 Greetings and welcome to the Introduction to Astronomy. In this video, we are going to look at the atmospheric retention lab and simulator. So we will look a little bit about how that works. Now remember, when you're answering the questions on the assignment, that some of the things that it asks for may look for the background information here. So there are two simulators here, the gas retention simulator and the gas retention plot. You will need those. But you do need to look at these other materials to find some of your work as well. So let's go ahead and get started here. And what I'm going to really look at is the two simulators. So let's open up the gas retention simulator first and explain a little bit about how that works. And what we will see is that you will come up with all of these different areas. You'll have the chamber, which is where the gas materials are. A distribution plot, which will show how they are distributed relative to velocities. And then some things that you can adjust. You can adjust the properties of the chamber here and the gases that you want to add. So in this case, what you'd want to do is you'll want to add the gases that it asks you to within the simulator. So we'll just pick out a couple here. We can add things like carbon dioxide. We can add things like water. And we can add something like hydrogen. What we'll see is that they have three completely different distributions. That the carbon dioxide is heavier, so it moves slower on average and has a peak back here. The water slightly lighter has its peak here, so it's distributed towards higher velocities. And the hydrogen has a peak way out here someplace because it is even lighter. So those will depend on what the atoms are and they actually have to do with what the molecular weights are. So carbon dioxide is the heaviest and hydrogen is the lightest. And we start them all off with equal representations and they're represented by the different colors within the chamber here. And then you can adjust various things and it may ask you to adjust certain things for each part of the lab. But one of the things we can run is just to run a little example here, is to say what if we were to run with a temperature of 300 kelvin and an escape speed of 1500 meters per second. Now you'll see that that does highlight the escape speed on your distribution plot here, so that's where the escape speed is. So molecules traveling faster than that will be able to escape and molecules traveling slower than that would not be able to escape. So what we'd expect just by looking at this plot is that hydrogen is going to very easily be able to escape from this object. Water, not very well, and carbon dioxide hardly at all. And we can check to see if our predictions are correct by starting the simulation and letting that run. And you can see that hydrogen disappears very quickly and its percentage quickly goes to zero. And here it's just down to a tiny fraction of a percent as all of that has been able to escape. Now after this what you'll see is it's all carbon dioxide and water. But note that carbon dioxide is a little bit heavier and moves a little slower on the average. So if you watch it for a while you will watch the percentage for carbon dioxide increase and the percentage for water decrease as the water that is over here in this tail of the distribution slowly begins to escape. So you can use this as an example of what you'll be looking at as you work with this simulation. And then we want to look also at the other simulator. So the other simulator was the gas retention plot and let's take a look at that. That should start off just like this when you open it up. There are a number of gases that we can look at here. And we can also add in some of the solar system objects. And then we can change a custom object. We can change its properties, its temperature, its radius, and its density. So we can look at how those will affect where it occurs on this object. And that is the red dot that you see on the plot right now. But let's go ahead and add a few of these things. Let's add, for example, we could put in hydrogen, water, and carbon dioxide, the three that we did previously. Now, their speeds will vary depending on the mass as we saw from the previous plot. But they also vary depending on temperature. At a higher temperature they will be moving faster. So carbon dioxide would move at this speed at a very low temperature of 30 Kelvin. But it will be moving at this speed at a much higher temperature of 1,000 Kelvin. And what you look at is these are 10 times the velocities, average velocities. So anything above this would be able to hold on to that gas. So how does this work for things within our solar system? Well, let's clear that. And let's click on adding these objects so we can actually show where the gas giants would occur on here. The terrestrial planets and the icier objects in the solar system. So what it does is to plot them based on their temperature, based on their distance from the sun, and their escape velocity based on their size. So those two tell where it will occur in the plot. So we can then use that to see, and let's look at an example here for Earth. Earth is up above the values for ammonia, in this case, and carbon dioxide. So it would be able to hold on to those in its atmosphere pretty well. Whereas hydrogen it is below the hydrogen line and therefore it would not be able to hold on to hydrogen gas. You can see that the gas giant planets are all above the hydrogen line, that's why they hold on to it. And we can see that things like the moon are way below all of these lines, meaning that the moon would not even be able to hold on to heavier elements like carbon dioxide. And if we go to the heaviest element that we look at there, xenon, and check that, then the moon would barely be able to hold on to xenon, and probably would not even hold on to that over very, very long time periods. So you can use this to kind of figure out what we would look at, what we would be able to see for each of these elements, what each planet, what each object would be able to hold on to. You can also adjust your custom object property. You can change its temperature, which will move it from left to right, and you can change its radius, which will change it, and make it a much larger planet or a much smaller planet. Its radius and density will give it its mass, so that will tell us how much mass there is, and if you make it a lot larger, it's going to be better able to hold on to the other gases. If you make it very small, it's not going to be able to hold on to those. And changing the density will do something similar. A very low density object will not be able to hold on to things, and a very high density object will be better able to hold on to things. So you can use those to adjust the custom object if you need to during your lab exercises. So that concludes this video looking at the Atmospheric Retention Simulator. 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.