View source for SETI@home

{{short description|BOINC based volunteer computing project searching for signs of extraterrestrial intelligence}}
{{Multiple issues|
{{Original research|date=December 2023}}
{{More footnotes needed|date=December 2023}}
}}
{{Use mdy dates|date=July 2019}}
{{Infobox distributed computing project
| logo                   = SETI@home logo.png
| developer              = [[University of California, Berkeley]]
| released               = {{start date |1999|05|17}}
| latest release version  = SETI@home v8：8.00
| latest release date     = {{start date and age|2015|12|30}}
SETI@home v8 for [[NVIDIA]] and [[AMD]]/[[ATi]] [[GPU]] Card：8.12/<br /> {{start date and age|2016|5|19}}<br />
AstroPulse v7：7.00/<br /> {{start date and age|2014|10|7}}<br />
AstroPulse v7 for nVidia and AMD/ATi GPU Card：7.10/<br /> {{start date and age|2015|4|23}}
| status                 = In hibernation
| goal                   = Discovery of radio evidence of [[extraterrestrial life]]
| funding                = [[Government spending#United States of America|Public funding]] and private donations
| programming language   = 
| operating system       = [[Microsoft Windows]], [[Linux]], [[Android (operating system)|Android]], [[macOS]], [[Solaris (operating system)|Solaris]],<ref>{{Cite web|url=https://boinc.berkeley.edu/projects.php|title=Choosing BOINC projects|website=boinc.berkeley.edu|access-date=January 3, 2023|archive-date=January 3, 2018|archive-url=https://web.archive.org/web/20180103072445/https://boinc.berkeley.edu/projects.php|url-status=live}}</ref><br />[[IBM AIX]], [[FreeBSD]], [[DragonflyBSD]], [[OpenBSD]], [[NetBSD]], [[HP-UX]], [[IRIX]], [[Tru64 Unix]], [[OS/2 Warp]], [[eComStation]]<ref>{{Cite web|url=https://boinc.berkeley.edu/trac/wiki/DownloadOther|title=DownloadOther – BOINC|website=boinc.berkeley.edu|access-date=January 3, 2023|archive-date=January 3, 2023|archive-url=https://web.archive.org/web/20230103033124/https://boinc.berkeley.edu/trac/wiki/DownloadOther|url-status=live}}</ref>
| platform               = [[Cross-platform]]
| genre                  = [[Volunteer computing]]
| license                = [[GNU General Public License|GPL]]<ref>{{Cite web|url=https://setiathome.berkeley.edu/sah_porting.php|title=Porting and optimizing SETI@home|website=setiathome.berkeley.edu|access-date=January 3, 2023|archive-date=January 3, 2023|archive-url=https://web.archive.org/web/20230103033126/https://setiathome.berkeley.edu/sah_porting.php|url-status=live}}</ref> <!-- or | licence = -->
| website                = {{URL| https://setiathome.berkeley.edu/ }}
| active users           = {{decrease}} 91,454 (March 2020)<ref name=bionicstats>{{cite web|title=Detailed stats – SETI@Home|url=http://boincstats.com/en/stats/0/project/detail/overview|website=BOINC stats|access-date=March 5, 2020|archive-date=January 4, 2015|archive-url=https://web.archive.org/web/20150104041228/http://boincstats.com/en/stats/0/project/detail/overview|url-status=live}}</ref>
| total users            = {{increase}} 1,803,163 (March 2020)<ref name=bionicstats/>
| active hosts           = 144,779 (March 2020)<ref name=bionicstats/>
| total hosts            = 165,178 (March 2020)<ref name=bionicstats/>
|screenshot=SETI@home_custom_background_and_logo_screensaver.gif|screenshot_size=250px|screenshot caption=Screensaver with custom background}}

''' SETI@home''' ("SETI at home") is a project of the [[Berkeley SETI Research Center]] to analyze radio signals with the aim of [[Search for extraterrestrial intelligence|searching for signs of extraterrestrial intelligence]]. Until March 2020, it was run as an Internet-based public [[volunteer computing]] project that employed the [[Berkeley Open Infrastructure for Network Computing|BOINC]] software platform. It is hosted by the [[Space Sciences Laboratory]] at the [[University of California, Berkeley]], and is one of many activities undertaken as part of the worldwide [[SETI]] effort.

