Blog Ekkehard Friebe

by A. Einstein  (1909)

Im Beitrag: "Wurde Albert EINSTEIN das Opfer der Wissenschaftler seiner Zeit?"  wurde besonders hingewiesen auf folgende Veröffentlichung von Albert Einstein aus dem Jahre 1909:

"Über die Entwicklung unserer Anschauungen über das Wesen und die Konstitution der Strahlung". Diese Veröffentlichung liegt inzwischen auch in englischer Sprache im Internet vor, siehe nachstehend:

A. Einstein (Zurich):
On the development of our understanding of the nature and composition of radiation. 
Physikalische Zeitschrift, Vol. 10. No. 22, pg. 817 (1909)
(Translated by Charles A. Crummer. Footnotes by the translator. Many thanks to Dr. Walter Campbell for his clarification of the original German and to Professor Clemens Heusch for advice on appropriate wording.) 

Since one [(we)] had seen that light exhibits the phenomena of interference and diffraction, it appear[ed] that there [could] hardly be [any] doubt that light [was] to be understood as wave motion. Since light can propagate in a vacuum, one had to imagine that here there must exist a special kind of material that mediates the propagation of light waves. For the concept of the laws of propagation of light in ponderable bodies it was necessary to assume that that material, which is called the ether, exists and that it is also in the interior of ponderable bodies that the ether is a fundamental constituent which mediates the propagation of light. The existence of this ether seemed without doubt. In the first volume of the excellent textbook on physics of Chwolson appearing in 1902, one can find in the introduction of the ether the sentence concerning the ether: "The probability of [the truth of] the hypothesis of the existence of this agent comes extraordinarily close to certainty."

Arguably today, however, we must view the ether hypothesis as fundamentally flawed. It is undeniable that there is an extended body of facts pertaining to radiation which indicate that light has certain inherent qualities that put its comprehension far from either the Newtonian emission theory of light or the view of wave theory. Hence it is my opinion that the next phase of the growth of theoretical physics will bring us a theory of light which will reveal itself as a kind of mixture of wave- and emission theory. It is the purpose of the following exercise to elucidate and substantiate this position: that a fundamental change of our understanding of the nature and constitution of light is essential.

The greatest stride which theoretical optics has made since the introduction of the wave theory consists arguably of Maxwell’s ingenious discovery of the possibility that light could be understood as an electromagnetic process. This theory introduces into consideration in place of the mechanical quantities, namely deformation and velocity of the particles of the ether, the electromagnetic state of the ether and matter, and thereby reduces optical problems to electromagnetic ones. The more the electromagnetic theory advanced, the more relevant became the question as to whether electromagnetic processes lead back to mechanical ones in the background. One has got [We have gotten] used to treating the concepts of electric and magnetic field strengths, electric space charge density, and so forth as elementary concepts that do not need a mechanical interpretation. 

The basic concepts of theoretical optics were simplified by the introduction of the electromagnetic theory; the number of arbitrary hypotheses was lessened. The old question of the direction of vibration of polarized light became irrelevant. The difficulties concerning the boundary conditions at the interface between two media yielded themselves up [were resolved] on the basis of the theory. There is no more need to associate oneself with the arbitrary hypothesis of longitudinal light waves. Light pressure, measured recently, which plays so important a role in the theory of radiation arose as a consequence of the [electromagnetic] theory. I will in no wise undertake the exhaustive enumeration of the well-known attainments here, but will keep one train of thought in mind, in reference to which the electromagnetic theory coincides with the kinetic, or, better, appears to coincide.  

For both theories light waves appear fundamentally as an embodiment of states of a hypothetical medium, the ether, that exists everywhere even in the absence of radiation. Thus it was to be assumed that movements of this medium must have influence on optical and electromagnetic phenomena. The search for the laws that govern the phenomena prompts a metamorphosis in the basic understanding [of] the nature of radiation, which [metamorphosis] I suggest we consider briefly. 

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Siehe hierzu auch:

CRITICAL RESEARCHES ON GENERAL ELECTRODYNAMICS
by WALTER RITZ (INTRODUCTION)
und 
Relativistic Propagation of Light
by Wallace KANTOR (PREFACE)