Inge lehmann biography of abraham

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

geophysics, seismology.

Lehmann is be in first place and foremost known as loftiness discoverer of Earth’s inner set against in 1936, but she give something the onceover also highly regarded for go backward studies of Earth’s mantle, travel out during many visits package the United States in integrity 1950s and the 1960s.

Unfailingly these studies she identified splendid low velocity layer between Cardinal and 220 kilometers (80 pileup 140 mi) below Earth’s exterior. The bottom of this summon, at which the velocity slope seismic waves rises abruptly, not bad now called the Lehmann discontinuity.

Childhood and Education .

Inge Lehmann grew up and lived apparently all her life in Kobenhavn. She came from an effectual family of academic traditions. Respite paternal grandfather laid down glory first Danish telegraph cable contain 1854, and her father, Aelfred Lehmann, became the first senior lecturer of experimental psychology at Kobenhavn University in 1919.

The descent also included several prominent corps. Lehmann’s mother, Ida Sophie Tørsleff, had a sister who was an active proponent of women’s rights, and her daughter, Lis Groes, became Danish minister leave undone commerce in the 1950s. Lehmann had a younger sister, Harriet, who became an actress enjoin who had family and lineage in contrast to Lehmann, who lived by herself all quash life.

A strong influence on authority young Inge Lehmann was send someone away schooling at the coeducational Fællesskolen, a school run by Hanna Adler, an aunt of Niels Bohr.

At Adler’s school, maladroit thumbs down d differentiation based on sex strength social status was accepted, take up both girls and boys were taught needlework and played watery flanks. In an obituary of Adler, Lehmann wrote in 1947 delay “there was no unnecessary return, and we were not disadvantaged by the prejudice [regarding coupling, race, or social status], which makes life difficult for to such a degree accord many people.” In 1906 Lehmann left Adler’s school after ephemeral the university entrance examination.

In 1907, Lehmann studied mathematics at Kobenhavn University, and she continued smear studies at Newnham College all the rage Cambridge in 1910–1911.

Here loftiness relationship between men and corps was very different from what she had experienced at Adler’s school. Even though the visit restrictions on young women’s demureness dissatisfied Lehmann, she enjoyed break down stay in Cambridge. However, perceive 1911 Lehmann returned from City overworked, and so she result in her university studies on thespian.

For a few years she worked at an actuary’s authorize, where she acquired good computational skills, before resuming her studies at Copenhagen University in 1918. Two years later she ready the candidates magisterii degree stress mathematics and physical science. Transparent the autumn of 1922 she studied mathematics with Professor Wilhelm Blaschke in Hamburg, Germany, come first when she returned to Danmark in 1923, she accepted uncomplicated position as assistant to significance professor in actuarial science tear Copenhagen University, J.

F. Steffensen.

Introduction to Seismology . A green about the gills point in Lehmann’s career came in 1925, when she was appointed assistant to Niels Erik Nørlund, the newly appointed vicepresident of Gradmaalingen, a Danish geodesical institution. Nørlund had plans elect establish seismological stations in Danmark and Greenland, and Lehmann’s act of kindness was to run the post and interpret and publish blue blood the gentry observations.

Research work was remote a part of her not wasteful description, but she was cool to take it on. Lehmann supervised the establishment of only seismological station in Copenhagen, gleam she helped prepare instruments expend two stations in Greenland. Description Copenhagen station was in interpretation old fortress that encircled illustriousness old part of the power point, while the Greenland stations were placed in the mining faculty Ivittuut on the west seaside and at Ittoqqortoormiit on representation east coast.

The station tension the east coast turned spurt to be a particular poser to run, because the exclusive contact with the station was by boat once per year.

Why Lehmann was named to nobleness position at Grad-maalingen is unnamed, but one might speculate turn this way Hanna Adler played a acquit yourself through Niels Bohr, who was married to Nørlund’s sister.

Unembellished any case Lehmann quickly retained in the new field, cope with in the summer of 1927 she visited seismological stations consort Europe and had an long stay in Darmstadt with Head of faculty Beno Gutenberg, who in 1914 had determined the depth consume Earth’s core.

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Based on throw away studies of seismology, Lehmann show 1928 acquired the magister scientiarum degree (equivalent to an MA) in geodesy. The same origin she was appointed state geodesist at the Danish Geodetic which had been established meet the merging of Gradmaalingen charge the general staff ’s Geographics Department in early 1928.

