When discussing SETI and the Fermi Paradox the focus tends to be on distance, the idea that an alien civilization could exist in relatively close proximity to earth enough that we could detect them. So far we haven’t found anything. But there is another aspect to the potential existence of
The first possibility is that there was once someone else here, but are no longer, either through self-destruction, destruction at the hands of another exo-civilization or cataclysmic event, or even unforeseen ways a highly technological civilization could simply up and disappear. A civilization like this is possible because the Milky Way has been able to form planets far longer than our solar system has existed, the current oldest exoplanet we know of comes in at about 12.7 billion years.
Whether exoplanets that formed early in the Milky Way’s history could have the right composition to be earth-like and produce a civilization is up for debate. But it’s at least hypothetically possible, and such a civilization, even though extinct, may have left artifacts or at least evidence of their former existence that we might detect as we explore the galaxy.
But, it’s also possible that we are early in the curve in that Humanity might be among the earliest civilizations present in the Milky Way. There are a number of reasons this could be, dealing largely in unanswered scientific questions. Is life easy to start chemically? We don’t know yet. Does life develop complexity very slowly? Earth suggests it does, but again, we don’t know. What conditions have to be present for intelligent life to arise? Are those common or rare? There are arguments that they are probably rare.
As a result, we may be early in the game and that the solution the Fermi Paradox and the lack of detections so far of alien civilization is that we’re among the earliest to arise. But this brings up another possibility, if time is key, then will civilizations become more prevalent in the Milky Way as time goes on? The universe is still fairly young, it could last for immense amounts of time. And while its period of star and planet formation will eventually come to an end, it’s chocked full of some very long lived types of stars that will be here billions of years after our own sun goes red giant, with more stars yet to form. These long-lived stars, the red and orange dwarfs, could allow for environments that can allow life to evolve for much longer periods of time than we had here on earth. If so, as the universe ages this might allow for an explosion, or blossoming of intelligent life billions of years from now as life has longer to evolve and develop intelligence. But that’s not the only way it could happen. If we colonize the galaxy, or any contemporary civilization to us, then we could just as easily create aliens of our own.
One way this can happen is uplifting, where we, or someone else, could upgrade a natural species, either from earth or one we might find in space to be smarter, or if not that, more biologically suited to leave their home planet. An example here would be a water world, where aquatic life might be intelligent, but might be trapped by their conditions and physiology and rendered incapable of harnessing fire, or for that matter building rockets. This could also be relevant here on earth. If we survive for hundreds of thousands, or millions of years longer, evolution on this world could move towards other intelligent species arising here. A good example would be the dolphins, there is some thinking that they aren’t that far behind us as far as evolving intelligence goes and that earth in the distant future might be home to two intelligent civilizations, though one might not be capable of developing technology. Would we help them out? Or would someone come by and help us out. It’s always possible, and we’re already asking this question of ourselves, that biology is inferior to technology and that we might some day transcend biology to become a machine civilization. I’m not sure we’d ever really do that or not, but what if it were forced onto us, similar to perhaps the Borg or The Reapers from Mass effect? What if we weren’t first, and out there somewhere lurks a far older civilization, perhaps one made up of machines?