The physical nature of inertia is explored. Authors, based on Mach’s principle, offer hypothesis of the induction nature of inertia and theory, which allows extend the principle of relativity to the non-inertial reference systems. The system of differential equations, which eliminates the shortcomings of Newtonian mechanics and Special Theory of Relativity (STR) was composed according to this theory. Row of concrete calculations and explanations are made using the theory. Reason of constancy orbital velocities of galaxies is found out and way of its calculations is shown. Existence of dark matter and the new particles (neutralinos, axons, space vacuum etc.) is prejudiced. Axial deviation of the ray of light in gravitational field is explained and calculated. An example of calculation of the Mercury’s orbital motion is made and complex planets’ trajectories are explained by the action of new field with induction nature. Flat rotation of celestial bodies and shaping of planets’ rings (like the Saturn’s rings) are explained. Indistinguishability of Doppler and Einstein’s effects for terrestrial observer is shown.