Inge Lehmann ForMemRS (13 May 1888 – 21 February 1993) was a Danish seismologist and geophysicist. In 1936, she discovered that the Earth has a solid inner core[2][3] inside a molten outer core. Before that, seismologists believed Earth's core to be a single molten sphere, being unable, however, to explain careful measurements of seismic waves from earthquakes, which were inconsistent with this idea. Lehmann analysed the seismic wave measurements and concluded that Earth must have a solid inner core and a molten outer core to produce seismic waves that matched the measurements. Other seismologists tested and then accepted Lehmann's explanation. Lehmann was also one of the longest-lived scientists, having lived for over 104 years.[1][4][5][6]

Inge Lehmann
Lehmann in 1932
Born(1888-05-13)13 May 1888
Copenhagen, Denmark
Died21 February 1993(1993-02-21) (aged 104)
Copenhagen, Denmark[1]
Resting placeHørsholm Cemetery
55°52′14.06″N 12°30′16.01″E / 55.8705722°N 12.5044472°E / 55.8705722; 12.5044472
Alma materUniversity of Copenhagen, University of Cambridge
AwardsWilliam Bowie Medal (1971)
Scientific career
FieldsSeismology, geophysics
InstitutionsGeodetical Institute of Denmark

Early life and education Edit

Inge Lehmann was born and grew up in Østerbro, a part of Copenhagen. She was very shy as a child, a behavior that continued throughout her life. Her mother, Ida Sophie Tørsleff, was a housewife; her father was experimental psychologist Alfred Georg Ludvik Lehmann (1858–1921).

She received her school education at Fællesskolen, a pedagogically progressive high school that treated girls and boys equally, enrolling them in the same curriculum and extracurricular activities. This school was led by Hanna Adler, Niels Bohr's aunt.[7][8] According to Lehmann, her father and Adler were the most significant influences on her intellectual development.

At age 18, she achieved a first rank mark in the entrance exam for Copenhagen University. In 1907, she started her studies in mathematics, chemistry and physics at the University of Copenhagen and University of Cambridge. These studies were interrupted by poor health. She continued her studies of mathematics in Cambridge from 1910 to 1911 at Newnham College. In 1911, she returned from Cambridge feeling exhausted from the work and put her studies aside for a while. She developed good computational skills in an actuary office she worked in for a few years until she resumed studies at Copenhagen University in 1918. She completed the candidata magisterii degree in physical science and mathematics in two years, graduating in 1920. When she returned to Denmark in 1923, she accepted a position at Copenhagen University as an assistant to J.F. Steffensen, the professor of actuarial science. [9]

Lehmann had a younger sister, Harriet, who became a movie writer and who had family and children in contrast to Lehmann, who lived by herself all her adult life.[10][11][12]

Career Edit

A modern understanding of the Lehmann discontinuity: velocity of seismic S-waves in the Earth near the surface in three tectonic provinces: TNA = Tectonic North America SNA = Shield North America and ATL = North Atlantic.[13]

In 1925 Lehmann's seismology career began as she became an assistant to the geodesist Niels Erik Nørlund. She was paired with three other assistants who had never so much as seen a seismograph before. She began the task of setting up seismological observatories in Denmark and Greenland. In the meantime, she studied seismology on her own. She went abroad for three months to study seismology with leading experts in the field such as Beno Gutenberg, who had determined the distance to the core-mantle boundary within 15 km of the modern accepted value.

Based on her studies in seismology, in 1928 she earned the magister scientiarum degree (equivalent to an MA) in geodesy and accepted a position as state geodesist and head of the department of seismology at the Geodetical Institute of Denmark led by Nørlund.[14] Lehmann looked into improving the co-ordination and analysis of measurements from Europe's seismographic observatories, as well as many other scientific endeavours.[15][3] These improvements lay at the heart of her later discoveries.

