by studying the collisions, scientists have already made a major discovery, the higgs boson. some call it "the god particle". they're now hoping to learn a lot more, because after two years of repairs and upgrades, the collider has begun smashing particles at nearly double the power. the things it's searching for now sound like they're straight out of science fiction. security is tight at the large hadron collider. you need a retina scan to get inside. >> thank you. you have been identified. >> stahl: the entire complex is buried deep underground. >> greg rakness: you can see power, cooling... >> stahl: and this is the heart of it. is this where the collision takes place? >> rakness: the protons come down this pipe, down this orange pipe. >> stahl: american physicist greg rakness showed us one of the four detectors where subatomic particles called protons ram into each other at nearly the speed of light to simulate conditions that are believed to have existed when the universe began. is there a boom? is there noise? >> rakness: there's no noise, but there's a flash of light a