Albert Einstein's special theory of relativity | Britannica

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