There are multiple independent organizations and individuals engaged in CETI research; the generic application of abbreviations CETI and SETI (search for extraterrestrial intelligence) in this article should not be taken as referring to any particular organization (such as the SETI Institute).
CETI research has focused on four broad areas: mathematical languages, pictorial systems such as the Arecibo message, algorithmic communication systems (ACETI), and computational approaches to detecting and deciphering "natural" language communication. There remain many undeciphered writing systems in human communication, such as Linear A, discovered by archeologists. Much of the research effort is directed at how to overcome similar problems of decipherment that arise in many scenarios of interplanetary communication.
In the 19th century, many books and articles speculated about the possible inhabitants of other planets. Many people believed that intelligent beings might live on the Moon, Mars, and/or Venus.[6]
Since travel to other planets was not possible at the time, some people suggested ways to signal extraterrestrials even before radio was discovered. Carl Friedrich Gauss is often credited with an 1820 proposal that a giant triangle and three squares, the Pythagoras, could be drawn on the Siberian tundra. The outlines of the shapes would have been ten-mile-wide strips of pine forest, whereas the interiors could be filled with rye or wheat.[7]
Illustration of the Pythagorean theorem, that was proposed to be a signal for extraterrestrials. The sum of two squares whose sides are the two legs (blue and red) is equal to the area of the square whose side is the hypotenuse (purple).
Joseph Johann Littrow proposed in 1819 to use the Sahara as a sort of blackboard. Giant trenches several hundred yards wide could delineate twenty-mile-wide shapes. Then the trenches would be filled with water, and then enough kerosene could be poured on top of the water to burn for six hours. Using this method, a different signal could be sent every night.[8]
Meanwhile, other astronomers were looking for signs of life on other planets. In 1822, Franz von Paula Gruithuisen thought he saw a giant city and evidence of agriculture on the Moon, but astronomers using more powerful instruments refuted his claims. Gruithuisen also believed he saw evidence of life on Venus. Ashen light had previously been observed on the dark side of Venus, and he postulated that it was caused by a great fire festival put on by the inhabitants to celebrate their new emperor. Later he revised his position, stating that the Venusians could be burning their rainforest to make more farmland.[9]
By the late 1800s, the possibility of life on the Moon was put to rest. Astronomers at that time believed in the Kant-Laplace hypothesis, which stated that the farthest planets from the sun are the oldest–therefore Mars was more likely to have advanced civilizations than Venus.[10] Subsequent investigations focused on contacting Martians. In 1877, Giovanni Schiaparelli announced he had discovered "canali" ("channels" in Italian, which occur naturally, and mistranslated as "canals", which are artificial) on Mars. This was followed by thirty years of enthusiasm about the possibility of life on Mars.[11] Eventually the Martian canals proved illusory.
The inventor Charles Cros was convinced that pinpoints of light observed on Mars and Venus were the lights of large cities. He spent years of his life trying to get funding for a giant mirror with which to signal the Martians. The mirror would be focused on the Martian desert, where the intense reflected sunlight could be used to burn figures into the Martian sand.[12]
Inventor Nikola Tesla mentioned many times during his career that he thought his inventions such as his Tesla coil, used in the role of a "resonant receiver", could be used to communicate with other planets,[13][14] and that he even had observed repetitive signals of what he believed were extraterrestrial radio communications coming from Venus or Mars in 1899. These "signals" turned out to be terrestrial radiation, however.
Around 1900, the Guzman Prize was created; the first person to establish interplanetary communication would be awarded 100,000 francs, under one stipulation: Mars was excluded because Madame Guzman thought communicating with Mars would be too easy to deserve a prize.[15]
Published in 1960 by Hans Freudenthal, Lincos: Design of a Language for Cosmic Intercourse, expands upon Astraglossa to create a general-purpose language derived from basic mathematics and logic symbols.[16] Several researchers have expanded further upon Freudenthal's work. A dictionary resembling Lincos was featured in the Carl Sagan novel Contact and its film adaptation.
Astraglossa
Published in 1963 by Lancelot Hogben, "Astraglossa" is an essay describing a system for combining numbers and operators in a series of short and long pulses. In Hogben's system, short pulses represent numbers, while trains of long pulses represent symbols for addition, subtraction, etc.[17]
Carl Sagan
In the 1985 science fiction novel Contact, Carl Sagan explored in some depth how a message might be constructed to allow communication with an alien civilization, using prime numbers as a starting point, followed by various universal principles and facts of mathematics and science.
