Theory of relativity

The theory of relativity is a theory Albert Einstein created in the early 1900s. There are two theories of relativity. The first is special relativity and the second is general relativity.

The theory tries to solve problems which could not be solved by Classical physics, or by 19th century physics. Some things, like the orbit of Mercury or the way light from distant sources bends as it passes a star, cannot be explained by the physics of 1900. Einstein tried to change the basic ideas of physics. He came up with two theories to do that. The first was called Special relativity and the second was called General relativity.