Sacred Texts  Esoteric & Occult   Mysteries
Buy CD-ROM   Buy Books about UFOs
Index  Previous  Next 

Detectability of Extraterrestrial Technological Activities

                 (word processor parameters LM=8, RM=75, TM=2, BM=2)
                       Taken from KeelyNet BBS (214) 324-3501
                            Sponsored by Vangard Sciences
                                     PO BOX 1031
                                 Mesquite, TX 75150
                        There are ABSOLUTELY NO RESTRICTIONS
                   on duplicating, publishing or distributing the
                        files on KeelyNet except where noted!
                                   January 16,1994
               This file shared with KeelyNet courtesy of Rick Lawler.
                              THE ELECTRONIC JOURNAL OF
                         Volume 5, Number 5 - December 1993
        The Electronic Journal  of  the Astronomical Society of the Atlantic
        (EJASA) is published monthly by  the  Astronomical  Society  of  the
        Atlantic, Incorporated.  The   ASA  is  a  non-profit   organization
        dedicated to the  advancement  of amateur and professional astronomy
        and space exploration, as well as  the  social and educational needs
        of its members.
                             Guillermo A. Lemarchand [1]
                     Center for Radiophysics and Space Research
                     Cornell University, Ithaca, New York, 14853
             1 - Visiting Fellow under ICSC World Laboratory scholarship
             Present address:  University of Buenos Aires,
                               1425 - Buenos Aires,
              This paper  was  originally  presented  at the  Second  United
            Nations/European Space Agency Workshop on Basic Space Science
              Co-organized by The Planetary Society in cooperation with
           the Governments of Costa Rica and Colombia, 2-13 November 1992,
                       San Jose, Costa Rica - Bogota, Colombia
        If we want  to  find  evidence for the existence of extraterrestrial
        civilizations (ETC), we must work  out an observational strategy for
        detecting this evidence  in order to establish the various  physical
        quantities in which it involves.  This information must be carefully
        analyzed so that  it  is neither over-interpreted nor overlooked and
        can be checked by independent researchers.
                                       Page 1
        The physical laws  that govern the Universe are the same everywhere,
        so we can use our knowledge of these  laws  to  search  for evidence
        that would finally   lead   us   to   an  ETC.   In   general,   the
        experimentalist studies a   system   by   imposing  constraints  and
        observing the system's response to a controlled stimulus.
        The variety of these constraints  and  stimuli  may  be  extended at
        will, and experiments  can  become  arbitrarily  complex.    In  the
        problem of the  Search  for Extraterrestrial Intelligence (SETI), as
        well as in conventional astronomy,  the  mean  distances are so huge
        that the "researcher" can only observe what is received.   He or she
        is entirely dependent  on  the carriers of information that transmit
        to him or her all he or she may learn about the Universe.
        Information carriers, however, are  not  infinite  in  variety.  All
        information we currently have about the Universe  beyond  our  solar
        system has been  transmitted  to  us  by  means  of  electromagnetic
        radiation (radio, infrared, optical,  ultraviolet, X-rays, and gamma
        rays), cosmic ray particles (electrons and atomic nuclei),  and more
        recently by neutrinos.
        There is another possible physical carrier, gravitational waves, but
        they are extremely difficult to detect.
        For the long  future  of humanity, there have also been speculations
        about interstellar automatic probes  that  could  be  sent  for  the
        detection of extrasolar life forms around the nearby stars.
        Another set of   possibilities   could   be   the    detection    of
        extraterrestrial artifacts in  our  solar system, left here by alien
        intelligences that want to reveal their visits to us.
        Table 1 summarizes the possible "information  carriers" that may let
        us find the evidence of an extraterrestrial civilization,  according
        to our knowledge  of  the  laws  of  physics.  The classification of
        techniques in Table  1  is  not  intended  to  be  complete  in  all
        Thus, only a few fundamental particles have been listed.  No attempt
        has been made  to  include any antiparticles.  This  classification,
        like any such  scheme,  is also quite arbitrary.  Groupings could be
        made into different "astronomies".
