Inge Lehmann Google Doodle

Inge Lehmann: Discoverer of the Earth’s Inner Core

Today Google honors Inge Lehmann with a Doodle. She was a Danish seismologist who first discoverer of the Earth’s Inner Core, in 1936.

Inge Lehmann Google Doodle
Inge Lehmann Google Doodle

Inge Lehmann was born on 13 May 1888 at Osterbro by the Lakes in Copenhagen and attended a non-traditional school that practiced gender equity.

portrait of Inge Lehmann
Inge Lehmann

Inge Lehmann’s interest in mathematics was initially refuted by her parents, then she passed the entrance exam with first class standing. She went on to study mathematics in physics, chemistry and astronomy at the University of Copenhagen and Nenham College, Cambria. At Nenham College, Inge experienced “severe restrictions inflicted on the conduct of young girls” and returned home from exhaustion. Inge returned to University of Copenhagen where she graduated in 1920.

Inge Lehmann had previous experience through employment at an actuary office while on respite. Upon graduation she became assistant to professor in actuarial science at University of Copenhagen.

In 1925 she was appointed assistant to Professor N.E. Norland. Norland later installed seismographic stations of which she later manned. This led her to study geodesy with thesis topic in the nature of seismology earning mag. Scient. (magister scientiarum), 1928, University of Copenhagen.

At this time she was selected chief of the seismological department of Royal Danish Geodetic Institute until retirement in 1953. She travelled extensively, later earning her Doctor of Science degree in 1964 from Columbia University, NY.

Discoverer of the Earth’s Inner Core

After studying shock waves from a large earthquake occurring near New Zealand in 1929 she noticed a difference in the seismic data. It took a large earthquake for this data to become evident. From what she observed Lehmann asserted that because some P-waves, which should have been deflected by the core, were of record (not deflected) then a layering in the core must be present.

This layering, Inge Lehmann theorized, is of a solid inner core, liquid outer core and is separated by some sort of boundary between the two. This boundary is known as the Lehmann Discontinuity and while for over twenty years was highly controversial it was also later confirmed.

Earth inner core
The internal structure of Earth
Image: “Earth poster” by Kelvinsong/Wikimedia, licenced under CC BY-SA 3.0

Discontinuity theory

Inge Lehmann’s theory broke from conventional wisdom that previously claimed the Earth’s core was liquid followed by a solid mantle and then surrounded with a crust.

Each change in composition was considered to be abrupt and was called “discontinuity”. This led to the name of this discovery. The Lehmann Discontinuity theory also led to new thinking about the Earth’s composition overall.

Inge Lehmann received many awards including the Tagea Brandt Award twice (1938 ,1967), and the William Bowie Medal, 1971 which is the highest honor for the American Geophysical Union.

 

Inge Lehmann: Google Doodle (static)
Inge Lehmann: Google Doodle

Inge Lehmann died on February 21, 1993 in Copenhagen, at 104 years of age. Lehmann’s name will continue to be honoured in the geophysical world.