Active SETI

'Active SETI' was a term as early as 2005, though some decades after the term SETI.{{Cite book |last=A. |first=Vakoch, Douglas |url=http://worldcat.org/oclc/774904900 |title=Expanding Human Presence Beyond the Solar System Through Active SETI : on the Prerequisites for Legal Relations with Extraterrestrial Intelligence |date=2005 |oclc=774904900}} The term METI was coined in 2006 by Russian scientist Alexander Zaitsev, who proposed a subtle distinction between Active SETI and METI:

{{cite arXiv |eprint=physics/0610031 |first1=A. |last1=Zaitsev |title=Messaging to Extra-Terrestrial Intelligence |year=2006}}{{cite news |last=Johnson |first=Steven |date=28 June 2017 |title=Greetings, E.T. (Please Don't Murder Us.) |work=The New York Times |url=https://www.nytimes.com/2017/06/28/magazine/greetings-et-please-dont-murder-us.html |url-status=live |access-date=28 June 2017 |archive-url=https://web.archive.org/web/20170628101941/https://www.nytimes.com/2017/06/28/magazine/greetings-et-please-dont-murder-us.html |archive-date=28 June 2017}}

{{cquote|The science known as SETI deals with searching for messages from aliens. METI deals with the creation and transmission of messages to aliens. Thus, SETI and METI proponents have quite different perspectives. SETI scientists are in a position to address only the local question “does Active SETI make sense?” In other words, would it be reasonable, for SETI success, to transmit with the object of attracting ETI's attention? In contrast to Active SETI, METI pursues not a local, but a more global purpose – to overcome the Great Silence in the Universe, bringing to our extraterrestrial neighbors the long-expected annunciation “You are not alone!”

}}

Concern over METI 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 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".{{Cite journal |date=2006 |title=Ambassador for Earth |journal=Nature |language=en |volume=443 |issue=7112 |pages=606 |doi=10.1038/443606a |pmid=17035960 |bibcode=2006Natur.443..606. |s2cid=39467483 |issn=1476-4687|doi-access=free }} In the same year, astronomer and science fiction author David Brin expressed similar concerns.{{cite web |last=Brin |first=David |date=June 2006 |title=Shouting at the Cosmos |url=http://lifeboat.com/ex/shouting.at.the.cosmos |url-status=live |archive-url=https://web.archive.org/web/20170307223116/http://lifeboat.com/ex/shouting.at.the.cosmos |archive-date=March 7, 2017 |access-date=June 28, 2009 |publisher=Lifeboat Foundation}} In 2013 Brin amended his initial article based on the recent developments in METI.Dabid Brin, [https://www.davidbrin.com/nonfiction/shouldsetitransmit.html Shouting At the Cosmos, 2013 addendum]

In 2010, Douglas A. Vakoch from SETI Institute, addressed concerns about the validity of Active SETI alone as an experimental science by proposing the integration of Active SETI and Passive SETI programs to engage in a clearly articulated, ongoing, and evolving set of experiments to test various versions of the Zoo hypothesis, including specific dates at which a first response to messages sent to particular stars could be expected.

{{cite conference |last1=Vakoch |first1=D. A. |year=2010 |title=Integrating Active and Passive SETI Programs: Prerequisites for Multigenerational Research |url=http://www.lpi.usra.edu/meetings/abscicon2010/pdf/5213.pdf |page=5213 |bibcode=2010LPICo1538.5213V |archive-url=https://web.archive.org/web/20140809184104/http://www.lpi.usra.edu/meetings/abscicon2010/pdf/5213.pdf |archive-date=2014-08-09 |book-title=Proceedings of the Astrobiology Science Conference 2010 |url-status=live}}

On 13 February 2015, scientists including Douglas Vakoch, David Grinspoon, Seth Shostak, and David Brin at an annual meeting of the American Association for the Advancement of Science discussed Active SETI, and whether transmitting a message to possible intelligent extraterrestrials in the Cosmos was a good idea.{{cite news |last=Borenstein |first=Seth |date=13 February 2015 |title=Should We Call the Cosmos Seeking ET? Or Is That Risky? |website=Phys.org |url=https://phys.org/news/2015-02-cosmos-risky.html |url-status=live |access-date=14 February 2015 |archive-url=https://web.archive.org/web/20150214001713/http://phys.org/news/2015-02-cosmos-risky.html |archive-date=14 February 2015}}{{cite news |last=Ghosh |first=Pallab |date=12 February 2015 |title=Scientists in US are urged to seek contact with aliens |work=BBC News |url=https://www.bbc.com/news/science-environment-31442952 |url-status=live |access-date=12 February 2015 |archive-url=https://web.archive.org/web/20150213064250/http://www.bbc.com/news/science-environment-31442952 |archive-date=13 February 2015}} That same week, a statement was released, signed by many in the SETI community including Berkeley SETI Research Center director Andrew Siemion, advocating that a "worldwide scientific, political and humanitarian discussion must occur before any message is sent".{{cite web |author=Various |date=13 February 2015 |title=Regarding Messaging To Extraterrestrial Intelligence (METI) / Active Searches For Extraterrestrial Intelligence (Active SETI) |url=http://setiathome.berkeley.edu/meti_statement_0.html |url-status=dead |archive-url=https://web.archive.org/web/20150214142331/http://setiathome.berkeley.edu/meti_statement_0.html |archive-date=14 February 2015 |access-date=14 February 2015 |work=University of California, Berkeley}}