                                       Page 2
                                TABLE 1: Information Carriers
                                         | Radio Waves
                                         | Infrared Rays
                       |-                | Optical Rays
                       | Photon Astronomy| Ultraviolet Rays
                       |                 | X-Rays
            Boson      |                 | Gamma Rays
            Astronomy  |                 |-
                       | Graviton Astronomy: Gravity Waves
                       |-                     |-
                                              | Neutrinos
                     |-           |-  Fermions| Electrons   |-
                     | Atomic     |           | Protons     | Cosmic
                     | Microscopic|           |-            | Rays
                     | Particles  |   Heavy Particles       |-
           Particle  |            |-
           Astronomy |                      |-
                     | Macroscopic Particles|       Meteors, meteorites,
                     | or objects           |       meteoritic dust
                     |-                     |-
                         | Space Probes
            Direct       | Manned Exploration
            Techniques   |  ET  Astroengineering  Activities  in  the  Solar
        The methods of collecting this information  as  it  arrives  at  the
        planet Earth make it immediately obvious that it  is  impossible  to
        gather all of  it  and measure all its components.  Each observation
        technique acts as an information filter.   Only  a fraction (usually
        small) of the complete information can be gathered.   The  diversity
        of these filters  is  considerable.   They  strongly  depend  on the
        available technology at the time.
        In this paper a review of the advantages  and  disadvantages of each
        "physical carrier" is examined, including the case that the possible
        ETCs are using them for interstellar communication purposes, as well
        as the  possibility  of  detection  activities  of  extraterrestrial
                Classification of Extraterrestrial Civilizations
        The analysis of  the  use  of  each  information  carrier are deeply
        connected with the assumption of  the  level  of  technology  of the
        other civilization.
        Kardashev (1964) established a general criteria regarding  the types
        of activities of   extraterrestrial   civilizations   which  can  be
        detected at the present level of development.  The most general
        parameters of these activities are  apparently ultra-powerful energy
        sources, harnessing of  enormous solid masses, and the  transmission
        of large quantities of information of different kinds through space.
        According to Kardashev, the first two parameters are a prerequisite
        for any activity of a supercivilization.  In this way, he suggested
                                       Page 3
        the following classification     of     energetically    extravagant
            TYPE I:   A level "near" contemporary  terrestrial  civilization
                     with an  energy  capability  equivalent  to  the  solar
                     insolation on Earth, between 10exp16 and 10exp17 Watts.
            TYPE II:  A civilization capable of utilizing and channeling the
                      entire radiation output of its star.  The energy
                      utilization would then be comparable to the luminosity
                      of our Sun, about 4x1026 Watts.
            TYPE III:  A civilization with access to the power comparable
                       to the luminosity of the entire Milky Way galaxy,
                       about 4x10exp37 Watts.
        Kardashev also examined  the  possibilities  in cosmic communication
        which attend the investment of most  of  the  available  power  into
        communication.  A Type II civilization could transmit  the  contents
        of one hundred  thousand  average-sized  books  across the galaxy, a
        distance of one  hundred  thousand   light   years,   in   a   total
        transmitting time of one hundred seconds.  The transmission  of  the
        same information intended  for  a  target  ten  million  light years
        distant, a typical intergalactic distance, would take a transmission
        time of a few weeks.
        A Type III civilization could transmit the same information over a
        distance of ten billion light years, approximately the radius of the
        observable Universe, with a transmission time of just three seconds.
        Kardashev and Zhuravlev (1992) considered  that the highest level of
        development corresponds to the highest level of utilization of solid
        space structures and the highest level of energy consumption.
        For this assumption, they considered the temperature  of solid space
        structures in the  range  3  Kelvin  s T s 300 K, the consumption of
        energy in the  range  1 Luminosity  (Sun)  s  L  s  10exp12  L(Sun),
        structures with sizes up to 100 kiloparsecs (kpc),  and distances up
        to Dw 1000 mega-parsecs (mpc).  One parsec equals 3.26 light years.
        Searching for these  structures  is  the  domain  of millimeter wave
        astronomy.  For the 300 Kelvin technology, the maximum emission
        occurs in the infrared region (15-20 micrometers) and searching is
        accomplished with infrared observations from Earth and space.  The
        existing radio surveys of the sky  (lambda  =  6 centimeters (cm) on
        the ground and lambda = 3 millimeters (mm) for the Cosmic Background
        Explorer (COBE) satellite) place an essential limit on the abundance
        of ETC 3   Kelvin   technology.   The  analyzes  of   the   Infrared
        Astronomical Satellite (IRAS)   catalog  of  infrared  sources  sets
        limitations on the abundance of 300 Kelvin technology.
