Another fun pick-up from the 'new arrivals' shelf at the library. This is the 2nd book in a row to point out that there are significant areas of our lives in which we (or rather scientists) still know very little about. Why do we sleep? What actually goes on in our brains while we're asleep? Can we be held responsible for actions taken (even including killing someone) while asleep? Some really interesting stuff in here, though still not many answers. Not that it's the author's fault; it's just that we don't know the answers yet!

One of the most interesting things I picked up was in the first couple of chapters. Before we had electric lights that kept us up long after the sun went down, most people just went to sleep shortly after dark. But instead of sleeping through 10+ hours of darkness, we went through what was called a "first sleep" for 3-4 hours, wake up for an hour or two, and then have a "second sleep". Often times people were there most productive, or came up with the best ideas "in between first and second sleep."  One experiment with a group of people who did this (sleep when it got dark out) revealed similar behavior. For a few days, they had super nights of sleep, catching up on all the sleep debt that we all accumulate. But after a week or two, almost all of them started waking up in the middle of the night for this period between sleeps. It's fascinating, though the author admits it's not likely we'll ever get back to that sort of a schedule as a norm.