Hermann von Helmholtz

Hermann Ludwig Ferdinand von Helmholtz ( August 31, 1821 in Potsdam, † September 8, 1894 in Charlottenburg ) was a German physiologist and physicist. As a polymath, he was one of the most versatile natural scientists of his time and also Chancellor of physics was called. Since 1995, the Helmholtz Association of German Research Centres, a network of large non-university research centers, named after Hermann von Helmholtz.

Life

Hermann von Helmholtz was the son of August Ferdinand Julius Helmholtz and Caroline Penne ( 1797-1854 ). He attended the High School " Big city school " in Potsdam, where his father worked as a director. To his younger brother Otto, who was an engineer, he had all his life a close connection.

Even the seventeen Helmholtz was interested in physics. The natural sciences, especially physics, however, were regarded as subjects of starving art. Therefore, Helmholtz studied medicine at 1838 Medicinisch - surgical Friedrich- Wilhelm Institute in Berlin. Helmholtz received his doctorate in 1842 with a dissertation in a microscopic anatomy and was a year later, an assistant physician at the Charité. He was an above average graduate, but at first there was little point to an academic career. From 1843 Helmholtz served in Potsdam, as the study included the commitment to a subsequent eight years of military service in the institution of his choice. In 1846 he was a military surgeon in the Royal Regiment.

In 1848 he was released early from military service on the recommendation of Alexander von Humboldt and first taught anatomy at the Berlin Academy of Art. In 1848 at the Helmholtz in succession by Ernst Wilhelm bridge to the chair of physiology in Berlin. Helmholtz was shortly after his marriage ( on 26 August 1849 Olga von Velten ( 1827-1859 ) ) more focused on his work and cared less about the political events in 1848 (1848 Revolution) - unlike, say, his colleague Emil Heinrich Du Bois -Reymond.

In 1849 he was appointed as professor of physiology and pathology to Königsberg. However, his wife suffering from tuberculosis could not stand the harsh climate in East Prussia. Through the mediation of Alexander von Humboldt in 1851 Helmholtz moved to Bonn to there to accept the vacant Chair of Physiology. From 1858 Helmholtz adopted a well-paid professor in Heidelberg, where from 1858 to 1863 Wilhelm Wundt was his assistant.

In December 1859 his wife, who left him with two small children died. On May 16, 1861 Helmholtz married his second wife, Anna von Mohl ( 1834-1899 ). From two marriages a total of five children ( three sons and two daughters ) were born. A son from his first marriage was the railroad engineer Richard von Helmholtz ( 1852-1934 ). 1870 Helmholtz was appointed a member of the Prussian Academy of Sciences.

In 1870, the Professor of Physics at the Friedrich- Wilhelms- University of Berlin, Heinrich Gustav Magnus died. Helmholtz was offered the professorship. Since he had dealt in recent years with more physics than physiology, he accepted the offer. Helmholtz was even then one of the largest, most versatile thinkers and researchers in Germany. With great effort he was adopted by the educated population of Heidelberg.

From 1879 to 1883, the young Heinrich Hertz worked in Berlin at Helmholtz. In 1883 Helmholtz was raised to the peerage, 1877/78 he served as rector of the university. In 1882 he was, next to Wilhelm Foerster and Werner von Siemens, one of the initiators for the subsequent establishment of the Physical- Technical Institute. The many innovations in electrical engineering, the measurement of quantities of electricity needed a uniform standardization. Helmholtz in 1888 became the first President of the Physikalisch -Technische Reich Institute in Charlottenburg.

Many tragedies darkened the lives of Helmholtz in the last phase: the death of his son Robert ( 1889), the friend Werner von Siemens (1892 ) (also father to his daughter Ellen ), the student Heinrich Hertz ( 1894), colleague August Kundt ( 1894). On September 8, 1894 Helmholtz, died at a second stroke. He was laid to rest in a grave of honor point of the city of Berlin in the Dept. AT -52 in the cemetery Wannsee, linden street. The design of the grave complex dates from the sculptor Adolf von Hildebrand.

Research

Already in 1842 pointed Helmholtz in his doctoral thesis the origin of the nerve fibers from ganglion cells after. At the start of his scientific work reached by Helmholtz studies on fermentation, putrefaction and the heat production of living beings (which he mainly attributed to muscular work ) to the formulation of the law of conservation of energy.

