Hermann von Helmholtz

Hermann von Helmholtz (1821-1894), German scientist of extraordinary genius, whose contributions in physiology, optics, acoustics, and electrodynamics greatly advanced 19th-century scientific thought.

Hermann Ludwig Ferdinand von Helmholtz was born on August 31, 1821, in Potsdam, where his father, a teacher at the gymnasium, taught him languages and the scientific thinking of the time. In 1838 he entered the Friedrich Wilhelm Medical Institute in Berlin. There the renowned physiologist Johannes Muller grounded him in the prevailing Kantian approach to “nature philosophy,” which held that vital or nonphysical forces imperceptible to the senses accounted for physiological functions. Opposing this theory, Helmholtz soon came to believe that physiological forces as well as forces of inorganic nature could be perceived by the senses. Helmholtz became further convinced that such forces could be mechanically measured and understood; this belief carried through the rest of his life and led him to his later investigations and contributions.

While serving as a military surgeon, Helmholtz wrote his famous 1847 paper “On the Conservation of Force,” in which he explained that animal heat and muscle contraction were a result of physical and chemical forces. With several contemporaries he became associated with what was called the 1847 or mechanistic school of physiology. Helmholtz next examined the sciatic nerves of frogs, becoming the first to measure the velocity of nerve impulses. From 1856 to 1866, as a professor of anatomy primarily at the University of Heidelberg, he researched the eye, which vitalists of the time considered the organ that best illustrated the workings of nonmaterial forces. The result of this extensive research was his multivolume Physiological Optics, a work that remained for many decades the definitive study on the physiology and physics of vision. During these studies Helmholtz also invented the ophthalmoscope (an instrument used to view the interior of the eye) and developed a theory of color vision.

Next, studying the ear, Helmholtz formulated the resonance theory of hearing, in which certain organs of the inner ear were believed to function as tuned resonators. In 1863, with the publication of On the Sensation of Tone as a Physiological Basis for the Theory of Music, he further refuted the vitalists by demonstrating that the aesthetics of music was a function of the ear's mechanical ability to pick up wave motions of musical sounds.

After 1871, as professor of physics at the University of Berlin, Helmholtz became interested in electrodynamics, which he tried to reduce to a few mathematical principles. Drawing on his earlier discoveries of wave motions and energy transfer, he applied his mechanistic approach to meteorology. By the time of his death in Berlin on September 8, 1894, the explanation of the physical world in terms of classical mechanics was nearly played out. The revolution in physics brought on by the discovery of X rays and radioactivity and the development of relativity theory soon replaced the considerable advances that Helmholtz made during his century.