Exploding bottle bottom trick. Demonstration of how hitting the top of a liquid-filled glass bottle can cause the bottom to fall off. Hitting the top of the bottle causes the bottle to move downwards. The liquid does not move, due to inertia, and so an area of low pressure develops at the bottom of the bottle. The low pressure causes the formation of tiny bubbles in the liquid. The high pressure of the liquid above the bubbles causes them to collapse, creating shock and sound waves. When lots of bubbles collapse these waves cause the glass to break. This is an example of cavitation.