The lights of other days

The concept of first lights can be thought of as the most recent iteration in an extended interplay between the idea that the world around us can be explained in terms of processes that are still going on and amenable to examination (“uniformitarianism”) and the idea that many important things happened only long ago when the universe was very different (“catastrophism”). As is usually the case in such matters, there is a fair amount of truth on each side, but, just at the moment, the catastrophists are slightly in the lead.