Radio telescopes are said to "listen" to space because... 1. they monitor sound waves
2. they detect radio waves
3. they detect electromagnetic waves
4. they detect only aural EM waves

An important dimensionless parameter concerned with very high-speed flow is the mach number, defined as v/c, where v is the speed of the object such as an airplane or projectile, and c is the speed of sound in the fluid surrounding the object. for a projectile traveling at 1170 mph through air at 50 ˚f and standard atmospheric pressure, what is the value of the mach number?