All --
A couple of issues / observations . . .
Concerning the probability that an "advanced civilization" (or "intelligent
species"), even if it ever comes into being, will persist long enough to be
noticed by another hypothetical "intelligent species" -- there are arguments
that it (the probability of persistence) will be quite low. Here's a link to
some discussion of Bayesian reasoning, and a brief outline of what is sometimes
called the "doomsday argument":
http://csustan.csustan.edu/~tom/Lecture-Notes/Risks/risks.pdf
But of course a deep question in SETI is the question of what one should look
for . . . clearly the best bet is electromagnetic signals -- although even that
may just be more or less parochial bias. Perhaps we should be looking for
gravitational wave communication, or neutrino-based communication, or something
we haven't thought of or have no clue about -- but we're constrained to looking
with the technological devices we have today, so radio waves it is, right?
Although even that raises some problems. We've been a "technologically
advanced civilization" (i.e., capable of using electromagnetic spectrum beyond
simplistic visual signaling) for what, a century? And note that looking for
simple AM or FM signals is almost surely pointless -- we're already outgrowing
that -- in terms of sheer volume, it's "all digital now." And, information
theory tells us that optimal use of a digital communication channel will
maximize entropy, and hence will make all channel usage look like white noise.
So, if we want to look for "advanced civilizations," what we should be looking
for is "white noise" sources. But beyond that, optimal use of available
channel capacity will demand "narrow-casting" to avoid interference (and thus,
e.g., fiber optic, etc.). You don't want to use "broadcast" because of the
waste associated with leakage and interference.
Hence, if we want to look for "advanced civilizations," it seems we should be
looking for relatively quiet "white noise" sources . . . :-) Sort of the
only other hope is that some other "advanced civilization" will notice the
"noisy new kids on the block" (us :-), and send us a really simple, easy to see
"narrow-cast" beamed directly at us. I'd say we're extremely unlikely to
"overhear" the "noisy chatter" of advanced civilizations . . . my guess is that
advanced civilizations will outgrow the "noisy chatter" modes of communication
about as fast as we have been . . .
Thanks . . .
tom
p.s. -- An example of evolution of communication . . . consider Sprint . . .
how did Sprint telecomm come into existence? Southern Pacific Railway (SPRint
-- a coincidence? Not really :-) had railway right-of-ways, which gave them the
ability to lay fiber-optic backbone, which enabled them to enter the Switched
PRIvate Network Telecommunications game, etc. . . .
On Mar 31, 2012, at 12:02 PM, Douglas Roberts wrote:
> A couple of comments:
>
> 1. Recent research shows that there are tens of billions of rocky planets
> inhabiting the habitable liquid water zone in our galaxy alone. See
>
> http://www.physorg.com/news/2012-03-billions-rocky-planets-habitable-zones.html
>
> 2. Multicellular life started on earth about 540 million years ago
>
> 3. 250 million years ago the Mesozoic era began -- trees, dinosaurs
>
> 4. Homo Sap. has been around for maybe 100,000 years, or about 0.000000007%
> of the total time since the big bang.
>
> 5. There are perhaps 200 billion galaxies in the observable universe, and
> nobody even knows if the diameter of the universe is 78 billion light years
> in diameter, or infinite.
>
> Given the above, I'd say the chances there this is life out there are
> considerably greater than the chances of winning the mega-millions lottery.
> Whether any of that life evolves to the point of developing what we might
> call intelligence before catastrophe intervenes is an interesting question.
> There have been 5 mass extinctions on earth:
>
> • The first great mass extinction event took place at the end of the
> Ordovician, when according to the fossil record, 60% of all genera of both
> terrestrial and marine life worldwide were exterminated.
> • 360 million years ago in the Late Devonian period, the environment
> that had clearly nurtured reefs for at least 13 million years turned hostile
> and the world plunged into the second mass extinction event.
> • The fossil record of the end Permian mass extinction reveals a
> staggering loss of life: perhaps 80–95% of all marine species went extinct.
