I graduated from a faculty of mathematics, so don't know if there are other geeks who will find this amusing, but I came across this webpage: http://www.kleinbottle.com/whats_a_klein_bottle.htm it describes the Klein bottle: Take a rectangle and join one pair of opposite sides -- you'll now have a cylinder. Now join the other pair of sides with a half-twist. That last step isn't possible in our universe, sad to say. A true Klein Bottle requires 4-dimensions because the surface has to pass through itself without a hole. It's closed and non-orientable, so a symbol on its surface can be slid around on it and reappear backwards at the same place.You can't do this trick on a sphere, doughnut, or pet ferret -- they're orientable. the base webpage is pretty amusing as well. // ************************************************ // Selina, Birch, Dief, Sprite, Sand and Bear // missing Storm // http://www.cgl.uwaterloo.ca/~ssiu [Posted in FML issue 3775]