Leenu

The universe expands faster than the speed of light. Increasing the distance between celestial objects to a point where light from an object will never reach the other object because it looses all it's energy. But the pockets of the universe where gravity beats the expansion of the universe, gravity is pulling mass together. In some million years, our galaxy will collide with the andromeda galaxy. 

Still with me? Well this is where my two cents come in. You see, when matter is gathered into a smaller volume, the the matter becomes dense. This is essentially how black holes form. If all matter in a pocket of the universe keeps getting closer and closer, it will become denser and denser. Overtime, this pocket will become infinitely small and infinitely dense and infinitely hot. You know what else was infinitely small and infinitely dense and infinitely hot? The thing before BIG BANG! So I think that, when a universe is created, dense pockets of gravity form which are seperated from each other, then these pockets become super dense and create a new universe. Which means parallel universes most likely exist. But we can not detect their existence due to how far they are.And not only is our universe expanding, it is possible that the multiverse is expanding. Like a tree that grows branches, and those branches grow branches. An insect on a branch might think that just it's branch is expanding. But in reality the whole tree is growing.