I think, you know, for instance, a man called Milankovic in around 1940 made a convincing argument, and I think now it's correct, that orbital variations created a change in insulation, incoming sunlight, in the Arctic in summer. And that controlled the ice ages. And the thinking was pretty simple. He was saying that, you know, every winter is cold. Every winter has snow. But what the temperature or the insulation or the sunlight in the summer is determines whether that snow melts or not before the next cycle. And if you're at a point where it doesn't melt, you build a glacier. Takes thousands of years, but eventually it's big.