Friedrich Hasenöhrl

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Friedrich Hasenöhrl

Friedrich Hasenöhrl (born November 30, 1874 in Vienna , † October 7, 1915 in Vielgereuth , Welschtirol ) was an Austrian physicist .

life and work

Friedrich Hasenöhrl was born in Vienna as the second child of Viktor Hasenöhrl (councilor, court and court advocate) and Gabriele, née Freiin von Pidoll zu Quintenbach. He attended the Theresian Academy and passed the Matura with distinction. Already in his school days he appeared in smaller publications in the field of mathematics. In 1892 he began studying mathematics and physics and worked at the University of Vienna a . a. with Franz-Serafin Exner , Josef Stefan and Ludwig Boltzmann . During the second year of his studies he published the mathematical work "On the law of quadratic reciprocity". In 1894 he interrupted his studies for a year of voluntary military service, during which he met Hugo von Hofmannsthal . In 1896 he received his doctorate under Franz-Serafin Exner on the temperature coefficient of the dielectric constant in liquids and the Mosotti-Clausius formula .

Then Hasenöhrl turned more to theoretical physics, was awarded a doctorate in philosophy in 1897 and habilitated in 1899 with a thesis on potential theory . A stay abroad led him to Heike Kamerlingh Onnes at the University of Leiden - Boltzmann had recommended him to Kamerlingh-Onnes as an assistant upon request. In March 1899 he married Ella Brückner and received the venia legendi at the University of Vienna that same year . He quickly gained a reputation for giving excellent lectures. His students included u. a. Paul Ehrenfest and Erwin Schrödinger . In 1905 Friedrich Hasenöhrl was awarded the Haitinger Prize of the Academy of Sciences in Vienna .

First Solvay Conference 1911 - Friedrich Hasenöhrl, standing eighth from left

In 1906 Hasenöhrl became an associate professor at the Technical University in Vienna . When Ludwig Boltzmann died that same year, Hasenöhrl, who was third on the list of appointments after Wilhelm Wien and Max Planck , was his successor as professor of theoretical physics. He was a participant in the first two Solvay conferences in 1911 and 1913.

At the outbreak of the First World War , Hasenöhrl, now forty years old, volunteered for military service. After a shoulder wound in July 1915, he was awarded the 3rd Class Military Cross of Merit. As first lieutenant in the reserve and battalion commander in the 14th Infantry Regiment, he was fatally hit in the head by a shrapnel on October 7th in Vielgereuth (Folgaria) near Trento while he was leading the attack of his battalion. His early death at the age of only 41 attracted wide attention - he was considered to be the great hope of theoretical physics in Austria. The emperor personally sent the widow a condolence telegram. Today his bones rest in the Altmünster cemetery near Gmunden . In 1956 the Hasenöhrlstraße in Vienna- Favoriten was named after him.

The cavity radiation

From 1880, physicists such as Joseph John Thomson (1881), George Frederick Charles Searle (1897), Wilhelm Wien (1900), Henri Poincaré (1900), Max Abraham (1902), and Hendrik Antoon Lorentz (1904) used the term “ electromagnetic Mass "used. This expressed that the electromagnetic energy has an impulse and contributes to the mass of a body. The formula for this connection resulted (in modern notation):

In July 1904 Hasenöhrl's work On the Theory of Radiation in Moving Bodies appeared in the Annalen der Physik (after preparatory work in the Vienna meeting reports in the same year) . In it he develops the formula from the radiation pressure of electromagnetic waves

Here m is the "apparent mass of the cavity radiation", the "amount of the radiation energy contained in the resting cavity" and c the speed of light. The formula expresses that a hollow body filled with radiation has an additional, "apparent mass" due to the radiation. Hasenöhrl also concluded that this relationship is valid for every form of thermal radiation and thus for every body whose temperature is greater than 0 K. In 1905, however, Hasenöhrl was made aware of an error by Max Abraham , which meant that he had to correct the formula to:

This formula corresponds to that which was already known earlier for the electromagnetic mass. Hasenöhrl's addition to these previous achievements consisted in applying this connection to, among other things, cavity radiation and relating it to thermodynamic considerations. For this achievement, at the suggestion of Ludwig Boltzmann, he received the Haitinger Prize of the Imperial Academy of Sciences in Vienna and in 1906, despite his youth, succeeded Boltzmann as full professor. With reference to Hasenöhrl, cavity radiation was later also used by Kurd von Mosengeil (1906) and, following the latter, in a very general way within the framework of the relativity theory by Max Planck (1907).

In further work (1907, 1908) Hasenöhrl expanded his theory further and noted that the results of his new theory agreed with those of Mosengeil and Planck. However, he complained that his 1904 results were not mentioned at all by Planck (1907). However, Hasenöhrl's new work from 1907 was now also recognized by Planck (1908), who, like Hasenöhrl, noted that its results, despite different methods, agreed with those inferred from the theory of relativity.

Max Planck and Wolfgang Pauli wrote:

"F. Hasenöhrl was the first to draw attention to the fact that cavity radiation has inertia."

