I believe that years ago the universe was one giant atomic mass. In the center was the burning core that heated the atoms, causing them to vibrate which produced more heat. Eventually the mass overheated, causing a cataclysmic explosion. Creating the galaxies we know today. The galaxies are slowly moving out and apart from each other, and eventually there is still the center of gravity where the atomic mass was. And eventually the gravity will pull the galaxies together again, restarting the cycle. I call this theory the Universal Breathing Process (UBP).