SETI

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Encyclopedia
The search for extraterrestrial intelligence (SETI) is the collective name for a number of activities people undertake to search for intelligent extraterrestrial life
Extraterrestrial life
Extraterrestrial life is defined as life that does not originate from Earth...

. Some of the most well known projects are run by the SETI Institute
SETI Institute
The SETI Institute is a not-for-profit organization whose mission is to “explore, understand and explain the origin, nature and prevalence of life in the universe”. SETI stands for the "search for extraterrestrial intelligence". One program is the use of both radio and optical telescopes to search...

. SETI projects use scientific method
Scientific method
Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...

s to search for intelligent life on other planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...

s. For example, electromagnetic radiation
Electromagnetic radiation
Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...

 is monitored for signs of transmissions
Interstellar communication
Interstellar communication is the transmission of signals between planetary systems. Sending Interstellar messages is potentially much easier than interstellar travel, being possible with technologies and equipment which are currently available...

 from civilization
Civilization
Civilization is a sometimes controversial term that has been used in several related ways. Primarily, the term has been used to refer to the material and instrumental side of human cultures that are complex in terms of technology, science, and division of labor. Such civilizations are generally...

s on other worlds. The United States government
Federal government of the United States
The federal government of the United States is the national government of the constitutional republic of fifty states that is the United States of America. The federal government comprises three distinct branches of government: a legislative, an executive and a judiciary. These branches and...

 contributed to early SETI projects, but recent work has been primarily funded by private sources.

There are great challenges in searching across the cosmos
Cosmos
In the general sense, a cosmos is an orderly or harmonious system. It originates from the Greek term κόσμος , meaning "order" or "ornament" and is antithetical to the concept of chaos. Today, the word is generally used as a synonym of the word Universe . The word cosmos originates from the same root...

 for a first transmission that could be characterized as intelligent, since its direction, spectrum and method of communication are all unknown beforehand. SETI projects necessarily make assumptions to narrow the search, the foremost being that electromagnetic radiation
Electromagnetic radiation
Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...

 would be a medium of communication for advanced extraterrestrial life.

Radio experiments



Many radio frequencies penetrate our atmosphere quite well, and this led to radio telescope
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...

s that investigate the cosmos using large radio antennas. Furthermore, the Earth emits considerable electromagnetic radiation as a byproduct of communications such as television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...

 and radio. These signals would be easy to recognize as artificial due to their repetitive nature and narrow bandwidths. If this is typical, one way of discovering an extraterrestrial civilization might be to detect non-natural radio emissions from a location outside our Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

.

Early work


As early as 1896, Nikola Tesla
Nikola Tesla
Nikola Tesla was a Serbian-American inventor, mechanical engineer, and electrical engineer...

 suggested that radio could be used to contact extraterrestrial life. In 1899 while investigating atmospheric electricity
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

 using a Tesla coil
Tesla coil
A Tesla coil is a type of resonant transformer circuit invented by Nikola Tesla around 1891. It is used to produce high voltage, low current, high frequency alternating current electricity. Tesla coils produce higher current than the other source of high voltage discharges, electrostatic machines...

 receiver in his Knob Hill
Knob Hill
Knob Hill is a neighborhood in central Colorado Springs, Colorado, one mile east of downtown, extending east from South Union Blvd to South Circle Drive, and from East Willamette Ave south to Airport Rd...

 lab, Tesla observed repetitive signals, substantially different from the signals noted from storms and Earth noise, that he interpreted as being of extraterrestrial origin. He later recalled the signals appeared in groups of one, two, three, and four clicks together. Tesla thought the signals were coming from Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

. Analysis of Tesla's research has ranged from suggestions that Tesla detected nothing, he simply was misunderstanding the new technology he was working with, to claims that Tesla may have been observing naturally occurring Jovian
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

 plasma torus
Jupiter's magnetosphere
The magnetosphere of Jupiter is the cavity created in the solar wind by the planet's magnetic field. Extending up to seven million kilometers in the Sun's direction and almost to the orbit of Saturn in the opposite direction, Jupiter's magnetosphere is the largest and most powerful of any planetary...

 signals. In the early 1900s, Guglielmo Marconi
Guglielmo Marconi
Guglielmo Marconi was an Italian inventor, known as the father of long distance radio transmission and for his development of Marconi's law and a radio telegraph system. Marconi is often credited as the inventor of radio, and indeed he shared the 1909 Nobel Prize in Physics with Karl Ferdinand...

, Lord Kelvin
William Thomson, 1st Baron Kelvin
William Thomson, 1st Baron Kelvin OM, GCVO, PC, PRS, PRSE, was a mathematical physicist and engineer. At the University of Glasgow he did important work in the mathematical analysis of electricity and formulation of the first and second laws of thermodynamics, and did much to unify the emerging...

, and David Peck Todd
David Peck Todd
David Peck Todd was a noted American astronomer. He produced a complete set of photographs of the 1882 transit of Venus.-Biography:...

 also stated their belief that radio could be used to contact Martian
Martian
As an adjective, the term martian is used to describe anything pertaining to the planet Mars.However, a Martian is more usually a hypothetical or fictional native inhabitant of the planet Mars. Historically, life on Mars has often been hypothesized, although there is currently no solid evidence of...

s, with Marconi stating that his stations had also picked up potential Martian signals.

On August 21–23, 1924, Mars entered an opposition closer to Earth than any time in a century before or since. In the United States, a "National Radio Silence Day" was promoted during a 36-hour period from the 21–23, with all radios quiet for five minutes on the hour, every hour. At the United States Naval Observatory
United States Naval Observatory
The United States Naval Observatory is one of the oldest scientific agencies in the United States, with a primary mission to produce Positioning, Navigation, and Timing for the U.S. Navy and the U.S. Department of Defense...

, a radio receiver was lifted 3 kilometers above the ground in a dirigible tuned to a wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...

 between 8 and 9 kilometers, using a "radio-camera" developed by Amherst College
Amherst College
Amherst College is a private liberal arts college located in Amherst, Massachusetts, United States. Amherst is an exclusively undergraduate four-year institution and enrolled 1,744 students in the fall of 2009...

 and Charles Francis Jenkins
Charles Francis Jenkins
Charles Francis Jenkins was an American pioneer of early cinema and one of the inventors of television, though he used mechanical rather than electronic technologies...

. The program was led by David Peck Todd with the military assistance of Admiral Edward W. Eberle (Chief of Naval Operations
Chief of Naval Operations
The Chief of Naval Operations is a statutory office held by a four-star admiral in the United States Navy, and is the most senior uniformed officer assigned to serve in the Department of the Navy. The office is a military adviser and deputy to the Secretary of the Navy...

), with William F. Friedman
William F. Friedman
William Frederick Friedman was a US Army cryptographer who ran the research division of the Army's Signals Intelligence Service in the 1930s, and parts of its follow-on services into the 1950s...

 (chief cryptographer
Cryptography
Cryptography is the practice and study of techniques for secure communication in the presence of third parties...

 of the US Army), assigned to translate any potential Martian messages.

A 1959 paper by Philip Morrison
Philip Morrison
Philip Morrison, was Institute Professor Emeritus and Professor of Physics Emeritus at the Massachusetts Institute of Technology .-Early life and education:...

 and Giuseppe Cocconi
Giuseppe Cocconi
Giuseppe Cocconi was a former director of the Proton Synchrotron at CERN in Geneva. He is known for is work in particle physics and for his involvement with SETI.-Life:...

 first pointed out the possibility of searching the microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...

 spectrum, and proposed frequencies and a set of initial targets.

In 1960, Cornell University
Cornell University
Cornell University is an Ivy League university located in Ithaca, New York, United States. It is a private land-grant university, receiving annual funding from the State of New York for certain educational missions...

 astronomer Frank Drake
Frank Drake
Frank Donald Drake PhD is an American astronomer and astrophysicist. He is most notable as one of the pioneers in the search for extraterrestrial intelligence, including the founding of SETI, mounting the first observational attempts at detecting extraterrestrial communications in 1961 in Project...

 performed the first modern SETI experiment, named "Project Ozma
Project Ozma
Project Ozma was a pioneering SETI experiment started in 1960 by Cornell University astronomer Frank Drake, at the National Radio Astronomy Observatory at Green Bank, West Virginia. The object of the experiment was to search for signs of life in distant solar systems through interstellar radio waves...

", after the Queen of Oz
Princess Ozma
Princess Ozma is a fictional character in the Land of Oz, created by L. Frank Baum. She appears in every book of the series except the first, The Wonderful Wizard of Oz .She is the rightful ruler of Oz, and L...

 in L. Frank Baum
L. Frank Baum
Lyman Frank Baum was an American author of children's books, best known for writing The Wonderful Wizard of Oz...

's fantasy books. Drake used a radio telescope
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...

 26 meters in diameter at Green Bank, West Virginia
Green Bank, West Virginia
Green Bank is a census-designated place in Pocahontas County in West Virginia's Potomac Highlands inside the Allegheny Mountain Range. Green Bank is located along WV 28. Green Bank is also close to the Snowshoe Mountain ski resort...

