The scientist who developed the theory of relativity is Albert Einstein. He introduced this groundbreaking theory in the early 20th century, encapsulated by two key components: special relativity and general relativity. Special relativity, published in 1905, revolutionized the understanding of space and time, establishing that the speed of light is constant and that time can vary based on an observer's motion. General relativity, introduced in 1915, expanded these ideas to include gravitation, proposing that massive objects warp spacetime, influencing the motion of other objects. Einstein's theories have vast implications across physics and cosmology, fundamentally changing our grasp of the universe.