How Fast Is Balloon Bursting?

Balloon rubber tears at Mach 0.7 — about 250 m/s, but the visible pop point happens at about 70 m/s. Sound travels slightly slower in rubber than in air, which is why you hear the bang clearly: the rupture has already finished by the time the sound reaches your ears.

Balloon rubber tears faster than the speed of sound through rubber — which is why you hear the pop after it has already finished.

• Same speed as a tennis serve
• Tears faster than sound in rubber