The Large Hadron Collider goes live today. Some people have been concerned that it will accidentally destroy the planet (see first reference), if not a good chunk of the universe. Such worries are overstated; there is an infinitesimal chance that it will destroy part of France.
Just in case, though, watch this site. If the message of the day at “Has the Large Hadron Collider destroyed the earth yet?” changes, take the relevant precautions.
HT: Daniel Drucker
Update: xkcd rings in again.