sometimes i think about this too. when people ask me about how i think the world and everything was ceated i usually change my answer depending on my mood. most times i say
'maybe god did created the world and everything in it. god probably realised what a shit job he did (creating the world and everything in it) and then just walked away. he probably realised the mess he made and then fucked off. after all he did create us in his own image' lol
this does tend to shut people up.
I was in college with a lot of credits in math and science, but studying accounting when I set out to quit Catholicism. Three books whose titles I long ago forgot helped me:
1. a book that compared the various forms of Xianity,
2. a book that compared the world's major religions, and
3. a book that described the creation stories of many religions.
Realizing that I would never know the answers, I settled for agnosticism.
When I first learned of what's now called the Big Bang explanation, I asked "How do they know?" and decided that they didn't know.
Leaving Catholicism's certainties was like leaping into a void and, upon reading of existentialism, I decided that I have to assume responsibility for my actions.
After briefly considering suicide, I decided that my life is mine and started paying attention to what I wanted in life.
I graduated, found work I enjoyed and decided that religion is important to people who are unhappy.
Years passed and I quit agnosticism for atheism. I tell people so and don't try to convert anyone.
Believers sometimes ask me questions for which they claim to have certainty. I reply with a metaphor; I tell them that my knowing the answers won't help me pay the rent.
The universe? I'm okay with Buddhism's endlessly expanding-contracting explanation.
Yes, this does come to my mind too. This question needs to be answered only if you want to brcome an atheist helped only by science. Elsewhere, in one A N discussion, it has been shown that logic too can be used to lead to atheism. There are many questions that arise in one's mind about a supernatural power and if they are satisfactorily answered, then the question you ask becomes insignificant. I therefore often say that freeethought, rationalism, secularism finally lead one to atheism. This is how I myself have become a strong atheist. I think you are unnecessarily troubling yourself.
However, now to your question. The science has thus far found out how our universe came in to existance and how life evolved. Science must not be expected to give all answers at once. Scientific research is continuing and will continue for a long long time. Religions also have told us only about what they thought was our universe and it has turned out to be a hoax. Science has painstakingly put the truth before us. Who do you think will lead us to more correct answers in future? Someone who does not know who we are, where we came from, what is our universe and how it is? Can religion or their imginary god who are confused about everything tell us anything?
If there is a godlike power in this world, then only science can lead us to that power. That will a most elementary matter or energy source or a combination of both. It will not be, and evrything tells us that it cannot be, anything like the god described by any religion. It will be a scientific entity. Let us give science all the time it needs to tell mankind the final truth, even if it does not come in our times. Let us believe in science and give it a chance. That is more correct than to believe in ant purely imaginary and outrightly incorrect concept. Even if you become an atheist with such thoughts, you loose nothing because you have only stopped believing that truely is nothing.
Are you reading?
I haven't read any of the other comments here yet, so if I repeat any points then I apologise. First, I think that the universe isn't 4-5 billion years old, but somewhere between 13.5-14 billion years old. But, in all fairness, let's just ignore that mistake.
Now I turn to your question on where the universe came from. I am no physicist, but I would refer you to the law of conservation energy, which states "energy can be neither created nor destroyed. However, energy can change forms, and energy can flow from one place to another. The total energy of an isolated system remains the same." Perhaps I am wrong, but I think that it is pretty evidential that the cosmos (the term "universe" is somewhat inaccurate and cosmologists don't use this term very often nowadays when we're talking about this question). If we think about it this way, then the cosmos has always existed.
My own position, however, is that such a question is illogical in the first place. The main reason for this is that it seems to me to ask for the cause of something is to ask what other thing within the universe brought it about. Thus, the idea of cause and effect is only applicable within the cosmos. If we were to ask it about the cosmos itself, it makes no sense because it would be like asking "which point on Earth is north of the North Pole?"
I am far from being a phycist or any kind of scientist and so my answer may be wrong. Since the instant of the big bang, the universe has used enormous amounts of material and energy. Therefore the law of conservation energy alone may not be enough to answer the question.
Science offers some evidence as far back as making the big bang plausible. Nobody knows, what had been before.
So it is just a choice to either consider the big bang as a beginning and wonder, where it all came from or else assume an eternal process of matters in motion. I personally prefer the concept of eternity.
Nietzsche; did i spell that right? Ingersoll too.
You may be interested in reading a book called "Atheist Universe" by David Mills. In his second chapter, "Origins of the Universe" he goes into this question. It's written in a way that even a dummy like me can understand it. He covers a great many questions that skeptics ask. The answer to your question appears on page 76 of the 2006 edition of his book. I would quote it but it is too long. However, it basically says just what you said, that the materials have been here forever, just greatly condensed until the Big Bang.
Explanations differ from delusions.
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The big bang explanation is compatible Buddhism's endlessly expanding-contracting explanation. (A Catholic priest who'd studied mathematics devised the big bang explanation, and it happens to very closely match xianity's creation-from-nothing delusion.)
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When cosmologists started saying the big bang brought both time and space into existence, the explanation became a delusion.
This is a great question and, like the others have said, there really is no good answer yet. Maybe there never will be one. This could be the last of the gaps for god to fill. I know that it can be hard to accept a universe with infinite existence, no beginning and no end. But is it really any harder to accept than a god with no beginning or end?