Ernst Waldfried Josef Wenzel Mach was an Austrian physicist and philosopher, noted for his contributions to physics such as study of shock waves. The ratio of one's speed to that of sound is named the Mach number in his honor. As a philosopher of science, he was a major influence on logical positivism, American pragmatism and through his criticism of Newton's theories of space and time, foreshadowing Einstein's theory of relativity.

https://en.wikipedia.org/wiki/Ernst_Mach