| Hermann von Helmholtz | |
|---|---|
| Born | August 31, 1821 Potsdam, Kingdom of Prussia |
| Died | September 8, 1894 (aged 73) Charlottenburg, German Empire |
| Residence | Germany |
| Nationality | Germany |
| Fields | Physics, physiology and psychology |
| Institutions | University of Königsberg University of Bonn University of Heidelberg University of Berlin |
| Alma mater | Royal Friedrich-Wilhelm Institute |
| Doctoral advisor | Johannes Peter Müller |
| Doctoral students |
Albert Abraham Michelson |
| Other notable students | Henry Augustus Rowland Wilhelm Wundt |
| Known for | Conservation of energy Helmholtz free energy |
Hermann Ludwig Ferdinand von Helmholtz (August 31, 1821 – September 8, 1894) was a German physician and physicist who made significant contributions to several widely varied areas of modern science. In physiology and psychology, he is known for his mathematics of the eye, theories of vision, ideas on the visual perception of space, color vision research, and on the sensation of tone, perception of sound, and empiricism. In physics, he is known for his theories on the conservation of energy, work in electrodynamics, chemical thermodynamics, and on a mechanical foundation of thermodynamics. As a philosopher, he is known for his philosophy of science, ideas on the relation between the laws of perception and the laws of nature, the science of aesthetics, and ideas on the civilizing power of science. The largest German association of research institutions, the Helmholtz Association, is named after him.[1]
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Helmholtz was the son of the Potsdam Gymnasium headmaster, Ferdinand Helmholtz, who had studied classical philology and philosophy, and who was a close friend of the publisher and philosopher Immanuel Hermann Fichte. Helmholtz's work is influenced by the philosophy of Fichte and Kant. He tried to trace their theories in empirical matters like physiology.
As a young man, Helmholtz was interested in natural science, but his father wanted him to study medicine at the Charité because there was financial support for medical students.
Trained primarily in physiology, Helmholtz wrote on many other topics, ranging from theoretical physics, to the age of the Earth, to the origin of the solar system.
Helmholtz's first academic position was associate professor of physiology at the Prussian University of Königsberg, where he was appointed in 1849. In 1855 he accepted a full professorship of anatomy and physiology at the University of Bonn, also in Prussia. He was not particularly happy in Bonn, however, and three years later he transferred to the University of Heidelberg, in Baden, where he served as professor of physiology. In 1871 he accepted his final university position, as professor of physics at the University of Berlin.
His first important scientific achievement, an 1847 physics treatise on the conservation of energy was written in the context of his medical studies and philosophical background. He discovered the principle of conservation of energy while studying muscle metabolism. He tried to demonstrate that no energy is lost in muscle movement, motivated by the implication that there were no vital forces necessary to move a muscle. This was a rejection of the speculative tradition of Naturphilosophie which was at that time a dominant philosophical paradigm in German physiology.
Drawing on the earlier work of Sadi Carnot, Émile Clapeyron and James Prescott Joule, he postulated a relationship between mechanics, heat, light, electricity and magnetism by treating them all as manifestations of a single force (energy in modern terms[2]). He published his theories in his book Über die Erhaltung der Kraft (On the Conservation of Force, 1847). Whether or not Helmholtz knew of Julius Robert von Mayer's discovery of the law of conservation of energy in the beginning of the 1840s is a point of controversy. Helmholtz did not quote Mayer in his work and was accused by contemporaries of plagiarism.
In the 1850s and 60s, building on the publications of William Thomson, Helmholtz and William Rankine popularized the idea of the heat death of the universe.
The sensory physiology of Helmholtz was the basis of the work of Wilhelm Wundt, a student of Helmholtz, who is considered one of the founders of experimental psychology. He, more explicitly than Helmholtz, described his research as a form of empirical philosophy and as a study of the mind as something separate. Helmholtz had, in his early repudiation of Naturphilosophie, stressed the importance of materialism, and was focusing more on the unity of "mind" and body.[3]
In 1851, Helmholtz revolutionized the field of ophthalmology with the invention of the ophthalmoscope; an instrument used to examine the inside of the human eye. This made him world famous overnight. Helmholtz's interests at that time were increasingly focused on the physiology of the senses. His main publication, entitled Handbuch der Physiologischen Optik (Handbook of Physiological Optics or Treatise on Physiological Optics), provided empirical theories on depth perception, color vision, and motion perception, and became the fundamental reference work in his field during the second half of the nineteenth century. It was first translated into English under the editorship of James P. C. Southall on behalf of the Optical Society of America in 1924-5. His theory of accommodation went unchallenged until the final decade of the 20th century.
