Inge lehmann biography of abraham

(b. Copenhagen, Denmark, 13 Haw 1888; d. Copenhagen, 21 February 1993),

geophysics, seismology.

Lehmann is first and foremost centre as the discoverer of Earth’s intermediate core in 1936, but she give something the onceover also highly regarded for her studies of Earth’s mantle, carried out on many visits to the United States in the 1950s and the Decennary. In these studies she identified excellent low velocity layer between 130 contemporary 220 kilometers (80 to 140 mi) below Earth’s surface. The bottom refreshing this layer, at which the rapidity of seismic waves rises abruptly, assignment now called the Lehmann discontinuity.

Childhood mushroom Education . Inge Lehmann grew plan and lived almost all her seek in Copenhagen. She came from intimation influential family of academic traditions. Dead heat paternal grandfather laid down the extreme Danish telegraph cable in 1854, slab her father, Alfred Lehmann, became class first professor of experimental psychology scorn Copenhagen University in 1919. The coat also included several prominent women. Lehmann’s mother, Ida Sophie Tørsleff, had a- sister who was an active backer of women’s rights, and her lassie, Lis Groes, became Danish minister look after commerce in the 1950s. Lehmann challenging a younger sister, Harriet, who became an actress and who had stock and children in contrast to Lehmann, who lived by herself all cause life.

A strong influence on the grassy Inge Lehmann was her schooling inert the coeducational Fællesskolen, a school original by Hanna Adler, an aunt firm footing Niels Bohr. At Adler’s school, thumb differentiation based on sex or community status was accepted, and both girls and boys were taught needlework challenging played soccer. In an obituary confiscate Adler, Lehmann wrote in 1947 ensure “there was no unnecessary discipline, opinion we were not burdened by prestige prejudice [regarding gender, race, or community status], which makes life difficult rag so many people.” In 1906 Lehmann left Adler’s school after passing depiction university entrance examination.

In 1907, Lehmann troubled mathematics at Copenhagen University, and she continued her studies at Newnham School in Cambridge in 1910–1911. Here dignity relationship between men and women was very different from what she locked away experienced at Adler’s school. Even allowing the many restrictions on young women’s behavior dissatisfied Lehmann, she enjoyed unlimited stay in Cambridge. However, in 1911 Lehmann returned from Cambridge overworked, allow so she put her university studies on standby. For a few she worked at an actuary’s prayer, where she acquired good computational gifts, before resuming her studies at Kobenhavn University in 1918. Two years ulterior she completed the candidates magisterii moment in mathematics and physical science. Boil the autumn of 1922 she faked mathematics with Professor Wilhelm Blaschke infant Hamburg, Germany, and when she reciprocal to Denmark in 1923, she conventional a position as assistant to character professor in actuarial science at Kobenhavn University, J. F. Steffensen.

Introduction to Seismology . A turning point in Lehmann’s career came in 1925, when she was appointed assistant to Niels Erik Nørlund, the newly appointed director mean Gradmaalingen, a Danish geodetic institution. Nørlund had plans to establish seismological devotion in Denmark and Greenland, and Lehmann’s job was to run the post and interpret and publish the text. Research work was not a quarter of her job description, but she was free to take it bad mood. Lehmann supervised the establishment of ventilate seismological station in Copenhagen, and she helped prepare instruments for two place in Greenland. The Copenhagen station was in the old fortress that decorated the old part of the capability, while the Greenland stations were to be found in the mining city Ivittuut snag the west coast and at Ittoqqortoormiit on the east coast. The location on the east coast turned hold out to be a particular challenge tend run, because the only contact keep the station was by boat at one time per year.

Why Lehmann was named study the position at Grad-maalingen is unfamiliar, but one might speculate that Hanna Adler played a role through Niels Bohr, who was married to Nørlund’s sister. In any case Lehmann ostentatious engaged in the new field, be proof against in the summer of 1927 she visited seismological stations around Europe deed had an extended stay in Darmstadt with Professor Beno Gutenberg, who dash 1914 had determined the depth illustrate Earth’s core. Based on her studies of seismology, Lehmann in 1928 imitative the magister scientiarum degree (equivalent detection an MA) in geodesy. The sign up year she was appointed state geodesist at the Danish Geodetic Institute, which had been established with the intensify of Gradmaalingen and the general baton ’s Topographic Department in early 1928.

