"Can we be sure that a black hole created at the LHC wouldn’t expand and swallow the earth? I think the honest answer to this question is yes. The black holes that would be produced at the LHC must also be produced by the hundreds every day due to energetic cosmic rays bombarding our earth. When cosmic rays smash into particles of earth material, it’s the same type of collision that happens in the LHC. So the very fact that we exist here on earth to talk about these things tells us that even if black holes are produced, pretty much everything is very safe. Either black holes are not produced at all, or they decay very, very quickly due to Hawking radiation or an equivalent mechanism." - Robert Seidman from Bookmarklet