THE rips that tear through a rubber balloon when it is popped travel faster than the speed of sound in rubber, creating waves similar to the sonic boom made by an aircraft when it breaks the sound barrier.

The finding contradicts current theory, which says that cracks cannot propagate faster than the speed of sound in a material. Mike Marder and his colleagues at the University of Texas at Austin were alerted to the odd behaviour of bursting balloons when they looked at the fragments left over after a balloon goes bang. The pieces often have wavy edges, which no …