# Friedrich Hasenöhrl: Wikis

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# Encyclopedia

Friedrich Hasenöhrl

Friedrich Hasenöhrl
Born November 30, 1874
Vienna, Austria (Austria-Hungary)
Died October 7, 1915 (aged 40)
Tyrol, Austria (Austria-Hungary)
Residence Austria-Hungary
Nationality Austro-Hungarian
Fields Physicist
Institutions University of Vienna
Alma mater University of Vienna
Doctoral advisor Franz S. Exner
Doctoral students Karl Herzfeld
Erwin Schrödinger
Known for Cavity radiation

Friedrich Hasenöhrl (November 30, 1874 - October 7, 1915), was an Austro-Hungarian physicist.

Friedrich Hasenöhrl was born in Vienna, Austria (Austria-Hungary) in 1874. His father was a lawyer and his mother belonged to a prominent aristocratic family. After his elementary education, he studied natural science and mathematics at the University of Vienna under Stephan and Boltzmann. He worked under H. A. Lorentz in Leiden at the low temperature laboratory.

In 1907 he became Boltzmann's successor at the University of Vienna as the head of the Department of Theoretical Physics. He had a number of illustrious pupils there and had an especially significant impact on Erwin Schrödinger, who later won the Nobel Prize for Physics for his contributions to Quantum Mechanics.

When the war broke out in 1914, he volunteered at once into the Austria-Hungarian army. He fought as Oberleutnant against the Italians in Tyrol. He was wounded, recovered and returned to the front. He was then killed by a grenade in an attack on Mount Plaut on October 7, 1915 at the age of 40.

## Contents

Since J. J. Thomson in 1881, many physicists like Wilhelm Wien (1900), Max Abraham (1902), and Hendrik Lorentz (1904) used equations equivalent to

$m_{em}=\frac{4}{3} \cdot \frac{E_{em}}{c^2}$

for the so called "electromagnetic mass", which expresses how much electromagnetic energy contributes to the mass of bodies. And Henri Poincaré (1900) implicitly used the expression m=E/c2 for the mass of electromagnetic energy.

Following this line of thought, Hasenöhrl (1904, 1905) published several papers on the inertia of a cavity containing radiation. This was an entirely classical derivation (no use of special relativity) and used Maxwell's equation for the pressure of light. Hasenöhrl specifically associated the "apparent" mass via inertia with the energy concept through the equation

$m=\frac{8}{3} \cdot \frac{h \, \varepsilon_0}{c^2}$,

where hε0 is the radiation energy. He also concluded that this result is valid for all radiating bodies, i.e. for all bodies whose temperature is > 0°K. For this result Hasenöhrl was awarded the Haitinger prize of the Austrian Academy of Sciences. However, it was shown by Abraham that Hasenöhrl's calculation for the apparent mass was incorrect, so he published another paper in 1905, where he presented Abraham's criticism and corrected his formula to:

$m=\frac{4}{3} \cdot \frac{h \, \varepsilon_0}{c^2}$

This was the same relation (as Hasenöhrl noted himself) which was already known from the electromagnetic mass. If he had included the shell in his calculations in a way consistent with relativity, the pre-factor of 4/3 would have been 1, so yielding m = E / c2. He could not have done this, since he did not have relativistic mechanics, with which he could model the shell.

Hasenöhrl's results (concerning apparent mass and thermodynamics) by using cavity radiation was further elaborated and criticized by Kurd von Mosengeil (1906/7) who already incorporated Albert Einstein's theory of relativity in his work. A broad outline of relativistic thermodynamics and mass-energy equivalence using cavity radiation was given by Max Planck in 1907.[1][2][3]

In some additional papers (1907, 1908) Hasenöhrl elaborated further on his 1904-work and concluded that his new results were now in accordance to the theories of Mosengeil and Planck. However, he complained about the fact that Planck (1907) did not mention his earlier 1904-results (like the dependency of apparent mass on temperature). Eventually, in 1908 Planck wrote that the results of Hasenöhrl's new approach from 1907 were indeed equivalent to those of relativity.[4]

## Hasenöhrl and Einstein

The formulas for electromagnetic mass (like those of Hasenöhrl's) were similar to the famous equation for mass–energy equivalence:

$\displaystyle{E=mc^2}$

published by Albert Einstein in September 1905 in the Annalen der Physik —a few editions after Hasenöhrl published his results on cavity radiation. The similarity between those formulas led some critics of Einstein, up until the 1930's, to claim that he plagiarized the formula from Hasenöhrl, often in connection with the antisemitic Deutsche Physik.

As an example, Phillip Lenard published a paper in 1921 in which he gave priority for "E=mc²" to Hasenöhrl (Lenard also gave credit to Johann Georg von Soldner and Paul Gerber in relation to some effects of general relativity).[5] However, Max von Laue quickly rebutted those claims by saying that the inertia of electromagnetic energy was long known before Hasenöhrl, especially by the works of Henri Poincaré (1900) and Max Abraham (1902), while Hasenöhrl only used their results for his calculation on cavity radiation. Laue continued by saying that credit for establishing the inertia of all forms of energy (the real mass-energy equivalence) goes to Einstein, who was also the first to understand the deep implications of that equivalence in relation to relativity. [6]

## Publications

Hasenöhrl's papers on cavity radiation and thermodynamics

## Notes and References

1. ^ Miller, Arthur I. (1981). Albert Einstein’s special theory of relativity. Emergence (1905) and early interpretation (1905–1911). Reading: Addison–Wesley. pp. 359–374. ISBN 0-201-04679-2.
2. ^ Mosengeil, Kurd von (1907). "Theorie der stationären Strahlung in einem gleichförmich bewegten Hohlraum". Annalen der Physik 327 (5): 867–904.
3. ^ Planck, Max (1907). "Zur Dynamik bewegter Systeme". Sitzungsberichte der Königlich-Preussischen Akademie der Wissenschaften, Berlin Erster Halbband (29): 542–570.
4. ^ Planck, Max (1908). " Bemerkungen zum Prinzip der Aktion und Reaktion in der allgemeinen Dynamik". Physikalische Zeitschrift 9 (23): 828–830.
5. ^ Lenard, P. (1921). "Vorbemerkung Lenards zu Soldners: Über die Ablenkung eines Lichtstrahls von seiner geradlinigen Bewegung durch die Attraktion eines Weltkörpers, an welchem er nahe vorbeigeht;". Annalen der Physik 65: 593–604. doi:10.1002/andp.19213701503.
6. ^ Laue, M.v. (1921). "Erwiderung auf Hrn. Lenards Vorbemerkungen zur Soldnerschen Arbeit von 1801". Annalen der Physik 66: 283–284. doi:10.1002/andp.19213712005.

• Lenard, Philipp, Great Men of Science. Translated from the second German edition, G. Bell and sons, London (1950) ISBN 083691614X
• Moore, Walter "Schrödinger: Life and Thought" University of Cambridge (1989) ISBN 0521437679.