Optimally, Mach 2 is 1,552.4141 mph. This measurement is twice the speed of a moving object relative to the speed of sound in a surrounding medium when placed under ambient conditions.
It is important to note that the number that constitutes Mach 2 can fluctuate depending on varying conditions that can alter the speed of sound. For example, sound travels at slightly different speeds under different temperature conditions, and these conditions can vary based on altitude.
While the concept of Mach is named after Austrian physicist and philosopher Ernst Mach, the moniker is given as a tribute to him, and not because he hatched the concept. The scientist who derived the concept of Mach was aeronautical engineer and scientist Jakob Ackeret. However, Ackeret decided to name his concept after Mach, who had passed away shortly before to the conceptual discovery.