Mach speed, often referred to as "Mach," is a dimensionless unit used to describe the speed of an object relative to the speed of sound in the surrounding medium. It is named after the Austrian physicist and philosopher Ernst Mach. When an object is traveling at Mach 1, it is moving at the speed of sound in that particular medium. If it travels at Mach 2, it is moving at twice the speed of sound, and so on.
In practical terms, Mach speed is significant because it represents the ratio of an object's velocity to the speed at which pressure waves (i.e., sound waves) propagate through the medium. As an object moves through the air or another fluid, it causes pressure waves to form in front of it. When the object travels at or above the speed of sound, it catches up to and passes those pressure waves, creating a shock wave known as a "sonic boom."
What happens if you travel at or above Mach speed in real life:
Subsonic Flight (Mach < 1): When an object travels at speeds lower than the speed of sound, it is considered to be in subsonic flight. Most commercial airliners, for example, operate at subsonic speeds, typically around Mach 0.8 (80% of the speed of sound).
Transonic Flight (Mach ~ 1): Transonic flight occurs when an object is in the process of transitioning from subsonic to supersonic speeds. At this speed, shock waves can start to form, leading to potential turbulence and drag-related challenges.
Supersonic Flight (Mach > 1): Supersonic flight happens when an object moves at a speed greater than the speed of sound. Aircraft designed for supersonic flight, like the Concorde (retired) and some military jets, experience shock waves that can cause loud sonic booms and increased aerodynamic challenges.
Hypersonic Flight (Mach > 5): Hypersonic flight involves extremely high speeds, typically above Mach 5. Objects traveling at hypersonic speeds experience significant aerodynamic heating due to air friction, which presents considerable engineering and material challenges.
Transonic and Supersonic Speeds (Mach ~ 1 to 5) in Atmosphere: As an object reaches and surpasses the speed of sound, the behavior of the air around it changes dramatically. The aerodynamic forces, drag, and temperature increase significantly. The sonic boom produced during supersonic flight can be heard on the ground as a loud noise.
It's important to note that traveling at extremely high speeds, especially in the atmosphere, requires specialized engineering and materials due to the challenges posed by aerodynamic heating and other factors. Hypersonic flight, in particular, is an area of ongoing research and development for military and space exploration applications.