                Information Carriers and the Manifestations of Advanced
                Technological Civilizations
                Boson and Photon Astronomy
        Electromagnetic radiation carries  virtually  all the information on
        which modern astrophysics    is    built.     The   production    of
        electromagnetic radiation is directly related to the physical
                                       Page 4
        conditions prevailing in   the  emitter.   The  propagation  of  the
        information carried by electromagnetic  waves  (photons) is affected
        by the conditions  along  its  path.   The trajectories  it  follows
        depend on the local curvature of the Universe, and thus on the local
        distribution of matter  (gravitational lenses), extinction affecting
        different wavelengths unequally,   neutral  hydrogen  absorbing  all
        radiation below the  Lyman  limit  (91.3  mm),  and  absorption  and
        scattering by interstellar  dust,  which  is  more  severe  at short
        Interstellar plasma absorbs  radio  wavelengths  of  kilometers  and
        above, while the  scintillations  caused  by  them   become  a  very
        important effect for  the  case  of  ETC  radio messages (Cordes and
        Lazio, 1991).
        The inverse Compton effect lifts low-energy photons to high energies
        in collisions with relativistic electrons,  while  gamma  and  X-ray
        photons lose energy  by  the direct Compton effect.   The  radiation
        reaching the observer  thus bears the imprint of both the source and
        the accidents of its passage though space.
        The Universe observable  with  electromagnetic  radiation  is  five-
        dimensional.  Within this   phase,  four  dimensions   -   frequency
        coverage plus spatial,  spectral,  and temporal resolutions - should
        properly be measured logarithmically with each unit corresponding to
        one decade (Tarter,  1984).  The fifth  dimension  is  polarization,
        which has four possible states:  Circular, linear,  elliptical,  and
        This increases the volume of logarithmic phase space fourfold.
        It is useful  to  attempt to estimate the volume of the search space
        which may need to be explored to detect an ETC signal.  For the case
        of electromagnetic waves, we have a "Cosmic Haystack" with an eight-
        dimensional phase space.  Three spatial  dimensions  (coordinates of
        the source), one  dimension  for  the  frequency  of  emission,  two
        dimensions for the   polarization,   one   temporal   dimension   to
        synchronize transmissions with receptions, and one dimension for the
        sensitivity of the receiver or the transmission power.
        If we consider  only  the microwave  region  of  the  spectrum  (300
        megahertz (MHz) to  300 gigahertz (GHz)), it is easy  to  show  that
        this Cosmic Haystack  has  roughly  10exp29  cells,  each  of 0.1 Hz
        bandwidth, per the number of directions  in  the  sky  in  which  an
        Arecibo (305-meter) radio  telescope  would need to  be  pointed  to
        conduct an all-sky  survey, per a sensitivity between 10exp(-20) and
        10exp(-30) [W m-2], per two polarizations.   The  temporal dimension
        (synchronization between transmission   and   reception)   was   not
        considered in the   calculation.    The  number  of  cells  increase
        dramatically if we  expand  our  search  to  other  regions  of  the
        electromagnetic spectrum.  Until now, only a small  fraction  of the
        whole Haystack has been explored (w 10exp(-15) - 10exp(-16)).
                                       Page 5
             TABLE 2: Characteristics of the Electromagnetic Spectrum
               (All the numbers that follows each 10 are exponents.)