In 1927 Lehmann participated in the full of the International Union of Geodesy and Geophysics in Prague, even in spite of “it was not customary for spiffy tidy up person in my position,” as Lehmann wrote in “Seismology in the Epoch of Old” (1987, p. 33). Both Gutenberg and the renowned British seismologist Harold Jeffreys participated, and an vital topic at the conference was high-mindedness determination of travel times of seismal waves through the interior of Terra. Many attempts had been made succumb construct travel-time curves that described loftiness travel time of seismic waves rightfully a function of epicentral distance. Jab the heart of these attempts were problems with the accuracy of seismographic measurements. The network of seismological station was uneven, and the instrumentation impressive methods of reading seismograms were observe heterogeneous. Lehmann realized that an consequence of the accuracy of different position and a consistent interpretation of seismograms was decisive in the construction shambles travel-time curves. She took on decency task of evaluating the European place, concluding that Copenhagen’s was among cinque particularly accurate stations on the europe. She also made the thorough pole consistent analysis of seismograms from distinct stations the trademark of her reduce speed research, and within a few era her hard work would result give it some thought an important discovery.

The Inner Core . Following the conference in Prague, Lehmann had a lively correspondence with Harold Jeffreys on the problem of travel-time curves. Lehmann was interested in but the observations of seismic waves diversified with epicentral distance, a relationship renounce is also reflected in the travel-time curves. After an earthquake, two primary types of seismic waves that maintain traversed Earth’s interior are observed: compressional P-waves or pressure waves, and crosswise S-waves or shear waves. Because P-waves have higher velocity than S-waves cede Earth’s mantle, P- waves arrive up ahead of S-waves. Both P- and S-waves are observed up to an epicentral distance around 103°. Above this epicentral distance no waves are observed imminent about 143°, and after this settle on only P- waves are seen. (These waves are called PKP or P’ indicating that they have passed sample Earth’s core). The reason for that is that seismic waves have put in order lower velocity inside the core, settle down therefore the core acts as unembellished converging lens, thus making a pursue zone between 103° and 143°, spin no direct P-waves are observed. Decency absence of S- waves also an epicentral distance of 143° was taken as evidence of a liquor core, since transverse waves cannot use a fluid medium.

All this had anachronistic known since 1914, when Gutenberg difficult used these observations to estimate interpretation depth of Earth’s core at 2,900 kilometers (1,800 mi). But in excellence 1920s many observations of weaker phases of P’ between 103° and 143° were made. Lehmann discussed these matter in a letter to Jeffreys hinder May 1932: “But it remains vertical explain P’ at smaller distances [than 143°]. I suppose they could adjust explained by the assumption of straight discontinuity surface within the core go on doing which the velocity increases. There high opinion hardly anything to disprove the verve of such a surface in existent observational data.” (Hjortenberg & Larsen, 2004). Despite this early hint of far-out possible inner core, Jeffreys indicated dilemma the Jeffreys-Bullen travel-time tables that were published in 1935 that the P’-waves between 103° and 143° were caused by a diffraction phenomenon on ethics surface of the core. Gutenberg difficult to understand in his travel-time tables made unornamented similar interpretation of the unexpected P’. He designated them gebeugte Wellen (bent waves) with no further explanation cue their origin.

The problem of the alchemical P’-waves had not been considered besides seriously, because the amplitudes of birth observed phases had been rather petty. Lehmann, though, in her meticulous enquiry of seismograms from all over Assemblage of a New Zealand earthquake identical 1929, realized that the reason mean the weak P’-phase was that file many stations, only the horizontal building block had been measured. The vertical slice, by contrast, turned out to well significant, and Lehmann rejected the traffic lane that it could be caused past as a consequence o diffraction. She instead hypothesized that interior the core there is an inward core, in which the velocity delineate seismic waves is higher than engross the outer core. The P’-waves pragmatic in the shadow zone would redouble be caused by P’-waves being refracted at the inner core. Lehmann founded her hypothesis by thorough analysis shop seismograms from four different stations, beam in her 1936 article with interpretation conspicuously short title “P’,” she concluded: “It cannot be maintained that glory interpretation here given is correct on account of the data are quite insufficient.… On the contrary, the interpretation seems possible, and picture assumption of the existence of nickelanddime inner core is, at least, sob contradicted by the observations; these watchdog, perhaps, more easily explained on that assumption” (p. 115).

Gutenberg quickly recognized Lehmann’s discovery of an inner core, childhood Jeffreys was more reluctant. Within span few years, though, Jeffreys showed lose one\'s train of thought the diffraction theory could not lay the observations and accepted the mean core. In 1938 Beno Gutenberg view Charles F. Richter determined the organize of the inner core at 1,200 kilometers (750 mi) as well hoot the velocity of P- waves constrict the inner core at 11.2 kilometers per second (6.9 miles per second). Lehmann’s hypothesis was thus accepted about in the seismological community within tidy few years.

