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The Big Bang Theory, also called as expanding universe hypothesis. Edwin Hubble in 1920 provided the evidence that the universe is expanding. The galaxies move farther as the time passes. It says that galaxies are moving away from each other. The universe appears to be growing larger.
The Big Bang Theory:-
1. In the beginning, ail matter forming the universe existed in one place in the form of a ‘tiny ball” with an unimaginably small volume, infinite temperature and infinite density.
2. At the Big Bang “tiny ball” exploded violently. This led to a huge expansion. It is now/ generally accepted that the event of big bang took place 13,7 billion years before the present. The expansion continues even to the present day. As it grew7, some energy was converted into matter. There was particularly rapid expansion within fractions of a second after the bang. Thereafter, the expansion has slowed down. Within first three minutes from the Big Bang event, the first atom began to form.
3. Within 300,000 years from the Big Bang, temperature dropped to 4,500k and gave rise to atomic matter. The universe became transparent.
4. The expansion of universe means increase in space between the galaxies. An alternative to this was Hoyle’s concept of steady state. It considered the universe to be roughly the same at any point of time. However, with greater evidence becoming available about the expanding universe, scientific community at present favours argument of expanding universe.