> Why "unmistakable"? Has it ever occured to you that relics of some
> extraterrestrial visit weren't meant to be "messages to mankind?" You've
> backed into the same anthrocentric cul-de-sac as the extraterrestrial-UFO
> gurus who ask "Why haven't they landed on the White House law?" and think
> they've said something profound.
> Imagine this: a civilzation uses Mars as a temporary shelter of sorts a long,
> long time ago, when Mars still had abundant liquid water. They go about
> their agenda, whatever it is) using complexes of self-contained ecologies and
> either leave or die off. Their buildings are rained on, buried and reburied
> in sand, oxidized, wind-eroded...until, by mistake, they're found.
Like I said... last generation's science fiction. You're being silly. Yes, I said silly. We are not talking about a bunch of squatters with tents, like our own tentative probes. We're talking about civilizations with the ability to cross stars and probably galaxies, civilizations thousands or millions of years more advanced than ours.
I'm not talking Singularity. I'm not talking Powers. I'm not even talking about races who rip apart stars for spare parts to build Dyson spheres, even though we'll be doing that ourselves in just a few millennia CRNS (Current Rate No Singularity). But I am talking about nanotechnology, at the very minimum. If you don't want to be found, then you aren't found. If you don't care who finds you, then your works are clearly and unmistakably visible from other stars, never mind from an orbiting satellite. If there were alien races running around in our system, we would *notice*.
They do not "die off". They do not land, poke around in self-contained shelters, and then leave. I'm sure it makes for very nice short stories in _Analog_, but real life just isn't like that. By the time an alien race has crossed the gap between their star and ours, they are not picnickers; and if they haven't died off already, then they won't. They're either expansionists or extremely quiet. I acknowledge the possibility that Powers commit suicide or leave, and that the "leftover" civilizations remain mortal. Even so, aliens that can cross stars are bloody powerful mortals.
That kind of technology doesn't allow for moderation. On the spectrum of Blaringly Obvious to Totally Undetectable, it is simply beyond probability that the aliens just *happen* to fall in the Detectable To Twentieth-Century Humans But They Have To Look Real Hard category. It's such a narrow range that it's far more probable that someone is looking *too* hard.
I can only compare the Mars Face hypothesis to the creationists who claim that (a) God tried real hard to disguise the fact that Earth is only 5700 years old by burying fake dinosaurs; (b) God did such a lousy job that there are obvious flaws in Darwinism.
-- firstname.lastname@example.org Eliezer S. Yudkowsky http://pobox.com/~sentience/tmol-faq/meaningoflife.html Running on BeOS Typing in Dvorak Programming with Patterns Voting for Libertarians Heading for Singularity There Is A Better Way