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Re: starship-design: WHERE ARE THEY?

In a message dated 7/25/99 11:07:17 AM, lparker@cacaphony.net writes:


I've always been interested in this too.  Its been a major question about the 
nature of life and the universe.

>The first new theory is from James Annis, an astrophysicist at Fermilab
>Chicago. He thinks cataclysmic gamma-ray bursts often sterilize galaxies,
>  That, says Annis, may be the answer to Fermi's
>question. "They just haven't had enough time to get here yet," he says.
>GRB model essentially resets the available time for the rise of intelligent
>life to zero each time a burst occurs."
>Paul Davies, a visiting physicist at Imperial College, London, says the
>basic idea for resolving the paradox makes sense. "Any Galaxy-wide
>sterilizing event would do," he says. However, he adds that GRBs may be
>brief: "If the drama is all over in seconds, you only zap half a planet.
>planet's mass shields the shadowed side." Annis counters that GRBs are
>likely to have many indirect effects, such as wrecking ozone layers that
>protect planets from deadly levels of ultraviolet radiation.

The importance or our ozone layer is grossly over stated now a adays..  If 
our ozone layer were eliminated, it would be as if we all moved 100 miles 
closer to the equator.  Also radiation forms ozone.

On the other hand having half an ecosphere burned off would have to trash the 
rest of the planet.  Certainly enough to crash a civilization for a while, 
but not enough to kill off intelligent lifeforms.

A variation of this is the idea even milder burst could crash an interstellar 
civilization.  Right now cosmic rays are a major limitation on life in space 
due to the radiation.  But since we know about it we can design our ships and 
platforms to deal with it.  But it seems cosmic rays are intermittent.  If we 
"came out" during a millennia of low space rad.  We might have a major 
interstellar civilization, and see it all destroyed when a few century cosmic 
ray storm whipes out space travelers.  The result could crash civilization 
everywhere.  Perhaps were just the first ones out who knew what to expect?

>Annis also highlights an intriguing implication of the theory: the current
>rate of GRBs allows intelligent life to evolve for a few hundred million
>years before being zapped, possibly giving it enough time to reach the
>space faring stage. "It may be that intelligent life has recently sprouted up
>at many places in the Galaxy and that at least a few groups are busily 
>in spreading."


>The second theory deals with a surprising connection between the conditions
>required for a total eclipse and for the emergence of intelligent life.
>Guillermo Gonzalez of the University of Washington in Seattle points out
>that our distance from the Sun is a necessary condition for us to be here.
>"If we were a little nearer or farther from the Sun, the Earth would be
>hot or too cold and so uninhabitable," says Gonzalez. At the same time
>existence depends on an unusually large moon since its pull stops the Earth
>wobbling around too much on its axis and causing wild and catastrophic
>swings in climate like those on Mars. Our Moon, which is unusually large
>compared to those in almost all other planet-moon systems, probably formed
>from molten material blasted from the Earth during the impact of a giant
>body more than 4 billion years ago.

This seems iffy, but the weird nature of our moon could be significant.  Thou 
I find it hard to believe its the only way to evolve a intelligent race?  One 
could just as easily decide one needed to be on a moon of a jovian since 
close in to most stars the radiation and orbital stability are to bad.

>Taken together, these two factors enormously reduce the values of at least
>one and probably as many as three variables to practically zero offering
>at least one possible answer to Fermi's query, there aren't any...
>If you consider all of the factors you can write a simple relation, using
>Drake's Equation, for estimating the probability. I use the word "estimate"
>intentionally because our knowledge of most of the factors is so poor that
>we are really only guessing.

True, we haven't more then poor clues, and most of them don't add up to the 
empty skies we see around us.  Any of these ideas at most mean their should 
be fewer folks out their coming here.  But we have no sign that anyone EVER 
came to earth!  The statistics of that are low, which is frightening.

>Suppose you guessed that stars in our galaxy form at the rate of one per
>year (probably not a bad estimate), that 1/5 of the stars have planets
>(no one knows), that there are 0.0005859375 planets with stable environments
>(length of time between GRBs divided by the age of our solar system times
>the fraction of planets with suitable moons in our solar system ), that
>life appears on each (fraction = 1), that intelligence emerges on each of 
>(fraction= 1), that 1/10 of these develop communication capability and
>that these remain in this state for 1000 years. Then, it works out that the
>number is 0.01171875. In other words, in one hundred thousand years, only
>one intelligent, communicative civilization would appear, far less than
>most current speculations.

But again the numbers are guesses.  You assume few stars grow starsystems, 
and very few have environments where life can grow.  There ae multiple 
autonomous ecosystems on earth, only ours needs to worry about solar energy 
or weather.  Those based on the volcanic chemistry of deep ocean vents, or 
deep under ground are now thought to be far larger then our photosynthesis 
based ecosphere.  The deep ocean vent environment is thought to exist on at 
least one moon in our solar system, and that's out in the jovian belt.  This 
strongly suggests our biases toward the "life belt" based on solar heating 
and photosphere may just be our prejudice. 

Why assume folks only retain communication abilities for a thousand years.  
We've retained writing for about 5 times as long.  Abilities to build boats 
and simple buildings and weapons for a couple times that.  Given the value of 
high tech and spaced based industry and resources, I could see this stuff 
being a high priority for retention.

A better question is why would one do SETI communications.  If your curious 
about the stars.  Most won't have anyone to answer your call.  Sending probes 
or expeditions could be far more effective, and get info back a lot faster 
then waiting for someone to answer your call.  I'm beginning to think the 
basic assumption of SETI, that folks would always prefer transmitting and 
waiting, rather then scouting about and looking for themselves.  Give the 
ridiculous waits necessary to check out any stars, especially if you need to 
wait for a civilization to evevolve to answer your call.

Bottom line, we don't know (even in vague ways) how likly biosphere's, 
intelligence, muchless technical civilizations are.  They could be virtually 
the norm for any chemically active planet that hangs around a few billion 
years.  One per solar system could be virtually unknown.  

Or they might almost never happen, and you hardly ever have more then a 
handful of civilization active in a galaxy at one time.

Or perhaps the nanotech/singularity folks are right and past our level of 
tech things explode dramatically.  A couple centuries from now our 
desendanscould be so advanced they'd be little more interested in contacting 
us, as we'd have to go visit ants.

>L. Parker