The switch was flipped and the first beam of protons has been fired around the Large Hadron Collider, the biggest particle physics experiment in history. (And we didn't get devoured by a black hole.)
The LHC is a circular particle accelerator with a circumference of 17 miles—or about 300 football fields—buried deep underground at the French-Swiss border outside Geneva. Built at the European Organization for Nuclear Research, known as CERN, the collider will smash protons into each other at nearly the speed of light, hoping to produce data that will let scientists see the conditions of the cosmos a fraction of a second after the big bang. Researchers hope it will also find evidence of the hypothesized (but never observed) Higgs boson, nicknamed the "God particle," which would help physicists explain how particles get their mass and give them a deeper, unified understanding of the universe.
Before long, there'll be proton smashing, but for now, and for the next month or so, scientists will circulate protons in one direction only. Then, they'll circulate them in the opposite direction. And finally, they'll crash the protons into each other, analyzing the collisions.
Follow along with the LHC live Web cast, play the online game Epsilon to see what it's like to be a particle physicist, and be sure to check out the explanatory rap video (above). —Heather Wax