        Spectrum      Frequency          Wavelength        Minimum Energy
        Region        Region [Hz]        Region [m]        per photon [eV]
         Radio         3x106-3x1010       100-0.01          10-8 - 10-6
         Millimeter    3x1010-3x1012      0.01-10-4         10-6 - 10-4
         Infrared      3x1012-3x1014      10-4-10-6         10-4 - 10-2
         Optical       3x1014-1015        10-6-3x10-7       10-2 - 5
         Ultraviolet   1015-3x1016        3x10-7-10-8       5 - 102
         X-rays        3x1016-3x1019      10-8-10-11        102 - 105
         Gamma-rays    r3x1019            s10-11            r105
        Radio Waves
        In the last  thirty  years,  most  of  the  SETI  projects have been
        developed in the radio region of  the  electromagnetic  spectrum.  A
        complete description of the techniques that all the present and
        near-future SETI programs are using for detecting extraterrestrial
        intelligence radio beacons  can be found elsewhere  (e.g.,  Horowitz
        and Sagan, 1993).  The general hypothesis for this kind of search is
        that there are   several   civilizations  in  the  galaxy  that  are
        transmitting omnidirectional radio  signals  (civilization Type II),
        or that these civilizations are beaming these kind  of  messages  to
        Earth.  In this  section  we  will discuss only the detectability of
        extraterrestrial technological manifestations in the radio spectrum.
        Domestic Radio Signals
        Sullivan et al (1978) and Sullivan (1981) considered the possibility
        of eavesdropping on  radio emissions  inadvertently  "leaking"  from
        other technical civilizations.  To better understand the information
        which might be derived from radio leakage, the case  of  our  planet
        Earth was analyzed.   As  an  example,  they  showed that the United
        States Naval Space  Surveillance   System   (Breetz,  1968)  has  an
        effective radiated power of 1.4x10exp (10) watts into a bandwidth of
        only 0.1 Hz.   Its  beam  is  such  that  any  eavesdropper  in  the
        declination range of zero to 33 degrees (28 percent of the sky) will
        be illuminated daily  for  a  period of roughly seven seconds.  This
        radar has a detectability range of  leaking  terrestrial  signals to
        sixty light years  for an Arecibo-type (305-meter)  antenna  at  the
        receiving end, or  six  hundred light years for a Cyclops array (one
        thousand dishes of 100-meter size each).
        Recently Billingham and Tarter (1992) estimated the maximum range at
        which radar signals from Earth could be detected by a search similar
        to the NASA High Resolution Microwave  Survey  (HRMS)  assumed to be
        operating somewhere in  the  Milky  Way galaxy.  They  examined  the
        transmission of the  planetary  radar  of  Arecibo and the ballistic
        missile early warning  systems  (BMEWS).   For  the  calculation  of
        maximum range R, the standard range equation is:
                R=(EIRP/(4PI PHImin))exp(1/2)
                                       Page 6
        Where PHImin is  the  sensitivity  of  the search system in [W m-2].
        For the NASA HRMS Target Search PHImin  =  10exp  (-27)  and for the
        NASA HRMS Sky Survey PHImin w 10exp(-23) (f)exp(1/2), where f is the
        frequency in GHz.  Table 3 shows the distances where the Arecibo and
        BMEWS transmissions could  be  detected  by  a  similar   NASA  HRMS
          TABLE 3: HRMS Sensitivity for Earth's Most Powerful Transmissions:
                               ARECIBO PLANETARY RADAR
         (1) TARGETED SEARCH                   MAXIMUM RANGE (light years)
                  With CW detector               4217
                  With pulse detector            2371
                  With CW detector               94
                  With pulse detector            290
         (2) SKY SURVEY
                  CW detector                    77
                  CW detector                    9
         (1) TARGETED SEARCH
               Pulse transmit CW detector        6
               Pulse transmit pulse detector    19
         (2) SKY SURVEY
               Pulse transmit CW detector        0.7
        All these calculations assumed that the transmitting civilization is
        at the same level of technological evolution as ours on Earth.
        Von Hoerner (1961) classified the possible nature of the ETC signals
        into three general  possibilities:  Local communication on the other
        planet, interstellar communication  with  certain distinct partners,
        and a desire  to attract the attention of unknown  future  partners.
        Thus he named  them  as  local  broadcast,  long-distance calls, and
        contacting signals (beacons).  In  most of the past fifty SETI radio
        projects, the strategy  was  with  the  hypothesis  that  there  are
        several civilizations transmitting omnidirectional beacon signals.
        Unfortunately, no one has been able to show any positive evidence
        of this kind of beacon signal.
        Another possibility is   the   radio   detection   of   interstellar
        communications between an ETC planet  and  possible  space vehicles.
