Top 10 Incredible Facts about Inge Lehmann

Top 10 Incredible Facts about Inge Lehmann

Inge Lehmann was a Danish seismologist and geophysicist who analysed how energy released from earthquakes travels through the Earth. Through her findings, she was able to discover the Earth’s core is composed of two parts: a solid metal core surrounded by an outer liquid core.

Before Lehmann’s discovery, seismologists believed the Earth’s core to be a single-molten sphere and had a hard time believing in Lehmann’s new findings. Frustrated by her peer ignorance and failure to take her findings into consideration, Lehman once referred to herself as “the only Danish seismologist.”

It was only after other seismologist analysed the seismic wave measurements and came to the same conclusion as her; Earth must have a solid inner core and a molten outer core to produce seismic waves that matched the measurements, that her 1936 discovery of the earth’s core was accepted.

That is not the only interesting fact about her, continue reading the article to learn 10 more incredible facts about Inge Lehmann;

1. A good educational foundation

Thomas George Webster, painting portraying boys and girls in a classroom – Wikipedia

Lehmann received her education at Fællesskolen, a pedagogically progressive high school founded by Hanna Adler. The school was ahead of its time since girls and boys were treated equally, enrolling them in the same curriculum and extracurricular activities. In such an environment, Lehmann was able to compete with her fellow students on equal ground, not limited by her gender.

Exposure to an environment where young people were co-educated without prejudice toward race, gender or social standing enabled Lehmann’s talent and intellectual abilities to be fully nurtured. It also gave her the mentality that both males and females had the same intellectual capabilities and standing in society. Sadly, this was not a notion that the environment outside the school shared.

Later in life Lehmann was surprised by the lack of equality in the world, telling Stephen Brush in 1980 that there was “No difference between the intellect of boys and girls was recognized, a fact that brought some disappointments later in life when I had to recognize that this was not the general attitude.”

2. Who inspired Lehmann’s intellectual development

Painting of séance by Richard Bergh, 1887 – Wikipedia

Lehmann was born into a privilege family surrounded by activists, intellectuals and artists who were critical in shaping her independent thinking personality. However, according to Lehmann, her father and Hanna Adler were the most significant influences on her intellectual development.

Her father, Alfred Georg Ludvik Lehmann, was an experimental psychologist who established the Laboratory of Psychophysics, one of the oldest laboratories of psychology in the world. In 1918, he was able to realize his dream of establishing psychology as an independent subject at the University of Copenhagen. This new curriculum emphasized on experimental and applied work, separating itself from its earlier ties to philosophy.

Hanna Adler was Niels Bohr‘s aunt. Niels Bohr was a Nobel Prize winner who made foundational contributions to understanding atomic structure and quantum theory. Hanna was one of the first women to take a master’s degree in physics at the University of Copenhagen in 1892. She also founded her own school, which was the first community school in Denmark.

3. Lehmann’s first time experiencing an earthquake

Illustration of a seismic wave from the earth – Pixabay

On a Sunday morning when Lehmann was15 or 16 she felt the floor beneath and the ceiling lamp sway for the first time in her life. At that time, Lehmann was sitting at home with her mother and sister and still recovering from the shock, her father entered the room and announced that they had experienced an earthquake.

This began her curiosity in understanding earthquakes. In 1925, she was able to fulfil her dream when she began her seismology career as an assistant to the geodesist Niels Erik Nørlund. She was tasked with the responsibility of setting up seismological observatories in Denmark and Greenland.

Remembering her teenage-hood experience later in life, Lehmann remarked that, despite scientists’ best efforts after the earthquake, they never did locate its epicentre.  

4. It took her 10+ years to graduate from university

Close up group of graduates holding a hat – Unsplash

At age 18, Lehmann achieved  a first rank mark in the entrance examination for Copenhagen University which she joined in 1907. At the university she studied mathematics, chemistry and physic before transferring to the University of Cambridge, in Cambridge, England in 1910 to focus on studying mathematics.

After an year at the University of Cambridge Lehmann returned back to Denmark because her health was suffering due to exhaustion from rigorous academic studies. While on break, between 1911 and 1918,  Lehmann instead worked as an actuarial assistant where risks are determined for use in determining insurance rates. This job greatly improved her computational skills which helped her later in her career.

She returned to the University of Copenhagen in 1918 and graduated with a cand.mag. in mathematics in 1920, at the age 32.

