HELMHOLTZ, HERMANN VON

HELMHOLTZ, HERMANN VON (1821–1894), German scientist.

Hermann Ludwig Ferdinand von Helmholtz was one of the most versatile scientists of the nineteenth century, endowed with a keen theoretical understanding of physical phenomena, with an unusual ability for putting them into a mathematical form, and with a rare intuition for instrumentation and experimental exploration. Above all, he was able to connect remote scientific fields with each other. During the last decades of his life, he held an outstanding position in European science.

life

Helmholtz was born in Potsdam, near Berlin, on 31 August 1821. Unable to afford a university education, he entered the Prussian military medical school, which was connected with the university. After taking his doctorate degree with the physiologist Johannes Müller in 1842, Helmholtz served a one-year internship in Berlin's Charité Hospital and then worked as a military surgeon in Potsdam until 1848. Many of Müller's students later came to play important roles in physiology and related subjects, and in 1845 some of them took part in founding the Physical Society, which remains the official German organization of physicists. In July 1847, Helmholtz read his memoir On the Conservation of Force to this group, announcing what was later called the energy conservation principle.

After serving as an anatomy instructor at the Berlin Academy and as an assistant to Müller for a year, Helmholtz began his academic career as a professor of physiology at the University of Königsberg in 1849. There he measured the velocity at which frog muscles conducted nerve impulses and devoted himself to sensory physiology. In 1850 he became famous for inventing the ophthalmoscope, which opened up vast possibilities for ophthalmology. Five years later, Helmholtz moved to the University of Bonn as a professor of anatomy and physiology, and three years later he taught physiology at the University of Heidelberg. During his Heidelberg years, he finished two treatises on sensory physiology, the Handbook of Physiological Optics (1856–1867) and On the Sensation of Tone as a Physiological Basis for the Theory of Music (1863)—presentations that still carry authority in their field and remain standard references in many respects.

The height of Helmholtz's career and fame began when he took up the Berlin chair of physics in 1871. The new German Reich had found in Helmholtz the "Reich's chancellor of science," as he was sometimes called. He began to devote himself almost exclusively to physics, mainly electro-dynamics.

Helmholtz was made a noble by the German emperor in 1883 and four years later became the founding president of the Physikalisch-Technische Reichsanstalt, a nonacademic government institute of physics and technology in Berlin-Charlottenburg. Helmholtz died in Berlin on 8 September 1894. After his death, the rapid development of modern physics away from its mechanistic foundations soon made Helmholtz's worldview outdated but did not overshadow his individual contributions.

work

The unifying idea of Helmholtz's scientific work can be found in his mechanistic interpretation of nature—that is, in the view that all physical phenomena can be explained in terms of mechanics. This idea served also as a background to Helmholtz's energy conservation principle, to which he was led by asking whether the mechanical equivalent of muscular heat and work could be accounted for solely by the metabolic process. If this were the case, the assumption that a separate life force existed would become obsolete. Helmholtz's energy conservation principle thus marked the beginning of organic physics, which sought to reduce all organic processes to the laws of physics and chemistry, and ultimately to mechanics.

To many contemporaries, Helmholtz's reductionism appeared to be downright materialism, and it is true that at the beginning of his career Helmholtz had strong sympathies with the materialist inclinations of the revolutionary movement of 1848. Helmholtz never claimed, however, that mental phenomena could be reduced to or identified with biological (and thus ultimately with mechanical) processes, as the materialists did. On the contrary, in the famous controversy with the physiologist Ewald Hering (1834–1918) on space perception, Helmholtz argued that visual perception requires a mind that has learned from movements in space and draws unconscious inferences from them. Hering, on the other hand, claimed that perception depends on an innate physiological mechanism that does not require a judging consciousness to turn incoming sensations into perceptions.

Other problems of visual physiology that Helmholtz dealt with included the accommodation of the eye, color vision, contrast phenomena, optical illusions, and eye movements. In physiological acoustics, he developed the resonance theory of hearing, in which the sensations produced by the resonating endings of the acoustic nerves are perceived as a tone. He also solved the problem of consonance and dissonance, which made it possible to explain musical harmony.

From his work with organ pipes, which he needed for his experiments on the physiology of hearing, Helmholtz was led to questions of hydrodynamics. In 1858 he demonstrated the invariance of vortices in ideal fluids and developed the notion of the vortex sheet, which foreshadowed the notion of the boundary layer, which is central to modern fluid mechanics.

In his work on electrodynamics, Helmholtz tried to mediate between James Clark Maxwell's field theory and the Continental approaches, which were based on action at a distance, merging them into a compromise version. The experimental work of his student Heinrich Hertz, which culminated in his detection of electromagnetic waves in 1887–1888, had originally emerged from attempts to confirm Helmholtz's rendering of Maxwell's theory.