SETI@home software was released to the public on May 17, 1999,<ref>{{cite web |url=https://science.nasa.gov/newhome/headlines/ast23may99_1.htm |publisher=[[NASA]] |title=ET, phone SETI@home! |author=Tony Phillips |date=May 23, 1999 |access-date=6 October 2006 |archive-url=https://web.archive.org/web/20061001170505/http://science.nasa.gov//newhome/headlines/ast23may99_1.htm |archive-date=October 1, 2006 }}</ref><ref>{{Cite APOD |title=How to Search for Aliens |date=May 17, 1999 |access-date=6 October 2006}}</ref><ref>{{cite web |url=http://setiathome.berkeley.edu/classic.php |title=SETI@home Classic: In Memoriam |date=December 15, 2005 |access-date=6 October 2006 |archive-date=March 8, 2007 |archive-url=https://web.archive.org/web/20070308090420/http://setiathome.berkeley.edu/classic.php |url-status=live }}</ref><ref>{{cite web |url=http://www.nettalklive.com/seti/ |title=Searches For ET! |work=Net Talk Live! |access-date=12 January 2022 |archive-url=https://web.archive.org/web/20000815053637/http://www.nettalklive.com/seti/ |archive-date=15 August 2000 }}</ref> making it the third large-scale use of [[volunteer computing]] over the Internet for research purposes, after [[Great Internet Mersenne Prime Search]] (GIMPS) was launched in 1996 and [[distributed.net]] in 1997. Along with [[MilkyWay@home]] and [[Einstein@home]], it is the third major computing project of this type that has the investigation of phenomena in interstellar space as its primary purpose.

In March 2020, the project stopped sending out new work to SETI@home users, bringing the crowdsourced computing aspect of the project to a stop.<ref>{{Cite news|last=Overbye|first=Dennis|url=https://www.nytimes.com/2020/03/23/science/seti-at-home-aliens.html|title=The Search for E.T. Goes on Hold, for Now|date=2020-03-23|work=The New York Times|access-date=2020-03-23|language=en-US|issn=0362-4331|archive-date=April 7, 2020|archive-url=https://web.archive.org/web/20200407093808/https://www.nytimes.com/2020/03/23/science/seti-at-home-aliens.html|url-status=live}}</ref> At the time, the team intended to shift focus onto the analysis and interpretation of the 20 years' worth of accumulated data. However, the team left open the possibility of eventually resuming volunteer computing using data from other radio telescopes, such as [[MeerKAT]] and [[Five-hundred-meter Aperture Spherical Telescope|FAST]].<ref>{{Cite magazine|magazine=[[Wired (magazine)|Wired]]|url=https://www.wired.com/story/setihome-is-over-but-the-search-for-alien-life-continues/|title=SETI@Home Is Over. But the Search for Alien Life Continues|access-date=February 27, 2021|first=Daniel|last=Oberhaus|date=2020-03-03|archive-date=February 28, 2021|archive-url=https://web.archive.org/web/20210228203800/https://www.wired.com/story/setihome-is-over-but-the-search-for-alien-life-continues/|url-status=live}}</ref>

As of November 2021, the science team has analysed the data and removed noisy signals ([[Radio Frequency Interference]]) using the Nebula tool they developed and will choose the top-scoring 100 or so multiplets to be observed using the [[Five-hundred-meter Aperture Spherical Telescope]], to which they have been granted 24 hours of observation time.<ref>{{Cite web|title=New zones, a milestone, and next steps|url=https://setiathome.berkeley.edu/forum_thread.php?id=85810#2088641|access-date=2021-11-27|website=setiathome.berkeley.edu|archive-date=November 27, 2021|archive-url=https://web.archive.org/web/20211127200350/https://setiathome.berkeley.edu/forum_thread.php?id=85810#2088641|url-status=live}}</ref>

==Scientific research==
The two original goals of SETI@home were:
* to do useful scientific work by supporting an observational analysis to detect intelligent life outside [[Earth]]<ref name="acmanderson">{{Cite journal |last1=Anderson |first1=David P. |last2=Cobb |first2=Jeff |last3=Korpela |first3=Eric |last4=Lebofsky |first4=Matt |last5=Werthimer |first5=Dan |date=November 2002 |title=SETI@home: an experiment in public-resource computing |url=https://dl.acm.org/doi/10.1145/581571.581573 |journal=Communications of the ACM |language=en |volume=45 |issue=11 |pages=56–61 |doi=10.1145/581571.581573 |s2cid=15439521 |issn=0001-0782 |access-date=September 19, 2022 |archive-date=September 20, 2022 |archive-url=https://web.archive.org/web/20220920172330/https://dl.acm.org/doi/10.1145/581571.581573 |url-status=live |url-access=subscription }}</ref>
* to prove the viability and practicality of the "volunteer computing" concept<ref>{{Cite web |title=S.E.T.I. - 100000 pr |url=https://sites.google.com/site/scoemiche/s-e-t-i |access-date=2022-09-19 |website=sites.google.com |archive-date=September 20, 2022 |archive-url=https://web.archive.org/web/20220920171704/https://sites.google.com/site/scoemiche/s-e-t-i |url-status=live }}</ref>

The second of these goals is considered to have succeeded completely. The current [[BOINC]] environment, a development of the original SETI@home, is providing support for many computationally intensive projects in a wide range of disciplines.

The first of these goals has to date yielded no conclusive results: no evidence for ETI signals has been shown via SETI@home. However, the ongoing continuation is predicated on the assumption that the observational analysis is not "ill-posed." The remainder of this article deals specifically with the original SETI@home observations/analysis. The vast majority of the sky (over 98%) has yet to be surveyed, and each point in the sky must be surveyed many times to exclude even a subset of possibilities.

