Yes, the Big Bang is the name of a rock group. But more importantly, it is the name of one of the theories of the origin of the universe. It is a widely accepted theory, but also has been under some attacks recently.
When discussing the origin of the universe, there is always the confrontation between the theists and the atheists. Theists believe essentially that God created the universe, or at least some “Intelligent Designer” did. Atheists hold that the universe has been eternal and needed no Creator. This argument has raged for centuries.
However, due to more recent discoveries such as galactic motion and proton decay, scientists have come to believe with certainty that the universe, at some point, actually began. The final nail was the Second Law of Thermodynamics. Based on this, physicists feel that there are only two plausible explanations for the origin of the universe. First, someone made the universe (intelligent design) or second, the universe made itself (random chance).
The third option, favored by the atheists, that the universe has always been here, is too contradictory of empirical science. No other plausible theory has ever been proposed. The implications of this are wild, and have led to the proposition of the Big Bang theory, which, at its heart, is an atheistic theory.
We know that the universe did have a beginning. Before that, there was nothing…no time, space, matter, energy, nothing. The theory says that our universe sprang into being as a singularity some 13 or 14 billion years ago. We really do not know what a singularity is, because they really defy our current understanding of physics. They are thought to exist at the core of black holes, which are areas of intense gravitational pressures. The pressure is thought to be so intense that finite matter is compacted into infinite density. This is, of course, only a mathematic concept. These zones of infinite density are singularities.
Our universe is believed to have begun as an infinitely small, infinitely dense and infinitely hot singularity. We do not know where it came from, nor do we know why it appeared. The theory says that after the initial appearance, it inflated (the Big Bang, which may or may not have been an actual explosion), expanded and cooled, until the universe as we now know it existed. We do know that this expansion and cooling continues to this day, and is represented by the aforementioned Second Law of Thermodynamics.
There are some disquieting issues with this theory, at least to the non-Physicists. First, the singularity did not appear in space. Space did not exist before the big Bang and in fact, had to begin inside the singularity. Prior to the singularity, nothing existed. So, where did it come from and why? We don’t know. All we do know is that we exist within space and at one time it did not exist and neither did we.
There is some evidence for the Big Bang. As mentioned, the universe did appear to have had a beginning. It is also expanding, since we know that galaxies are moving away from us at speeds proportional to their distance (Hubble’s Law). Also, the discovery of cosmic microwave background radiation seems to indicate to some that it is the remnant of the heat that must have been produced by the Big Bang. Even the presence of certain light elements, like hydrogen and helium, are thought to be supportive of the Big Bang.
At the same time, there are other theories out there. Many come under the heading of Inflation Universe Theories, and currently there are about 50 of these being proposed and studied. But all of them are generally acknowledged to have their own problems, and will likely never be proposed and accepted as “the” answer.
As even with the Big Bang, it seems that the only way to get realistic calculations for any of the IUT models is to make assumptions that are not really justifiable. We can make certain observations and, based on the observations, make certain assumptions as to cause, then go about mathematically “proving” the theory. But, if the assumptions themselves are flawed, or the observable data are flawed to begin with, all we are doing is forcing the situation to conform to what we want it to be. This is not good science in general, and particularly not good physics.
In short, the Big Bang theory is not the best theory, it is just the currently most popular. Even the person who named it Big Bang, Sir Fred Hoyle, has now walked away from it. Others have begun to look toward Einstein and his static space-time paradigm as a means of dealing with the origin of the universe. Again, however, physics may not have advanced to the point where any truly plausible work can be generated.
George Ellis, a renowned astrophysicist, basically says that he and others believe that there is a range of models that could explain the origin of the universe. He can posit several that cannot be disproved based on observations. Yet, he himself admits that they are not sufficient, and can be excluded on philosophical grounds. And this problem of the philosophy of the scientist may in fact be something of the core problem.
Cosmology, or the study of the origin of the universe, is an area where science and theology meet head on. If one is predisposed to discount Creation as a “supernatural” event, then one would tend to ignore anything that did not or does not occur within the natural realm. But the “natural” realm is in itself the product of an event that took place outside of this natural realm. Recall the discussion of the singularity and how is suddenly sprung into “being” and in so doing created time and space and matter and energy. Was this “natural” or supernatural?
If the singularity existed before the universe existed or, put another way, existed outside the natural realm, what else is out there? What else may “suddenly spring into being”, who or what is determining this occurrence, and what caused the thing before the universe to exist?