In July 2015, the Breakthrough Message program was announced. This was an open competition to design a digital message that could be transmitted from Earth to an extraterrestrial civilization, with a US$1,000,000 prize pool. The message was to be "representative of humanity and planet Earth". The program pledged "not to transmit any message until there has been a wide-ranging debate at high levels of science and politics on the risks and rewards of contacting advanced civilizations".{{Cite web |title=Breakthrough Initiatives |url=http://www.breakthroughinitiatives.org/Initiative/2 |url-status=live |archive-url=https://web.archive.org/web/20230116230915/https://breakthroughinitiatives.org/initiative/2 |archive-date=2023-01-16 |access-date=2015-07-24 |website=www.breakthroughinitiatives.org}}

In the paper Rationale for METI,{{Cite journal |last=Zaitsev |first=Alexander L. |date=2011-05-02 |title=Rationale for METI |arxiv=1105.0910 }} transmission of the information into the Cosmos is treated as one of the pressing needs of an advanced civilization. This view is not universally accepted, and it is not agreed with by those who are against the transmission of interstellar radio messages, but at the same time are not against SETI searching. Such duality is called the SETI Paradox.{{Cite journal |last=Zaitsev |first=Alexander |date=2006-11-29 |title=The SETI Paradox |arxiv=physics/0611283 |bibcode=2006physics..11283Z }}{{Cite journal |last=Kerins |first=Eamonn |date=2020-12-22 |title=Mutual Detectability: A Targeted SETI Strategy That Avoids the SETI Paradox |journal=The Astronomical Journal |volume=161 |issue=1 |pages=39 |doi=10.3847/1538-3881/abcc5f |s2cid=222209060 |issn=0004-6256|arxiv=2010.04089 |doi-access=free }}

The lack of an established communications protocol is a challenge for METI. While trying to synthesize and project an Interstellar Radio Message (IRM), the receiving extraterrestrials (ETs) will first encounter a physical phenomenon and, only after that, perceive the information. Initially, a receiving system will detect the radio signal; then the issue of the extraction of the received information and comprehension of the obtained message will arise. Therefore, above all, the constructor of an IRM should be concerned about the ease of signal determination. In other words, the signal should have maximum openness, which is understood here as an antonym of the term security. This branch of signal synthesis is termed anticryptography.

To this end, in 2010, Michael W. Busch created a general-purpose binary language,

{{cite conference

|last1=Busch

|first1=M. W.

|last2=Reddick

|first2=R. M.

|year=2010

|title=Testing SETI Messages Design |book-title=Proceedings of the Astrobiology Science Conference 2010

|url=http://www.lpi.usra.edu/meetings/abscicon2010/pdf/5070.pdf

|arxiv=0911.3976

|bibcode=2010LPICo1538.5070B

|url-status=live

|archive-url=https://web.archive.org/web/20131002054934/http://www.lpi.usra.edu/meetings/abscicon2010/pdf/5070.pdf

|archive-date=2013-10-02

}} later used in the Lone Signal project

{{cite web

|website=Lone Signal |title=Message Encoding – But, Can They Read It?

|url=http://www.lonesignal.com/about/encoding

|archive-url=https://archive.today/20130624203807/https://www.lonesignal.com/about/encoding

|url-status=dead

|archive-date=24 June 2013

|access-date=7 July 2013

}} to transmit crowdsourced messages to extraterrestrial intelligence.

{{cite web

|website=Lone Signal |title=Recent Beams

|url=http://www.lonesignal.com/

|access-date=7 July 2013

|url-status=dead

|archive-url=https://web.archive.org/web/20130707124938/http://www.lonesignal.com/

|archive-date=7 July 2013

}} Busch developed the coding scheme

and provided Rachel M. Reddick with a test message, in a blind test of decryption. Reddick decoded the entire message after approximately twelve hours of work. This was followed by an attempt to extend the syntax used in the Lone Signal hailing message to communicate in a way that, while neither mathematical nor strictly logical, was nonetheless understandable given the prior definition of terms and concepts in the hailing message.

