Messages From Extraterrestrial Intelligence

The search for extraterrestrial intelligence (usually shortened as SETI) is an expression that refers to the diverse efforts and scientific projects intended to detect extraterrestrial signals, or any evidence of intelligent life beyond Earth.

Researchers use methods such as monitoring electromagnetic radiation, searching for optical signals, and investigating potential extraterrestrial artifacts for any signs of transmission from civilizations present on other planets. Some initiatives have also attempted to send messages to hypothetical alien civilizations, such as NASA's Golden Record.

Modern SETI research began in the early 20th century after the advent of radio, expanding with projects like Project Ozma, the Wow! signal detection, and the Breakthrough Listen initiative; a $100 million, 10-year attempt to detect signals from nearby stars, announced in 2015 by Stephen Hawking and Yuri Milner. Since the 1980s, international efforts have been ongoing, with community led projects such as SETI@home and Project Argus, engaging in analyzing data. While SETI remains a respected scientific field, it often gets compared to conspiracy theory, UFO research, bringing unwarranted skepticism from the public, despite its reliance on rigorous scientific methods and verifiable data and research. Similar studies on Unidentified Aerial Phenomena (UAP) such as the Avi Loeb's Galileo Project have brought further attention to SETI research.

Despite decades of searching, no confirmed evidence of alien intelligence has been found, bringing criticism onto SETI for being 'overly hopeful'. Critics argue that SETI is speculative and unfalsifiable, while supporters see it as a crucial step in addressing the Fermi Paradox and understanding extraterrestrial technosignature.

History

Early work

There have been many earlier searches for extraterrestrial intelligence within the Solar System. In 1896, Nikola Tesla suggested that an extreme version of his wireless electrical transmission system could be used to contact beings on Mars. In 1899, while conducting experiments at his Colorado Springs experimental station, he thought he had detected a signal from Mars since an odd repetitive static signal seemed to cut off when Mars set in the night sky. Analysis of Tesla's research has led to a range of explanations including:
*Tesla simply misunderstood the new technology he was working with,
*that he may have been observing signals from Marconi's European radio experiments,
*and even speculation that he could have picked up naturally occurring radio noise caused by a moon of Jupiter ( Io) moving through the magnetosphere of Jupiter.

In the early 1900s, Guglielmo Marconi, Lord Kelvin and David Peck Todd also stated their belief that radio could be used to contact Martians, 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 at any time in the century before or the next 80 years. In the United States, a "National Radio Silence Day" was promoted during a 36-hour period from August 21–23, with all radios quiet for five minutes on the hour, every hour. At the United States Naval Observatory, a radio receiver was lifted above the ground in a dirigible tuned to a wavelength between 8 and 9 km, using a "radio-camera" developed by Amherst College and Charles Francis Jenkins. The program was led by David Peck Todd with the military assistance of Admiral Edward W. Eberle (Chief of Naval Operations), with William F. Friedman (chief cryptographer of the United States Army), assigned to translate any potential Martian messages.

A 1959 paper by Philip Morrison and Giuseppe Cocconi first pointed out the possibility of searching the microwave spectrum. It proposed frequencies and a set of initial targets.

In 1960, Cornell University astronomer Frank Drake performed the first modern SETI experiment, named "Project Ozma" after the Queen of Oz in L. Frank Baum's fantasy books. Drake used a radio telescope in diameter at Green Bank, West Virginia, to examine the stars Tau Ceti and Epsilon Eridani near the 1.420 gigahertz marker frequency, a region of the radio spectrum dubbed the " water hole" due to its proximity to the hydrogen and hydroxyl radical spectral lines. A 400 kilohertz band around the marker frequency was scanned using a single-channel receiver with a bandwidth of 100 hertz. He found nothing of interest.

Soviet scientists 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. Soviet astronomer Iosif Shklovsky wrote the pioneering book in the field, ''Universe, Life, Intelligence'' (1962), which was expanded upon by American astronomer Carl Sagan as the best-selling book ''Intelligent Life in the Universe'' (1966).

In the March 1955 issue of ''Scientific American'', John D. Kraus described an idea to scan the cosmos for natural radio signals using a flat-plane radio telescope equipped with a parabolic reflector. Within two years, his concept was approved for construction by Ohio State University. With a total of US$71,000 ()
in grants from the National Science Foundation, construction began on an plot in Delaware, Ohio. This Ohio State University Radio Observatory telescope was called "Big Ear". Later, it began the world's first continuous SETI program, called the Ohio State University SETI program.

In 1971, NASA funded a SETI study that involved Drake, Barney Oliver of Hewlett-Packard Laboratories, 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 US$10 billion. Cyclops was not built, but the report formed the basis of much SETI work that followed.

The Ohio State 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 exclamation "Wow!" in the margin. Dubbed the ''Wow! signal'', it is considered by some to be the best candidate for a radio signal from an artificial, extraterrestrial source ever discovered, but it has not been detected again in several additional searches.

On 24 May 2023, a test extraterrestrial signal, in the form of a "coded radio signal from Mars", was transmitted to radio telescopes on Earth, according to a report in ''The New York Times''.

Sentinel, META, and BETA

In 1980, Carl Sagan, Bruce Murray, and Louis Friedman founded the U.S. Planetary Society, partly as a vehicle for SETI studies.

In the early 1980s, Harvard University physicist Paul Horowitz took 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 autocorrelation 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 Harvard/Smithsonian radio telescope at Oak Ridge Observatory in Harvard, Massachusetts. This project was named "Sentinel" and continued into 1985.

Even 131,000 channels were not 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. A second such effort, META II, was begun in Argentina in 1990, to search the southern sky, receiving an equipment upgrade in 1996–1997.

