Every good magician should be able to levitate objects! This trick will enable you to amaze your friends and family with your ability to cause ping pong balls to mysteriously rise up into the air… A hair dryer with a ‘cool’ setting A ping pong ball 1. Set the hair dryer to cool, switch it on, and point it at the ceiling. 2. Carefully put the ping pong ball in the stream of air. Hold the hair dryer very steady and watch as the ping pong ball floats in the stream of air. 3. Now carefully move the hairdryer from left to right and watch how the ball moves as well, staying in the stream of air. Before showing this trick to your friends, ask them to predict what they think will happen. Try prompting them to say that the air from the hairdryer will just blow the ping pong ball away. At this point, you can reveal your magic powers and "demand" that the ping pong ball levitates in the stream of air. You’ve probably realised by now that there isn’t any magic happening here. Your friends may well have been happy with the prediction that the ball would get blown away, but why doesn’t it? The air from the hair dryer flows around the outside of the ball and if you position the ball carefully, the air flows evenly around each side. Gravity pulls the ball downwards while the pressure below the ball from the moving air forces it upwards. This means that all the forces acting on the ball are balanced and the ball hovers in mid air. You can make the ball follow the stream of air as you move the hairdryer because Bernoulli's principle says that the fast moving air around the sides of the ball is at a lower pressure than the surrounding stationary air. If the ball tries to leave the stream of air, the still, higher pressure air will push it back in – so the ball will float in the flow no matter how you move it. And that’s (not) magic Debbie!