2 6 0 D O C U M E N T 1 3 3 S E P T E M B E R 1 9 2 0
According to my conception, it is impossible to derive the Doppler principle
from equation
In order to define radiation as a frequency , I need a wave
of the kind
is the number of waves that pass by a point in the coordinate system, while t = 1,
i.e., while a seconds clock, arranged at rest relative to this point of the coordinate
system, is making one tick. The Doppler principle results from the equation
whereby this equation must be made into an identity through the Lorentz transfor-
mation. I absolutely would not know how to indicate a simpler derivation of the
Doppler principle. In any case, from equation (1) nothing at all can be concluded
either about the rate of a moving clock or about the Doppler principle. You must
think of it as if t has the meaning
= time of emission of the light signal
at A
= time of arrival of the l[ight] s[ig]. at B.
There is no such thing as one clock that can indicate t.
Best regards, yours,
A. Einstein.
133. From Max Planck
Gmund on Lake Tegern, Grundner Farm, 5 September 1920
Dear Colleague,
On returning to Germany from Southern Tyrol, where no news reached me, I dis-
covered the reports about the almost incredibly disgusting behavior that had oc-
curred at the Berlin Philharmonic and about everything connected with
I am
momentarily at a loss for an explanation of how such baseness can be possible
among highly educated people. But of very much greater importance to me than
this problem is the issue of what impression such machinations are apt to make on
you personally and I am plagued by the thought of the possibility that you will lose
x y z + +
------------------------------ -
x y z + +
------------------------------ - t
x y z + +
----------------------------------------- - =
light signal
t t2 t1 –=
t1 A =
t2 B =
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