When we observe the universe on the scale of the naked eye, it appears to be continuous and governed by physical laws. That is, we can divide matter and time as finely as we wish and describe their behavior via physical laws, which we have discovered. At one time it was believed we could extend this concept without bound. In other words, we could observe and make discoveries about the universe at smaller and smaller -- as well as larger and larger -- dimensions of time and space.
However, the universe behaves differently at very small scales, as described by Quantum Mechanics. And as its name implies, Quantum Mechanics involves describing the universe in terms of "quanta" or units. For example, electrons within an atom cannot change position in a continuous manner the way planets within a solar system can. Rather the electrons can only be in quantified mathematical states and can only "jump" from one state to the other. Further, while the precise position of a planet can be determined, the position of an electron can only be given in terms of probabilities. And the mere act of measurement affects the probability.
At small enough scales, there is no way to observe the universe or test theories. Although String Theory postulates that, at scales much smaller than subatomic particles, the universe is composed of a variety of energy loops or strings, this cannot be observed, tested, or proved. The smallest unit (quanta) of time is the Plank time of 10-43 seconds. The universe jumps in time via Plank units. For example although the universe began at time 0, it is not observable until time 10-43 seconds.
This behavior of the universe, which was discovered in the 1920s (Quantum Mechanics), was unexpected and sparked a debate among scientists and philosophers. How can the universe be quantified and described by probabilities rather than precision? How can we be unable to observe and understand it beyond a limiting factor? It is similar to our inability to observe and understand the universe before the Big Bang. Just like String Theory, there are theories as to what went on before the Big Bang, but we will never be able to observe or test these theories.
Now consider a digital picture. Although a high-resolution digital picture looks continuous, we know that it is made of megapixels. As we zoom in on the picture, it becomes less and less precise, until we see the individual pixels. When one pixel fills our field of view, the picture no longer has meaning, and it is pointless to subdivide the pixel. Looking at the entire picture again, it makes sense to describe a location precisely in x and y. For example we may say a point is a x=2.319 inches and y=3.472 inches. But when we zoom in far enough, it only makes sense to talk in terms of individual units. For example, we would say a point is at x=21 pixels and y =87 pixels.
The picture has no exact meaning at fractional pixels. However, the color and intensity of surrounding pixels may be averaged to give values (color and intensity) at a fractional pixel. But this is only an approximate or probable value. Is this starting to sound familiar? Just as a digital picture has a limiting resolution, so too the universe has a limiting resolution. In the case of the digital picture, the limiting resolution is described in terms of pixels, and in the case of the universe, the limiting resolution is described in terms of Quantum Mechanics.
Just as it does not make sense to subdivide a pixel, it does not make sense to subdivide the universe beyond what can be observed, tested, and proved. It is impossible to observe the universe beyond the limits of Quantum Mechanics. And String Theory can never be proved. Even so, how would we subdivide the strings? We cannot know or observe the universe at very small scales of time and space, because we have exceeded the resolution -- or bounds -- of the universe. In the same way we cannot know or observe the universe before the Big Bang, because we have exceeded the start -- or beginning bounds -- of the physical universe. (Also of note, the universe will "die" through the process entropy.)
Both the Big Bang and Quantum Mechanics represent limits, beyond which we can no longer explain the universe via our observations of the physical universe: there is no underlying physical cause. It now becomes a philosophical and religious question: is there a supernatural creator (or are there supernatural beings) that supersedes the physical universe as "first cause"? Is it valid to use the scientific method to search for such answers?
The universe can be observed and the natural laws can be understood. If we observe circumvention of the natural laws, we have observed the supernatural, and the natural laws can no longer be considered "first cause." This is why miracles are so important. However, it is a passionate issue and difficult to look at objectively. So while many Christians replace obvious scientific fact with their own grossly distorted picture of the natural world (various forms of Creationism, including Intelligent Design), many secular scientists refuse to consider the possibility of anything existing outside of the natural world. They search for a "theory of everything" and try to explain the universe beyond its bounds. For example, String Theory is quite convoluted, with many dimensions, etc. It is similar to theorists who tried to save the Ptolemy (circle) theory of planetary motions (as opposed to the true elliptical motions), by putting circles on-top-of circles, etc.
"Science without religion is lame, religion without science is blind." -- Albert Einstein
There is ample miraculous evidence for the existence of God (including the Born Again experience), and both the Big Bang and Quantum Mechanics point to a finite, designed physical universe, which cannot be an end in itself. The universe did not create itself, just as we did not create ourselves. This of course points to a supreme being, God, as creator. So where did God come from? He didn't come from anywhere. He is outside of time, space and the universe. There are seemingly only 2 possibilities: (1) absolute nothingness and no God, or (2) existence and an infinite God.
However, there is much evil in the universe. In fact its very nature is evil. For example, when a massive earthquake occurs, causing great suffering, it's simply a natural consequence of physical law. So too the process of evolution, with the suffering and death of animals via competition, is only the universe following natural physical laws. Therefore either God created a fundamentally evil universe, or something more is going on.
If we assume God is good, then He must have created -- before the creation of the material universe -- very powerful spiritual beings (angels), some of whom turned against Him, became evil, and perverted the universe. Therefore, the perversion of the universe and perhaps the very existence of the material universe are the result of the fall of Satan and his angels, before the Big Bang.