The theory of general relativity (GR) is a theory of gravitation that was proposed by Albert Einstein in 1915. It is a geometric theory of gravity that explains how objects with mass interact with one another in the presence of a gravitational field.
The key concepts of GR as described in Einstein's original papers include the principle of equivalence, the curvature of spacetime, and the idea that gravity is not a force, but rather a result of the structure of spacetime.
Einstein developed the theory of GR through a series of thought experiments and mathematical calculations. He was inspired by the principle of equivalence, which states that the effects of gravity and acceleration are indistinguishable, and used this as a starting point for his theory.
Some of the key predictions of GR that have been confirmed by experiments include the bending of light by massive objects, the gravitational redshift, and the precession of the orbit of Mercury. More recent confirmations include the detection of gravitational waves and the observation of gravitational lensing.
Einstein's original papers on GR revolutionized the field of physics and our understanding of gravity. They provided a new framework for understanding the universe and laid the foundation for modern theories of cosmology and astrophysics. The theory of GR is still widely studied and used in research today.