Sound Barrier

aviation · physics · speed

What it is. The sound barrier is not a real wall in the sky, but rather a zone where aircraft experience huge increases in drag and strange aerodynamic effects as they approach the speed of sound (about 761 miles per hour at sea level).

Shock waves form. As an aircraft gets closer to the speed of sound, shock waves build up in front of it like waves stacking against a wall. These shock waves push back hard against the plane, making it very difficult to go faster.

Sonic boom happens. When an aircraft finally breaks through and flies faster than sound, it creates a sonic boom, a loud explosive sound that people on the ground can hear.

First to break it. Chuck Yeager became the first pilot to fly faster than sound in 1947 in an experimental plane called the Bell X-1, proving that the barrier could be overcome.

Not really a barrier. Today we know the sound barrier is not truly impossible to cross, and modern fighter jets routinely fly supersonic (faster than sound) without much trouble.