There is a joke that goes like this: A mathematician and an engineer attend a lecture on the 11-dimensional M-theory. At the end of the lecture the mathematicia

There is a joke that goes like this: A mathematician and an engineer attend a lecture on the 11-dimensional M-theory. At the end of the lecture the mathematician delighted says how much he enjoyed it. The engineer puzzled asks him how anything even makes sense. The mathematician replies "It's easy. Visualize an N-dimensional space, then let N go to 11."