Heike Kamerlingh Onnes

Heike Kamerlingh Onnes was a Dutch experimental physicist working at the far edge of what temperature could do. On 21 September 1853 he was born; by the early 1900s he'd pushed cryogenics further than anyone. In 1908 he liquefied helium, dropping it near 1.5 kelvin - a feat no one had managed. Three years later, in 1911, he turned that achievement into a tool: cooling solid mercury in liquid helium, he watched its electrical resistance disappear entirely at 4.2 K. He'd stumbled on superconductivity. The Nobel Prize in Physics came in 1913. He died 21 February 1926, having opened two doors physics is still walking through.