One of the 19th century's greatest scientists, and a devoted empiricist, Hermann Ludwig Ferdinand von Helmholtz made discoveries which were to be used in fields ranging from optics to meteorology. However, above all else he is known for the Helmholtz Resonator, which was used in early attempts at Fourier analysis, and for extending Joule's findings to a general principle of conservation of energy.
Born in Potsdam, Germany, on the 31st of August 1821, Helmholtz was the son of a gymnasium teacher. A sickly child, he was not allowed outside his own home for the first seven years of his life. During these years he learned languages and philosophy from his father, who hoped that his son would follow in his path.
However, although his father was a teacher of philosophy and literature, Hermann was more interested in science. He became one of the foremost empiricists, rejecting the beliefs still extant among many scientists at the time, that meaningful scientific conclusions could be reached from philosophical postulates.
Depite finding his interests to be in general science, Helmholtz went to study medicine at the Friedrich Wilhelm Medical Institute in Berlin, one of the very few state-subsidised centres of further education. Here he studied under Dr Johannes Müller, the greatest doctor of physiology of the day, doing physiological research in the mornings, and attending physics lectures and working through mathematical textbooks in his spare time. He also learned to play the piano, a study which was to prove of great use in his works on the sensation of tone.
One of the conditions of the state-sponsored education was that graduates from the medical school should serve for eight years in the Prussian Army on their graduation. Helmholtz was sent to join a Hussar regiment as a Squadron Surgeon. The Hussars were, as a cavalry regiment, essentially a militarised gentlemens' club, and Helmholtz's military duties were few. With the permission of his commanding officer, Helmholtz set up a small laboratory in the regimental barracks to continue his work in his spare time. By 1848, six years into his eight year commission, Helmholtz's scientific prowess was so apparent to all that Alexander von Humboldt personally interceded to ask that he be allowed to return to academia early.
He spent a short stint as a lecturer of Anatomy at the Berliner Kunstakademie (Berlin Academy of Fine Arts) but quickly moved on to the University of Königsberg where, at the recommendation of von Humboldt he became an assisant professor of Physiology and Pathology and the director of the Physiological Institute. However, the perpetual cold in Königsberg was so bad for both Helmholtz and his wife that they had to move on, going first to Bonn and then Heidelberg. Here he remained until 1871, when he was offered the chair of Professor of Physics at Berlin University.
Helmholtz's acheivements had not gone unnoticed over these years. The publication of such papers as 'On the Sensation of Tone as a Physiological Basis for the Theory of Music' in 1863 and 'On the Integrals of Hydrodynamic Equations to Which Vortex Motions Conform' in 1858 had been received with great interest both at home and overseas. It was for services to scientific progress that Helmholtz was ennobled in 1882, and out of respect that he was offered the post of first director of the Physico-Technical Institute in Berlin in 1888, a post which he was to hold until his death in 1894.
Helmholtz's first published work was his thesis, in which he investigated the connection between nerve fibres and nerve cells. This soon led him into a wider field of investigation, namely, the source of animal heat. It had recently been suggested by a series of papers published in Paris that the heat of a body was not only the result of chemical interactions, but that some vital principle was at work. Helmholtz however was able to approach the problem with the tools of both a mathematician and a physicist and argued that if there were a heat not subject to such physical laws, then it could be harnessed and used to create a perpetual motion machine, the concept of which had been shown to be impossible as early as 1775. From here he went on to generalise his findings to state that all heat was related to ordinary forces, and finally to state that force could not be destroyed, but only dissipated as heat. In his paper 'On the Conservation of Force', published in 1847, he finally completed Joule's work by publishing a complete Law of Conservation of Energy.
Further refutation of the ideas of the vitalists' ideas came with Helmholtz's measurements of the human eye. Before the invention of two new instruments, the ophthalmoscope and the ophthalmometer, no measurements had been possible, but Helmholtz was able to at a stroke show that the eye was not evidence of the divine creator, but a rather imperfect piece of workmanship, and at the same time demonstrate his ability to invent new instruments. Helmholtz's findings from his observations of the eye formed the centrepiece of his book 'The Handbook of Physiological Optics'. In his next book, 'On the Sensation of Tone...', Helmholtz extends his observations to the ear. However, his results are inconclusive, and the research is mainly notable for his invention of the Helmholtz resonator as a way of selecting or isolating a single frequency of sound. In his later life, he studied the nascent fields of electricty and magnetism. However, these had been advanced to the limits of classical mechanics by the likes of James Clerk Maxwell and Michael Faraday and were not to be further advanced until the advent of Einstein, who destroyed Helmholtz's theories by disproving the concept of ether.
- The Encyclopaedia Britannica, 15th edition: Helmholtz, Hermann von.