> 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.
>Like I said... last generation's science fiction. You're being silly.
>Yes, I said silly.
Like I said, I envy your certainty...
>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.
No problem with this.
>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*.
This is where I take issue. I think it's likely there are a _lot_ of technological civilizations out there, and I think it's unwise (to be mild) to assume that _every single one_ is going to employ a variation of the nanotech scenario that obviously sits well with members of this mailing list. Some of them? Quite probably. But _all_ of them? I can't make this leap without knowing more about the civilization/s under question...and at this point, unfortunately, we don't know anything at all. We ourselves are a rather long way from the sort of nanotech you're describing, so we can't really even use _ourselves_ as an example.
>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.
Too much supposition. The star-faring culture could have easily "blasted off" from a point of technological development _much_ more primitive than the situation you describe. Generation arcs and the like may be too "science fiction" for you, but just because they're not stylish anymore among the likes of certain Extropians doesn't render the concept obsolete (or even suspect).
>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.
Couldn't resist, could you?