I voted for "don't know" because I know some interpretations of quantum mechanics would say they exist conceptually. I probably go about my daily life, including thinking about ATLs, with the premise that we are only engaged in science fiction and speculation.
Xen said:
"I think they do, when ever I write something, anything, I see it as though Im giving life to a world, or a galaxy. The people become real, the emotions become real. I guess its kind of like the Never Ending story, as long as you create it, its real. So yes, I say theyre real, out there somewhere."
-this kind of scares me. I too feel these worlds take on a certain reality of their own when I "create" them. But does this mean that when I create a fictional ATL with the Third Reich victorious or slavery continuing in the USA/CSA to the modern day, I have somehow called into being real people to be gassed and enslaved? I hope to God the answer is no, or I'll only be dreaming up nothing but boring goody-two-shoes histories where everybody loves and respects each other!