D O C U M E N T 2 5 J A N U A R Y 1 9 2 1 2 1
always be
away.[17]
I’m pleased that Busch appealed to you so
much.[18]
He really
is a splendid fellow, pure as a child. His playing is powerful; the only thing that
sometimes disturbs me a little is the undue austerity and relentless rhythm. No
dreaminess, no familiarity. Doesn’t something of Berlin rub off there? The other
great local violinists exhibit this phenomenon even more strongly than Busch.
Hearty greetings to all of you [with the youngsters] together, from your
Einstein.
with
Maltschiks.[19]
I straightened out the Methuen
affair.[20]
25. To Edouard Guillaume
[Berlin,] 20 January 1921
Dear Guillaume,
It is not
true[1]
[But has nothing to do with the famous Manifesto of the 93.] that
both statements,
1) The velocity of light is constant, but the bodies suffer a . . . contraction;
2) The bodies stay unchanged but the vel. of light is greater in the direction of
motion than perpendicular to it,
are entirely
equivalent.[2]
This equivalence is only valid with respect to the expla-
nation of Michelson’s experiment.
On the contrary, in case (2) the velocity of light would have to depend on the
motion of the generating light source against the coordinate system, which means
a physical hypothesis differing from Lorentz’s theory (contrary to (1)).
I decidedly contest, furthermore, that the equation
(where means the velocity of light with reference to , that of the same
light with reference to ), is compatible with the Lorentz transformation. This
equation is much rather merely derived via a blooper from the L[orentz] t[ransfor-
mation].
Best regards, yours,
A. Einstein.
P.S. Wasn’t Hadamard, when he spoke the quoted words, venting some celebratory
hot air?[3]
c2
c
1
2
cos +
-------------------------------------0
=
c0 K1 c2
K2
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