Albert Einstein's theory of relativity describing absolute quantities | Britannica

Albert Einstein's special theory of relativity | Britannica

A simplified introduction to Einstein's theory of relativity

The Theory of Relativity Lesson for Kids

Relativity theory, formulated by Albert Einstein in the early 20th century, revolutionized our understanding of space, time, and gravity. It consists of two major branches: special relativity and general relativity. Together, these theories have reshaped our perception of the fundamental nature of the universe. Special relativity, published by Einstein in 1905, introduced a new way of looking at the laws of physics in the absence of gravitational forces. It is built upon two postulates: the prin