Aliens need a lot motime to find us

On Jan 22, 2007, at 22:10 UTC, Jake wrote:

> I agree on most of your points.. Now let me pick them apart...

Sure! That's how we learn from each other.

> What I was trying to say was that just because other beings may not be
> able or advanced enough to be detected doesn't make us alone..

If by this, you mean that there may be life out there but no other
civilizations, then I would agree.

If you mean that there may be other civilizations, which remain stuck
in a pre-spacefaring stage essentially forever... well, I find that
hard to believe. Seems like a civilization is either going to advance
to the space-settling stage (as we have nearly done), or die out (as
the dinosaurs did, whether they had civilization or not). Moreover,
they're going to do one or the other pretty quickly, on a geological
timescale. Our civilization only arose a few tens of thousands of
years ago, after all. Dinosaurs ruled the Earth for millions of years,
and even that was just an eyeblink -- the vast majority of Earth's
history, there was nothing more advanced than microorganisms.

So, when we finally get out into the galaxy, I wouldn't be at all
surprised if we find other planets with microscopic life. But I'd be
quite astonished by the very improbable case of finding a planet where
civilization arose within a few tens of millenia of our own, and so
have not yet started settling the galaxy.

> I believe advanced beings have been or are "here" now.. But they would
> have faced the same problems we do and maybe some different.. Like
> interstellar travel, life support, ect..

I'm not sure what you're saying here. Are you saying that aliens have
been here on Earth? Or walk among us today? You do hear that sort of
claim from UFO and conspiracy nuts, but not generally on serious
discussion lists. It's remotely possible, of course, but flies in the
face of Occam's Razor.

> Maybe it's just not feasible
> for them to send a "welcome wagon".. Maybe the journey is done in
> generations or through cryogenic hibernation and the explorers are not
> able to return with their findings..

Hmm, I think a point has been missed. If they're out there at all,
they settled the *entire* galaxy -- except for any areas they purposely
avoided for some reason -- millions of years ago. They don't have a
long journey to go; they'd be right next door, and obviously watching
us, since they have eschewed the resources of our solar system.

> Or maybe they have (to take from star trek) a prime directive..

Yes, that's the "nature preserve" hypothesis. Not outrageous, but not
really in line with Occam either. As Mike's article points out, surely
if the whole galaxy were settled millions of years ago and were now
teeming with advanced civilized life, we'd see SOME sign of their
engineering works. Yet we see nothing we can't adequately explain with
fairly simple astrophysics. (Except the whole dark matter/dark energy
quagmire, but I think that points more to a misunderstanding of gravity
on a large scale than to any engineering effect.)

Still, it's far more likely that we're in a nature preserve than, say,
that there are dozens of civilizations out there that have not yet
started to colonize other stars.

> The chances of two or more civilizations evolving in the same galaxy
> within a few hundred million years may not be as slim as you think.

Well, I've worked through the math. It really does turn out to be
extremely unlikely. I can go into more detail if you wish, but in a
nutshell, this is because the time-to-emergence would follow a normal
distribution, and in any normally distributed population, the outliers
are rather far apart relative to the standard deviation. In my
simulations, it's occasionally possible for the second civilization to
arise before the first one has entirely settled the galaxy, but even
that is rare. All other civilizations that arise at all, find
themselves in a long-since-inhabited galaxy.

Note that this result is not sensitive to parameters such as the
likelihood of life on any particular planet, the likelihood of life
disappearing from any particular star system, etc.

> After all.. We had at least 3 separate ones arise right here on
> earth..

Hmm, no, not really. In all of Earth's 4.5-billion-year history, there
has been exactly one civilization: humanity. The various branches
you're thinking of are all part of that same Homo sapiens development.

You can sort-of make an analogy with different human cultures, and it
still works, but the scale of everything is different. And you end up
with pretty much the same result: to the extent that the cultures
really were isolated, it's extremely unlikely that when they finally do
come into contact, they'll be at the same level of technological
development. Did the Europeans find, say, the Australian Aborigines
with guns and clocks? Why not? Well, it's obvious that if they're
really independent, it's extremely unlikely that they'll develop to the
same point at the same time (within a few decades, say). Yet for some
reason, many people have trouble applying the same argument to the
galaxy as a whole. (Not talking about you, Jake, so don't get ruffled;
just making a general observation.)

> Your analogy of "life in a pond" is way off base.. I mean yeah.. If
> there was some civilization so advanced they dominated the whole
> galaxy.

But that's the whole point. The first civilization to start colonizing
the stars WILL do exactly that, and in fairly short order. How could
they not? Expanding into new niches is a property of life, ANY life,
even mathematical simulations of life. As long as you have
reproduction and variation, it will will happen.

> Then maybe you would be right, but this is obviously not the
> case or we would probably be living under their control now..

Right! Exactly. So, most likely, they're not out there at all, and we
happen to be the first or only civilization our galaxy will produce.
(Or else, we really are living under their control now, and don't
realize it -- c.f. "nature preserve.")

Best,
- Joe

Joe Strout -- joe@...