Sagan also edited a nonfiction book on the subject.[18] An updated collection of articles on the same topic was published in 2011.[19]
A language based on the fundamental facts of science
Published in 1992 by Carl Devito and Richard Oehrle, A language based on the fundamental facts of science is a paper describing a language similar in syntax to Astraglossa and Lincos, but which builds its vocabulary around known physical properties.[20]
Busch general-purpose binary language used in Lone Signal transmissions
In 2010, Michael W. Busch created a general-purpose binary language [21] later used in the Lone Signal project[22] to transmit crowdsourced messages to extraterrestrial intelligence (METI). This was followed by an attempt to extend the syntax used in the Lone Signal hailing message to communicate in a way that, while neither mathematical nor strictly logical, was nonetheless understandable given the prior definition of terms and concepts in the Lone Signal hailing message.[23]
Example of a high-resolution pictorial message to potential eti at Proxima Centauri
Pictorial communication systems seek to describe fundamental mathematical or physical concepts via simplified diagrams sent as bitmaps. These messages necessarily assume that the recipient has similar visual capabilities and can understand basic mathematics and geometry. A common critique of pictorial systems is that they presume a shared understanding of special shapes, which may not be the case with a species with substantially different vision, and therefore a different way of interpreting visual information. For instance, an arrow representing the movement of some object might be misinterpreted as a weapon firing.
Pioneer probes
Two etched plaques, known as the Pioneer plaques, were included aboard the Pioneer 10 and Pioneer 11 spacecraft when they launched in 1972 and 1973. The plaques depict the specific location of the Solar System within the galaxy and the Earth within the Solar System, as well as the form of the human body.
Voyager probes
Launched in 1977, the Voyager probes carried two golden records that were inscribed with diagrams similar to the Pioneer plaques, depicting the human form, the Solar System, and its location. Also included were recordings of images and sounds from Earth.
Arecibo message
The Arecibo message, transmitted in 1974, was a 1,679-pixel bitmap that, when properly arranged into 73 rows and 23 columns, shows the numbers one through ten; the atomic numbers of hydrogen, carbon, nitrogen, oxygen, and phosphorus; the formulas for the sugars and bases that make up the nucleotides of DNA; the number of nucleotides in the human genome; the double helix structure of DNA; a simple illustration of a human being and its height; the human population of Earth; a diagram of the Solar System; and an illustration of the Arecibo telescope with its diameter.
Cosmic Call messages
The Cosmic Call messages consisted of a few digital sections – "Rosetta Stone", a copy of the Arecibo Message, the Bilingual Image Glossary, and the Braastad message – as well as text, audio, video, and other image files submitted for transmission by people around the world. The "Rosetta Stone" was composed by Stéphane Dumas and Yvan Dutil, and represents a multi-page bitmap that builds a vocabulary of symbols representing numbers and mathematical operations. The message proceeds from basic mathematics to progressively more complex concepts, including physical processes and objects (such as a hydrogen atom). The message was designed with a noise-resistant format and characters that make it resistant to alteration by noise. These messages were transmitted in 1999 and 2003 from Evpatoria Planetary Radar in Russia under the scientific guidance of Alexander L. Zaitsev. Richard Braastad coordinated the overall project.
Star systems to which the messages were sent include the following:[24]
The Teen-Age Message, composed by Russian scientists (Zaitsev, Gindilis, Pshenichner, Filippova) and teens, was transmitted from the 70-m dish of Evpatoria Deep Space Center in Ukraine to six star systems resembling that of the Sun on August 29 and September 3 and 4, 2001. The message consists of three parts:
Section 1 represents a coherent-sounding radio signal with slow Doppler wavelength tuning to imitate transmission from the Sun's center. This signal was transmitted in order to help extraterrestrials detect the TAM and diagnose the radio propagation effect of the interstellar medium.
Section 2 is analog information representing musical melodies performed on the theremin. This electric musical instrument produces a quasi-monochromatic signal, which is easily detectable across interstellar distances. There were seven musical compositions in the First Theremin Concert for Aliens. The 14-minute analog transmission of the theremin concert would take almost 50 hours by digital means; see The First Musical Interstellar Radio Message.
Section 3 represents a well-known Arecibo-like binary digital information: the logotype of the TAM, bilingual Russian and English greeting to aliens, and image glossary.
Star systems to which the message was sent are the following:[24]
The Cosmic Call-2 message contained text, images, video, music, the Dutil/Dumas message, a copy of the 1974 Arecibo message, BIG = Bilingual Image Glossary, the AI program Ella, and the Braastad message.
