From: LARRY KLAES (ljk4_at_msn.com)
Date: Fri Apr 04 2008 - 12:32:16 PDT
>From: Centauri Dreams <gilster_at_mindspring.com>
>Reply-To: Centauri Dreams <gilster_at_mindspring.com>
>Subject: Centauri Dreams
>Date: Fri, 4 Apr 2008 14:03:42 -0500 (CDT)
>
>Centauri Dreams
>
>///////////////////////////////////////////
>Dyson Spheres: Hoping to Be Surprised
>
>Posted: 04 Apr 2008 11:50 AM CDT
>http://www.centauri-dreams.org/?p=1806
>
>
>How accurate do you think we are in projecting what extraterrestrial
>civilizations might do? The question is prompted by recent speculation on
>Dyson spheres and the supposition that advanced cultures will invariably
>build them. After all, a Dyson sphere would seem to be a natural for beings
>who wanted to extract as much usable power as possible from their sun. Such
>a civilization, which Nikolai Kardashev thought of as Type II, using all
>the power of its star, would doubtless think breaking up a local gas giant
>and using it to enclose that star made sense.
>
>
>
>So lets assume for a moment that extraterrestrial beings follow a game plan
>we humans have devised. And lets take it to the next logical level. Going
>from Type II to Kardashevs Type III, cultures that exploit the resources of
>entire galaxies, we would have to admit the possibility of creating Dyson
>spheres around every star in a galaxy, an interesting thought when you ask
>what methods are best for detecting signs of intelligent life elsewhere in
>the universe.
>
>Image: A Dyson sphere allows a civilization to exploit maximal energy from
>its star. Excess infrared could conceivably mark its location to
>SETI-oriented astronomers. Credit: Wikimedia Commons.
>
>Hunting for Dyson Spheres
>
>For instead of listening for radio broadcasts or looking for optical
>beacons, finding Dyson spheres, either by themselves or in a wavefront
>spreading through a galaxy, is an observational SETI that could be
>successful even if its targets have no interest in trying to contact us.
>Thus Bruce Dormineys recent essay on SETIs new wave, the idea of searching
>for distinctive signatures of Dyson spheres and their derivatives.
>Dorminey, author of the fine Distant Wanderers: The Search for Planets
>Beyond the Solar System (2001), tracked down people who have begun looking
>for such objects. People like Dan Wertheimer (UC-Berkeley), who analyzed a
>thousand solar-type stars (having culled those at least a billion years
>old), looking for excess infrared. 32 stars made the final cut and were
>examined for radio or optical transmissions, with no sign of alien
>intelligence.
>
>Dick Carrigan (retired from Fermilab) has spent five years on 11,124
>sources identified by the Infrared Astronomical Satellite (IRAS). Its all
>in Dormineys essay, how Carrigan went after objects with an infrared
>temperature of 200-600 K, looking for the radiation of waste heat, again
>finding no signs of intelligent activity when scanning several contenders
>for anomalous radio signals. Or consider James Annis (Fermilab), who
>analyzes not single stars but entire galaxies looking for signs of
>engineering.
>
>Heres Annis on the possibilities, looking for a galaxy that might emit only
>100th of one percent of the light expected from it, the possible signature
>of astroengineering at work:
>
>If you were to see obvious dust clouds around a candidate galaxy in the
>infrared, then it could be a dusty starburst galaxy where the dust is very
>clumpy and you can see ongoing star formation. But if you got an infrared
>galactic image that was completely smooth with no lumpiness, that’s an
>interesting object.
>
>Dorminey notes that to achieve this level of dimming on a galactic scale, a
>Type III civilization would need to have gone to work on just about every
>star in its galaxy. Which cannot, of course, be ruled out when youre
>dealing with technologies at this level. Even here, though, we have to
>avoid being too doctrinaire. One argument against intelligent life in the
>nearby cosmos is the lack of Type III engineering, the assumption being
>that any culture that could harness an entire galaxys power would already
>be blindingly obvious to us. My guess, says Dan Wertheimer, is that just
>from the astronomical data on file we would have discovered such a
>civilization by accident.”
>
>Alien Technologies, Human Assumptions
>
>Would we? That would bring us back to Type II as the only kind of advanced
>civilization to look for, but I disagree with Wertheimer. In trying to
>understand hypothetical alien cultures, were assuming we can extrapolate
>forward from our own technology to what we would do if we had the necessary
>tools. Thus Dysons sphere, maybe 150 million kilometers in radius, a
>meters-thick shell rotating around its star. We can figure this to be a
>desirable outcome, so we assume aliens would think as we do. But would
>they? Perhaps a Type II society would have made breakthroughs in energy
>management that would render a Dyson sphere a historical curiosity, like
>some early 19th Century idea of a flying machine powered by flapping wings
>and a steam engine.
