The call comes in from the control room. Stanford University's particle accelerator-one of the largest machines on Earth-has been shut down because of a failed magnet. This is bad news for the scientists I have traveled across the continent to see: Their experiment was designed to run 24 hours a day and the disruption will cost them reams of precious data. But me, I'm thrilled. Normally, the innards of the radiation-spewing accelerator are off-limits. But idle, it poses no danger.