THE NEW KINEMATICS 139As indicated in Chapter 6, special relativity was born after a decade of gestation.
However, the crucial kinematic insights which underlie this theory dawned on its
author not more than five or six weeks before the actual completion of the paper
under discussion. We know this from the talk given by Einstein in Kyoto, in
December 1922, which also reveals that this climactic period was preceded by a
year of struggle which had led him nowhere. I quote once again from the Kyoto
address [Ol]:
'I took into consideration Fizeau's experiment, and then attempted to deal with
the problems on the assumption that Lorentz's equations concerning the electron
should hold as well in the case of our system of coordinates being defined on the
moving bodies as defined in vacuo. At any rate, at that time I felt certain of the
truth of the Maxwell-Lorentz equations in electrodynamics. All the more, it
showed to us the relations of the so-called invariance of the velocity of light that
those equations should hold also in the moving frame of reference. This invariance
of the velocity of light was, however, in conflict with the rule of addition of veloc-
ities we knew of well in mechanics.
'I felt a great difficulty to resolve the question why the two cases were in conflict
with each other. I had wasted time almost a year in fruitless considerations, with
a hope of some modification of Lorentz's idea, and at the same time I could not
but realize that it was a puzzle not easy to solve at all.
'Unexpectedly a friend of mine in Bern then helped me. That was a very beau-
tiful day when I visited him and began to talk with him as follows:
' "I have recently had a question which was difficult for me to understand. So
I came here today to bring with me a battle on the question." Trying a lot of
discussions with him, I could suddenly comprehend the matter. Next day I visited
him again and said to him without greeting: "Thank you. I've completely solved
the problem." My solution was really for the very concept of time, that is, that
time is not absolutely defined but there is an inseparable connection between time
and the signal velocity. With this conception, the foregoing extraordinary difficulty
could be thoroughly solved. Five weeks after my recognition of this, the present
theory of special relativity was completed.'
The friend in Bern was Besso, close to Einstein since the student days in Zurich,
colleague at the patent office since 1904. Thus the Kyoto address makes clear what
was the substance of the 'loyal assistance of my friend M. Besso,' to which Einstein
devoted the acknowledgment in his June paper. As to the completion of the work
in five weeks, since the paper was received by the Annalen der Physik on June
30, Einstein's total concentration on relativity followed immediately upon the
relief of his having finished three major projects in statistical physics: the paper
on the light-quantum, his thesis, and the paper on Brownian motion, completed
on March 17, April 30, and around May 10, respectively.
In 1905 Einstein's belief in 'the truth of the Maxwell-Lorentz equations' was
not unqualified, as we shall see later. It was strong enough, however, for him to
perceive the conflict between the constancy of the velocity of light (in the vacuum)