Since active messaging to targeted extraterrestrial bodies is an ongoing practice, it is difficult to see how current scientific arguments have the ability to influence actions which have independent ...economic and institutional structures. The article analyzes what structures of argumentation might have an effect on on-going and future METI, as well as the type of theological reflection that would likely contribute to this discussion.
Microwave digital communication at interstellar distances is the foundation of extraterrestrial civilization (SETI and METI) communication of information-bearing signals. Large distances demand large ...transmitted power and/or large antennas, while the propagation is transparent over a wide bandwidth. Recognizing a fundamental tradeoff, reduced energy delivered to the receiver at the expense of wide bandwidth (the opposite of terrestrial objectives) is advantageous. Wide bandwidth also results in simpler design and implementation, allowing circumvention of dispersion and scattering arising in the interstellar medium and motion effects and obviating any related processing. The minimum energy delivered to the receiver per bit of information is determined by cosmic microwave background alone. By mapping a single bit onto a carrier burst, the Morse code invented for the telegraph in 1836 comes closer to this minimum energy than approaches used in modern terrestrial radio. Rather than the terrestrial approach of adding phases and amplitudes increases information capacity while minimizing bandwidth, adding multiple time–frequency locations for carrier bursts increases capacity while minimizing energy per information bit. The resulting location code is simple and yet can approach the minimum energy as bandwidth is expanded. It is consistent with easy discovery, since carrier bursts are energetic and straightforward modifications to post-detection pattern recognition can identify burst patterns. Time and frequency coherence constraints leading to simple signal discovery are addressed, and observations of the interstellar medium by transmitter and receiver constrain the burst parameters and limit the search scope.
•Fundamental limits on energy requirement for interstellar communication.•Low energy is more significant than small bandwidth.•Encoding information through time/frequency location is energy efficient.•Dispersion, scattering, and motion do not increase energy requirements.•Cosmic microwave background and scintillation are the limiting factors.
Because of the "big" in "Big History," its story of the one universe will have to expand if or when we incorporate the separate histories of extraterrestrial civilizations. communication exchange ...between terrestrials and extraterrestrials occurs, two things will likely happen: the scope of our Big History will become more comprehensive and, perhaps also, deeper in self-understanding. Objective knowledge of extraterrestrial history will expand our cosmic horizon while, at the same time, it may compel a subjective transformation of our place in the cosmic story. As the President of the International Big History Association, Lowell Gustafson, hints: Big History requires a galactic politics.
Stephen Hawking is right to oppose messaging other worlds, not because of the level of risk this would involve, but because the risks such a message would impose must be explicitly accepted by all of ...humanity.
Is it possible to mount a compelling ethical argument for METI? As we have argued elsewhere, conventional ethical theories are highly anthropocentric, making them difficult to apply to unknown alien ...intelligences, whose characteristics, needs, and concerns may differ radically from our own. In the absence of ethically relevant information about ETIs we contend that it isn't possible to provide a strong conventional ethical argument for METI. Drawing upon the ancient, less widely known, ethical-political tradition of cosmopolitanism, however, we show how proponents of METI could provide an ethical argument for trying to contact ETIs under the right procedural conditions.
In the search for habitable planets, the ultimate aspiration is finding an extraterrestrial technical civilization. We already lost a half of century for an active search for extraterrestrial ...civilizations. Should we lose another half? If all civilizations in the Universe are only recipients and not message-sending civilizations, then no SETI (Search for Extraterrestrial Intelligence) searches make any sense. Detecting only leaked radio signals is a hard job with present resources. Fear from the extraterrestrials is unfounded, having in mind physical difficulties and requirements of the interstellar travel. If possible extraterrestrial civilizations are more advanced than ours then they can pick up life signs from Earth easier than we can from their planets at present. Here we propose a scientifically based METI (Messaging to Extraterrestrial Intelligence) program.
The design of an end-to-end digital interstellar communication system at radio frequencies is discussed, drawing on the disciplines of digital communication engineering and computer network ...engineering in terrestrial and near-space applications. One goal is a roadmap to the design of such systems, aimed at future designers of either receivers (SETI) or transmitters (METI). In particular we emphasize the implications arising from the impossibility of coordination between transmitter and receiver prior to a receiver's search for a signal. A system architecture based on layering, as commonly used in network and software design, assists in organizing and categorizing the various design issues and identifying dependencies. Implications of impairments introduced in the interstellar medium, such as dispersion, scattering, Doppler, noise, and signal attenuation are discussed. Less fundamental (but nevertheless influential) design issues are the motivations of the transmitter designers and associated resource requirements at both transmitter and receiver. Unreliability is inevitably imposed by non-idealities in the physical communication channel, and this unreliability will have substantial implications for those seeking to convey interstellar messages.
► Digital communication engineering principles applied to interstellar communication. ► Consider the impact of non-coordination between transmitter and receiver designs. ► Employ modularity and propose three-layer architecture: signal, reliability and message. ► Separate discovery from communication, and propose discovery within signal layer. ► Discuss the implications of the inevitable unreliability seen by the message layer.
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