{{cite web

|last1=Chapman

|first1=C. R.

|title=Extending the syntax used by the Lone Signal Active SETI project

|url=http://sites.google.com/site/lonesignalactiveseti/

|website=Lone Signal Active SETI

|archive-url=https://www.webcitation.org/6IqrYp0fX?url=https://sites.google.com/site/lonesignalactiveseti/

|archive-date=13 August 2013

|url-status=live

}}
{{cite web |title=Lone Signal & Jamesburg Earth Station Technologies - Technical Setup |url=https://s3.amazonaws.com/lonesignal-prod-web/Lone+Signal+Technical+Setup_06042013.pdf |url-status=dead |archive-url=https://www.webcitation.org/6Ik4qwRQ5?url=https://s3.amazonaws.com/lonesignal-prod-web/Lone+Signal+Technical+Setup_06042013.pdf |archive-date=2013-08-09

}}

In addition, characteristics of the radio signal, such as wavelength, type of polarization, and modulation are considered. Over galactic distances, the interstellar medium induces some scintillation effects and artificial modulation of electromagnetic signals. This modulation is higher at lower frequencies and is a function of the sky direction. Over large distances, the depth of the modulation can exceed 100%, making any METI signal very difficult to decode.

In METI research, any message must have some redundancy, although the exact amount of redundancy and message formats are still in great dispute. Using ideograms, instead of binary sequence, already offers some improvement against noise resistance. In faxlike transmissions, ideograms are spread on many lines. This increases its resistance against short bursts of noise like radio frequency interference or

interstellar scintillation.

One format approach proposed for interstellar messages was to use the product of two prime numbers to construct an image. Unfortunately, this method works only if all the bits are present. As an example, the message sent by Frank Drake from the Arecibo Observatory in 1974 did not have any feature to support mechanisms to cope with the inevitable noise degradation of the interstellar medium.

Error correction tolerance rates for previous METI messages are 9% (one page) for the 1974 Arecibo Message, 44% (23 separate pages) for the 1999 Evpatoria Message, and 46% (one page, estimated) for the 2003 Evpatoria Message.

The 1999 Cosmic Call transmission was far from being optimal (from a terrestrial viewpoint) as it was essentially a monochromatic signal spiced with supplementary information. Additionally, the message had a very small modulation index overall, a condition not viewed as being optimal for interstellar communication. Over the 370,967 bits (46,371 bytes) sent, some 314,239 were “1” and 56,768 were “0”—5.54 times as many 1's as 0's. Since frequency-shift keying modulation scheme was used, most of the time the signal was on the “0” frequency. In addition, “0” tended to be sent in long stretches, which appeared as white lines in the message.

{{Main|List of interstellar radio messages}}

The below projects have targeted stars between 17 and 69 light-years from the Earth. The exception is the Arecibo message, which targeted globular cluster M13, approximately 24,000 light-years away. The first interstellar message to reach its destination was the Altair (Morimoto - Hirabayashi) Message, which likely reached its target in 1999.{{cite web |title=Earth Set to Receive Alien Reply, Invasion in 2015? |url=https://gizmodo.com/earth-set-to-receive-alien-reply-invasion-in-2015-390304 |website=Gizmodo |date=14 May 2008 |first=Jesus |last=Diaz |language=en-us}}

• The Morse Message (1962){{cite web|url=http://www.lightspeedmagazine.com/nonfiction/you-never-get-a-seventh-chance-to-make-a-first-impression-an-awkward-history-of-our-space-transmissions/ |first=Genevieve |last=Valentine |title=You Never Get a Seventh Chance to Make a First Impression: An Awkward History of Our Space Transmissions |work=Lightspeed Magazine |date=March 2011 |access-date=9 April 2017 |url-status=live |archive-url=https://web.archive.org/web/20160524123653/http://www.lightspeedmagazine.com/nonfiction/you-never-get-a-seventh-chance-to-make-a-first-impression-an-awkward-history-of-our-space-transmissions/ |archive-date=24 May 2016}}
• Arecibo Message (1974)
• Cosmic Call 1 (1999)
• Teen Age Message (2001)
• Cosmic Call 2 (2003)
• Across the Universe (2008)
• [https://web.archive.org/web/20100209202317/http://www.hellofromearth.net/ Hello from Earth] (2009)
• Wow! Reply (2012){{cite web|url=http://www.space.com/17151-alien-wow-signal-response.html |title=Humanity Responds to 'Alien' Wow Signal, 35 Years Later |date=17 August 2012 |work=Space.com |author=Staff |access-date=9 April 2017}}
• Lone Signal (2013)
• A Simple Response to an Elemental Message (2016)