In a paper titled P' (1936),[16][17] Lehmann was the first to interpret P wave arrivals—which inexplicably appeared in the P wave shadow of the Earth's core—as reflections from an inner core, for example from the strong 1929 Murchison earthquake.[18] Other leading seismologists of the time, such as Beno Gutenberg, Charles Richter, and Harold Jeffreys, adopted this interpretation within two or three years, but it took until 1971 for the interpretation to be shown correct by computer calculations.[19] Lehmann was significantly hampered in her work and maintaining international contacts during the German occupation of Denmark in World War II. She served as the Chair of the Danish Geophysical Society in 1940 and 1944 respectively.

In 1952, Lehmann was considered for a professorship in geophysics at Copenhagen University, but was not appointed. In 1953, she retired from her position at the Geodetic Institute. She moved to the US for several years and collaborated with Maurice Ewing and Frank Press on investigations of Earth's crust and upper mantle. During this work, she discovered another seismic discontinuity, which is a step-change increase in the speed of seismic waves at depths between 190 and 250 km. This discontinuity was named the Lehmann discontinuity after her. Francis Birch noted that the "Lehmann discontinuity was discovered through exacting scrutiny of seismic records by a master of a black art for which no amount of computerization is likely to be a complete substitute."[19]

Memorial to Lehmann in Copenhagen (by Elisabeth Toubro)

Awards, honours, and legacy Edit

Lehmann received many honours for her outstanding scientific achievements, among them the Gordon Wood Award (1960), the Emil Wiechert Medal (1964), the Gold Medal of the Danish Royal Society of Science and Letters (1965), the Tagea Brandt Rejselegat (1938 and 1967), her election as a Fellow of the Royal Society in 1969,[20] the William Bowie Medal (1971, as the first woman), and the Medal of the Seismological Society of America in 1977. She was awarded honorary doctorates from Columbia University in 1964 and from the University of Copenhagen in 1968, as well as numerous honorific memberships.

The asteroid 5632 Ingelehmann was named in her honour and in 2015 (which was the 100th anniversary of women's suffrage in Denmark) Lehmann got, in recognition of her great struggle against the male-dominated research community that existed in Denmark in the mid-20th century, a new beetle species named after her: Globicornis (Hadrotoma) ingelehmannae sp. n., Jiří Háva & Anders Leth Damgaard, 2015.[21]

Because of her contribution to geological science, in 1997, the American Geophysical Union established the annual Inge Lehmann Medal to honour "outstanding contributions to the understanding of the structure, composition, and dynamics of the Earth's mantle and core."[15][22][23]

Christiane Rousseau received the 2014 George Pólya Award of the Mathematical Association of America for her article "How Inge Lehmann Discovered the Inner Core of the Earth".[24]

In 2015, on the 127th anniversary of her birth, Google dedicated its worldwide Google Doodle to her.[25][26][27]

A new memorial dedicated to Lehmann was installed on Frue Plads in Copenhagen in 2017. The monument is designed by Elisabeth Toubro.[28]

Key publications Edit

  • Lehmann, Inge (1936). "P'". Publications du Bureau Central Séismologique International. A14 (3): 87–115.

