Why theano UFOs

--- In spacesettlers@yahoogroups.com, "Combs, Mike"
> From: Dan Wylie-Sears
> > A spacefaring civilization has no particular claim on
> > lasting a million years, let alone a hundred million.
>
> I'd have to disagree. I think one of the things which inevitably
> falls out of the assumption of a spacefaring civilization is that
> it has become an immortal civilization. As soon as we get to the
> High Frontier stage, no conceivable disaster short of a supernova
> could wipe out the human race. As soon as we establish orbital
> habitats around another star, not even a supernova could do it.
>

How about whatever weapons they invent, as far beyond our schemes as
nuclear-armed ICBMs are beyond the schemes of Julius Caesar?

How about division of the species into breeders and
protectors/engineers, followed by re-merger into a unified species
incapable of replacing the grand infrastructure their great-to-the-
fifth grandparents built to last for seven generations?

How about depletion of whatever resources it depends on? Let's
assume they overcome the need for any resource but space, actual
cubic meters of somewhere to be, and are limited to travel at the
speed of light. With exponential growth at typical rates for
existing human populations, fixed body size, and a density of 1 g/cc,
the total mass of all members of the species will soon exceed the
volume of a sphere expanding at the speed of light. Malthus picked
linear growth of carrying capacity out of his @#$^, for exponential
growth to exceed. But Einstein gave us a possibly real constraint
that grows at cubic rate, which exponential growth overwhelms almost
as quickly.

> I think with spacefaring comes incredible diversification, and with
> that the odds become staggeringly small that all evolutionary lines
> would come to the same end.

Why would there be such diversification as to make it a matter of
never in forever? Why would there be any at all?

> I don't quite get why you assume this. I would expect that the
> species which don't maintain mixing across their range would be the
> ones with far-flung colonies.
>

Far-flung relative to their travel capabilities, yes. Suppose each
colony can run itself to collapse with a half-life of 10,000 years
(not that a lot of human civilizations have lasted that long), and
they have room for a thousand in the area they reach. In just
100,000 years the half-life gets them down to less than one. A more
realistic model would be a wavefront expanding through a galaxy or
cluster of galaxies, with the number of occupied star systems doing a
random walk as the region of colonization expands and the colonies
die out.

> > Or maybe different species evolve, make contact, and annihilate
each
> > other after periods of peaceful coexistence averaging only 10,000
> years.
>
> I think the only way to assume that they annihilate each other is to
> assume they are at roughly comparable stages of technological
> advancement. The odds are vastly against this. It's far more
> likely that one of the civilizations would be in excess of a
> million years more advanced than the other. That would not be a
> mutually-annihilating war, that would be an extermination.

When no new species has been a serious threat for a million years,
are they going to keep on slaughtering every new one before it gets a
peek at their technology? That kind of absolute cultural rigidity
doesn't bode well for their ability to handle changing circumstances.

It's easy to keep spinning scenarios, and impossible to test most of
them. Most will seem fairly unlikely on further consideration, but
only most and fairly, and in the end you haven't gotten much of
anywhere.