Danish geophysicist

Trained as a mathematician and an actuary, Danish geophysicist Inge Lehmann used painstaking analyses, measurements and observations of shock waves generated by earthquakes to propose in 1936 that the earth had a solid inner core. Throughout her long career, which extended far beyond her official retirement in 1953, Lehmann conducted research in Europe and North America and was active in international scientific organizations including serving as the first president and a founder of the European Seismological Federation.

Lehmann was one of two daughters born to Alfred Georg Ludvig Lehmann, a University of Copenhagen professor of psychology, and Ida Sophie Torsleff. As a child, she attended and graduated from the first coeducational school in Denmark, an institution founded and run by Hanna Adler, the aunt of future Nobel Prize winning physicist Niels Bohr. She began her university education by studying mathematics at the University of Copenhagen from 1907 to 1910. She continued her mathematical studies the following year at Cambridge University in England before returning to Denmark, where she worked as an actuary from 1912 to 1918. She also continued her formal education. In 1920, Lehmann earned her masters degree in mathematics from the University of Copenhagen and later studied mathematics at the University of Hamburg. In 1925, Lehmann began her career in seismology as a member of the Royal Danish Geodetic Institute and helped install the first seismographs at her Copenhagen office. "I was thrilled by the idea that these instruments could help us to explore the interior of the earth, and I began to read about it," she was quoted in a 1982 article published in the Journal of Geological Education. Lehmann later helped establish seismograph stations in Denmark and Greenland.

After further study with seismologists in France, Germany, Belgium, and the Netherlands, and after earning a M.S. degree in geodesy from the University of Copenhagen in 1928, Lehmann was named chief of the Royal Danish Geodetic Institute. In that position, held until her retirement in 1953, Lehmann was Denmark's only seismologist for more than two decades. She was responsible for supervising the Denmark's seismology program, overseeing the operation of the seismograph stations in Denmark and Greenland, and preparing the institute's bulletins.

Despite this heavy workload, Lehmann still found time to explore scientific research. In 1936, she published her most significant finding, the discovery of the earth's inner core, under the simple title of "P." The letter P stood for three types of waves generated by Pacific earthquakes that Lehmann had been carefully observing through the planet for ten years. By studying the shock waves generated by earthquakes, recorded on seismographs as travel-time curves, she theorized that the earth has a smaller solid inner core. Within a few years, work by other scientists, including Harold Jeffreys and Beno Gutenberg, substantiated her findings.

Lehmann continued her research well after her retirement in 1953, exploring the nature of the planet's interior in Denmark, in Canada at the Dominion Observatory in Ottawa and in the United States at the University of California at Berkeley, the California Institute of Technology, and the Lamont Doherty Earth Observatory at Columbia University. She was a named a fellow of both the Royal Society of London and Edinburgh and was named to the Royal Danish Academy of Science and Letters and the Deutsche Geophysikalische Gesellschaft. In 1971, she was awarded the William Bowie Medal of the American Geophysical Union in recognition of her "outstanding contributions to fundamental geophysics and unselfish cooperation in research." She was also awarded honorary doctorates by the University of Copenhagen and Columbia University.

Lehmann remained single throughout her long and productive life. Her interests were not restricted to science. She was concerned with the poor in her native Denmark and the plight of European refugees. Travel in conjunction with her work also afforded her frequent opportunities to pursue two of her hobbies—visiting art galleries throughout Europe and the United States, and the outdoors. Lehmann enjoyed hiking, mountain climbing, and skiing. She died at the age of 105.