The Fermi Paradox is the question that, if the conditions for life in the galaxy are as ubiquitous as they appear to be, so that there should be hundreds, if not thousands of alien civilizations out there, then where is everyone? Why have we found no evidence for any for those civilizations? And why aren’t they here?
Edward Snowden has a proposed answer:
“When you look at encrypted communications, if they are properly encrypted, there is no real way to tell that they are encrypted. You can’t distinguish a properly encrypted communication, at least in the theoretical sense, from random noise,” says Snowden. He suggests that over time all societies realize that encryption is a necessity. “So if you have an alien civilization trying to listen for other civilizations, or our civilization trying to listen for aliens, there’s only one small period in the development of their society where all of their communications will be sent via the most primitive and most unprotected means.”
This is an interesting idea, although it’s a variation of another one that’s been around for a while. Many have speculated that a society that simply digitally encodes all of their signals might make them indistinguishable from natural noise. Digitally encoding a signal requires protocols, which we, of course, wouldn’t be privy to. Encryption would just make it even more unlikely that we’d detect it.
But this answer makes a large assumption, that interstellar exploration of any type is impossible, or so monstrously costly that no one ever bothers. On the face of it, the idea of Star Trek like exploration might well be impossible. But when you consider ideas like AI probes exploring the galaxy at 1% the speed of light, the notion of exploration being impossible starts to look overly pessimistic. If those probes were self-replicating, they’d be able to fill the galaxy in 20-30 million years, a long time by human standards, but peanuts on geological or cosmological time scales.
Of course, another possibility is that such exploration is possible, and that the probes or similar technology are here, but keeping hidden. We can’t eliminate this possibility, except that the idea that an alien intelligence wouldn’t be interested in researching our biosphere seems far fetched, or that if they’re doing so, that we wouldn’t find any indications of it.
Another possibility is that they are here and not being hidden at all, but that we’re simply too primitive to even distinguish them from the natural environment, similar to how a monkey probably regards a building as just another rock, or a vehicle as just another animal. Again, it doesn’t seem like we can eliminate this possibility, but I can’t see that it’s especially productive to dwell on it.
This always brings me back to the simplest explanation, that intelligent life is profoundly rare, and that the closest civilization may be millions, or maybe even billions of light years away.