==Procedure details==
SETI@home searches for possible evidence of radio transmissions from [[extraterrestrial intelligence]] using observational data from the [[Arecibo Observatory|Arecibo radio telescope]] and the [[Green Bank Telescope]].<ref>{{Cite web|url=https://seti.berkeley.edu/listen/research.html|title=Berkeley SETI|website=seti.berkeley.edu|access-date=10 June 2017|archive-date=July 31, 2018|archive-url=https://web.archive.org/web/20180731153757/https://seti.berkeley.edu/listen/research.html|url-status=live}}</ref> The data is taken "piggyback" or "passively" while the telescope is used for other scientific programs. The data is digitized, stored, and sent to the SETI@home facility. The data is then parsed into small chunks in frequency and time, and analyzed, using software, to search for any signals—that is, variations which cannot be ascribed to noise, and hence contain information. Using volunteer computing, SETI@home sends the millions of chunks of data to be analyzed off-site by home computers, and then have those computers report the results. Thus what appears a difficult problem in data analysis is reduced to a reasonable one by aid from a large, Internet-based community of borrowed computer resources.

The software searches for five types of signals that distinguish them from [[Electromagnetic interference|noise]]:<ref>{{cite web |url=http://seticlassic.ssl.berkeley.edu/about_seti/about_seti_at_home_4.html |title=How SETI@Home Works – What is SETI@home Looking For? |publisher=SETI@Home Classic |access-date=23 June 2010 |archive-date=September 9, 2019 |archive-url=https://web.archive.org/web/20190909020950/http://seticlassic.ssl.berkeley.edu/about_seti/about_seti_at_home_4.html |url-status=live }}</ref>
* Spikes in [[power spectrum|power spectra]]
* [[Gaussian function|Gaussian]] rises and falls in transmission power, possibly representing the telescope beam's [[main lobe]] passing over a radio source
* Triplets&nbsp;– three power spikes in a row
* [[Pulse (signal processing)|Pulsing]] signals that possibly represent a [[narrowband]] digital-style transmission
* [[Autocorrelation]] detects signal waveforms.

There are many variations on how an ETI signal may be affected by the interstellar medium, and by the relative motion of its origin compared to Earth. The potential "signal" is thus processed in many ways (although not testing all detection methods nor scenarios) to ensure the highest likelihood of distinguishing it from the scintillating noise already present in all directions of outer space. For instance, another planet is very likely to be moving at a speed and acceleration with respect to Earth, and that will shift the frequency, over time, of the potential "signal." Checking for this through processing is done, to an extent, in the SETI@home software.

The process is somewhat like tuning a radio to various [[Channel (broadcasting)|channels]], and looking at the signal strength meter. If the strength of the signal goes up, that gets attention. More technically, it involves a lot of digital signal processing, mostly [[discrete Fourier transform]]s at various [[chirp]] rates and durations.

==Results==
To date, the project has not confirmed the detection of any [[Extraterrestrial intelligence|ETI]] signals. However, it has identified several candidate targets (sky positions), where the spike in intensity is not easily explained as noise spots,<ref>{{cite web |url=http://seticlassic.ssl.berkeley.edu/candidates.html |title=Signal Candidate |publisher=Classic SETI@home |access-date=23 June 2010 |archive-date=September 1, 2007 |archive-url=https://web.archive.org/web/20070901054148/http://seticlassic.ssl.berkeley.edu/candidates.html |url-status=live }}</ref> for further analysis. The most significant candidate signal to date was announced on September 1, 2004, named [[Radio source SHGb02+14a]].

While the project has not reached the stated primary goal of finding extraterrestrial intelligence, it has proved to the scientific community that volunteer computing projects using Internet-connected computers can succeed as a viable analysis tool, and even beat the largest supercomputers.<ref>{{cite web |url=http://boincstats.com/en/stats/-1/project/detail |publisher=BOINCstats |title=BOINC combined – Credit overview |access-date=23 June 2010 |archive-date=January 22, 2013 |archive-url=https://web.archive.org/web/20130122022019/http://boincstats.com/en/stats/-1/project/detail/ |url-status=live }}</ref>{{Failed verification|date=March 2020}} However, it has not been demonstrated that the order of magnitude excess in computers used, many outside the home (the original intent was to use 50,000–100,000 "home" computers),<ref name="Sullivan">{{cite web |url=http://seticlassic.ssl.berkeley.edu/woody_paper.html |title=Sullivan, et al.: Seti@Home |publisher=Seticlassic.ssl.berkeley.edu |access-date=17 May 2009 |archive-date=December 21, 2008 |archive-url=https://web.archive.org/web/20081221172659/http://seticlassic.ssl.berkeley.edu/woody_paper.html |url-status=live }}</ref> has benefited the project scientifically. (For more on this, see {{section link||Challenges}} below.)

[[Astronomer]] [[Seth Shostak]] stated in 2004 that he expects to get a conclusive signal and proof of alien contact between 2020 and 2025, based on the [[Drake equation]].<ref>{{cite news | work = Space Daily | title = First Contact Within 20 Years: Shostak | url = http://www.spacedaily.com/news/seti-04e.html | date = July 22, 2004 | last = Shostak | first = Seth | author-link = Seth Shostak | access-date = 12 June 2006 | archive-date = June 29, 2006 | archive-url = https://web.archive.org/web/20060629082041/http://www.spacedaily.com/news/seti-04e.html | url-status = live }}</ref> This implies that a prolonged effort may benefit SETI@home, despite its (present) twenty-year run without success in ETI detection.

