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The Actuary The magazine of the Institute & Faculty of Actuaries

Another actuarial pioneer

Inge Lehmann was a pioneer in the field of seismology. She was the first scientist to discover that the earth’s core was divided into an inner core and an outer core, and she became a leading authority on the structure of the earth’s upper mantle.

Inge Lehmann was born in Denmark in 1888. Her early education was at a progressive school where boys and girls studied the same subjects, played soccer and rugby, and learned to do needlepoint. This was a sharp contrast to the prejudice she later encountered in her career.

It was not easy for a woman to make her way into the scientific community at the beginning of the 20th century. After earning a master’s degree in mathematics in 1920, she went to work as an actuary, calculating life expectancies and statistical risks for insurance companies. In 1925, she helped establish seismological stations in Greenland and Copenhagen. Seismology would become her life work for the next 25 years.

Inge Lehmann studied the shock waves from a large earthquake that occurred near New Zealand in 1929. She theorised that these waves travelled into the core then bounced off some kind of boundary. Her interpretation of the seismological data from that earthquake was the foundation of a 1936 scientific paper in which she theorised that the earth’s centre consisted of two parts: a solid inner core surrounded by a liquid outer core.

Inge Lehmann died in 1993.