Inge Lehmann and Earth’s deepest Secret

April 3, 2026

22 min read

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Inge Lehmann and Earth’s deepest Secret

Science writer Hanne Strager explores how the trailblazing Danish seismologist Inge Lehmann overcame self-doubt to discover that Earth has a solid inner core, overturning the long-held belief that it was liquid

By Carol Sutton Lewis, Jenny Dare & The Lost Women of Science Initiative

Columbia University Press (image); Lily Whear (composite)

In this episode of Lost Women of Science Conversations, host Carol Sutton Lewis speaks with science writer Hanne Strager about her biography of Inge Lehmann, the pioneering Danish seismologist who discovered that Earth has a solid inner core.

Largely unknown outside scientific circles, Lehmann fundamentally transformed our understanding of what lies at the heart of our planet. She did this in 1936 by identifying anomalies in earthquake waves that others had overlooked. At the time, scientists believed Earth’s core was entirely liquid. Lehmann proposed instead that a solid inner core lay hidden within it—a groundbreaking insight that reshaped geophysics.

In revisiting Lehmann’s story, Strager highlights that Lehmann’s legacy is one of resilience and perseverance—proof that early setbacks do not define a person and that brilliance can flourish, even later in life.

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TRANSCRIPT

Hanne Strager: I think her legacy is resilience and perseverance. How much it matters that you carry on, even despite having a huge mental, nervous breakdown in your youth, you can still rise. There's still a whole life in front of you.

Carol Sutton Lewis: Hello and welcome to Lost Women of Science: Conversations. I'm Carol Sutton Lewis. In this series of conversations, we talk to authors and artists who've discovered and celebrated female scientists in books, poetry, film and the visual arts.

I'm delighted to be joined today by the brilliant science writer Hanne Strager, who's written award winning books on subjects including killer whales and Darwin. Hanne has recently turned her focus to Inge Lehmann, a little known Danish scientist. Hanne's biography is called, If I'm Right and I Know I Am. Inge Lehmann, the woman who discovered Earth's innermost secret. The book gives us fresh and fascinating insight into a woman whose study of the waves from earthquakes led to a new understanding of what lies at the very center of our planet.

Hanne, thanks so much for joining us.

Hanne Strager: Thank you so much for having me!

Carol Sutton Lewis: So you're a widely acclaimed biologist, you're an author, a museum director. You could have chosen anyone to make the next subject of a research project. Tell us what attracted you to Inge Lehmann, her life, and her story.

Hanne Strager: I think that what attracted me was that I didn't know her. I met geologists at my work at the Natural History Museum in Denmark, who said that, “well, you know, she's probably the most famous geologist from Denmark. She's amazing!” And I was like, “I've never even heard of her, not in school, not at university. I never heard of her,” and neither did anyone else. And that's what was the intriguing part. How could we have someone so interesting and who had contributed so much, and then why didn't we know of her?

Carol Sutton Lewis: And so how did you go about researching her, since she wasn't so well-known?

Hanne Strager: Well, the first thing I did was that I went to the National Archives of Denmark and ordered all her correspondence. I'm not a historian or not used to working in archives, so I didn't really know what to expect, but they rolled in this trolley full with cardboard boxes and just left it at my table, and I started opening the cardboard boxes, and they were all of them full of letters and papers and envelopes, and it was completely unorganized. There could be letters from 1931 lying next to one from 1982 and it was really, really difficult.

So, I teamed up with a historian who taught me a little bit of the tricks of the trade, how you do that. But what really made the whole project change was when I found a distant relative, her mother's sister's grandson, who was still alive. She didn't marry, she didn't have any children herself, and he had a box of her private letters in his attic. He lent me the box. That gave me another perspective of her, because the letters that were in the National Archives were mainly the professional side of her, but with the letters in the box I also got a more private and personal side of her.

Carol Sutton Lewis: And so armed with both that personal and public side of her, Can you paint us a picture of Inge’s family life?