Active SETI
In contrast to Active SETI, METI pursues not a local, but a more global purpose – to overcome the Great Silence in the Universe, bringing to our extraterrestrial neighbors the long-expected annunciation “You are not alone!”Concern over METI was raised by the science journal Nature in an editorial in October 2006, which commented on a recent meeting of the International Academy of Astronautics SETI study group.
The program pledged "not to transmit any message until there has been a wide-ranging debate at high levels of science and politics on the risks and rewards of contacting advanced civilizations".
While trying to synthesize and project an Interstellar Radio Message (IRM), the receiving extraterrestrials (ETs) will first encounter a physical phenomenon and, only after that, perceive the information.
To this end, in 2010, Michael W. Busch created a general-purpose binary language,[17] later used in the Lone Signal project[18] to transmit crowdsourced messages to extraterrestrial intelligence.
As an example, the message sent by Frank Drake from the Arecibo Observatory in 1974 did not have any feature to support mechanisms to cope with the inevitable noise degradation of the interstellar medium.
The 1999 Cosmic Call transmission was far from being optimal (from a terrestrial viewpoint) as it was essentially a monochromatic signal spiced with supplementary information.
[31][32][33][34] Active SETI has primarily been criticized due to the perceived risk of revealing the location of the Earth to alien civilizations, without some process of prior international consultation.
However, some scientists consider these fears about the dangers of METI as panic and irrational superstition; Russian and Soviet radio engineer and astronomer Alexander L. Zaitsev has argued against these concerns.
[43][44] Zaitsev argues that we should consider the risks of not attempting to contact extraterrestrial civilizations, since the knowledge and wisdom an ETI could impart to us would save us from humanity's self-destructive tendencies.
[2] Astronomer Jill Tarter also disagrees with Hawking, arguing that aliens developed and long-lived enough to communicate and travel across interstellar distances would have evolved a cooperative and less violent intelligence.
[46] To lend a quantitative basis to discussions of the risks of transmitting deliberate messages from Earth, the SETI Permanent Study Group of the International Academy of Astronautics[47] adopted in 2007 a new analytical tool, the San Marino Scale.
[48] Developed by Prof. Ivan Almar and Prof. H. Paul Shuch, the San Marino Scale evaluates the significance of transmissions from Earth as a function of signal intensity and information content.
Its adoption suggests that not all such transmissions are created equal, thus each must be evaluated separately before establishing a blanket international policy regarding Active SETI.
[53] One proposal for a 10 billion watt interstellar SETI beacon was dismissed by Robert A. Freitas Jr. as being infeasible for a pre-Type I civilization, such as humanity, on the Kardashev scale.
Advances in consumer electronics have made possible transmitters that simultaneously transmit many narrow beams, covering the million or so nearest stars but not the spaces between.
Once civilizations have discovered each other's locations, the energy requirements for maintaining contact and exchanging information can be significantly reduced through the use of highly directional transmission technologies.
