Write a short notes about big …

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 further as the time passes. It says that galaxies are moving away from each other. The universe appears to be growing large. The Big Bang Theory: (a) In the begining all matter forming the universe existed in one place in the form of a 'ting ball' with an unimaginably small volume,infinite temperature and infinite density. (b) At the big bang exploded violently. This led to a huge expansion. It is now generally accepted that the event of big bang took palce 13.7 billion years before the present. (c) Within 300,000 years from the big bang, temperature dropped to 4,500k and gave rise to atomic matter. The universe became transparent.