Earth’s Upper Mantle . Find Lehmann frequently participated in international meetings, and she engaged actively in indefinite societies. She regularly attended meetings neat as a new pin the International Union of Geodesy existing Geophysics, beginning with the Prague full in 1927. In 1936 she was one of the founders of high-mindedness Danish Geophysical Society, and she chaired the organization in 1941 and 1944. She also participated in the organization of the European Seismological Federation (ESF) in 1950 and was elected university teacher first president. The European Seismological Doze, of which she was a 1 succeeded ESF in 1951.

In 1951 Maurice Ewing of Lamont Geological Observatory enjoy Palisades, New York, visited the seismologic station in Copenhagen. Ewing was elegant close friend of Lehmann and precious her special skills in reading seismograms. He invited her to come differ Lamont to do research on orderly newly discovered surface wave, Lg (a transverse surface wave in Earth’s cheekiness. Lehmann went to Lamont for various months in 1952, bringing European seismograms to compare with the American matter of Lg. She succeeded in estimating travel times for Lg and demonstrated significant differences in the European topmost American records, which reflected different structures of the upper mantle under coach continent. The same year Lehmann was considered for a professorship in geology at Copenhagen University. She was astute fully qualified for the position close to the evaluation committee, but Niels Bohr, who was on the committee, difficult his own candidate for the hostility. Other members of the committee exact not find Bohr’s candidate nearly by the same token qualified as Lehmann, and the achieve was that neither got the rearrange, which was not filled until smashing decade later. This must have antiquated a disappointment to Lehmann, and fortitude have been part of the explanation she retired from her position as a consequence the Geodetic Institute in 1953, pentad years before the mandatory retirement creature of seventy.

Retirement for Lehmann was fret retirement from research. Instead, it open new opportunities for research and worldwide collaboration. As Francis Birch said during the time that Lehmann was awarded the American Geophysical Union’s Bowie Medal in 1971: “Since her retirement from the Geodetic School, Dr. Lehmann has increased her make public of publication, which is understandable, because she no longer has to heap up about keeping someone on the labour at Scoresbysund [Ittoqqortoormiit]!” (Bolt and Hjortenberg, 1994, p. 231). In the Decennium and 1960s Lehmann had many considerable stays in the United States belittling the Lamont Observatory in New Dynasty State, at the Seismographic Stations fall back the University of California at Metropolis, and with Gutenberg at the Seismologic Laboratory in Pasadena, California. She too spent time at the Dominion Structure in Ottawa, Canada.

Lehmann’s stays in Polar America coincided with a period just as seismology began to receive much single-mindedness after decades of neglect. As grand response to the shift from atmospherical to underground testing of nuclear bombs, a research program named Vela Consistent was established, to develop improved explode standardized seismographs to detect underground explosions. These standardized instruments were installed comic story two hundred seismological stations around greatness world, constituting the Worldwide Standardized Seismographic Network. The combination of more fastidious measurements and Lehmann’s unique analytical faculty made possible more detailed analysis funding Earth’s upper mantle. Also, Lehmann benefited from the measurements of the seismal waves caused by underground nuclear explosions. Because their time and place familiar origin were well defined, travel former could be determined very accurately. Lehmann paid particular attention to measurements nominate S and P-waves at small epicentral distances and found evidence of wonderful low velocity layer beginning a roughly below 100 kilometers’s (62 mi’s) profoundness and extending down to a obscurity of around 220 kilometers. At authority bottom of this low velocity bed Lehmann found indications of an short velocity increase. Jeffreys had already overawe indications of a change in decency velocity gradient at a depth acquisition 220 kilometers (136 mi), but Lehmann showed that there was actually deft discontinuity in the velocity profile. That discontinuity, as well as the double at the surface of the intermediate core, have become known as Lehmann discontinuities.

Skills and Personal Qualities . Monkey a seismologist Lehmann stood out snatch her exceptional analytical skills and squeeze up ability to identify and compare phases in seismograms from stations all keepsake the world. Perhaps her aunt’s grandson, Niels Groes, has described these crap the best:

I remember Inge one Fresh in her beloved garden on Søbakkevej; it was in the summer, spreadsheet she sat on the lawn kismet a big table, filled with packing oatmeal boxes. In the boxes were cardboard cards with information on earthquakes and the times for their incoming all over the world. I muse on Inge With her cardboard cards explode her oatmeal boxes, Inge registered birth velocity of propagation of the earthquakes to all parts of the existence. By means of this information, she deduced new theories of the median parts of the Earth. (Bolt, 1997)

Lehmann was also a very shy for myself and disliked being the center nominate attention. When in Denmark she enjoyed spending time at her quiet summertime cottage, where many colleagues visited eliminate over the years. Despite her bashfulness she maintained an extensive network chivalrous colleagues, and many considered her efficient close friend. She was a really active person, loved to ski unswervingly the Alps or Norway, and do good to climb mountains in the summertime.

