Search for Extra-Terrestrial Intelligence (SETI) is the collective name for a number of activities to detect intelligent
extraterrestrial life. The general approach of SETI projects is to survey the skyto detect the existence of transmissions from a civilization on a distant planet – an approach widely endorsed by the scientific communityas hard science(see, "e.g.", claims in " Skeptical Inquirer" [Mark Moldwin, [http://findarticles.com/p/articles/mi_m2843/is_6_28/ai_n6361832/pg_1 Why SETI is science and UFOlogy is not] , "Skeptical Inquirer", Nov-Dec, 2004.] ). The United States Government contributed to SETI early on, but recent work has been primarily funded by private sources.
There are great challenges in searching across the sky 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, and thus no exhaustive search has so far been conducted.
ETI's experiments with radios
Early work, the "Wow!" signal, and SERENDIP
Cornell Universityastronomer Frank Drakeperformed the first modern SETI experiment, named " Project Ozma", after the Queen of Oz in L. Frank Baum's fantasy books. Drake used a 25-meter-diameter radio telescope at Green Bank, West Virginia, to examine the stars Tau Cetiand Epsilon Eridaninear the 1.420 gigahertz marker frequency. 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.
The first SETI conference took place at Green Bank in 1961. The
Soviets took a strong interest in SETI during the 1960s and performed a number of searches with omnidirectional antennas in the hope of picking up powerful radio signals. TV host and American astronomer Carl Saganand Soviet astronomer Iosif Shklovskii together wrote the pioneering book in the field, "Intelligent Life in the Universe" which was published in 1966.cite book | first = Carl | last = Sagan | coauthors = Iosif Shklovskii | title = Intelligent Life in the Universe | year = 1966]
In the March 1955 issue of
Scientific American, Dr. John Kraus, Professor Emeritus and McDougal Professor of Electrical Engineeringand Astronomyat the Ohio State University, described a concept to scan the cosmosfor natural radio signals using a flat-plane radio telescopeequipped with a parabolic reflector. Within two years, his concept was approved for construction by the Ohio State University. With $71,000 total in grants from the National Science Foundation, construction of the first Kraus-style radio telescope began on a 20 acre plot in Delaware, Ohio. The convert|360|ft|m wide, convert|500|ft|m long, and convert|70|ft|m high telescope was powered up in 1963. This Ohio State University radio telescopewas called Big Ear. Later, it began the world's first continuous SETI program, called the Ohio State University SETI program.
NASAfunded a SETI study that involved Drake, Bernard Oliverof Hewlett-PackardCorporation, and others. The resulting report proposed the construction of an Earth-based radio telescope array with 1,500 dishes known as " Project Cyclops". The price tag for the Cyclops array was $10 billion USD. Cyclops was not built, but the report [ [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730010095_1973010095.pdf NASA Technical Report CR-114445 - Project Cyclops: A design study of a system for detecting extraterrestial intelligent life] . 14.5 MB pdf file.] formed the basis of much SETI work that followed.
In 1974, a largely symbolic attempt was made at the
Arecibo Observatoryto send a message 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 Dr.
Jerry R. 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", is considered by some to be the most likely candidate from an artificial, extraterrestrial source ever discovered, but it has not been detected again in several additional searches.
In 1979 the
University of California, Berkeleylaunched a SETI project named "Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations (SERENDIP)".cite web | url = http://seti.ssl.berkeley.edu/serendip/ | title = SERENDIP | publisher = UC Berkeley| accessdate = 2006-06-12] In 1986, UC Berkeley initiated their second SETI effort, SERENDIP II, and has continued with two more SERENDIP efforts to the present day.
