Albert Einstein is the famous physicist known for the theory of relativity, which revolutionized our understanding of space, time, and gravity. Formulated in the early 20th century, this theory consists of two parts: special relativity and general relativity. Special relativity, introduced in 1905, focuses on the physics of objects moving at constant speeds, particularly the speed of light. General relativity, published in 1915, extends these ideas to include acceleration and gravitation, explaining how massive objects like planets and stars warp the fabric of spacetime. Einstein's contributions fundamentally changed modern physics and our conceptualization of the universe.