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Fwd = How to Sort Signs of Artifical Life from the Real Thing (Shostak)

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  • Frits Westra
    Forwarded by: fwestra@hetnet.nl (Frits Westra) URL: http://www.space.com/searchforlife/seti_shostak_artificial_030130.html Original Date: Fri, 31 Jan
    Message 1 of 1 , Jan 31 11:18 AM
      Forwarded by: fwestra@... (Frits Westra)
      URL: http://www.space.com/searchforlife/seti_shostak_artificial_030130.html
      Original Date: Fri, 31 Jan 2003 10:44:09 -0500

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      How to Sort Signs of Artifical Life
      from the Real Thing

      By Seth Shostak
      Senior Astronomer, SETI Institute
      posted: 07:00 am ET
      30 January 2003

      Picture Jodie Foster, her eyes closed and a mildly bored look on her
      face. Shes wearing earphones and listening to the dull roar of the

      Now imagine Jodie 20 seconds later, when she hears something sounding
      like an unpleasant accident in the Boston Pops percussion section.
      Jodie knows shes scored big: the aliens are on the air.

      Still, how can she be sure shes picked up intelligence, and not just
      the cosmic gurgle of a completely natural object? How can she know
      shes not merely harkening to the ticking beat of a pulsar, the whoosh
      of a quasar, or perhaps the lasing bray of a molecular gas cloud?

      Because the signal sounds artificial, thats how.

      But what does that mean? In a universe awash in electromagnetic
      radiation filled with light and radio from a slew of objects that
      either emit or transmit how do we recognize a signal thats produced by
      intelligence? How do we define artificial?

      This problem is well known in the context of SETA, the Search for
      Extraterrestrial Artifacts. For example, any astronomer would be
      impressed by finding a stellar grouping in which a hundred stars were
      precisely arrayed on a 10 by 10 grid, and quickly conclude it was an
      alien construction. But not all artifacts are so unambiguous. For
      decades, the Viking Orbiter photo of the "Face on Mars" lathered up a
      lot of folk who felt that the appearance of this feature as seen by
      the Orbiters camera met the criteria of artificiality. Surprisingly,
      despite recent high-resolution photos of the "Face" that strongly
      challenge this conclusion, the debate continues. (Crop circles are a
      different matter: here the arguments fly not over whether or not
      theyre artificial, but who makes them.)

      In the late 1940s, a Soviet engineer and science fiction writer, A.P.
      Kazantsev, suggested that the famous Tunguska meteor of 1908 (which
      leveled trees as far away as 25 miles, and roasted 200 reindeer) might
      have been an exploded, nuclear-powered spacecraft from another world
      making this the Siberian equivalent of a purported alien landing
      mishap in Roswell, New Mexico four decades later. (Extraterrestrial
      rocket jockeys apparently can manage interstellar travel. Its the
      landings that befuddle them.) But the failure to find any tell-tale
      indications of nuclear reactions at Tunguska, and a better
      understanding of how rocks from space can explode in our atmosphere,
      has quelled this idea.

      Artificiality, some property that belies intelligence, is a crucial,
      and somewhat unresolved, concept in SETI. In the mid-1960s, a radio
      source found and cataloged by Caltech radio astronomers, CTA-102,
      piqued the interest of researchers in the U.S.S.R. This source
      apparently varied on time scales of 100 days and even less. Such
      relatively rapid change was, the Soviets averred, the result of
      deliberate signaling, and the famous physicist Nikolai Kardashev
      encouraged further study of CTA-102 as it might be a highly advanced
      society. As it turns out, CTA-102 is a quasar, not a beacon.

      In 1967, British radio astronomers found some radio sources that
      emitted exquisitely regular pulses, and tentatively labeled them LGMs:
      Little Green Men. Their methodical signals certainly seemed to be
      mechanical, rather than natural. Once again however, the transmitters
      were found to be odd but not alien. The Cambridge astronomers had
      discovered pulsars.

      Its worth asking what about a pulsars precise radio heartbeat would
      tell you that theyre not artificial. To begin with, the emissions
      occur over a wide bandwidth; a broadcast splatter rather similar to
      the static caused by lightning, and clearly a very inefficient way to
      transmit information. In addition, endless, regular pulses dont convey
      any information. Just as an interminable flute tone would not be music
      (except, perhaps, to Andy Warhol), so too is an unceasing clock tick
      devoid of any message. Within a few years of their discovery, pulsars
      were found all over the sky, a further indication that they were
      natural members of the galactic bestiary, rather than some societys
      attempt to get in touch. Finally, astrophysicists quickly confected a
      plausible theory that pulsars are collapsed stars. This has not only
      explained their radio (and optical) ticks, but also even predicted the
      fact that they slow down.

      Is the ambiguity of the Cambridge discovery a thing of the past? Do
      contemporary SETI researchers have such a firm hold on what
      constitutes an artificial signal that theyll immediately recognize it
      when they find it? Or need we be concerned that, in the words of The
      Who, "we dont get fooled again"? Jodie Foster heard a rhythmic sound
      effect that was, to her, unambiguous. Soon thereafter, her SETI team
      discovered an old TV broadcast layered into the received signal. This
      firmly tagged it as not only extraterrestrial, but intended for us. No
      uncertainty there. But the scenario depicted in Contact could only
      play out in real life if aliens are very nearby.

      A true SETI signal is likely to be quite different from its fictional
      counterparts. In the next installment of this two-part saga, well
      explore how todays SETI scientists hope to discern that most
      intangible cosmic commodity: artificiality.

      © 1999-2003 SPACE.com, Inc. ALL RIGHTS RESERVED.

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