"SETI@home" is an extremely popular
volunteer computingproject that was launched by U.C. Berkeley in May 1999. It was funded originally by the The Planetary Society and Paramount picturesand later by the State of California. The project is run by director David P. Andersonand chief scientist Dan Werthimer. Any individual can become involved with SETI research by downloading and running the SETI@home software package, which then runs signal analysis on a "work unit" of data recorded from the central 2.5 MHz wide band of the SERENDIP IV instrument. The results are then automatically reported back to UC Berkeley. Over 5 million computer users in more than 200 countries have signed up for SETI@home and have collectively contributed over 19 billion hours of computerprocessing time.cite web | url = http://seticlassic.ssl.berkeley.edu/totals.html | title = SETI@home Classic — Current Total Statistics | accessdate = 2006-06-12] cite web | url = http://www.boincstats.com/ | title = BOINCstats | accessdate = 2008-01-29] As of January 29, 2008the Seti@home achieves an average throughput of 387 TeraFLOPS, making it equivalent to the second fastest supercomputeron Earth. [ [http://www.boincstats.com/stats/project_graph.php?pr=sah "BOINC Stats"] ] Radio source SHGb02+14ais the most interesting signal analyzed to date.
entinel, META, and BETA
Carl Sagan, Bruce Murray, and Louis Friedmanfounded the U.S. Planetary Society, partly as a vehicle for SETI studies.
In the early 1980s,
Harvard Universityphysicist Paul Horowitztook the next step and proposed the design of a spectrum analyzer 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(DSP) technology could be used to build autocorrelationreceivers 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 telescopeat Harvard, Massachusetts. 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 shiftto 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. A second such effort, META II, was begun in Argentina 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 FFT engines, each capable of performing a 222-point complex fast Fourier transformin two seconds, and 21 general-purpose PCs equipped with custom digital signal processingboards. This allowed BETA to receive 250 million simultaneous channels with a resolution of 0.5 hertz per channel. It scanned through the microwave spectrumfrom 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 the earth's siderealrotation rate. A third receiver observed the horizon to veto signals of obvious terrestrial origin. On March 23, 1999the 26-meter radio telescopeon 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, performing a "Targeted Search" of 800 specific nearby stars, along with a general "Sky Survey" to scan the sky. MOP was to be performed by radio dishes associated with the NASA
Deep Space Network, as well as a 43-meter dish at Green Bank and the big Arecibo dish. The signals were to be analyzed by spectrum analyzers, each with a capacity of 15 million channels. These spectrum analyzers could be ganged 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 strongly ridiculed, and was canceled a year after its start. SETI advocates did not give up, and in 1995 the nonprofit SETI Instituteof Mountain View, California, resurrected the work under the name of Project "Phoenix", backed by private sources of funding. Project Phoenix, under the direction of Dr. Jill Tarter, previously Project Scientist for the NASA project, is a continuation of the Targeted Search program, studying roughly 1,000 nearby Sun-like stars. Seth Shostakalso worked on Project Phoenix. From 1995 through March 2004, Phoenix conducted observing campaigns at the 64-meter Parkes radio telescope in Australia, the convert|140|ft|m|sing=on Telescope of the National Radio Astronomy Observatory in West Virginia, USA, and the Arecibo Observatory 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 to a distance of about 200 light years. (A typical airport radar has this much peak power, but is only on about 1/1000 of the time, and would not have been detected in this survey.)
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 1500 members in 62 countries on all seven continents. This grass-roots alliance of amateur and professional radio astronomers is headed by executive director emeritus Prof.
H. Paul Shuch, the engineer credited with developing the world's first commercial home satellite TV receiver. 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. [cite journal |last=Chown |first=Marcus |journal=New Scientist |title=The Alien Spotters |year=1997, 19 April |pages=p. 28 |url=http://www.newscientist.com/article/mg15420784.500-the-alien-spotters.html |accessdate=2008-04-13] 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 Insititute's Project Phoenix). There are currently 135 Project Argus radio telescopes operating in 26 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.
Allen Telescope Array
The SETI Institute is now 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 new array concept is named the "Allen Telescope Array" (ATA) (formerly, One Hectare Telescope [1HT] ) after the project's benefactor
Paul Allen. 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 Observatoryin rural northern California.cite web | url = http://www.seti.org/site/pp.asp?c=ktJ2J9MMIsE&b=179146 | title = Allen Telescope Array General Overview | publisher = SETI Institute| accessdate = 2006-06-12]
The full array is planned to consist of 350 or more Gregorian radio dishes, each 6.1 meters (20 ft) in diameter. These dishes are the largest producible with commercially available
satellite televisiondish 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.
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 parabola antenna that can be directed in azimuth and elevation, a LNA that covers the 1420 MHz spectrum, a receiver to produce the wideband audio and a standard PC computer for control and for the detection algorithms.
