He did, of course, not know that a few weeks earlier someone else had inde-
pendently noted the group properties of Lorentz transformations and had derived
Eqs. 6.19-6.21 by an almost identical argument.
I shall return later to the efforts by Lorentz in 1904 and by Poincare in 1905
to give a theory of the electron. However, I believe I have presented at this point
all the evidence that bears on the role of Lorentz and of Poincare in the develop-
ment of relativity theory. I shall now let their case rest until the discussion of
Einstein's first two papers on the subject has been completed. Thereafter an
attempt will be made to compare the contributions of all three men.
As a last step preparatory to the account of Einstein's discovery of relativity, I
should like to mention what little we know about his thoughts on the subject prior
to 1905.
6d. Einstein before 1905
Einstein's curiosity in electromagnetic theory goes back at least to his Pavia days
of 1895, which followed his escape from the hated high school in Munich. The
following brief and rather disconnected remarks bear on his interest in electro-
dynamics during the decade preceding his creation of the special theory of
relativity.
- The Pavia Essay.* In 1895 Einstein sent a manuscript entitled Uber die
Untersuchung des Atherzustandes im magnetischen Felde (On the Examination
of the State of the Aether in a Magnetic Field) to his uncle Caesar Koch in Bel-
gium. This paper—which Einstein never published—was accompanied by a cov-
ering letter in which he wrote: '[The manuscript] deals with a very special theme
and is ... rather naive and incomplete, as can be expected from a young fellow.'
*In 1950, Einstein dated this manuscript to be from 1894 or 1895. It was sent to Caesar Koch in
1895, since in its covering letter Einstein tells of his intent to go to the ETH and adds, 'In the next
letter I shall write you what may come of this.' Both the essay and its covering letter were reproduced
in a paper by Mehra [Ml8].
130 RELATIVITY, THE SPECIAL THEORYSO thatOnce it is settled that « = 1, the Lorentz transformations have the property that
In showing the group property of Lorentz transformations, Poincare remarked
that the 'product' of two transformations (Eq. 6.3), one with velocity w,, the other
with v 2 , results in another Lorentz transformation with velocity v given by