D.-E.Liebscher (Astrophysikalisches Observatorium Potsdam)
P.Brosche (Sternwarte der Universität Bonn)
Three traps in stellar aberration
The effect of aberration seems to be one of the simplest phenomena
in astronomical observations. Nevertheless, it has a long
and pertaining history of
misunderstanding and wrong interpretation.
In the time just before the advent of the theory of relativity,
aberration and drag of the aether (as found in Michelson's
experiment) are interpreted as contradiction. This contradiction
vanishes with the theory of relativity.
More obstinate is the misunderstanding that the aberration
depends on the relative velocity of source and observer.
In the twenties, some physicists and astronomers believed that the
consequences of such a relativity, wrongly supposed but never found,
would constitute a firm argument against Einstein's theory
(Hayn, Tomaschek,
Osten, v.Brunn, Courvoisier, Mohorovicic).
History forgot their argument, but it is difficult to find a correct
explanation of their error (Emden).
Instead, the subject is forgotten, and one can conjecture that it is
because of the political side of the argument.
This attitude takes its revenge: Misunderstandings
are still handed down from
textbook to textbook.
- Aberration is the difference between the apparent positions
found by observers in relative motion.
- The model of streaming particles is used in the simplest
explanation. It falls in contradiction to the then natural
assumption that the isotropic emission velocity of a source must
be composed with their own velocity.
In contrast to this expectation, the emission velocity is not
composed with the velocity of the source.
- The mechanistic wave picture correctly describes the
lack of this composition, but the wave-front normals
do not show aberration.
- Fresnel overcame this difficulty because conventional
telescopes did not state the direction of wave fronts but only
the direction of parts of a wave (i.e. wave groups, signals)
which move like particles due to their locality.
- There is no aberration of wave fronts without relativity of
simultaneity, i.e. without Einstein's theory of relativity.
- It was Einstein's theory of relativity that reminded us
that only relative velocities may lead to measurable effects.
However, that does not imply that aberration answers
the relative motion between source and observer. There is no
stellar aberration due to the velocity of the source (if the emission
event is given).
Bradley's explanation is found everywhere, beginning with
- Bradley,J. (1728): An account of a new discovered motion of fixed stars,
Phil.Trans.London 35, 637, 1729,
reprinted in W.Magie ed., A source book of physics, Cambridge
MS, Harvard 1935
The retardation in the particle picture is, for instance,
noticed and tested in
- Herschel,J.F.W. (1844): Schreiben an den Herausgeber,
Astron.Nachr. 22, 249-254 (520).
- Zurhellen,W. (1914):
Zur Frage der astronomischen Kriterien
für die Konstanz der Lichtgeschwindigkeit,
Astron.Nachr. 198, 1-10 (4729).
The absence of wave-front aberration (in aether theories) is noticed in
- Fresnel,A. (1814):
Lettre à son frère Léonor, 4.Juillet 1814,
Oeuvres complètes 2, 820-824, Paris, Imprimerie impériale 1868.
- Stokes,G.G. (1845):
On the aberration of light,
Phil.Mag.(3) 27, 9-15.
Fresnel's explanation is found more rarely, beginning with
- Fresnel,A. (1818):
Sur l'influence du mouvement de terre dans quelques phénomènes
d'optique,
Oeuvres complètes 2, 627, Paris, Imprimerie impériale 1868.
The absence of the aberration of wave-front normals is
overlooked, for instance, by
- Joos,G. (1956):
Lehrbuch der theoretischen Physik, Leipzig, Geest & Portig, 9.Aufl.
- Liebscher,D.-E. (1973):
Theoretische Physik, Berlin, Akademie-Verlag, S. 201, erste Formel.
- Herlt,E., Salié,N. (1978):
Spezielle Relativitätstheorie, Berlin, Akademie-Verlag.
- Ruder,H., Ruder,M. (1994):
Die Spezielle Relativitätstheorie, Vieweg Braunschweig.