==Technology==
Anybody with an at least intermittently Internet-connected computer was able to participate in SETI@home by running a free program that downloaded and analyzed [[radio telescope]] data.

Observational data were recorded on 2-[[terabyte]] [[SATA]] hard disk drives fed from the [[Arecibo Telescope]] in Puerto Rico, each holding about 2.5 days of observations, which were then sent to [[University of California, Berkeley|Berkeley]].<ref name="Korpela">{{cite journal | title = SETI@home&nbsp;– Massively Distributed Computing for SETI | first = Eric | last = Korpela | author2 = Dan Werthimer | author3 = David Anderson | author4 = Jeff Cobb | author5 = Matt Lebofsky | journal = Computing in Science & Engineering | date = January 2001 | pages = 78–83 | url = http://setiathome.ssl.berkeley.edu/~korpela/papers/CISE.pdf | doi = 10.1109/5992.895191 | volume = 3 | issue = 1 | bibcode = 2001CSE.....3a..78K | access-date = October 25, 2005 | archive-date = October 23, 2014 | archive-url = https://web.archive.org/web/20141023225217/http://setiathome.ssl.berkeley.edu/~korpela/papers/CISE.pdf }}</ref> Arecibo does not have a broadband [[Internet access|Internet connection]], so data must go by [[postal mail]] to Berkeley.<ref>{{cite web |url=http://seticlassic.ssl.berkeley.edu/about_seti/about_seti_at_home_2.html |title=About SETI@home page 2 |publisher=Seticlassic.ssl.berkeley.edu |access-date=17 May 2009 |archive-date=March 10, 2020 |archive-url=https://web.archive.org/web/20200310022312/http://seticlassic.ssl.berkeley.edu/about_seti/about_seti_at_home_2.html |url-status=live }}</ref> Once there, it is divided in both [[time domain|time]] and [[frequency domain]]s ''work units'' of 107 seconds of data,<ref>{{cite web | title = The SETI@home Sky Survey | url = http://seticlassic.ssl.berkeley.edu/sciencepaper.html | author = SETI@home | date = 2001<!-- no valid last modified available --> | access-date = 2 June 2006 | archive-date = April 22, 2020 | archive-url = https://web.archive.org/web/20200422000741/http://seticlassic.ssl.berkeley.edu/sciencepaper.html | url-status = live }}</ref> or approximately 0.35 [[megabytes]] (350 [[kilobytes]] or 350,000 [[bytes]]), which overlap in time but not in frequency.<ref name="Korpela"/> These work units are then sent from the SETI@home [[Server (computing)|server]] over the Internet to personal computers around the world to analyze.

Data was merged into a [[database]] using SETI@home computers in Berkeley. [[Interference (communication)|Interference]] was rejected, and various pattern-detection algorithms were applied to search for the most interesting signals.

The project used [[CUDA]] for [[GPU]] processing starting in 2015.<ref>{{Cite web|url=https://setiathome.berkeley.edu/apps.php|title=Applications|access-date=July 5, 2019|archive-date=October 5, 2022|archive-url=https://web.archive.org/web/20221005061217/https://setiathome.berkeley.edu/apps.php|url-status=live}}</ref>

In 2016 SETI@home began processing data from the [[Breakthrough Listen]] project.<ref>{{Cite web|url=https://breakthroughinitiatives.org/news/3|title=Breakthrough Initiatives|website=breakthroughinitiatives.org|access-date=31 May 2019|archive-date=May 31, 2019|archive-url=https://web.archive.org/web/20190531153829/https://breakthroughinitiatives.org/news/3|url-status=live}}</ref>

===Software===
[[File:BOINC Manager Screenshot.jpg|thumb|left|upright|The [[Berkeley Open Infrastructure for Network Computing|BOINC]] Manager working on the SETI@home project (v 7.6.22)]]
[[Image:Setiathomeversion3point07.JPG|thumb|right|Screenshot of SETI@home Classic Screensaver (v3.07)]]
<!--Generally needs to go much deeper about how the software works internally rather than how it appears to a non-technical participant. Maybe put this in how it section and make this a history section?-->

The SETI@home volunteer computing software ran either as a [[screensaver]] or continuously while a user worked, making use of processor time that would otherwise be unused.

The initial software platform, now referred to as "SETI@home Classic", ran from May 17, 1999, to December 15, 2005. This program was only capable of running SETI@home; it was replaced by [[Berkeley Open Infrastructure for Network Computing]] (BOINC), which also allows users to contribute to other volunteer computing projects at the same time as running SETI@home. The BOINC platform also allowed testing for more types of signals.

The discontinuation of the SETI@home Classic platform rendered older [[Mac (computer)|Macintosh]] computers running the [[classic Mac OS]] (pre December, 2001) unsuitable for participating in the project.

