Parametrical optics effects at the presence of gravitation

It is shown that in the model of a flat 3D space the time and the gravitation constant G represent in fact material (constitutive) coefficients of the flat space (or the corresponding optical medium) and should, therefore, obey the Neumann principle. Gravitation field of spherical symmetric mass does not lead to the lowering of symmetry of the space and the appearance of anisotropy. In particular, the relations which describe the changes in the refractive indices of the space treated as an optical medium near the massive spherical body under the influence of its gravitation field have been derived. The light velocity depends upon the gravitation field strength and approaches c₀ value only if the gravitation field strength tends to zero