April 5 - Happy Birthday, Hedwig Kohn

Posted on April 5, 2020

Hedwig Kohn was German.

She was also Jewish.

Since she was born on this date in 1887, that wasn't a great combination.

Actually, Kohn was born in what was THEN Breslau, German Empire, but is NOW Wroclaw, Poland. She went to Breslau University and was able to earn a doctorate in physics as well as a "habilitation" - the qualification for teaching in a university. Needless to say, this was rare for a woman, back then; as a matter of fact, Kohn was one of only three women to qualify to teach university classes in all of Germany before World War II.

But just a few years after earning the right to teach at uni, Kohn was forced to leave her job and her nation. She was able to get a visa to the United Kingdom I 1939, but she lost the opportunity because of WWII stuff; finally she was able to get a visa to travel to Sweden and promptly went there in July 1940. From Sweden, she was able to travel to her goal - a teaching assignment at the Women's College of the University of North Carolina, in the United States - by taking a circuitous route: from Stockholm to Leningrad to Moscow to Vladivostok (a harbor town in the USSR, on the coast of the Sea of Japan), Yokohama (Japan), then on to San Francisco, Chicago, and FINALLY Greensboro, NC.

I imagine that Kohn took the Trans-Siberian Railroad (route pictured above).
What used to be called Leningrad is now called Saint Petersburg. The
second dot to the right (or east) of Saint Petersburg on this map is Moscow.

Kohn lived in the U.S. the rest of her life, with several positions as university physics professor and a final position as a research associate. She studied the intensity of light, emission lines of atoms and molecules, and ways of gaining information from light intensity and emission lines.

Intensity of light is a measurement of how many photons pass through a particular area per unit of time (say, per second).

Emission lines are particular bits of a spectrum that are emitted when a chemical element is hot and glowing. Each element has its own characteristic emission lines. 

Hedwig Kohn did a lot of research, wrote a lot of papers, trained a lot of students - and of course made an epic journey during a World War!

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