In the best case the Large Hadron Colliders' ALICE experiment successfully creates quark-gluon plasma, a substance theorized to have existed just milliseconds after the Big Bang. By generating temperatures more than 100,000 times hotter than the sun, scientists hope to watch as this particle goo cools and expands into the particles that we know. That could help scientists answer why protons and neutrons weigh 100 times more than the quarks they're made of. And why women cry at the most random times imaginable.
The the worst case, scientists inadvertently make a micro black hole, and the earth is quickly erased from existence. Just kidding. Scientists at CERN and elsewhere have ruled out the possibility that the LHC will create any kind of doomsday scenario. The black holes that the LHC could theoretically create don't even have enough energy to light up a light bulb. On the other hand, the U.K.'s Astronomer Royal put the odds of destroying the world at 1 in 50 million. I plan on going to work tomorrow. If not, I hope I see you in Paradise.
If you are as geekish as me, check this out, its interesting: