General Relativity Part 1 : Introduction
Jason, I think I’ll start before you finish, to save a bit of my time. So I’m starting off with a summary of special relativity and move on from there. 
By essentially extending on the principle of Galilean relativity, by changing ‘laws of motion’ to ‘laws of physics Einstein showed that the speed of light, c is absolute in all reference frames, he demolished the impractical ether concept.
Then, using the Lorentz contraction factor-independently proposed by the Dutch physicist H.A. Lorentz and Irish physicist George Fitzgerald in attempt to explain the null result in the Michelson-Morely experiment-Einstein showed how length contraction occurs in conjunction with time dilation and mass increase as an object approaches relativistic speeds.
In establishing the theory of special relativity, Einstein concluded that there is no way for an observer to determine whether a given frame of reference is at rest or is moving at constant velocity in a straight line. Thus, the laws of physics must be the same in different inertial reference frames.
After completing the theory of special relativity, Einstein then proceeded to tackle the general case of motion, where reference frames can be accelerating. Additionally, relativity is already compatible with Maxwell’s laws of electromagnetism but not Newton’s law of gravity. From special relativity in 1905, Einstein would spend his next 10 years in formulating his theory of general relativity.
Newton’s theory of gravity says that gravity is a mysterious force that instantaneously exerts itself in influencing distant objects. This contradicts relativity, as nothing can travel faster than the speed of light. Additionally, the concept of instantaneous requires the existence of universal time, which was abolished in favor of absolute time…
