A strict derivation of the Schwarzschild metric, based solely
on Newton’s law of free fall and the equivalence principle, is
presented. In the light of it, regarding Schwarzschild’s coordinates
as representing the point of view of a distant observer
resting relative to the source of a centrally symmetric gravitational
field, proves illegitimate. Such point of view is better
represented by the Painlev´e-Gullstrand system of coordinates,
which agrees with Schwarzschild’s system with respect to its
spatial coordinates and time scale, but disagrees with respect
to the relation of simultaneity. A duality of the Schwarzschild
solution and its time-irreversibility is suggested. The physical
meaning of the coordinate singularity at the Schwarzschild
radius is clarified.
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