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246  SEARCHING FOR GODot
     "Appendix F"   MIT Press,  1973
      (Communication with Extraterrestrial Intelligence CETI
       edited by Carl Sagan)

     I assume (1) the angels are still within the galaxy, and (2)
their average "progress" can best be estimated as equal to ours +/-
millennia.
     Then a reasonable proportion will have reached the stage of 
interstellar (wisely "unmanned") travel--but not of being able to 
discriminate Earth from multitude. (The UFO seers are incredibly
geocentric in their conceits.)
     Ergo: if there is a transmitter, it will be at the unique point
in the Galaxy--as far as I can imagine, the barycenter is just that.
This will be even more self-evident to that subset of angels who
live a few hundred or thousand light years from the center.  By the
way, would they have more interstellar dust to use for rocket
"fuel"?
     Further I would favor looking for signals in the frequency
domain, as compared with the advantages of time-averaging.  The
operational program is to look for unexpected line-structure, super-
imposed on the doppler-broadened lines of, say, the 21-cm
H microwave emission.  Which we have good reason to do anyhow.
     But if one takes such programs seriously, we must also contemplate
the political imperatives of establishing terrestrial radio
silence vis a vis emissions that might be detected elsewhere.
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