Inge Lehmann FRS  was a Danish

Denmark

Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

 seismologist

Seismology

Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. The field also includes studies of earthquake effects, such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, oceanic,...

 who, in 1936, argued that the Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

's core is not one single molten sphere, but that an inner core

Inner core

The inner core of the Earth, its innermost hottest part as detected by seismological studies, is a primarily solid ball about in radius, or about 70% that of the Moon...

 exists which has physical properties that are different from those of the outer core.

Life

Inge Lehmann was born and grew up in Østerbro, a part of Copenhagen

Copenhagen

Copenhagen is the capital and largest city of Denmark, with an urban population of 1,199,224 and a metropolitan population of 1,930,260 . With the completion of the transnational Øresund Bridge in 2000, Copenhagen has become the centre of the increasingly integrating Øresund Region...

, as daughter of the experimental psychologist

Psychologist

Psychologist is a professional or academic title used by individuals who are either:* Clinical professionals who work with patients in a variety of therapeutic contexts .* Scientists conducting psychological research or teaching psychology in a college...

 Alfred Georg Ludvik Lehmann (1858–1921). She received her school education at a pedagogically progressive high school led by Hanna Adler, an aunt of Niels Bohr

Niels Bohr

Niels Henrik David Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in...

. According to Lehmann, her father and Adler were the two most significant influences for her intellectual development. After having finished school, she studied, with some interruptions due to poor health, mathematics at the universities of Copenhagen and Cambridge

Cambridge

The city of Cambridge is a university town and the administrative centre of the county of Cambridgeshire, England. It lies in East Anglia about north of London. Cambridge is at the heart of the high-technology centre known as Silicon Fen – a play on Silicon Valley and the fens surrounding the...

. After a few years of work in the insurance business she became an assistant to the geodesist

Geodesy

Geodesy , also named geodetics, a branch of earth sciences, is the scientific discipline that deals with the measurement and representation of the Earth, including its gravitational field, in a three-dimensional time-varying space. Geodesists also study geodynamical phenomena such as crustal...

 Niels Erik Nørlund, who assigned her the task of setting up seismological observatories in Denmark and Greenland

Greenland

Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...

. The beginning of her interest in seismology dates back to this time. In 1928 she passed her exam in geodesy and accepted a position as state geodesist and head of the department of seismology at the Geodetical Institute of Denmark, which was led by Nørlund.

In a paper with the unspectacular title P, she was the first to interpret P wave

Seismic wave

Seismic waves are waves of energy that travel through the earth, and are a result of an earthquake, explosion, or a volcano that imparts low-frequency acoustic energy. Many other natural and anthropogenic sources create low amplitude waves commonly referred to as ambient vibrations. Seismic waves...

 arrivals which inexplicably appeared in the P wave shadow of the Earth's core as reflexions at an inner core. This interpretation was adopted within two to three years by other leading seismologists of the time, such as Beno Gutenberg

Beno Gutenberg

Beno Gutenberg was a German-American seismologist who made several important contributions to the science...

, Charles Richter, and Harold Jeffreys

Harold Jeffreys

Sir Harold Jeffreys, FRS was a mathematician, statistician, geophysicist, and astronomer. His seminal book Theory of Probability, which first appeared in 1939, played an important role in the revival of the Bayesian view of probability.-Biography:Jeffreys was born in Fatfield, Washington, County...

. The Second World War and the occupation of Denmark by the German army hampered Lehmann's work and her international contacts significantly during the following years.

In the last years until her retirement in 1953 the relations between her and other members of the Geodetical Institute deteriorated, partly probably because she had little patience with less competent colleagues. After 1953, Inge Lehmann moved to the USA for several years and collaborated with Maurice Ewing

Maurice Ewing

William Maurice "Doc" Ewing was an American geophysicist and oceanographer.Ewing has been described as a pioneering geophysicist who worked on the research of seismic reflection and refraction in ocean basins, ocean bottom photography, submarine sound transmission , deep sea coring of the ocean...

 and Frank Press

Frank Press

Frank Press is an American geophysicist.Born in Brooklyn, New York, Press was science advisor to President Jimmy Carter from1976 to 1980,and president of the U.S. NationalAcademy of Sciences from 1981 to 1993...

 on investigations of the Earth's crust

Crust (geology)

In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...

 and upper mantle

Mantle (geology)

The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....

