Today is the birthday of physicist Walther Meissner, who was born in Berlin in 1882. He received his PhD in 1907 after studying under Max Planck, the founder of quantum theory. Meissner is best known for his work with superconductors, materials that have zero electrical resistance at low temperatures. In 1933 Meissner and colleague Robert Ochsenfeld discovered that superconductors expel magnetic fields from their interior. Physicists often demonstrate this phenomenon, known as the Meissner effect, by getting a magnet to levitate over a superconducting material. Crucially, the Meissner effect is used today to confirm that materials are indeed superconductors; it is considered more reliable than resistance measurements. In 1946 Meissner became the director of the Bavarian Academy of Sciences and founded a Commission for Low Temperature Physics. In 1982 the Central Institute for Low Temperature Research in Garching, Germany, was renamed the Walther Meissner Institute for Low Temperature Research. (Photo credit: AIP Emilio Segrè Visual Archives, Physics Today Collection)
