Physicists returned to their future on Friday. About 10 p.m. outside Geneva, scientists at CERN, the European Center for Nuclear Research, succeeded in sending beams of protons clockwise around the 17-mile underground magnetic racetrack known as the Large Hadron Collider, the world’s biggest and most expensive physics experiment.

For physicists, the event was a milestone on the way back from disaster and the resumption of a 15-year, $9 billion quest to investigate laws and forces that prevailed when the universe was less than a trillionth of a second old.

The collider was designed to accelerate protons to energies of seven trillion electron volts apiece and smash them together in tiny fireballs in an effort to replicate and study the conditions of the Big Bang.

The first time protons circled the collider, on Sept. 10, 2008, the event was celebrated with Champagne and midnight pajama parties around the world. But the festivities were cut short a few days later when an electrical connection between a pair of the collider’s giant superconducting electromagnets vaporized.