. During this work, she discovered another seismic discontinuity, which lies at depths between 190 and 250 km and is usually referred to as "Lehmann discontinuity

Lehmann discontinuity

The Lehmann discontinuity refers to an abrupt increase of P-wave and S-wave velocities in the vicinity of 220±30 km depth, discovered by seismologist Inge Lehmann. It appears beneath continents, but not usually beneath oceans, and does not readily appear in globally averaged studies...

" in honor of its discoverer. Francis Birch

Francis Birch (geophysicist)

Albert Francis Birch was an American geophysicist best known for his experimental work on the properties of Earth-forming minerals at high pressure and temperature, in 1952 he published a well-known paper in the Journal of Geophysical Research ,where he demonstrated that the mantle is chiefly...

 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..."

She received many honors for her outstanding scientific achievements, among them the Harry Oscar Wood Award (1960), the Emil Wiechert

Emil Wiechert

Emil Johann Wiechert was a German geophysicist who presented the first verifiable model of a layered structure of the Earth.-Life:...

 Medal (1964), the Gold Medal of the Danish Royal Society of Science and Letters (1965), the
Tagea Brandt Rejselegat

Tagea Brandt Rejselegat

The Tagea Brandt Rejselegat is awarded annually, on the 17 March.The scholarship was created and endowed by Danish industrialist Vilhelm Brandt in honor of his wife, Tagea...

 (1938 and 1967), the election as a Fellow of the Royal Society (1969), the William Bowie

William Bowie

William Bowie, B.S., C.E., M.A. was an American geodetic engineer.-Background and education:He was born at Grassland, an historic estate near Annapolis Junction, Anne Arundel County, Maryland, to Thomas John Bowie and Susanna Anderson. He was educated in public schools, at St...

 Medal (1971, as the first woman), and the Medal of the Seismological Society of America (1977). Furthermore, she was awarded honorific doctorates of Columbia University

Columbia University

Columbia University in the City of New York is a private, Ivy League university in Manhattan, New York City. Columbia is the oldest institution of higher learning in the state of New York, the fifth oldest in the United States, and one of the country's nine Colonial Colleges founded before the...

, New York, in 1964 and of the University of Copenhagen in 1968 as well as numerous honorific memberships. The asteroid 5632 was named Ingelehmann in her honour. In Aventura, Florida

Aventura, Florida

Aventura is a planned, suburban city located in northeastern Miami-Dade County, Florida. The city name is from the Spanish word for "adventure", and was named "Aventura" after one of the developers of the original group of condominiums in the area remarked to the others, "What an adventure this is...

, there is a stretch of U.S. 1

U.S. Route 1 in Florida

U.S. Route 1 in Florida runs along the state's east coast from Key West to its crossing of the St. Marys River into Georgia north of Boulogne, and south of Folkston. US 1 was designated through Florida when the U.S. Highway System was established in 1926.US 1 runs in the state of Florida, and...

 and a bridge named in her honour.

In 1997 the American Geophysical Union

American Geophysical Union

The American Geophysical Union is a nonprofit organization of geophysicists, consisting of over 50,000 members from over 135 countries. AGU's activities are focused on the organization and dissemination of scientific information in the interdisciplinary and international field of geophysics...

 established the Inge Lehmann Medal

Inge Lehmann Medal

The Inge Lehmann Medal is given out by the American Geophysical Union to recognize "outstanding contributions to the understanding of the structure, composition, and dynamics of the Earth's mantle and core". The award was created in 1997 and named after Inge Lehmann...

 to honor "outstanding contributions to the understanding of the structure, composition, and dynamics of the Earth’s mantle and core."

Publications and honors

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

In 1971, Inge Lehmann was presented with the Allan Abrigo Medal of Excellence, the American Geophysical Union

American Geophysical Union

The American Geophysical Union is a nonprofit organization of geophysicists, consisting of over 50,000 members from over 135 countries. AGU's activities are focused on the organization and dissemination of scientific information in the interdisciplinary and international field of geophysics...

's highest honor, which is granted to a scientist who has made fundamental contributions to the study of geophysics.