, to examine the stars Tau Ceti
Tau Ceti
Tau Ceti is a star in the constellation Cetus that is spectrally similar to the Sun, although it has only about 78% of the Sun's mass. At a distance of just under 12 light-years from the Solar System, it is a relatively close star. Tau Ceti is metal-deficient and so is thought to be less likely to...

 and Epsilon Eridani
Epsilon Eridani
Epsilon Eridani is a star in the southern constellation Eridanus, along a declination 9.46° south of the celestial equator. This allows the star to be viewed from most of the Earth's surface. At a distance of 10.5 light years , it has an apparent magnitude of 3.73...

 near the 1.420 gigahertz marker frequency, a region of the radio spectrum dubbed the "water hole
Waterhole (radio)
The waterhole, or water hole, refers to an especially quiet band of the electromagnetic spectrum between 1,420 and 1,666 megahertz, corresponding to wavelengths of 21 and 18 centimeters respectively. The term was coined by Bernard Oliver. The strongest hydroxyl radical spectral line radiates at 18...

" due to its proximity to the hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 and hydroxyl radical
Hydroxyl radical
The hydroxyl radical, •OH, is the neutral form of the hydroxide ion . Hydroxyl radicals are highly reactive and consequently short-lived; however, they form an important part of radical chemistry. Most notably hydroxyl radicals are produced from the decomposition of hydroperoxides or, in...

 spectral lines. A 400 kilohertz band was scanned around the marker frequency, using a single-channel receiver with a bandwidth of 100 hertz. The information was stored on tape for off-line analysis. He found nothing of great interest, but has continued a pro-active involvement in the search for life beyond Earth for 50 years.

The first SETI conference took place at Green Bank, West Virginia in 1961.

The Soviet scientists took a strong interest in SETI during the 1960s and performed a number of searches with omnidirectional antenna
Omnidirectional antenna
In radio communication, an omnidirectional antenna is an antenna which radiates radio wave power uniformly in all directions in one plane, with the radiated power decreasing with elevation angle above or below the plane, dropping to zero on the antenna's axis. This radiation pattern is often...

s in the hope of picking up powerful radio signals. Soviet astronomer Iosif Shklovskii wrote the pioneering book in the field Universe, Life, Intelligence (1962), which was expanded upon by American astronomer Carl Sagan
Carl Sagan
Carl Edward Sagan was an American astronomer, astrophysicist, cosmologist, author, science popularizer and science communicator in astronomy and natural sciences. He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books...

 as the best-selling Intelligent Life in the Universe (1966).

The first Kraus-style radio telescope
Kraus-type
The Kraus-type radio telescope design was created by Dr. John D. Kraus .Kraus-type telescopes are transit instruments, where the flat primary reflects radio light towards the spherical secondary, which focuses it towards a mobile focal carriage...

 was powered up in 1963. It was 360 feet (109.7 m) wide, 500 feet (152.4 m) long, and 70 feet (21.3 m) high. In the March 1955 issue of Scientific American
Scientific American
Scientific American is a popular science magazine. It is notable for its long history of presenting science monthly to an educated but not necessarily scientific public, through its careful attention to the clarity of its text as well as the quality of its specially commissioned color graphics...

, John D. Kraus
John D. Kraus
John Daniel Kraus was an American physicist known for his contributions to electromagnetics, radio astronomy, and antenna theory. His inventions included the helical antenna, the corner reflector, and several other types of antennas...

 described a concept to scan the cosmos
Cosmos
In the general sense, a cosmos is an orderly or harmonious system. It originates from the Greek term κόσμος , meaning "order" or "ornament" and is antithetical to the concept of chaos. Today, the word is generally used as a synonym of the word Universe . The word cosmos originates from the same root...

 for natural radio signals using a flat-plane radio telescope
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...

 equipped with a parabolic reflector
Reflector (antenna)
An antenna reflector is a device that reflects electromagnetic waves.It is often a part of an antenna assembly.The most common reflector types are...

. Within two years, his concept was approved for construction by Ohio State University
Ohio State University
The Ohio State University, commonly referred to as Ohio State, is a public research university located in Columbus, Ohio. It was originally founded in 1870 as a land-grant university and is currently the third largest university campus in the United States...

. With $71,000 total in grants from the National Science Foundation
National Science Foundation
The National Science Foundation is a United States government agency that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National Institutes of Health...

, construction began on a 20-acre
Acre
The acre is a unit of area in a number of different systems, including the imperial and U.S. customary systems. The most commonly used acres today are the international acre and, in the United States, the survey acre. The most common use of the acre is to measure tracts of land.The acre is related...

 plot in Delaware, Ohio
Delaware, Ohio
The City of Delaware is a city in and the county seat of Delaware County in the United States state of Ohio. Delaware was founded in 1808 and was incorporated in 1816. It is located near the center of Ohio, is about north of Columbus, and is part of the Columbus, Ohio Metropolitan Area...

. This Ohio State University radio telescope
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...

 was called Big Ear. Later, it began the world's first continuous SETI program, called the Ohio State University SETI program.
In 1971, NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 funded a SETI study that involved Drake, Bernard Oliver of Hewlett-Packard
Hewlett-Packard
Hewlett-Packard Company or HP is an American multinational information technology corporation headquartered in Palo Alto, California, USA that provides products, technologies, softwares, solutions and services to consumers, small- and medium-sized businesses and large enterprises, including...

 Corporation, and others. The resulting report proposed the construction of an Earth-based radio telescope array with 1,500 dishes known as "Project Cyclops
Project Cyclops
Project Cyclops was a 1971 NASA project that investigated how SETI should be conducted. As a NASA product the report is in the public domain. The project team created a design for coordinating large numbers of radio telescopes to search for Earth-like radio signals at a distance of up to 1000...

". The price tag for the Cyclops array was $10 billion USD. Cyclops was not built, but the report formed the basis of much SETI work that followed.

In 1974, a largely symbolic attempt was made at the Arecibo Observatory
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...

 to send a message
Arecibo message
The Arecibo message was broadcast into space a single time via frequency modulated radio waves at a ceremony to mark the remodeling of the Arecibo radio telescope on 16 November 1974. It was aimed at the globular star cluster M13 some 25,000 light years away because M13 was a large and close...

 to other worlds. It was sent towards the globular star cluster M13, which is 25,000 light years from Earth.

The OSU SETI program gained fame on August 15, 1977 when Jerry Ehman, a project volunteer, witnessed a startlingly strong signal received by the telescope. He quickly circled the indication on a printout and scribbled the phrase “Wow!” in the margin. This signal, dubbed the Wow! signal
Wow! signal
The Wow! signal was a strong narrowband radio signal detected by Dr. Jerry R. Ehman on August 15, 1977, while working on a SETI project at the Big Ear radio telescope of The Ohio State University then located at Ohio Wesleyan University's Perkins Observatory, Delaware, Ohio. The signal bore...

, is considered by some to be the most likely candidate from an artificial, extraterrestrial
Extraterrestrial life
Extraterrestrial life is defined as life that does not originate from Earth...

 source ever discovered, but it has not been detected again in several additional searches.

In 1979 the University of California, Berkeley
University of California, Berkeley
The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...

 launched a SETI project named "Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations (SERENDIP)
SERENDIP
SERENDIP is a Search for Extra-Terrestrial Intelligence program originated at the University of California, Berkeley....

". In 1986, UC Berkeley initiated their second SETI effort, SERENDIP II, and has continued with four more SERENDIP efforts to the present day. The latest incarnation of the SERENDIP project is SERENDIP V.v, a commensal all-sky survey using the Arecibo radio telescope began in June 2009.

Sentinel, META, and BETA


In 1980, Carl Sagan
Carl Sagan
Carl Edward Sagan was an American astronomer, astrophysicist, cosmologist, author, science popularizer and science communicator in astronomy and natural sciences. He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books...

, Bruce Murray
Bruce C. Murray
Bruce C. Murray was born November 30, 1931 in New York, NY. He is a professor emeritus of planetary science and geology at Caltech and was Director of the Jet Propulsion Laboratory from April 1, 1976 to June 30, 1982.He received his Ph.D...

, and Louis Friedman
Louis Friedman
Louis Friedman is an American astronautics engineer and space spokesperson. He was born in New York and raised in the Bronx. Dr. Friedman was a co-founder of The Planetary Society with Carl Sagan and Bruce C. Murray.-Education and career:...

 founded the U.S. Planetary Society
Planetary Society
The Planetary Society is a large, publicly supported, non-government and non-profit organization that has many research projects related to astronomy...

, partly as a vehicle for SETI studies.