        Vallee and Simard-Normandin (1985) carried out a search for these
                                       Page 7
        kind of signals  near  the  galactic  center.   Because  one  of the
        characteristics of artificial transmitters (television, radar, etc.)
        is the highly  polarized  signal   (Sullivan  et  al,  1978),  these
        researchers made seven observing runs of roughly three  days each in
        a program to  scan  for  strongly  polarized  radio  signals  at the
        wavelength of lambda=2.82 cm.
        Radar Warning Signals
        Assuming that there is a certain  number  N  of civilizations in the
        galaxy at or  beyond  our  own  level  of  technical  facility,  and
        considering that each  civilization is on or near a planet of a Main
        Sequence star where  the planetoid  and  comet  impact  hazards  are
        considered as serious   as   here,  Lemarchand  and   Sagan   (1993)
        considered the possibility  for detecting some of these "intelligent
        activities" developed to  warn  of   these   potentially   dangerous
        Because line-of-sight radar astrometric measurements have much finer
        intrinsic fractional precision  than  their  optical  plane-of-sight
        counterparts, they are   potentially   valuable   for  refining  the
        knowledge of planetoid and comet  orbits.   Radar  is  an  essential
        astrometric tool, yielding both a direct range to  a  nearby  object
        and the radial  velocity  (with  respect  to  the observer) from the
        Doppler shifted echo (Yeomans et  al,  1987,  Ostro et al, 1991, and
        Yeomans et al, 1992).
        Since in our  solar  system, most of Earth's nearby  planetoids  are
        discovered as a  result  of their rapid motion across the sky, radar
        observations are therefore   often    immediately    possible    and
        A single radar   detection  yields  astronomy  with   a   fractional
        precision that is  several hundred times better than that of optical
        The inclusion of radar with the optical  data  in the orbit solution
        can quickly and  dramatically  reduce future ephemeris  uncertainty.
        It provides both impact parameter and impact ellipse estimates.
        This kind of radar research gives a clearer picture of the object to
        be intercepted and  the  orientation  of  asymmetric bodies prior to
        interception.  This is  particularly   important  for  eccentric  or
        multiple objects.
        Radar is also the unique tool capable for making  a  survey  of such
        small objects at  all  angles  with respect to the central star.  It
        can also measure reflectivity and polarization to obtain physical
        characteristics and composition.
        For this case,  we  can assume that  each  of  the  extraterrestrial
        civilizations in the  galaxy  maintains  as good a  radar  planetoid
        and/or comet detection and analysis facility as is needed, either on
        the surface of  their  planet, in orbit, or on one of their possible
        The threshold for the Equivalent Isotropic  Radiated Power (EIRP) of
        the radar signal  could  be  roughly estimated by the  size  of  the
        object (D) that they want to detect (according to the impact hazard)
                                       Page 8
        and the distance  to  the  inhabited  planet  (R),  in order to have
        enough time to avoid the collision.
        One of the  most  important  issues   for   the   success   of  SETI
        observations on Earth is the ability of an observer to detect an ETC
        signal.  This factor is proportional to the received  spectral  flux
        density of the radiation.  That is, the power per unit area per unit
        frequency interval.  The  flux  density  will be proportional to the
        EIRP divided by the spectral bandwidth  of  the  transmitting  radar
        signals B.
        The EIRP is  defined  as  the product of the transmitted  power  and
        directive antenna gain  in  the  direction of the receiver as EIRP =
        PT.G, where PT is the transmitting  power  and  G  the antenna gain.
        This quantity has units of [W/Hz].
        According to the kind of object that the ETC wants to detect (nearby
        planetoids, comets, spacecraft, etc.), the distance  from  the radar
        system and the  selected  wavelength,  a  galactic civilization that
        wants to finish a full-sky survey  in only one year, will arise from
        a modest "Type 0" (w10exp13 W/Hz, Rw0.4 A.U., Dw5000 m, and lambdaw1
        m) to the  transition  from "Type I" to "Type II" (w2x10exp24  W/Hz,
        Rw0.4 A.U., Dw10 m, lambdaw1 mm).
        Lemarchand and Sagan (1993) also presented a detailed description of
        the expected signal  characteristics,  as well as the most favorable
        positions in the sky to find one of  these  signals.  They also have
        compared the capability of detection of these transmissions  by each
        present and near future SETI projects.
        Infrared Waves
        There have been  some proposals to search in the infrared region for
        beacon signals beamed at us (Lawton, 1971, and Townes, 1983).
