Editing Fermi paradox (section)

=== Searches for stellar-scale artifacts ===
{{further|Dyson sphere|Stellar engine|Kardashev scale}}
[[File:Dyson Sphere Diagram-en.svg|thumb|upright=1.2|A variant of the speculative [[Dyson sphere]]. Such large-scale artifacts would drastically alter the spectrum of a star.]]
In 1959, [[Freeman Dyson]] observed that every developing human civilization constantly increases its energy consumption, and he conjectured that a civilization might try to harness a large part of the energy produced by a star. He proposed a hypothetical "Dyson sphere" as a means: a shell or cloud of objects enclosing a star to absorb and utilize as much [[radiant energy]] as possible. Such a feat of [[astroengineering]] would drastically alter the observed [[spectroscopy|spectrum]] of the star involved, changing it at least partly from the normal [[emission lines]] of a natural [[stellar atmosphere]] to those of [[black-body radiation]], probably with a peak in the [[infrared]]. Dyson speculated that advanced alien civilizations might be detected by examining the spectra of stars and searching for such an altered spectrum.<ref>{{cite journal| journal=[[Science (journal)|Science]]| date=1960| url=http://www.islandone.org/LEOBiblio/SETI1.HTM| title=Search for Artificial Stellar Sources of Infra-Red Radiation| author=Dyson, Freeman J.| pages=1667–1668| volume=131| doi=10.1126/science.131.3414.1667| pmid=17780673| issue=3414| bibcode=1960Sci...131.1667D| s2cid=3195432| author-link=Freeman Dyson| access-date=August 19, 2010| archive-url=https://web.archive.org/web/20190714215002/http://www.islandone.org/LEOBiblio/SETI1.HTM| archive-date=July 14, 2019| url-status=live}}</ref><ref name="G^I">{{Cite journal| arxiv=1408.1133| last1= Wright| first1= J. T.| title= The Ĝ Infrared Search for Extraterrestrial Civilizations with Large Energy Supplies. I. Background and Justification| journal= The Astrophysical Journal| volume= 792| issue= 1| pages= 26| last2= Mullan| first2= B.| last3= Sigurðsson| first3= S.|last4= Povich| first4= M. S.| date= 2014| doi= 10.1088/0004-637X/792/1/26| bibcode= 2014ApJ...792...26W| s2cid= 119221206}}</ref><ref name="G^II">{{Cite journal| arxiv=1408.1134| last1= Wright| first1= J. T.| title= The Ĝ Infrared Search for Extraterrestrial Civilizations with Large Energy Supplies. II. Framework, Strategy, and First Result| journal= The Astrophysical Journal| volume= 792| issue= 1| pages= 27| last2= Griffith| first2= R.| last3= Sigurðsson| first3= S.| last4= Povich| first4= M. S.| last5= Mullan| first5= B.| date= 2014| doi= 10.1088/0004-637X/792/1/27| bibcode= 2014ApJ...792...27W| s2cid= 16322536}}</ref>

There have been attempts to find evidence of Dyson spheres that would alter the spectra of their core stars.<ref>{{cite web|url = http://home.fnal.gov/~carrigan/infrared_astronomy/Fermilab_search.htm|title = Fermilab Dyson Sphere search program|publisher = Fermi National Accelerator Laboratory|access-date = February 10, 2008|archive-url = https://web.archive.org/web/20060306222359/http://home.fnal.gov/~carrigan/Infrared_Astronomy/Fermilab_search.htm|archive-date = March 6, 2006|url-status = dead}}</ref> Direct observation of thousands of galaxies has shown no explicit evidence of artificial construction or modifications.<ref name="G^I" /><ref name="G^II" /><ref name="G^III">{{Cite journal|first1=J. T. |last1=Wright |first2=B |last2=Mullan |first3=S |last3=Sigurdsson |first4=M. S |last4=Povich |arxiv=1504.03418 |title=The Ĝ Infrared Search for Extraterrestrial Civilizations with Large Energy Supplies. III. The Reddest Extended Sources in WISE |journal=The Astrophysical Journal Supplement Series |volume=217 |issue=2 |pages=25 |date=2014|doi=10.1088/0067-0049/217/2/25 |bibcode=2015ApJS..217...25G |s2cid=118463557 }}</ref><ref>{{cite news |title=Alien Supercivilizations Absent from 100,000 Nearby Galaxies |url=http://www.scientificamerican.com/article/alien-supercivilizations-absent-from-100-000-nearby-galaxies/ |work=Scientific American |date=April 17, 2015 |access-date=June 29, 2015 |archive-url=https://web.archive.org/web/20150622003330/http://www.scientificamerican.com/article/alien-supercivilizations-absent-from-100-000-nearby-galaxies/ |archive-date=June 22, 2015 |url-status=live }}</ref> In October 2015, there was speculation that a dimming of light from star [[KIC 8462852]], observed by the [[Kepler space telescope]], could have been a result of Dyson sphere construction.<ref>{{Cite journal|arxiv=1510.04606| last1= Wright| first1= Jason T.|title= The Ĝ Search for Extraterrestrial Civilizations with Large Energy Supplies. IV. The Signatures and Information Content of Transiting Megastructures| journal= The Astrophysical Journal| volume= 816| issue= 1| pages= 17| last2=Cartier| first2= Kimberly M. S.| last3= Zhao| first3= Ming| last4= Jontof-Hutter| first4= Daniel| last5= Ford| first5= Eric B.| year= 2015| doi= 10.3847/0004-637X/816/1/17|bibcode = 2016ApJ...816...17W | s2cid= 119282226| doi-access= free}}</ref><ref name="ATL-20151013">{{cite web| last1=Andersen| first1=Ross| title=The Most Mysterious Star in Our Galaxy| url=https://www.theatlantic.com/science/archive/2015/10/the-most-interesting-star-in-our-galaxy/410023/| date=October 13, 2015| work=[[The Atlantic]]| access-date=October 13, 2015| archive-url=https://web.archive.org/web/20170720013427/https://www.theatlantic.com/science/archive/2015/10/the-most-interesting-star-in-our-galaxy/410023/| archive-date=July 20, 2017| url-status=live}}</ref> However, in 2018, further observations determined that the amount of dimming varied by the frequency of the light, pointing to dust, rather than an opaque object such as a Dyson sphere, as the cause of the dimming.<ref>{{Cite journal |title=The First Post-Kepler Brightness Dips of KIC 8462852 |journal=The Astrophysical Journal |volume=853 |issue=1 |at=L8 |arxiv=1801.00732 |first1=Tabetha S. |last1=Boyajian |display-authors=etal |doi=10.3847/2041-8213/aaa405 |year=2018 |bibcode=2018ApJ...853L...8B|s2cid=215751718 |doi-access=free }}</ref><ref>{{cite news |last1=Overbye |first1=Dennis |title=Magnetic Secrets of Mysterious Radio Bursts in a Faraway Galaxy |url=https://www.nytimes.com/2018/01/10/science/neutron-star-fast-radio-bursts.html |access-date=April 2, 2019 |work=The New York Times |date=January 10, 2018 |archive-url=https://web.archive.org/web/20180111001837/https://www.nytimes.com/2018/01/10/science/neutron-star-fast-radio-bursts.html |archive-date=January 11, 2018 |url-status=live }}</ref>