The topic of this paper is a defocusing semi-linear wave equation \(u_{t t}-\varDelta u=-|u|^{p-1} u\) in sub-conformal case in \(d\ge 3\) whose initial data come with a finite energy. We prove that almost all energy moves to infinity at almost the light speed as time tends to infinity. In addition, the inward/outward part of energy gradually vanishes as time tends to positive/negative infinity. We also prove some decay estimates of the solutions if initial data decay at a certain rate as the spatial variable tends to infinity. A combination of this property with a method of characteristic lines give a scattering result if the initial data are radial and in a weighted energy space.
