D O C U M E N T 3 1 J A N U A R Y 1 9 2 2 5 7

8.) From this theorem by Gibbs therefore follows: No matter how long and far

we run along with the group, we always see in it solely the waves with the small

inclinations between , which correspond to one the slit breadth (or a part of

it)—just the fictitious (dead!) waves far in advance of the head of the group have

the large inclinations.

31. To Paul Ehrenfest

[Berlin, between 19 and 22 January

1922][1]

Dear Ehrenfest,

Everyone is pelting me about my constant doggedness. Laue already had a

proper duel with me at the

colloquium.[2]

But I’m sure of my point. I performed a

fine, rigorous calculation that will surely convince you. It’s just too long for me to

be able to tell you the essence so briefly. In a couple of weeks I’ll send you the cor-

rection

proofs.[3]

The error in your

consideration[4]

lies in the following:

You prove that a wave that enters at A after propagating has

the same inclination for the wave normal at B as at A. This

would be true—if the wave complex arrived at B. This, how-

ever, is not what it does; instead it arrives at C and its wave

normal at C has the orientation AC.The whole problem can

only be solved properly if one examines the course of the ray.

I started from a strict solution and consider my proof secure—

whatever a theoretical physicist may call secure. I am peni-

tently remorseful of formerly committed blunders . . . . In any

event I am curious what you’ll say about my proof. My love

for it is naturally based for the most part on my having agonized over it. The Span-

ish fellow scientist interested in the Au-ion affair is called Kuno Kocherthaler,

Apartment 425, Madrid, 9 Lealtad Street. I laughed myself to tears about your mes-

sage regarding

him.[5]

With Grommer I am trying to address the zero-point energy

problem.[6]

It’s not easy. I also have in mind to determine with Geiger and Bothe

the quadratic Doppler effect by means of a few little tricks; but it is

difficult.[7]

Prod

K[amerlingh] Onnes about the superconductivity

experiments.[8]

Did the young

American find fluctuations? I ought to have gone to Paris for New Year’s, but could

not overcome my weariness of

traveling.[9]

Kramers recently visited me, an excel-

lent

fellow.[10]

Are you still thinking about the spectral

congress?[11]

It really would

be fine if Julius were to analyze the solar-center/solar-limb effect photographically/

photometrically by then, so that some clarity could be reached on

this.[12]

The main

ε±