The choice of targets, transmission rate, and encoding may effect how likely a message will be received and interpreted by extraterrestrial intelligence. "Across the Universe" and "A Simple Response to an Elemental Message" were sent to Polaris, which is 431 light years distant from us and whose planetary system, even if it exists, may not be suited for life, because it is a supergiant star, spectral type F7Ib which is only 70 million years old.{{cite journal |author1=Wielen, R. |author2=Jahreiß, H. |author3=Dettbarn, C. |author4=Lenhardt, H. |author5=Schwan, H. |date=2000 |title=Polaris: Astrometric orbit, position, and proper motion |journal=Astronomy and Astrophysics |volume=360 |page=399 |arxiv=astro-ph/0002406 |bibcode=2000A&A...360..399W}} In addition, both transmission rates were very high, about 128 kbit/s, for such moderate transmitter power (about 18 kW){{Explain|date=April 2025}}. The main defect of the "Hello From Earth" is an insufficient scientific and technical justification, since no famous SETI scientist made statements with validation of HFE's design{{Citation needed|date=April 2025}}. As it follows from [https://web.archive.org/web/20100211005300/http://www.hellofromearth.net/gliese581d/links/index.htm]: "After the final message was collected on Monday 24 August 2009, messages were exported as a text file and sent to NASA's Jet Propulsion Laboratory in California, where they were encoded into binary, packaged and tested before transmission", but nobody explained why he hopes that such encoded and packaged text will be understood and conceived by possible extraterrestrials.

Below is a table of messages sent and target/destination stars, ordered chronologically by date of sending:{{cite conference |language=ru |url=http://www.cplire.ru/rus/ra&sr/VAK-2004.html |author=А. Л. Зайцев |title=Передача и поиски разумных сигналов во Вселенной |publisher=Институт радиотехники и электроники РАН |book-title=Пленарный доклад на Всероссийской астрономической конференции ВАК-2004 "Горизонты Вселенной", Москва, МГУ, 7 июня 2004 года |url-status=live |archive-url=https://web.archive.org/web/20120210090149/http://www.cplire.ru/rus/ra%26sr/VAK-2004.html |archive-date=2012-02-10 |access-date=2018-10-01 }}
[{{cite conference |author=A. L. Zaitsev |title=Transmission and retrieval of intelligent signals in the universe |publisher=Institute of Radio Engineering and Electronics RAS |book-title=Keynote Address at the National Astronomical Conference VAK-2004 "Horizons of Universe", Moscow, MSU, 7 June 2004}}]{{cite web |url=http://www.daviddarling.info/encyclopedia/I/IRM.html |title=interstellar radio message (IRM) |website=David Darling |url-status=live |archive-url=https://web.archive.org/web/20080111034116/http://www.daviddarling.info/encyclopedia/I/IRM.html |archive-date=2008-01-11}}{{cite news |url=http://news.bbc.co.uk/2/hi/science/nature/7660449.stm |title=Is anybody listening out there? |work=BBC News |date=9 October 2008 |access-date=11 November 2008}}{{cite web |title=MIR, LENIN, SSSR |url=http://www.cplire.ru/html/ra&sr/irm/MIR-LENIN-SSSR.html |url-status=live |archive-url=https://web.archive.org/web/20090612082250/http://www.cplire.ru/html/ra%26sr/irm/MIR-LENIN-SSSR.html |archive-date=2009-06-12 |quote=Word MIR (it signifies both "peace" and "world" in Russian) was transmitted from the EPR on 19 November 1962, and words LENIN and SSSR (the Russian acronym for the Soviet Union) – on 24 November 1962, respectively were sent to the direction near the star HD131336 in the Libra constellation}}{{cite web|url=https://www.lonesignal.com/targets/1 |archive-url=https://archive.today/20130717080511/https://www.lonesignal.com/targets/1 |url-status=dead |archive-date=17 July 2013 |website=Lone Signal |title=Gliese 526 |access-date=15 July 2013 }}{{cite web|title=Sónar Calling GJ273b - About this project|url=https://www.sonarcalling.com/en/faq/|website=Sónar Calling GJ273b|publisher=Sónar Music Festival|access-date=6 May 2021}}

