We consider small and localized perturbations of a homogeneous equilibrium for the Vlasov-Poisson system in R^3. An old observation by Landau is that such perturbations have an unexpected mechanism for decay involving dissipation (in a time-reversible system!). We justify this in the special case of the Poisson equilibrium on R^3. This is joint work with A. Ionescu, B. Pausader and X. Wang.