In the early 1980s, Harvard University
Harvard University
Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...

 physicist Paul Horowitz
Paul Horowitz
Paul Horowitz is a U.S. physicist and electrical engineer, known primarily for his work in electronics design, as well as for his role in the search for extraterrestrial intelligence .-Biography:...

 took the next step and proposed the design of a spectrum analyzer
Spectrum analyzer
A spectrum analyzer measures the magnitude of an input signal versus frequency within the full frequency range of the instrument. The primary use is to measure the power of the spectrum of known and unknown signals...

 specifically intended to search for SETI transmissions. Traditional desktop spectrum analyzers were of little use for this job, as they sampled frequencies using banks of analog filters and so were restricted in the number of channels they could acquire. However, modern integrated-circuit digital signal processing
Digital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...

 (DSP) technology could be used to build autocorrelation
Autocorrelation
Autocorrelation is the cross-correlation of a signal with itself. Informally, it is the similarity between observations as a function of the time separation between them...

 receivers to check far more channels. This work led in 1981 to a portable spectrum analyzer named "Suitcase SETI" that had a capacity of 131,000 narrow band channels. After field tests that lasted into 1982, Suitcase SETI was put into use in 1983 with the 26-meter Harvard/Smithsonian radio telescope
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...

 at Harvard, Massachusetts
Harvard, Massachusetts
Harvard is a town in Worcester County, Massachusetts, United States. A farming community settled in 1658 and incorporated in 1732, it has been home to several non-traditional communities, such as Harvard Shaker Village and the utopian Transcendentalist center Fruitlands...

. This project was named "Sentinel", and continued into 1985.

Even 131,000 channels weren't enough to search the sky in detail at a fast rate, so Suitcase SETI was followed in 1985 by Project "META", for "Megachannel Extra-Terrestrial Assay". The META spectrum analyzer had a capacity of 8.4 million channels and a channel resolution of 0.05 hertz. An important feature of META was its use of frequency doppler shift to distinguish between signals of terrestrial and extraterrestrial origin. The project was led by Horowitz with the help of the Planetary Society, and was partly funded by movie maker Steven Spielberg
Steven Spielberg
Steven Allan Spielberg KBE is an American film director, screenwriter, producer, video game designer, and studio entrepreneur. In a career of more than four decades, Spielberg's films have covered many themes and genres. Spielberg's early science-fiction and adventure films were seen as an...

. A second such effort, META II, was begun in Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

 in 1990 to search the southern sky. META II is still in operation, after an equipment upgrade in 1996.

The follow-on to META was named "BETA", for "Billion-channel Extraterrestrial Assay", and it commenced observation on October 30, 1995. The heart of BETA's processing capability consisted of 63 dedicated fast Fourier transform
Fast Fourier transform
A fast Fourier transform is an efficient algorithm to compute the discrete Fourier transform and its inverse. "The FFT has been called the most important numerical algorithm of our lifetime ." There are many distinct FFT algorithms involving a wide range of mathematics, from simple...

 (FFT) engines, each capable of performing a 222-point complex FFTs in two seconds, and 21 general-purpose personal computers
IBM PC compatible
IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Such computers used to be referred to as PC clones, or IBM clones since they almost exactly duplicated all the significant features of the PC architecture, facilitated by various manufacturers' ability to...

 equipped with custom digital signal processing
Digital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...

 boards. This allowed BETA to receive 250 million simultaneous channels with a resolution of 0.5 hertz per channel. It scanned through the microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...

 spectrum
Spectrum
A spectrum is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a prism; it has since been applied by...

 from 1.400 to 1.720 gigahertz in eight hops, with two seconds of observation per hop. An important capability of the BETA search was rapid and automatic re-observation of candidate signals, achieved by observing the sky with two adjacent beams, one slightly to the east and the other slightly to the west. A successful candidate signal would first transit the east beam, and then the west beam and do so with a speed consistent with Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

's sidereal
Sidereal time
Sidereal time is a time-keeping system astronomers use to keep track of the direction to point their telescopes to view a given star in the night sky...

 rotation rate. A third receiver observed the horizon to veto signals of obvious terrestrial origin. On March 23, 1999 the 26-meter radio telescope
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...

 on which Sentinel, META and BETA were based was blown over by strong winds and seriously damaged. This forced the BETA project to cease operation.

MOP and Project Phoenix


In 1992, the U.S. government funded an operational SETI program, in the form of the NASA Microwave Observing Program (MOP). MOP was planned as a long-term effort to conduct a general survey of the sky and also carry out targeted searches of 800 specific nearby stars. MOP was to be performed by radio antennas associated with the NASA Deep Space Network
Deep Space Network
The Deep Space Network, or DSN, is a world-wide network of large antennas and communication facilities that supports interplanetary spacecraft missions. It also performs radio and radar astronomy observations for the exploration of the solar system and the universe, and supports selected...

, as well as the 140 feet (42.7 m) radio telescope
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...

 of the National Radio Astronomy Observatory
National Radio Astronomy Observatory
The National Radio Astronomy Observatory is a Federally Funded Research and Development Center of the United States National Science Foundation operated under cooperative agreement by Associated Universities, Inc for the purpose of radio astronomy...

 at Green Bank, West Virginia
Green Bank, West Virginia
Green Bank is a census-designated place in Pocahontas County in West Virginia's Potomac Highlands inside the Allegheny Mountain Range. Green Bank is located along WV 28. Green Bank is also close to the Snowshoe Mountain ski resort...

 and the 1000 feet (304.8 m) radio telescope
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...

 at the Arecibo Observatory
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...

 in Puerto Rico. The signals were to be analyzed by spectrum analyzers, each with a capacity of 15 million channels. These spectrum analyzers could be grouped together to obtain greater capacity. Those used in the targeted search had a bandwidth of 1 hertz per channel, while those used in the sky survey had a bandwidth of 30 hertz per channel.

MOP drew the attention of the U.S. Congress, where the program was ridiculed and canceled a year after its start. SETI advocates continued without government funding, and in 1995 the nonprofit SETI Institute
SETI Institute
The SETI Institute is a not-for-profit organization whose mission is to “explore, understand and explain the origin, nature and prevalence of life in the universe”. SETI stands for the "search for extraterrestrial intelligence". One program is the use of both radio and optical telescopes to search...

 of Mountain View, California resurrected the MOP program under the name of Project "Phoenix", backed by private sources of funding. Project Phoenix
Project Phoenix (SETI)
Project Phoenix is a SETI project: a search for extraterrestrial intelligence by analyzing patterns in radio signals. It is run by the independently funded SETI Institute of Mountain View, California, USA....

, under the direction of Jill Tarter
Jill Tarter
Jill Cornell Tarter is an American astronomer and the current director of the Center for SETI Research, holding the Bernard M. Oliver Chair for SETI at the SETI Institute.-Education:...

, is a continuation of the targeted search program from MOP and studies roughly 1,000 nearby Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

-like stars. From 1995 through March 2004, Phoenix conducted observations at the 64-meter Parkes radio telescope
Parkes Observatory
The Parkes Observatory is a radio telescope observatory, 20 kilometres north of the town of Parkes, New South Wales, Australia. It was one of several radio antennas used to receive live, televised images of the Apollo 11 moon landing on 20 July 1969....

 in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, the 140 feet (42.7 m) radio telescope
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...

 of the National Radio Astronomy Observatory
National Radio Astronomy Observatory
The National Radio Astronomy Observatory is a Federally Funded Research and Development Center of the United States National Science Foundation operated under cooperative agreement by Associated Universities, Inc for the purpose of radio astronomy...

 in Green Bank, West Virginia
Green Bank, West Virginia
Green Bank is a census-designated place in Pocahontas County in West Virginia's Potomac Highlands inside the Allegheny Mountain Range. Green Bank is located along WV 28. Green Bank is also close to the Snowshoe Mountain ski resort...

, and the 1000 feet (304.8 m) radio telescope
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...

 at the Arecibo Observatory
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...

 in Puerto Rico. The project observed the equivalent of 800 stars over the available channels in the frequency range from 1200 to 3000 MHz. The search was sensitive enough to pick up transmitters with 1 GW EIRP
Equivalent isotropically radiated power
In radio communication systems, Equivalent isotropically radiated power or, alternatively, Effective isotropically radiated power is the amount of power that a theoretical isotropic antenna would emit to produce the peak power density observed in the direction of maximum antenna gain...

 to a distance of about 200 light years.

The SETI League and Project Argus


Founded in 1994 in response to the US Congress cancellation of the NASA SETI program, The SETI League, Inc. is a membership-supported nonprofit organization with 1,500 members in 62 countries. This grass-roots alliance of amateur and professional radio astronomers is headed by executive director emeritus Prof. H. Paul Shuch
H. Paul Shuch
Dr. H. Paul Shuch is an American scientist and engineer who has coordinated radio amateurs to help in the search for extraterrestrial intelligence.-Overview:...

, the engineer credited with developing the world's first commercial home satellite TV receiver
Satellite television
Satellite television is television programming delivered by the means of communications satellite and received by an outdoor antenna, usually a parabolic mirror generally referred to as a satellite dish, and as far as household usage is concerned, a satellite receiver either in the form of an...

. Many SETI League members are licensed radio amateurs and microwave experimenters. Others are digital signal processing experts and computer enthusiasts.

