Scientists in South Korea recently claimed to have produced one of the "holy grails" of physics: a superconductor at room temperatures and pressures. Now, researchers around the world are racing to replicate the results. The material, called LK-99, has been presented by its creators as one that can carry electricity in everyday temperatures with absolutely no electrical resistance — sparking a frenzy of excited speculation on social media, quixotic attempts to levitate home-cooked mixtures of lead, and a race by scientists to recreate the material and replicate the original findings. If scientists confirm LK-99 is a room temperature superconductor, it...