MEYRIN, Switzerland -- One recent Saturday morning, physicists here shot the first beam of subatomic matter into the most powerful particle accelerator ever built. The machine -- a 17-mile circular tunnel that sits 330 feet underground along the Franco-Swiss border -- is designed to smash protons together at nearly the speed of light. It will allow physicists to search for undiscovered particles, extra dimensions of space, dark matter and perhaps even microscopic black holes.

In a nearby auditorium, another groundbreaking...