D O C . 3 1 I D E A S A N D M E T H O D S 1 1 7
and which, due to the daily rotation of the earth, would change by itself. But no ef-
fect ever could be verified that would allow for an interpretation as the action of
the ether wind.
H. A. Lorentz himself 〈felt and〉 saw clearly that this negative outcome was a fact
of the highest significance, and his theory had to deal with it. With penetrating cal-
culations he proved that, according to his theory, the ether wind could not have any
experimentally verifiable effect in nearly all actually performable and performed
tests. This proof was based upon the fact that the velocity v of the ether wind is so
small compared to the speed of light that the quantity becomes a practi-
cally vanishing ratio (order of magnitude one-hundredth of a million, ). There
was only one experiment, namely the famous one by Michelson (1881, repeated in
1887 with even higher accuracy by Michelson and
Morley)[11]
and its precision was
so high that, according to Lorentz’s theory, it would definitely have been sufficient
to demonstrate the ether wind.
It is well worthwhile to consider the gist of this experiment even though its prop-
er description is not necessary for our purposes. Let be a rod of length . Let
a ray of light go from to , reflect it in so that it comes back to . Light re-
quires a time of to traverse this distance if the rod is at rest relative to the ether.
But if the rod is moved relative to the ether with a velocity v, one obtains a time
different from ; different ( , respectively) depending on the rod being ori-
ented in the direction of the ether wind or perpendicular to it. From elementary con-
siderations, one obtains
.
The time difference in Michelson’s interference experiment should have
caused a shift in the interference pattern, viewed via telescope, when the entire ap-
paratus was rotated by 90 o about a vertical axis. The result did not occur; even this
ether-wind-weather vane of utmost sensitivity did not feel the ether wind.
c
v
c
-- -
⎝ ⎠
⎛ ⎞
2
10–8
AB l
A B B A
2l
c
---- -
2l
c
---- - Δ1, Δ2
Δ1
2l
c
---- -
1
1
v2-
c2
---- –
--------------
⋅ =
Δ2
2l
c
---- -
1
1
v2-
c2
---- –
------------------
⋅ =
Δ1 Δ2 –
[p. 5]