The antenna can be pointed and locked to one sky location enabeling the system to integrate on it for long periods. Currently the
Wow! signalarea is being monitored when it is above the horizon but all search data is collected and made available on the internet archive.
SETI Net started operation in the early 80’s 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.
Interstellar Message Realized and Paper Projects
First Interstellar Radio Message (IRM), "
Arecibo Message", was transmitted in Nov, 1974 from Arecibo Radar Telescope. IRMs Cosmic Call, Teen Age Message, and Cosmic Call 2were transmitted in 1999, 2001, and 2003 from EupatoriaPlanetary Radar, more info in Communication with Extraterrestrial Intelligenceand Active SETI.
Directed by Douglas Vakoch at SETI in Mountain View, the Interstellar Message Composition Project is charged with sending messages to extraterrestrials that convey basic scientific or mathematical principles, as well as human altruism. 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 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 intellegible to an alien civilization.
Vakoch's most recent research is highlighted through
Greater Good Science Center, University of California, Berkeley.
Optical SETI 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
lasers for interstellar communications at optical wavelengths. The idea was first suggested in a paper published in the British journal "Nature" in 1961, and in 1983 Charles 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". 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 sun of a remote star system would be too difficult. Now some SETI advocates, such as Frank Drake, 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. 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, emitting light in narrow pulses results in a broad spectrum of emission, with the spread in frequency becoming 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 [cite book | author = Exers, Ronald, D. Cullers, J. Billingham, L. Scheffer (editors) | title = SETI 2020: A Roadmap for the Search for Extraterrestrial Intelligence | year = 2003 | publisher = SETI Press | id = ISBN 0-9666335-3-9] 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, 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 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 Observatoryin Harvard, Massachusetts.
The University of California, Berkeley, home of SERENDIP and SETI@home, is also conducting optical SETI searches. One is being directed by
Geoffrey Marcy, an extrasolar planet hunter, and involves examination of records of spectra taken during extrasolar planethunts 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 Werthimerof Berkeley, who built the laser detector for the Harvard-Smithsonian group. The Berkeley survey uses a 76-centimeter (30-inch) automated telescope and an older laser detector built by Werthimer.
Probe SETI and SETA experiments
The possibility of using interstellar messenger probes in the search for extraterrestrial intelligence was first suggested by
Ronald N. Bracewellin 1960 (see Bracewell probe), and the technical feasibility of this approach was demonstrated by the British Interplanetary Society's starship study Project Daedalusin 1978. Starting in 1979, Robert Freitasadvanced arguments [ [http://www.rfreitas.com/Astro/InterstellarProbesJBIS1980.htm "Interstellar probes - A new approach to SETI"] - by Robert A. Freitas Jr.] [ [http://www.rfreitas.com/Astro/ProbeMyths1983.htm "Debunking the Myths of Interstellar Probes"] - by Robert A. Freitas Jr.] [ [http://www.rfreitas.com/Astro/TheCaseForInterstellarProbes1983.htm "The Case for Interstellar Probes"] - by Robert A. Freitas Jr.] for the proposition that physical space-probes are a superior mode of interstellar communication to radio signals.
In recognition that any sufficiently advanced interstellar probe in the vicinity of Earth could easily monitor our terrestrial internet,
Invitation to ETIwas established by Prof. Allen Toughin June, 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, executive director emeritus of The SETI League, serves as the project's Principal Investigator.
In a September 2004 paper featured on the cover of "Nature" [ [http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v431/n7004/index.html "Nature Magazine"] - Volume 431 Number 7004 pp1-109, issue (2 September 2004)] , Christopher Rose and
Gregory Wrightshowed that inscribing a message in matter and transporting it to the destination is vastly more energy efficient than communication using electromagnetic waves if the message can tolerate delivery delay beyond light transit time [ [http://www.nature.com/nature/journal/v431/n7004/full/nature02884.html "Nature Magazine"] - with registration] [ [http://www.winlab.rutgers.edu/~crose/papers/nature.pdf "Inscribed matter as an energy efficient means of communication with an extraterrestrial civilization"] - winlab.rutgers.edu] [ [http://www.winlab.rutgers.edu/~crose/cgi-bin/cosmic23.html "Cosmic Communications"] - winlab.rutgers.edu] . Thus, a solarcentric Search for Extraterrestrial Artifacts (SETA) [ [http://www.rfreitas.com/Astro/SETAJBISNov1983.htm "The Search for Extraterrestrial Artifacts (SETA)"] - by Robert A. Freitas Jr., Xenology Research Institute] would seem to be favored over the more traditional radio or optical searches.
