5 8 D O C U M E N T 3 1 J A N U A R Y 1 9 2 1
German scientists and at the same time to believe that Germany and all things Ger-
man are utterly and hopelessly bad.
With regard to Das Relativitätsprinzip: the copy which you sent me was pub-
lished in 1915 and contains no reference to your later work on the allgemeine rela-
tivitätstheorie. Several of the papers are widely known among English scientists
and there are two quite good books—Silberstein and Cunningham on the special
theory.[4]
I do not think that one could put the book forward as a presentation of the
theory as it stands today. However there is one point on which I am not clear. I men-
tioned the book in correspondence with Dr E. T. Gumbel, whom I think you
know,[5]
and he says that there is quite a lot in it about the general theory. Has a
later edition been published? I have asked my English booksellers but they do not
know of
any.[6]
You may be interested to hear of some work which I have been doing on the the-
ory. It will shortly be published by the Royal Society of
London.[7]
I have consid-
ered the equations of the gravitational and electromagnetic fields and find that they
have an exact
solution[8]
where
where = constant of gravitation, c = velocity of light in absence of gravitation. m,
are constants of integration which can be identified with the mass and charge of
the particle. I do not think it is more than a coincidence but has its infinity value,
namely 1, in the case of an electron when r is of order
You will remember that at the end of one of your papers in the Sitzungsberichte
you speak of the Quantum hypothesis applying to gravitation as well as, to electro-
magnetic phenomena.[9] It appears to me that we neglect radiation and introduce
the quantum hypothesis and that it is not unlikely that these two are equivalent: that
the quantised orbits are those which correspond to no radiation. The no radiation
orbits are those which correspond to the periodic solutions of our differential equa-
tions. The above mentioned work enables me to treat the problem of the motion of
an electron in the field of say a hydrogen nucleus to the approximation which ne-
glects the disturbance of the field due to the mass of the electron. It leads to an
equation of orbits of the type
ds2
1
--dr2
-
– r2d 2 – r2sin2 d 2 c2dt2 + – =
2 m
c2r
2
c4r2
-+–=--------------------1
10–13.
d
du
2
a0u4 a1u3 a2u2 a3u a4 + + + + =