The world of theoretical physics, the universe and how matter behaves in space is complex. There's a lot of math involved but the questions even non-physicists want answered surround the issues of big the universe is, is it continuing to expand or it coming in on itself and how is this all happening. The short answer? It's complicated. The ancient Greeks wondered if it was infinite going on forever, or did it end somewhere with a hard edge. Newton thought it must be infinite, otherwise the laws of gravity would mean that it would all come crashing in on us. Einstein weighed in during his time, saying that it was static, because in his math, there had to be a constant.
Edwin Hubble came along and measured the shift in the frequencies of light coming from distant galaxies and wrote a paper that explained how the universe was an ever expanding entity. But exactly how does it expand? If it were going off irregularly, eventually it could stop or collapse, however recent research shows it's expanding in an orderly and symmetrical way, making it isotropic. And it's going pretty fast as well, with galaxies getting further away from each other. So where's it going? Everywhere, in all directions. Because it's happening so fast, no matter where humans could go, no matter how far or fast, eventually, we'd get back to where we started. Physics, no matter where you go, there you are.