Ugo at Cassandra's Legacy has a post theorising about a possible link between peak fossil fuels and the Fermi paradox - The Hubbert hurdle: revisiting the Fermi Paradox.
When I started reading astronomy books, in the 1960s, nobody knew if there existed planets around other stars and the common view was that they were very rare. Of course, that contrasted with the main theme of the science fiction of the time, of which I was also an avid reader. The idea that planetary systems were common in the galaxy was much more fascinating than the "official" one but, at that time, it seemed to be pure fantasy. But it turns out that science fiction was absolutely right, at least on this point. We are discovering hundreds of planets orbiting around stars and the latest news are that one sun-class star out of three may have an earth-like planet in the habitable zone. Fantastic!
The measurements that are telling us of extra-solar planets cannot tell us anything about extra-solar civilizations, another typical theme of science fiction. But, if earth-like planets are common in the galaxy, then organic, carbon based life should common as well. And if life is common, intelligent life cannot be that rare. And if intelligent life is not rare, then there must exist alien civilizations out there. With 100 billion stars in our galaxy, we may think that also on this point science fiction might have been right. Could the galaxy be populated with alien civilizations?
Here, however, we have a well known problem called the "Fermi Paradox". If all those civilizations exist, then could they develop interstellar travel? And, in this case, if there are so many of them, why aren't they here? Of course, for all we known the speed of light remains an impassable barrier. But, even at speeds slower than light, nothing physical prevents a spaceship from crossing the galaxy from end to end in a million year or even less. Since our galaxy is more than 10 billion years old, intelligent aliens would have had plenty of time to explore and colonize every star in the galaxy, jumping from one to another. But we don't see aliens around and that's the paradox. The consequence seems to be that we are alone as sentient beings in the galaxy, perhaps in the whole universe. So, we seem to be back to some old models of the solar system that told us that we are exceptional. Once, we were told that we are exceptional because planets are rare, now it may be because civilizations are rare. But why?