Ernst Mach

1838-1916

Austrian physicist associated with the speed of sound and its multiples (known as Mach 1, Mach 2, Mach 3, etc., in his honor). Mach showed that the characteristics of airflow over a moving object change dramatically as the object approaches the speed of sound.

Mach's biggest impact was in the philosophy of science. He provided a clear distinction between physics and psychology and brought rigor to both disciplines. He upheld the principle, a tenet of scientific positivism, that no statement should be accepted by science until it has been verified by experimentation.