S.E.T.I.: The Search for Extraterrestrial Intelligence

This topic submitted by Dustin Gebhard ( Dusty34118@aol.com) at 10:05 AM on 6/24/02.

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The search for the answer to the age-old question ñAre we alone in the universe?î no doubt began with the dawn of man. It wasnÍt until the early twentieth century that man started to apply his knowledge of electromagnetic frequency to this question. Radio pioneers such as Heinrich Hertz, Nikola Tesla and Guglielmo Marconi were the first to attempt to use radio waves for ñinterplanetary communicationî, little did they know that there was no one within the planetary system with which to communicate. Ignorant of this fact, Marconi caused a great public stir in 1919 when he tried to determine if the odd radio signals he was receiving had originated on Mars. Elmer Sperry, head of Sperry Gyroscope Company, wanted to set up a massive array of searchlights to send a beacon to Mars. Even Albert Einstein believed that light rays may be an easily controlled method for extraterrestrial communication . Today, many scientists believe radio waves to be the best or only chance we have at interstellar communication.Radio waves are a form of electromagnetic radiation and travel at the speed of light, 300,000 km per second, the fastest velocity possible. To give an idea of how great the distances involved in this study are; imagine it takes four years traveling at the speed of light to reach the star closest to the Earth, Proxima Centauri, and almost all other stars are much farther away. Besides their speed, radio waves are the optimal band of the electromagnetic (EM) spectrum for interstellar communication for three other reasons: 1. The radio wavelength is relatively free of the absorption and noise that clutters the other areas of the spectrum. 2. Radio, visible light and near infrared are the only EM frequencies that are able to penetrate the EarthÍs atmosphere, and radio waves are the least easily absorbed by interstellar gas and dust. 3. Stars are usually relatively quiet in the radio wavelength making radio a natural candidate for a deliberate beacon from an advanced, intelligent civilization . There is also a specific frequency that has been favored by SETI researchers, this is the frequency close to the ñ21 cm lineî, also known as the ñwater holeî. This frequency is significant for two reasons: 1. This is an important frequency in radio astronomy because it falls between the frequencies of Hydrogen(around 1,420 megahertz), the most common element in the universe, and Hydroxyl, the components of life sustaining water (alien engineers may recognize his and choose it as a logical hailing frequency). 2. Because of this, all radio transmissions are prohibited on and off Earth by an international agreement, reducing the amount of terrestrial interference in this part of the spectrum . So astronomers have an idea of where to focus their search, but that doesnÍt make their task any less daunting. The radio-telescopic search for extraterrestrial life has often and appropriately been compared to searching for a needle in a haystack.
The modern search for extraterrestrial intelligence began in 1961 with the Drake equation which launched the SETI movement. In April of 1960 a radio astronomer named Frank Drake became the first scientist to start a systematic search for intelligent signals in space. Drake used a twenty-five meter dish of the National Radio Astronomy Observatory in Green Bank, WV. He scanned frequencies close to the 21 cm wavelength of two nearby, sun-like stars: Epsilon Eriduni and Tau Ceti for six hours a day from April to July. The project was cheap and unsuccessful . After this failure, Drake came up with his famous equation that would offer the potential to calculate the number of radio-emitting civilizations in the universe:
N = R x fp x ne x fl x fi x fc x L
Using this equation, it can be calculated that theoretically there should be one radio-emitting civilization right now per four million stars. Drake is remembered as saying: ñI could see no reason to think that human kind was the only example of civilization, unique in the universe.î Regardless of this somewhat optimistic figure, forty years of SETI research have failed to discover any such civilizations .
Currently there are several large-scale searches for extraterrestrial intelligence scanning the skies for both radio and laser transmissions from other civilizations. Radio astronomer Alan M. MacRobert said in Sky and Telescope that ñRadio searches have been going on the longest, and the theory behind them is well established: Radio searches hunt through the microwave spectrum for any extremely narrowband (single-frequency) signal coming from outside the solar system. According to conventional wisdom this is the kind of broadcast that has the best chance of being detected across interstellar distances...the band frequencies from about 0.5 to 60 gigahertz has the least natural background interference in space (our own atmosphere tends to limit us to frequencies below around 12 gigahertz).î Because of the size of our galaxy, the immense distances between stars and the width of the microwave spectrum, the task of detecting a signal from an advanced alien civilization is very difficult. The only kind of transmission that we currently have much chance of detecting is a very strong signal deliberately sent out, or an alien ñbeaconî .
There are currently several SETI projects in operation today: 1. Project Phoenix: Project Phoenix is the continuation of a failed SETI search designed by NASA. Congress canceled the search in 1993, after which the privately funded SETI Institute secured the equipment to continue the targeted search that already had 58 million government dollars invested in it. Project Phoenix is run by the SETI institute of Mountain View, Ca and is a ñtargeted searchî, performing sensitive examinations of relatively few targets (1,000 mostly sun-like stars, closer than 200 light-years and older than three billion years, as well as all other closest stars regardless of their type). The movie ñContactî was loosely based on this project. project Phoenix operates out of a truck trailer filled with custom-built equipment and powerful computers. This ñmoving laboratoryî travels to large radio telescopes all over the world to monitor its chosen stars. The project is capable of scanning more that two billion channels between 1.2 and 30 gigahertz with a ñrazor-thinî resolution of 0.7 hertz per channel. Any signal this narrow is undoubtedly artificial, the narrowest microwave frequency found in nature is about 300 hertz wide (produced by an interstellar maser). In 1998 the project was moved to the Arecibo radio telescope in Puerto Rico, where it remains now. The 305 meter Arecibo dish is the most sensitive radio telescope in the world. In addition to Project Phoenix, Other SETI projects such as SERENDIP 4, and SERENDIPÍs extension, SETI@home have made use of the dish.
Today the program utilizes the Arecibo dish by running twenty daily sessions of about twelve hours each every six months until the year 2003 (when the project will have to apply for more telescope time). Project Phoenix has a very narrow effective listening beam, only about ten arc seconds wide, this is too narrow to include any significant number of background stars around the one being targeted.
Strengths: Close stars are examined with much greater depth than they are with any other SETI program. Project is capable of scanning a wider fraction of the microwave window, about 2 gigahertz worth, which is more than any current SETI program. The program is built around reinforced methods for detecting false alarms, it is capable of simultaneous observation with the 76 meter Lowell Bank radio dish in England which allows it to chase and confirm a signal in real time.
Weaknesses: Project only looks at a few stars out of the billions that are in our galaxy. The program is only actively surveying about five percent of the time each year.

