Answer: Albert Einstein
Explanation: Albert Einstein was a physicist who developed the theory of relativity and thus transformed modern physics. Together with quantum mechanics, the theory of relativity is the basis for modern physics. Albert Einstein is also known as a hard-to-understand physicist, since his work also influenced the philosophy of science, i.e. he was known for the philosophical approach to the study of natural sciences. He is best known for his mass and energy equivalence formula E = mc².