- Max Planck

“ The radiation in the moving cavity . This case is of historical interest, since it can be treated solely on the basis of electrodynamics, even without the theory of relativity. It is then necessary to ascribe momentum, i.e. also inert mass, to the radiant energy in motion. It is interesting that this result was found by Hasenöhrl even before the relativity theory was established. His conclusions were, however, in need of improvement on some points. A complete solution to the problem was first given by K.v. Mosengeil. "

- Wolfgang Pauli

4/3 factor

There are different explanations for the 4/3 factor in Hasenöhrl's formula. For example, Enrico Fermi and others assumed that this was to be seen analogously to the same factor for the electromagnetic mass . I.e. you not only have to take into account the energy of the radiation itself, but also the elastic stresses in the shell of the hollow body. Both together then result in a mass increase according to the relativistic formula .

In addition, Stephen Boughn and Tony Rothman (2011) and Boughn (2012) believe that Hasenöhrl could not correctly calculate the kinetic energy using the means of the time, ie without the relativistic transformation formulas. Above all, he overlooked the fact that the radiation sources lose mass during radiation, which, ironically, corresponds to an energy-mass relationship that Hasenöhrl's work should actually have demonstrated. Nevertheless, Hasenöhrl deserves recognition for the fundamental knowledge that electromagnetic energy contributes to the mass of radiating bodies.

Hasenöhrl and Einstein

The formulas for electromagnetic mass (as well as that of Hasenöhrl from July 1904) are very similar to the formula

which Albert Einstein published a few issues later, in September 1905 (see Annus mirabilis ) in the same journal in his work on the electrodynamics of moving bodies . The similarity between the two formulas was confirmed by opponents of Einstein's relativity theory (s), in particular by the representatives of National Socialist German Physics - u. a. by Philipp Lenard - used to substantiate their criticism or at least to dispute Einstein's originality.

In a work from 1921 Lenard asserted (where, by the way, he also asserted the priority of Johann Georg von Soldner and Paul Gerber ) that it was Hasenöhrls and the subsequent investigations that examined the “inertia of energy” (i.e. a combination of equivalence of heavy and inert mass and the equivalence of mass and energy ). Max von Laue (1921) replied that the inertia of electromagnetic energy had been demonstrated in particular by Poincaré (1900) and Abraham (1902) through the introduction of the electromagnetic pulse, while Hasenöhrl basically only applied this knowledge to cavity radiation. Einstein's concept of the inertia of energy, on the other hand, is much more extensive, since it is not only valid for electromagnetic energy as with the other authors, but for every possible form of energy.

See also

Publications

Wikisource: Friedrich Hasenöhrl  - Sources and full texts
Hasenöhrl's work on cavity radiation

Individual evidence

  1. ↑ Miller, Arthur I .: Albert Einstein's special theory of relativity. Emergence (1905) and early interpretation (1905-1911) . Addison-Wesley, Reading 1981, ISBN 0-201-04679-2 .
  2. ↑ Mosengeil, Kurd von: Theory of stationary radiation in a uniformly moving cavity . In: Annals of Physics . 327, No. 5, 1907, pp. 867-904.
  3. ↑ Planck, Max: On the dynamics of moving systems . In: Session reports of the Royal Prussian Academy of Sciences, Berlin . First Half Volume, No. 29, 1907, pp. 542-570.
  4. ↑ Planck, Max: Comments on the principle of action and reaction in general dynamics . In: Physikalische Zeitschrift . 9, No. 23, 1908, pp. 828-830.
  5. ↑ Planck, Max: Eight lectures on theoretical physics, given at Columbia University in the City of New York . S. Hirzel, Leipzig 1910.
  6. ↑ Pauli, Wolfgang: The theory of relativity . In: Encyclopedia of Mathematical Sciences , Volume 5.2 1921, pp. 539-776.
  7. ^ Fermi, E .: Sulla massa della radiazione in uno spazio vuoto . In: Rendiconti Lincei . 32, 1923, pp. 162-164.
  8. ↑ Mathpages: Another Derivation of Mass-Energy Equivalence . Accessed in 2011.
  9. ↑ Stephen Boughn, Tony Rothman: Hasenöhrl and the Equivalence of Mass and Energy . In: Cornell University . 2011. arxiv : 1108.2250 .
  10. ↑ Stephen Boughn: Fritz Hasenöhrl and E = mc2 . In: European Physical Journal H . 2013. arxiv : 1303.7162 . doi : 10.1140 / epjh / e2012-30061-5 .
  11. ↑ Lenard, P .: Lenard's preliminary remarks on Soldner's: About the deflection of a ray of light from its rectilinear movement by the attraction of a celestial body, which it passes close; . In: Annals of Physics . 65, 1921, pp. 593-604. doi : 10.1002 / andp.19213701503 .
  12. ↑ Laue, Mv: Reply to Mr. Lenard's preliminary remarks on Soldner's work of 1801 . In: Annals of Physics . 66, 1921, pp. 283-284. doi : 10.1002 / andp.19213712005 .

literature

Web links

Commons : Friedrich Hasenöhrl  - Collection of images, videos and audio files
personal data
SURNAME Hasenöhrl, Friedrich
ALTERNATIVE NAMES Hasenöhrl, Fritz
BRIEF DESCRIPTION Austrian physicist
DATE OF BIRTH November 30, 1874
PLACE OF BIRTH Vienna
DATE OF DEATH October 7, 1915
Place of death Vielgereuth (Folgaria), South Tyrol