2. Project SERENDIP: Search for Extraterrestrial Radio Emission from Nearby Developed Intelligent Populations. Getting adequate radio telescope time has always been one of the biggest problems for SETI researches, (as was seen in the film ñContactî). Project SERENDIP has found a way to avoid this problem by implementing a technique called ñpiggybackingî. The idea of ñpiggybackingî an extra receiver onto an other-wise engaged radio telescope was conceived about twenty-five years ago by SETI researchers at the University of California at Berkeley. This 200 billion-instructions-per-second-supercomputer was installed June 11 of 1997. The current version of SERENDIP, SERENDIP 4, is suspended high above the Arecibo dish with multiple other receivers. The program scans for narrowband signals wherever the dish is aimed by its controlling radio astronomers involved in other research. Theoretically, the program can collect data all year-round, but in practice, data is only collected seventy-five percent of the time. Since installation, SERENDIP 4 has been listening to 168 million radio channels simultaneously, each 0.6 hertz wide every 1.7 seconds. This comes out to a total band of 100 megahertz wide focused on the ñwater holeî aka. the 21 cm wavelength (Hydrogen emission frequency of 1,420 megahertz). The program receives raw data at a rate of one megabyte every four minutes. Data collected is transferred via internet from the Arecibo dish to the SERENDIP lab at UC Berkeley. There it is run through a series of algorithms designed to reject radio frequency interference and detect signals that have the possibility of being both artificial and extraterrestrial . Given enough time, SERENDIP 4 should be able to scan most of the area in the sky between the declinations 0 degrees to 38 degrees repeatedly, about thirty percent of the sky. Because the Arecibo dish points directly up, it cannot see any farther North or south of these declinations. Interesting signals that pass preliminary false alarm tests are kept on file and scheduled for dedicated follow-up observations. Project scientist Dan Werthimer reports that preliminary analysis of the SERENDIP 4 data collected so far has turned up no obviously exciting signals, but full analysis of data will take more time . SERENDIP 4Ís ancestor, SERENDIP 1, was started in 1979 at UC BerkeleyÍs Hat Creek Observatory. The program ran on an archaic , one hundred channel spectrum analyzer.

