The most popular argument regarding the origin of the universe is the BIG BANG theory also known as expanding universe hypothesis. Edwin hubble in 1920 provided evidence that the universe is expanding and galaxies itself are expanding, as time passes galaxies are moving further and further apart, the big bang theory contains following stages in development of the universe-
(1) In the beginning, all matter forming the universe existed in one place in form of tiny ball(singular atom) with an small volume, infinite temperature and density.
(2) before 13.7 billion years from now this tiny ball exploded violently, led to huge expansion, as it grew some energy was converted into matter, within 1st 3 minute from big bang event the first atom began to form.
(3) Within 300000 years from the big bang temperature dropped to 4500Kelvin and gave rise to atomic matter. The universe became transparent.
(4) Hoyle gave an alternative to above theory “concept of steady state”. It considered the universe to be roughly the same at any point of time.
But scientific unit favours the expanding universe theory.
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