 Greetings, and welcome to the Introduction to Astronomy. In this video, we are going to discuss the solar system model's labs, which looks at how we have understood the solar system from the geocentric model of ancient times to the heliocentric model. For the actual lab work that you are going to do, we are going to look at the heliocentric model. You will need these sections here, and will not need to worry about looking at those unless you have a desire to go back and look at how things were understood. So what we are going to look at, and you will need a couple of these, you will need some of the background material for some of the earlier questions, and then the planetary configuration simulator is what we will be using for much of the lab. And that's of course what we want to take a look at here. So let's go ahead and let that load, and see what we have here. And what we find is that like with many of the other labs, you will have a variety of different windows within it, and in fact you will have your diagram here showing the orbit. Here you are seeing the strip of the zodiac, so the constellations of the zodiac present, and the location of the sun and the planet under those. Here you can adjust the orbit size, and you can use the presets to select specific planets. You can adjust the speed of the animation. And then you have some of the different configurations that we will look at. Things like opposition and conjunction and quadrature, and here you can have them stopped. Now one interesting thing that you can do is that if you need to pause them, if you are trying to look at times, you can actually pause them for a number of seconds when those configurations occur so you don't miss them. So we can look at some of the examples here, and let's look at an example that if we set this observing from the Earth and say looking at the planet Mars. So now we are at Earth, which is the blue here and then Mars is this one, and then we can then let the controls go, and in fact I will set this to just pause for a couple of seconds as it reaches each configuration. And when we start the animation we will see right now we are at the configuration of opposition. So opposition is when the Earth here has the planet on one side and the sun on the other. So the planet and the sun are opposite to each other in the sky. That will show up here as being 180 degrees apart. Now if we run this forward a little bit we can start the animation and now we are going to pause that there and we are at the position of quadrature. Now quadrature occurs when the planet is 90 degrees away from the sun. So from the Earth there is the sun, from the Earth here is the planet and they are at a 90 degree or a right angle and you will see that 90 degrees here and in this case it will actually tell you that it is 90 degrees east. There is actually an eastern quadrature and previous to this there was a western quadrature depending on what part of the sky the planet is in. So in this case if you were looking from the Earth the planet would be to the east of the sun. Now we can go ahead and let it run forward again and find that we will look for the next configuration and now they are getting closer and closer together and we reach conjunction. Conjunction is when the two objects are in the same direction in the sky. So here is our Earth and the sun is here and so is the planet. So they are in the same direction in the sky. That means the angle between them will be zero degrees and that allows you to then see them. You cannot be able to see the planet it would be in the same direction as the sun so it would be blotted out by the sun's brightness. So we can see how they are moving around over the course of a year. Now this is for a superior planet one further from the Earth. It is slightly different if you look at it will be called an inferior planet or one that is closer such as Mercury and in fact you will see that the terminology is similar except there is a few is similar but there are some things that do not match up. So for example you now have conjunction you can have inferior conjunction or superior conjunction. There is no opposition for an inferior planet. We also do not have quadrature. We have a greatest elongation in the west and in the east. So there are other terminology that apply to an interior planet. And we can see those and a superior conjunction is when the Earth sees the planet on the other side of the sun. Inferior conjunction would be when the planet was here in between the Earth and the sun. So this would be the inferior conjunction location here. So you are going to be able to run those and look at some of these different simulations over the course of the lab exercise. You will also need this counter. Sometimes it will ask you to count to determine the length of the year. Either the sidereal or the synodic here. There are two different ones we will be looking at. And what you will do is run this for example from superior conjunction to superior conjunction again. So as we let the simulation run it will stop at each elongation. An inferior conjunction and then it will stop at the greatest western elongation. And then finally it will get back to superior conjunction again. And if we stop it then we can find as an example here what is the synodic period of Mercury which is 117.6 days. That's how long it takes to get back to the same position relative to the sun. So if you note where they were on the zodiac strip has changed but where they are their configuration relative to the sun is exactly the same. We are back to superior conjunction when the planet is on the opposite side of the sun from the earth. So there will be a number of different exercises. It will have you change the planets and measure the various periods there and answer some questions. So that concludes this video on the solar system models simulator and the planetary configuration simulator. We'll be back again next time to look at another one of these simulations. So until then have a great day everyone and I will see you in class.