From October 1845 Helmholtz came with the physics professor Heinrich Gustav Magnus in contact. For physicists group under Magnus then belonged Ernst Wilhelm Bridge ( physicians ), Emil Du Bois- Reymond ( physicians ), Werner von Siemens ( lieutenant of artillery ), Johann Georg Halske ( mechanic ). 1845 founded the group, the Physical Society of Berlin and a magazine entitled "Progress of Physics". 1846 taught Helmholtz, during his time as a military doctor in Potsdam, a laboratory and wrote an experimental work "On the metabolic consumption of muscle actions ."

In his book, On the conservation of force ( 1847) he formulated the law of energy conservation in more detail than Julius Robert von Mayer had done it in 1842, and contributed significantly to the recognition of this principle in initially very controversial. The allegations of plagiarism of many of his contemporaries, he fended off by saying that he did not know the five years earlier published work of Mayer. By applying the conservation of energy on living organisms Helmholtz contradicted the vitalist who accepted a vital force as a basic force of life.

As of 1849, Helmholtz, a professor of physiology and pathology in Königsberg, in his research intensively the sense organs eye and ear. Here he developed the ophthalmoscope for observing the fundus. Furthermore, Helmholtz developed an apparatus to measure the nerve of frogs.

"I have found that a measurable time elapses while the stimulus, which exerts an instantaneous electric current to the Hüftgeflecht a frog, propagates up to the entrance of the femoral nerve in the calf muscle. For large frogs, whose nerves were between 50 and 60 millimeters long, and which I had stored at 2-6 degrees Celsius, while the temperature of the observation room was 11-15 degrees, this time period was from 0.0014 to 0.0020 of a second. "

Building on these physiological research, he dealt with the physiology of hearing and seeing. He developed a mathematical theory to explain the timbre by harmonics, the resonance theory of hearing and, based on the doctrine of the Sensations of Tone as a Physiological Basis for the Theory of Music ( 1863). Helped the Helmholtz established by Thomas Young additive theory of color vision to break through, which he showed that three primary colors ( Young had six needed ) to produce all other meet (three-color theory). He invented the ophthalmoscope in 1850 ( ophthalmoscope ) to examine the fundus, 1851, the keratometer to determine the radii of curvature of the cornea and 1857 Telestereoskop.

From 1858 to Helmholtz in Heidelberg dealt with medical basics of optical and acoustic physiology, with questions of theoretical physics ( hydrodynamics and electrodynamics), with mathematical questions ( geometry). Helmholtz was also interested in the relationships of physics, physiology, psychology and aesthetics.

With the formation of the vortex sets (1858 and 1868 ) on the behavior and motion of vortices in inviscid fluids Helmholtz provided important foundations of hydrodynamics. In studies of electrodynamics Helmholtz sought a compromise between the theories of Franz Ernst Neumann and James Clerk Maxwell. Mathematically elaborated studies on natural phenomena such as hurricanes, thunderstorms or glaciers were found to Helmholtz founder of scientific meteorology.

In epistemological discussions, Helmholtz sat apart with problems of counting and measuring, as well as the generality of the principle of least action. On the basis of its optical and acoustic investigations he modified the classical perception concept, leaning in contrast to Kant, the existence of solid forms of intuition from, and therefore thought it possible to make non-Euclidean geometries vividly. The four- phase model of the creative process goes back to observations of Helmholtz.

In the last volume of his 1856-67 work published Handbook of Physiological Optics, he figured, what is the role of the unconscious conclusion for perception.

One of the most outstanding achievements of Helmholtz later, the three treatises on the "Thermodynamics of chemical processes " ( 1882/1883 ). Here Helmholtz applied the laws of thermodynamics on the electrochemistry. He introduced the concept of free energy. Due to the free energy, one can predict whether a chemical reaction according to the laws of thermodynamics ( Gibbs - Helmholtz equation ) is possible.

Helmholtz coil

→ Main article: Helmholtz coil

The Helmholtz coil is a commonly used, simple geometry to produce a nearly uniform magnetic field accessible on all sides. The arrangement consists of two coaxially at a distance equal to the radius of its opposite ring coils with the same number of turns.

If the individual coils are current flowing through it in the same direction, one obtains a large area with constant field strength. When the coils traversed in opposite directions, one obtains an almost constant field gradient in the inner region.