See also Edit

References Edit

  1. ^ a b "Lehmann, Inge". Complete Dictionary of Scientific Biography. Detroit, MI: Charles Scribner's Sons. 2008. Retrieved 15 October 2013.
  2. ^ Buffett, Bruce (1 November 2013). "Earth's enigmatic inner core". Physics Today. 66 (11): 37–41. Bibcode:2013PhT....66k..37B. doi:10.1063/PT.3.2178. ISSN 0031-9228.
  3. ^ a b "Inge Lehmann: Discoverer of the Earth's Inner Core". American Museum of Natural History.
  4. ^ "Inge Lehmann – Biography, Facts and Pictures". Famous Scientists. The Art of Genius. Retrieved 2 July 2017.
  5. ^ "Lehmann; Inge (1888–1993)". The Royal Society: Past Fellows. Archived from the original on 21 January 2019. Retrieved 24 September 2013.
  6. ^ Bolt, Bruce A. (January 1994). "Inge Lehmann". Physics Today. 47 (1): 61. Bibcode:1994PhT....47a..61B. doi:10.1063/1.2808386.
  7. ^ "WiP: Herstory: Spotlight Scientist: Inge Lehmann". Purdue University. Archived from the original on 26 March 2016. Retrieved 15 October 2013.
  8. ^ Knopoff, Leon. "Lehmann, Inge". UCLA. Archived from the original on 18 May 2015. Retrieved 15 October 2013.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
  9. ^ Stomberg, Joseph (13 May 2015). "How Inge Lehmann used earthquakes to discover the Earth's inner core". Vox. Retrieved 8 October 2021.
  10. ^ "Lehmann had a younger sister, Harriet, who became an actress and who had family and children in contrast to Lehmann, who lived by herself all her life; from google (Inge Lehmann married) result 2".
  11. ^ "She sacrificed marriage and family for her career, since women at that time could almost never have both; from google (Inge Lehmann married) result 1".
  12. ^ "She had not married and had no children; from google (Inge Lehmann married) result 3".
  13. ^ Figure patterned after Don L Anderson (2007). New Theory of the Earth (2nd ed.). Cambridge University Press. p. 102, Figure 8.6. ISBN 978-0-521-84959-3.; Original figure attributed to Grand and Helmberger (1984)
  14. ^ Maiken, Lolck (2008). ""Lehmann, Inge." Complete Dictionary of Scientific Biography". Gale Virtual Reference Library. Vol. 22: Gale. pp. 232–236. Retrieved 22 May 2015.{{cite web}}: CS1 maint: location (link)[permanent dead link]
  15. ^ a b "Inge Lehmann". Famous Scientists.
  16. ^ Lehmann, I. (1936): P', Publications du Bureau Central Seismologique International, Série A, Travaux Scientifique, 14, 87–115.
  17. ^ Kölbl-Ebert, Martina (1 December 2001). "Inge Lehmann's paper: " P'"(1936)". Episodes Journal of International Geoscience. 24 (4): 262–267. doi:10.18814/epiiugs/2001/v24i4/007.
  18. ^ Bolt, Bruce A. (1987). "50 years of studies on the inner core". EOS. 68 (6): 73, 80–81. Bibcode:1987EOSTr..68Q..73B. doi:10.1029/EO068i006p00073-01.
  19. ^ a b Dahlmann, Jan (23 January 2005). "Inge Lehmann og Jordens kerne" [Inge Lehmann and the core of the Earth]. Ingeniøren (in Danish). Retrieved 14 May 2015.
  20. ^ "Fellowship of the Royal Society". Royal Society. Archived from the original on 15 October 2015. Retrieved 13 May 2015.
  21. ^ "A New Species of Globicornis (Hadrotoma) (Coleoptera, Dermestidae, Megatominae) From Baltic Amber". Archived from the original on 3 February 2016. Retrieved 2 July 2017.
  22. ^ "Inge Lehmann Medal". American Geophysical Union.
  23. ^ "Inge Lehmann".
  24. ^ How Inge Lehmann Discovered the Inner Core of the Earth, Mathematical Association of America, retrieved 2014-12-17.
  25. ^ Gander, Kashmira (12 May 2015). "Inge Lehmann's 127th Birthday: Pioneering seismologist celebrated by Google Doodle". The Independent. Retrieved 12 May 2015.
  26. ^ Kevin McSpadden (13 May 2015). "New Google Doodle Honors Pioneering Seismologist Inge Lehmann". Time. Retrieved 13 May 2015.
  27. ^ "Inge Lehmann's 127th Birthday".
  28. ^ "Skulptur på Frue Plads i København er et minidrys feministisk retfærdighed". Politiken (in Danish). 8 July 2017. Retrieved 8 July 2017.

Further reading Edit

External links Edit