Evidence Favouring the Big Bang
One piece of evidence comes from the expansion of the universe which we have already described. The expanding universe suggests that the matter was packed much more densely in the early stages of the universe. The proof for this also comes from the distant objects quasars. When we 'look' at quasars situated 6 to 8 billion light years away, wc are looking at them as they existed then. If the universe were more dense in that epoch, we should be able to sce some evidence of that density in the quasars. We do see such high density among thc quasars. Another substantial hit of evidcncc for the Big Bang theory comci from thc cosmic background radiation.
For many years the astronomers believed that if there was a .cosmic explosion long ago, radiation from that event should still exist within the universe. This radiation may be weak, it may have lost its energy due to the expansion and cooling of the universe, but it should exist. Radio-astronomers have, indeed, discovered faint signals-a constantly present background radio noise that pervades allspace.
Calculations done by astrophysicists show that this radiation, called the cosmic microwave background radiation, is a relic of the ancient past when the universe was inits first throes of creation in the Big Bang. An additional discovery made by astronomers in the past two decades is that of the primordial abundance of elements, i.e. the elements hydrogen and helium first createdin the aftermath of creation are found to be most abundant in the universe.
By examining the light coming from the various parts of the universe, astronomers have found out that, out of every 100 atoms, almost 93 are hydrogen atoms and seven are helium atoms. Elements heavier than helium are present in traces only. This suggests that the universe started out with a Big Bang from a very hot and dense state and quickly cooled as it expanded. The hot and dense conditions lasted long enough for some hydrogen to fuse into helium. But they did not last long to allow other heavier elements to form in significant amounts. These were made much later in the interior ofmassive stars.