The Omnifarium - Science/PaperCylinder.html

The Rotating Paper Cylinder

Category: Science
Thu, 18 Oct 2007, 20:51

I first tried this more than three decades ago after reading about it in Martin Gardner's monthly column in Scientific American. It was a fun trick, and at the time, it almost convinced me that I had psychic powers.

To do this "experiment", make a cylinder out of a piece of paper as shown in the following photo. Before you glue the ends together, you may decorate the cylinder as you please. Support the cylinder with another narrow piece of paper pushed through slits on opposite sides of the cylinder, and balance it on a suitable narrow support with a pin or needle. The cylinder should rotate freely. If necessary, adjust the cylinder so that it rests more or less vertically.

With the cylinder balanced and still, carefully cup your hands around the cylinder without touching it, as shown by the following photo:

Concentrate on the cylinder. After a few seconds, the cylinder should start to rotate. Before I offer the explanation for this behavior, think about why this happens.

One possible explanation is telekinesis, the ability to initiate movement without perceptible mechanical means, merely using the power of ones mind. Think of ways to test this hypothesis. Is it even possible to test this hypothesis? Note that if the theory is not testable, it is not, by definition, a scientific theory.

The real reason for the rotation of the cylinder is quite mundane. The cylinder is quite vulnerable to the slightest air currents. By cupping your hands around the cylinder, you are magnifying the slightest currents, increasing the chances that the cylinder will be affected by these currents. Your own breath may itself contribute to the "breeze" surrounding the cylinder.

A clever sort of person, though, could easily convince gullible spectators that his psychic powers moved the cylinder.

I'll leave you with a chemistry joke I heard recently at the Ontario Science Centre. Two atoms are chatting:

First atom: "I just lost an electron."

Second atom: "Are you sure?"

First atom: "Yes, I'm positive!"

Hans

path: /Science | permanent link to this entry