CETI is a branch of SETI research that focuses on composing and deciphering messages that could theoretically be understood by another technological civilization. The best known CETI experiment was the 1974 Arecibo message composed by Frank Drake and Carl Sagan.

CETI research has focused on three broad areas: mathematical languages, pictoral systems such as the Arecibo message, and algorithmic communication systems (ACETI).

Contents

1 History 2 Mathematical Languages 2.1 Astraglossa 2.2 LinCos (Lingua Cosmica) 2.3 A Language Based On The Fundamental Facts of Science 3 Pictoral Messages 3.1 Voyager Probes 3.2 The Arecibo Message 3.3 Cosmic Call Messages 4 Algorithmic Messages 4.1 Cosmic OS 4.2 Logic Gate Matrices 5 CETI Researchers 6 References

History

Humans have been attempting to communicate with other planets since they first speculated about the existence of inhabited worlds. (placeholder for additional content to be added)

Mathematical Languages

Astraglossa

Published in 1953 by Lancelot Hogben describes 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.

LinCos (Lingua Cosmica)

Lincos, published in 1960 by Hans Freudenthal, expands upon Astraglossa to create a general purpose language derived from basic math and logic symbols.

A Language Based On The Fundamental Facts of Science

Published in 1992 by Carl Devito and Richard Oehrle, is similar in syntax to Astraglossa and Lincos but builds its vocabulary around known physical properties.

Pictoral Messages

Pictoral communication systems seek to describe fundamental mathematical or physical concepts via simplified diagrams sent as bitmaps. These messages assume that the recipient has similar visual capabilities (weak assumption) and can understand basic math and geometry (strong assumption because both are prerequisites for building the optimal shape for a radio or optical telescope). A common critique of these systems is that they assume 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.

Voyager Probes

The Voyager probes, launched in 1977, carried two golden records that were inscribed with diagrams depicting the human form, our solar system and its location. Also included were recordings of pictures and sounds from Earth.

The Arecibo Message

The Arecibo message, transmitted in 1974, was a 1679 pixel image with 73 rows and 23 columns. It shows the numbers one through ten, the atomic numbers of hydrogen, carbon, nitrogen, oxygen, and phosphorous, the formulas for the sugars and bases in the nucleotides of DNA, the number of nucleotides in DNA, the double helix structure of DNA, a figure of a human being and its height, the population of Earth, our solar system, and an image of the Arecibo telescope with its diameter.

Cosmic Call Messages

The Cosmic Call message, composed by Stephane Dumas and Yvan Dutil and transmitted in 1999 and 2003, is a multi-page bitmap that builds a vocabulary of symbols representing numbers and mathematical operations. The message proceeds from basic math to progressively more complex concepts, including physical processes and objects (such as a hydrogen atom).

Algorithmic Messages

Algorithmic communication systems are a relatively field within CETI. In these systems, which build upon early work on mathematical languages, the sender describes a small set of math 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 pictoral and mathematical messages, 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.

Cosmic OS

Cosmic OS, designed by Paul Fitzpatrick at MIT, describes a virtual machine that is derived from lambda calculus.

Logic Gate Matrices

Logic Gate Matrices (aka LGM), developed by Brian McConnell, describes a universal virtual machine that is constructed by connecting coordinates in an n-dimensional space via math and logic operations, for example: (1,0,0) <-- (OR (0,0,1) (0,0,2)). Using this method, one can describe an arbitrarily complex computing substrate as well as the instructions to be executed on it.

CETI Researchers

Frank Drake (SETI Institute) : SETI pioneer, composed the Arecibo message with Carl Sagan

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 techique 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 2000-2002.

Marvin Minsky (MIT AI researcher) : first proposed the idea of including algorithms within an interstellar message.

Carl Sagan (deceased) : co-authored the Arecibo message, and was heavily involved in SETI throughout his life.

Douglas Vakoch (SETI Institute) : studies CETI and has published numerous articles, as well as an upcoming book from MIT Press about interstellar communication.

References

• Dutil, Dumas, Cosmic Call Message, http://www3.sympatico.ca/stephane_dumas/CETI/default.htm

• Martin, Martin C. 1991 SETI Puzzle, posted to sci.crypt, sci.astro, sci.space, rec.arts.sf-lovers and rec.puzzles. http://www.metahuman.org/martin/SETIPuzzle.html

• Communication with Alien Intelligence, 1985, Marvin Minsky, http://web.media.mit.edu/~minsky/papers/AlienIntelligence.html

• Devito, C. and Oerle, R. A Language Based on the Fundamental Facts of Science, Journal of the British Interplanetary Society, 1990, Vol 43, pp. 561-568

• Freudenthal H 1960 Lincos: Design of a Language for Cosmic Intercourse. North-Holland, Amsterdam.

• Hogben, Lancelot. Science in Authority. New York: W. W. Norton (1963)

• McConnell, Brian S. 2001 Beyond Contact: A Guide to SETI and Communicating with Alien Civilizations. O'Reilly, Cambridge, MA

• McConnell, Brian S. 2002 Algorithmic Communication with ETI & Mixed Media Message Composition

• McConnell, Brian S at al, 2005, Between Worlds, SETI Institute/MIT Press

• 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, MA: 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.