Theory of relativity facts for kids
The theory aims to solve problems which could not be solved by classical physics, or by 19th century physics. Certain observations, 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 set out to revise the basic ideas of physics. His work was done in two stages, and each stage has a separate page on this wiki.
Theory of relativity Facts for Kids. Kiddle Encyclopedia.