HOW IT ALL BEGAN It turned out that our Earth is already an old lady. About 13.8 billion years ago, there was a big blown in biblical proportions. The British call it the Big Bang. The theory of how our world began. Since our universe continues to expand at a speed of 735 kilometers per second, scientists came to the logical conclusion that it was once a small clump of matter with infinite density and temperature. Small clots exploded and began to expand and thus spawned our entire universe.