For starters, the universe cannot possibly exist WITHOUT a God or all powerful eternal entity. And the reasoning behind that is both totally logical and scientific as well.
I'll use energy as an example...It is all around us. It is literally intertwined with everything in the known physical universe.
Science says that energy cannot be created nor destroyed within the physical universe. That means that energy is technically infinite, or eternal; unlimited. Now, the implications of that statement alone are massive. If energy is eternal, and it has no known origins in the PHYSICAL universe, then its origins must exist OUTSIDE of our known physical universe. Energy must have an infinite source if it's properties are eternal.
Now, if we've established that the origins of energy must exist outside the realm of the physical world(gravity, time, physics in general, etc.), we can also use reasoning and logic to apply attributes to this energy source.
We can assume that this energy source is:
-Intelligent- Because we can observe intelligence in human beings and creatures on the Earth.
-All powerful- Energy is eternal. The same entity that created energy(which is eternal) has an infinite supply of power at its disposal.
-All knowing- The world and it's physical properties are vastly complex. DNA, RNA, the human brain, body structure, cell mechanisms, animals, the ecosystem, the atmosphere, etc., all scream of complexity and design. The same entity that made all these things and set energy in motion must also understand what it is creating in order for it to work like clockworks. Physical laws all have to be applied to the universe as it's created, which furthers the notion that an insane amount of understanding is required to complete such a task.
Many people may ask,"Well, how do I learn about this God? Or what authority or proof do you have of His nature, His actions, etc."
My answer to that would be read the Bible. If you refuse to read the Bible because you believe that it is full of "inaccuracies and fallacies" of logic, I would suggest you take a closer look.The Bible has more than enough proof of God's understanding regarding the universe and the laws He created to govern it.
For instance, in Genesis, God told Abraham to circumcise all the males in his house who were 8 days old, as a token of the covenant between God and Abraham. Now, the interesting part about that is that we have a blood clotting agent in the human body known as vitamin K (techincally speaking, prothrombin). From the fifth day on, the level of prothrombin in the body is high enough to allow for fast enough clotting that a circumcision can be safely performed. Vitamin K levels reach 100% on the seventh day, but on the eighth? It reaches a whopping 110%. On the ninth, it drops back to 100%. Now how on Earth would a bunch of "ancient people" just KNOW that? Obviously, they didn't just use trial and error. That would practically be genocide....
Well...okay...Maybe genocide is a bit of an exaggeration, but honestly? They didn't even have the tools necesary to make accurate guages and conclusions for such a delicate task. No, trial and error is not the case.
The logical assumption would be to conclude that the same God who created the universe knew PRECISELY what was going on. That's only one example, of course. I'm just saying, I believe science will always point to the creator.
Oh, I read a response on this page that made me laugh because of the illogical idea presented in it. Here is what he/she/it said:
"If we were created by an all powerful being, He..She.....It, made some big time mistakes.
"Oh! Lord! How can you blame us
naked and cold with blood on our feet
thirsty and hungry we're starving and weak
to walk down this path laid by your hand
lined it with evil, chaos and greed
painted with lies designed to deceive
controlled by the evil one's power and greed
are we pay'n for a sin done on the cross
a new generation is already lost."
Now, this is going to tie in to WHY the universe was created, but for now, I'm going to point out the obvious flaws in the above statement.
The user is blaming God for "lining the our world with evil." In other words, he/she/it is suggesting that we should not be held responsible for our actions as individuals, but rather, it's all "God's fault."
This is clearly not the case.
For one thing, there is this thing called "free-will," or our ability to make decisions and act on our own. We are therefore responsible for our own actions.
That is why rapists and serial killers are thrown in jail.
Sin must be punished, and sin must not be tolerated(however, society today would like to tell you that you're a product of evolution. Simply put, you're just an animal, and you should do what you want to without fear of consequences, because there is supposedly "No God"). Sin, or evil, has consequences. You don't have to be all spiritual to understand something that simple. Even atheists know that (whether they call it "sin" or an "un-wise choice").
Now, someone might say God made a mistake by allowing evil to exist, but is that really the case? Is God really a devious, execrable, unloving entity that enjoys watching humans suffer? The answer is no. And the logic that supports that answer is sound.
The fact of the matter is that God allowed evil to exist because He loves us. This may seem insane or illogical, but think about it carefully before you make a hasy(and stupid) assumption.
For one thing, how can humans love God is they don't have free will? In order to TRULY love God, we need to be able to CHOOSE Him. Not act like robots that simply obey all the time. The only alternative to an all knowing, perfect, and HOLY God, would be precisely the opposite of that...Which is called Evil.
Now, if you understand the basic attributes of perfection, you realize that it cannot be tainted...Cannot be changed. That which is perfect REMAINS perfect.
Now, Adam(the father of mankind) sinned and brought evil upon a perfect world. You might ask why such a seemingly trivial act would cause the entire universe to become tainted with evil. The answer is simple; it is because God is Holy. Anything that sin touches, God cannot abide in. So naturally, if something is dying, you can assume that it has lost it's energy...It's life.
It's like a light-bulb...When it begins to separate from its power source, it naturally begins to die. There's no more light. And that is precisely what happened to our universe. The energy(God) could not abide with something that was less than perfection, so it left. We now had a sinful, evil infested world because of the actions of a single human being...Man's nature immediately became evil...Fleshly desires were mankind's nature. Death became a reality physically, and spiritually as well. Because of sin, souls were marked for eternal torment after, because God cannot abide with sin. Sin offerings and staying cleansed were the only ways to appease God's wrath for mankind's evil.
HOWEVER, God loved the world so much, that He sent Jesus to Earth to die as a replacement for us. Jesus was literally the incarnation of perfection. He went through the worst pain humanly possible, and died on a cross to bear our sins. Jesus is the way to eternal life...He is the way to escape Hell.
His sacrifice is a declaration of His love for us.
Essentially, the answer to "why does the universe exist" would be this:
He loved us enough to give us our sense...Sight, smell, hearing...everything. He wants us to love Him...He wants us to love perfection...To love Holiness, and to strive for Him. Everything He's ever created was meant to point at His mastery of time...Of space, of knowledge. He created the world and all the people in it to LOVE Him.
Love is really the reason for the existence of the universe.
That's all I have to say about that...