SETI@home was available for the Sony [[PlayStation 3]] console.<ref>{{cite web|url=http://www.dotsch.de/boinc/SETI@home%20applications.html|archive-url=https://web.archive.org/web/20080108193313/http://www.dotsch.de/boinc/SETI%40home%20applications.html|archive-date=2008-01-08|title=SETI@home applications}}</ref>

On May 3, 2006, new work units for a new version of SETI@home called "SETI@home Enhanced" started distribution. Since computers had the power for more computationally intensive work than when the project began, this new version was more sensitive by a factor of two concerning Gaussian signals and to some kinds of pulsed signals than the original SETI@home (BOINC) software. This new application had been optimized to the point where it would run faster on some work units than earlier versions. However, some work units (the best work units, scientifically speaking) would take significantly longer.

In addition, some distributions of the SETI@home applications were optimized for a particular type of [[CPU]]. They were referred to as "optimized executables", and had been found to run faster on systems specific for that CPU. {{As of|2007}}, most of these applications were optimized for [[Intel]] processors and their corresponding [[instruction set]]s.<ref>{{cite web |url=http://lunatics.kwsn.net |title=Seti@Home optimized science apps and information |publisher=Lunatics.kwsn.net |access-date=17 May 2009 |archive-url=https://web.archive.org/web/20090424210331/http://lunatics.kwsn.net/ |archive-date=April 24, 2009 }}</ref>

The results of the data processing were normally automatically transmitted when the computer was next connected to the Internet; it could also be instructed to connect to the Internet as needed.

==Statistics==
With over 5.2&nbsp;million participants worldwide, the project was the volunteer computing project with the most participants to date{{when|date=March 2014}}. The original intent of SETI@home was to utilize 50,000–100,000 home computers.<ref name="Sullivan" /> Since its launch on May 17, 1999, the project has logged over two million years of aggregate computing time.{{as of?|date=May 2012}} On September 26, 2001, SETI@home had performed a total of 10<sup>21</sup> [[floating point]] operations. It was acknowledged by the 2008 edition of the ''[[Guinness World Records]]'' as the largest computation in history.<ref>{{cite web | title = Largest Computation | url = http://www.guinnessworldrecords.com/index.asp?id=53519 | work = Guinness World Records | editor = Newport, Stuart | date = 2005<!-- no valid last modified available --> | publisher = HCI Entertainment | access-date = 3 December 2005 |archive-url = https://web.archive.org/web/20051128165405/http://www.guinnessworldrecords.com/index.asp?id=53519 <!-- Bot retrieved archive --> |archive-date = November 28, 2005}}</ref> With over 145,000 active computers in the system (1.4&nbsp;million total) in 233 countries, {{As of|2013|06|23|lc=on}}, SETI@home had the ability to compute over 668 [[teraFLOPS]].<ref>{{cite web |url=http://boincstats.com/en/stats/0/project/detail |title=SETI@Home Project |publisher=BOINC Stats |access-date=23 June 2013 |archive-date=July 3, 2013 |archive-url=https://web.archive.org/web/20130703143037/http://boincstats.com/en/stats/0/project/detail |url-status=live }}</ref> For comparison, the [[Tianhe-2]] computer, which {{As of|2013|06|23|lc=on}} was the world's [[Top500|fastest]] [[supercomputer]], was able to compute 33.86 [[petaFLOPS]] (approximately 50 times greater).

==Project future==
There were plans to get data from the [[Parkes Observatory]] in Australia to analyze the southern hemisphere.<ref>{{cite web |url=http://seticlassic.ssl.berkeley.edu/setifuture.html#southern |title=Southern Hemisphere Search – increasing SETI@home's sky coverage in the "Future directions of SETI@home" |publisher=Classic SETI@home website |access-date=23 June 2010 |archive-date=February 19, 2007 |archive-url=https://web.archive.org/web/20070219101606/http://seticlassic.ssl.berkeley.edu/setifuture.html#southern |url-status=live }}</ref> However, {{As of|2018|06|03|lc=on}}, these plans were not mentioned in the project's website. Other plans include a Multi-Beam Data Recorder, a Near Time Persistency Checker and [[Astropulse]] (an application that uses coherent dedispersion to search for pulsed signals).<ref>{{cite web |url=http://setiathome.berkeley.edu/sah_plans.php |title=SETI@home Plans |publisher=SETI@home |access-date=23 June 2010 |archive-date=October 11, 2007 |archive-url=https://web.archive.org/web/20071011025755/http://setiathome.berkeley.edu/sah_plans.php |url-status=live }}</ref> Astropulse will team with the original SETI@home to detect other sources, such as rapidly rotating pulsars, exploding primordial black holes, or as-yet unknown astrophysical phenomena.<ref>{{cite web |url=http://setiathome.berkeley.edu/ap_faq.php |title=Astropulse FAQ |publisher=Setiathome.berkeley.edu |access-date=17 May 2009 |archive-date=April 29, 2009 |archive-url=https://web.archive.org/web/20090429072028/http://setiathome.berkeley.edu/ap_faq.php |url-status=live }}</ref> Beta testing of the final public release version of Astropulse was completed in July 2008, and the distribution of work units to higher spec machines capable of processing the more CPU intensive work units started in mid-July 2008.

