Hypothesis that the inertial forces acting on a body in accelerated motion are determined by the quantity and distribution of matter in the universe.
relativity ; unaware that George Berkeley had proposed similar views in the 18th century, he attributed the idea to Ernst Mach . He abandoned the principle when he realized that {{link=inertia">inertia is assumed in the geodesic equation of motion (see geodesy ) and need not depend on the existence of matter elsewhere in the universe.