Call it First Bang.

The Large Hadron Collider, the world’s biggest and most expensive science experiment, produced its first collisions on Monday, said scientists at CERN, the European Organization for Nuclear Research, outside Geneva.

Seemingly making up for lost time after years of disasters and delays, the collisions came only three days after engineers had begun shooting the subatomic particles known as protons around their 17-mile underground racetrack. The physicists announced that they had succeeded in making the beams collide, producing what they called “candidate collision events” in the giant particle detectors in the collider.

The collider has been built over 15 years at a cost of $9 billion to accelerate protons to energies of seven trillion electron volts apiece and then slam them together in an attempt to recreate forces and particles that reigned during the first moments of the Big Bang. But for much of that time, the only things that have gone bang in the collider were magnets and other components, most notably in September 2008 after the first time protons circled the collider.

When the beams began circulating again on Friday, CERN officials said they expected the first collisions to happen in early December.