P versus NP problem
And so far, for the hard problems, the solutions have required on the order of  computations. For any particular problem, people have found ways to reduce the number of computations needed. One might figure out that a way to do just 1% of the worst-case number of computation and that saves a lot of computing, but that is still  computations. And every extra rock still doubles the number of computations needed to solve the problem. There are insights that can produce methods to do even fewer computations producing variations of the model: e.g. . But the exponential function still dominates as  grows.