What if the aliens decide they don't like us?

To paraphrase one contributor to the BBC Focus magazine forum this week: if the Universe is 14 billion years old and the Earth just 4.5 billion, we newcomers to the Universe might have grasped the concept of civilisation rather late in the day. Upon meeting us, our technologically superior, interstellar pen pals might deem us quaint cosmic toddlers — or expendable cosmic savages.

If we are to extend that terrestrial hand of courtesy, its fingers should be crossed, in the hope that any passing aliens simply fancy adding a few unreconstructed earthlings to their Bebo accounts.