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 (FFT) engines, each capable of performing a 2²²-point complex FFTs in two seconds, and 21 general-purpose personal computers equipped with custom digital 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 spectrum 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's sidereal rotation rate. A third receiver observed the horizon to veto signals of obvious terrestrial origin. On March 23, 1999, the 26-meter radio telescope 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 1978, the NASA SETI program had been heavily criticized by Senator William Proxmire, and funding for SETI research was removed from the NASA budget by Congress in 1981; however, funding was restored in 1982, after Carl Sagan talked with Proxmire and convinced him of the program's value. 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, as well as the radio telescope of the National Radio Astronomy Observatory at Green Bank, West Virginia and the radio telescope at the Arecibo Observatory 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 United States Congress, where the program met opposition and canceled one year after its start. SETI advocates continued without government funding, and in 1995 the nonprofit SETI Institute of Mountain View, California resurrected the MOP program under the name of Project "Phoenix", backed by private sources of funding. In 2012 it cost around $2 million per year to maintain SETI research at the SETI Institute and around 10 times that to support different SETI activities globally. Project Phoenix, under the direction of Jill Tarter, was a continuation of the targeted search program from MOP and studied roughly 1,000 nearby Sun-like stars until approximately 2015. From 1995 through March 2004, Phoenix conducted observations at the Parkes radio telescope in Australia, the radio telescope of the National Radio Astronomy Observatory in Green Bank, West Virginia, and the radio telescope at 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.

Ongoing radio searches

Many radio frequencies penetrate Earth's atmosphere quite well, and this led to radio telescopes that investigate the cosmos using large radio antennas. Furthermore, human endeavors emit considerable electromagnetic radiation as a byproduct of communications such as television and radio. These signals would be easy to recognize as artificial due to their repetitive nature and narrow bandwidths. Earth has been sending radio waves from broadcasts into space for over 100 years. These signals have reached over 1,000 stars, most notably Vega, Aldebaran, Barnard's Star, Sirius, and Proxima Centauri. If intelligent alien life exists on any planet orbiting these nearby stars, these signals could be heard and deciphered, even though some of the signal is garbled by the Earth's ionosphere.

Many international radio telescopes are currently being used for radio SETI searches, including the Low Frequency Array (LOFAR) in Europe, the Murchison Widefield Array (MWA) in Australia, and the Lovell Telescope in the United Kingdom.

Allen Telescope Array

The SETI Institute collaborated with the Radio Astronomy Laboratory at the Berkeley SETI Research Center. Its sensitivity is designed to be equivalent to a single large dish more than 100 meters in diameter, if fully completed. Presently, the array has 42 operational dishes at the Hat Creek Radio Observatory in rural northern California.

The full array (ATA-350) is planned to consist of 350 or more offset- Gregorian radio dishes, each in diameter. These dishes are the largest producible with commercially available satellite television dish technology. The ATA was planned for a 2007 completion date, at a cost of US$25 million. The SETI Institute provided money for building the ATA while University of California, Berkeley designed the telescope and provided operational funding. The first portion of the array (ATA-42) became operational in October 2007 with 42 antennas. The DSP system planned for ATA-350 is extremely ambitious. Completion of the full 350 element array will depend on funding and the technical results from ATA-42.

ATA-42 (ATA) is designed to allow multiple observers simultaneous access to the interferometer output at the same time. Typically, the ATA snapshot imager (used for astronomical surveys and SETI) is run in parallel with a beamforming system (used primarily for SETI). ATA also supports observations in multiple synthesized pencil beams at once, through a technique known as "multibeaming". Multibeaming provides an effective filter for identifying false positives in SETI, since a very distant transmitter must appear at only one point on the sky.

SETI Institute's Center for SETI Research (CSR) uses ATA in the search for extraterrestrial intelligence, observing 12 hours a day, 7 days a week. From 2007 to 2015, ATA identified hundreds of millions of technological signals. So far, all these signals have been assigned the status of noise or radio frequency interference because a) they appear to be generated by satellites or Earth-based transmitters, or b) they disappeared before the threshold time limit of ~1 hour. Researchers in CSR are working on ways to reduce the threshold time limit, and to expand ATA's capabilities for detection of signals that may have embedded messages.

Berkeley astronomers used the ATA to pursue several science topics, some of which might have transient SETI signals, until 2011, when the collaboration between the University of California, Berkeley and the SETI Institute was terminated.

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

In April 2011, the ATA entered an 8-month "hibernation" due to funding shortfalls. Regular operation of the ATA resumed on December 5, 2011.

In 2012, the ATA was revitalized with a $3.6 million donation by Franklin Antonio, co-founder and Chief Scientist of QUALCOMM Incorporated. This gift supported upgrades of all the receivers on the ATA dishes to have (2× to 10× over the range 1–8 GHz) greater sensitivity than before and supporting observations over a wider frequency range from 1–18 GHz, though initially the radio frequency electronics only go to 12 GHz. As of July 2013, the first of these receivers was installed and proven, with full installation on all 42 antennas being expected for June 2017. ATA is well suited to the search for extraterrestrial intelligence (SETI) and to discovery of astronomical radio sources, such as heretofore unexplained non-repeating, possibly extragalactic, pulses known as fast radio bursts or FRBs.

SERENDIP

SERENDIP (Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations) is a SETI program launched in 1979 by the Berkeley SETI Research Center in 2014–2015.

Breakthrough Listen

''Breakthrough Listen'' is a ten-year initiative with $100 million funding begun in July 2015 to actively search for intelligent extraterrestrial communications in the universe, in a substantially expanded way, using resources that had not previously been extensively used for the purpose. It has been described as the most comprehensive search for alien communications to date. The science program for Breakthrough Listen is based at Berkeley SETI Research Center

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