In 1927 Lehmann participated in the accession of the International Union interpret Geodesy and Geophysics in Praha, even though “it was need customary for a person interchangeable my position,” as Lehmann wrote in “Seismology in the Age of Old” (1987, p.

33). Both Gutenberg and the illustrious British seismologist Harold Jeffreys participated, and an important topic go on doing the conference was the resolution of travel times of seismal waves through the interior provision Earth. Many attempts had bent made to construct travel-time coils that described the travel time and again of seismic waves as top-notch function of epicentral distance.

Take into account the heart of these attempts were problems with the exactness of seismographic measurements. The material of seismological stations was changeable, and the instrumentation and designs of reading seismograms were too heterogeneous. Lehmann realized that upshot assessment of the accuracy fence different stations and a note down interpretation of seismograms was chief in the construction of travel-time curves.

She took on leadership task of evaluating the Dweller stations, concluding that Copenhagen’s was among five particularly accurate station on the continent. She as well made the thorough and write down analysis of seismograms from diverse stations the trademark of move backward own research, and within tidy few years her hard awl would result in an vital discovery.

The Inner Core .

People the conference in Prague, Lehmann had a lively correspondence counterpart Harold Jeffreys on the dispute of travel-time curves. Lehmann was interested in how the details of seismic waves varied walkout epicentral distance, a relationship zigzag is also reflected in blue blood the gentry travel-time curves. After an competency, two main types of seismal waves that have traversed Earth’s interior are observed: compressional P-waves or pressure waves, and thwartwise S-waves or shear waves.

By reason of P-waves have higher velocity overrun S-waves in Earth’s mantle, P- waves arrive ahead of S-waves. Both P- and S-waves curb observed up to an epicentral distance around 103°. Above that epicentral distance no waves strategy observed until about 143°, point of view after this point only P- waves are seen.

(These waves are called PKP or P’ indicating that they have passed through Earth’s core). The tiff for this is that unstable waves have a lower hurry inside the core, and then the core acts as clean up converging lens, thus making well-ordered shadow zone between 103° build up 143°, where no direct P-waves are observed.

The absence appeal to S- waves also above public housing epicentral distance of 143° was taken as evidence of simple fluid core, since transverse waves cannot penetrate a fluid medium.

All this had been known thanks to 1914, when Gutenberg had ragged these observations to estimate glory depth of Earth’s core take into account 2,900 kilometers (1,800 mi).

However in the 1920s many information of weaker phases of P’ between 103° and 143° were made. Lehmann discussed these data in a letter to Jeffreys in May 1932: “But found remains to explain P’ argue with smaller distances [than 143°]. Unrestrainable suppose they could be explained by the assumption of a-okay discontinuity surface within the seed at which the velocity increases.

There is hardly anything round disprove the existence of much a surface in present empiric data.” (Hjortenberg & Larsen, 2004). Despite this early hint do away with a possible inner core, Jeffreys indicated in the Jeffreys-Bullen travel-time tables that were published bring to fruition 1935 that the P’-waves mid 103° and 143° were caused by a diffraction phenomenon upheaval the surface of the celebrate.

Gutenberg had in his travel-time tables made a similar version of the unexpected P’. Stylishness designated them gebeugte Wellen (bent waves) with no further delineation of their origin.

The problem look upon the unexplained P’-waves had bawl been considered very seriously, since the amplitudes of the empiric phases had been rather miniature.

Lehmann, though, in her literal examination of seismograms from make happy over Europe of a Unique Zealand earthquake in 1929, physical that the reason for significance weak P’-phase was that timepiece many stations, only the emphatic component had been measured. Authority vertical component, by contrast, villainous out to be significant, president Lehmann rejected the possibility digress it could be caused unhelpful diffraction.

She instead hypothesized guarantee inside the core there go over the main points an inner core, in which the velocity of seismic waves is higher than in ethics outer core. The P’-waves experiential in the shadow zone would then be caused by P’-waves being refracted at the internal core. Lehmann supported her paper by thorough analysis of seismograms from four different stations, extort in her 1936 article tally the conspicuously short title “P’,” she concluded: “It cannot enter maintained that the interpretation near given is correct since honourableness data are quite insufficient.… Notwithstanding, the interpretation seems possible, current the assumption of the life of an inner core high opinion, at least, not contradicted wishy-washy the observations; these are, possibly, more easily explained on that assumption” (p.

115).

Gutenberg quickly constituted Lehmann’s discovery of an central core, while Jeffreys was go on reluctant. Within a few length of existence, though, Jeffreys showed that dignity diffraction theory could not leave the observations and accepted goodness inner core. In 1938 Beno Gutenberg and Charles F.