The SETI League pioneered the conversion of 3 to 5 metre diameter backyard satellite TV dishes into research-grade radio telescopes of modest sensitivity. The organization concentrates on coordinating a global network of small, amateur-built radio telescopes under Project Argus, an all-sky survey seeking to achieve real-time coverage of the entire sky. Project Argus was conceived as a continuation of the all-sky survey component of the late NASA SETI program (the targeted search having been continued by the SETI Institute's Project Phoenix). There are currently 143 Project Argus radio telescopes operating in 27 countries. Project Argus instruments typically exhibit sensitivity on the order of 10−23 Watts/square metre, or roughly equivalent to that achieved by the Ohio State University Big Ear radio telescope in 1977, when it detected the landmark "Wow!" candidate signal.

The name "Argus" derives from the mythical Greek guard-beast
Argus Panoptes
In Greek mythology, Argus Panoptes or Argos, guardian of the heifer-nymph Io and son of Arestor, was a primordial giant whose epithet "Panoptes", "all-seeing", led to his being described with multiple, often one hundred, eyes. The epithet Panoptes was applied to the Titan of the Sun, Helios, and...

 who had 100 eyes, and could see in all directions at once. In the SETI context, the name has been used for radio telescopes in fiction (Arthur C. Clarke, "Imperial Earth
Imperial Earth
Imperial Earth is a novel written by Arthur C. Clarke, and published in time for the U.S. bicentennial in 1976 by Ballantine Books. The plot follows the protagonist, Duncan Makenzie, on a trip to Earth from his home on Titan, ostensibly for a diplomatic visit to the U.S...

"
; Carl Sagan, "Contact
Contact (novel)
Contact is a science fiction novel written by Carl Sagan and published in 1985. It deals with the theme of contact between humanity and a more technologically advanced, extraterrestrial life form. It ranked No. 7 on the 1985 U.S. bestseller list....

"
), was the name initially used for the NASA study ultimately known as "Cyclops," and is the name given to an omnidirectional radio telescope design being developed at the Ohio State University.

SETI@home



SETI@home was conceived by David Gedye along with Craig Kasnoff and is a popular volunteer distributed computing
Distributed computing
Distributed computing is a field of computer science that studies distributed systems. A distributed system consists of multiple autonomous computers that communicate through a computer network. The computers interact with each other in order to achieve a common goal...

 project that was launched by the University of California, Berkeley
University of California, Berkeley
The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...

 in May 1999. It was originally funded by The Planetary Society
Planetary Society
The Planetary Society is a large, publicly supported, non-government and non-profit organization that has many research projects related to astronomy...

 and Paramount Pictures
Paramount Pictures
Paramount Pictures Corporation is an American film production and distribution company, located at 5555 Melrose Avenue in Hollywood. Founded in 1912 and currently owned by media conglomerate Viacom, it is America's oldest existing film studio; it is also the last major film studio still...

, and later by the state of California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

. The project is run by director David P. Anderson
David P. Anderson
David Pope Anderson is a Research Scientist at the Space Sciences Laboratory, at the University of California, Berkeley, and an Adjunct Professor of Computer Science at the University of Houston...

 and chief scientist Dan Werthimer
Dan Werthimer
Dan Werthimer is co-founder and chief scientist of the SETI@home project and directs other UC Berkeley SETI searches at radio, infrared and visible wavelengths, including the Search for Extra-Terrestrial Radio Emissions from Nearby Developed Intelligent Populations...

. Any individual can become involved with SETI research by downloading the Berkeley Open Infrastructure for Network Computing
Berkeley Open Infrastructure for Network Computing
The Berkeley Open Infrastructure for Network Computing is an open source middleware system for volunteer and grid computing. It was originally developed to support the SETI@home project before it became useful as a platform for other distributed applications in areas as diverse as mathematics,...

 (BOINC) software program, attaching to the SETI@home project, and allowing the program to run as a background process that uses idle computer power. The SETI@home program itself runs signal analysis on a "work unit" of data recorded from the central 2.5 MHz wide band of the SERENDIP IV instrument. After computation on the work unit is complete, the results are then automatically reported back to SETI@home server
Server (computing)
In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...

s at UC Berkeley. As of June 28, 2009 the SETI@home project has over 180,000 active participants volunteering a total of over 290,000 computers. These computers give SETI@home an average computational power of 617 teraFLOPS. Radio source SHGb02+14a
Radio source SHGb02+14a
Radio source SHGb02+14a is a source and a candidate in the Search for Extra-Terrestrial Intelligence , discovered in March 2003 by SETI@home and announced in New Scientist on September 1, 2004....

 is the most interesting signal analyzed to date.

Allen Telescope Array



The SETI Institute
SETI Institute
The SETI Institute is a not-for-profit organization whose mission is to “explore, understand and explain the origin, nature and prevalence of life in the universe”. SETI stands for the "search for extraterrestrial intelligence". One program is the use of both radio and optical telescopes to search...

 has been collaborating with the Radio Astronomy Laboratory at UC Berkeley to develop a specialized radio telescope array for SETI studies, something like a mini-cyclops array. The array concept is named the "Allen Telescope Array" (ATA) (formerly, One Hectare Telescope [1HT]) after the project's benefactor Paul Allen
Paul Allen
Paul Gardner Allen is an American business magnate, investor, and philanthropist. Allen co-founded Microsoft with Bill Gates...

. Its sensitivity will be equivalent to a single large dish more than 100 meters in diameter. The array is being constructed at the Hat Creek Observatory in rural northern California.

The full array is planned to consist of 350 or more Gregorian
Gregorian telescope
The Gregorian telescope is a type of reflecting telescope designed by Scottish mathematician and astronomer James Gregory in the 17th century, and first built in 1673 by Robert Hooke...

 radio dishes, each 6.1 meters (20 ft) in diameter. These dishes are the largest producible with commercially available satellite television
Satellite television
Satellite television is television programming delivered by the means of communications satellite and received by an outdoor antenna, usually a parabolic mirror generally referred to as a satellite dish, and as far as household usage is concerned, a satellite receiver either in the form of an...

 dish technology. The ATA was planned for a 2007 completion date, at a very modest cost of $25 million USD. The SETI Institute provides money for building the ATA while UC Berkeley designs the telescope and provides operational funding. Berkeley astronomers will use the ATA to pursue other deep space radio observations. The ATA is intended to support a large number of simultaneous observations through a technique known as "multibeaming", in which DSP technology is used to sort out signals from the multiple dishes. The DSP system planned for the ATA is extremely ambitious. The first portion of the array became operational in October 2007 with 42 antennas. Completion of the full 350 element array will depend on funding and the technical results from the 42-element sub-array.

CNET
CNET
CNET is a tech media website that publishes news articles, blogs, and podcasts on technology and consumer electronics. Originally founded in 1994 by Halsey Minor and Shelby Bonnie, it was the flagship brand of CNET Networks and became a brand of CBS Interactive through CNET Networks' acquisition...

 published an article and pictures about the Allen Telescope Array (ATA) on December 12, 2008.

In April 2011, the ATA was forced to enter "hibernation" due to funding shortfalls, and is currently inactive.

SETI Net


SETI Net is a private search system created by a single individual. It is closely affiliated with the SETI League and is one of the project Argus stations (DM12jw).

The SETI Net station consists of off-the-shelf, consumer-grade electronics to minimize cost and to allow this design to be replicated as simply as possible. It has a 3-meter parabolic antenna that can be directed in azimuth and elevation, an LNA that covers the 1420 MHz spectrum, a receiver to reproduce the wideband audio, and a standard PC as the control device and for deploying the detection algorithms.

The antenna can be pointed and locked to one sky location, enabling the system to integrate on it for long periods. Currently the Wow! signal
Wow! signal
The Wow! signal was a strong narrowband radio signal detected by Dr. Jerry R. Ehman on August 15, 1977, while working on a SETI project at the Big Ear radio telescope of The Ohio State University then located at Ohio Wesleyan University's Perkins Observatory, Delaware, Ohio. The signal bore...

 area is being monitored when it is above the horizon, but all search data are collected and made available on the internet archive.

SETI Net started operation in the early 1980s as a way to learn about the science of the search, and has developed several software packages for the amateur SETI community. It has provided an astronomical clock, a file manager to keep track of SETI data files, a spectrum analyzer optimized for amateur SETI, remote control of the station from the internet, and other packages.

Realized Interstellar Radio Message Projects


The first Interstellar Radio Message (IRM), "Arecibo Message
Arecibo message
The Arecibo message was broadcast into space a single time via frequency modulated radio waves at a ceremony to mark the remodeling of the Arecibo radio telescope on 16 November 1974. It was aimed at the globular star cluster M13 some 25,000 light years away because M13 was a large and close...

", was transmitted in Nov, 1974 from Arecibo Radar Telescope. IRMs Cosmic Call
Cosmic Call
Cosmic Call was the name of two interstellar radio messages that were sent from RT-70 in Yevpatoria in 1999 and 2003 to various nearby stars. The messages were designed with noise resistant format and characters....

