by Una Hearne. On a rerun of the sublime TV show QI (don't you just love Stephen Fry and Alan Davies?) they were talking about the 'half life of facts'. That is, how half of the 'facts' that medical students learn in college will be considered to be untrue in 10 or 12 years time. And how facts given on QI itself are just as subject to contrary proof over time. We like to think that scientific facts are in fact, facts - and to some extent they are - but they are constantly changing ...