If we are to believe the Mayan calendar, the end of the world is
due on 21 December. But sceptics say climate change or a global
pandemic is far more likely to wipe us all out.  2012
apocalypse: A brief history of end times  The world is set to
end again this Friday, according to thousands of YouTube videos
and fringe internet sites. The idea has gained so much traction
that even Nasa has had to engage the conspiracy theorists.  This
is not the first time the world has been predicted to end, but
the 2012 doomsday theories have become more widespread than most
- supposedly backed by the ancient knowledge of the Mayan
civilisation.  Nasa has published a page rubbishing "common
beliefs" about how the world will end on Dec 21 2012, explaining
"claims behind the end of the world quickly unravel when pinned
down to the 2012 timeline".  The US space agency is so certain
nothing will happen that is has already published a video -
intended for Saturday morning viewing - entitled "Why the world
didn't end yesterday" to