The origins of the universe
Scientists believe that the universe began in a hot 'big bang' about 13,700 million years ago. The universe continues to expand. Stars do not remain the same but change as they age. The evidence for the Big Bang Theory includes the existence of a microwave background radiation, and red-shift.
The universe contains extremely dense objects, called black holes, and may consist mostly of dark matter that cannot be seen.
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 about 13,700 million years ago 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.
Gravity is slowing down the rate of expansion. It is possible that the universe may expand for ever, or it may stop expanding. It may even contract and become very small again - the 'Big Crunch'.
There are other scientific theories for the origin of the universe. For example, the Oscillating Theory suggests that this universe is one of many - some that have existed in the past, and others that will exist in the future. When the universe contracts in a Big Crunch, a new universe is created in a new Big Bang.
The Steady State Theory suggests that as the universe expands new matter is created, so that the overall appearance of the universe never changes.
NB Sometimes the age of the universe is given as 13.7 billion years. This is because In scientific terms 1 billion is defined as a 1,000 million.
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