, Teen Age Message
Teen Age Message
The Teen Age Message was a METI message, transmitted from the Yevpatoria Planetary Radar to 6 nearby Sun-like stars during August–September 2001. Unlike the previous digital-only Messages, Arecibo-1974 and Cosmic Call 1, the TAM has complex, three-section structure with different forms of...

, Cosmic Call 2, A Message From Earth
A Message From Earth
A Message from Earth is a high-powered digital radio signal that was sent on 9 October 2008 towards Gliese 581 c, a large terrestrial extrasolar planet orbiting the red dwarf star Gliese 581. The signal is a digital time capsule containing 501 messages that were selected through a competition on...

 were transmitted in 1999, 2001, 2003 and 2008 from Evpatoria Planetary Radar.

Additional information presents at: Communication with Extraterrestrial Intelligence
Communication with Extraterrestrial Intelligence
Communication with extraterrestrial intelligence is a branch of the search for extraterrestrial intelligence 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...

, Active SETI
Active SETI
Active SETI is the attempt to send messages to intelligent aliens. Active SETI messages are usually in the form of radio signals. Physical messages like that of the Pioneer plaque may also be considered an active SETI message...

, List of interstellar radio messages.

Paper Projects


A large number of paper projects also exist. For example, directed by Douglas Vakoch at the SETI Institute in Mountain View CA, the Interstellar Message Composition Project is charged with designing messages that could presumably be sent to extraterrestrials that convey basic scientific or mathematical principles, as well as human altruism
Altruism
Altruism is a concern for the welfare of others. It is a traditional virtue in many cultures, and a core aspect of various religious traditions, though the concept of 'others' toward whom concern should be directed can vary among cultures and religions. Altruism is the opposite of...

. Vackoch's idea is to send a message of reciprocal altruism because hopefully any extraterrestrials would reciprocate with a reply back.

Vakoch has founded "Encoding Altruism", a workshop that started in 2003 in Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...

 that brings together anthropologists, philosophers, physicists, astronomers, theologians, musicians, and artists to address the challenge of communicating with extraterrestrials in a language and syntax that would be intelligible to an alien civilization.

Vakoch's most recent research is highlighted through Greater Good Science Center
Greater Good Science Center
The Greater Good Science Center, located at the University of California, Berkeley is an interdisciplinary research center devoted to the scientific understanding of happy and compassionate individuals, strong social bonds, and altruistic behavior. By studying individuals and their relationships,...

, University of California, Berkeley
University of California, Berkeley
The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...

.

Optical experiments


While most SETI sky searches have studied the radio spectrum, some SETI researchers have considered the possibility that alien civilizations might be using powerful laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...

s for interstellar communications at optical wavelengths. The idea was first suggested by R. N. Schwartz and Charles Hard Townes
Charles Hard Townes
Charles Hard Townes is an American Nobel Prize-winning physicist and educator. Townes is known for his work on the theory and application of the maser, on which he got the fundamental patent, and other work in quantum electronics connected with both maser and laser devices. He shared the Nobel...

 in a 1961 paper published in the journal Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...

titled "Interstellar and Interplanetary Communication by Optical Masers". In 1983, Townes, one of the inventors of the laser, published a detailed study of the idea in the US journal Proceedings of the National Academy of Sciences
Proceedings of the National Academy of Sciences
The Proceedings of the National Academy of Sciences of the United States of America, usually referred to as PNAS, is the official journal of the United States National Academy of Sciences...

. Most SETI researchers agreed with the idea.

The 1971 Cyclops study discounted the possibility of optical SETI, reasoning that construction of a laser system that could outshine the bright central star of a remote star system would be too difficult.

Some SETI advocates, such as Frank Drake
Frank Drake
Frank Donald Drake PhD is an American astronomer and astrophysicist. He is most notable as one of the pioneers in the search for extraterrestrial intelligence, including the founding of SETI, mounting the first observational attempts at detecting extraterrestrial communications in 1961 in Project...

, have suggested that such a judgment was too conservative; early 21st century humans have no means of knowing how a superior technology is communicating or would communicate, and negative results may simply mean humans are making the wrong searches.

There are two problems with optical SETI. The first problem is that lasers are highly "monochromatic", that is, they emit light only on one frequency, making it troublesome to figure out what frequency to look for.

However, according to the uncertainty principle
Uncertainty principle
In quantum mechanics, the Heisenberg uncertainty principle states a fundamental limit on the accuracy with which certain pairs of physical properties of a particle, such as position and momentum, can be simultaneously known...

, emitting light in narrow pulses results in a broad spectrum of emission; the spread in frequency becomes higher as the pulse width becomes narrower, making it easier to detect an emission.

The other problem is that while radio transmissions can be broadcast in all directions, lasers are highly directional. This means that a laser beam could be easily blocked by clouds of interstellar dust, and Earth would have to cross its direct line of fire by chance to receive it.

Optical SETI supporters have conducted paper studies of the effectiveness of using contemporary high-energy lasers and a ten-meter focus mirror as an interstellar beacon. The analysis shows that an infrared pulse from a laser, focused into a narrow beam by such a mirror, would appear thousands of times brighter than the Sun to a distant civilization in the beam's line of fire. The Cyclops study proved incorrect in suggesting a laser beam would be inherently hard to see.

Such a system could be made to automatically steer itself through a target list, sending a pulse to each target at a constant rate. This would allow targeting of all Sun-like stars within a distance of 100 light-years. The studies have also described an automatic laser pulse detector system with a low-cost, two-meter mirror made of carbon composite materials, focusing on an array of light detectors. This automatic detector system could perform sky surveys to detect laser flashes from civilizations attempting contact.

In the 1980s, two Soviet researchers conducted a short optical SETI search, but turned up nothing. During much of the 1990s, the optical SETI cause was kept alive through searches by Stuart Kingsley
Stuart Kingsley
Stuart Kingsley is considered a pioneer in the Optical Search For Extraterrestrial Intelligence, also known as Optical SETI ....

, a dedicated British amateur living in the US state of Ohio.

Several optical SETI experiments are now in progress. A Harvard-Smithsonian group that includes Paul Horowitz designed a laser detector and mounted it on Harvard's 155 centimeter (61 inch) optical telescope. This telescope is currently being used for a more conventional star survey, and the optical SETI survey is "piggybacking" on that effort. Between October 1998 and November 1999, the survey inspected about 2,500 stars. Nothing that resembled an intentional laser signal was detected, but efforts continue. The Harvard-Smithsonian group is now working with Princeton University
Princeton University
Princeton University is a private research university located in Princeton, New Jersey, United States. The school is one of the eight universities of the Ivy League, and is one of the nine Colonial Colleges founded before the American Revolution....

 to mount a similar detector system on Princeton's 91-centimeter (36-inch) telescope. The Harvard and Princeton telescopes will be "ganged" to track the same targets at the same time, with the intent being to detect the same signal in both locations as a means of reducing errors from detector noise.

The Harvard-Smithsonian group is now building a dedicated all-sky optical survey system along the lines of that described above, featuring a 1.8-meter (72-inch) telescope. The new optical SETI survey telescope is being set up at the Oak Ridge Observatory
Oak Ridge Observatory
The Oak Ridge Observatory, also known as the George R. Agassiz Station, is located at 42 Pinnacle Road, Harvard, Massachusetts, and was formerly operated by the Harvard-Smithsonian Center for Astrophysics as a facility of the Smithsonian Astrophysical Observatory .The observatory was established in...

 in Harvard, Massachusetts
Harvard, Massachusetts
Harvard is a town in Worcester County, Massachusetts, United States. A farming community settled in 1658 and incorporated in 1732, it has been home to several non-traditional communities, such as Harvard Shaker Village and the utopian Transcendentalist center Fruitlands...

.

The University of California, Berkeley, home of SERENDIP and SETI@home, is also conducting optical SETI searches. One is being directed by Geoffrey Marcy
Geoffrey Marcy
Geoffrey W. Marcy is an American astronomer, who is currently Professor of Astronomy at the University of California, Berkeley, famous for discovering more extrasolar planets than anyone else, 70 out of the first 100 to be discovered, along with R...

, an extrasolar planet hunter, and involves examination of records of spectra taken during extrasolar planet
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...

 hunts for a continuous, rather than pulsed, laser signal. The other Berkeley optical SETI effort is more like that being pursued by the Harvard-Smithsonian group and is being directed by Dan Werthimer
Dan Werthimer
Dan Werthimer is co-founder and chief scientist of the SETI@home project and directs other UC Berkeley SETI searches at radio, infrared and visible wavelengths, including the Search for Extra-Terrestrial Radio Emissions from Nearby Developed Intelligent Populations...

 of Berkeley, who built the laser detector for the Harvard-Smithsonian group. The Berkeley survey uses a 76-centimeter (30-inch) automated telescope at Leuschner Observatory
Leuschner Observatory
Leuschner Observatory, originally called the Students' Observatory, is an observatory operated by the University of California, Berkeley. The observatory was built in 1886 on the Berkeley campus. For many years, it was directed by Armin Otto Leuschner, for whom the observatory was renamed in 1951...

 and an older laser detector built by Werthimer.