Algorithmic messages
Algorithmic communication systems are a relatively new field within CETI. In these systems, which build upon early work on mathematical languages, the sender describes a small set of mathematic and logic symbols that form the basis for a rudimentary programming language that the recipient can run on a virtual machine. Algorithmic communication has a number of advantages over static pictorial and mathematical messages,[citation needed] including: localized communication (the recipient can probe and interact with the programs within a message, without transmitting a reply to the sender and then waiting years for a response), forward error correction (the message might contain algorithms that process data elsewhere in the message), and the ability to embed proxy agents within the message. In principle, a sophisticated program when run on a fast enough computing substrate, may exhibit complex behavior and perhaps, intelligence.
Logic Gate Matrices (a.k.a. LGM), developed by Brian McConnell, describes a universal virtual machine that is constructed by connecting coordinates in an n-dimensional space via mathematics and logic operations, for example: (1,0,0) <-- (OR (0,0,1) (0,0,2)). Using this method, one may describe an arbitrarily complex computing substrate as well as the instructions to be executed on it.[clarification needed]
Natural language messages
This research focuses on the event that we receive a signal or message that is either not directed at us (eavesdropping) or one that is in its natural communicative form. To tackle this difficult, but probable scenario, methods are being developed that will detect if a signal has structure indicative of an intelligent source, categorize the type of structure detected, and then decipher its content, from its physical level encoding and patterns to the parts-of-speech that encode internal and external ontologies.[25][26]
Primarily, this structure modeling focuses on the search for generic human and inter-species language universals to devise computational methods by which language may be discriminated from non-language, and core structural syntactic elements of unknown languages may be detected.[27] Aims of this research include contributing to the understanding of language structure and the detection of intelligent language-like features in signals, in order to aid the search for extraterrestrial intelligence.[28][29]
A plot of the rank versus frequency for the first 10 million words in 30 Wikipedias (dumps from October 2015) in a log-log scale
The problem goal is therefore to separate language from non-language without dialogue, and learn something about the structure of language in the passing. The language may not be human (animals, aliens, computers, etc.), the perceptual space may be unknown, and human language structure cannot be presumed, but must begin somewhere. The language signal should be approached from a naive viewpoint, increasing ignorance and assuming as little as possible.[30][31]
If a sequence can be tokenized, that is, separated into "words", an unknown human language may be distinguished from many other data sequences by the frequency distribution of the tokens. Human languages conform to a Zipfian distribution, while many (but not all) other data sequences do not. It has been proposed that an alien language also might conform to such a distribution.[30] When displayed in a log-log graph of frequency vs. rank, this distribution would appear as a somewhat straight line with a slope of approximately -1. SETI scientist Laurance Doyle explains that the slope of a line that represents individual tokens in a stream of tokens may indicate whether the stream contains linguistic or other structured content. If the line angles at 45°, the stream contains such content. If the line is flat, it does not.[32][33]
Dr John Elliott: research into developing strategies, which are based on receiving a 'natural' language message, that look at developing algorithms to detect if an ET signal has intelligent-like structure and if so, then how to decipher its content. Author of many papers in this area and a contributor to SETI's book on interstellar communication. Other contributions include message design and construction; member of: International Academy of Astronautics, SETI Permanent Study Group; International Task Group for the Post-detection identification of unknown radio signals.[25][26][27][28][29][30][31]
Laurence Doyle (SETI Institute): studies animal communication, and has developed statistical measures of complexity in animal utterances as well as human language.
Stephane Dumas: developed Cosmic Call messages, as well as a general technique for generating 2-D symbols that remain recognizable even if corrupted by noise.
Yvan Dutil: developed Cosmic Call messages with Stephane Dumas.
Paul Fitzpatrick (MIT): developed CosmicOS system based on lambda calculus
Brian McConnell: developed framework for algorithmic communication systems (ACETI) from 2000 to 2002.
Marvin Minsky (MITAI researcher): Believes that aliens may think similarly to humans because of shared constraints, permitting communication.[34] First proposed the idea of including algorithms within an interstellar message.
Carl Sagan: co-authored the Arecibo message and was heavily involved in SETI throughout his life.
Michael W. Busch: (Lone Signal) created the binary encoding system for the ongoing Lone Signal hailing message.
Jacob Haqq Misra: (Lone Signal) is the chief science officer for the ongoing Lone Signal active SETI project.