SERENDIP 4 instruments are used by the Australian SETI group at the Parkes telescope, the Italian SETI group at the Medicina Observatory, and OSU is using a four million channel version of the program for SETI research at the OSU radio Observatory. In the spring of ï98, the SERENDIP project was honored by the Smithsonian by winning the 1998 Science Innovation Award.
Strengths: Project SERENDIP 4 uses the worldÍs largest radio telescope to scan a fair portion of the celestial sphere. It samples many billions of Milky Way stars and many thousands of background galaxies. Although no one star gets as deep a scrutiny as Project Phoenix provides, a much greater number of stars can be scanned.
Weaknesses: Project SERENDIP has no real time follow-up, so the weak signals from beyond several 100 light-years may fade in and out of audibility before they can be fully analyzed. (A result of thin gas between stars causing stellar scintillation).

3. SETI@Home: SETI@ home is an extension program of project SERENDIP. It was created in 1998 by David Gedye (a Seattle Computer Scientist) who was looking to find a solution for the problems plaguing project SERENDIP. With massive amounts of data and not enough computing power, Gedye suggested creating a program that allowed volunteers to use their home PC to more deeply analyze the SETI radio data. This 790 kb program works by installing itself as your computers default screensaver, when the computer is not in use, the program fetches a 350 kb file of data, a ñwork unitî, recorded by the SERENDIP receiver. The program then analyzes the data (for about six to sixty hours depending on setup) before returning the results and picking up another work unit . As of December 6, 2001 (two years and six months into the project), 3.4 million people from nearly every country in the world had downloaded the program. SETI@home analyzes only a narrow 2.5 megahertz of SERENDIPÍs 100 mHz wide band, but within this 2.5 mHz band sensitivity is increased ten fold ( thirty times more planets and stars get searched). SETI@home qualifies as one of the worldÍs most powerful supercomputers, and Berkeley lab has yet to use its full potential.
Strengths: SETI@home performs the deepest wide-sky survey of the 21 cm frequency that has ever been done, and that is possible with todayÍs equipment. The program has also help to expand public understanding of SETI issues.
Weaknesses: Program only provides a 21 cm frequency survey, and as with the rest of SERENDIP, there is no real time follow-up (result of piggybacking).

4. Optical SETI: The premise for Optical SETI was suggested in 1961 by laser inventor Charles H. Townes. Stuart Kingsley, who has long believed laser technology to be an attractive substitute for interstellar radio waves, started COSET (Columbus Optical SETI). Kingsley was the first astronomer to perform a targeted search for extraterrestrial laser signals. He searched hundreds of stars for both narrowbeam laser signals and for extremely brief pulsed signals at a visual wavelength using just a ten inch amateur telescope and commercial equipment. The idea of Extraterrestrial laser signals is so appealing because a laser hardly more powerful that what we have today could be capable of directing a short burst of beacon signals to a million stars a day. These signals could be detected across 1,000 light-years by todayÍs optical telescopes. Such a brief pulsed signal would be very clear and obviously artificial. This type of signal could be detected by scanning a single, wide-frequency channel spanning much of the visible or infrared spectrum. Optical signals arenÍt vulnerable to interstellar scintillation, so they donÍt fade in and out like radio signals. This process is also much less complicated than scanning billions of narrow channels for a continuous radio signal.
(Also worth mentioning are projects Southern SETI and project BETA, both of which greatly contribute to the ongoing search for alien life.)

