Inge Lehmann Discovered Earth's Inner Core In Her Free Time [View all]

[OKIsItJustMe]

https://news.ku.dk/lehmann_eng/

She struggled with prejudice and lack of opportunities as a woman in science. But she persisted and ultimately revolutionised our knowledge of Earth.

On a summer’s day in 1932, Inge Lehmann embarks on the journey of a lifetime. The 44-year-old usually spends her summer holidays sweating on Europe's steep mountain sides. But this summer, she's not going anywhere.

She is at her desk in her small, whitewashed cottage on a hilltop in Holte outside Copenhagen, surrounded by maps and cardboard boxes filled with documents. Each box contains data about arrival times and wave strengths from an earthquake at a specific location. One box with data from Tokyo, one from Vienna, one from London.

Slowly but surely, Inge Lehmann follows the earthquake waves through the many layers of Earth on a voyage of discovery into its burning inner core. 5,100 km beneath the surface of Earth, she discovers something no one else has seen before.

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After the earthquake in New Zealand, Inge Lehmann discovers something curious: Several seismographs in Europe have registered a few P-waves from the quake, even though they are in the shadow zone. She closely studies multiple seismograms from different locations to map the path of P-waves through Earth's interior. And then she has an idea: When the P-waves from the earthquake travel through Earth's liquid core, some of them hit another core. A hard core that deflects the waves and sends them to the shadow zone, where they otherwise should not arrive.


In Inge Lehmann's time, P-waves and S-waves were observed after an earthquake, as shown here. The dotted lines show the P-waves that Inge Lehmann interpreted as evidence that there had to be an inner core deep within Earth, which deflected certain P-waves and sent them into the area where they would otherwise not have arrived.
Graphics: Frans Wej Petersen

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