I would like people to know about the Copernican principle - the idea that our location is not likely to be special. We started out thinking that the Earth was at a very special location, at the centre of the universe. Nicolaus Copernicus finally convinced people that this was not true.

We use the Copernican principle all the time, in evaluating data. The principle also has important implications for the future of the human race. If our location in human history is not special, then there is a 95 per cent chance that we are in the middle 95 per cent of human history - and that the future of the human race will last at least 5,100 more years, but less than 7.8million more years. The Copernican argument suggests that we would be wise to colonise space now, while we have the chance - as a life insurance policy against what ever catastrophes might befall us on Earth.

J Richard Gott III is author of Time Travel in Einstein's Universe: The Physical Possibilities of Travel Through Time (buy this book from Amazon (UK) or Amazon (USA)).