Extreme pressure is not just what you get from your job (but weird things happen there, too). We already knew a few things about pressure, like atmospheric pressure feels pretty normal for us at sea level. At higher altitudes, it get harder for us to breath, and that's why we have to keep airplanes pressurized. Deep sea creatures have evolved to withstand higher pressure that would kill humans. Extreme pressure, the kind that exists at the center of the earth is something we rarely think about.
Under this kind of extreme pressure, solids turn liquid and liquids turn solid, and gas pretty much just disappears. Imagine water turning into a solid. Well, that happens in winter, but at the center of the earth it solidifies under high heat, because of the immense pressure. Adam Cole explains the weird ways extreme pressure warps the way we think about the states of matter when you get outside our normal pressure range. And he makes it both understandable and fascinating. (via Kottke)