The Big Bang
...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.
The faster the galaxy moves, the more shift it has. If the galaxy is moving
closer, the spectral line will show a blue shift. If the galaxy is not moving,
there is no shift at all. However, as astronomers observed, the more...
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