GENEVA — The world's largest particle collider successfully completed its first major test by firing a beam of protons all the way around a 17-mile tunnel today in what scientists hope is the next great step to understanding the makeup of the universe.

After a series of trial runs, two white dots flashed on a computer screen at 10:36 a.m. indicating the protons had traveled the full length of the $3.8 billion Large Hadron Collider. "There it is," project leader Lyn Evans said when the beam completed its lap.

Champagne corks popped in labs as far away as Chicago, where contributing scientists watched the proceedings by satellite. Physicists around the world now have much greater power to smash the components of atoms together to see how they are made.

"Well done everybody," said Robert Aymar, director-general of the European Organization for Nuclear Research, to cheers from the scientists in the collider's control room at the Swiss-French border.

The organization began firing the protons — a type of subatomic particle — around the tunnel in stages less than an hour earlier.

Eventually two beams will be fired in opposite directions with the aim of recreating conditions a split second after the big bang, which scientists theorize was the massive explosion that created the universe.