Helmholtz resonator

→ Main article: Helmholtz resonator

A sound used for analysis of acoustic resonator ( oscillatory system which begins to oscillate at the excitation at the natural frequency ) is made of an air-filled hollow sphere with an opening. The Helmholtz resonator is used today many ways, eg at the resonant charging in Porsche engines to increase performance and reduce fuel consumption.

Helmholtz differential equation

→ Main article: Helmholtz differential equation

As Helmholtz equation is the general partial differential equation

Referred to. is the Laplace operator.

In electrodynamics, the Helmholtz equation from the wave equation for the vector potential, assuming harmonic time dependence:

Superposition principle according to Helmholtz

In a network are only linear resistors and independent sources ( power sources and / or voltage sources) are present, the following relation holds:

" The effect of ( current or voltage) at any point of the network, which is caused by all the sources is equal to the sum of the effects of each single source, at the same time when the remaining sources are replaced by their ideal internal resistances. " Ideal voltage sources are therefore short-circuit, ideal current sources are to be replaced by an open circuit. "

The superposition principle according to Helmholtz is only valid for currents and voltages, not for services!

Helmholtz as a namesake

According to Hermann von Helmholtz are named:

• The Helmholtz Medal of the Prussian Academy of Sciences
• The Helmholtz Medal of the German Society of Acoustics
• Since 1995, the Helmholtz Association of German Research Centres
• Several high schools, see Helmholtz -Gymnasium
• Since 1935, the lunar crater Helmholtz
• Since 1973, the Mars crater Helmholtz

There was a proposal to name the physical unit of the electric double layer Helmholtz moment.

Exhibition

Hermann von Helmholtz - a pioneer of psychology. Exhibition ( since 10 December 2012) in the Adolf- Würth - Center for the History of Psychology in Würzburg.

Writings

• On the conservation of force. Reimer, Berlin 1847 ( digitized and full text in German Text Archive )
• Concerning the interaction of the forces of nature and relating thereto latest Ermittelungen of physics: a popular - scientific lecture, held on February 7, 1854 Grafe & Dead Ringers, Königsberg in 1854 ( at the HU Berlin: Full text )
• Theory of air oscillations in tubes with open ends. In: Journal of Pure and Applied Mathematics. 57 (1860 ), No. 1, pp. 1-72. ( Digitized and full text in German Text Archive )
• Held speech at the commencement of Rectorats at the Friedrich- Wilhelms- University in Berlin on October 15, 1877, August Hirschwald, Berlin 1878 ( at the HU Berlin: Full text ) - Over the academic freedom of universities in Germany
• Writings on epistemology, commented by Moritz Schlick and Paul Hertz, ed. by Ecke Bonk, Vienna; New York: Springer 1998, ISBN 3-211-82770-6.
• About the Conservation of Energy (1847 ) / About vortices (1858 ), ed. A. Wangerin, 2nd edition. Reprint of the ed Leipzig, Engelmann, tuna; German, Frankfurt am Main 1996, ISBN 3-8171-3001-5.
• On the history of the principle of least action, Proceedings of the Royal Prussian Academy of Sciences in Berlin 14, 1887 ( at the HU Berlin: Full text )
• Essays on Philosophy and Geometry, ed and inlaid. by Sabine S. Gehlhaar, Cuxhaven: Junghans 1987, ISBN 3-926848-00-6.
• The doctrine of the sensations of tone as a physiological basis for the theory of music, Vieweg, Braunschweig, 1863, reprint: Minerva -Verlag, Frankfurt / Main 1981, ISBN 3-8102-0715-2 ( excerpt )
• Description of an ophthalmoscope for examination of the retina in the living eye, unveränd. Nachdr d ed Leipzig, JA Barth, 1910, Leipzig 1968.
• Physiological Optics ( Vol. 3) ( JPC Southall, Trans ) Rochester, NY: Optical Society of America, 1925/1909
• Thinking in terms of natural science, unveränd. repro graf. Nachdr University Press, Darmstadt 1968.
• The facts in perception / Counting and measuring considered epistemologically, unveränd. fotomechan. Nachdr Scientific. Book Company, Darmstadt 1959.
• Lectures and speeches, Volume 1, Vieweg, Braunschweig, 1896, 4th ed
• Speeches, Vol 2, Vieweg, Braunschweig, 1896, 4th ed
• Handbook of Physiological Optics, L. Voss, Leipzig 1867