Ludwig Zehnder

Ludwig Zehnder

Ludwig Louis Albert Zehnder (born May 4, 1854 in Illnau , † March 24, 1949 in Oberhofen am Thunersee ) was a Swiss physicist .

Life

He studied mechanical engineering in Zurich from 1873 to 1875 (without Matura) . After that he had a factory for electrical appliances in Basel for 15 years. But that did not satisfy him in the long run and in 1885 he went to Berlin to study physics with Hermann von Helmholtz . While on vacation in Switzerland, he met Wilhelm Conrad Röntgen and his wife, and the couple became friends. Since Zehnder had learned from Helmholtz on request that he could not do his doctorate due to the lack of a high school diploma, he went to his friend Röntgen in Giessen (Röntgen, who did not have a high school diploma himself, was more open-minded in this regard). He received his doctorate in 1887 and became Röntgen's assistant, who moved from Gießen to Würzburg in August 1888 .

After his habilitation in physics in Basel with Hagenbach-Bischoff (mediated by Röntgen) in 1890, he became an associate professor in Freiburg i.Br. in 1893. In 1899 he went to Röntgen to Würzburg as an assistant and private lecturer and followed him to Munich in 1900 . But since he could not get an extraordinary position there, he went to the teaching institute for senior post office officials in Berlin as a physics teacher in 1904, which he remained until the outbreak of the First World War in 1914. Then he went to Zurich to the X-ray department at the Cantonal Hospital. From 1919 to 1945 he was an associate professor in Basel, where he also gave many lectures at the adult education center.

He conducted a two-year study of the refractive indices of different bodies in different aggregate states with the Jamin interferometer . But in order to be able to move the two interfering beams as far apart as desired, he constructed a new interference refractor , the Mach-Zehnder interferometer presented in August 1891 . Independently of this, Ludwig Mach had constructed a similar one, which he announced seven months later.

Zehnder was a skilled experimenter and at the end of the 19th century also dealt with high-frequency technology. In 1903 he published the Zehnder tube named after him (glow discharge tube according to L. Zehnder), which has a total of 4 electrodes. A direct voltage is applied to two distant electrodes, which does not allow a glow discharge to start. This discharge is triggered between this first pair of electrodes by a high-frequency voltage of low amplitude applied to a second pair of electrodes, the (smaller) space between which is also between the first pair of electrodes.

He was an opponent of the theory of relativity and quantum theory and developed his own mechanical theory of the universe, which he disseminated in popular science books at the end of the 19th century and which isolated him scientifically. As early as 1890, his friend Roentgen held against him in a letter his tendency to speculate without sufficient basis and repeated his warnings again and again, but Zehnder did not allow himself to be dissuaded from his attempts to develop a worldview based on classical mechanics and elastic ether and saw that in it actual motive of his occupation with physics.

Soon after Röntgen's discovery of X-rays (1895), he took early X-rays of the human body (1896), demonstrated Röntgen's discovery in public, and developed and built X-ray machines himself. In particular, he built X-ray tubes out of metal instead of glass in Zurich, which greatly reduced the radiation exposure of the medical staff.

obituary

• Friedrich Dessauer : Ludwig Zehnder 1854–1949 in: Negotiations of the Swiss Natural Research Society (SNG) 129, pp. 413–416 (1949)

Publications

• The origin of life developed from mechanical principles , Freiburg i. B. 1899
• About the development of the universe and the eternal cycle of matter ; Basel, 1885
• A new interference refractor ; In: Zeitschrift für Instrumentenkunde; 11, pp. 275-285, August 1891
• With WC Röntgen: About the influence of pressure on the refraction exponents of water, carbon disulfide, benzene, ethyl ether and some alcohols ; Ann. d Phys. 1891, new series. Volume XLIV, p. 24.
• About the nature of cathode rays and X-rays: After a lecture given in the natural Society Freiburg i. Br. On July 8, 1896 ; Munich, 1896
• The mechanics of the universe presented in its basic features ; Freiburg, 1897
• Life in space ; Tubingen, 1904
• Plan of physics ; Tübingen, Laupp, 1907
• About the nature of comets ; 1910
• The eternal cycle of the universe ; Braunschweig, Friedr. Vieweg & Son, 1914
• The structure of atoms from primordial atoms: Lecture goes 1921 ; Tübingen, Laupp, 1922
• Conclusions from the spherical form of the simplest atoms ; 1922
• The synthesis of the substance according to the latest physical, chemical and biological results ; Halle, Hofstetter, 1924
• The cyclical path of the sun as the cause of the sunspot periods ; 1928
• The development of the universe from mechanical principles , Tübingen: Laupp 1928
• A new electrical effect ; 1929
• Röntgen, Wilhelm Conrad: Professor of Physics 1845–1923 ; Wuerzburg, 1930
• The changes in basic physical concepts in the last 50 years ; Zurich, Frey, 1932
• Radiation des espaces interstellaires et processus cosmiques ; Neuchatel, Guébhard-Séverine, 1932
• The ether in the light of classical and modern times ; Tübingen, Laupp, 1933
• Personal memories of WC Röntgen and the development of the X-ray tubes ; Special copy, Basel, approx. 1933
• WC Röntgen - Letters to Ludwig Zehnder: with the articles History of his development of X-rays and Röntgen's attitude to the renaissance of classical physics by Ludwig Zehnder. Rascher & Cie. AG, Zurich / Leipzig / Stuttgart 1935.
• A new invisible radiation ; Basel, 1937
• The deepest foundations of physics and chemistry: from university lectures, 1935–38 ; Zurich, Rascher, 1938

Individual evidence

1. ↑ Brief portrait on bernensia.ch
2. ↑ fu-berlin.de: The Mach-Zehnder interferometer (diss.)
3. ^ Zehndersche Röhre Walter Nernst: Arnold Berliner, Karl Scheel (ed.), Physikalische Handwörterbuch, 1924, p. 888. (digitized version). For details see: L. Zehnder, Ann. D. Phys. 12 , 417, 1174 (1903).
4. ↑ Dessauer, obituary in the negotiations of the Swiss Naturf. Ges., 1949, p. 414
5. ↑ digitized version