>
>No, I cant imagine what those breakthroughs would be, but then, thats the
>point. How accurate can we be about predicting what science will find down
>the road? As Brian Wang has recently noted, projecting technology on our
>own planet out even fifty to a hundred years is all but impossible. For
>that matter, how can we be sure advanced engineering works would even be
>detectable, much less understood? My border collies are supremely
>intelligent dogs (one of them, anyway), but do they understand the
>difference between artifact and natural object? Do they know what a
>technology is? Yet the gap between border collie and human could be minor
>compared to the gap between human and extraterrestrial, especially if the
>latter has been developing its own technology for millions of years, if not
>billions.
>
>None of which is to downplay what Wertheimer, Carrigan and Annis have done.
>Although the odds are daunting, Im all for keeping our eyes open, and if a
>search for anomalous stars with excess infrared emission turns up
>interesting objects, lets by all means investigate them. If we find
>galaxies with high infrared and low optical luminosity, lets subject them
>to detailed scrutiny. But lets not make any more assumptions than we have
>to. A negative result in a search for Dyson spheres or anomalous galaxies
>may only point to the limitations of our ability to project where
>technologies go as societies enter higher Kardashev levels.
>
>Anomalous Galaxies and Their Uses
>
>
>
>
>
>If you want to find something anomalous about galaxies, consider the case
>of NGC 5907, a spiral galaxy 39 million light years away. Observations of
>this galaxy in 1998 by Michael Liu (UC-Berkeley) and an international team
>of astronomers showed an odd mix of stars. Expecting to see hundreds of
>bright stars in their field of view, the researchers found only a few.
>Evidently twenty times more light comes from dwarfs than giant stars in the
>halo of this galaxy. Liu, lead author of the paper on this work, described
>the finding this way:
>
>Our results force us to turn to more esoteric descriptions of the stellar
>content of NGC 5907s halo. In particular, our data combined with the
>measured colors of the halo suggest a very metal-poor stellar population
>with an enormous excess of faint dwarfs. This is the first direct evidence
>of a substantial population of stars which is essentially all dwarf stars.
>Such a population has been invoked in the past as a constituent of the dark
>matter making up galaxy halos.
>
>Image: NGC 5907. Can an entire galaxy become the subject of advanced
>engineering? If so, would we recognize the result? Credit: Brad Ehrhorn,
>Dan Azari, and Chris Lasley/Kitt Peak Advanced Observing Program.
>
>Larry Klaes recently noted this study as an example of anomalies that could
>conceivably be related to engineering on the galactic scale. His point was
>not that NGC 5907 demonstrates such, but that given the vast number of
>galaxies we have to observe, our attempts to examine them in the context of
>SETI are in their infancy. And if I am right that a Type III civilization
>is going to be extremely difficult to recognize, then hunting for galactic
>anomalies makes sense in the context of a broader search, rather than one
>focused on a particular range of emissions.
>
>There is no question that we are re-examining the nature of the SETI search
>as we grapple with such issues. In radio frequencies, we are most likely to
>be able to receive a directed signal, which means that here or in the
>optical range as well our best bet is to find extraterrestrials who
>already have an interest in communicating with us. Again, we have no reason
>to assume that alien cultures will feel such a need. Extending SETI into
>the realm of deep-sky observation (optical SETI is already doing this),
>using parameters that are both carefully selected yet open to anomalous
>result, seems a natural development.
>
>LOFAR and the Quest for Synergy
>
>
>
>Which brings us to LOFAR, the Low Frequency Array that is now planning to
>link radio detectors across Britain, France, Holland, Sweden and Germany.
>LOFAR studies a wide range of frequencies between 20 MHz and 80 MHz, and
>again between 120 MHz and 240 MHz. Its primary function is scientific,
>notes Robert Nichol of Portsmouth University in The Guardian:
>
>We will be looking for all sorts of different things with Lofar, added
>Nichol. We will make surveys of the skies to look for unexpected events;
>for things that go bump in the night, as it were. We will also be able to
>study the universes childhood years. We know a lot about the Big Bang, when
>the universe was created 13 billion years ago, and a lot about it now. But
>its early childhood years, around 500 million years after the Big Bang,
>remain a mystery.
>
>But Nichol adds that extraterrestrial broadcasts could potentially be found
>by LOFARs detectors. LOFAR, in other words, is a project dedicated to basic
>research that could have SETI ramifications on the periphery, and I think
>thats about the right mix. Those of us who doubt SETI will produce a
>confirmed extraterrestrial civilization any time soon would still like to
>see synergy between ongoing science and the attempt to make such
>discoveries. And wed like to be proven wrong in our SETI pessimism.
>Whichever wavelengths were studying, whatever objects in the heavens, lets
>keep our minds open and hope to be surprised.
>
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