Oh, my, there is all kinds of stuff going on in this thread.
Of gods, demons, and the supernatural (what is it?)First off, yes, all of these concepts of gods and demons came from a time in humanity's past where rationality and scientific ability were not yet dominant in our collective consciousness. And, indeed especially in reflection on a great number of things lately, I can confidently say that while a lack of alternatives in our ability to find solutions for the problems we face in life allowed these ancient impulses to drive us to either discover or create these concepts and beings, as your individual beliefs dictate, the benefit of such constructs in our lives is still discernible to us, even in this age of rationality and scientific thought. In other words, we came to these beliefs when we could not explain the world around us, but now that we can, we still benefit from the belief in a number of ways (primarily through very subtle things like having a positive outlook on one's present safety and future possibilities, and giving additional structure to moral codes).
Secondly, it is a great debate amongst the religious as to whether or not the divine has any real ability or interest in acting directly on our world. Certainly, from the two-sided concepts of God versus Satan or Good versus Evil, there is not only work to be done, but a definable arena where that work takes place - our world. And yet, atheists would contend that they see neither a greater plan, nor any true evidence of a guiding force, in the events that unfold around them.
Thirdly, considering for the moment that the supernatural does indeed exist, it is clear from what we know of them that, regardless of the direction of creation (us in their image, or they in ours), they share much with us in terms of the kinds of goals and methods that make up our perspective on the universe around us. This means that they are inherently understandable, at least in part, and their will is compatible with ours. Furthermore, a well adjusted personality will be able to see the positive in the world and not only recognize it for what it is, but consciously align themselves with that good, to the best of their ability.
There's more I want to add to this, but I will have to come back to it, I am falling asleep.
Why does God let bad things happen?Well, the absolute best explanation I have seen for that situation goes quite simply like this:
God gave us Free Will.
Free Will means that we have the ability to choose between good and evil.
God loves us, and will never take that Free Will from us.
Thus God cannot stop us from creating or supporting evil, by his own rules.
On the death of the universeIt is logical truth that barring a "Big Crunch", the only other alternative is the "Heat-Death" of the universe. Consider this train of logic:
1) Stars make energy by
nuclear fusion - by taking the abundant Hydrogen created in the earliest moments of the universe and combining them into ever bigger and bigger elements.
2) Once so combined, the total sum quantity of material available as fuel for this process, in the whole of the universe, goes down. Once the Hydrogen becomes Helium, much less anything heavier, it is gone forever.
3) Barring matter being created or inserted into our universe through either an outside force, or a process that we have yet to even imagine, we cannot increase this supply of basic raw material.
4) Considering the expansion of the observable universe - where it is clear that the universe is expanding, and indeed is accelerating in its expansion - such raw materials, even if they could be found, would be harder and harder to get to, much less collect together to put to use, as time wears on.
5) The progression of elements through the process of fusion has a calculable end, where the energies required to continue the process fail to sustain fusion past iron, meaning that not only is the base material finite, the process as a whole is working its way to a definable end.
6) Moving on from the specifics of stellar function, the planets that surround each star get most or all of their heat from their star. Our planet may have a molten center, but it is the sun's warmth that sustains us on the surface. Without heat from a blazing sun, a planet is a cold and lifeless thing.
7) Add all of this together, and it can be imagined that there will come a point where there is no fusable material left in the universe, and thus all the stars will have gone out, and lacking their heat, the whole of the universe will cool into a frozen lifelessness for the rest of eternity.
Of course, all of this is trillions or quadrillions of years from now, so don't get all fatalistic over it. We have billions of years before our own sun gets far enough along in its life-cycle that we have to leave our system forever (and I DO hope that we are out and about in the galaxy/universe by that point).