3 3 2 D O C . 3 3 2 O N T H E E T H E R
332. “On the Ether”
[Einstein 1924p]
Presented 4 October 1924
Published 1924
In: Schweizerische Naturforschende Gesellschaft. Verhandlungen II. Wissenschaftlicher
Teil 105 (1924): 85–93.
When the topic being discussed is the ether, one naturally doesn’t address the
material ether of the wave theory, which is subject to the laws of Newtonian me-
chanics and in which individual points are assigned a velocity. It is my conviction
that this theoretical construct has finally played itself out since the creation of the
special theory of relativity. Rather, the topic more generally concerns those things,
conceived to be physically real, that play a role in the causal nexus of physics,
alongside ponderable matter, composed of charged elementary particles. Instead of
speaking of the “ether,” one could just as well be speaking of the “physical qualities
of space.” One could assume, however, that all subjects in physics are included in
this concept because, according to the consistent theory of fields, ponderable mat-
ter, that is the constitutive elementary particles, are conceivable as “fields” of a spe-
cial kind, or as special “states of space.” Nevertheless, one will have to concede that
such an interpretation would be premature in the present state of physics; for, all
efforts by theoretical physicists directed at this goal have failed up to now. Thus,
given the present state of things, we are in fact forced to distinguish between “mat-
ter” and “fields,” although we may also hope that later generations will supersede
this dualistic conception and will replace it with a unified one, as field theory in our
day has been attempting in vain.
It is usually accepted that Newton’s physics did not conceive of any ether, and
that the wave theory of light was the first to introduce an omnipresent medium that
co-determines physical phenomena. This is not the case, however. Newtonian me-
chanics has its “ether” in the indicated sense; albeit, it is described as “absolute
space.” In order to recognize this clearly and at the same time elaborate the ether
concept somewhat more precisely, we must go back a bit.
Let us first look at a branch of physics that makes do without the ether, namely,
Euclid’s geometry, conceived as the doctrine of the possible ways to bring practi-
cally rigid bodies into contact with one another. (Here we disregard rays of light,
which may likewise be involved in the development of the concepts and laws of
[p. 85]
[p. 86]