@Jzyehoshua
"Then where did the molecules needed for the Big Bang come from?"
By molecules you probably mean the matter/energy required for the Big Bang, cause no molecules existed in the early times, only subatomic particles. The answer is simply we don't know. As I already said, matter and energy must have already existed in some form in order for the Big Bang to have occurred but our tools for understanding nature break down before the Big Bang. And no, that doesn't mean "God", it means that our understanding is not enough and perhaps it'll never be to answer all of our questions. The universe is under no obligation to make sense to us, but we try our best to understabd it anyway.
When one looks upon a great mystery such as "what was there before the Big Bang" and says "there must have been some sort of creator", he automatically assmumes the nature of the answer and takes pride in having explained the orogin of everything. Then stops the quest for answers thinking he already knows the truth is God. Science doesn't do that. It doesn't take pride in finding the ultimate truth cause we know that's not something realistic to achieve. Science is humble and honest enough to admit that we don't know and that's the very force driving it forward, constantly improving its current models as new information comes along, all in search of the actual truth, not the easiest explanation.
"Furthermore, why is it assumed that the Big Bang model is correct in the first place? How does one arrive at the conclusions that it occurred without assuming that the universe occurred through purely naturalistic processes? What evidence clearly indicates the Big Bang ever occurred to the exclusion of all other possibilities?"
I'll give you the short version of the story. Here's more observational evidence and in more detail if you want to read more about it: en.wikipedia.org/wiki/Big_Bang#Observational_evidence
There is a lot of evidence supporting the Big Bang but the most prominent one is the prediction of cosmic microwave backround radiation a few decades before it was actually observed.
Up until the 1920's people believed the universe was static and eternal. But then everything changed when observations from the Hubble telescope showed us that distant galaxies were moving away from us. If you're curious about how we can tell this, it's from a phenomenon called "redshifting". When an object is moving away from us, the electromagnetic waves it emits are streched by its velocity and hence their wave length increases making the light color change towards the "red" end of the electromagnetic spectrum. It's similar to how the Doppler effect works on sound waves changing the pitch of moving objects like sirenes: en.wikipedia.org/wiki/Redshift
From the observations, comparing how redshifted each galaxy was, it was clear that the further an object was, the faster its apparent recession velocity was. Objects were also moving away from each other following the same rule, not only away from us. This led scientists to conclude that the universe is in fact not static, but constantly expanding. Running time backwards, the further back we go, the smaller the universe gets and the denser and hotter the conditions inside it get.
When the Big Bag model was constructed, describing this expansion of the universe, experts said that there should be some light left over from that early initial state of the universe, like the one we see from the far away galaxies, but much older. Some ancient electromagnetic waves from the universe was in that extremely hot and dense phase and it should be detectable uniformly in all directions. But nothing was found and the theory didn't get much support.
As it turns out, the light form that early universe had been travelling for so long that its wavelength had been stretched (redshifted) by the expansion, way past the visible light range and gone way down to the microwave spectrum. Our equipment was not strong enough yet to detect such weak electromagnetic signals. It took us until the 60's to finally be able to detect it for the first time and it actually happened by accident by two random guys. Now we can clearly detect it in all directions as expected years before its discovery. That is one of many reasons that the Big Bang model became the widely accepted one.
en.wikipedia.org/wiki/Cosmic_microwave_background
The model fits all our observations and explains the phenomena we encounter through them, and all that was constructed years before we could actually view the evidence through telescopes. Does that mean it's perfect? No. It's just the best model of the universe we can create with our current understanding and it will be adapted and improved as we learn more about the world. Cause that's what science does, it embraces new information and constantly evolves, it doesn't cling to the explanation that seems more convenient to believe.
It really saddens me that despite all this amazing effort put by brilliant people, despite centuries of learning, observing and improving in order to be able to create a model that describes how our universe evolved over billions of years.... some people still choose the explanations humans had thousands of years ago, back when our understanding of the world was less than 1% of what it is now, undermining all the remarkable descoveries humanity has made since then.
