
 NPCompleteness and Origami 
  NPcomplete problems have the property that every problem in NP can be converted into any NPcomplete problem, which means that if you could knock off one of these incorrigibles in polynomial time, you could use the same approach to solve all NP problems and make millions of dollars along the way. 
  The traveling salesman problem and several others are in a special corner of NP, called NPcomplete, which means that they are hard in a particular way. 
  The traveling salesman is in a class of problems, called NP for “nondeterministic polynomial time,” which may or may not be solvable in polynomial time, but whose solutions, once found, can be checked in polynomial time. 
 pr.caltech.edu /periodicals/EandS/articles/LXVII1/NPcompleteness.html (844 words) 
