The Fermi paradox is indeed a thought-provoking concept, and there are various perspectives on it. The paradox raises the question of why, given the vast number of potentially habitable planets in the universe, we have not yet observed any conclusive evidence of advanced extraterrestrial civilizations.
Regarding the capability of interstellar travel, it is important to distinguish between our current technological limitations and what a highly advanced civilization might achieve. It is true that with our current technology, interstellar travel is incredibly challenging, and we have not yet sent manned missions beyond our Moon. However, technological progress is not stagnant, and advancements could occur over vast timescales.
When considering the potential capabilities of extraterrestrial civilizations, it is plausible to imagine that a civilization significantly more advanced than ours might have developed scientific and technological breakthroughs that could overcome the challenges of interstellar travel. This could involve concepts and technologies beyond our current understanding.
The expansion of space, as described by the theory of cosmic inflation, does indeed cause distant galaxies to move away from us at accelerating speeds. However, within a local galactic group or a region of space, such as a galaxy cluster, gravitational interactions can overcome the effects of cosmic expansion. So, while the universe as a whole is expanding, certain structures remain gravitationally bound and could be navigable over vast timescales.
It is also worth noting that interstellar travel does not necessarily require physical spacecraft to traverse large distances. Concepts like self-replicating probes, which could explore the universe at a slower pace but still cover significant distances over time, have been proposed. Additionally, there could be advanced methods of communication or exploration that we have not yet envisioned.
Ultimately, the Fermi paradox presents us with an intriguing question and various possible explanations. It highlights the vastness of the universe and our current limited understanding of it. Future scientific discoveries and advancements in technology may shed more light on this paradox and provide us with a clearer understanding of the prevalence or absence of extraterrestrial civilizations.