- Goy,F. (1996):
Aberration and the question of equivalence of
some ether theories to special relativity,
Found.Phys.Lett. 9, 165-174.
The aberration of wave-front normals requires a relativity
of simultaneity. This can be found in
- Drude,P. (1900):
Lehrbuch der Optik, Leipzig, Hirzel.
- Sommerfeld,A. (1959):
Vorlesungen, IV. Optik, 2.Aufl., Leipzig, Geest & Portig.
- Bohm,D. (1965):
The special theory of relativity, W.A.Benjamin.
- Führt,P. (1970):
Fundamental principles
of modern theoretical physics, London, Pergamon Press.
- Atwater,H.A. (1974):
Non-simultaneity in the aberration of starlight,
Amer.J.Phys. 42, 1022-1024.
The aberration should be a matter of relative velocity
betweeen observer and source. This error is, for instance, outspoken
seriously or by neglect in
- v.Laue,M. (1911):
Das Relativitätsprinzip, Braunschweig, Vieweg.
- Einstein,A. (1916):
Über spezielle und allgemeine
Relativitätstheorie, Braunschweig, Vieweg.
- Pauli,W. (1921):
Relativitätstheorie,
Enzyklopädie der mathematischen Wissenschaften V/2, Berlin, Springer,
S. 563.
- Melcher,H. (1974):
Relativitätstheorie, Berlin,
Deutscher Verlag der Wissenschaften.
- Toretti,R. (1984):
Relativity and Geometry, Oxford, Pergamon.
- Treder,H.J. (1985):
Aberration und Rotation des Kosmos,
Ann.d.Physik 42, 71-72.
An active aberration is expected (erroneously) by
- Camerer,J.W. (1797):
Über die tägliche Aberration der Gestirne,
Astronomisches Jahrbuch für das Jahr 1798, 139-142.
- Houzeau,J.C. (1844):
D'un nouvel effet de l'aberration de la lumière
particulier aux étoiles doubles qui possèdent un
mouvement propre,
Astron.Nachr. 21, 241-248 (496), 273-278 (498).
No active aberration is observed. This is (correctly) stated by
- Nyrén,M. (1888):
Zur Aberration der Fixsterne,
Bull.Acad.Imp.St.Petersburg 32, 402-412.
- Seeliger,H. (1884):
Ueber die Aberration der Fixsterne,
Astron.Nachr. 109, 275-280 (2610).
The absence of active aberration is (erroneously) believed to be an
argument against the theory of relativity by
- Hayn,A.N. (1920):
Didaktisches zur Aberration II,
Astron.Nachr. 212, 81-88 (5070).
- Tomaschek,R. (1925):
Über die Aberration,
Z.Physik 32, 397-402.
- Osten,H. (1925):
Aberration und Relativität,
Astron.Nachr. 224, 66-67 (Nr.5356).
- Mohorovicic,St. (1928):
Optik bewegter Körper,
in: E.Gehrke,
Handbuch der physikalischen Optik 2, 917 ff., Leipzig, J.A.Barth.
- Marmet,P. (1996):
Stellar aberration and Einstein's relativity,
Physics Essays 9, 96-99.
- Spencer,D.E., Shams,U.Y. (1996):
Stellar aberration and the postulates on the velocity of light,
Physics Essays 9, 476-483.
That no active aberration is to be expected, is (correctly)
stated by
- Herschel,J.F.W. (1844):
Schreiben an den Herausgeber,
Astron.Nachr. 22, 249-254 (520).
- Emden,R. (1926):
Aberration und Relativitätstheorie,
Die Naturwissenschaften 14, 327-335.
- Fock,V.A. (1960):
Theorie von Raum-Zeit und Gravitation, Berlin, Akademie-Verlag.
- Liebert,J. (1995):
Die Aberration. Ein Gedankenexperiment zum Aberrationseffekt,
Die Sterne 71, 76-83.
Here you will find the
Poster.
|
D.-E. Liebscher
|
|
Last updated: February 26, 1998