A Möbius strip is made by taking a strip of paper, twisting it once and joining the ends. Now the strip has only one side and one edge. This can be demonstrated by putting a pencil down on the strip, turning the strip under the pencil until the pencil line returns to its starting place. The pencil line will appear on both sides of the strip, which means, in effect, that it has only one side. The Möbius strip was named after August Möbius in 1885.

     The classic joke concerning the Möbius strip is this: Why did the chicken cross the Möbius strip? Answer: To get to the same side.