D O C . 3 1 I D E A S A N D M E T H O D S 1 1 3
31. “Fundamental Ideas and Methods of the
Theory of Relativity, Presented in Their Development”
[after 22 January
1920][1]
Fundamental Ideas and Methods of the Theory of Relativity, Presented in Its Devel-
opment.[2]
On the occasion of 〈confirmation〉 the finding of the gravitational curvature of light
rays by the British expedition that was sent to observe the eclipse of the sun, I have
been urged by many to give a brief description to non-mathematicians of the theory
and its
development.[3]
I do this the more gladly as there is a certain danger that
the—unfortunately—rather complicated mathematical form of the theory threatens
to overshadow its simple 〈and natural〉 physical content. This mathematical form is
merely a means, while the essence of the theory is definitely the consequent execu-
tion of some 〈less taken from physical experience〉 〈general〉 simple principles to
which physical experience has led us. The theory is not at all, as many believe, the
result of daring mathematical
speculation.[4]
I. The Special Theory of Relativity
The special theory of relativity is nothing but a contradiction-free amalgamation
of the results of Maxwell-Lorentz electrodynamics and those of classical mechan-
ics. This will become clearly obvious from the following schematic sketch of its
development.
1. The Light Ether
The investigation of interference and diffraction phenomena of light during the first
half of the 19th century showed that 〈light as〉 Huygens’s opinion of the undulatory
nature of light was correct versus Newton’s theory of emission. Since physicists
then were convinced that all processes in nature have to be interpreted mechanical-
ly, they viewed light as the undulatory motion of a hypothetical substance called
“ether.” The introduction of a specific medium of light aside from other matter was
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