5. A prophet is always rejected in his hometown

Generally speaking, in the 20^th century, it was difficult for women to have a voice in Denmark. Lehmann was no exception to this, as she was not recognized among her peers in Denmark, with even world renowned Niels Bohr having difficulty accepting her.

To make matters worse her fellow seismologist would use and publish her thesis in their own names never to give her any credit. Also, the Royal Danish Academy of Sciences and Letters, a prominent Danish academy of science, never offered Lehmann membership despite her long career as head of the Geodesic Institute and remarkable discoveries.

The final straw for Lehman came in 1952 when she was denied a professorship in geophysics at Copenhagen University. The following year, she retired from her position at the Geodetic Institute and moved to America. In America, her voice as a woman was heard, and she went on to receive doctorates and honours in recognition of her work.

6. A seismic discontinuity named after her

A modern understanding of the Lehmann discontinuity – Wikipedia

While in the US, Lehmann was collaborating with Maurice Ewing and Frank Press on investigations of Earth’s crust and upper mantle when she discovered another seismic discontinuity, which are a step-change increase in the speeds of seismic waves at depths between 190 and 250 km.

This discontinuity was named after her, being coined as the Lehmann discontinuity. The Lehmann discontinuity is an abrupt increase of P-wave and S-wave velocities at the depth of 220 km (140 mi) and thickness of 220 km. It appears beneath continents, but not popular beneath oceans, and does not readily appear in globally averaged studies.

Several explanations have been proposed to explain the occurrence of the Lehmann discontinuity, including a lower limit to the pliable asthenosphere, a phase transition, and most plausibly, depth variation in the shear wave anisotropy.

7. Lehmann honoured in America

Dr. Bowie awarded the Bowie Medal – Wikimedia Commons

While in Denmark Lehmann did not receive much appreciation for her discoveries, but while in America she was showered with many honours for her outstanding scientific achievements, among them was the William Bowie Medal.

The William Bowie Medal is awarded annually by the American Geophysical Union for “outstanding contributions to fundamental geophysics and for unselfish cooperation in research”. It is the highest honour given by the AGU, American Geophysical Union.

In 1971 Lehmann was awarded the medal for discovering the Lehmann discontinuity, making her the first woman to receive such an honour.

The AGU also honoured her by creating the Inge Lehmann Medal in 1995. This Medal is given annually to a senior scientist in recognition of outstanding contributions to the understanding of the structure, composition, and dynamics of the Earth’s mantle and core.

8. Lehmann was described as “the master of a black art” for her computation skills

When Lehmann was awarded the William Bowie Medal, Professor Francis Birch said, “The Lehmann discontinuity was discovered through exacting scrutiny of seismic records by a master of a black art for which no amount of computerization is likely to be a complete substitute.”

The professor made this remark in honour of Lehmann’s hyper-accurate mathematical abilities.

Lehman’s mathematical background started in the University of Copenhagen and University of Cambridge where she studied mathematics, chemistry and physics. She further developed her computation skills when she became an actuary office for a few years. This background gave her the impeccable computing skill she made to make her world renowned discovery.

9. A tribute that sort of missed the mark

Memorial to Lehmann in Copenhagen – Wikipedia

In 2017 a memorial designed by Elisabeth Toubro was dedicated to Lehman at Frue Plads. The cryptic memorial is located on a corner, surrounded by the University of Copenhagen’s greatest luminaries. It consists of a column upon which there is a hemisphere.

This monument is located next to Niels Bohr. No doubt that Niels Bohr in his own rights deserves this recognition, but how do you place Lehmann beside a man who had difficulty accepting her discovery that the earth has a solid inner core inside a molten outer core.

In addition, the sculpture’s details are very wanting. On the flat side of the hemisphere there are a series of lines that look like one of the figures in Inge Lehmann’s renowned publication P’ however, the most important line – the actual P’-line – is missing.

10. One of the longest-lived scientist

Inge Lehman died in Copenhagen on February 21, 1993, three months shy of her 105th birthday. Despite having to deal with gender inequality all her life, Lehmann was contented with the life she had led.

Danish writer Nils Groes wrote of her in the UCLA profile: “One day at the hospital, Inge told us that all day she had been thinking about her own life and she was content. It had been a long and rich life full of victories and good memories.”