"Then where did the molecules needed for the Big Bang come from?"
By molecules you probably mean the matter/energy required for the Big Bang, cause no molecules existed in the early times, only subatomic particles. The answer is simply we don't know. As I already said, matter and energy must have already existed in some form in order for the Big Bang to have occurred but our tools for understanding nature break down before the Big Bang. And no, that doesn't mean "God", it means that our understanding is not enough and perhaps it'll never be to answer all of our questions. The universe is under no obligation to make sense to us, but we try our best to understabd it anyway.
When one looks upon a great mystery such as "what was there before the Big Bang" and says "there must have been some sort of creator", he automatically assmumes the nature of the answer and takes pride in having explained the orogin of everything. Then stops the quest for answers thinking he already knows the truth is God. Science doesn't do that. It doesn't take pride in finding the ultimate truth cause we know that's not something realistic to achieve. Science is humble and honest enough to admit that we don't know and that's the very force driving it forward, constantly improving its current models as new information comes along, all in search of the actual truth, not the easiest explanation.
"Furthermore, why is it assumed that the Big Bang model is correct in the first place? How does one arrive at the conclusions that it occurred without assuming that the universe occurred through purely naturalistic processes? What evidence clearly indicates the Big Bang ever occurred to the exclusion of all other possibilities?"
I'll give you the short version of the story. Here's more observational evidence and in more detail if you want to read more about it: en.wikipedia.org/wiki/Big_Bang#Observational_evidence
There is a lot of evidence supporting the Big Bang but the most prominent one is the prediction of cosmic microwave backround radiation a few decades before it was actually observed.
Up until the 1920's people believed the universe was static and eternal. But then everything changed when observations from the Hubble telescope showed us that distant galaxies were moving away from us. If you're curious about how we can tell this, it's from a phenomenon called "redshifting". When an object is moving away from us, the electromagnetic waves it emits are streched by its velocity and hence their wave length increases making the light color change towards the "red" end of the electromagnetic spectrum. It's similar to how the Doppler effect works on sound waves changing the pitch of moving objects like sirenes: en.wikipedia.org/wiki/Redshift
From the observations, comparing how redshifted each galaxy was, it was clear that the further an object was, the faster its apparent recession velocity was. Objects were also moving away from each other following the same rule, not only away from us. This led scientists to conclude that the universe is in fact not static, but constantly expanding. Running time backwards, the further back we go, the smaller the universe gets and the denser and hotter the conditions inside it get.
When the Big Bag model was constructed, describing this expansion of the universe, experts said that there should be some light left over from that early initial state of the universe, like the one we see from the far away galaxies, but much older. Some ancient electromagnetic waves from the universe was in that extremely hot and dense phase and it should be detectable uniformly in all directions. But nothing was found and the theory didn't get much support.
As it turns out, the light form that early universe had been travelling for so long that its wavelength had been stretched (redshifted) by the expansion, way past the visible light range and gone way down to the microwave spectrum. Our equipment was not strong enough yet to detect such weak electromagnetic signals. It took us until the 60's to finally be able to detect it for the first time and it actually happened by accident by two random guys. Now we can clearly detect it in all directions as expected years before its discovery. That is one of many reasons that the Big Bang model became the widely accepted one.
en.wikipedia.org/wiki/Cosmic_microwave_background
The model fits all our observations and explains the phenomena we encounter through them, and all that was constructed years before we could actually view the evidence through telescopes. Does that mean it's perfect? No. It's just the best model of the universe we can create with our current understanding and it will be adapted and improved as we learn more about the world. Cause that's what science does, it embraces new information and constantly evolves, it doesn't cling to the explanation that seems more convenient to believe.
It really saddens me that despite all this amazing effort put by brilliant people, despite centuries of learning, observing and improving in order to be able to create a model that describes how our universe evolved over billions of years.... some people still choose the explanations humans had thousands of years ago, back when our understanding of the world was less than 1% of what it is now, undermining all the remarkable descoveries humanity has made since then.