On March 31, 2020, UC Berkeley stopped sending out new data for SETI@Home clients to process, ending the effort for the time being. The program stated they were at a point of "diminishing returns" with the volunteer processing and needed to put the effort into hibernation while they processed the results.<ref>{{cite web | url = https://www.engadget.com/2020/03/04/seti-home-stops-for-now/ | title = SETI@Home ends its crowdsourced search for alien life after 21 years | first = Daniel | last = Cooper | date = March 4, 2020 | access-date = March 4, 2020 | work = [[Engadget]] | archive-date = March 5, 2020 | archive-url = https://web.archive.org/web/20200305051713/https://www.engadget.com/2020/03/04/seti-home-stops-for-now/ | url-status = live }}</ref>

==Competitive aspect==
SETI@home users quickly started to compete with one another to process the maximum number of work units. Teams were formed to combine the efforts of individual users. The competition continued and grew larger with the introduction of BOINC.

As with any competition, attempts have been made to "cheat" the system and claim credit for work that has not been performed. To combat cheats, the SETI@home system sends every work unit to multiple computers, a value known as "initial replication" (currently '''2'''). Credit is only granted for each returned work unit once a minimum number of results have been returned and the results agree, a value known as "minimum quorum" (currently '''2'''). If, due to computation errors or cheating by submitting false data, not enough results agree, more identical work units are sent out until the minimum quorum can be reached. The final credit granted to all machines which returned the correct result is the same and is the lowest of the values claimed by each machine.

Some users have installed and run SETI@home on computers at their workplaces; an act known as "Borging", after the assimilation-driven [[Borg (Star Trek)|Borg]] of ''[[Star Trek]]''. In some cases, SETI@home users have misused company resources to gain work-unit results with at least two individuals getting fired for running SETI@home on an enterprise production system.<ref>{{cite news |url=http://news.bbc.co.uk/1/hi/sci/tech/1782050.stm |title=BBC 2002 |work=BBC News |date=January 28, 2002 |access-date=17 May 2009 |archive-date=January 7, 2009 |archive-url=https://web.archive.org/web/20090107085414/http://news.bbc.co.uk/1/hi/sci/tech/1782050.stm |url-status=live }}</ref> <!-- The first firing was much earlier, but needs citation finding before one can use that information-->There is a thread in the newsgroup alt.sci.seti which bears the title "Anyone fired for SETI screensaver"<ref>{{Cite web|url=https://groups.google.com/g/alt.sci.seti/c/0ksE8kN4wJI|title=Anyone fired for SETI screensaver|website=groups.google.com|access-date=June 6, 2022|archive-date=June 6, 2022|archive-url=https://web.archive.org/web/20220606023940/https://groups.google.com/g/alt.sci.seti/c/0ksE8kN4wJI|url-status=live}}</ref> and ran starting as early as September 14, 1999.

Other users collect large quantities of equipment together at home to create "SETI farms", which typically consist of a number of computers consisting of only a [[motherboard]], [[Central processing unit|CPU]], [[RAM]] and [[power supply]] that are arranged on shelves as diskless [[Workstation (computer hardware)|workstations]] running either [[Linux]] or old versions of [[Microsoft Windows]] "headless" (without a monitor).<ref>{{cite web|url=http://bhs.broo.k12.wv.us/homepage/staff/seti/farms.htm |title=SETI Stack and farm systems |publisher=Bhs.broo.k12.wv.us |access-date=14 July 2009 |archive-url=https://web.archive.org/web/20090131122519/http://bhs.broo.k12.wv.us/homepage/staff/seti/farms.htm |archive-date=January 31, 2009 }}</ref>

==Challenges==

===Closure of Arecibo Observatory===

Until 2020, SETI@home procured its data from the [[Arecibo Observatory]] facility that was operated by the National Astronomy and Ionosphere Center and administered by [[SRI International]].

The decreasing operating budget for the observatory has created a shortfall of funds which has not been made up from other sources such as private donors, [[NASA]], other foreign research institutions, nor private non-profit organizations such as SETI@home.

However, in the overall long-term views held by many involved with the SETI project, any usable radio telescope could take over from Arecibo (which completely collapsed in December 2020),<ref name="guardian collapsed">{{cite news|date=1 December 2020|title=Giant Arecibo radio telescope collapses in Puerto Rico|work=[[The Guardian]]|agency=[[Associated Press]]|url=https://www.theguardian.com/world/2020/dec/01/arecibo-radio-telescope-collapses-puerto-rico|access-date=1 December 2020|archive-date=December 5, 2020|archive-url=https://web.archive.org/web/20201205135942/https://www.theguardian.com/world/2020/dec/01/arecibo-radio-telescope-collapses-puerto-rico|url-status=live}}</ref><ref name="APNews1Dec2020">{{cite news |last1=Coto |first1=Danica |title=Huge Puerto Rico radio telescope, already damaged, collapses |url=https://apnews.com/article/technology-arecibo-observatory-puerto-rico-science--0da6abb251f455977bf0c752348e712e |access-date=5 December 2020 |work=AP NEWS |date=1 December 2020 |archive-date=April 22, 2021 |archive-url=https://web.archive.org/web/20210422013836/https://apnews.com/article/technology-arecibo-observatory-puerto-rico-science--0da6abb251f455977bf0c752348e712e |url-status=live }}</ref> as all the SETI systems are portable and relocatable.

