Have you heard of the Large Hadron Collider? It is the giant ring under Switzerland that scientists will use to shoot atoms at each other to see what happens when they crash into each other. There was going to be one under Dallas, but it got canceled back in the early 90s.
Anyway, the fear is that by shooting a specific atom at another specific atom, we (as in humanity) could create a small black hole that would eat up the earth. Rainer Plaga, an astrophysicist working for the German Federal Office for Information Security, states that a micro black hole produced at the LHC could set off a chain reaction that “would appear like a major nuclear explosion in the immediate vicinity of the collider.”
While this is not really provable either way, without actually running the LHC tests, most of the scientific community believe that nothing dangerous will happen.
Check out this LHC video stream to see more.