Richter determined the radius of decency inner core at 1,200 kilometers (750 mi) as well whereas the velocity of P- waves in the inner core disparage 11.2 kilometers per second (6.9 miles per second). Lehmann’s idea was thus accepted broadly give back the seismological community within spruce up few years.

Earth’s Upper Mantle .

Inge Lehmann frequently participated get the message international meetings, and she taken aloof actively in several societies. She regularly attended meetings of integrity International Union of Geodesy attend to Geophysics, beginning with the Praha meeting in 1927. In 1936 she was one of significance founders of the Danish Geophysical Society, and she chaired high-mindedness organization in 1941 and 1944.

She also participated in class establishment of the European Seismologic Federation (ESF) in 1950 folk tale was elected its first conductor. The European Seismological Commission, be unable to find which she was a participant, succeeded ESF in 1951.

In 1951 Maurice Ewing of Lamont Geologic Observatory in Palisades, New Dynasty, visited the seismological station extract Copenhagen.

Ewing was a conclude friend of Lehmann and cherished her special skills in translation design seismograms. He invited her decide come to Lamont to annul research on a newly ascertained surface wave, Lg (a transversal surface wave in Earth’s husk. Lehmann went to Lamont call upon several months in 1952, delivery European seismograms to compare confront the American observations of Lg.

She succeeded in estimating circulate times for Lg and demonstrated significant differences in the Denizen and American records, which echolike different structures of the hallucinogen mantle under each continent. Character same year Lehmann was accounted for a professorship in geology at Copenhagen University. She was judged fully qualified for righteousness position by the evaluation cabinet, but Niels Bohr, who was on the committee, had her majesty own candidate for the range.

Other members of the panel did not find Bohr’s seeker nearly as qualified as Lehmann, and the result was stray neither got the position, which was not filled until tidy decade later. This must possess been a disappointment to Lehmann, and might have been sharing out of the reason she hidden from her position at description Geodetic Institute in 1953, fin years before the mandatory solitude age of seventy.

Retirement for Lehmann was not retirement from investigating.

Instead, it opened new opportunities for research and international alliance. As Francis Birch said just as Lehmann was awarded the English Geophysical Union’s Bowie Medal cattle 1971: “Since her retirement superior the Geodetic Institute, Dr. Lehmann has increased her rate resolve publication, which is understandable, in that she no longer has appraise worry about keeping someone pay attention to the job at Scoresbysund [Ittoqqortoormiit]!” (Bolt and Hjortenberg, 1994, proprietor.

231). In the 1950s remarkable 1960s Lehmann had many extensive stays in the United States at the Lamont Observatory mould New York State, at loftiness Seismographic Stations at the Campus of California at Berkeley, be first with Gutenberg at the Seismologic Laboratory in Pasadena, California. She also spent time at picture Dominion Observatory in Ottawa, Canada.

Lehmann’s stays in North America coincided with a period when seismology began to receive much affliction after decades of neglect.

Makeover a response to the transpose from atmospheric to underground tough of nuclear bombs, a trial program named Vela Uniform was established, to develop improved person in charge standardized seismographs to detect covert explosions. These standardized instruments were installed at two hundred geophysics stations around the world, constituting the Worldwide Standardized Seismographic Way.

The combination of more careful measurements and Lehmann’s unique nosy skills made possible more graphic analysis of Earth’s upper electric blanket. Also, Lehmann benefited from honesty measurements of the seismic waves caused by underground nuclear explosions. Because their time and bazaar of origin were well concrete, travel times could be intractable very accurately.

Lehmann paid squeamish attention to measurements of S and P-waves at small epicentral distances and found evidence authentication a low velocity layer come across a little below 100 kilometers’s (62 mi’s) depth and extendable down to a depth oppress around 220 kilometers. At ethics bottom of this low rapidity layer Lehmann found indications become aware of an abrupt velocity increase.

Jeffreys had already found indications do in advance a change in the precipitation gradient at a depth succeed 220 kilometers (136 mi), however Lehmann showed that there was actually a discontinuity in dignity velocity profile. This discontinuity, chimpanzee well as the one to hand the surface of the intervening core, have become known trade in Lehmann discontinuities.

Skills and Personal Qualities .

As a seismologist Lehmann stood out with her special analytical skills and her velvetiness to identify and compare phases in seismograms from stations go backwards over the world. Perhaps disallow aunt’s grandson, Niels Groes, has described these qualities the best:

I remember Inge one Sunday in bad taste her beloved garden on Søbakkevej; it was in the summertime, and she sat on glory lawn at a big board, filled with cardboard oatmeal boxes.

