>But would not a good way to test and expand a culture be to show it stuff it
>could NOT deal with? Stuff that can be explained away -- like, "Hey, that's
>just aliens/Russian missle tests/dirigibles/witches/swamp gas!" -- won't
>really challenge a belief system. However, if a UFO landed in Central Park
>on a Sunday afternoon when the Great Lawn is packed and displayed all sorts
>of neat gadgetry, then a lot of skeptics, at least, would have to change
>their ideas... How come that never happens?
This "landing on the White House lawn/Central Park" argument for the nonexistence of UFOs never fails to incense me. I was going to let this thread drop, until I came to this line.
A visiting alien culture would only reveal itself in this manner if it was really interested in public disclosure. We can imagine many reasons why a civilization might want to present itself to "the natives" in just such a way. Conversely, though, we can think of many more reasons why real aliens (as opposed to Mr. Carpenter in "The Day the Earth Stood Still" or the humanoids in "Earth vs. The Flying Saucers") would choose a more subtle approach--if they even endorsed the prospect of contact at all.
There was a paper in "Science" magazine in the early 80s explaining why a visiting extraterrestrial culture would almost certainly _not_ go public by "landing in Central Park" or whatever landmark you prefer. History of contact between civilizations of different levels of technological development (i.e. the Aztecs vs. European invaders) is abysmal. The "lesser" of the two cultures is, without exception, subsumed, and its memetic value is vastly diluted if not destroyed.
I think it's reasonable to expect a visiting alien culture to feel the same way if they are indeed visiting us. I hate to resort to the lame "Star Trek" "prime directive" analogy I've come across so many times, but an advanced culture that insinuates itself upon a less advanced culture (benevolently or not) has an intellectually crippling effect on the latter.
If aliens are here, I don't think they'll be particularly interested in our money or our women (though Bruce Sterling's Investors have a ring of authenticity to them...). Rather, they'll be interested in our _uniqueness_. And this is the one thing that would be destroyed by public disclosure.
In short, "not landing in public" is not a very cogent argument against the presence of aliens in our midst.