The story goes that Enrico Fermi was having lunch with fellow physicists Edward Teller, Herbert York and Emil Konopinski. They were discussing recent UFO reports in the news, as well as faster-than-light travel. During this discussion, Fermi is credited with asking where everybody else is. Where are all of the other intelligent species that have to exist in the universe, and why can we not see them?
This question gets to the fundamental contradiction between the lack of evidence for extraterrestrial civilizations elsewhere in the Milky Way galaxy and various high estimates for their probability. The Drake equation is one of the best known estimating tools for the existence of civilizations around other stars. Optimistic parameters give you tremendous results, making one think that even with moderate results, there should be millions of civilizations in the Milky Way alone. Even when we tighten them down to some very low probabilities, there are still a handful of civilizations that, statistically speaking, should be out there, and old enough to have left a visible mark on the universe.
Unless we are dismissing an unnatural signal as natural, we do not. So the question is, why?
There are plenty of thoughts on the subject, but I wanted to work this into how I deal with my own universe in the Automated Empire stories. While I admit I make non-human species a bit more prevalent than I believe will actually be the case, I do believe there are other intelligent species out there.
I do think that there are certain limitations that are easily overlooked. For example, a civilization in the Andromeda Galaxy might be a two and a half million years ahead of us, and already altered their galaxy in such a way as to be easily visible. But because that galaxy is two and a half million light years away, we would not be able to see them at all. Within our own galaxy, it is the same situation, just on a slightly smaller scale. The other side of our galaxy is a hundred thousand light years away.
My opinion is that it's just a matter of time. A lot of time. No, we are not alone, but we are still early. We might be the first, but I doubt it. The thing is, the molecules in our bodies were formed in stars, and it takes time to get that mix right. So maybe we are in the first batch in our galaxy. Maybe a thousand light years away is a civilization a thousand years ahead of us technologically. We would still not be able to see them. But we will, eventually.
In the universe of the Automated Empire, there are civilizations much older than we are, and some have died out. But there are a lot more who are close to our age, and then there will be many who are younger. I think that gives me a rich tapestry to explore. In the end, having such a fictional universe is a lot more fun in terms of storytelling for me personally.