Much like the "preferred frequency" concept in SETI radio beacon theory, the Earth-Moon or Sun-Earth
librationorbits 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 L4 and L5, 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. [http://www.rfreitas.com/Astro/SearchIcarus1980.htm "A Search for Natural or Artificial Objects Located at the Earth-Moon Libration Points"] ] The authors conducted a second, more comprehensive photographic search for probes in 1982 [ [http://www.rfreitas.com/Astro/SearchIcarus1983.htm "A Search for Objects near the Earth-Moon Lagrangian Points"] - By Francisco Valdes] that examined the five Earth-Moon
Lagrangianpositions and included the solar-synchronized positions in the stable L4/L5 libration orbits, the potentially stable nonplanar orbits near L1/L2, Earth-Moon L3, and also L2 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 L1/L2, and 14-16th magnitude for Sun-Earth L2.
In June 1983, Valdes and Freitas [ [http://www.rfreitas.com/Astro/TritiumSearch1986.htm "A Search for the Tritium Hyperfine Line from Nearby Stars"] - By Francisco Valdes] 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 regionof the terrestrial microwave window, and (3) in addition to beacon signals, tritium hyperfine emission may occur as a byproduct of extensive nuclear fusion 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.
Where are they?
Enrico Fermisuggested 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, [Eric Jones, [http://www.fas.org/sgp/othergov/doe/lanl/la-10311-ms.pdf "Where is everybody?", An account of Fermi's question"] , Los Alamos Technical report LA-10311-MS, March, 1985.] Fermi either asked "Where are they?" or "Where is everybody?")
The Fermi paradox can be stated more completely as follows:
The size and age of the universe incline us to believe that many technologically advanced civilizations must exist. However, this belief seems logically inconsistent with our lack of observational evidence to support it. Either the initial assumption is incorrect and technologically advanced intelligent life is much rarer than we believe, our current observations are incomplete and we simply have not detected them yet, or our search methodologies are flawed and we are not searching for the correct indicators.
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, professor of Biology and of Earth and Space Sciences at the
University of Washingtonauthored a book claiming the Rare Earth hypothesis. In short, the theory claims that the emergence of complex multicellular life( metazoa) on Earth required an extremely unlikely combination of astrophysicaland geologicalevents and circumstances. This hypothesis contradicts the principle of mediocrity, which SETI takes as an assumption.
Another suggestion, made by astrophysicist
Ray Norrisin 2000 [cite journal
authorlink = Ray Norris | title = How old is ET | journal = Acta Astraonautica | volume = 2-9 | pages = 731–733 | year = 2000] (and subsequently by
first = Allen | last = Tough | author-link = Allen Tough | title = When SETI Succeeds: The Impact of High-Information Contact | place = Bellevue, Washington | publisher = Foundation For the Future | year = 2000 | doi = | isbn = 0-9677252-2-4 ] ) was that
gamma-ray burstevents are sufficiently frequent to sterilize vast swaths of galactic real-estate. This idea was subsequently popularized by physicist Arnon Dar, and described in the PBS Novashow 'Death Star'. [ [http://www.pbs.org/wgbh/nova/gamma/ NOVA Online | Death Star ] ]
Timothy Ferrishas posited that since galactic societies would most likely be only transitory, then an obvious solution is an interstellar communications network, or 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).
Others believe that intelligent life would or will communicate through an obvious medium. Mostly this is based on experimental supposition.
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.
International Academy of Astronautics(IAA) has a long-standing SETI Permanent Study Group (SPSG, formerly called the IAA SETI Committee), which addresses matters of SETI science, technology, and international policy. The SPSG meets in conjunction with the International Astronautical Congress (IAC) held annually at different locations around the world, and sponsors two SETI Symposia at each IAC.
