Why theano UFOs

> Weapons that might devastate every single object in an entire solar
> system?

They don't have to devastate every object. They just have to make
the civilization collapse. There are endless possibilities. Maybe
some species have a vulnerability such that there's a weapon that
just makes everyone of that species really stupid, system-wide at the
push of a button. Maybe for some species at some points in their
technological development the basic weapon is just a plain old rock
going the opposite direction in the same orbit, but an elaborate
series of countermeasures and counter-countermeasures and so on make
it optimal to put all your eggs in one basket that's 99.99% safe in
any given year -- and species that follow that trajectory tend to be
stable for 10,000 years. Maybe some civilizations develop really
efficient missiles that can track down any habitat big enough for a
viable population, and set them off in varying numbers in different
conflicts until one time in 100,000 there's a conflict big enough to
have no one left. Maybe some species at some times like living in
really big structures, expansions of the generation ship that arrived
there, with everyone living together and robots gathering resources
everywhere else in the system, and there's a nuclear option that
destroys the whole structure. You can keep on spinning these
scenarios for a long time, and truth is almost certain to include
many possibilities that are stranger than fiction.

With millions of possible doomsday scenarios, and millions of years
for them to happen in, the odds of one of them happening approach one
even if each scenario is very unlikely in any one year.

that eventually rupture due to unobtainium fatigue with a half-life
of 500,000 years.

> You have to explain why ALL species would INEVITABLY head off down
> this same

Not the same one. That's the whole point. With millions of possible
doomsday scenarios, and millions of years for them to happen in, the
odds of one of them happening approach one even if each scenario is
very unlikely in any one year.

> Yes, that supposition is exactly where we differ. It seems you
> assume that societal collapse is inevitable and the only variable
> we might discuss is the timing.

I *assume* that societal collase is possible, not that it's
inevitable. Or more precisely, that its probability per year is non-
zero, and that the probabilities for years far apart are nearly
indpendent. Then I *conclude* that given infinite time its
probability approaches one -- still not inevitable in any finite
period. Finally I *propose* that the Great Filter may simply be that
millions of years is enough time for the actual probabilities to be
pretty big for whoever has been out there.

> Resources can be recycled such that I don't think mass extinction
> could possibly be the end result.

Recycling one resource consumes others, inevitably including energy.
If their energy source is total conversion, exponential growth will
soon demand enough energy to convert the entire mass within the light
cone to blackbody radiation. Zero local population growth would be a
solution, except that as soon as someone cheats they win in the
medium term.

> I certainly don't assume that. I merely assume that a race which
> pops up later will, by definition, be younger. And I have a hard
> time seeing a younger race wiping out an older one which is armed
> with a technology a million years in advance of theirs.

Not only is such leapfrogging possible, it's the norm on the shorter
timescales that we can actually observe. If a technology is fifty
years old in the country that developed it, the country that learns
it will be making improvements in five or ten years. If a culture is
in a million-year stasis wrt a particular technology, by definition
it's not particularly innovative wrt it. A thousand years is plenty
of time for a species to adopt and adapt the technology they learned
from another.

--- In spacesettlers@yahoogroups.com, "Combs, Mike"
>
> From: Dan Wylie-Sears
>
> > How about whatever weapons they invent, as far beyond our schemes
as
> > nuclear-armed ICBMs are beyond the schemes of Julius Caesar?
>
> Weapons that might devastate every single object in an entire solar
> system? Maybe. But I think any technological advances that would
> enable the creation of such weapons would also make it easier to
> establish far-flung colonies.
>
> > 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?
>
> Yes, but see what kind of elaborate scenario you had to devise? You
> have to explain why ALL species would INEVITABLY head off down this
same
> road (or a similar road with the same end result) WITHOUT EXCEPTION.
>
> > 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.
>
> So you're saying that an exponentially-reproducing mass of human
flesh
> expanding outward at the speed of light might then turn around and
> become utterly extinct? I have a hard time seeing it. Resources
can be
> recycled such that I don't think mass extinction could possibly be
the
> end result.
>
> > Why would there be such diversification as to make it a matter of
> > never in forever? Why would there be any at all?
>
> Can't quite parse this. Could you expand on this point a bit?
>
> > 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),
>
> Yes, that supposition is exactly where we differ. It seems you
assume
> that societal collapse is inevitable and the only variable we might
> discuss is the timing. You probably feel justified in assuming
that all
> societies are mortal given history here on Earth. But I think a
> breakout into space might result in something new: an immortal
society.
>
> (I don't mean immortal in the sense of unchanging, only in the
sense of
> never reaching a point where they fail to leave any descendants.)
>
> > 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?
>
> I certainly don't assume that. I merely assume that a race which
pops
> up later will, by definition, be younger. And I have a hard time
seeing
> a younger race wiping out an older one which is armed with a
technology
> a million years in advance of theirs.
>
> > 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.
>
> Perhaps true. I still feel justified in holding to 2 conclusions.
One:
> I still believe that a society capable of interstellar colonization
> becomes unkillable. Two: It's difficult to come up with a no-growth
> scenario so all-encompassing that nobody would ever avail
themselves of