Okay so first off, I would like to clear up what you think about the scientific theory: the scientific theory is different from just a theory. A scientific theory is "a well-substantiated explanation of some aspect of the natural world, based on a body of knowledge that has been repeatedly confirmed through observation and experimentation". There's no guessing game-it's a repeatedly tested conclusion. So please don't say that. And secondly, no, atheism is not in any way a religious belief. Atheism is simply the opposite of that-lack of a religious belief in a god(s).