In 2005, the International Academy of Astronautics established the (Chairman, Professor
Paul Davies) "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 Scaleto evaluate the importance of releasing the information to the public.
Criticism of SETI
As various SETI projects have continued, some have criticized early claims by researchers now seen to be 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." [ [http://www.csicop.org/si/2006-03/seti.html SETI Requires a Skeptical Reappraisal (Skeptical Inquirer May/June 2006) ] ]
SETI has also occasionally been the target of criticism by those who suggest that it is a form of
pseudoscience. 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 criteria for falsifiability. [ [http://web.archive.org/web/*/http://www.theness.com/articles/seti-nejs0101.html Internet Archive Wayback Machine ] ] Science fictionwriter Michael Crichton, in a 2003 lecture at Caltech, stated that "The Drake equationcannot be tested and therefore SETI is not science. SETI is unquestionably a religion." [ [http://www.crichton-official.com/speeches/speeches_quote04.html Welcome to MichaelCrichton.com ] ]
In response, SETI advocates note, among other things, that the Drake Equation was never intended to be tested, and is in fact not really an equation intended to be "solved" at all, but was merely a clever representation of the agenda for the world's first scientific SETI meeting in 1961. Further, SETI proponents 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. 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, has not been considered by many of these detractors. Concerning the latter argument, the justification for SETI projects doesn't necessarily require an acceptance of the Drake equation. Science proceeds through hypothesis. If one were only to take what was at face value observable, many scientific phenomena never would have been discovered. In addition it should be noted that the Drake equation by itself is not an hypothesis and hence it is not even supposed to be testable. The equation can serve as a tool in formulating testable hypotheses.
The "search" for extraterrestrial intelligence is not an assertion that extraterrestrial intelligence exists, and conflating the two can be seen as a
straw man argument. There is an effort to distinguish the SETI projects from UFOlogy, the study of UFOs considered to be pseudoscience by many. In " Skeptical Inquirer", Mark Moldwin explicitly made the distinction between the two projects, arguing that an important discriminator was 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." [ [http://www.arn.org/docs/williams/pw_setivsufology.htm In a recent Skeptical Inquirer article, ‘Why SETI IS Science and UFOlogy Is Not: A Space Science Perspective on Boundaries’ (V ] ]
Is "active" SETI dangerous?
Positive SETI (also known as "active SETI" or as METI = "messages to extraterrestrial intelligence") consists of sending signals into space in the hope that they will be picked up by an alien intelligence. Some feel that this activity contains improbable but real dangers and ought to be discussed more broadly before it is undertaken.
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 AstronauticsSETI 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 Brinhas expressed similar concerns. [ [http://lifeboat.com/ex/shouting.at.the.cosmos LF Special Report: Shouting at the cosmos ] ]
As was suggested by Richard Carrigan, a particle physicist at the US Fermi National Accelerator Laboratory in Illinois, 'passive' SETI could also be dangerous in the style of computer viruses. [http://home.fnal.gov/~carrigan/SETI/SETI%20Hacker_AC-03-IAA-8-3-06.doc]
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. [ [http://iaaseti.org/smiscale.htm International Academy of Astronautics, SETI Permanent Study Group ] ] Developed by Prof.
Ivan Almarand Prof. H. Paul Shuch, the San Marino Scaleevaluates the significance of transmissions from Earth as a function of signal intensity and information content. Its adoption suggests that not all such transmissions are created equal, thus each must be evaluated on a case-by-case basis before establishing blanket international policy regarding Active SETI.
