of day is 3 PM, you can set to those two things. And then find out where is the moon in the sky. And you can use the diagram then to find that again. Like the others, you can turn this around. To find that when you have first quarter moon at 3 PM, the moon is going to be in the southeast. So it has already risen off the horizon in the east and is a little bit further up in the sky. We can look at one more example of that. If we want to change the phase of the moon, so if we want to look at a slightly different phase, what if the phase were a, let's say a, and let's say it were a waning crescent moon. So now we've changed the waning crescent, the phase. We have not changed the time, it is still 3 PM. Where is it going to be located? Well, the waning crescent moon will always be at 3 PM, will be located on the western horizon just setting. So if you know any two of these, the phase, the time, and the location, you can then figure out the third of them. So that concludes this video on how to work through the phases, the phases of the moon simulators that we will be using for one of our labs. And we'll be back again next time for another topic in astronomy. So until then, have a great day everyone, and I will see you in class.