> Reefs didn't reappear for about 10 million years, the greatest hiatus in reef
> building in all of Earth history.
> • The end Triassic mass extinction is estimated to have claimed about
> half of all marine invertebrates. Around 80% of all land quadrupeds also went
> extinct.
> • The end Cretaceous mass extinction 65 million years ago is famously
> associated with the demise of the dinosaurs. Virtually no large land animals
> survived. Plants were also greatly affected while tropical marine life was
> decimated. Global temperature was 6 to 14°C warmer than present with sea
> levels over 300 metres higher than current levels. At this time, the oceans
> flooded up to 40% of the continents.
>
> Were it not for that last one, intelligent life on earth might be
> sauron-based, rather than (arguably) hominid-based. However, having observed
> that the demonstrated proven benefits of intelligence on earth include
> religion, religious war, a fascination with building enough nuclear weapons
> to guarantee another mass extinction event, and a propensity for breeding
> beyond the capacity of the planet to supply food and water for a rapidly
> growing population of billions, I'd say that the odds were pretty good that
> we won't be around to meet another intelligence, should one ever happen to
> come looking this way.
>
> However, if you are a Sarah Palin or Rick Santorum or Rick Perry-class
> creationist, please ignore all of the above. Humans and dinosaurs were
> happily co-existing from the beginning, 6,000 years ago, and God made us in
> his image, and we are the chosen. Which makes the whole question of other
> intelligence completely immaterial.
>
> If you are a Mitt Romney-class Mormon, you may pass directly on to Kolub; the
> issue of intelligent life is obviously of no meaning to you.
>
> --Doug
>
> On Sat, Mar 31, 2012 at 11:09 AM, Owen Densmore <[email protected]> wrote:
> >
> > I got to thinking a bit more about an assumption I (and I bet most of us)
> > have held, that surely there is "intelligent" life on other planets, one
> > capable of technology .. thus SETI's radio search. Surely it is hubris to
> > claim humanity is somehow unique, just look at the diversity of our own
> > world! Thus there's got to be lots of intelligent life out there, right?
> >
> > (Yes, I know, this is pretty vague, and we're intelligent only for very
> > small values of intelligent.)
> >
> > But listening to a TED by Hawking, I was impressed with his somewhat
> > measured approach: that we have not found a radio source within 200-400
> > light years. I believe his choice of distance had to do with our own
> > development of radio a couple of centuries ago.
> >
> > That got me reading up on just how long we've been around, and how long
> > other civilizations could have existed. Very roughly speaking, the big
> > bang was 14 billion years ago, our sun is 4.5 billion years old, and the
> > earth is 4 billion years old.
> >
> > Well, that sounds like we're late to the game: 4 billion years old in a
> > universe 14 billion years old. But wait a minute, we know we're the result
> > of star-stuff, the heavy elements. The big bang was only able to muster
> > nuclei of fairly low weight, lithium say .. possibly a bit more. The first
> > generation of stars, therefor were fairly odd, huge and short lived. And
> > the second generation of stars were less heavy element rich than our sun,
> > which makes it at best third generation. http://goo.gl/gV54S
> >
> > So given only 14BY for building solar systems, and assuming the requirement
> > for an at least third generation sun, we may be as young as likely a life
> > form possible.
> >
> > So SETI is likely playing a loosing game, we're young enough that the
> > statistics may be that, yes there is life out there, but it's pretty young
> > too and maybe is no more advanced than we are. (Maybe that is Hawking's
> > couple of centuries limit) Of course we're talking about a few centuries,
> > which would make a huge difference in technology, but still.
> >
> > Hawking does end with a grim comment others have made: maybe civilizations
> > are short lived .. they self destruct or fall prey to destructive events
> > (meteors, comets).
> >
> > -- Owen
> >
> > ============================================================
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> > Meets Fridays 9a-11:30 at cafe at St. John's College
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>
>
>
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============================================================
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