Emerald Robinson: Hi! I'm Emerald Robinson and in this 'What is' video we are going to answer the question, what is a sonic boom? A sonic boom is a noise produced by something moving through the air faster than the speed of sound. But how does a sonic boom produced?
As an object moves through the air, it forces air molecules out of its way, creating waves. These waves move away from the object or propagate. If the object moves faster than these waves can propagate, the waves become more and more compressed. Eventually they are unable to get out of the way of the moving object quickly enough and combine into one large shock wave that trails behind the object.
Sonic booms comes from the shock wave created by an object moving faster than its own sound waves. The shock wave forms a cone shape around the object, with the tip of the cone at the front and the base trailing behind. When you first see the object, it appears to be moving without making any noise. Its only when the base of the cone reaches your ears, that you hear the boom.
In order to create a sonic boom, an object must move faster than a speed of sound about 700 miles per hour. Sometimes physicists call this speed Mach 1. Anything moving faster than Mach 1 is moving faster than the speed of sound. Any object, that moves faster than Mach 1 makes a sonic boom. Although we usually associate airplanes and space crafts with sonic booms, meteors and other objects entering the earth's atmosphere from space make them too. A whips crack is a mini sonic boom when its tip moves faster than the speed of sound. Even nature makes sonic booms. Lightning makes air molecules move faster than the speed of sound and because of the sonic, boom, we call thunder.