Stephen Hawking, Albert Einstein, and Edwin Hubble are few popular of many scientists who have helped us develop every theory and conception about the origin of the universe through the scientific approach. Big Bang Theory is probably the most popular one among all others actually existing derived from many theoretical experiments conducted time after time. The origin of the universe has always been the point where scientific, religious, and philosophical conceptions meet in one place. However, in this discussion, we will only cover what he Big Bang Theory tries to explain; other perspectives from the different field will be excluded.
Before reaching deeper to the main topic, we should discuss what a theory really is from the point of view of scientific studies. Theory is a general knowledge where possibilities and probabilities are floating around. Consider gravitational theory, theory of relativity, Archimedes theory, and more; they are all likely to be leading to the proper or correct conception. Nevertheless, almost all kinds of theories are disprovable by new findings with new theories as well.
The Big Bang Theory is indeed famous, but surprisingly lacking of misunderstanding leads to misconceptions. Some people consider that Big Bang is an explosion; therefore, they think that the universe is originated from a single big explosion; well, it is not accurate. Big Bang Theory explains that the universe, which we accept as where we are now, began from expansion and it is still expanding now. From a very tiny dense state, universe is expanding to form what it looks like today. The theory does not try to explain what existed before the universe or things that exist outside of it. Once again, rapid expansion is the main discussion, not any sort of explosion.
Another question arises regarding the expansion. Will the universe expand forever or stop at certain moment in the future? According to another theory, the expansion depends on the amount of matter exists. Once again, however, that would be beyond the cope of this discussion.
Big Bang Theory emphasizes that the center of the universe does not exist. Universe in all points is the same, no centralized position. To come up with a solution to bring Big Bang Theory to our general conception of modern physics is very difficult. Plenty of new theories and laws, which did not exist or exist only within Earth, are sometimes disapproving greatly. Nevertheless, since Big Bang explains the evolution and expansion, some of other important physics discovery did not apply. Once again, we have to emphasize that Big Bang Theory tries to describe the development of the universe; it does not suggest any explanation what existed before universe, existence beyond the universe, and the shape of the universe. Although in some ways some answers can be found according to the theory, they would be new things that do not change what Big Bang has already stated.
After all, Big Bang Theory explains what it explains; the universe is expanding. Other possibilities that might just arrive based on this theory will not change anything to this expanding model. If other theories discussed the origin of the universe or anything that Big Bang does not explain, they should be separated from Big Bang itself.