Rudolf Clausius was a German physicist and mathematician, born on January 2, 1822. He is best known for formulating the second law of thermodynamics, which describes how energy moves and transforms in physical systems. Clausius introduced the concept of entropy, a measure of disorder or randomness in a system, which has become fundamental in understanding thermodynamic processes. Clausius's work laid the groundwork for modern thermodynamics and influenced various fields, including physics, chemistry, and engineering. His contributions helped explain the behavior of heat engines and the efficiency of energy conversion, making him a key figure in the development of thermodynamic theory.