Another form of searching for intelligent life that in addition makes available lower level life-forms was proposed in the July/August 2010 issue of American Astronautical Society
American Astronautical Society
Formed in 1954, the American Astronautical Society is an independent scientific and technical group in the United States dedicated to the advancement of space science and exploration. AAS supports NASA's Vision for Space Exploration and is a member of the Coalition for Space Exploration and the...

's "Space Times" magazine. Titled "Deep Space Astrobiology" written by Eugene F. Lally
Eugene F. Lally
Eugene F. Lally is an American space scientist, spacecraft and mission conceptual designer and photographer, and was born in South Boston, Massachusetts in 1934. He was educated as an electrical engineer at Northeastern University...

 formerly of the Jet Propulsion Laboratory
Jet Propulsion Laboratory
Jet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is headquartered in the city of Pasadena on the border of La Cañada Flintridge and Pasadena...

, an Exoplanet Explorer Spacecraft at the L2 Lagrangian point uses cryogenic infrared spectroscopy to investigate constituents of exoplanet atmospheres. The "Lally Life-forms Probability Index" is discussed for evaluating exoplanet spectra. Lally added additional design information in the Space Times May/June 2011 issue, "Space Exploration...How Far Can We Reach and How Do We Get There" and in the Space Times September/October 2011 "Exploring for Life in Our Galaxy...A Different Approach Using an Unmanned Spacecraft" to discover life-forms outside of our solar system.

Probe SETI and SETA experiments


The possibility of using interstellar messenger probes in the search for extraterrestrial intelligence was first suggested by Ronald N. Bracewell
Ronald N. Bracewell
Ronald Newbold Bracewell AO was the Lewis M. Terman Professor of Electrical Engineering, Emeritus of the at Stanford University.- Education :...

 in 1960 (see Bracewell probe
Bracewell probe
A Bracewell probe is a hypothetical concept for an autonomous interstellar space probe dispatched for the express purpose of communication with one or more alien civilizations. It was proposed by Ronald N...

), and the technical feasibility of this approach was demonstrated by the British Interplanetary Society's starship study Project Daedalus
Project Daedalus
Project Daedalus was a study conducted between 1973 and 1978 by the British Interplanetary Society to design a plausible unmanned interstellar spacecraft. Intended mainly as a scientific probe, the design criteria specified that the spacecraft had to use current or near-future technology and had to...

 in 1978. Starting in 1979, Robert Freitas
Robert Freitas
Robert A. Freitas Jr. is a Senior Research Fellow, one of four researchers at the nonprofit foundation Institute for Molecular Manufacturing in Palo Alto, California. He holds a 1974 Bachelor's degree majoring in both physics and psychology from Harvey Mudd College, and a 1978 Juris Doctor degree...

 advanced arguments for the proposition that physical space-probes are a superior mode of interstellar communication to radio signals. See Voyager Golden Record
Voyager Golden Record
The Voyager Golden Records are phonograph records which were included aboard both Voyager spacecraft, which were launched in 1977. They contain sounds and images selected to portray the diversity of life and culture on Earth, and are intended for any intelligent extraterrestrial life form, or for...

.

In recognition that any sufficiently advanced interstellar probe in the vicinity of Earth could easily monitor our terrestrial Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

, Invitation to ETI was established by Prof. Allen Tough
Allen Tough
Dr. Allen Tough is Professor Emeritus at the University of Toronto. He has contributed to the fields of Adult Education, Futures Studies, and SETI. Linking these fields together is Dr. Tough's concern with the long-term future of humanity in the cosmos, and humans' search for meaning and purpose...

 in 1996, as a Web-based SETI experiment inviting such spacefaring probes to establish contact with humanity. The project's 100 Signatories includes prominent physical, biological, and social scientists, as well as artists, educators, entertainers, philosophers and futurists. Prof. H. Paul Shuch
H. Paul Shuch
Dr. H. Paul Shuch is an American scientist and engineer who has coordinated radio amateurs to help in the search for extraterrestrial intelligence.-Overview:...

, executive director emeritus of The SETI League, serves as the project's Principal Investigator.

In a 2004 paper, C. Rose
Christopher Rose (professor)
Christopher Rose is a professor of electrical and computer engineering at Rutgers University in New Jersey and a founding member of WINLAB. He received a Ph.D from the Massachusetts Institute of Technology in 1985...

 and G. Wright showed that inscribing a message in matter and transporting it to an interstellar destination can be enormously more energy efficient than communication using electromagnetic waves if delays larger than light transit time can be tolerated. That said, for simple messages such as "hello," radio SETI could be far more efficient . If energy requirement is used as a proxy for technical difficulty, then a solarcentric Search for Extraterrestrial Artifacts (SETA) may be a useful supplement to traditional radio or optical searches.

Much like the "preferred frequency" concept in SETI radio beacon theory, the Earth-Moon or Sun-Earth libration
Libration
In astronomy, libration is an oscillating motion of orbiting bodies relative to each other, notably including the motion of the Moon relative to Earth, or of Trojan asteroids relative to planets.-Lunar libration:...

 orbits might therefore constitute the most universally convenient parking places for automated extraterrestrial spacecraft exploring arbitrary stellar systems. A viable long-term SETI program may be founded upon a search for these objects.

In 1979, Freitas and Valdes conducted a photographic search of the vicinity of the Earth-Moon triangular libration points and , and of the solar-synchronized positions in the associated halo orbits, seeking possible orbiting extraterrestrial interstellar probes, but found nothing to a detection limit of about 14th magnitude. The authors conducted a second, more comprehensive photographic search for probes in 1982 that examined the five Earth-Moon Lagrangian positions
Lagrangian point
The Lagrangian points are the five positions in an orbital configuration where a small object affected only by gravity can theoretically be stationary relative to two larger objects...

 and included the solar-synchronized positions in the stable L4/L5 libration orbits, the potentially stable nonplanar orbits near L1/L2, Earth-Moon , and also in the Sun-Earth system. Again no extraterrestrial probes were found to limiting magnitudes of 17–19th magnitude near L3/L4/L5, 10–18th magnitude for /, and 14–16th magnitude for Sun-Earth .

In June 1983, Valdes and Freitas used the 26 m radiotelescope at Hat Creek Radio Observatory to search for the tritium hyperfine line at 1516 MHz from 108 assorted astronomical objects, with emphasis on 53 nearby stars including all visible stars within a 20 light-year radius. The tritium frequency was deemed highly attractive for SETI work because (1) the isotope is cosmically rare, (2) the tritium hyperfine line is centered in the SETI waterhole region of the terrestrial microwave window, and (3) in addition to beacon signals, tritium hyperfine emission may occur as a byproduct of extensive nuclear fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...

 energy production by extraterrestrial civilizations. The wideband- and narrowband-channel observations achieved sensitivities of 5–14 x 10−21 W/m²/channel and 0.7-2 x 10−24 W/m²/channel, respectively, but no detections were made.

Traces of targeted asteroid mining
Asteroid mining
Asteroid mining refers to the possibility of exploiting raw materials from asteroids and planetoids in space, including near-Earth objects. Minerals and volatiles could be mined from an asteroid or spent comet to provide space construction material , to extract water and oxygen to sustain the lives...

 on asteroids and comets could also be utilized for the search of ETI.

Fermi paradox


Italian physicist Enrico Fermi
Enrico Fermi
Enrico Fermi was an Italian-born, naturalized American physicist particularly known for his work on the development of the first nuclear reactor, Chicago Pile-1, and for his contributions to the development of quantum theory, nuclear and particle physics, and statistical mechanics...

 suggested in the 1950s that if technologically advanced civilizations are common in the universe, then they should be detectable in one way or another. (According to those who were there, Fermi either asked "Where are they?" or "Where is everybody?")

The Fermi paradox can be stated more completely as follows:
Possible explanations for the paradox suggest, for example, that while simple life may well be abundant in the universe, intelligent life may be exceedingly rare. In 2000, Peter Ward
Peter Ward (paleontologist)
Peter Douglas Ward is a paleontologist and professor of Biology and of Earth and Space Sciences at the University of Washington, Seattle, and has written popular science works for a general audience. He is also an adviser to the Microbes Mind Forum....

, professor of Biology and of Earth and Space Sciences at the University of Washington
University of Washington
University of Washington is a public research university, founded in 1861 in Seattle, Washington, United States. The UW is the largest university in the Northwest and the oldest public university on the West Coast. The university has three campuses, with its largest campus in the University...

 authored a book claiming the Rare Earth hypothesis
Rare Earth hypothesis
In planetary astronomy and astrobiology, the Rare Earth hypothesis argues that the emergence of complex multicellular life on Earth required an improbable combination of astrophysical and geological events and circumstances...

. In short, the theory claims that the emergence of complex multicellular life (metazoa) on Earth required an extremely unlikely combination of astrophysical and geological events and circumstances. This hypothesis contradicts the principle of mediocrity, which SETI takes as an assumption.

