Letter: Put your money on the asteroid

Sir: "I'm no statistician," writes Charles Wroe (letter, 26 February). Nor, it would seem, a very careful reader of Oliver Morton's excellent and thought-provoking article ("So who cares if the sky is falling?", 25 February).

The reason there have been a hundred or so National Lottery jackpot-winners is that the draw has taken place once or twice a week for the past couple of years. Alas, usually only one or two people win each time.

In contrast, a smallish asteroid hits the Earth only about once in 500,000 years, but would kill about a quarter of the global population in one go. Taking the long-term average, the odds of this happening to any one of us in our lifetime are indeed greater than those of winning the lottery.

Dr DAVID A ROTHERY

Department of Earth Sciences

The Open University

Milton Keynes, Buckinghamshire