Inge Lehmann

Inge Lehmann never married nor had any children.

She breathed her last on February 21, 1993 at the age of 104. She left all her possessions to the Danish Academy.

Posthumously, to mark the contribution made by Lehmann in the field of seismology, the American Geophysical Union established the Inge Lehmann Medal in 1997. The medal is awarded for outstanding contributions to the understanding of the structure, composition, and dynamics of the Earth’s mantle and core, every year.

Inge Lehmann was born on May 13, 1888 in Osterbro, Copenhangen, to Alfred Georg Ludvik Lehmann and Ida Sophie Tørsleff. Her father was an experimental psychologist by profession.

Lehmann was educated at pedagogically progressive high school under Hanna Adler. The school was one-of-its-kind for despite being a co-educational, no differentiation based on sex was made. Girls and boys enjoyed equal status. Adler cast an important influence on the mind of young Lehmann, as did her father.

Completing her preliminary education, in 1907, Lehmann gained admission at the University of Copenhagen, studying mathematics. However, her frail health partially interrupted her studies. In 1910, she gained admission at the Newnham College, at the University of Cambridge continuing her study of mathematics.

In 1911, Lehmann returned from Cambridge. Her frail health did not allow her to study any further, as she suffered from fatigue and lassitude. She temporarily took up work in an actuary’s office where she developed good computational skills.

In 1918, Lehmann resumed her studies at the Copenhagen University. After two years of study, she finally completed candidatus magisterii degree in physical science and mathematics

In the autumn of 1922, Lehmann studied mathematics with Professor Wilhelm Blaschke, in Hamburg, Germany only to return to Denmark a year later. She accepted the position of assistant J.F. Steffensen, the professor of actuarial science, at Copenhagen University.

Year 1925 marked the turning point in Lehmann’s career. She was appointed as an assistant to Niels Erik Nørlund, the newly appointed director of Gradmaalingen, a Danish geodetic institution. Nørlund planned to set up seismological observatories in Denmark and Greenland and wanted Lehmann to run the stations and interpret and publish the observations.

In her new profile as Nørlund’s assistant, Lehmann supervised the establishment of one seismological station in Copenhagen. She also helped prepare instruments for two other stations in Greenland. Though Lehmann’s job description did not include research work, she was free to indulge in it.

In 1927, Lehmann visited the seismological stations across Europe. Same year, she attended an International Union of Geodesy and Geophysics in Prague. The conference was attended by the who’s who of seismology, including Gutenberg and Harold Jeffreys. From the conference, Lehmann comprehended that to construct a time travel curve, an assessment of the accuracy of different stations and a consistent interpretation of seismograms was decisive.

In 1928, based on her studies, she gained the magister scientiarum degree (equivalent to an MA) in geodesy. Same year, she was appointed state geodesist head of the department of seismology at the Geodetical Institute of Denmark.

Lehmann’s most important contribution to the world of science has been in the field of seismology. Through her extensive research and investigation, she brought forth the fact that the inner core of the Earth is solid, rather than the presumed belief of its being molten. She further researched and determined that the solid inner core has a liquid outer core that in turn explained the transits of seismic waves. Using mathematical concepts, she analysed the way energy was released by Earthquakes and travelled through the Earth. Other than being discoverer of the Earth’s core, Lehmann also figured out a low velocity layer between 190 and 250 km below the Earth’s surface. This seismic discontinuity was later renamed Lehmann discontinuity.