Another suggestion, made by astrophysicist Ray Norris
Ray Norris (astrophysicist)
Ray Norris is an astrophysicist and science communicator at the CSIRO Australia Telescope National Facility, and is well known for his work on Aboriginal Astronomy.-Early life:...

 in 2000 (and subsequently by Allen Tough
Allen Tough
Dr. Allen Tough is Professor Emeritus at the University of Toronto. He has contributed to the fields of Adult Education, Futures Studies, and SETI. Linking these fields together is Dr. Tough's concern with the long-term future of humanity in the cosmos, and humans' search for meaning and purpose...

) was that gamma-ray burst events are sufficiently frequent to sterilize vast swaths of galactic real-estate. This idea was subsequently popularized by physicist Arnon Dar, and described in the show Death Star on PBS Nova.

Science writer Timothy Ferris
Timothy Ferris
Timothy Ferris is a science writer and the best-selling author of twelve books, including The Science of Liberty and Coming of Age in the Milky Way , for which he was awarded the American Institute of Physics Prize and was nominated for the Pulitzer Prize...

 has posited that since galactic societies are most likely only transitory, an obvious solution is an interstellar communications network, or a type of library consisting mostly of automated systems. They would store the cumulative knowledge of vanished civilizations and communicate that knowledge through the galaxy. Ferris calls this the "Interstellar Internet", with the various automated systems acting as network "servers".

If such an Interstellar Internet exists, the hypothesis states, communications between servers are mostly through narrow-band, highly directional radio or laser links. Intercepting such signals is, as discussed earlier, very difficult. However, the network could maintain some broadcast nodes in hopes of making contact with new civilizations.

Although somewhat dated in terms of "information culture" arguments, not to mention the obvious technological problems of a system that could work effectively for billions of years and requires multiple lifeforms agreeing on certain basics of communications technologies, this hypothesis is actually testable (see below).

An alternate hypothesis is that evolutionary pressures in many environments favor species which rapidly consume available resources once they achieve dominance. By the time they have achieved sufficient technology to come to the notice of other civilizations, they are already well on their way to exhausting the resources of their host planet. Therefore the time period available for communication is finite, and very small compared with planetary timescales.

Post Detection Disclosure Protocol


The International Academy of Astronautics
International Academy of Astronautics
The International Academy of Astronautics is an international community of experts committed to expanding the frontiers of space. It is a non-governmental organisation established in Stockholm on August 16, 1960....

 (IAA) has a long-standing SETI Permanent Study Group (SPSG, formerly called the IAA SETI Committee), which addresses matters of SETI science
Science
Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe...

, technology
Technology
Technology is the making, usage, and knowledge of tools, machines, techniques, crafts, systems or methods of organization in order to solve a problem or perform a specific function. It can also refer to the collection of such tools, machinery, and procedures. The word technology comes ;...

, and international policy
International relations
International relations is the study of relationships between countries, including the roles of states, inter-governmental organizations , international nongovernmental organizations , non-governmental organizations and multinational corporations...

. The SPSG meets in conjunction with the International Astronautical Congress (IAC)
International Astronautical Congress
Every year, the International Astronautical Federation together with the International Academy of Astronautics and the International Institute of Space Law , holds the International Astronautical Congress which is hosted by one of the national society members of the IAF.They are an annual meeting...

 held annually at different locations around the world, and sponsors two SETI Symposia at each IAC. In 2005, the IAA established the SETI: Post-Detection Science and Technology Taskgroup (Chairman, Professor Paul Davies
Paul Davies
Paul Charles William Davies, AM is an English physicist, writer and broadcaster, currently a professor at Arizona State University as well as the Director of BEYOND: Center for Fundamental Concepts in Science...

) "to act as a Standing Committee to be available to be called on at any time to advise and consult on questions stemming from the discovery of a putative signal of extraterrestrial intelligent (ETI) origin." It will use, in part, the Rio Scale to evaluate the importance of releasing the information to the public.

When awarded the 2009 TED Prize SETI Institute's Jill Tarter outlined the organisation's "post detection protocol". During NASA's funding of the project, an administrator would be first informed with the intention of informing the United States executive government. The current protocol for SETI Institute is to first internally investigate the signal, seeking independent verification and confirmation. During the process, the organisation's private financiers would be secretly informed. Once a signal has been verified, a telegram would be sent via the Central Bureau for Astronomical Telegrams
Central Bureau for Astronomical Telegrams
The Central Bureau for Astronomical Telegrams is the official international clearing house for information relating to transient astronomical events....

. Following this process, Tarter says that the organisation hold a press conference with the aim of broadcasting to the public. SETI Institute's Seth Shostak
Seth Shostak
Seth Shostak is an American astronomer. He grew up in Arlington, VA and earned his physics degree from Princeton University and a Ph.D...

 has claimed that knowledge of the discovery would likely leak as early as the verification process.

However the protocols mentioned apply only to radio SETI rather than for METI (Active SETI) The intention for METI is covered under the SETI charter "Declaration of Principles Concerning Sending Communications with Extraterrestrial Intelligence".

The SETI Institute does not officially recognise the Wow! signal
Wow! signal
The Wow! signal was a strong narrowband radio signal detected by Dr. Jerry R. Ehman on August 15, 1977, while working on a SETI project at the Big Ear radio telescope of The Ohio State University then located at Ohio Wesleyan University's Perkins Observatory, Delaware, Ohio. The signal bore...

 as of extraterrestrial origin (as it was unable to be verified). The SETI Institute has also publicly denied that the candidate signal Radio source SHGb02+14a
Radio source SHGb02+14a
Radio source SHGb02+14a is a source and a candidate in the Search for Extra-Terrestrial Intelligence , discovered in March 2003 by SETI@home and announced in New Scientist on September 1, 2004....

 is of extraterrestrial origin though full details of the signal, such as its exact location have never been disclosed to the public. Although other volunteering projects such as Zooniverse
Zooniverse (citizen science project)
Zooniverse is a citizen science web portal that grew from the original Galaxy Zoo project. It hosts numerous projects which allow users to participate in scientific research from classifying galaxies to collating climate data...

 credit users for discoveries there is currently no for crediting or early notification of SETI@Home following the discovery of a signal.

Some people, including conspiracy theorists
Conspiracy theory
A conspiracy theory explains an event as being the result of an alleged plot by a covert group or organization or, more broadly, the idea that important political, social or economic events are the products of secret plots that are largely unknown to the general public.-Usage:The term "conspiracy...

, such as Steven M. Greer
Steven M. Greer
Steven M. Greer is an American physician and ufologist who founded the Orion Project and The Disclosure Project.-Biography:Greer claims that he is a contactee who has coined the term "close encounter of the fifth kind" to describe human-initiated contact with extraterrestrials.-The Disclosure...

 have expressed cynicism that the general public might not be informed in the event of a genuine discovery of extraterrestrial intelligence due to significant vested interest
Vested interest
Vested interest is a communication theory that seeks to explain how influences impact behaviors. As defined by William Crano, vested interest refers to the amount that an attitude object is deemed hedonically relevant by the attitude holder...

s. Some, such as Bruce Jakosky
Bruce Jakosky
Bruce Martin Jakosky has been involved with the Viking, Solar Mesosphere Explorer, Clementine, Mars Observer, Mars Global Surveyor, Mars Odyssey, Mars Science Laboratory and MAVEN spacecraft missions, and is involved in planning future spacecraft missions.-Career:Jakosky heads up the University of...

 have also argued that the official disclosure of extraterrestrial life may have far reaching and as yet undetermined implications for society particularly for the world's religion
Religion
Religion is a collection of cultural systems, belief systems, and worldviews that establishes symbols that relate humanity to spirituality and, sometimes, to moral values. Many religions have narratives, symbols, traditions and sacred histories that are intended to give meaning to life or to...

s. Assessing this impact is the intention of the IAA's Rio Scale and these factors present a real motive for withholding the information from the public.

Criticism


As various SETI projects have progressed, some have criticized early claims by researchers as being too "euphoric" or "optimistic." For example, Peter Schenkel, while remaining a supporter of SETI projects, has written that "[i]n light of new findings and insights, it seems appropriate to put excessive euphoria to rest and to take a more down-to-earth view ... We should quietly admit that the early estimates — that there may be a million, a hundred thousand, or ten thousand advanced extraterrestrial civilizations in our galaxy — may no longer be tenable." Clive Trotman presents some sobering but realistic calculations emphasizing the timeframe dimension.

SETI has also occasionally been the target of criticism by those who suggest that it is a form of pseudoscience
Pseudoscience
Pseudoscience is a claim, belief, or practice which is presented as scientific, but which does not adhere to a valid scientific method, lacks supporting evidence or plausibility, cannot be reliably tested, or otherwise lacks scientific status...

. In particular, critics allege that no observed phenomena suggest the existence of extraterrestrial intelligence, and furthermore that the assertion of the existence of extraterrestrial intelligence has no good Popperian
Karl Popper
Sir Karl Raimund Popper, CH FRS FBA was an Austro-British philosopher and a professor at the London School of Economics...

 criteria for falsifiability
Falsifiability
Falsifiability or refutability of an assertion, hypothesis or theory is the logical possibility that it can be contradicted by an observation or the outcome of a physical experiment...

