That's the trouble with losing your mind; by the time it's gone, it's too late to get it back.

Energy is liberated matter, matter is energy waiting to happen.

I still enjoy traveling a lot. I mean, it amazes me that I still get excited in hotel rooms just to see what kind of shampoo they've left me.

Why is it, I wondered, that old people are always so self-centered and excitable? But I just smiled benignly and stood back, comforted by the thought that soon they would be dead.

My favourite fellow of the Royal Society is the Reverend Thomas Bayes, an obscure 18th-century Kent clergyman and a brilliant mathematician who devised a complex equation known as the Bayes theorem, which can be used to work out probability distributions. It had no practical application in his lifetime, but today, thanks to computers, is routinely used in the modelling of climate change, astrophysics and stock-market analysis.

Black bears rarely attack. But here's the thing. Sometimes they do. All bears are agile, cunning and immensely strong, and they are always hungry. If they want to kill you and eat you, they can, and pretty much whenever they want. That doesn't happen often, but - and here is the absolutely salient point - once would be enough.

I come Des Moines. Somebody had to.