Communication with Extraterrestrial Intelligence
*European Darwin Project
Terrestrial Planet Finder
*"Contact", a novel by SETI advocate
Carl Sagan, later made into a film
References and notes
* [http://www.iaaweb.org/ International Academy of Astronautics]
* [http://iaaseti.org/ IAA SETI Permanent Study Group]
* [http://www.seti.org/ SETI Institute]
* [http://www.seti-uk.co.uk/ SETI Research UK]
* [http://www.setileague.org/ The SETI League]
* [http://www.setileague.org/iaaseti/postdet.htm SETI Post-Detection taskgroup]
* [http://setiathome.ssl.berkeley.edu/ SETI@home] , the
* [http://www.planetary.org/ The Planetary Society]
* [http://ieti.org/ Invitation to ETI]
* [http://spsr.utsi.edu/ SPSR] The Society for Planetary SETI Research
* [http://www.coseti.org The Columbus Optical SETI Observatory, Dr. Stuart A, Kingsley]
* [http://www.openseti.org Open SETI Initiative] – Gerry Zeitlin's site concerned with reforming SETI's approach
* [http://www.bigear.org/ Big Ear Memorial Website] - discovered the "
Wow! signal" and has entry in Guinness Book of Records
* [http://www.naapo.org/ NAAPO] , North American AstroPhysical Observatory (formerly Big Ear)
* [http://www.seti.net/ SETI Net] , Single developer amateur SETI station
Academic journals, reports and publications
* [http://cic.setileague.org/ Contact in Context] (peer-reviewed online scholarly journal)
* [http://www.setileague.org/srchlite/ SearchLites] (quarterly newsletter of The SETI League, Inc.)
* [http://www.boulder.swri.edu/CSEPR/projects/readings/race-need_for_operating_guidelines.pdf "SETI Principles"] as defined from the
Department of Space Studiesof the Southwest Research Institute(PDF File)
* [http://seti.harvard.edu/seti/ Harvard University SETI page]
* [http://www.markelowitz.com/exobiology.htm Mark Elowitz's Web site on Exobiology and SETI]
* [http://history.nasa.gov/SP-419/sp419.htm "The Search For Extraterrestrial Intelligence" (NASA SP-419, 1977)]
* [http://www.ieti.org/tough/books/succeeds.htm When SETI Succeeds: The Impact of High-Information Contact by Allen Tough]
* [http://www.atnf.csiro.au/people/rnorris/papers/n163.htm How old is ET? by Ray Norris]
* [http://spacegeek.org/ep2_flash.shtml VIDEO on SETI by Canadian astrophysicist Doctor P]
*Video presentation and tour of the Ohio State University Radio Telescope, "
Big Ear," associated with the Wow! signal: [http://www.youtube.com/watch?v=hg5i0JyYtwE] , [http://www.youtube.com/watch?v=T_vKl1vwg_A] , [http://www.youtube.com/watch?v=3FwiLpwcenI]
Articles and FAQs
* [http://lifeboat.com/ex/shouting.at.the.cosmos SHOUTING AT THE COSMOS...Or How SETI has Taken a Worrisome Turn Into Dangerous Territory] by
* [http://www.setileague.org/editor/clarke.htm Where Is Everybody?] : an
essayby Arthur C. Clarkeon SETI
* [http://history.nasa.gov/garber.pdf "Searching for Good Science: The Cancellation of NASA's SETI Program"] (PDF) – By
Stephen J. Garber, NASA History Office. "Journal of the British Interplanetary Society", Vol. 52, pp. 3-12, 1999. Provides more details on the elimination of SETI funding by the US Congress in 1993.
* [http://www.winlab.rutgers.edu/~crose/cgi-bin/cosmic23.html ET Might Write, Not Radiate]
* Cirkovic, Milan M., and Bradbury, R. J., 200n, " [http://www.anthropic-principle.com/preprints/milan-seti.pdf Galactic Gradients, Postbiological Evolution, and the Apparent Failure of SETI.] "
* [http://SkyandTelescope.com/resources/seti/ "SETI: Searching for Life"] – Article series in
Sky & Telescopemagazine
* [http://www.ccnmag.com/story.php?id=146 IT & SETI: The Role of Computer Technology in the Search for Extraterrestrial Intelligence]
* [http://www.setifaq.org/ SETI@home FAQ for newsgroups alt.sci.seti and sci.astro.seti]
* [http://www.spacedaily.com/reports/Has_Seti_Been_Barking_Up_The_Wrong_Tree_Mostly_999.html Has SETI Been Barking Up the Wrong Tree (Mostly?)]
* [http://science.howstuffworks.com/seti.htm How SETI Works]
* [http://iaaseti.org/rioscale.htm Rio Scale]
* [http://www.spacedaily.com/news/seti-04e.html "First Contact Within 20 Years: Shostak"] – From SpaceDaily.com,
22 July 2004(based on calculations to be published in Acta Astronautica)
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