To me the most likely back of the napkin answer to the Fermi paradox is that aliens are elsewhere in time. The Milky Way galaxy is about 100,000 light years across but about 13.5 billion years old. So it’s like 135,000x deeper in the time direction than the distance direction.
We’re in the light cones of all the stars we can see, and as far as we know, we can’t get out of them. If a civilization ended even 100 years earlier than our equivalent “now” in their light cone, we wouldn’t have seen them. And if they became visible even 1 year later than our equivalent “now,” we would not have seen them yet.
We’re proceeding through time at 1 sec per sec and basically if we’re going to see an alien civilization at this point, I think the only way would be if one happens to achieve the necessary technology to be detected while we’re looking at it. If there were existing civilizations that were easy to see, we would have seen them already.
I think it’s far more likely we will confirm alien life first by indirect means, for example spectroscopically detecting free atmospheric oxygen on an exoplanet, or finding tiny fossils on Mars.
We’re in the light cones of all the stars we can see, and as far as we know, we can’t get out of them. If a civilization ended even 100 years earlier than our equivalent “now” in their light cone, we wouldn’t have seen them. And if they became visible even 1 year later than our equivalent “now,” we would not have seen them yet.
We’re proceeding through time at 1 sec per sec and basically if we’re going to see an alien civilization at this point, I think the only way would be if one happens to achieve the necessary technology to be detected while we’re looking at it. If there were existing civilizations that were easy to see, we would have seen them already.
I think it’s far more likely we will confirm alien life first by indirect means, for example spectroscopically detecting free atmospheric oxygen on an exoplanet, or finding tiny fossils on Mars.