Whether or not to conduct Active SETI, as well as the tone of any message, is a highly controversial topic.{{Cite journal |last=Shostak |first=S. |date=2014-01-01 |title=Sending Signals Into Space: Is it Really a Bad Idea? |url=https://ui.adsabs.harvard.edu/abs/2014JBIS...67...27S |journal=Journal of the British Interplanetary Society |volume=67 |pages=27–29 |bibcode=2014JBIS...67...27S |issn=0007-084X}}{{Cite journal |last1=Billingham |first1=J |last2=Benford |first2=J |date=2016 |title=Costs and difficulties of interstellar 'Messaging' and the need for international debate on potential risks |url=https://bis-space.com/shop/product/reviewing-meti-a-critical-analysis-of-the-arguments/ |journal=Journal of the British Interplanetary Society |volume=19 |pages=17–23}}{{Cite journal |last=Gertz |first=J |date=2016 |title=Reviewing METI: A critical analysis of the arguments |url=https://bis-space.com/shop/product/reviewing-meti-a-critical-analysis-of-the-arguments/ |journal=Journal of the British Interplanetary Society |volume=69 |pages=31–36|arxiv=1605.05663 |bibcode=2016JBIS...69...31G }}{{Cite journal |last1=Haramia |first1=Chelsea |last2=DeMarines |first2=Julia |date=2019-01-02 |title=The Imperative to Develop an Ethically-Informed METI Analysis |url=https://doi.org/10.1080/14746700.2019.1557800 |journal=Theology and Science |volume=17 |issue=1 |pages=38–48 |doi=10.1080/14746700.2019.1557800 |s2cid=171404637 |issn=1474-6700|url-access=subscription }} Active SETI has primarily been criticized due to the perceived risk of revealing the location of the Earth to alien civilizations, without some process of prior international consultation. That is, Active SETI does not meet the criteria for informed consent in a mass experiment involving human subjects and, potentially, nonhuman sentient subjects.{{Cite journal |last=Traphagan |first=John W. |date=2019-01-02 |title=Active SETI and the Problem of Research Ethics |url=https://doi.org/10.1080/14746700.2019.1557806 |journal=Theology and Science |volume=17 |issue=1 |pages=69–78 |doi=10.1080/14746700.2019.1557806 |s2cid=172004039 |issn=1474-6700|url-access=subscription }}

Active SETI is discussed in terms of the ethics of space policy. Issues include whether to send belligerent versus defensive messages,{{Cite journal |last=Santana |first=Carlos |date=2021-08-01 |title=We Come in Peace? A Rational Approach to METI |url=https://www.sciencedirect.com/science/article/pii/S0265964621000229 |journal=Space Policy |language=en |volume=57 |pages=101430 |doi=10.1016/j.spacepol.2021.101430 |bibcode=2021SpPol..5701430S |issn=0265-9646|url-access=subscription }} cosmopolitanism,{{Cite journal |last1=Wilson |first1=Elspeth M. |last2=Cleland |first2=Carol E. |date=2019-07-03 |title=Should We Call E.T.? An Ethical-Political Analysis of METI |url=https://doi.org/10.1080/14746700.2019.1632551 |journal=Theology and Science |volume=17 |issue=3 |pages=382–394 |doi=10.1080/14746700.2019.1632551 |s2cid=198688714 |issn=1474-6700|url-access=subscription }} communicative burden, consensus, messaging content, proscriptions on premature messaging, responsibility, and shared values,{{Cite journal |last1=Haramia |first1=Chelsea |last2=DeMarines |first2=Julia |date=2019-01-02 |title=The Imperative to Develop an Ethically-Informed METI Analysis |url=https://doi.org/10.1080/14746700.2019.1557800 |journal=Theology and Science |volume=17 |issue=1 |pages=38–48 |doi=10.1080/14746700.2019.1557800 |s2cid=171404637 |issn=1474-6700|url-access=subscription }} with concerns that even if successful, humanity could be reduced to a cargo cult.{{Cite journal |last=Traphagan |first=John W. |date=2018-11-01 |title=Cargo Cults and the Ethics of Active SETI |url=https://www.sciencedirect.com/science/article/pii/S0265964618300201 |journal=Space Policy |language=en |volume=46 |pages=18–22 |doi=10.1016/j.spacepol.2018.04.001 |bibcode=2018SpPol..46...18T |s2cid=158546639 |issn=0265-9646|url-access=subscription }} David Brin also urged for an extensive international consultation before any METI activities and has debunked key rationalizations for active SETI (METI), such as the "barn door" argument (unintentional "leaked signals" were millions-fold weaker than intentional METI signals), ignoring/dismissing the precautionary principle (that requires taking extreme precaution e.g. handling extraterrestrial samples even without any known example of risks), and treating METI as being prayer-like which disregards the issue of informed consent from other people.{{Cite journal |last=Brin |first=David |date=2019-01-02 |title=The "Barn Door" Argument, The Precautionary Principle, and METI as "Prayer" – an Appraisal of the Top Three Rationalizations for "Active SETI" |url=https://doi.org/10.1080/14746700.2018.1557391 |journal=Theology and Science |volume=17 |issue=1 |pages=16–28 |doi=10.1080/14746700.2018.1557391 |s2cid=172101534 |issn=1474-6700|url-access=subscription }} Notable among METI's critics was Stephen Hawking. Hawking, who in his book A Brief History of Time suggests that "alerting" extraterrestrial intelligences to our existence is foolhardy, citing humankind's history of treating its own kind harshly in meetings of civilizations with a significant technology gap, e.g., the extermination of Tasmanian aborigines. He suggested, in view of this history, that we "lay low".{{Cite journal |last=A. Vakoch |first=Douglas |date=2017-04-03 |title=Hawking's fear of an alien invasion may explain the Fermi Paradox |url=http://dx.doi.org/10.1080/14746700.2017.1299380 |journal=Theology and Science |volume=15 |issue=2 |pages=134–138 |doi=10.1080/14746700.2017.1299380 |issn=1474-6700 |s2cid=219627161|url-access=subscription }} Scientist and science fiction author David Brin expressed similar concerns.{{cite web |url=http://lifeboat.com/ex/shouting.at.the.cosmos |title=Shouting at the Cosmos |author=David Brin |date=September 2006 |orig-year=last updated July 2008 |website=Lifeboat Foundation |access-date=9 April 2017 |url-status=live |archive-url=https://web.archive.org/web/20170307223116/http://lifeboat.com/ex/shouting.at.the.cosmos|archive-date=7 March 2017}} Similarly, Liu Cixin's trilogy of novels The Three Body Problem highlights the potential dangers of METI.

