  We prove that solutions to the quintic semilinear wave equation with variable
coefficients in $\mathbb R^{1+3}$ scatter to a solution to the corresponding
linear wave equation. The coefficients are small and decay as $|x|\to\infty$,
but are allowed to be time dependent. The proof uses local energy decay
estimates to establish the decay of the $L^6$ norm of the solution as
$t\to\infty$.
