  In this paper we consider equations of motion for 2-body problem according to
an observer close to one of the gravitational bodies. The influence of the
Thomas precession of the observer's frame has an important role. The equations
of motion are based on a nonlinear connection modified by the action of an
orthogonal tensor which synchronizes the 4-velocities of the considered two
bodies. Finally we present periastron shift according to an observer inside the
gravitational field, using the orthonormal coordinates. This is different
approach than that used in General Relativity where the periastron shift is
only given as observed far from the massive bodies.

General Physics