Heat, Light, and Emilie du Châtelet

By Laurel Corona

The Chateau de Cirey. Emilie du Chatelet and Voltaire set up a physics lab on the ground floor.

In 1800, when William Herschel shot a beam of sunlight through a glass prism and measured the temperature of each color of light, he noticed that the temperature increased from the violet to the red ends of the spectrum. Going further, he measured the temperature just beyond the edge of the visible red and discovered it was the hottest of all. The “calorific” rays, as he named them, behaved just like visible light without being detectable to the human eye. He had discovered infrared light.

Sixty-three years earlier, Emilie du Châtelet, anonymously mailed to the French Academy of Science an essay, “Dissertation on the Nature and Propagation of Fire,” which included the idea that different colors of light carried different amounts of heat. She wrote that the way to prove this was to refract light onto a row of thermometers corresponding to the various colors in the spectrum – exactly the experiment Herschel performed.

She was unable to carry out the experiment herself for lack of thermometers. Her lover, the writer and philosopher Voltaire, was using all of their lab equipment trying to prove that fire was matter. Still thinking of herself more as his assistant than a scientist in her own right, Emilie did not insist. If she had, it’s likely Herschel’s discovery would have been made right then.

Would she have received the recognition she deserved? It’s doubtful. Voltaire himself admitted that a work on Newton published in his own name had been practically dictated by his brilliant lover.

About the author: Laurel Corona is also the author of Penelope’s Daughter, The Four Seasons, and Until Our Last Breath: A Holocaust Story of Love and Partisan Resistance. She lives in San Diego. She welcomes visitors to her website at www.laurelcorona.com.

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