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Detectability of Extraterrestrial Technological Activities


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Author Topic: Detectability of Extraterrestrial Technological Activities  (Read 669 times)
Jennifer Murdoch
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« on: February 04, 2010, 01:19:49 pm »

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)).


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