In the inflationary Big Bang model, our universe is one of the many pocket universes in the multiverse. How can we detect the existence of the other pocket universes? I presumed that all the pocket universes exist in the same physical space. So in principle, they can exert influence on one another, gravitationally for instance. But if the expansion rate of the space between two pocket universes exceeds the speed of light, does that mean that the two pocket universes will cease to have any physical effect on each other? In other words, information about the other pocket universes is available in the past but not in the future. Does this result in a paradox?