D O C U M E N T 3 9 1 I M P R E S S I O N S I N J A P A N 3 3 5
world of constant and variable (in the temporal
sense)[5]
negative curvature. There
it was, of course, necessary (in order to obtain the only interesting material
real[6]
world, from the point of view of physics and geometry) to use a different expres-
sion for the interval, in that I took it (according to Bianchi, Lezioni di geometria
differenziale, volume 1) in the following form:
;
the result of the computations showed that in this case not only a world of constant
(already negative) curvature can exist but also a world of (in the temporal
sense)[7]
variable curvature. The existence of the possibility of obtaining from your universal
equations a world of constant negative curvature is of very special interest to me,
which is why I earnestly ask you not to deny me an answer to this letter of mine,
although I know how very busy you are going to be.
In the event that you find the calculations discussed in this letter correct, please
do not reject my letting the editorial office of the Zeitschrift für Physik know about
it; in this case you might perhaps publish a correction or make possible a printing
of an excerpt from the present
letter.[8]
Your sincere
admirer,[9]
A. Friedmann.
At head of the document: “Physical Central Observatory, Petrograd, Wassili Ostrov, 23 Linie, 2nd
professor.”
391. “Musings on My Impressions in Japan”
[Einstein 1923b]
Manuscript completed on or after 7 December 1922.
Published January
1923[1]
In: Kaizo 5 (1923): 338–343.
I have been traveling much around the world in the last few years, actually more
than befits a scholar. The likes of me really ought to stay quietly put in his study
and ponder. For my earlier trips there was always an excuse that could easily pacify
my not very susceptible conscience. But when
Yamamoto’s[2]
invitation to Japan
arrived, I immediately resolved to go on such a great voyage that must demand
months, even though I am unable to offer any excuse other
than[3]
that I would
dτ2
R x4)2(dx1 (
x3
2
--------------- - 2 dx2 2 dx3 2) + + M2dx4 2 + =
[p. 343]
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