M A S T E R P A G E
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3.
By 1936, scientists had learned from the study of earthquake
waves that the Earth has three layers, crust, mantle, and core.
Denmark’s Inge Lehmann was the first to demonstrate the
existence of a change in composition midway through the core,
dividing it into an inner core and an outer core. This division is
now known as the Lehmann discontinuity.
As a girl, at the turn of the century, Lehmann attended the first
coeducational school in Denmark, which was founded and run by
Hanna Adler. (Adler’s nephew, Neils Bohr, was the first to
describe the physical makeup of the atom.) At that school,
Lehmann wrote many years later, “No difference between the
intellect of boys and girls was recognized—a fact that brought me
disappointments later in life when I found that this was not the
general attitude.”
Lehmann studied at Oxford, earned a master’s degree in
mathematics from the University of Copenhagen, and went to
work as an actuary, calculating life expectancies and statistical
risks for insurance companies. Beginning in 1925, however, she
also served as a staff member of the Danish Geodetic Institute,
helping to establish seismological stations in Greenland and in
Copenhagen—a part of the world not noted for its seismicity.
Seismology soon became her life work, and for 25 years, until just
before her retirement, she was the only Danish seismologist.
As early as 1910 scientists had noticed a shadow zone in the
Earth’s interior, but seismographs had not been refined enough to
explain this observation. In the course of the 1930s more and more
sensitive seismographs were being developed. At the Copenhagen
Seismological Observatory, Lehmann studied waves reflected
through the core from earthquakes in Japan. In 1936, after 10
years of studying seismograms, she interpreted the newly
revealed data to confirm the existence of a relatively small inner
core in the center of the Earth. The paper in which she reported
her findings has one of the shortest titles in the history of
seismology, if not of all science: It was called “P.”
Lehmann was among the founders of the Danish Geophysical
Society in 1936, and served as its president from 1941 until 1944.
She helped to formulate the constitution of the European
Seismological Federation and was elected its first president in
1950. She found time to attend most of the meetings of the
International Union of Geodesy and Geophysics, and served on
the executive committee of the International Seismological
Association from 1936 to 1944, from 1951 to 1954, and from
1957 to 1960. International cooperation in the sciences was one
of her passions. She was active in national and international
scientific organizations, and traveled in France, the Netherlands,
Belgium, and Germany, where she worked with some of the
leading seismologists of the day. In Canada, she worked at
Ottawa’s Dominion Observatory, and in the United States she
conducted research at the Seismological Laboratory, California
Institute of Technology; the University of California at Berkeley;
and the Lamont-Doherty Geological Observatory, Columbia
University, New York.
She loved hiking, skiing, and mountain climbing. Her favorite
place indoors, aside from her own cottage in Denmark, was an art
gallery. She loved to visit galleries and look at paintings
whenever she traveled, and she traveled widely, especially after
her retirement in 1953. She also loved music and gardening. Inge
Lehmann died in February, 1993, at the age of 105, leaving a
worldwide network of friends.
What title would you give this essay?
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