mach, ernst mach, german physicist of long ago, named after him, mach 1, mach 2. let's talk about cars. mach 1, right? mach 1 means when you have a car go 750 miles an hour or about 340 meters per second. that's fast. sound travels fast. not compared to light-- about a million as fast as light, but nevertheless sound. about 750 miles an hour. so if you're in an aircraft going 600 miles an hour, you don't produce a shockwave. that's because the waves don't pile up in front of you. i mean, you're traveling along like this, okay, and your wave is sort of like this. see, the waves are still going faster than you're going. it's only as you go as fast as the sound. of course then you get like this, okay? and you know what, those waves don't pile up anywhere but right here. so when an aircraft is going to the speed of sound and a little bit faster, down here they don't get a sonic boom. you only get the sonic boom when it's going appreciably fast enough so you that you can generate this shockwave like that. so the misconception is, people think that airplanes produce son