Interspecies communication
Some researchers have concluded that in order to communicate with extraterrestrial species, humanity must first try to communicate with Earth's intelligent animal species. John C. Lilly worked with interspecies communication by teaching dolphins English (successful with rhythms, not with understandability, given their different mouth/blowhole shapes). He practiced various disciplines of spirituality and also ingested psychedelic drugs such as LSD and (later) ketamine in the company of dolphins.[39] He tried to determine whether he could communicate non-verbally with dolphins, and also tried to determine if some extraterrestrial radio signals are intelligent communications. Similarly, Laurance Doyle,[40][41][42]Robert Freitas[citation needed] and Brenda McCowan[40][41] compare the complexity of cetacean and human languages to help determine whether a specific signal from space is complex enough to represent a message that needs to be decoded.
The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way Galaxy.
The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high likelihood of its existence. Those affirming the paradox generally conclude that if the conditions required for life to arise from non-living matter are as permissive as the available evidence on Earth indicates, then extraterrestrial life would be sufficiently common such that it would be implausible for it not to have been detected yet.
Lincos is a constructed language first described in 1960 by Dr. Hans Freudenthal in his book Lincos: Design of a Language for Cosmic Intercourse, Part 1. It is a language designed to be understandable by any possible intelligent extraterrestrial life form, for use in interstellar radio transmissions. Freudenthal considered that such a language should be easily understood by beings not acquainted with any Earthling syntax or language. Lincos was designed to be capable of encapsulating "the whole bulk of our knowledge".
The search for extraterrestrial intelligence (SETI) is a collective term for scientific searches for intelligent extraterrestrial life. Methods include monitoring electromagnetic radiation for signs of transmissions from civilizations on other planets, optical observation, and the search for physical artifacts. Attempts to message extraterrestrial intelligences have also been made.
Frank Donald Drake was an American astrophysicist and astrobiologist.
Extraterrestrial intelligence (ETI) refers to hypothetical intelligent extraterrestrial life. No such life has ever been verifiably observed to exist. The question of whether other inhabited worlds might exist has been debated since ancient times. The modern form of the concept emerged when the Copernican Revolution demonstrated that the Earth was a planet revolving around the Sun, and other planets were, conversely, other worlds. The question of whether other inhabited planets or moons exist was a natural consequence of this new understanding. It has become one of the most speculative questions in science and is a central theme of science fiction and popular culture.
The Arecibo message is an interstellar radio message carrying basic information about humanity and Earth that was sent to the globular cluster Messier 13 in 1974. It was meant as a demonstration of human technological achievement, rather than a real attempt to enter into a conversation with extraterrestrials.
The Teen Age Message (TAM) was a series of interstellar radio transmissions sent from the Yevpatoria Planetary Radar to six solar-type stars during August–September 2001. The structure of the TAM was suggested by Alexander Zaitsev, Chief Scientist at Russia's Institute of Radio-engineering and Electronics. The message's content and target stars were selected by a group of teens from four Russian cities, who collaborated in person and via the Internet. Each transmission comprised three sections: a sounding, a live theremin concert, and digital data including images and text. TAM was humanity's fourth Active SETI broadcast and the first musical interstellar radio message.
Aleksandr Leonidovich Zaitsev was a Russian and Soviet radio engineer and astronomer from Fryazino. He worked on radar astronomy devices, near-Earth asteroid radar research, and SETI.
Astrolinguistics is a field of linguistics connected with the search for extraterrestrial intelligence (SETI).
Active SETI is the attempt to send messages to intelligent extraterrestrial life. Active SETI messages are predominantly sent in the form of radio signals. Physical messages like that of the Pioneer plaque may also be considered an active SETI message. Active SETI is also known as METI.
Cosmic Call was the name of two sets of interstellar radio messages that were sent from RT-70 in Yevpatoria, Ukraine in 1999 and 2003 to various nearby stars. The messages were designed with noise-resistant format and characters.
The cultural impact of extraterrestrial contact is the corpus of changes to terrestrial science, technology, religion, politics, and ecosystems resulting from contact with an extraterrestrial civilization. This concept is closely related to the search for extraterrestrial intelligence (SETI), which attempts to locate intelligent life as opposed to analyzing the implications of contact with that life.
Lone Signal was a crowdfunded active SETI project designed to send interstellar messages from Earth to a possible extraterrestrial civilization. Founded by businessman Pierre Fabre and supported by several entrepreneurs, Lone Signal was based at the Jamesburg Earth Station in Carmel, California.
A Simple Response to an Elemental Message (ASREM) was an Interstellar Radio Message (IRM) consisting primarily of 3775 worldwide responses to this initiative's posed question; "How will our present, environmental interactions shape the future?" This transmission also features a smaller 'Honorary Mention' text archive and a series of images of Earth.