Helmholtz is also known as the author of some twenty-five popular and philosophical essays. His interest in philosophy was roused by his father, who was an enthusiast of German idealism, and it gained momentum from his work on perception. In 1855 Helmholtz joined and stimulated the rising neo-Kantian movement with a lecture, "Human Vision," in which he propagated a new epistemology as a cure for speculation in the manner of Hegelian philosophy. He developed an empiricist theory of perception, called the theory of signs, which started from the skeptical claim that human sensations cannot be taken as images of reality, but only as signs, without any similarity to the objects signified. The order humans give to those sensations, however, originates with the outer objects, and this order can be taken as a true image of the world's causal order. One can never know for certain that a sensation is caused by an object, but all human perceptions are hypotheses to this effect and are constantly tested through voluntary manipulation of the world.

From his philosophy of perception, Helmholtz was led to the foundations of geometry, where he defended an empiricist interpretation of the axioms. Space has to be taken as the epitome of the movability of rigid bodies or, equivalently, of the congruence of relations between bodies and surfaces. He found that such movements and relations were possible not only in Euclidean space but also in non-Euclidean space. He concluded that non-Euclidean spaces are conceivable and that the Euclidean axioms are not necessarily true of space as claimed by Kant.

See alsoEinstein, Albert; Hertz, Heinrich; Maxwell, James Clerk; Physics; Science and Technology.

bibliography

Primary Sources

Helmholtz, Hermann von. Wissenschaftliche Abhandlungen. 3 vols. Leipzig, Germany, 1882–1895. An almost complete collection of Helmholtz's scientific papers.

——. Vorlesungen über theoretische Physik. 6 vols. Leipzig, Germany, 1897–1907. Lectures on theoretical physics, given during his time as president of the Physikalisch-Technische Reichsanstalt.

——. Epistemological Writings: The Paul Hertz/Moritz Schlick Centenary Edition of 1921. Edited by Robert S. Cohen and Yehuda Elkana. Translated by Malcolm F. Lowe. Dordrecht, Netherlands, and Boston, 1977. This edition has become famous for its extensive and congenial annotation in the context of rising logical empiricism.

——. Helmholtz's Treatise on Physiological Optics. Edited by James P. C. Southall. 3 vols. Rochester, N.Y., 1924–1925. Reprint, Mineola, N.Y., 2005. Translation of Handbuch der physiologischen Optik.

——. Science and Culture: Popular and Philosophical Essays. Edited by David Cahan. Chicago, 1995. Selected popular and philosophical writings.

Secondary Sources

Cahan, David, ed. Hermann von Helmholtz and the Foundations of Nineteenth-Century Science. Berkeley, Calif., 1993. An excellent collection, written by historians and philosophers of science and covering virtually all areas of Helmholtz's work. Includes a fairly complete bibliography of secondary works.

Cranefield, Paul F. "The Organic Physics of 1847 and the Biophysics of Today." Journal of the History of Medicine and Allied Sciences 12 (1957): 407–423. Vivid account of the program of organic physics, its context, and its limitations.

Darrigol, Olivier. "From Organ Pipes to Atmospheric Motions: Helmholtz on Fluid Mechanics." Historical Studies in the Physical and Biological Sciences 29 (1998): 1–51. Profound account of Helmholtz's contributions to fluid mechanics, exemplifying Helmholtz's unity of thought across many disciplines.

Hatfield, Gary. The Natural and the Normative: Theories of Spatial Perception from Kant to Helmholtz. Cambridge, Mass., 1990. Profound history of spatial perception in the nineteenth century, concentrating on the philosophical context.

Heidelberger, Michael. "Hermann von Helmholtz (1821–1894)." In Die großen Physiker. Vol. 1: Von Aristoteles bis Kelvin, edited by Karl von Meÿenn, 396–415, 474–475, and 528–531. Munich, Germany, 1997. Attempt at a short general account of Helmholtz's life and work.

Koenigsberger, Leo. Hermann von Helmholtz. 3 vols. Translated by Francis Welby. Oxford, U.K., 1906. Rich and authoritative, yet hagiographic and somewhat Whiggish account of Helmholtz's work and life by one of his students.

Rechenberg, Helmut. Hermann von Helmholtz: Bilder seines Lebens und Wirkens. Weinheim, Germany, 1994. Heavily illustrated, very readable scientific biography.

Richards, Joan L. "The Evolution of Empiricism: Hermann von Helmholtz and the Foundations of Geometry." British Journal for the Philosophy of Science 28 (1977): 235–253. Account of Helmholtz's foundational work on geometry and its later impact; still valid.

Schiemann, Gregor. Wahrheitsgew ißheitsverlust: Hermann von Helmholtz' Mechanismus im Anbruch der Moderne. Darmstadt, Germany, 1997. Thorough exploration of Helmholtz's mechanical interpretation of nature and its contemporary context in philosophy, science and society.

Michael Heidelberger