Walther Meissner (1882-1974)
Fritz Walther Meissner was born on December 16, 1882, in Berlin, Germany. He studied mechanical engineering at the Technische Hochschule Berlin-Charlottenburg from 1901 to 1904, followed by two years of mathematics and physics at the University of Berlin. In 1907, Meissner received his doctorate in physics, having completed his thesis under the direction of Max Planck, the well-known originator of quantum theory. Meissner accepted a position at the Physikalisch-Technische Reichsanstalt, a scientific research institute founded by Hermann von Helmholtz, in 1887.
Meissner made a significant contribution toward the understanding of superconductors in 1933. Superconductivity, which is a phenomenon characterized by the disappearance of electrical resistivity in various materials cooled below a critical temperature, had been discovered by Dutch physicist Heike Kamerlingh Onnes in 1911. Since that time, however, little had been learned about the properties of superconductors until Meissner and Robert Ochsenfeld began their work with superconducting materials and magnetism. In the course of their investigations, the pair discovered that superconductors expel relatively weak magnetic fields from their interior and are strongly diamagnetic. This phenomenon, commonly known as the Meissner effect or the Meissner-Ochsenfeld effect, is related to the generation of screening currents along the surface of the superconductor that are able to cancel out the applied magnetic field. (For a short explanation and video, click here.)
Notably, the Meissner effect is not always observed. When an external magnetic field is very strong, a material may be unable to enter the superconducting state and, consequently, no Meissner effect occurs. Also, the phenomenon may transpire only partially, with the interior magnetic field being reduced but not completely expelled, when an applied field is of intermediate strength. The particular superconducting material in question, its shape, size, and the presence of impurities are all factors than can affect the extent of the Meissner effect. Visually the Meissner effect can be demonstrated by placing a magnet over a superconducting material, causing the magnet to levitate.
Following this discovery, Meissner was offered and accepted the technical physics chair at the Munich Institute of Technology in 1934. In the 1940s, he was elected president of the Bavarian Academy of Sciences and founded the Academy’s Commission for Low Temperature Research. By early 1952, Meissner officially retired, but he continued carrying out research for many years. In 1974, Meissner died in Munich. On the hundred year anniversary of his birth, in 1982, the Institute for Low Temperature Research located in that city was renamed in his honor.