However, some scientists consider these fears about the dangers of METI as panic and irrational superstition; Russian and Soviet radio engineer and astronomer Alexander L. Zaitsev has argued against these concerns.{{cite journal |title=Sending and searching for interstellar messages |first=Alexander L. |last=Zaitsev |date=September 2008 |journal=Acta Astronautica |volume=63 |issue=5–6 |pages=614–617 |doi=10.1016/j.actaastro.2008.05.014 |arxiv = 0711.2368 |bibcode = 2008AcAau..63..614Z |s2cid=55638129 }}{{cite journal |url=http://jre.cplire.ru/jre/may08/2/text_e.html |title=Detection Probability of Terrestrial Radio Signals by a Hostile Super-civilization |author=Alexander L. Zaitsev |journal=Journal of Radio Electronics |issue=5 |year=2008 |access-date=9 April 2017 |url-status=live |archive-url=https://web.archive.org/web/20170118154523/http://jre.cplire.ru/jre/may08/2/text_e.html |archive-date=18 January 2017|bibcode=2008arXiv0804.2754Z |arxiv=0804.2754 }} Zaitsev argues that we should consider the risks of not attempting to contact extraterrestrial civilizations, since the knowledge and wisdom an ETI could impart to us would save us from humanity's self-destructive tendencies.{{cite web |url=http://www.setileague.org/editor/meti.htm |title=Making a Case for METI |author1=Alexander Zaitsev |author2=Charles M. Chafer |author3=Richard Braastad |website=SETI League |access-date=9 April 2017 |url-status=live |archive-url=https://web.archive.org/web/20170221134306/http://www.setileague.org/editor/meti.htm|archive-date=21 February 2017 }} Similarly, in a March 2015 essay astronomer Seth Shostak considered the risk and ended by stressing that any danger was hypothetical and that humanity would better off risk contact than "endlessly tremble at the sight of the stars".

Astronomer Jill Tarter also disagrees with Hawking, arguing that aliens developed and long-lived enough to communicate and travel across interstellar distances would have evolved a cooperative and less violent intelligence. She however thinks it is too soon for humans to attempt active SETI and that humans should be more advanced technologically first but keep listening in the meantime.{{cite web |last1=Orwig |first1=Jessica |title=A world leading scientist on the search for extraterrestrials pointed out a flaw in Stephen Hawking's fear of finding intelligent aliens |url=http://www.businessinsider.com/jill-tarter-says-stephen-hawking-is-wrong-about-aliens-2016-1 |url-status=live |archive-url=https://web.archive.org/web/20180221020808/http://www.businessinsider.com/jill-tarter-says-stephen-hawking-is-wrong-about-aliens-2016-1 |archive-date=21 February 2018 |access-date=8 February 2018 |website=Business Insider}}

Image:Pictorial_message_to_potential_eti_at_proxima_centauri.jpg. These messages usually contain information about the location of the solar system in the Milky Way.]]