Helmholtz continued to work for several decades on several editions of the handbook, frequently updating his work because of his dispute with Ewald Hering who held opposite views on spatial and color vision. This dispute divided the discipline of physiology during the second half of the 1800s.
In 1849, while at Königsberg, Helmholtz measured the speed at which the signal is carried along a nerve fibre. At that time most people believed that nerve signals passed along nerves immeasurably fast.[4] He used a recently dissected sciatic nerve of a frog and the calf muscle to which it attached. He used a galvanometer as a sensitive timing device, attaching a mirror to the needle to reflect a light beam across the room to a scale which gave much greater sensitivity.[4] Helmholtz reported[5][6] transmissions speeds in the range of 24.6 - 38.4 meters per second.[4]
In 1863 Helmholtz published Die Lehre von den Tonempfindungen als physiologische Grundlage für die Theorie der Musik (On the Sensations of Tone as a Physiological Basis for the Theory of Music), once again demonstrating his interest in the physics of perception. This book influenced musicologists into the twentieth century. Helmholtz invented the Helmholtz resonator to identify the various frequencies or "tones" present in musical and other sounds containing by multiple tones.[7] Alexander Graham Bell in particular was interested in how Helmholtz used resonators to mimic vowel sounds. Due to not being able to read German, Bell misconstrued Helmholtz' diagrams as meaning that Helmholtz had transmitted vowel sounds over a wire, whereas Helmholtz was merely using electrical stimulation to keep his resonators in motion without manual intervention. Bell reasoned that if vowels could be transmitted, then consonants also should be possible. He tried, and failed, to reproduce what he thought had already been done by Helmholtz. However, Bell was later to say that if he had been able to read German he would probably have given up the task as impossible, but in the event, went on to invent the telephone using the harmonic telegraph as the basis.[8]
The translation by Alexander J. Ellis was first published in 1875 (the first English edition was from the 1870 third German edition; Ellis's second English edition from the 1877 fourth German edition was published in 1885; the 1895 and 1912 third and fourth English editions were reprints of the second).[9]
Helmholtz studied the phenomena of electrical oscillations from 1869 to 1871, and in a lecture delivered to the Nat. Hist. Med. Ver. at Heidelberg on April 30, 1869 titled On Electrical Oscillations he indicated that the perceptible damped electrical oscillations in a coil joined up with a Leyden jar were about 1/50th of a second in duration.[10] In 1871 he announced that the velocity of the propagation of electromagnetic induction was about 314,000 meters per second.[11]
In 1871 Helmholtz moved from Heidelberg to Berlin to become a professor in physics. He became interested in electromagnetism and the Helmholtz equation is named for him. Although he did not make major contributions to this field, his student Heinrich Rudolf Hertz became famous as the first to demonstrate electromagnetic radiation. Oliver Heaviside criticised Helmholtz's electromagnetic theory because it allowed the existence of longitudinal waves. Based on work on Maxwell's equations, Heaviside pronounced that longitudinal waves could not exist in a vacuum or a homogeneous medium. Heaviside did not note, however, that longitudinal electromagnetic waves can exist at a boundary or in an enclosed space.[12]
Whoever in the pursuit of science, seeks after immediate practical utility may rest assured that he seeks in vain. --Academic Discourse (Heidelberg 1862)[13]
Other students and research associates of Helmholtz at Berlin included Max Planck, Heinrich Kayser, Eugen Goldstein, Wilhelm Wien, Arthur König, Henry Augustus Rowland, A. A. Michelson, Wilhelm Wundt, and Michael I. Pupin. Leo Koenigsberger, who studied at Berlin while Helmholtz was there, wrote the definitive biography of him in 1902.