“Look at this brand new undershirt,” my wife said. “I am shaking it and shaking it but still I have this twist. Can you see what to do?”
I gave the undershirt a good shake. And another one. And one more. And then it struck me. It was a Möbius undershirt!
What a rare case in which mathematics can come to the rescue in domestic matters
“There is no way in the world this twist can be undone,” I said. “This is a mathematical fact! It is a Möbius undershirt!” My wife listened carefully to my firm statement.
I started to day-dream about the bright future of this rare Möbius undershirt: I will show her to my colleagues!, I will display her in public lectures, and even let some selected graduate students hold her. However, a few days later my Möbius undershirt disappeared. The open sewing machine may give a hint of what had happend.
Of course, I do not have a picture of a Möbius undershirt but only of an ordinary one. There is no way in the world an ordinary undershirt can be turned into a Möbius undershirt. This is a mathematical fact!