I will present recent joint work with Jonathan Luk (Stanford), where we develop a general method for understanding the precise late time asymptotic behavior of solutions to linear and nonlinear wave equations in odd spatial dimensions. In the setting of stationary linear equations, we recover and generalize the Price law decay rates. However, in the presence of a nonlinearity and/or a dynamical background, we prove that the late time tails are in general different(!) from the better-understood case of linear equations on stationary backgrounds. I will explain how this problem is related to the problem of the singularity structure in the interior of generic dynamical vacuum black holes.