The Magic Trick

It’s based on something called capillary action. Basically when you get to a small enough scale, surface forces become more important than gravity. This is how insects walk on the ceiling – the surface attraction between their feet and the ceiling is stronger than gravity pulling them down. With very thin tubes or the fibres in the paper serviette, the surface tension acting on the liquid water and adhesion with the paper pulls it up more strongly than gravity pulls it down. This is the same action as in the Water Daisies we made a few weeks ago, or in the wick of a candle.