Is there one universe or is there more than one?

Well, (and my tech ed teacher told me this), for every star, there are 10 planets. So if there is 10 planets in each star, i don't think that we're the only planet with life on it.

No one knows and probably never will. Some people believe there are multiple universes, possibly an infinite number of them. Co-existing but not touching. Every time a decision is made is a branching point. Make a choice and the future plays out one way. Make another choice and a different future will happen. Consider how many decisions are made every day by everyone and consider how many possible futures there might be. Infinite is the only Word that even begins to cover that.