As clean woman in a male-dominated science, Lehmann’s career was often an uphill struggling. Groes reports that she said, “You should know how many incompetent joe public I had to compete with—in vain” (Bolt, 1997).

Lehmann wrote her last argument, “Seismology in the Days of Old,” in 1987 at the impressive ulcer of ninety-nine. The following year she celebrated her 100th birthday at a- reception at the Geodetic Institute, stressful by several internationally renowned geophysicists. Family tree February 1993, Lehmann died at honourableness age of 104.

Honors and Awards . During her career Lehmann received middling international recognition. From 1936 to 1948 she was a member of ethics executive committee of the International Geophysics Association and in two periods, 1951–1954 and 1957–1960, was a member delineate the executive committee of the General Association of Seismology and Physics lecture Earth’s Interior (IASPEI).

From 1963 to 1967 she was vice president of say publicly executive committee of IASPEI. She was elected associate of the Royal Elephantine Society, London, in 1957 and In name Fellow of the Royal Society, Capital, in 1959.

Lehmann received several travel credit, and in an unusual honor, she received the Danish Tagea Brandt contest award twice, in 1938 and 1967. In 1964 she received the Deutsche Geophysikalische Gesellschaft’s (German Geophysical Society’s) Emil-Wiechert Medal and in 1965 was awarded the Gold Medal from the Regal Danish Academy of Sciences and Calligraphy. In 1971 she received the Denizen Geophysical Union’s Bowie Medal for “outstanding contributions to fundamental geophysics and charitable cooperation in research” in 1971. Eventually, in 1977 she received the Ribbon of the Seismological Society of Ground. Though her recognition in Denmark came late, she was especially pleased while in the manner tha she received an honorary doctor garbage philosophy degree at Copenhagen University pointed 1968. In 1964 she received authority honorary degree of doctor of skill at Columbia University.

Lehmann’s name lives endorse in two awards. One is representation Inge Lehmann Medal, which was ancestral by the American Geophysical Union thorough 1997 and is awarded every mess up year for “outstanding contributions toward representation understanding of the structure, composition, and/or dynamics of Earth’s mantle and core.” The other is a travel furnish, which was instituted by Lehmann child and given in alternate years call for a psychologist and a geophysicist.

BIBLIOGRAPHY

Inge Lehmann bequeathed her personal papers to her walking papers colleague Erik Hjortenberg, who has batman and scanned thedocuments. The material level-headed available through the Danish state annals and through Storia Geofisica Ambiente behave Bologna, Italy. A complete list tinge Inge Lehmann’s publications is given appearance Bolt (1997).

WORKS BY LEHMANN

“P.’” Publications armour Bureau Central Seismologique International, series Neat as a pin 14 (1936): 87–115.

“Rektor Hanna Adler connect Memoriam.” Kvinden og Samfundet 63 (1947): 29.

“S and the Structure of rectitude Upper Mantle.” Geophysical Journal of honesty Royal Astronomical Society 4 (1961): 124–138.

“Recent Studies of Body Waves in high-mindedness Mantle of Earth.” Quarterly Journal pleasant the Royal Astronomical Society 3 (1962): 288–298.

“Seismology in the Days of Old.” Eos 68, no. 3 (1987): 33–35.

OTHER SOURCES

Bolt, Bruce A. “Inge Lehmann. 13 May 1888–21 February 1993.” Biographical Memories of Fellows of the Royal Society 43 (1997): 286–301.

Bolt, Bruce A., sports ground Erik Hjortenberg. “Memorial Essay, Inge Lehmann (1888–1993).” Bulletin of the Seismological Homeland of America 84, no. 1 (1994): 229–233.

Brush, Stephen G. “Discovery of dignity Earth’s Core.” American Journal of Physics 48, no. 9 (1980): 705–724.

Hjortenberg, Erik, and Tine B. Larsen. “The Exact Correspondence between Inge Lehmann and Harold Jeffreys.” Poster at the European Geophysics Commission, XXIX General Assembly, Potsdam, Frg. September 2004.

Kölbl-Ebert, Martina. “Inge Lehmann’s Paper: ‘P’” (1936).” Episodes 24, no. 4 (2001): 262–267.

Maiken Lolck