What is space represented by in the theory of general relativity ?
The experimental observation that all objects in free fall accelerate at the same rate , as noted by Galileo and then embodied in Newton 's theory as the equality of gravitational and inertial masses , and later confirmed to high accuracy by modern forms of the Eötvös experiment , is the basis of the Equivalence Principle , from which basis Einstein 's theory of general relativity initially took off .