Mathematically, this can be defined as M = u/ c, where M is the Mach number, u is the local flow velocity with respect to the boundaries (i.e. And this ratio is due to the fact that the speed of sound varies from one location to the next, owing to differences in temperature and air density.Īn F-22 Raptor reaching a velocity high enough to achieve a sonic boom. The truth is that a Mach Number is a ratio rather than an actual direct measurement of speed. However this term is more loaded than you might think. When we hear the term Mach 1 it is easy to assume it is the speed of sound through Earth’s atmosphere. So how fast do you have to be going to do that? Definition: In other words, pushing past the sound barrier is defined as Mach 1. And when it comes to breaking this barrier, scientists use what is known as a Mach Number to represent the flow boundary past the local speed of sound.

This is a barrier that humanity may never be able to push past, mainly because doing so violate one of the most fundamental laws of physics – Einstein’s Theory of General Relativity.īut what about the speed of sound? This is another barrier in physics, but one which humanity has been able to break (several times over in fact). The most well-known is the speed of light, the maximum speed at which all conventional matter and all forms of information in the Universe can travel. Within the realm of physics, there are certain barriers that human beings have come to recognize.

Speed of sound in miles per hour