What is Sound barrier?
[[File:FA-18 Hornet breaking sound barrier (7 July 1999).jpg|thumb|An F/A-18 Hornet aircraft breaking the sound barrier.]] Sound barrier is a phenomenon where sound waves in the air get packed densely ahead of a moving thing (such an [[aircraft]]) and form a highly pressurized area there. [[Sound]] is vibration in the air, and it goes as sound waves. They move at constant speed in the air. When an object, such as an aircraft moves in the air, it produces sound. The sound waves spread all around the object. When the object comes closer to the speed of sound ([[Mach number|Mach]] 1), air [[pressure]] changes drastically, and there will be pressure waves around the object - the sound waves can no more escape ahead, but get packed and form a high pressure area ahead the object. This pressure will rise until the speed of Mach 1 is reached. At this point, it will suddenly decrease, and a sound burst will result. The speed of Mach 1, where this burst happens, is often called '''sound barrier'''. Aircraft wings had to be redesigned, so that certain aircraft can fly at speeds faster than Mach 1. Flying faster than sound produces a [[sonic boom]]. Breaking the sound barrier will take a lot of [[energy]], and breaking it will succeed only with specially designed missiles and aircraft. {{Stub}} [[Category:Thermodynamics]]