Much like skin on a person or the atmosphere that of the globe, there are barriers everywhere you look. Even down to smallest microscopic organism, there is a thin membrane that covers it to protect itself from outside forces. Staying within itself and not expanding beyond it's necessary space for its own well being. Even, the very things that make up life on this earth contain barriers of their own. The most infinitesimal thing in the known universe is an atom but it is really just a shell for a more smaller material called a nucleus. A direct consequence of two nucleus slamming at each other and breaking through their respective shells, or atoms, will lead to total catastrophe.