Sound Science — Charles Sturm
Charles Sturm launched a distinguished career in mathematics by measuring the speed of sound in water.
As a young man growing up in Switzerland in the first half of the 19th century, Sturm aspired to a career in mathematics. And, Paris was the place to be, if you were an aspiring young scientist. But, as a Swiss citizen, Sturm was barred from entering the scientific community in Paris through the customary route — two years of study at the prestigious Ecole Polytechnique. So, instead Sturm used social connections to find his way into inner circle of the Paris scientific community.
Sturm found employment as the family tutor for a wealthy member of the Parisian high society. And so, in 1823 Sturm was frequently in the company of Francois Arago, friend of the family and the popular director of the Paris Observatory, and Arago’s good friend Alexander von Humboldt, world-famous scientist and explorer. Both men encouraged Sturm in his ambitions for a career in science. However, to gain full acceptance, Sturm first needed to prove his merit as a scientific peer and colleague.
An opportunity for Sturm to establish his credentials presented itself in 1825 when the Academy of Science announced a prize competition for the best research paper on the topic of the compressibility of liquids. Sturm entered the competition in collaboration with physicist Daniel Colladon, a friend from his student days in Geneva. They set out with a plan to measure the compressibility of water directly in the laboratory, and then validate their results by measuring the speed of sound through water, which depends on its compressibility.
The physics of sound propagation had been worked out nearly 150 years earlier by Isaac Newton, who estimated the speed of sound in air through experiments conducted on a university quad. Measuring the speed of sound through water was a more challenging proposition, because sound moves about 4 times faster in water as in air. In the pre-electronic age, when time could only be measured reliably down to fractions of a second, Sturm and Colladon would have to make their measurements over a significantly larger distance.
Sturm and Colladon devised special apparatus to measure the speed of sound between two boats about 10 miles apart in Lake Geneva. Their estimated speed of 1437.8 meters per second matched the result of calculations based on their laboratory measurements of the compressibility of water, using a theoretical formula previously derived by Siméon-Denis Poisson. Sturm and Colladon won in a second round of judging, after the Academy extended the competition in 1827.
Sturm’s share of the prize money, amounting to about $15,000 USD today, allowed him to pursue his dream of a career in mathematics. The recognition he gained from winning the competition opened the doors to jobs teaching mathematics and, eventually, election to the Academy of Science. Today, Sturm is best remembered for his mathematical research related to the solution of second order differential equations, a key element in the mathematics applied to physics and engineering.
Charles Sturm is one of the 72 scientists and engineers named on the Eiffel Tower.
