An extraordinary claim by scientists in South Korea has sparked wild hopes of a utopian future where no health condition goes undiagnosed, trains float above their tracks, and – most importantly – your phone's battery life is incredible. LK-99 may sound like little more than a Star Wars extra, but has been tipped as a once-in-a-lifetime physics breakthrough that would land those behind it with a Nobel Prize. That's because it's purported to be a practical superconductor – one that works at room temperature and so could bring the power of a particle accelerator to the masses. Its discovery, detailed…