.

In response, SETI advocates note, among other things, that the Drake Equation
Drake equation
The Drake equation is an equation used to estimate the number of detectable extraterrestrial civilizations in the Milky Way galaxy. It is used in the fields of exobiology and the Search for ExtraTerrestrial Intelligence...

 was never a hypothesis, and so never intended to be testable, nor to be "solved"; it was merely a clever representation of the agenda for the world's first scientific SETI meeting in 1961, and it serves as a tool in formulating testable hypotheses. Further, they note that the existence of intelligent life on Earth is a plausible reason to expect it elsewhere, and that individual SETI projects have clearly defined "stop" conditions. Many detractors have not considered the collection and processing of data, the first order of business, and the refining of those data streams, in the case of SETI through algorithm optimization. To justify SETI projects does not require an acceptance of the Drake equation. Science proceeds through hypothesis. If one were to only take what was at face value observable, many scientific phenomena never would have been discovered.

The search for extraterrestrial intelligence is not an assertion that extraterrestrial intelligence exists or are visiting earth, and conflating the two can be seen as a straw man argument. There is an effort to distinguish the SETI projects from UFOlogy
Ufology
Ufology is a neologism coined to describe the collective efforts of those who study reports and associated evidence of unidentified flying objects . UFOs have been subject to various investigations over the years by governments, independent groups, and scientists...

, the study of UFOs, which many consider to be pseudoscience. In Skeptical Inquirer
Skeptical Inquirer
The Skeptical Inquirer is a bimonthly American magazine published by the Committee for Skeptical Inquiry with the subtitle: The magazine for science and reason....

, Mark Moldwin argued that the important differences between the two projects were the acceptance of SETI by the mainstream scientific community and that "[t]he methodology of SETI leads to useful scientific results even in the absence of discovery of alien life."

Some in the UFO community, such as nuclear physicist Stanton Friedman, say there is no basis for the search and it is therefore unscientific. Friedman has challenged SETI specialists to debate the issues, with no takers so far. Examples of objections to SETI include questioning energy requirements as well as why advanced civilizations would use radio.

Active SETI



Active SETI
Active SETI
Active SETI is the attempt to send messages to intelligent aliens. Active SETI messages are usually in the form of radio signals. Physical messages like that of the Pioneer plaque may also be considered an active SETI message...

, also known as messaging to extraterrestrial intelligence (METI), consists of sending signals into space in the hope that they will be picked up by an alien intelligence. Physicist Stephen Hawking
Stephen Hawking
Stephen William Hawking, CH, CBE, FRS, FRSA is an English theoretical physicist and cosmologist, whose scientific books and public appearances have made him an academic celebrity...

, in his book A Brief History of Time, suggests that "alerting" extraterrestrial intelligences of our existence is foolhardy, citing mankind's history of treating his fellow man harshly in meetings of civilizations with a significant technology gap. He suggests, in view of this history, that we "lay low".

The concern over SETI 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
International Academy of Astronautics
The International Academy of Astronautics is an international community of experts committed to expanding the frontiers of space. It is a non-governmental organisation established in Stockholm on August 16, 1960....

 SETI study group. The editor said, "It is not obvious that all extraterrestrial civilizations will be benign, or that contact with even a benign one would not have serious repercussions" (Nature Vol 443 12 Oct 06 p 606). Astronomer and science fiction author David Brin
David Brin
Glen David Brin, Ph.D. is an American scientist and award-winning author of science fiction. He has received the Hugo, Locus, Campbell and Nebula Awards.-Biography:...

 has expressed similar concerns.

Richard Carrigan, a particle physicist at the Fermi National Accelerator Laboratory near Chicago, Illinois, suggested that passive SETI could also be dangerous in the style of computer virus
Computer virus
A computer virus is a computer program that can replicate itself and spread from one computer to another. The term "virus" is also commonly but erroneously used to refer to other types of malware, including but not limited to adware and spyware programs that do not have the reproductive ability...

es. Computer security expert Bruce Schneier
Bruce Schneier
Bruce Schneier is an American cryptographer, computer security specialist, and writer. He is the author of several books on general security topics, computer security and cryptography, and is the founder and chief technology officer of BT Managed Security Solutions, formerly Counterpane Internet...

 dismissed this possibility as a "bizarre movie-plot threat".

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 adopted in 2007 a new analytical tool, the San Marino Scale
San Marino Scale
In exopolitics, the San Marino Scale is a suggested scale for assessing risks associated with deliberate transmissions from Earth aimed to possible extraterrestrial intelligent life. The scale was suggested by Iván Almár at a conference in San Marino in 2005...

. Developed by Prof. Ivan Almar and Prof. H. Paul Shuch
H. Paul Shuch
Dr. H. Paul Shuch is an American scientist and engineer who has coordinated radio amateurs to help in the search for extraterrestrial intelligence.-Overview:...

, the 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 equal, and each must be evaluated separately before establishing blanket international policy regarding active SETI.

However, some scientists consider these fears about the dangers of METI as panic and irrational superstition
Superstition
Superstition is a belief in supernatural causality: that one event leads to the cause of another without any process in the physical world linking the two events....

; see, for example, Alexander L. Zaitsev's papers.

See also



  • Alien language
    Alien language
    Alien language is a generic term used to describe a possible language originating from a hypothetical alien species. The study of such a hypothetical language has been termed xenolinguistics, although alternative terminology such as exolinguistics has found its way into use through the medium of...

  • Arecibo Message
    Arecibo message
    The Arecibo message was broadcast into space a single time via frequency modulated radio waves at a ceremony to mark the remodeling of the Arecibo radio telescope on 16 November 1974. It was aimed at the globular star cluster M13 some 25,000 light years away because M13 was a large and close...

  • Astrobiology Science and Technology for Exploring Planets
  • Astrobiology
    Astrobiology
    Astrobiology is the study of the origin, evolution, distribution, and future of life in the universe. This interdisciplinary field encompasses the search for habitable environments in our Solar System and habitable planets outside our Solar System, the search for evidence of prebiotic chemistry,...

  • Communication with extraterrestrial intelligence
    Communication with Extraterrestrial Intelligence
    Communication with extraterrestrial intelligence is a branch of the search for extraterrestrial intelligence 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...

  • Darwin Mission
  • First contact (science fiction)
    First contact (science fiction)
    First contact is a common science fiction theme about the first meeting between humans and extraterrestrial life, or of any sentient race's first encounter with another one....

  • Iosif Shklovsky
    Iosif Shklovsky
    Iosif Samuilovich Shklovsky was a Soviet astronomer and astrophysicist...



  • Metalaw
    Metalaw
    Metalaw is a concept of space law closely related to the scientific Search for Extraterrestrial Intelligence .Immanuel Kant and his Categorical imperative: "Act only according to that maxim whereby you can at the same time will that it should become a universal law" is the forerunner of the...

  • Ohio State University Radio Observatory (The Big Ear)
  • Open SonATA
    Open SonATA
    Open SonATA stands for Open SETI on the Allen Telescope Array and is the open source version of the software are used for signal detection by the SETI Institute on the Allen Telescope Array . The software currently runs on GNU/Linux and Mac OS operating systems and is intended to be ported to...

  • SETI@home
    SETI@home
    SETI@home is an Internet-based public volunteer computing project employing the BOINC software platform, hosted by the Space Sciences Laboratory, at the University of California, Berkeley, in the United States. SETI is an acronym for the Search for Extra-Terrestrial Intelligence...

  • setiQuest
    SetiQuest
    setiQuest is a project of the SETI Institute, whose declared aim is to "globalize the search for extra-terrestial intelligence and empower a new generation of SETI enthusiasts", by creating means for a deeper involvement from the interested public...

  • Space archaeology
    Space archaeology
    In archaeology, space archaeology refers to the study of various human-made items found in space, their interpretation as clues to the adventures mankind has experienced in space, and their preservation as cultural heritage....

  • Terrestrial Planet Finder
    Terrestrial Planet Finder
    The Terrestrial Planet Finder was a proposed project by NASA to construct a system of telescopes for detecting extrasolar terrestrial planets. TPF was postponed several times and finally cancelled...



Further reading


  • Frank White: The Seti Factor – How the Search for Extraterrestrial Intelligence Is Changing Our View of the Universe and Ourselves. Walker & Company, New York 1990, ISBN 978-0-8027-1105-2
  • David W. Swift: Seti Pioneers — Scientists Talk about Their Search for Extraterrestrial Intelligence. Univ. of Arizona Press, Tucson 1993, ISBN 0-8165-1119-5
  • P.Morrison, J.Billingham, J.Wolfe: The search for extraterrestrial intelligence-SETI. NASA SP, Washington 1977,online
  • Brian MacConnell: Beyond contact – a guide to SETI and communicating with Alien civilizations. O'Reilly, Beijing 2001, ISBN 0-596-00037-5.

External links