Being a pessimist is just such a gloomy way of looking at things, so I have to hope for the best - life wouldn't be worth living if we didn't have hope. And I also do think that human beings often do do wonderful, correct, brilliant things. So, on balance, I'd like to be optimistic about the future.

The upshot of all this is that we live in a universe whose age we can't quite compute, surrounded by stars whose distances we don't altogether know, filled with matter we can't identify, operating in conformance with physical laws whose properties we don’t truly understand.

Most big companies don't like you very much, except hotels, airlines and Microsoft, which don't like you at all.

We forget just how painfully dim the world was before electricity. A candle, a good candle, provides barely a hundredth of the illumination of a single 100 watt light bulb.

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.

The number of people on whose cooperative efforts your eventual existence depends has risen to approximately 1,000,000,000,000,000,000, which is several thousand times the total number of people who have ever lived.

Physics is really nothing more than a search for ultimate simplicity, but so far all we have is a kind of elegant messiness.