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The foremost theory of the origin of the universe is the Big Bang theory. It suggests that the universe began several billion years ago in an explosion that caused it to expand, and to continue expanding. Some of the evidence for the Big Bang comes from studying the red shift of light received from distant galaxies. Telescopes allow us to observe the universe.
The Big Bang
Scientists have gathered a lot of evidence and information about the universe. They have used their observations to develop a theory called the Big Bang. The theory states that originally all the matter in the universe was concentrated into a single incredibly tiny point. This began to enlarge rapidly in a hot explosion, and it is still expanding today. This explosion is called the Big Bang, and happened about 13.7 billion years ago (that's 13,700,000,000 years using the scientific definition of 1 billion = 1,000 million).
The Milky Way galaxy is home to planet Earth
Astronomers have even detected a cosmic background radiation that is thought to be the heat left over from the original explosion.
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