I find the BIG BANG theory rather interesting. I am a scientist (major in chemistry and computer sciences) and approach every question analytically. As to the big bang theory, it is only a theory, just like evolution is a theory. There is no conclusive scientific evidence that can prove either of these theories and we are left to speculate and make "educated guesses". No one knows for sure exactly how the universe came into existence. Christians and other groups who believe in a divine creator attribute this creative event to God.
As for the theory that a ray of light caused the birth of the universe, this sounds like creationism to me (God created light before He created the Sun, Moon and stars – see Gen 1:3). You may say that if light started it all, then there couldn't be any matter at all. If you think that then your logic is flawed. You see light is composed of photons which are particles of matter, even though they have very little mass. Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific context, electromagnetic radiation of any wavelength. Due to the wave-particle duality of matter, light simultaneously exhibits properties of both waves and particles.
So matter has always existed. Conservation of energy law states that the total amount of energy (including potential energy) in a closed system remains constant. In other words, energy can be converted from one form to another, but it cannot be created or destroyed. Keep this in your thoughts as you read on.
There was a small independent study done over 25 years ago to find out if the human spirit had mass. They performed tests on several terminally ill human patients and on dogs, cats, and rabbits. It was reported that only the humans lost a small amount of weight when they died. Was this mass their spirit? For sake of argument let's say it was. The Bible says that humans (not any other animal) are created in God’s image and that God is a spirit and is NOT a man. (See Genesis 1:27; Numbers 23:19; Luke 24:39; John 4:24) If you follow this reasoning then we can say that God's spirit has mass and is a form of energy. Matter has always existed because energy cannot be created or destroyed; therefore God has always existed and always will exist. Energy can be changed into other forms of energy ... like nuclear for example. Could God have changed part of His own being to form dense matter and used light (photons) to orchestrate the BIG BANG? Whether or not He did is inconsequential for we are told by divine revelation that all things were created by and through Him (Colossians 1:16; John 1:3; Romans 11:36). His word makes it emphatically clear who created the heavens and the earth at the very beginning. (See Genesis 1:1)
The Bible says that God is so big that even the heavens cannot contain Him (1 Kings 8:27; 2 Chronicles 2:6), so it only stands to reason that there would be enough energy for God to use to make everything and have lots left over. I know that this sounds a bit simplistic, but often the simplest explanations are usually the correct ones. And if this idea of mine is relegated to that of a theory instead of fact, it is in good company … move over Darwin. :)
For further reference as to how big God and His creation is click here.