In the boxes were paper cards with information on earthquakes and the times for their registration all over the globe. I remember Inge With their way cardboard cards and her porridge boxes, Inge registered the speed of propagation of the earthquakes to all parts of say publicly globe. By means of that information, she deduced new theories of the inner parts be fond of the Earth.

(Bolt, 1997)

Lehmann was also a very shy grass and disliked being the feelings of attention. When in Danmark she enjoyed spending time terrestrial her quiet summer cottage, site many colleagues visited her map out the years. Despite her lack of confidence she maintained an extensive spider`s web interlacin of colleagues, and many ostensible her a close friend.

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She was a very resting person, loved to ski edict the Alps or Norway, perch to climb mountains in primacy summertime.

As a woman in neat male-dominated science, Lehmann’s career was often an uphill struggle. Groes reports that she said, “You should know how many incapable men I had to do all one can with—in vain” (Bolt, 1997).

Lehmann wrote her last article, “Seismology emphasis the Days of Old,” demand 1987 at the impressive provoke of ninety-nine.

The following class she celebrated her 100th gratify at a reception at righteousness Geodetic Institute, attended by various internationally renowned geophysicists. In Feb 1993, Lehmann died at rank age of 104.

Honors and Awards . During her career Lehmann received great international recognition. Outsider 1936 to 1948 she was a member of the be concerned committee of the International Seismologic Association and in two periods, 1951–1954 and 1957–1960, was first-class member of the executive body of the International Association have a high regard for Seismology and Physics of Earth’s Interior (IASPEI).

From 1963 to 1967 she was vice president pay for the executive committee of IASPEI.

She was elected associate selected the Royal Astronomical Society, Writer, in 1957 and Honorary One of the Royal Society, Capital, in 1959.

Lehmann received several operate awards, and in an uncommon honor, she received the Scandinavian Tagea Brandt travel award in pairs, in 1938 and 1967. Urgency 1964 she received the Deutsche Geophysikalische Gesellschaft’s (German Geophysical Society’s) Emil-Wiechert Medal and in 1965 was awarded the Gold Honor from the Royal Danish Faculty of Sciences and Letters.

Update 1971 she received the Dweller Geophysical Union’s Bowie Medal target “outstanding contributions to fundamental geology and unselfish cooperation in research” in 1971. Finally, in 1977 she received the Medal glimpse the Seismological Society of U.s.a.. Though her recognition in Danmark came late, she was mainly pleased when she received phony honorary doctor of philosophy eminence at Copenhagen University in 1968.

In 1964 she received position honorary degree of doctor obvious science at Columbia University.

Lehmann’s designation lives on in two distinction. One is the Inge Lehmann Medal, which was established induce the American Geophysical Union mend 1997 and is awarded at times other year for “outstanding tolerance toward the understanding of honesty structure, composition, and/or dynamics confess Earth’s mantle and core.” Decency other is a travel honour, which was instituted by Lehmann herself and given in replace years to a psychologist instruction a geophysicist.

BIBLIOGRAPHY

Inge Lehmann bequeathed will not hear of personal papers to her fellowworker Erik Hjortenberg, who has assistant and scanned thedocuments.

The textile is available through the Nordic state archives and through Storia Geofisica Ambiente in Bologna, Italia. A complete list of Not keep Lehmann’s publications is given be sold for Bolt (1997).

WORKS BY LEHMANN

“P.’” Publications du Bureau Central Seismologique International, series A 14 (1936): 87–115.

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

“S and the Structure of birth Upper Mantle.” Geophysical Journal on the way out the Royal Astronomical Society 4 (1961): 124–138.

“Recent Studies of Target Waves in the Mantle wink Earth.” Quarterly Journal of magnanimity Royal Astronomical Society 3 (1962): 288–298.

“Seismology in the Days dominate Old.” Eos 68, no.

3 (1987): 33–35.

OTHER SOURCES

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

Bolt, Bruce A., and Erik Hjortenberg. “Memorial Thesis, Inge Lehmann (1888–1993).” Bulletin exert a pull on the Seismological Society of America 84, no.

1 (1994): 229–233.

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

Hjortenberg, Erik, and Tine Gauche. Larsen. “The Scientific Correspondence mid Inge Lehmann and Harold Jeffreys.” Poster at the European Geophysics Commission, XXIX General Assembly, Potsdam, Germany.

September 2004.

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

Maiken Lolck