# Woldemar Voigt

Woldemar Voigt [ vɔldəmar fo ː kt] ( born September 2, 1850 in Leipzig, † December 13, 1919 in Göttingen ) was a German physicist. He taught theoretical physics at the Georg- August University in Göttingen. Voigt is considered the founder of solid state physics.

## Life

Voigt got until 1867 to the humanist Thomas School in Leipzig. He was an avid musician, conducted Bach concertos and also published musicological treatises. But Voigt studied 1868-1870 mathematics and physics at the University of Leipzig. Here he became a member of the Leipzig University singers shaft to St. Pauli (today German singer shaft ) in winter 1868/69.

The age of 20 he took part in the Franco-German war of 1870/ 71 and in 1870 promoted to reserve officer. He served as Secondelieutenant the reserve in the Protect ( Füs. ) Regiment " Prince George " ( Royal Saxon ) No 108 and as First Lieutenant of the Landwehr Infantry in Dresden.

From 1871 to 1874 he studied at the Albertus University of Königsberg, among others, Franz Ernst Neumann, the founder of theoretical physics in Germany. In 1874 he received his doctorate in Königsberg on the elastic behavior of rock salt. After that, he was briefly a substitute teacher at St. Nicholas School in Leipzig.

From 1875 to 1883 he worked as an associate professor of physics at the Albertus University of Königsberg. In 1883 he became a full professor of Theoretical Physics at the Faculty of the Georg -August- University Göttingen and director of the Institute for Theoretical Physics, which had been re-established. Twice he was appointed Rector of the University of Gottingen.

Among his most famous pupils included Paul Drude (1863-1906), Friedrich Pockels (1865-1913), Walter Ritz (1878-1909) and Alfonso Sella ( 1865-1907 ).

He stood in a lively exchange with the most important scientists of his time as Antoine Henri Becquerel, Pietro Blaserna, Aimé Cotton, Pierre Curie, Hermann von Helmholtz, Heinrich Hertz, William Thomson, 1st Baron Kelvin, Gustav Robert Kirchhoff, Nagaoka Hantaro, Eduard Riecke, Augusto Righi, Hermann Amandus Schwarz, Arnold Sommerfeld and Wilhelm Eduard Weber.

Voigt discount stored in the University Archives of the University of Göttingen and contains a treatise on the transformation of the differential equations of motion.

The physicist Erich Mollwo was his grandson.

## Scientific work

1908 presented Woldemar Voigt with his book " magneto-and electro-optics " a comprehensive theory of magneto-optics in the framework of classical electrodynamics. He is the discoverer of the Voigt effect ( also called magnetic linear dichroism ). In 1910 he wrote the " Textbook of crystal physics," one of the fundamental works of crystallography and in particular for the piezoelectric effect. The term " tensor " was first used by him. On him the customary in crystallography Voigt notation goes back, a practical notation for symmetric tensors.

A Voigt profile is the convolution of a Gaussian curve with a Lorentz curve.

From 1878, Voigt was working on the basics and on the expansion of the hitherto much of Fresnel embossed theoretical optics. In the year of its introduction into the Göttingen Society of Sciences, 1883, he tried his hand at a consistent further development of a theory of light in vacuum on the basis of an elastic light ether. Later he gave mechanical model concepts to a large extent and sought a phenomenological theory. Their final form is included in Volume II of his " Compendium of theoretical physics."

Since about 1886 Voigt worked on the theory of the optics of moving bodies, then a current research area in advance of the modern theory of relativity, in which many physicists tried to detect movements against the "ether". He led the first transformation equations of the type of Lorentz transformation ago, the Voigt - transformations, and demonstrated the invariance of the wave equation under this transformation (see History of the Lorentz transformation # Voigt transformation). His starting point had been a partial differential equation for transverse waves and a general form of the Galilean transformation. Voigt's transformation, however, differs by a scale factor of the ordinary Lorentz transformation. As in 1905, in particular Henri Poincaré and Albert Einstein showed only the Lorentz transformation is symmetric and satisfies the principle of relativity.

As HA Lorentz in a footnote on page 198 of his book "Theory of Electrons " pointed out, Voigt has thus anticipated the Lorentz transformation. It is also known that Voigt had corresponded with Lorentz in the years 1887 and 1888 because of the Michelson experiment. However, Lorentz explained that he had not known Voigt's work from 1887, before he wrote his own work on it. In the important journal Annals of Physics Voigt's work was cited in an article on Doppler 's principle before the advent of modern relativity theory nor in 1903. Whether Larmor had known the Voigt transformation is uncertain. From the creators of the modern theory of relativity Voigt's pioneering work is mentioned ( for example, in space and time) except by Lorentz only by Hermann Minkowski.

In the years 1887 and 1888 Voigt brought an extensive " theory of light for moving media ", which was published in two versions. On page 235 of the first publication he ruled, first, that the Michelson - Morley experiment necessarily a negative result term " must", regardless of whether the light-ether will be carried by the earth or not. In a footnote on page 390 of the second publication Voigt revised this statement, however, and writes: " However, there is still assumed that the ether does not suppose in part the motion of the Earth, which does not seem to be correct according to the latest observations of H. Michelson. The concerns which I had formerly against such an interpretation of the observations of Mr. Michelson 's, I can not maintain as erroneously against epistolary objections of Mr. HA Loren (t ) z ".

## Awards and Affiliations

## Writings

Other publications by Woldemar Voigt:

- The relativity of light
- John J. O'Connor, Edmund F. Robertson ( University of St. Andrews, UK, 1996): A Brief History of Special Relativity.
- Publications Voigts on works by JS Bach and others