In 2005, at a festive midsummer night’s banquet at Uppsala Castle in Sweden, I chose a seat across the table from two of the world’s leading experts on particle physics: the theorist Frank Wilczek, the previous year’s winner of the Nobel Prize in Physics, and Janet Conrad, a leading experimentalist.

As the northern sun lingered late into the evening, they talked animatedly about the origin of mass. And that conversation led to a bet about an elusive, long-sought, much theorized particle, with me as the bet’s keeper.

Now, with the Large Hadron Collider up and running at a lab outside Geneva, we may be close to settling that bet.

The Standard Model of particle physics, which has passed one test after another, rests on the beautiful idea that the forces of nature arise out of symmetries, which imply certain similarities between particles. But particles actually differ, notably by having different masses. So one of these symmetries must be “broken.”