Mobius Strip
A Mobius Strip is an amusing three-dimensional object whose surface has only one side. Huh? Well, most objects you can imagine have a surface with two sides. For example, an ordinary piece of paper has two sides; you can paint one side blue and the other red. Now, a Mobius Strip has no other side! Don’t believe me? Try it yourself: cut a piece of paper about 1/2 inch (1 cm) wide and about 10 inches (25 cm) long. Close this strip of paper on itself - almost making a ring; however, rotate one end of this strip by 180 degrees. Tape the joint. Now take a red pen and start painting. You will very soon realize that you will be able to paint the whole Mobius Strip with red color without ever lifting the pen off its surface.
Mobius strip was named after the astronomer and mathematician August Ferdinand Mobius (1790-1868). He came up with his strip in September 1858. Independently, German mathematician Johann Benedict Listing (1808-1882) devised the same object in July 1858. Perhaps we should call it the Listing Strip?
