This is a tough one.
Oh boy.
Now, as far as humans can grasp in our thinking, it is impossible for something to continue for ever and ever and infinity. Everything MUST have an end. Therefore the universe must end somewhere, right?
Okay, so, if the universe ends, what is on the otherside of the universe? Non existance? If its another universe, whats after that one? Another one? How is that possible, everything must have an end and therefore there can't be infinite universes.
Mind bogglah!!!