Man has always wondered how the Universe originated. A number of theories have been put forward to explain its origin.
According to the Big Bang theory, the Universe is the result of an explosion called the Big Bang. This explosion occurred about 14 billion years ago. When the Big Bang happened, it let loose a huge amount of energy. This energy keeps the Universe expanding. This expansion is likely to continue for another 50 billion years.
Some other scientists, who propagated the Steady State Theory,' believe that the Universe has no beginning or end.