If the universe is expanding. What is it expanding into?
You'd have better luck asking a rock than getting the correct answer from any of the odd 6 billion people inhabiting this planet. We can't even understand what the universe is, little own what exists outside it. Besides even if an intelligent being who's billons of years more advanced than us and knew what existed outside the universe came down to earth and tried to explain it to us, is there anyone out there that is actually that ignorant that they think they would be able to condemplate it?
You'll send yourself insane if you spend too much time thinking about it. Better of wondering about questions that have a possiblity of being answered, by that I mean the mystery of what's in the universe, which at the moment (for the most part) is just as much a mystery to us as what exists outside it. Before i start wondering about what exist outside the universe I want to know if Europa has a liquid water ocean under the ice layer or how common are rocky planets and life in the universe (intelligent or single celled) just to name a few.
Just for fun though, I've always been fond of the idea that the universe is just some sought of power plant for a more meaningful reality, and life is simply a useless byproduct of it.