“The dream of seventeenth-century alchemists has been realized by physicists at the Large Hadron Collider (LHC), who have turned lead into gold — albeit for only a fraction of a second and at tremendous cost. The not-so-mysterious transmutation happened at CERN, Europe’s particle-physics laboratory, near Geneva, Switzerland, where the multi-billion-dollar LHC smashes together ions of lead for a portion of each experimental run. Early chemists hoped to turn abundant lead into precious gold. But differences in proton number between the elements (82 for lead and 79 for gold) made that impossible by chemical means. CERN researchers achieved the feat by aiming beams of lead at each other, travelling at close to the speed of light.