Making gravity consistent with special relativity required a major revision of how we think of space & time
Einstein’s thinking started with a simple principle, now known as the Equivalence Principle.
All things fall in the same way. If you drop a bowling ball, it falls in the same way as a pea….
This happens because the “inertial” mass that enters Newton’s law of motion, F=ma, is the same as the “gravitational” mass that enters the gravitational force law.
COSMOS to HUMANITY, Spring 2008
Lecture 2 , slide 3