The most used scientific model of the Universe is known as the Big Bang theory, which says the Universe expanded from a single point that held all the matter and energy of the Universe. There are many kinds of scientific evidence that support the Big Bang idea. Astronomers think that the Big Bang happened about 13.73 billion years ago, making the Universe 13.73 billion years old. Since then, the universe has expanded to be at least 93 billion light years, or 8.80 metres, in diameter. It is still expanding right now, and the expansion is getting faster.