It’s an eye-catching sight that has been captured by photographers and camera crews time and again; a military jet sweeps in low and fast, travelling at hundreds of miles an hour. As it picks up speed, it begins to be surrounded by a giant cone of vapour, a cloud that seems to erupt around the aircraft.

That, we’re often told in excitable captions, is a sonic boom.

Except, it isn’t – or at least, not quite. What you’re seeing is a physical effect that takes place as an aircraft approaches the speed of sound, but it’s not the sonic boom itself.

As aircraft design has become more sophisticated, planes have become more streamlined, and faster – and begun to do things to the air around them that they just weren’t able to do when they were slower and more cumbersome. And the mystery shockwaves that surround, low, fast-flying planes as they approach and then pass the sound barrier are proof that the air starts to do some very strange things at such speeds.