It is not NP != P that is proposed as a physical law. It is the impossibility of building computers that quickly solve NP-complete problems. It is really more like a heuristic to quickly shoot down some physical theories. The 2nd law is a bad metaphor. The impossibility of faster-than-light communication is a better one. If your proposed physical theory makes faster-than-light communication possible, that makes the theory look suspicious. Analogously, if your proposed physical theory makes solving SAT feasible with a polynomial amount of resources, that should make the theory look suspicious, says Aaronson.
EDIT: As an important example, the possibility of general time travel could make you solve SAT easily. It is a nice exercise to figure out how. Harry Potter tried it in Methods of Rationality, and Aaronson has a whole lecture about it.
I totally agree. I guess you could imagine Maxwell's demon as an example where untangling a supposed violation of the 2nd law led to new understanding.
Many experts suspect that there is no polynomial-time solution to the so-called NP-complete problems, though no-one has yet been able to rigorously prove this and there remains the possibility that a polynomial-time algorithm will one day emerge. However unlikely this is, today I would like to invite LW to play a game I played with with some colleagues called what-would-you-do-with-a-polynomial-time-solution-to-3SAT? 3SAT is, of course, one of the most famous of the NP-complete problems and a solution to 3SAT would also constitute a solution to *all* the problems in NP. This includes lots of fun planning problems (e.g. travelling salesman) as well as the problem of performing exact inference in (general) Bayesian networks. What's the most fun you could have?