The effects of distant matter on physical observables are discussed under the assumption that the distribution of distant matter is isotropic. We investigate the behaviours of light rays and radar signals near a massive star, the motion of a two-body system and the gravitational red-shifts of light rays emitted from a massive star, which is surrounded by distant matter. It is shown that the clock and the scale are affected by distant matter and then the effects on the physical observables become unobservable.