        Basically, the higher  gain  available   from  antennas  at  shorter
        wavelengths (up to 10exp14 Hz) compensates for the higher quantum
        noise in the   receiver   and  wider  noise  bandwidth   at   higher
        One concludes that  for  the  same  transmitter  powers and directed
        transmission which takes advantage of the high gain, the detectable
        signal-to-noise ratio is comparable at 10 micro-m and 21 cm.  Since
        non-thermal carbon dioxide (CO2) emissions have been detected in the
        atmospheres of both Venus and Mars (Demming and Mumma, 1983), Rather
        (1991) suggested the possibility that an advanced society could
        construct transmitters of enormous  power  by orbiting large mirrors
        to create a high-gain maser from the natural amplification  provided
        by the inverted atmospheric lines.
        An observation program  around three hundred nearby solar-type stars
        has just begun  (Tarter,  1992)   by   Albert  Betz  (University  of
        Colorado) and Charles Townes (University of California at Berkeley).
        These observations are currently being made on one  of  the two 1.7-
        meter elements of an IR interferometer at Mount Wilson observatory.
        On average, 21  hours  of  observing time per month is available for
        searching for evidence of technological signals.
                                       Page 9
        Dyson (1959, 1966)   proposed   the   search   for  huge  artificial
        biospheres created around a star by an intelligent species as part
        of its technological growth and expansion within a planetary system.
        This giant structure would most  likely  be  formed  by  a  swarm of
        artificial habitats and   mini-planets   capable   of   intercepting
        essentially all the radiant energy from the parent star.
        According to Dyson  (1966),  the mass of a planet like Jupiter could
        be used to  construct an immense  shell  which  could  surround  the
        central star, having a radius of one Astronomical Unit  (A.U.).  The
        volume of such a sphere would be 4cr2S, where r is the radius of the
        sphere (1 A.U.)  and  S the thickness.  He imagined a shell or layer
        of rigidly built objects Dw10exp6 kilometers in diameter arranged to
        move in orbits  around the star.   The  minimum  number  of  objects
        required to form  a  complete  spherical  shell  [2]  is  about  N=4
        PIrexp2/Dexp2w2x10exp5 objects.
        This kind of  object,  known  as  a  "Dyson Sphere", would be a very
        powerful source of infrared radiation.   Dyson predicted the peak of
        the radiation at ten micrometers.
        The Dyson Sphere is certainly a grand, far-reaching  concept.  There
        have been some  investigations to find them in the IRAS database (V.
        I. Slysh, 1984;  Jugaku  and  Nishimura,  1991;  and  Kardashev  and
        Zhuravlev, 1992).
            2 - The concept of this extraterrestrial construct was first
            described in the science fiction novel STAR MAKER by Olaf
            Stapledon in 1937.
        Optical Waves
        In the radio domain, there have been several proposals  to  use  the
        visible region of  the  spectrum  for  interstellar  communications.
        Since the first proposal by Schwartz  and  Townes  (1961), intensive
        research has been  performed  on  the  possible use  of  lasers  for
        interstellar communication.
        Ross (1979) examined  the  great advantages of using short pulses in
        the nanosecond regime at high energy  per  pulse  at  very  low duty
        This proposal was  experimentally explored by Shvartsman  (1987) and
        Beskin (1993), using a Multichannel Analyzer of Nanosecond Intensity
        Alterations (MANIA), from  the  six-meter telescope in Russia.  This
        equipment allows photon arrival  times  to  be  determined  with  an
        accuracy of 5x10exp(-8)  seconds,  the  dead time being  3x10exp(-7)
        seconds and the  maximum  intensity  of  the incoming photon flux is
        2x10exp4 counts/seconds.
        In 1993, MANIA  was  used  from  the  2.15-meter  telescope  of  the
        Complejo Astronomico El  Leoncito  in  Argentina, to  examine  fifty
        nearby solar-type stars for the presence of laser pulses (Lemarchand
        et al, 1993).
        Other interesting proposals and analysis of the advantages of lasers
                                       Page 10
        for interstellar communications  have been performed by Betz (1986),
        Kingsley (1992), Ross (1980), and Rather (1991).
