Comment by antonvs

> It’s a logical extrapolation if you think life is a natural phenomenon.

No, it really isn't. Taking life on Earth as an example, almost all of our technological signatures are effectively undetectable as little as 5 light years away. See e.g. the paper "Earth Detecting Earth" (https://arxiv.org/pdf/2502.02614). The maximum detectable distance for unintentional signal leakage is 4 light years - about the distance to Proxima Centauri, the nearest star. So if we're looking for that kind of signal, we have a population of exactly one star system that we might be able to detect something from, at the maximum end of the detectable range.

The paper also lists a couple of exceptions, which are the highly directional Deep Space Network and planetary radar, theoretically detectable at 65 ly and 12,000 ly respectively. But these only cover small parts of the sky for short periods, making interception of such signals extremely unlikely. Also, signals like that have only been transmitted for decades at most, so there are at most a few thousand star systems that could conceivably have intercepted one of these signals.

All in all, while the probabilities involved can't be calculated with certainty, they do certainly lean towards it being very unlikely for us to have detected another technological civilization. Which is consistent with what we actually observe.

Detecting non-technological signs, like atmospheric gases, is more feasible but also not necessarily definitive. E.g., the recent evidence for dimethyl sulfide in the atmosphere of K2-18b is considered a tentative candidate for a biosignature, but is in no way definitive.

In short, the Fermi "Paradox" mainly confirms what we now know about the difficulty of detecting life beyond our solar system.

As for spaceflight vs. sailing, at some point extrapolation from analogies just breaks down, and interstellar travel is certainly one of those cases. The energy demands, distances, timescales, technological limitations, radiation issues, economic and political issues, etc. all combine to make it an effectively impossible project.