I think I'm in love with you.

I think we could have a happy life together.

One cannot prove a negative (http://mcooki.es/182369). But I'll try my best in this response and I do not ever claim to speak for someone else:

The young Earth nonsense of our planet being only 6000 years old is enough. The Biblical concept that the Earth is flat and the center of the Universe is another. I've seen no double-blind studies where prayer to God has been proven effective. Many religions counter each other with their accounts of who gets to go to their fantasy story of an afterlife.

I could go on and on and I have challenged many to provide the slightest bit of proof otherwise. Silence. Always. Silence.

Before I dive into the meat of your question, allow me to clarify a few things. First, there are two types of evidence: I will call them positive evidence and negative evidence. Positive evidence in the presence of data that either implies or demands certain events. For instance, us falling back to earth when we jump, instead of flying off into the sky, demands that a certain force must be attracting us back towards the ground. Negative evidence works inversely: a murder investigator who finds no traces of gunshot wounds on a body will conclude that a gun was not the cause of death.

The second thing I would like to identify is the word atheism itself. Dissecting the word reveals it to be a negative state: A (not) THEIST (proponent or believer in a god or gods). I might like to call this negative state “default state” meaning that it is the state a human mind defaults to, after considering positive state theism and rejecting it. Inversely a mind that accepts theism becomes positive state theist. With me so far?

Now, for your question. Without going into too many details (I'll leave the deeper investigation to you) the universe exists, with or without a god. This much is proven, just look around you; it's there. Now, because of advancements made in physical sciences recently, we have also proven that nothingness (As in true nothing; timeless, exo-universal nothingness) has properties that demand something exist. It more specific terms, it is well proven that life exists independently of a creator; stars exist independently, planets, rocks, photons, you name it. It all has been shown to be capable of existing on its own. Now as you may have guessed, all this positive evidence does not prove that a god (or gods) does not exist, nor can it. To say so would be an oxymoron. That said, it does prove that a god does not NEED to exist. It proves that the universe does not NEED a god or gods. Occam's Razor allows us to cut all gods out of the equation right now, but I know you won't be satisfied with that. And that's ok.

Negative evidence carries considerably more weight, in terms of disproving a god. In the case of the detective, he would expect to find gun wounds if his victim has been shot. Just so we should expect to find traces or evidence of gods (I'm speaking in terms of active gods such as the Judeo-Muslim-Christian god, or Hindu gods) or at least their works, had our earth been formed by them. Engineering the world would leave very distinctive signs. Instead, however, we find none. Instead of finding a world that accurately fits the description of any god myth, we find the opposite. To quickly address Yahweh's creation myth, which is of great popularity in my country, we would expect to find a earth that was created over the course of a roughly a week, roughly six thousand year ago or so. A world such as that would have no fossils buried more than a few (10's) feet deep, and would barely have any fossils at all.

This is my best attempt to lay out an argument. I hope my explanations are clear to you. I'll keep an eye on this post if you have any further questions or need something clarified more.

The short answer to your question is "It depends."

What exactly do you mean by "god?" There are some definitions which are specific enough to contradict known facts, and others which are self-contradictory. These gods can be proven not to exist. Other gods, or things which people have declared to be gods and believed in as such, certainly do or did exist (e.g., Caligula). Some definitions cannot possibly be proven to be true or false, e.g. a "god" which does not interact with our universe in any way.

An atheist is someone who is unconvinced by the claim that a god exists. This is not the same thing as asserting that NO god exists. You're asking atheists to prove an assertion that they wouldn't necessarily make. Most atheists are agnostic atheists.

The null hypothesis is to assume that something does not exist until there is sufficient evidence to demonstrate that it does. This is not a cop-out. I could conceive of a million different imaginary things which are no more or less plausible than a god; would I have to prove that each one doesn't exist before I could reasonably say that I don't believe in it? Why should I treat the idea of a god any differently?

“Then again I'm probably overly skeptical about everything.”

Impossible. :)

I cannot fully reject the concept of a god(s), conscious, unconscious or otherwise, because doing so isn't logical (Remember the oxymoron bit?) but it is utterly irrelevant, and so I get off the thought train there. But since you asked, the evidence is strong enough in my mind to reject every religion I have ever heard of. Being non-religious makes me an atheist by definition, although I scarcely call myself that because I think it's a silly word we don't need. You may have heard the argument that just because you don't believe faeries exist doesn't mean to need to identify yourself as an a-faerie-ist. Even yourself, being on the fence are an atheist because you have not decided to be a theist.

You're absolutely spot on about good and evil being completely human concepts, or at least, as we define them, dependent on human perspective. Good and evil could be entirely different to a different life form in our universe. On this subject, I would love to direct you towards an essay that really changed the way I think about morality. It's heavy in the content department but should probably take an hour or two to read.

http://www.ebonmusings.org/atheism/carrot&stick.html

Until you reply, cheers!

P.S. Lawrence Krauss, the poet-physicist, wrote a book titled “A Universe from Nothing: Why there is Something Rather than Nothing” in which he address nothingness's properties. Could be a good read, if that's the sort of thing you're into.