[LINK] "Searching for Interstellar Communications"

[rfmcdonald]

I'd like to thank james_nicoll and ultimately Centauri Dreams for linking to the paper "Searching for Interstellar Communications", co-written by physicists Guiseppe Cocconi and Philip Morrison (Nature, Vol. 184, Number 4690, pp. 844-846, September 19, 1959), for starting the on-going discourse about how to find extrateerrestrial civilizations via radio signals.

No guesswork here is as good as finding the signal. We expect that the signal will be pulse-modulated with a speed not very fast or very slow compared to a second, on grounds of band-width and of rotations. A message is likely to continue for a time measured in years, since no answer can return in any event for some ten years. It will then repeat, from the beginning. Possibly it will contain different types of signals alternating throughout the years. For indisputable identification as an artificial signal, one signal might contain, for example, a sequence of small prime numbers of pulses, or simple arithmetical sums.

The first effort should be devoted to examining the closest likely stars. Among the stars within 15 light years, seven have luminosity and lifetime similar to those of our Sun. Four of these lie in the directions of low background. They are Tau Ceti, 02 Eridani, Eta Eridani, and Eta Indi. All these happen to have southern declinations. Three others, Alpha Centauri, 70 Ophiucus and 61 Cygni, lie near the galactic plane and therefore stand against higher backgrounds. There are about a hundred stars of the appropriate luminosity among the stars of known spectral type within some fifty light years. All main-sequence dwarfs between perhaps GO and K2 with visual magnitudes less than about +6 are candidates.

It's certainly ongoing, and the discussion has advanced significantly beyond this first consideration, but going back to the basics is always a good thing.