The Big Bang Theory

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It is always a mystery about how the universe began, whether

if and when it will end. Astronomers construct hypotheses called

cosmological models that try to find the answer. There are two

types of models: Big Bang and Steady State. However, through

many observational evidences, the Big Bang theory can best

explain the creation of the universe.

The Big Bang model postulates that about 15 to 20 billion

years ago, the universe violently exploded into being, in an

event called the Big Bang. Before the Big Bang, all of the

matter and radiation of our present universe were packed together

in the primeval fireball--an extremely hot dense state from which

the universe rapidly expanded.1 The Big Bang was the start of

time and space. The matter and radiation of that early stage

rapidly expanded and cooled. Several million years later, it

condensed into galaxies.

The universe has continued to expand,

and the galaxies have continued moving away from each other ever

since. Today the universe is still expanding, as astronomers

have observed.

The Steady State model says that the universe does not

evolve or change in time. There was no beginning in the past,

nor will there be change in the future. This model assumes the

perfect cosmological principle. This principle says that the

universe is the same everywhere on the large scale, at all

times.2 It maintains the same average density of matter forever.

There are observational evidences found that can prove the

Big Bang model is more reasonable than the Steady State model.

First, the redshifts of distant galaxies. Redshift is a Doppler

effect which states that if a galaxy is moving away, the spectral

line of that galaxy observed will have a shift to the red end.