Okay, Keith B. Wiley's new paper does have a somewhat daunting title: The Fermi Paradox, Self-Replicating Probes, and the Interstellar Transportation Bandwidth. But it's a pretty easy read and hugely well worth it--because in this paper Wiley provides what may be the clearest discussion yet of the core puzzle Fermi first proposed sixty-two years ago: if alien technological civilization is even possible, then they should be here; at the very least, such civilizations should be visible to us. That we are instead faced with 'the great silence' is one of the most troubling and, yes, paradoxical, results of modern science.

I addressed the Paradox in my novel Permanence, coming up with a possible new solution for it; although Milan Cirkovic and other astrophysicists haven't disproved my central contention, they've since shown that it's not a show-stopper. As Wiley points out in this paper, even if the lifetime of an interstellar civilization is short; even if they're all doomed; there is no credible argument as to why they couldn't create self-reproducing probes (SRPs) to investigate the entire galaxy that, collectively, outlive the originating civilization. This is the very scenario I paint in Permanence. SRPs are a cheaper solution than one-off expeditions. In fact, SRPs are so efficient a solution to exploration and colonization that, plugging in some highly conservative numbers of how many civilizations there might be out there, Wiley shows that hundreds to billions of such probes should actually be here, in our solar system, right now!

Wiley blows up some of the keystone explanations for the Paradox, including Geoff Landis's percolation model, which previously I'd considered a pretty solid argument. Wiley is so good at demolishing easy explanations, in fact, that he brings us almost all the way back to square one, where Fermi had us in 1950. Where are they? We haven't a clue.

The mystery deepens almost by the day, because we've now identified 700 extrasolar planets and the count is increasing rapidly. We should shortly be racking up lists of Earthlike worlds, and we're closing in on good estimates of how many there must be in our galaxy. And the number is in the billions. So one central argument against the existence of alien life--the 'rare Earth' argument that environments to host it must be rare--has been more or less disproven. And that, just this year.

As possible explanations dwindle, we are being drawn inexorably toward the one explanation that is no explanation: that we really are alone. Why should this be? As Wiley shows, all it would take would be one alien species with our capabilities appearing, sometime in the past couple of billion years, and for that species to surpass where we are now technologically by, oh, say, a couple of hundred years... and the evidence for their existence should be present right here in our own solar system. It's an astonishing conclusion.

So are we alone? Well, there is one other possibility, at this point. I've lately been trumpeting my revision of Clarke's Law (which originally said 'any sufficiently advanced technology is indistinguishable from magic'). My revision says that any sufficiently advanced technology is indistinguishable from Nature. (Astute readers will recognize this as a refinement and further advancement of my argument in Permanence.) Basically, either advanced alien civilizations don't exist, or we can't see them because they are indistinguishable from natural systems. I vote for the latter.

This vote has consequences. If the Fermi Paradox is a profound question, then this answer is equally profound. It amounts to saying that the universe provides us with a picture of the ultimate end-point of technological development. In the Great Silence, we see the future of technology, and it lies in achieving greater and greater efficiencies, until our machines approach the thermodynamic equilibria of their environment, and our economics is replaced by an ecology where nothing is wasted. After all, SETI is essentially a search for technological waste products: waste heat, waste light, waste electromagnetic signals. We merely have to posit that successful civilizations don't produce such waste, and the failure of SETI is explained. 

And as to why we haven't found any alien artifacts in our solar system, well, maybe we don't know what to look for.  Wiley cites Freitas as having come up with this basic idea; I'm prepared to take it much further, however.

Elsewhere I've talked about this particular long-term scenario for the future, an idea I call The Rewilding. Now normally one can't look into the future; in the case of the long-term evolution of technological civilization, however, that is precisely what astronomy allows us to do. And here's the thing: the Rewilding model predicts a universe that looks like ours--one that appears empty.  The datum that we tend to refer to as 'the Great Silence' also provides the falsification of certain other models of technological development. For instance, products of traditionally 'advanced' technological civilizations, such as Dyson spheres, should be visible to us from Earth. No comprehensive search has been done, to my knowledge, but no candidate objects have been stumbled upon in the course of normal astronomy. The Matrioshka brains, the vast computronium complexes that harvest all the resources of a stellar system... we're just not seeing them. The evidence for that model of the future is lacking. If we learn how life came to exist on Earth, and if it turns out to be a common or likely development, then the evidence for a future in which artificial and natural systems are indistinguishable is provided by the Great Silence itself.

Check out Wiley's paper. And just think: the Great Silence may turn out to be no paradox at all, but positive data about what our own future will look like.