The arrow of time appears to be pointing in one very specific direction. Natural processes, from rivers flowing downhill, never uphill, to eggs always breaking, never spontaneously reassembling, to cups of coffee always cooling down, show us that direction.  Yet the laws of physics that govern the motion of all matter are time-symmetrical: they don’t distinguish between past and future. What give time’s arrow its direction is the initial conditions of each situation: an orderly state of affairs which then disintegrates into a disorderly state. The question then is, what was that original orderly state of the entire universe, giving the whole of time its direction, asks Paul Davies.