The Big Bang

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...