"Matt Giwer" wrote in message
m...
Joann Evans wrote:
[snippage]

Where are they? is as good a question as Why would they
care to show up?

When one considers the possibility of even a single
long-lived (many billions of years) civilization in the
galaxy, counting daughter colonies, generation ships,
outposts, and orbital and other way-stations, i.e.,
so-called Ancients or First Ones, the two questions devolve
into the same one--Fermi demands that they already be here
(in local interstellar space,) or at least close enough for
their activities to be easily detectable. So, perhaps it is
useful to at least list some of the more detailed reasons,
besides the simple distance one, the Ancients would/or could
not be here. Since YMMV, I will just start off with a few of
my most favored ones and ignore the multitude of others
possible; in particular, for now I'll not consider there are
_no_ Ancients, or the concept that, "we cannot even imagine
the motives and actions of such hyperadvanced
intelligences." [Hypotheses may not be independent and P
values below have not been normed to 100%.]

1. All civilizations find the costs and resources needed for
maintaining IS outposts etc etc and a cohesive identity for
any prolonged period are prohibitive for numerous possible
reasons.
My estimate of probability-low say, 20% Superadvanced civs
will solve such problems, particularly if enough time is
allowed.

2. Ancients, for several possible reasons, maintain silence,
practice the Prime Directive and stealth, and actively avoid
contact with "Primitives." This covers lots so P is high,
estd. 80%

3. Ancients completely withdraw from the field eventually.
Many reasons possible: they become pseudoimmortal and thus
fear risk of death by accidents, aliens, etc; They become
"Lotus Eaters" due to drugs or Virtual Reality pursuits
(cyberjacking practices of some sort.) Or, they simply
withdraw after so many years of acquiring and cataloging
info on all types of Primitives and their actions, and
enormous scientific data on the universe-IOW, "been there,
done that!" Very broad category - High P ~ 90%

4. Singularities or Transcendence other than (3.) Medium P
~ 20%

5. Unavoidable presently unknown or underestimated natural
physical "nemesis" factors inherent in IS travel. Low P ~
15%

OK that's enough for a start--each of these could be further
broken down to myriad factors if desired. As shown though,
(3) and (2) are my best bets.
....tonyC