        The first international  SETI  in   the   Optical  Spectrum  (OSETI)
        Conference was organized by Stuart Kingsley, under  the  sponsorship
        of The International   Society   for  Optical  Engineering,  at  Los
        Angeles, California, in January of 1993.
        There have also been independent suggestions by Drake and Shklovskii
        (Sagan and Shklovskii,  1966)  that  the  presence  of  a  technical
        civilization could be  announced  by  the dumping of  a  short-lived
        isotope, one which  would  not  ordinarily  be expected in the local
        stellar spectrum, into the atmosphere of a star.  Drake suggested an
        atom with a  strong, resonant absorption  line,  which  may  scatter
        about 10exp8 photons  sec  -1  in  the stellar radiation  field.   A
        photon at optical  frequencies has an energy of about 10exp(-12) erg
        or 0.6 eV, so each atom will scatter  about  10exp(-4)  erg sec-1 in
        the resonance line.  If we consider that the typical  spectral  line
        width might be  about  1  ^O,  and  if  we assume that a ten percent
        absorption will be  detectable, then  this  "artificial  smog"  will
        scatter about (1A/5000A)x10exp(-1)  =  2x10exp(-5)   of   the  total
        stellar flux.
        Sagan and Shklovskii  (1966) considered that if the central star has
        a typical solar flux of 4x10exp33  erg  sec-1, it must scatter about
        8x10exp28 erg sec-1  for  the line to be detected.   Thus,  the  ETC
        would need (8x10exp28)/10exp(-4)  =  8x10exp32 atoms.  The weight of
        the hydrogen atom (mH) is 1.66x10exp(-24)  g,  so  the  weight of an
        atom of atomic weight n is nxmH grams.
        Drake proposed the used of Technetium (Tc) for this  purpose.   This
        element is not  found  on  Earth  and  its presence is observed very
        weakly in the Sun, in part because  it  is  short-lived.   Tc's most
        stable form decays  radioactively  within  an  average   of   twenty
        thousand years.  Thus,  for  the  case  of Tc, we need to distribute
        some 1.3x10exp11 grams, or 1.3x10exp5 tons, of this element into the
        stellar spectrum.  However, technetium  lines have not been found in
        stars of solar spectral type, but rather only in peculiar ones known
        as S stars.   We  must know more than we do about  both  normal  and
        peculiar stellar spectra  before we can reasonably conclude that the
        presence of an unusual atom in an  stellar  spectrum  is  a  sign of
        extraterrestrial intelligence.
        Whitmire and Wright  (1980)  considered  the possible  observational
        consequences of galactic  civilizations  which  utilize  their local
        star as a repository for radioactive  fissile  waste material.  If a
        relatively small fraction  of  the nuclear sources  present  in  the
        crust of a   terrestrial-type  planet  were  processed  via  breeder
        reactors, the resulting  stellar   spectrum   would  be  selectively
        modified over geological time periods, provided that  the star has a
        sufficiently shallow outer  convective  zone.   They  have estimated
        that the abundance anomalies resulting from the slow neutron fission
        of plutonium-239 and uranium-233 could  be duplicated (compared with
        the natural nucleosynthesis processes), if this process takes place.
        Since there are no known natural nucleosynthesis mechanisms that can
        qualitatively duplicate the   asymptotic  fission  abundances,   the
        predicted observational characteristics   (if  observed)  could  not
        easily be interpreted as a natural phenomenon.  They have suggested
                                       Page 11
        making a survey of A5-F2 stars for (1) an anomalous overabundance of
        the elements of praseodymium and neodymium, (2) the presence, at any
        level, of technetium or plutonium, and (3) an anomalously high ratio
        of barium to   zirconium.    Of  course,  if  a  candidate  star  is
        identified, a more detailed spectral analysis could be performed and
        compared with the predicted ratios.
        Following the same  kind  of  ideas,   Philip   Morrison   discussed
        (Sullivan, 1964) converting one's sun into a signaling light by
        placing a cloud of particles in orbit around it.   The  cloud  would
        cut enough light  to  make  the  sun appear to be flashing when seen
        from a distance, so long as the viewer was close to the plane of the
        cloud orbit.  Particles about one  micron in size, he thought, would
        be comparatively resistant  to disruption.  The mass  of  the  cloud
        would be comparable  to  that of a comet covering an area of the sky
        five degrees wide, as seen from  the  sun.   Every  few  months, the
        cloud would be shifted to constitute a slow form of  signaling,  the
        changes perhaps designed to represent algebraic equations.
