"Inflation holds that our universe experienced a sudden burst of rapid expansion an instant after the Big Bang, blowing up from a infinitesimally small speck to one spanning a quarter of a billion light-years in mere fractions of a second.
Yet inflation, once started, tends to never completely stop. According to the theory, once the universe starts expanding, it will end in some places, creating regions like the universe we see all around us today. But elsewhere inflation will simply keep on going eternally into the future.
This feature has led cosmologists to contemplate a scenario called eternal inflation. In this picture, individual regions of space stop inflating and become “bubble universes” like the one in which we live. But on larger scales, exponential expansion continues forever, and new bubble universes are continually being created. Each bubble is deemed a universe in its own right, despite being part of the same space-time, because an observer could not travel from one bubble to the next without moving faster than the speed of light. And each bubble may have its own distinct laws of physics. 'If you buy eternal inflation, it predicts a multiverse,' Peiris said."
Even if the neighboring universe is just a void, if this proves to be true then the existence and knowledge of multiverses will change our bubble forever.