Yesterday, Jess took and ran with my analogy between extreme cold and radiation. (Although I think that entry is locked, so not everyone will be able to see it.) At one point she says, "the Second Law of Thermodynamics, the law of increase of entropy that, in a way, defines the direction of time for the universe...".
This refers to the open question regarding why time appears to flow in one direction only, often called the Arrow of Time Problem. One of my old cosmology profs is now out in California, blogging and thinking about the Arrow of Time. Probably not in that order. But Jess' post reminded me of a recent post of his, an Arrow of Time FAQ.