According to the bing bang theory,between 10million to 20 million years ago,the universe began froma cosmic explosion at a single point. The exact time, location and size of that initial super-powerful explosion can not be determined because that cataclysm created space and time, as well as all the matter and energy the universe will ever hold. The early universe was extremely small, dense, and hot. For the first fraction of a second, only energy existed. It has since been expanded in all directions and has evolved from a primordial dense and hot state in a finite time in the past and continues to grow until today. As the universe expanded and cooled, the four fundamental forces (gravity, electromagnetism, and the strong and weak nuclear forces) became distinct.