[WRhine]

I have read similar articles on Fermi's insights on this before. It does have the clarity of logic behind it. One thing that he does not consider though is the possibility that highly advanced civilizations with technology that we cannot possibly comprehend may not be the type of civilizations to mindlessly expand to other solar systems just for the sake of expansion. In other words, they are beyond that type of physical conquest. Also, a highly advanced civilization might act as a protector for emerging civilizations, such as ours, from the more hostile galactic regimes. It is noteworthy that we here in America have long ago gave up our conquering ways (not to be confused with wars to protect our interests) and replaced it with friendly collaboration and alliances.

[tortoise]

One thing that he does not consider though is the possibility that highly advanced civilizations with technology that we cannot possibly comprehend may not be the type of civilizations to mindlessly expand to other solar systems just for the sake of expansion.

People after Fermi have spent a great deal of time on this very issue. For a number of reasons that I won't go into here, it turns out that one can demonstrate that grabbing resources as fast as you can is critical to survival in the long run and that any highly developed and rational society would HAVE to expand outward at a very fast pace. The calculus of it all points to advanced civilizations dismantling natural resources at a dizzying pace. The rational solution when the number of civilizations is one is very different from the rational solution when there are many civilizations.

[PatrickHenry]

Also, a highly advanced civilization might act as a protector for emerging civilizations, such as ours, from the more hostile galactic regimes.

This kind of explanation for the Fermi Paradox has been considered. It may be that some aliens are guided by the Prime Directive, and they won't interfere with us. But in a galaxy of thousands -- or perhaps millions -- of intelligent species, all it takes is one rogue culture to breach the protocol and go out conquering. One species can occupy the galaxy in a relatively short time, even if each "hop" from one star to the next takes centuries. Once a species' expansion begins, it's surprisingly rapid. The occupied sphere of colonized space grows very rapidly (again, relatively speaking). There's been time for the galaxy to have been colonized many times, by a whole succession of species. So the Fermi Paradox is still very valid.