Interstellar communications

Taking a value of 107 for N would mean that in our galaxy (with its perhaps 100 billion stars), there could be several million planets with life forms capable of interstellar communication. However, if these were distributed statistically, the nearest would still be 200 light years away from Earth. One point is important the term probability used in the Drake equation is interpreted in the sense of subjective probability (a term from the nomenclature used by statisticians and probability theorists), as the numerical value of this probability is determined only by the experience of the scientist concerned (Casti, 1989). Casti also provides more information on the Drake factors (apart from the factor fs) in the chapter Where are they then In summary, we can say that the Drake equation is a first attempt to quantify the ETI problem in order to move from the area of science fiction and pure speculation to that of serious scientific debate. 

Radio-astronomy searches (Project Ozma) for communications from intelligent extraterrestrial beings have been carried out at this frequency see Interstellar Communication, A. G. W. Cameron, etL, Benjamin, New York, 1963 Communication With Extraterrestrial Inteltt-genee, C. Sagan, ed. MIT Press, 1973. 

Ibid. See also A.T. Lawton, Infrared interstellar communication, Spaceflight, 13(3) 83-85 (1971) C. H. Townes, At what wavelengths should we search for signals from extraterrestrial intelligence Proceedings of the National Academy of Science U.S.A. 80 1147-1151 (1983) J. D. Rather, Lasers Revisited their superior utility for interstellar beacons, communications, and travel, Journal of the British Interplanetary Society, 44 385-392 (1991). 

I doubt it will come to that," Mae Ortlieb said. "As you said, they are a disorganized rabble. We control interstellar communications, it should be enough to prevent them merging to form a genuine threat."... 

Maser transitions have been observed in many important molecules and have been used to carry out surveys of the entire sky. The 22.235 GHz water maser transition is the strongest transition in the radio universe and represents an interesting candidate for an interstellar broadcast frequency. If extraterrestrial intelligence is trying to communicate with us, the choice of the broadcast frequency is an important one and would be known to all intelligent life. Of course it would have a different label, 22.235 GHz being a distinctly Earthly label, but it is a fundamental transition frequency and is observed everywhere. Other maser transitions include the 6.7 and 12.2 GHz methanol maser, the SiO maser v = 1, J = 7-6, 301.8 GHz, which occurs between levels in the first vibration state of the SiO molecule, and finally the OH maser first discovered in 1963 and buried deep in the 2n3/2 electronic state of the hydroxyl radical near 18 cm. This is actually four transitions at 1612, 1665, 1667 and 1720 MHz, all of which must be seen as a group but not necessarily of the same intensity. 

G. W. Cameron s Scientific Perspectives on Extraterrestrial Communication gives an excellent overview of current thinking on the subject. R. N. Bracewell s contribution printed in the same work was the basis of my own ideas about interstellar probes. 

Photochemical transformation of organic compounds and in particular PAHs on ice, as a medium, has not received much attention from the photochemical community. As a result, information on such transformations is limited. Astrophysical research on water ice, on the other hand, has evolved at a rapid pace in recent years after its discovery on outer solar system bodies and in interstellar space [21-23]. A recent review article by Klan and Holoubek [24] on ice photochemistry provides the current knowledge on the distribution, accumulation, and chemical/photo chemical transformation of persistent bio accumulative and toxic compounds in water ice. Since PAHs constitute a substantial portion of the interstellar carbon inventory [25,26], their photochemical behavior is of paramount importance in the radiative processing of interstellar ices. 

The optical range presents some relevant advantages with respect to the RF/MicroWave range, as it is a higher bandwith, that let us transfer information faster, and the fact that the interstellar medium produces a smaller perturbation on it. These features of the optical communication were known in 1959 when the SETI projects in the RF began, but only with the development of LASER... 

Ambrogelly et al (2007) Natural expansion of the genetic code. Nature Chem Biol 3 29-35 Bernstein MP, Dworkin JP, Sanford SA et al (2002) Racemic amino acids from the ultraviolet photolysis of interstellar ice analogues. Nature 416 401 —403 Blackmond DG, Klussmann M (2007) Spoilt for choice assessing phase behaviour models for the evolution of homochirality. Chem Commun 3990-3996 Breslow R (1959) The mechanism of the formose reaction. Tetrahedron Lett 21 22-26 Breslow R et al (2010) Initiating prebiotic homochirality on Earth. Orig Life Evol Biosph 40 11-26... 

Jobhn, C., Masselon, C, Boissel, F, de Parseval, R, Martinovic, S., Muller, JJ7 (1997) Simulation of interstellar aromatic hydrocarbons using ion cyclotron resonance. Prehminary results. Rapid Communications in Mass Spectrometry, 11,1619-1623. 

Analytical Chemistry Collision-Induced Spectroscopy Hydrogen Bond Infrared Spectroscopy Interstellar Matter Ion Kinetics and Energetics Microwave Communications Millimeter Astronomy Quantum Chemistry Time... 

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