152 RELATIVITY, THE SPECIAL THEORYwhere xl} x 2 , x 3 denote the spatial variables. The most important remarks made
in this colloquium were that the electromagnetic potentials as well as the charge-
current densities are vectors with respect to the Lorentz group, while the electro-
magnetic field strengths form a second-rank tensor (or a Traktor, as Minkowski
then called it). Soon thereafter Minkowski published a detailed paper [M5] in
which for the first time the Maxwell-Lorentz equations are presented in their
modern tensor form, the equations of point mechanics are given a similar treat-
ment, and the inadequacy of the Newtonian gravitation theory from the relativistic
point of view is discussed. Terms such as spacelike vector, timelike vector, light
cone, and world line stem from this paper.
Thus began the enormous formal simplification of special relativity. Initially,
Einstein was not impressed and regarded the transcriptions of his theory into ten-
sor form as 'uberfliissige Gelehrsamkeit,' (superfluous learnedness).* However, in
1912 he adopted tensor methods and in 1916 acknowledged his indebtedness to
Minkowski for having greatly facilitated the transition from special to general
relativity [E20].
Minkowski's semitechnical report on these matters, the 'space and time' lecture
given in Cologne in 1908, began with these words:** 'The views of space and time
which I wish to lay before you have sprung from the soil of experimental physics,
and therein lies their strength. They are radical. Henceforth space by itself, and
time by itself, are doomed to fade away into mere shadows, and only a kind of
union of the two will preserve an independent reality.' He ended as follows: 'The
validity without exception of the world postulate [i.e., the relativity postulates], I
like to think, is the true nucleus of an electromagnetic image of the world, which,
discovered by Lorentz, and further revealed by Einstein, now lies open in the full
light of day' [M6]. It is hardly surprising that these opening and closing state-
ments caused a tremendous stir among his listeners, though probably few of them
followed the lucid remarks he made in the body of the speech. Minkowski did not
live to see his lecture appear in print. In January 1909 he died of appendicitis.
Hilbert called him 'a gift of heaven' when he spoke in his memory [H2].
The rapid growth of Einstein's reputation in scientific circles dates from about
- In July 1909 the University of Geneva conferred the title of doctor honoris
causa 'a Monsieur Einstein, Expert du Bureau Federal de la Propriete intellec-
tuelle.' I do not know what citation accompanied this degree. However, Charles
Guye, then professor of experimental physics at Geneva, must have had a hand
in this. Since Guye's interests centered largely on the velocity dependence of beta-
ray energies, it is probable that Einstein received this first of many honors because
of relativity.
- Einstein told this to V. Bargmann, whom I thank for in turn relating it to me.
**The text of this colloquium was prepared for publication by Sommerfeld. It appeared in 1915
[M4j, long after Minkowski's death. This paper is not included in Minkowski collected works (pub-
lished in 1911) [M5].