What were the most beautiful experiments in physics (link via Making Light, among others)? The concept of beauty (or "elegance", as mathematicians tend to put it) in science is not any better defined than it is in art or literature; it’s a subjective quality that’s been the subject of arguments for milennia and probably since humanity first put burnt stick to cave wall or arranged some shells. Physicist Chad Orzel mused about the list and wondered why the Michelson-Morley experiment (which disproved the existance of luminous aether which had long been assumed to exist) didn’t make the cut. His guess is that experimental complexity (or its close analog, the degree to which a physics professor can demonstrate the experiment during a lecture) had something to do with it. But the Michelson-Morley experiment seems elegant to me; its results were surprising and important, it was conceptually (if not in practice) a simple experiment, and it involved proving that something didn’t exist. In math, disproving something is easy; you can use the proof by contrapositive (in you can show that A leads to B, and therefore the untruth of B leads to the untruth of A; that is, if the existance of Bigfoot is logically equivalent to the supremacy of the Bavarian Illuminati, the lack of Illuminati means that sasquatch hunters are out of luck). Or you can prove it by assuming that the proposition is true and showing that your assumption leads to a contradiction. (Euclid’s proof that there are an infinite number of primes is a classic example to this.) But proof by contradiction is hard to do in real life. One can’t very well build a universe where the speed of light isn’t constant and probe it for inconsistancies. What generally happens is that you show that some physical result that shouldn’t happen if your assumption is true happens anyway (or, contrawise, that one that should doesn’t). The Michelson-Morley experiment — which Prof. Orzel notes wasn’t expected to return the negative results that it did — inovlved floating the experimental apparatus in a vat of mercury. Even so, there were probably factors that could have skewed the results (or at least could have been interpreted as skewing the results) had they not been so striking. Commonsense experiments gain a slight edge in terms of elegance, I think. Observing that the inside of ovens didn’t emit infinite radiation was a first step towards quantum theory. An early experiment performed by Benjamin Thompson, Baron Rumford, that cast doubts on the caloric fluid was barely more complex.

Rumford was born Benjamin Thompson, in Massachussetts. He was a lifelong student of heat: the Rumford fireplace is still in use today, he made early attempts to calculate the relationship between work and heat, and his "Rumford grate" was a precursor to central heating. A Loyalist during the American Revolution, he fled to England then returned to fight for the British; after America’s independence was won, he was knighted for his service to the British Crown and spent some time in experimenting with heat and ballistics. When he fell under suspicion of being a spy for the French, he went to Paris, then meandered to Bavaria, where he performed the cannon experiment. While in Bavaria, he devised plans to improve Bavarian livestock, studied food ("The pleasure enjoyed in eating depends first upon the agreeableness of the taste of the Food; and secondly, upon its power to affect the palate"), and put his ideas to the test in the Bavarian workhouses which he founded. (He may also have spied on Bavaria for one or more parties; it would have been entirely in keeping with his character.)

In the workhouses, Bavaria’s poor were fed nourishing vegetarian food (in the process of feeding them as cheaply as possible, Thompson introduced the potato to the Bavarian diet) in exchange for making uniforms for the Bavarian military. Thompson even managed to turn a profit; he was ennobled as a count of the Holy Roman Empire and chose to name himself after Rumford (now Concord), New Hampshire, where he had met and married his wealthy first wife. Rumford returned to England, remarried, founded the Royal Society, married Lavoisier‘s widow, set up London’s first soup kitchens. Having turned his attention to the nature of food, Rumford churned out a number of inventions, including the kitchen range, the pressure cooker, the double boiler, and the first modern coffee pot.

And yet today, Rumford is almost entirely forgotten, remembered principally for his one experiment with cannons. Why? One report sums it up neatly:

Rumford was overbearingly arrogant and had no friends, as well as having a life filled with repeated cycles of rapid rises to prominence followed by equally rapid falls to penury. His abrasive personality and style are perhaps why his many innovations were not widely chronicled by historians.

For all his accomplishment, Rumford seems to have been almost universally loathed by his peers. History is not kind to the unpopular. Upon his death in 1814, Rumford endowed a chair in physics at Harvard; maybe if he had also endowed a chair in journalism, we’d know his name today.