Since the speed of sound depends on the air, which changes at different altitudes, are “Mach” speeds dependent on the altitude? Or is it basically just like 100 °C is the same even at altitudes where water boils at a lower temperature (in that it is a fixed speed based on the speed of sound at sea level)?
Technically it would reach an altitude where it would become ‘null’ due to dividing by zero. You would eventually hit the vacuum of space where there is no speed of sound and any speed is faster than it.