DATA: Collecting the data is only half of the work that goes into SETI projects, radio and laser data must be analyzed to determine the origin and validity of received signals.

1.
An Anomalous SETI signal. This is an Astronomy pic of the day from March 30, 1999 from the SETI league. This data is an example of a potential alien signal. The bright colors on blue background indicate that an anomalous signal was received on Earth. This signal was received by the 76 m Lowell Radio telescope in England. The signal turned out to be characteristic of a man-made satellite in low Earth orbit .

2.
This is a snapshot of data being received by the Southern SERENDIP project using the Parkes radio telescope gathered March 2, 2000. Southern SERENDIP takes the same data being received by the Multibeam Project (Australian all sky and pulsar survey) and examines it in a higher resolution. The signal is scanned for a very distinctive ñcarrier signalî typical of the type carrying artificially created information via radio waves. The Multibeam Project uses a special receiver that views the sky with fourteen closely packed ñradio eyesî. the Southern SERENDIP uses two of these eyes, splitting the incoming data into two sets of seven boards as a way of filtering out EarthÍs radio interference. If a signal of extraterrestrial origin were to be received, it would only be in one of the eyes or boards and oriented diagonally, appearing to postbox through the frequency (result of planetsÍ rotation, alien and Earth) .

3.
The most famous of all SETI candidate signals is the ñWOWî signal. When received and analyzed, the signal seemed to fit all characteristics anticipated for communications of intelligent extraterrestrial origin. The signal was received to the OSU radio astronomy SETI lab on August 15, 1977, and the scientist analyzing it was so amazed at the radio wave frequencies recorded that he wrote ñWOWî in the margin. This signal, which has even been mentioned on ñThe X-Filesî, is significant for four reasons: 1. The signal fits the rise and fall pattern of an antenna perfectly. 2. The source of the signal was concluded to be beyond the distance of the moon, and not a satellite. 3. The frequency of the signal is very near the 1,420 mHz Hydrogen line (water hole/ 21 cm frequency) which is prohibited for all earthly radio transmissions. 4. The signal was determined to be moving with the background stars by analyzing its doppler shift . Unfortunately, after twenty-six years and over one hundred follow-up studies, the signal has yet to be re-discovered or explained.
SETI research is becoming more popular all over the world, countries like China and Japan already have plans for future SETI designated radio telescopes. The SETI Institute is building a ñNew Search Systemî (NSS) to replace the present receiver system at Arecibo. The system, which should be ready by late 2002, will be capable of listening to one hundred mHz of narrowband radio channels at once, versus the twenty mHz it is handling now.
The SETI project is still very much alive and flourishing thanks to the support of private organizations, even after government shut down. With perseverance, the challenge of finding a needle in a haystack may be proven possible, and the discovery of extraterrestrial intelligent life may one day be a reality. The universe is vast and consequently the amount of information gathering power, computing power, man power and determination required to succeed in such a task is equally vast.

Works Cited:
1. http://www.setileague.org/photos/hits.htm#Unsworth
2. http://apod.gsfc.nasa.gov/apod/image/9903/anoml_setileague_big.gif
3. http://seti.uws.edu.au/main/livedata.htm
4. http://www.skypub.com/news/special/SETI_today.html, SETI: Searches Today, MacRobert, Alan M.
5. http://www.skypub.com/news/special/seti_today.html
6. http://seti.ssl.berkely.edu/SERENDIP/SERENDIP.html
7. http://www.skypub.com/news/special/9812SETI_aliens.html, The Chance of Finding Aliens, Schilling, Govert and MacRobert, Alan M.
8. ñSearching For Good Science: The Cancellation of NASAÍs SETI Programî, Garber, Stephen J., Journal of the British Interplanetary Society ,vol.52, pp3-12, 1999

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