  The radius of the observable region of the Universe is of the order of its
Schwarzschild radius. Due to the spherical symmetry, this allows to check the
properties of the gravitational force in the vicinity of the Schwarzschild
radius by comparing the theoretical and observed Hubble diagram at high
redshifts. This can be done in a simple model that fellows from
projective-invariant equations of gravitation.This paper shows that the Hubble
diagram up to $z=8$ testifies in favor of the specific properties of gravity
near and inside of the Schwarzschild radius.