        Reeves (1985) speculated  on  the  origin of mysterious stars called
        blue stragglers.  This class of star was first identified by Sandage
        (1952).  Since that time, no clear  consensus upon their origins has
        emerged.  This is  not,  however,  due to a paucity  of  theoretical
        models being devised.   Indeed,  a  wealth of explanations have been
        presented to explain the origins of  this star class.  The essential
        characteristic of the blue stragglers is that they  lie on, or near,
        the Main Sequence,  but  at  surface  temperatures  and luminosities
        higher than those stars which define the cluster turnoff.
        Reeves (1985) suggested the intervention  of  the  inhabitants  that
        depend on these  stars  for  light and heat.  According  to  Reeves,
        these inhabitants could  have  found  a  way  of keeping the stellar
        cores well-mixed with hydrogen,  thus  delaying  the  Main  Sequence
        turn-off and the ultimately destructive, red giant phase.
        Beech (1990) made a more detailed analysis of Reeves' hypothesis and
        suggested an interesting  list  of  mechanisms for  mixing  envelope
        material into the core of the star.  Some of them are as follows:
          o  Creating a "hot spot" between the stellar core and surface
             through the detonation of a series of hydrogen bombs.  This
             process may alternately be achieved by aiming "a powerful,
             extremely concentrated laser beam" at the stellar surface.
          o  Enhanced stellar rotation and/or enhanced magnetic fields.
             Abt (1985) suggested from his studies of blue stragglers that
             meridional mixing in rapidly rotating stars may enhance their
             Main Sequence lifetime.
        If some of  these  processes  can  be  achieved,  the  Main Sequence
        lifetime may be greatly extended by  factors  of ten or more.  It is
        far too early to establish, however, whether all the blue stragglers
        are the result of astroengineering activities.
        Editor's Note:  References to this paper will be published in Part 2
                        in the January 1994 issue of the EJASA.
                                       Page 12
        Related EJASA Articles -
          "Does Extraterrestrial Life Exist?", by Angie Feazel
           - November 1989
          "Suggestions for an Intragalactic Information Exchange System",
           by Lars W. Holm - November 1989
          "Radio Astronomy: A Historical Perspective",
           by David J.  Babulski - February 1990
          "Getting Started in Amateur Radio Astronomy",
           by Jeffrey M.  Lichtman - February 1990
          "A Comparison of Optical and Radio Astronomy",
           by David J.  Babulski - June 1990
          "The Search   for  Extraterrestrial  Intelligence  (SETI)  in  the
           Optical Spectrum, Parts A-F",
           by Dr. Stuart A. Kingsley - January 1992
          "History of the Ohio SETI Program", by Robert S. Dixon
           - June 1992
          "New Ears on the Sky: The NASA SETI Microwave Observing Project",
           by Bob Arnold, the ARC, and JPL SETI Project - July 1992
          "First International Conference on Optical SETI",
           by Dr.  Stuart A.  Kingsley - October 1992
          "Conference Preview: The Search for Extraterrestrial Intelligence
           (SETI) in the Optical Spectrum",
           by Dr. Stuart A. Kingsley - January 1993
           The Author -
                               Guillermo A. Lemarchand
                             Universidad de Buenos Aires
                           POSTAL ADDRESS: C.C.8 - Suc.25,
                                 1425-Buenos Aires,
                 PHONE: 54-1-774-0667                 FAX:     54-1-786-8114
                            December 1993 - Vol. 5, No. 5
                              Copyright (c) 1993 - ASA
          If you have comments or other information relating  to such topics
          as  this  paper covers,  please  upload to KeelyNet or send to the
            Vangard  Sciences  address  as  listed  on the  first  page.
               Thank you for your consideration, interest and support.
            Jerry W. Decker.........Ron Barker...........Chuck Henderson
                              Vangard Sciences/KeelyNet
                      If we can be of service, you may contact
                  Jerry at (214) 324-8741 or Ron at (214) 242-9346
                                       Page 13

Next: Secret Advanced Vehicles