Many people have heard a sonic boom, but few have seen one. When an airplane traveling at a speed higher than that of sound, density waves of sound emitted by the plane can not precede it, and then accumulate in a cone behind the aircraft. When this shock wave passes, you hear all at once the sound that had been delivered to over a period of time: a sonic boom. However, when a plane accelerates to the point of breaking the sound barrier, could form an unusual cloud. The origin of this cloud is still under debate. The main theory is that a decrease in atmospheric pressure in the plane, described by the Prandtl-Glauert, singularity occurs so that moist air condenses there and form water droplets. Above, an F/A-18 Hornet was photographed at the right time to break the sound barrier. The large meteors and the space shuttle often produce audible sonic booms before the Earth's atmosphere to slow them at a lower speed than the sound.