What were the problems?

gravity exerts its influence across space First problem In special relativity, Einstein established that nothing can travel faster than the speed of light. But according to Newton’s theory gravity exerts its influence across space instantaneously.

Second problem Einstein established that 2) In special relativity Einstein established that the physics laws are the same in all the inertial frames ( those in which the inertia principle is true). But what about a non- inertial system ?

General relativity is the answer

Heart of theory Gravity is not a force pulling masses together but a simple consequence of the geometry of space- time. In the absence of mass space-time is essentially a grid and the shortest path for an object to travel through it is a straight line. But when a mass is present it causes the fabric of space-time to curve so that an object traveling nearby must follow a rounded trajectory called geodesic, which is the generalization of the notion of a “straight line” to a “curved space”.

Curved space

Gravity is but the geometry of spacetime “Matter tells space how to curve. Space tells matter how to move.” – American physicist John Wheeler