The relativity of space-time

Many years ago Poincare convincingly demonstrated that space geometry does not have a meaning in itself, but only within the aggregate ''geometry + measuring instruments.'' Hitherto, this result did not manifest itself in physical theory, which proceeded along another path and admitted solely a dependence of space-time geometry on the matter-energy momentum tenser. In this paper it is shown how the fact, stated by Poincare, can manifest itself in space-time properties of noninertial frames of reference.