In the paper we consider the tidal field by analogy with electorstatics. The tidal forces result from the inhomogeneity of the gravitatiohal field. since the tidal forces not con be eliminated by a coordinate transformation

Hence we can describe the gravitational field by the tidal forces it produces. For example

we consider here two special cases: The first example consider the 'tidal range' of a drop of liguid at the center of a spaceship in orbit around the earth; As the second example consider the mumerical value of the tidal range in the open sea. The tidal range is exerted by the moon or the sun. Consider the relativistie generalization of the tidal field. As is well known

we have de fined the Riemann Curvature tensor in terms of entirely geometrical concepts

But this tensor also has a simple physical interpertation: Rβμν~ is the fidal force field. since the tidal force equation (33) can be used for measuring the Components ROLOK of the Riemann tensor. The Riemann tensor is therefore entirely determined by tidal force measurements. Final

To the Candition _kfK=0

Give a general proof using the exact Einstein equations.