Surviving the 21st Century - for iPod/iPhone

Leading cosmologist Professor Martin Rees once famously said that the human race has only a 50 per cent chance of surviving the 21st century. Current President of the Royal Society, Sir Rees cites natural disasters, nuclear war and global warming among the challenges facing future generations. The Open University's Dr Stephen Serjeant interviewed him ahead of the 2010 Reith Lectures to find out what the future of humanity might be and whether we can really estimate the chance of life in space.