===More restrictive computer use policies in businesses===
In one documented case, an individual was fired for explicitly importing and using the SETI@home software on computers used for the U.S. state of Ohio.<ref>{{cite web |date=October 9, 2004 |author=John Adams |url=http://www.oreillynet.com/databases/blog/2004/10/knock_down_then_kick.html |title=Knock Down, Then Kick – O'Reilly Databases |publisher=Oreillynet.com |access-date=17 May 2009 |archive-date=May 13, 2013 |archive-url=https://web.archive.org/web/20130513035117/http://www.oreillynet.com/databases/blog/2004/10/knock_down_then_kick.html |url-status=live }}</ref> In another incident a school IT director resigned after his installation allegedly cost his school district $1&nbsp;million in removal costs; however, other reasons for this firing included lack of communication with his superiors, not installing [[firewall (computing)|firewall]] software and alleged theft of computer equipment,<ref>{{cite news |title=Higley firing tied to alien-search software |date=November 30, 2009 |newspaper=The Arizona Republic |url=http://www.azcentral.com/news/articles/2009/11/30/20091130searchforaliens1202.html |archive-url=https://web.archive.org/web/20100407055848/http://www.azcentral.com/news/articles/2009/11/30/20091130searchforaliens1202.html |archive-date=April 7, 2010 |url-status=dead}}</ref> leading a [[ZDNet]] editor to comment that "the volunteer computing nonsense was simply the best and most obvious excuse the district had to terminate his contract [[Dismissal (employment)#Reasons|with cause]]".<ref>{{cite news |author=Christopher Dawson |url=http://www.zdnet.com/blog/education/admin-fired-for-incompetence-not-alien-search/3408 |title=Admin fired for incompetence, not alien search |work=ZDNet |date=December 2, 2009 |access-date=20 November 2013 |archive-date=May 11, 2010 |archive-url=https://web.archive.org/web/20100511193644/http://www.zdnet.com/blog/education/admin-fired-for-incompetence-not-alien-search/3408 |url-status=dead }}</ref>

{{As of|2005|10|16}}, approximately one-third of the processing for the non-BOINC version of the software was performed on work or school based machines.<ref>{{cite web | author = SETI@home | year = 2005 | url = http://seticlassic.ssl.berkeley.edu/stats/venues.html | title = SETI@home computer venues | access-date = 12 June 2006 | archive-date = July 3, 2008 | archive-url = https://web.archive.org/web/20080703160840/http://seticlassic.ssl.berkeley.edu/stats/venues.html | url-status = live }}</ref> As many of these computers will give reduced privileges to ordinary users, it is possible that much of this has been done by [[network administrator]]s.

To some extent, this may be offset by [[Internet access#History|better connectivity to home machines]] and [[Moore's law|increasing performance]] of home computers,{{Citation needed|date=December 2007}} especially those with [[GPU]]s,<ref name="SETI_GPU">{{Cite web
 |url=http://setiathome.berkeley.edu/forum_thread.php?id=73935
 |title=SETI@home now supports Intel GPUs
 |date=January 29, 2014
 |access-date=February 19, 2015
 |archive-date=February 20, 2015
 |archive-url=https://web.archive.org/web/20150220063011/http://setiathome.berkeley.edu/forum_thread.php?id=73935
 |url-status=live
 }}</ref> which have also benefited other volunteer computing projects such as [[Folding@Home]].<ref>{{cite web
 | url = https://www.engadget.com/2006/09/29/stanford-university-tailors-folding-home-to-gpus/
 | title = Stanford University tailors Folding@home to GPUs
 | author = Darren Murph
 | date = September 29, 2006
 | access-date = February 19, 2015
 | archive-date = October 12, 2007
 | archive-url = https://web.archive.org/web/20071012000648/http://www.engadget.com/2006/09/29/stanford-university-tailors-folding-home-to-gpus/
 | url-status = live
 }}</ref><ref>{{cite web
 | url = http://graphics.stanford.edu/~mhouston/
 | title = Folding@Home – GPGPU
 | author = Mike Houston
 | access-date = February 19, 2015
 | archive-date = October 27, 2007
 | archive-url = https://web.archive.org/web/20071027130116/http://graphics.stanford.edu/~mhouston/
 | url-status = live
 }}</ref> The spread of [[mobile computing]] devices provides another large resource for volunteer computing. For example, in 2012, Piotr Luszczek (a former doctoral student of [[Jack Dongarra]]) presented results showing that an [[iPad 2]] matched the historical performance of a [[Cray-2]] (the fastest computer in the world in 1985) on an embedded [[LINPACK]] benchmark.<ref name="iPad2_Cray2">{{Cite web
 |url=https://www.phoronix.com/scan.php?page=news_item&px=MTE4NjU
 |title=Apple iPad 2 As Fast As The Cray-2 Super Computer
 |first=Michael
 |last=Larabel
 |date=September 16, 2012
 |access-date=February 19, 2015
 |archive-date=February 20, 2015
 |archive-url=https://web.archive.org/web/20150220054659/http://www.phoronix.com/scan.php?page=news_item&px=MTE4NjU
 |url-status=live
 }}</ref>

