ABSTRACT
Exercise 4.9 What do you see when you look through the back wall of this three-manifold? What about the other walls? □
Imagine this new three-manifold to contain a jun gle gym like the one we built in the three-torus. This would be great fun to play in with a friend. Sometimes
when you ran into your friend he would be righthanded, and other times you’d find him to be lefthanded. You could play a special form of tag in which catching someone doesn’t count unless you can guess which hand is his left hand. Obviously there’s a big advantage for people who part their hair in the mid dle, and T-shirts with writing on them would be out of the question.
