GRAVITATION~ SPACETIME WITH AND WITHOUT COORDINATES

Now it came to me:...the independence of the

gravitational acceleration from the nature of

the falling substance, may be expressed as

follows:in a gravitational field (of small

spatial extension) things behave as they do

in a space free of gravitation...This happened

in 1908. Why were another seven years required

for the construction of the general theory of

relativity? The main reason lies in the fact that

it is not so easy to free oneself from the idea

that coordinates must have an immediate metrical

meaning.

現在，我想到:....引力加速度與落體的性質無關，可表述如下:在(空間廣延很小的)引力場中，事物的行為與在無引力的空間中一樣...這種想法產生於1908年。至於為何要花費長達七年的時間才完成廣義相對論呢?主要的原因是人們難以擺脫座標必須具有直接度規意義的觀念。

ALBERT EINSTEIN [in Schilpp (1949), pp.65-67.]