Quote from: Wikipedia
Misinterpretation of the Mesoamerican Long Count calendar is the basis for a New Age belief that a cataclysm will take place on December 21, 2012. December 21, 2012 is simply the first day of the 14th b'ak'tun.
Besides that point, the end of a calendar has no meaning in of itself. If my calender ends on Dec 31, 2012 I don't assume the world ends, I go out to buy a new calendar. The choice of Mayan's calendar is pretty arbitrary as a super intelligent people with knowledge of the future, anyway.
Sorry to shatter the dreams of apocalypse nuts, but you guys still owe for y2k.
About the LHC; I'm pretty sure they don't collide photons but electrons or alpha particles.
Some people assumed the LHC would bring about the end of the world and decided to sue CERN. CERN created an investigative body to look into the possibility of the two predicted senarios: the creation of a black hole, and the strange matter catastrophe. They found the possiblities highly unlikely.
The strange matter catastrophe I think is the more interesting one, if I remember correctly it's strange quarks arranging in such a way to produce "strange matter", which procedes to interact with the nearby matter to cause a cascade of transformation of everything on Earth into "strange matter."
Anyway, it's a good thing the eggheads are dealing with the particle smashing otherwise there would be more reason to worry.