D O C U M E N T 6 5 F E B R U A R Y 1 9 2 1 5 5
of course, causally determined only insofar as it exhibits characteristics indepen-
dent of the choice of a coordinate system. Questions such as where does the grav-
itational field that forms when I set the coordinate system into rotation come from?
are therefore senseless.
Experiments like the one you suggest are, in
The gen. theory of relativity allows an exact calculation of the result in advance.
Unfortunately, all the effects coming into consideration here enter into the factor:
gravitational constant/square of the velocity of light, which is of order of magni-
and causes these effects not to be attainable by laboratory experiment
because of their
In gr. respect.
65. From Paul Oppenheim
Frankfurt am M[ain], 46 Guiollett Street, 25 February 1921
My dear Professor,
I had just written the enclosed protest letter to Mr.
when his book
arrived, which I send you herewith. My letter is thus, unfortunately, outdated and I
ask you now please kindly to let me know what I ought to write with regard to pages
I find the author’s whole proceedings obnoxious and his enthusiasm is
absolutely no excuse; I rather see in this an unacceptable exploitation of your name
for commercial purposes, as it has unfortunately probably not been the first time. I
am, naturally, innocent of the whole indiscretion, otherwise I would be even more
I would, of course, not like to answer Mr. Fabre’s letter, which
I received before my trip to Berlin, before I have your response about what to write
him, and would therefore be obliged to you if you let me know as soon as possible
what and how I ought to reply. I would naturally very much prefer it if you wrote
him directly; for one can see from this case what can happen when someone stands
in-between, even when he, like I, is so careful and devoted to you; one formal rea-
son you can have for writing him directly is the fact that I forwarded a copy of his
letter at his request. If, however, you for any reason prefer not to correspond with
such a person directly anymore, please feel free to make use of my services as inter-
mediary. One could also consider sending out my letter as if I had not yet received
his book; I would not find this altogether unprincipled, as I had demonstrably writ-
ten him before receipt of the work. If you think this approach practicable, I request
that you return my letter addressed to Mr. Fabre: otherwise, please destroy it. If you
would like to read the book itself before returning it to me, there is, of course,
plenty of time for that.