Physicists have known since 1911 that electricity can flow without resistance in materials called superconductors. And in 1957, they figured out why: Under specific conditions, including typically very cold temperatures, electrons join together in pairs—something that's normally forbidden due to their mutual repulsion—and as pairs, they can flow freely. Electron pairs are named for Leon Cooper, the physicist who first described them. In addition to explaining classical superconductivity, physicists believe Cooper pairs bring about high-temperature superconductivity, an unconventional variant discovered in the 1980s. It was dubbed "high-temperature" because it occurs at temperatures that, although still very cold, are considerably higher...