Skulls in the Stars

One of the topics of the history of science that has continued to fascinate me is the discovery of the principle of conservation of energy. As I discussed in my three-part series “Booms, Blood, and Beer” (part 1, part 2, part 3), some of the key discoveries were made by the most unlikely of investigators: a cannon-borer Count Rumford (booms), a physician Julius Robert Mayer (blood) and a brewer (beer).

The story of Mayer in particular has always fascinated me. He was a German physician who decided, after earning his license to practice medicine, to work as a ship’s doctor on a Dutch merchant ship sailing to Indonesia in 1840. While on the trip, he spend a lot of time observing and pondering nature, and some of his observations got him thinking about a law of conserved “force” that would be a philosophical complement of sorts to the law of conservation of matter. One key observation for him was seeing that, during a standard bloodletting of the sailors when they arrived in Jakarta, the venous blood was much redder than he was used to seeing in Europe. In discussions with other doctors, he learned that this is because less oxygen is consumed to heat the body in the hot climate of Indonesia than in the chilly northern parts of Europe.

This mechanism was already known by science at the time, but it triggered a train of thought in Mayer that became his obsession. At the time, there was much discussion about the nature of heat: what is it that makes some things warmer than others? The prevailing theory was that heat is its own physical fluid, called caloric, that could be released from a substance by friction or combustion. Also known but less popular was the (correct) theory that heat is simply the collective random motion of atoms and molecules. Heat spreads because some of those “hot” molecules collide with neighboring “cold” molecules and transfer their energy to them. Mayer’s thoughts about the generation of heat by the human body led him not only to consider heat a form of motion, but to postulate that there is a conserved “something,” that he called “force,” that could be used to unify thinking about physical phenomena throughout nature, from simple collisions of inanimate objects to the workings of living creatures.

Mayer was complete correct on the general principle, but he was no physicist. His early attempts to create a theory of what would eventually be called conservation of energy were crude and inaccurate — but contained the kernel of a truth that had never before been successfully elucidated. After submitting his first paper for publication (which would fail), he wrote to his scientist friend Carl Baur to explain his ideas and get feedback, where he first wrote what I call “The most beautiful wrong equation in history.”

In this post, we go through Mayer’s first (translated) letter to Baur and see how even incorrectly formulated ideas can be amazing — and beautiful. I used Google Translate along with some very crude understanding of German to handle the translations. The translations come from an 1890 book of Mayer’s collected papers.