In reality, the activation of the large Hadron Collider won't end the planet. But reality is boring. Wouldn't it be more interesting if it really did usher in our ultimate destruction? OK, maybe not interesting. More like...terrible. So terrible that, uh, actually, we'd better make sure it doesn't mean the complete end of the human race. And what better way to ensure the safety of homo sapiens than to do what the gang at news aggregator site Reddit did, and send an emergency package to Switzerland. Who was it addressed to? The only man who's been through this whole "catastrophic, world-ending physics experiment" thing before. Within? A crowbar, a book and a note.
"Get this to Gordon Freeman. He'll know what to do".
Crowbar, headcrab, and Half-Life strategy guide shipped to CERN [Reddit, thanks Timmo!]