SETI

SETI (pronounced {{IPA|}}, to rhyme with "Betty") stands for Search for Extra-Terrestrial Intelligence.

Probe SETI and SETA Experiments

The possibility of using interstellar messenger probes in the search for extraterrestrial intelligence was first suggested by Ronald N. Bracewell in 1960, and the technical feasibility of this approach was demonstrated by the British Interplanetary Society's starship study Project Daedalus in 1978. Starting in 1979, Robert Freitas advanced arguments http://www.rfreitas.com/Astro/InterstellarProbesJBIS1980.htm http://www.rfreitas.com/Astro/ProbeMyths1983.htm http://www.rfreitas.com/Astro/TheCaseForInterstellarProbes1983.htm for the proposition that physical space-probes are a superior mode of interstellar communication to radio signals.

Related Topics:
Ronald N. Bracewell - Project Daedalus - Robert Freitas

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Subsequently, in a September 2004 paper featured on the cover of Nature Magazine

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v431/n7004/index.html,

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Christopher Rose and Gregory Wright showed that inscribing a message

Related Topics:
Christopher Rose - Gregory Wright

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

in matter and transporting it to the destination is vastly more energy-efficient

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

than communication using electromagnetic waves if the message can tolerate

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

delivery delay beyond light transit time

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

http://www.nature.com/nature/journal/v431/n7004/full/nature02884.html

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

http://www.winlab.rutgers.edu/~crose/papers/nature.pdf

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

http://www.winlab.rutgers.edu/~crose/cgi-bin/cosmic23.html.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Thus, a solarcentric Search for Extraterrestrial Artifacts (SETA) http://www.rfreitas.com/Astro/SETAJBISNov1983.htm would seem to be

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

favored over the more traditional radio or optical searches.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Much like the "preferred frequency" concept in SETI radio beacon theory, the Earth-Moon or Sun-Earth libration orbits http://www.rfreitas.com/Astro/SearchIcarus1980.htm might therefore constitute the most universally convenient parking places for automated extraterrestrial spacecraft exploring arbitrary stellar systems. A viable long-term SETI program may be founded upon a search for these objects.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

In 1979 Freitas and Valdes http://www.rfreitas.com/Astro/SearchIcarus1980.htm conducted a photographic search of the vicinity of the Earth-Moon triangular libration points L4 and L5, and of the solar-synchronized positions in the associated halo orbits, seeking possible orbiting extraterrestrial interstellar probes, but found nothing to a detection limit of about 14th magnitude. The authors conducted a second more comprehensive photographic search for probes in 1982 http://www.rfreitas.com/Astro/SearchIcarus1983.htm that examined the five Earth-Moon Lagrangian positions and included the solar-synchronized positions in the stable L4/L5 libration orbits, the potentially stable nonplanar orbits near LI/L2, Earth-Moon L3, and also L2 in the Sun-Earth system. Again no extraterrestrial probes were found to limiting magnitudes of 17-19th magnitude near L3/L4/L5, 10-18th magnitude for L1/L2, and 14-16th magnitude for Sun-Earth L2.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

In June 1983, Valdes and Freitas http://www.rfreitas.com/Astro/TritiumSearch1986.htm used the 26-m radiotelescope at Hat Creek Radio Observatory to search for the tritium hyperfine line at 1516 MHz from 108 assorted astronomical objects, with emphasis on 53 nearby stars including all visible stars within a 20 light-year radius. The tritium frequency was deemed highly attractive for SETI work because (1) the isotope is cosmically rare, (2) the tritium hyperfine line is centered in the SETI waterhole region of the terrestrial microwave window, and (3) in addition to beacon signals, tritium hyperfine emission may occur as a byproduct of extensive nuclear fusion energy production by extraterrestrial civilizations. The wideband- and narrowband-channel observations achieved sensitivities of 5-14 x 10-21 W/m2/channel and 0.7-2 x 10-24 W/m2/channel, respectively, but no detections were made.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~