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{{cite web |url=http://iaaseti.org |title=Overview |website=International Academy of Astronautics – SETI Permanent Committee |access-date=9 April 2017 |url-status=dead |archive-url=https://web.archive.org/web/20170510081227/http://iaaseti.org/|archive-date=10 May 2017 }} adopted in 2007 a new analytical tool, the San Marino Scale.{{cite web |url=http://iaaseti.org/smiscale.htm |archive-url=https://web.archive.org/web/20071208183315/http://iaaseti.org/smiscale.htm |url-status=dead |archive-date=8 December 2007|title=The San Marino Scale |website=International Academy of Astronautics – SETI Permanent Committee |access-date=9 April 2017}} Developed by Prof. Ivan Almar and Prof. H. Paul Shuch, the San Marino 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 created equal, thus each must be evaluated separately before establishing a blanket international policy regarding Active SETI.{{Cite journal |last1=Almár |first1=Iván |last2=Paul Shuch |first2=H. |date=2007-01-01 |title=The San Marino Scale: A new analytical tool for assessing transmission risk |url=https://www.sciencedirect.com/science/article/pii/S0094576506001858 |journal=Acta Astronautica |language=en |volume=60 |issue=1 |pages=57–59 |doi=10.1016/j.actaastro.2006.04.012 |bibcode=2007AcAau..60...57A |issn=0094-5765|url-access=subscription }}

In 2012, Jacob Haqq-Misra, Michael Busch, Sanjoy Som, and Seth Baum argued that while the benefits of radio communication on Earth likely outweigh the potential harms of detection by extraterrestrial watchers, the uncertainty regarding the outcome of contact with extraterrestrial beings creates difficulty in assessing whether or not to engage in long-term and large-scale METI.

{{cite journal

| last1 = Haqq-Misra | first1 = J.

| last2 = Busch | first2 = M. W.

| last3 = Som | first3 = S. M.

| last4 = Baum | first4 = S. D.

| year = 2013

| title = The benefits and harm of transmitting into space

| journal = Space Policy

| volume = 29 | issue = 1

| pages = 40–48

| doi = 10.1016/j.spacepol.2012.11.006

| arxiv = 1207.5540

| bibcode = 2013SpPol..29...40H

| s2cid = 7070311

}}

In 2015, in the context of the Zoo Hypothesis, biologist João Pedro de Magalhães proposed transmitting an invitation message to any extraterrestrial intelligences watching us already and inviting them to respond, arguing this would not put us in any more danger than we are already if the Zoo Hypothesis is correct.

{{cite journal |last=de Magalhaes |first=J. P. |arxiv=1509.03652 |title=A direct communication proposal to test the Zoo Hypothesis |date=2015 |doi=10.1016/j.spacepol.2016.06.001 |volume=38 |journal=Space Policy |pages=22–26|s2cid=119250429 }}

Douglas Vakoch, president of METI, argues that passive SETI itself is already an endorsement of active SETI, since "If we detect a signal from aliens through a SETI program, there's no way to prevent a cacophony of responses from Earth."{{Cite news |author=Hannah Osborne |url=http://www.newsweek.com/advanced-alien-civilization-send-messages-meti-713186 |title=Scientists Have Sent Messages to Advanced Alien Civilizations – And Are Hoping for a Reply in 25 Years |date=2017-11-16 |work=Newsweek |access-date=2017-11-17 |url-status=live |archive-url=https://web.archive.org/web/20171117024323/http://www.newsweek.com/advanced-alien-civilization-send-messages-meti-713186 |archive-date=2017-11-17}}

In the context of potentially detected extraterrestrial activity on Earth, physicist Mark Buchanan argued that humanity needs to determine whether it would be safe or wise to attempt to communicate with extraterrestrials and work on ways to handle such attempts in an organized manner.{{cite news |title=Perspective {{!}} Contacting aliens could end all life on earth. Let's stop trying. |newspaper=Washington Post |url=https://www.washingtonpost.com/outlook/ufo-report-aliens-seti/2021/06/09/1402f6a8-c899-11eb-81b1-34796c7393af_story.html |url-status=live |access-date=23 July 2021 |archive-url=https://web.archive.org/web/20210614200838/https://www.washingtonpost.com/outlook/ufo-report-aliens-seti/2021/06/09/1402f6a8-c899-11eb-81b1-34796c7393af_story.html |archive-date=14 June 2021}}

One proposal for a 10 billion watt interstellar SETI beacon was dismissed by Robert A. Freitas Jr. as being infeasible for a pre-Type I civilization, such as humanity, on the Kardashev scale.

