Science and religion are two sides of the same coin. They are both human attempts to explain the universe
Nope. That their apparent objective is the same (although I don't think it actually is), their methodologies are so far apart there's simply no way they can be considered related let alone two sides of the same coin.
Religion is presuppositional. It claims it has the answers and then tries to fit whatever evidence there is around it. Since there actually is no evidence, it invented a nifty little thing called "faith" as a way of hiding that embarrassing fact under the carpet. "Pffff...who needs evidence anyway? Just gotta have faith"! Interestingly, when some evidence appears to show up (although it never turns out to be compelling or even true) they are all over it like flies on a doughnut. So much for "who needs evidence", eh!
Science, conversely, is ALL about the evidence. It changes it's mind as the evidence changes and it's willing to go wherever it takes it - no matter what our personal thoughts on the matter.
All cultures observe the self same things and they explain them in their own way
So? This veers dangerously close to "Well, it's true for me".
Doesn't matter who explains what to themselves and in what way. They are either right or they are not. Science is the only thing that can tell us who is right and who is wrong. Not all "explanations" are equal.
Please explain to me why exactly you would expect to see evidence in this consciousness of things that de facto exist outside of it?
I have absolutely no idea what you mean here.
And assume you do know about the multiple universes theory?
Theory? No. Hypothesis, yes. Do you know the difference?
Have you given any thought to what lies beyond the known universe, what we are expanding into, etc.?
Yes. We're not expanding "into" anything. Space is a physical property of this universe, it's creating it within as it expands.
Possibility/probability of aliens?
Obviously the possibility exists. The probability is hard to determine since we are the only example we currently have of life within the universe. There is a famous attempt called The Drake Equation.
Dark Flow is another hypothesis.