Commercial airplanes now are no faster than they were in the 1960s. We’ve made advances in engines and materials and computers, so why can’t we strap fancy ultra-powerful engines to a jetliner and go from New York to LA in half the time it takes now? There are a lot of reasons and pretty much all of them are rooted in the physics of sound. To understand why the speed of sound is so important for aircraft, first we have to have a solid understanding of what sound is. Here’s everything you need to know about sound and sonic booms in our first of three episodes on supersonic flight.