 brand this initial model, we saw that the temperature of our planet cooled. Here, we see it starting at 10, because that was the last initial temperature that I'd used. And it dropped from 10 to a temperature of minus 18. Now, the question is why? Why did that happen? Let's consider a couple of things here. If we click to page 2 here, we see a couple of other parameters graphed here. One is the energy flux in. So that's just the energy added to our planet in blue. And here's the energy out, the energy flux out. This is the energy leaving the Earth in the form of infrared radiation. And so look what happens initially. Let's take the energy in to begin with. That starts off with a value of about 240, roughly 239. And that doesn't change at all. All throughout this model run, that has the same value of about 240. And the energy out instead, it starts quite high. 358 watts per meter squared. So at the beginning of time, the planet is losing a lot more energy than it's gaining here at this blue line. And that continues until eventually watch that energy flux out. It eventually gets down to be about 240. So at this point in time, those two have exactly the same value, the energy in and the energy out. When the energy in and the energy out have the same value, then our model is in what we call a steady state. And the temperature won't change. One thing just to note here is that each of these curves, the red and the blue, are plotted with their own different scales on the vertical axis. And that's why out in this region here, the two curves appear to be offset, but they actually have the same value here. So it's just a little trick in the vertical axis that's misleading us a little bit there. So the answer to the question of why did the planet cool is simply that initially, given its initial temperature, the energy leaving the planet was much higher than the energy coming into the planet. So the temperature has to drop.