In 1936 she discovered the Earth has a solid inner core surrounded by a liquid molten outer core,
separated by what was to become known as the Lehmann Discontinuity. Her
research was theorised in a paper simply entitled P′. Her
discoveries were confirmed in 1970, when sensitive seismographs detected waves deflecting off the solid core.
Unable to be appointed to a professorship, because
she was a woman and under-valued in her homeland, she moved from Denmark to the USA in 1953, at the invitation of Professor
Maurice Ewing, Director of the Lamont Geological Observatory at Columbia University.
Seismological research was regarded as a somewhat backwater
of academic endeavour in the 1950's in comparison to the more prestigous
and exciting areas of atomic physics and radio astronomy, but suddenly seismology became the new 'hot' research
field, due to the requirement to monitor clandestine underground nuclear testing. The need for surveillance to monitor
secret nuclear tests led to Project Vela, which had three components: Vela Hotel, a satellite programme to
monitor nucleat tests; Vela Uniform, seismic monitoring; and Vela Sierra, an advanced satellite system, detecting testing
in outer space and the atmosphere.
Beginning
a new stage in her life at the age of 70, provided by the opportunities of well funded research through the
Vela Uniform programme, looking back on her life she said 'it had been a long rich life full of
victories and good memories'.
Inge Lehmann FRS, born Copenhagen
1888, died Copenhagen 1993.
