Which physicist developed the theory of relativity?

The correct choice is Albert Einstein, who developed the theory of relativity, which fundamentally transformed our understanding of space, time, and gravity. This theory consists of two main parts: special relativity and general relativity. Special relativity, introduced in 1905, deals with the physics of objects moving at constant speed, particularly at speeds close to the speed of light. It introduced groundbreaking concepts such as the equivalence of mass and energy, expressed in the famous equation E=mc². General relativity, published in 1915, further expands on these ideas by describing how mass and energy influence the curvature of space-time, leading to the phenomenon we perceive as gravity.

Einstein’s work is pivotal because it challenged and expanded upon the classical mechanics established by earlier scientists, such as Newton, who focused on laws of motion and universal gravitation. While Blaise Pascal contributed significantly to mathematics and fluid mechanics, and Carl Friedrich Gauss made major contributions to various fields in mathematics and physics, neither developed the theory of relativity. Einstein's groundbreaking theories have had a lasting impact on modern physics and our conceptual framework of the universe.