D O C U M E N T 4 1 M A Y 1 9 2 3 4 1
rived out of your special action principle—provided one doesn’t want to introduce,
off the cuff, higher powers for the electromagnetic invariants. I shall later send you
the correction to my
paper,[2]
which I definitely must publish because Eddington’s
idea must necessarily be thought through to the end. I now also believe that all these
purely formal attempts will not advance the physical understanding any further. It
may be that field theory has already produced all that lies within its powers. As re-
gards the cosmological problem, I am not of your
opinion.[3]
According to De
Sitter, two material points sufficiently distant from each other accelerate as they
move apart ¢and². If there isn’t any quasi-static universe after all, then get rid of the
cosmological term.
Cordial greetings from your
A. Einstein.
41. To Georg Maschke
Berlin, 24 May 1923
Dear Mr. Maschke,
Unfortunately, as it seems, you did not receive my postcard from Leyden, in
which I suggested a meeting.
Both projects ought to be approached with caution, but not with absolute
rejection.[1]
Aircraft for high
altitudes[2]
would probably only come into consider-
ation for military purposes, because of the great risk of fatality and mainly because
of the immense pressure forces that the walls would have to withstand from the in-
terior. There is also the problem of the misting and icing over of the windows,
which is disastrous for the piloting. The technical development will probably cost
considerable human sacrifice. The motor with
auto-ignition[3]
arises out of a rea-
sonable thought, but the difficulties are considerable; woe, if the ignition chamber
fills up with lubricant. Nor will it be easy to direct the explosion out of the over-
compressed space through a necessarily narrow opening in the main piston area.
But since a trial ought not to be very costly, this matter should not be dismissed out
of hand. If the invention were to prove worthwhile, this business could become sig-
nificant; one would first have to see whether the design envisioned by the inventor
offered any prospect of success.
Amicable regards, yours,
P. S. I would be pleased if I could stay in contact with you regularly, without my
name being mentioned officially.