===Funding===
There is currently no government [[funding]] for SETI research, and private funding is always limited. Berkeley Space Science Lab has found ways of working with small budgets, and the project has received donations allowing it to go well beyond its original planned duration, but it still has to compete for limited funds with other SETI projects and other space sciences projects.

In a December 16, 2007 plea for donations, SETI@home stated its present modest state and urged donations of $476,000 needed for continuation into 2008.

===Unofficial clients===
A number of individuals and companies made unofficial changes to the distributed part of the software to try to produce faster results, but this compromised the integrity of all the results.<ref>{{cite journal | title = The SETI@Home Problem | journal = Crossroads |year = 2000 | first = David | last = Molnar | volume = 7 | issue = 1| url = http://oldwww.acm.org/crossroads/xrds7-1/september2000.html | archive-url = https://archive.today/20120715134754/http://oldwww.acm.org/crossroads/xrds7-1/september2000.html | archive-date = 15 July 2012 | access-date = 30 January 2011}}</ref> As a result, the software had to be updated to make it easier to detect such changes, and discover unreliable clients. BOINC will run on unofficial clients; however, clients that return different and therefore incorrect data are not allowed, so corrupting the result database is avoided. BOINC relies on cross-checking to validate data<ref>{{cite web |url=http://boinc.berkeley.edu/trac/wiki/SecurityIssues |title=SecurityIssues – BOINC – Trac |publisher=Boinc.berkeley.edu |access-date=17 May 2009 |archive-date=June 5, 2011 |archive-url=https://web.archive.org/web/20110605024001/http://boinc.berkeley.edu/trac/wiki/SecurityIssues |url-status=live }}</ref> but unreliable clients need to be identified, to avoid situations when two of these report the same invalid data and therefore corrupt the database. A very popular unofficial client (lunatic) allows users to take advantage of the special features provided by their processor(s) such as [[Streaming SIMD Extensions|SSE]], [[SSE2]], [[SSE3]], [[SSSE3]], [[SSE4]].1, and [[Advanced Vector Extensions|AVX]] to allow for faster processing.

===Hardware and database failures===
{{original research|date=February 2023|part=section|reason=The section appears to be original research elaboration upon the passing mention of "The sources of failure, both hardware and software,seemed limitless." in <ref name="acmanderson" />.}}
SETI@home is a test bed for further development not only of BOINC but of other hardware and software (database) technology. Under SETI@home processing loads, these experimental technologies can be more challenging than expected, as SETI databases do not have typical accounting and business data or relational structures. The non-traditional database uses often do incur greater processing overheads and risk of database corruption and outright database failure. Hardware, software and database failures can (and do) cause dips in project participation.

The project has had to shut down several times to change over to new databases capable of handling more massive datasets. Hardware failure has proven to be a substantial source of project shutdowns, as hardware failure is often coupled with database corruption.

==See also==
{{div col}}
*[[Active SETI]]
*[[BrookGPU]]
*[[Folding@home]]
*[[Grid computing]]
*[[List of volunteer computing projects]]
*[[PlanetQuest]]
*[[Primegrid]]
*[[Rosetta@home]]
*[[SETIcon]]
*[[Systemic (amateur extrasolar planet search project)]]
*[[World Community Grid]]
{{div col end}}

==References==
{{Reflist|colwidth=30em}}

==Further reading==
*{{cite journal | title = The Ultimate Hacker: SETI Signals May Need to Be Decontaminated | first = Richard A. Jr. | last = Carrigan | journal = Bioastronomy 2002: Life Among the Stars |year = 2003 | volume = 213 | publisher=Astronomical Society of the Pacific | page = 519 | bibcode=2004IAUS..213..519C}}
*{{cite news | title = Scientists be on guard... | url = http://technology.guardian.co.uk/news/story/0,16559,1650296,00.html | author = Sample, Ian | work = The Guardian |access-date = 25 November 2005 | location=London | date=25 November 2005<!-- no valid last modified available -->}}
*{{Cite web |url=https://www.theatlantic.com/science/archive/2017/05/aliens-on-your-packard-bell/527445/ |title=A Brief History of SETI@Home |publisher=The Atlantic |first=Sarah |last=Scoles |date=May 23, 2017}}

==External links==
{{Commons category|SETI@home}}
* {{Official website| https://setiathome.berkeley.edu/ }}
* {{YouTube|id=IfeGNAZY92k|title=SETI@home screensaver video}}

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{{Extraterrestrial life}}
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