METI International, known simply as METI, is a non-profit research organization founded in July 2015 by Douglas Vakoch that creates and transmits interstellar messages to attempt to communicate with extraterrestrial civilizations. It is based in San Francisco, California.
Douglas A. Vakoch is an American astrobiologist, search for extraterrestrial intelligence (SETI) researcher, psychologist, and president of METI International, a nonprofit research and educational organization devoted to transmitting intentional signals to extraterrestrial civilizations. Vakoch led METI's participation in Sónar Calling GJ 273b, which transmitted a series of interstellar messages to Luyten's Star, located 12.4 light years from Earth. Vakoch advocates ongoing transmission projects, arguing that this does not increase risks of an alien invasion as suggested by British cosmologist Stephen Hawking. He has participated in several SETI observation programs, and after sixteen years at the SETI Institute, where he was director of Interstellar Message Composition, Vakoch founded METI International. He has edited over two dozen books in SETI, astrobiology, the psychology of space exploration, ecocriticism, COVID, and transgender studies. Vakoch helped design the message included on NASA's Europa Clipper spacecraft. He is general editor of three book series in ecocriticism and in the intersection of space and society. Vakoch has appeared widely on television and radio as a commentator on SETI and astrobiology. He is an emeritus professor of clinical psychology at the California Institute of Integral Studies (CIIS).
Archaeology, Anthropology, and Interstellar Communication is a 2014 collection of essays edited by Douglas Vakoch and published by NASA. The book is focused on the role that the humanities and social sciences, in particular anthropology and archaeology, play in the search for extraterrestrial intelligence (SETI). The seventeen essays are gathered into four sections, which respectively explore the history of SETI as a field; archaeological comparisons for human-alien communication, such as the difficulties of translating ancient languages; the inferential gap between humans and aliens, and the consequences this would have for communication and trade; and the potential nature of alien intelligences.
The following outline is provided as an overview of and topical guide to extraterrestrial life:
↑ Garelik, Glenn; Nash, J. Madeleine; Woodbury, Richard (July 18, 1988). "Space: Onward to Mars". Time. Vol.132, no.3. p.50. Archived from the original on August 28, 2008.
↑ Ley, Willy (1958). Rockets, Missiles, and Space Travel. The Viking Press.
↑ Freudenthal H, ed. (1960). Lincos: Design of a Language for Cosmic Intercourse. Studies in Logic and the Foundations of Mathematics (Book 28). North-Holland, Amsterdam. ISBN978-0-444-53393-7.
↑ Devito, C. & Oerle, R (1990). "A Language Based on the Fundamental Facts of Science". Journal of the British Interplanetary Society. 43 (12): 561–568. PMID11540499.
1 2 Elliott, J; Atwell, E. (2000). "Is anybody out there: the detection of intelligent and generic language-like features". Journal of the British Interplanetary Society. 53: 13–22. Bibcode:2000JBIS...53...13E. ISSN0007-084X.
1 2 Elliott, J. (2002a). "Detecting languageness". Proceedings of 6th World Multi-Conference on Systemics, Cybernetics and Informatics (SCI 2002). IX: 323–328.
1 2 Elliott, John (2002b). "The filtration of inter-galactic objets trouvés and the identification of the Lingua ex Machina hierarchy". Proceedings of World Space Congress: The 53rd International Astronautical Congress. 68 (3–4): IAA–02–IAA.9.2.10. doi:10.1016/j.actaastro.2009.08.012.
Ley, Willy. Rockets, Missiles, and Space Travel (revised). New York: The Viking Press (1958) ISBN978-1568493022
McConnell, Brian S. 2001 Beyond Contact: A Guide to SETI and Communicating with Alien Civilizations. O'Reilly, Cambridge, Massachusetts ISBN978-0596000370
McConnell, Brian S. 2002 Algorithmic Communication with ETI & Mixed Media Message Composition
Minsky, Marvin, talk given at Communication With Extraterrestrial Intelligence (CETI), Proceedings of a conference held at the Byurakan Astrophysical Observatory, Yerevan, USSR, 5–11 September 1971. Edited by Carl Sagan. Cambridge, Massachusetts: The Massachusetts Institute of Technology, 1973. p. ix
Morrison, P. "Interstellar Communication", Bulletin of the Philosophical Society of Washington, 16, 78 (1962). Reprinted in A. G. W. Cameron, ed., Interstellar Communication.
Oberhaus, D. (2019) Extraterrestrial Languages. MIT Press.
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