Editing Drake equation (section)

==History==
In September 1959, physicists [[Giuseppe Cocconi]] and [[Philip Morrison]] published an article in the journal ''[[Nature (journal)|Nature]]'' with the provocative title "Searching for Interstellar Communications".<ref name="Cocconi 1959">
{{cite journal
 |last1=Cocconi |first1=G.
 |last2=Morisson |first2=P.
 |year=1959
 |title=Searching for Interstellar Communications
 |url=http://www.iaragroup.org/_OLD/seti/pdf_IARA/cocconi.pdf |archive-url=https://web.archive.org/web/20110728025232/http://www.iaragroup.org/_OLD/seti/pdf_IARA/cocconi.pdf |archive-date=2011-07-28 |url-status=live
 |journal=[[Nature (journal)|Nature]]
 |volume=184 |issue=4690 |pages=844–846
 |access-date=2013-04-10
 |bibcode=1959Natur.184..844C
 |doi=10.1038/184844a0
|s2cid=4220318
 }}</ref><ref name="history">{{cite web
 |last1=Schilling
 |first1=G.
 |last2=MacRobert
 |first2=A. M.
 |year=2013
 |title=The Chance of Finding Aliens
 |url=https://skyandtelescope.org/astronomy-news/the-chance-of-finding-aliens/
 |work=[[Sky & Telescope]]
 |access-date=2013-04-10
 |archive-url=https://web.archive.org/web/20130214073858/http://www.skyandtelescope.com/resources/seti/3304541.html
 |archive-date=14 February 2013
 |url-status=dead
 }}</ref> Cocconi and Morrison argued that [[radio telescope]]s had become sensitive enough to pick up transmissions that might be broadcast into space by civilizations orbiting other stars. Such messages, they suggested, might be transmitted at a [[wavelength]] of 21&nbsp;cm (1,420.4&nbsp;[[megahertz|MHz]]). This is the wavelength of radio emission by neutral [[hydrogen]], the most common element in the universe, and they reasoned that other intelligences might see this as a logical landmark in the [[radio spectrum]].

Two months later, Harvard University astronomy professor [[Harlow Shapley]] speculated on the number of inhabited planets in the universe, saying "The universe has 10 million, million, million suns (10 followed by 18 zeros) similar to our own. One in a million has planets around it. Only one in a million million has the right combination of chemicals, temperature, water, days and nights to support planetary life as we know it. This calculation arrives at the estimated figure of 100 million worlds where life has been forged by evolution."<ref name="SydneyMorningHerald">
{{cite news
 |last=newspaper |first=staff
 |date=8 November 1959
 |title=Life On Other Planets?
 |url=https://news.google.com/newspapers?nid=1301&dat=19591108&id=s39WAAAAIBAJ&pg=2212,2112869&hl=en
 |work=[[Sydney Morning Herald]]
 |access-date=2015-10-02
}}</ref>

Seven months after Cocconi and Morrison published their article, Drake began [[search for extraterrestrial intelligence|searching for extraterrestrial intelligence]] in an experiment called [[Project Ozma]]. It was the first systematic search for signals from communicative extraterrestrial civilizations. Using the {{convert|85|foot|abbr=on}} dish of the [[Green Bank Observatory|National Radio Astronomy Observatory, Green Bank]] in [[Green Bank, West Virginia]], Drake monitored two nearby Sun-like stars: [[Epsilon Eridani]] and [[Tau Ceti]], slowly scanning frequencies close to the 21&nbsp;cm wavelength for six hours per day from April to July 1960.<ref name="history"/> The project was well designed, inexpensive, and simple by today's standards. It detected no signals.

Soon thereafter, Drake hosted the first search for extraterrestrial intelligence conference on detecting their radio signals. The meeting was held at the Green Bank facility in 1961. The equation that bears Drake's name arose out of his preparations for the meeting.<ref name="Astrobiology Magazine">{{cite web | url=http://www.astrobio.net/alien-life/the-drake-equation-revisited-part-i/ | title=The Drake Equation Revisited: Part I | work=[[Astrobiology Magazine]] | date=29 September 2003 | access-date=20 May 2017 |archive-url=https://web.archive.org/web/20210225062139/http://www.astrobio.net/alien-life/the-drake-equation-revisited-part-i/ |archive-date=2021-02-25 |url-status=usurped}}</ref>

{{blockquote|As I planned the meeting, I realized a few day[s] ahead of time we needed an agenda. And so I wrote down all the things you needed to know to predict how hard it's going to be to detect extraterrestrial life. And looking at them it became pretty evident that if you multiplied all these together, you got a number, N, which is the number of detectable civilizations in our galaxy. This was aimed at the radio search, and not to search for primordial or primitive life forms.|Frank Drake}}

The ten attendees were conference organizer J. Peter Pearman, Frank Drake, [[Philip Morrison]], businessman and radio amateur Dana Atchley, chemist [[Melvin Calvin]], astronomer [[Su-Shu Huang]], neuroscientist [[John C. Lilly]], inventor [[Barney Oliver]], astronomer [[Carl Sagan]], and radio-astronomer [[Otto Struve]].<ref name="Wende">
{{cite news
 |last=Zaun |first=H.
 |date=1 November 2011
 |title=Es war wie eine 180-Grad-Wende von diesem peinlichen Geheimnis!
 |trans-title=It was like a 180 degree turn from this embarrassing secret
 |url=http://www.heise.de/tp/artikel/35/35756/1.html
 |work=[[Telepolis]]
 |language=de
 |access-date=2013-08-13
}}</ref> These participants called themselves "The Order of the Dolphin" (because of Lilly's work on [[dolphin communication]]), and commemorated their first meeting with a plaque at the observatory hall.<ref>
{{cite web
 |title=Drake Equation Plaque
 |url=http://www.setileague.org/photos/miscpix/drakeqn.jpg
 |access-date=2013-08-13
}}</ref><ref>{{cite encyclopedia |title=Green Bank conference (1961) |encyclopedia=[[The Encyclopedia of Science]] |url=https://www.daviddarling.info/encyclopedia/G/GreenBank.html#Green_Bank_SETI_conference |access-date=13 August 2013 |last=Darling |first=D. J. |archive-url=https://web.archive.org/web/20240221024436/https://www.daviddarling.info/encyclopedia/G/GreenBank.html#Green_Bank_SETI_conference |archive-date=21 Feb 2024 |url-status=dead |df=dmy-all}}</ref>