232 RELATIVITY, THE GENERAL THEORYthat the public debate was closed as far as he was concerned [E7]. To a friend he
described Abraham's theory as 'a stately horse which lacks three legs' [E8].
I would have disregarded the Abraham-Einstein polemic were it not for the
fact that Abraham was a very good physicist. Einstein considered him to have the
best understanding of gravitation among his colleagues [E9]. Abraham's 1914
review of gravitation theories is excellent [Al]. When in 1913 Einstein decided to
leave Zurich for Berlin, he suggested to Zangger that Abraham be considered as
his successor [E10].* But, he added, 'I believe that they will proceed without me
because I have espoused the cause of the feared Abraham.'
Abraham had a great and unfortunate talent for creating difficulties for himself,
especially because of his biting sarcasm. Between himself and his visions stood
forever the figure of his demon: Einstein. He understood relativity but could not
find peace with it. He cannot be called a major scientist but should be remembered
nevertheless as a figure representing the tragic element which accompanies sci-
entific transition. He died in 1923 of a brain tumor. Born and von Laue jointly
wrote his obituary: 'He was an honorable opponent who fought with honest weap-
ons and who did not cover up a defeat by lamentation and nonfactual arguments.
The abstractions of Einstein were deeply repugnant to him; he loved his absolute
aether, his field equations, his rigid electron, as a youth does his first flame, whose
memories cannot be erased by later experiences. But he remained clearheaded
... his objections rested on basic convictions regarding physics ... and not on lack
of knowledge' [Bl].
To return to the developments prior to the publication of the Ein-
stein-Grossmann paper, late in 1912 Nordstrom in Helsingfors (Helsinki) came
forth with an ingenious idea [Nl]. Since both Einstein and Abraham experienced
so much trouble from the ^-dependence of c, why not try to find a theory of
gravitation in which c is independent of $ and remains a universal constant in the
familiar way? As I have noted repeatedly, Einstein correctly saw from the begin-
ning that the incorporation of gravity meant the end of the unconditional validity
of special relativity. All the same, Nordstrom's question was an eminently sensible
one for its time. It is peculiar that this line of thought had remained unexplored
(or at least had not been discussed in the scientific literature) until October 1912.
As we saw from Abraham's mishandling of Eqs. 13.1-13.4, the problem is not
quite trivial. Nordstrom's idea was to let not c but, instead, mass depend on <1>.
For general mass m, he rewrote Eq. 13.1 (which referred to unit mass) as follows:
The novelty of his theory lies in the m term. From Eq. 13.7 and the obviously
unchanged Eq. 13.3, one finds*On May 17, 1912, Einstein wrote to Wien that Abraham had become a 'convert' to his theory.