Friedrich Hasenöhrl

Infobox_Scientist
name = Friedrich Hasenöhrl

|300px
caption = Friedrich Hasenöhrl
birth_date = birth date|1874|11|30|mf=y
birth_place = Vienna, Austria (Austria-Hungary)
death_date = death date and age|1915|10|7|1874|11|30|mf=y
death_place = Tyrol, Austrian (Austria-Hungary)
residence = Austria-Hungary
nationality = Austro-Hungarian
field = Physicist
work_institution = University of Vienna
alma_mater = University of Vienna
doctoral_advisor = Franz S. Exner
doctoral_students = Karl Herzfeld
Erwin Schrödinger
known_for = Cavity radiation
prizes =
religion =
footnotes =

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.

=E=mc²=

Since J. J. Thomson in 1881, many physicists like Wilhelm Wien (1900), Max Abraham (1902), and Hendrik Lorentz (1904) used expressions equivalent to "m = (4/3)E/c²" 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.

In 1904 and 1905 also Hasenöhrl published two 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.

In the first paper, Hasenöhrl [F. Hasenöhrl, Wien, Sitzungen IIA, 113, 1039 (1904)] specifically associated mass via inertia with the energy concept through an equation. Hasenöhrl first concluded that $m\; =\; (8/3)E/c^2$. The same formula appeared on the page 363 in his paper [ F. Hasenöhrl, Annalen der Physik, Band 15, Heft 12, 344 (1904) [http://www.ift.uni.wroc.pl/~mwolf/Hasenohrl_1904.pdf] (the relevant part is marked on the page 363)] . The title of this paper, which in English is "On the radiation of the bodies in motion", is very similar to the title of the Einstein's paper published a year later "On the electrodynamics of the bodies in motion".

In the later paper [F. Hasenöhrl, Ann. Physik, 16, 589 (1905) [Received 26 Jan., presented 14 Mar.] ] Hasenöhrl re-calculated this result and arrived at $m\; =\; (4/3)E/c^2$ (the same expression already known from the electromagnetic mass). Hasenöhrl indicated that if the internal energy of a system consists of radiation, then, in general, the inertial mass of the system would depend upon that energy. Thus, this new Hasenöhrl calculation establishes that due to the radiant energy E contained in his system, to that inertial mass must be added an apparent mass m. Indeed, in 1914 Cunningham [E. Cunningham, The Principle of Relativity, Cambridge University Press, 1914, p. 189] showed that Hasenöhrl had made an error in that he did not include the shell. If he had included the shell in his calculations in a way consistent with relativity, the pre-factor would have been 1, so yielding $m\; =\; E/c^2$. He could not have done this, since he did not have relativistic mechanics, with which he could model the shell.

See also

* Mass–energy equivalence
* History of special relativity

Notes and References

Further reading

* Hasenöhrl,Friedrich, "Berichte der Wiener Akademie", 113, 1039 (1904).
* Hasenöhrl,Friedrich, "Annalen der Physik", 16, 589 (1905).
* 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.

External links

* [http://www.univie.ac.at/archiv/tour/17.htm Career at University of Vienna]
* [http://www.austro-hungarian-army.co.uk/10_14.html Military record]

Persondata
NAME= Hasenöhrl, Friedrich
ALTERNATIVE NAMES=
SHORT DESCRIPTION= Austrian physicist
DATE OF BIRTH= November 30,1874
PLACE OF BIRTH= Vienna, Austria-Hungary
DATE OF DEATH= October 7, 1915
PLACE OF DEATH= Tyrol, Austria-Hungary