It's certainly possible that civilizations which advance beyond our stage of development use some additional force of Nature that we have not yet discovered as their primary means of communication, and that therefore we aren't detecting their signals. But that still doesn't explain why we can't detect anything that they're doing at all, since some of the actions of an advanced civilization -- flying large starships, modifying the output of their stars, etc. -- would be incredibly obvious even at interstellar distances. It also doesn't explain why we can't detect any radio emissions from civilizations at around <i>our</i> level of development (we've had radio about a century now with little sign of abandoning it, surely at least <i>some</i> other civilizations must keep it about as long). And most of all, it doesn't answer the <i>main</i> Fermi Paradox: "Where are they?" Because advanced civilizations would be able to construct starships, and colonize the whole of our Galaxy.

And yes. They could even bring the soil along with them -- if, at their level of technology, they still needed soil. Hey, <i>I'd</i> bring some -- I <i>like</i> looking at green growing things.

Please see:

freefall.purrsia.com/ff1400/fc01349.htm