{{cite journal

|last = Freitas

|first = R. A.

|year = 1980

|title = Interstellar Probes: A new approach to SETI

|url = http://www.rfreitas.com/Astro/InterstellarProbesJBIS1980.htm

|journal = Journal of the British Interplanetary Society

|volume = 33

|pages = 95–100

|bibcode = 1980JBIS...33...95F

|url-status = live

|archive-url = https://web.archive.org/web/20160414033819/http://www.rfreitas.com/Astro/InterstellarProbesJBIS1980.htm

|archive-date = 2016-04-14

}} However, this 1980s technical argument assumes omni-directional beacons, which may not be the best way to proceed on many technical grounds. Advances in consumer electronics have made possible transmitters that simultaneously transmit many narrow beams, covering the million or so nearest stars but not the spaces between.

{{cite journal

|last1=Scheffer |first1=L. K.

|year=2005

|title=A scheme for a high-power, low-cost transmitter for deep space applications

|journal=Radio Science

|volume=40 |issue=5 |pages=RS5012

|bibcode = 2005RaSc...40.5012S

|doi=10.1029/2005RS003243

|citeseerx=10.1.1.585.9519

|s2cid=55878347

}} This multibeam approach can reduce the power and cost to levels that are reasonable with early 21st century Earth technology.

Once civilizations have discovered each other's locations, the energy requirements for maintaining contact and exchanging information can be significantly reduced through the use of highly directional transmission technologies. To this end, a 2018 study estimated a 1-2 megawatt infrared laser focused through a 30-45 meter telescope could be seen from about 20,000 light years away.{{cite web|url = https://www.bostonglobe.com/metro/2018/11/08/magnified-laser-from-earth-could-attract-alien-attention-mit-researcher-says/HrbyazamrVaQ1NaBJhdllJ/story.html |title = Magnified laser from Earth could attract alien attention, MIT researcher says|work = Boston Globe|first = Andres|last = Picon|date = 8 November 2018}}

• Communication with extraterrestrial intelligence
• Dark forest hypothesis, the idea that planetary civilizations remain silent to avoid the possibility of contact with potentially aggressive worlds
• Detecting Earth from distant star-based systems
• {{annotated link|METI (Messaging Extraterrestrial Intelligence)}}
• {{annotated link|SETIcon}}
• SETI@home
• Wow! signal

{{Reflist|30em}}

{{Library resources box}}

• [http://www.cplire.ru/html/ra&sr/irm/index.html Interstellar Radio Messages]
• [http://www.activeseti.org ActiveSETI.org] {{Webarchive|url=https://web.archive.org/web/20100930195321/http://www.activeseti.org/ |date=2010-09-30 }}
• [http://active-seti.info/ active-seti.info]
• [http://www.setileague.org/editor/meti.htm Making a Case for METI]
• [https://www.fourmilab.ch/goldberg/setimsg.html Self-Decoding Messages]
• [http://www.starshipnivan.com/blog/?p=65 Should We Shout Into the Darkness?]
• [https://web.archive.org/web/20110605025707/http://www3.sympatico.ca/stephane_dumas/CETI/dutil_dumas.pdf Error Correction Schemes In Active SETI]
• [https://web.archive.org/web/20110724223451/http://activeseti.org/papers/evpatoria07.pdf The Evpatoria Messages]
• [http://www.daviddarling.info/encyclopedia/E/Encounter2001.html Encounter 2001 Message]
• {{cite book|doi=10.1007/978-3-642-13196-7_21|title=Searching for Extraterrestrial Intelligence|pages=399–428|series=The Frontiers Collection|year=2011|last1=Zaitsev|first1=Alexander L.|chapter=METI: Messaging to ExtraTerrestrial Intelligence |isbn=978-3-642-13195-0}}
• [http://www.centauri-dreams.org/?p=17861 The Pros and Cons of METI from Centauri Dreams]
• {{cite journal|doi=10.1016/j.actaastro.2011.05.026|title=Classification of interstellar radio messages|journal=Acta Astronautica|volume=78|pages=16–19|year=2012|last1=Zaitsev|first1=Alexander|bibcode=2012AcAau..78...16Z}}
• [https://web.archive.org/web/20130707124938/http://www.lonesignal.com/ Lone Signal]

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