Explain The Big bang theory

The Big bang theory

Big Bang Theory is about the origin of Universe.
It suggests that about 1370 crore (13.7 billion) years ago, all matter and energy in the universe was concentrated into an area smaller than an atom.
At this instant, matter, energy, space and time were not existent.
It is also called expanding universe hypothesis.
Edwin Hubble, in 1920, provided evidence that the universe is expanding.
As time passes, galaxies move further and further apart.
Similarly, the distance between the galaxies is also found to be increasing and thereby, the universe is considered to be expanding.

Proofs of Big Bang

Expanding galaxies:

Hubble in 1929, noted that galaxies outside our own Milky Way were all moving away from us, each at a speed proportional to its distance from us.
He quickly realized what this meant that there must have been an instant in time (now known to be about 14 billion years ago) when the entire Universe was contained in a single point in space.
The Universe must have been born in this single violent event which came to be known as the “Big Bang.”

Cosmic Background radiation:

Those early photons – the afterglow of the Big Bang known as cosmic background radiation – can be observed today.

Stages in the development of the universe:

In the beginning, all matter forming the universe existed in one place in the form of a “tiny ball” (singular atom) with an unimaginably small volume, infinite temperature and infinite density.
At the Big Bang the “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 grew, 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.
Within 300,000 years from the Big Bang, temperature dropped to 4,500K (Kelvin) and gave rise to atomic matter. The universe became transparent.

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