Big Bang Theory
...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 distance a...
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