I understand that I usually post something on a roughly once-a-week basis, usually around Thursday. Last week I was busy being ill, so no post. (Coincidentally, I tried to kick-start a nuclear fusion reactor using my forehead heat. It didn’t work.) But I’m using the opportunity to switch to regular, scheduled posting. This week I’ll put up what I had almost finished last week (for Thursday 18th) and something on Christmas Day. And just a heads up – after Christmas I’m going to start a series (anything from 2 to 6 weeks) on the Periodic Table, and how it actually describes the chemical interactions of the entire universe. Hide your chemists.