Editing LIGO (section)

===Observations begin===
Initial LIGO operations between 2002 and 2010 did not detect any gravitational waves. In 2004, under Barish, the funding and groundwork were laid for the next phase of LIGO development (called "Enhanced LIGO"). This was followed by a multi-year shut-down while the detectors were replaced by much improved "Advanced LIGO" versions.<ref>{{cite web| title=Gravitational wave detection a step closer with Advanced LIGO| url=http://spie.org/newsroom/technical-articles/videos/ligo-hanford-spie-video| publisher=SPIE Newsroom| access-date=4 January 2016}}</ref><ref>{{cite web|title=Daniel Sigg: The Advanced LIGO Detectors in the era of First Discoveries|url=http://spie.org/x120637.xml|publisher=SPIE Newsroom|access-date=9 September 2016}}</ref> Much of the research and development work for the LIGO/aLIGO machines was based on pioneering work for the [[GEO600]] detector at Hannover, Germany.<ref name="GEO600 a precursor">{{cite news |last=Ghosh |first=Pallab |url=https://www.bbc.com/news/science-environment-35524440 |title=Einstein's gravitational waves 'seen' from black holes |work=BBC News |date=11 February 2016 |access-date=18 February 2016 }}</ref><ref name="mpg2016">{{cite web |title=Gravitational waves detected 100 years after Einstein's prediction |url=https://www.mpg.de/9953360/gravitational-waves-detected |website=www.mpg.de |publisher=Max-Planck-Gelschaft |access-date=3 September 2018 |language=en}}</ref> By February 2015, the detectors were brought into engineering mode in both locations.<ref>{{cite web |title=LIGO Hanford's H1 Achieves Two-Hour Full Lock |url=https://www.advancedligo.mit.edu/feb_2015_news.html |date=February 2015 |url-status=dead |archive-url=https://web.archive.org/web/20150922064706/https://www.advancedligo.mit.edu/feb_2015_news.html |archive-date=22 September 2015  }}</ref>

In mid-September 2015, "the world's largest gravitational-wave facility" completed a five-year US$200-million overhaul, bringing the total cost to $620 million.<ref name="Nature_2015_Sept_15">{{citation |title=Hunt for gravitational waves to resume after massive upgrade: LIGO experiment now has better chance of detecting ripples in space-time|journal=Nature |volume=525 |issue=7569 |pages=301–302 |first=Davide |last=Castelvecchi|date=15 September 2015 |doi=10.1038/525301a |pmid=26381963 |bibcode=2015Natur.525..301C |doi-access=free }}</ref><ref>{{cite magazine |first=Sarah |last=Zhang |title=The Long Search for Elusive Ripples in Spacetime |magazine=Wired |url=https://www.wired.com/2015/09/long-search-elusive-ripples-spacetime |date=15 September 2015}}</ref> On 18 September 2015, Advanced LIGO began its first formal science observations at about four times the sensitivity of the initial LIGO interferometers.<ref>{{cite news |last=Amos |first=Jonathan |title=Advanced Ligo: Labs 'open their ears' to the cosmos |url=https://www.bbc.com/news/science-environment-34298363 |journal=BBC News |date=19 September 2015 |access-date=19 September 2015}}</ref> Its sensitivity was to be further enhanced until it was planned to reach design sensitivity {{As of|alt=around 2021|2021|01|post=.}}<ref name="LIGO_dec_2015">{{cite web| title=Planning for a bright tomorrow: prospects for gravitational-wave astronomy with Advanced LIGO and Advanced Virgo| url=http://www.ligo.org/science/Publication-ObservingScenario/index.php| publisher=[[LIGO Scientific Collaboration]] |access-date=31 December 2015 |date=23 December 2015}}</ref>

====Detections====
On 11 February 2016, the LIGO Scientific Collaboration and [[Virgo interferometer|Virgo Collaboration]] published a paper about the [[First observation of gravitational waves|detection of gravitational waves]], from a signal detected at 09.51 [[UTC]] on 14 September 2015 of two ~30 [[solar mass]] black holes merging about 1.3 billion [[light-years]] from Earth.<ref name="PhysRevLett.116.061102">{{cite journal |title=Observation of Gravitational Waves from a Binary Black Hole Merger |journal=Physical Review Letters |volume=116 |issue=6 |pages=061102 |date=11 February 2016 |last=LIGO Scientific Collaboration and Virgo Collaboration |first=B. P. Abbott|doi=10.1103/PhysRevLett.116.061102 |pmid=26918975 |arxiv = 1602.03837 |bibcode = 2016PhRvL.116f1102A |s2cid=124959784 }}</ref><ref name="Nature_11Feb16" />

Current executive director [[David Reitze]] announced the findings at a media event in Washington D.C., while executive director emeritus Barry Barish presented the first scientific paper of the findings at CERN to the physics community.<ref>{{Cite book | url=https://cds.cern.ch/record/2131411 | title=New results on the Search for Gravitational Waves| year=2016| series=CERN Colloquium}}</ref>

On 2 May 2016, members of the [[LIGO Scientific Collaboration]] and other contributors were awarded a [[Fundamental Physics Prize|Special Breakthrough Prize in Fundamental Physics]] for contributing to the direct detection of gravitational waves.<ref name=FPP-May2016>{{cite web|title=Fundamental Physics Prize – News|url=https://breakthroughprize.org/News/32|publisher=Fundamental Physics Prize (2016)|access-date=4 May 2016}}</ref>

On 16 June 2016 LIGO announced a [[GW151226|second signal]] was detected from the merging of two black holes with 14.2 and 7.5 times the mass of the Sun. The signal was picked up on 26 December 2015, at 3:38 UTC.<ref name="chu"/>

The detection of a third black hole merger, between objects of 31.2 and 19.4 solar masses, occurred on 4 January 2017 and was announced on 1 June 2017.<ref name = "Abbott2017">{{cite journal |doi=10.1103/PhysRevLett.118.221101 |pmid= 28621973 |title= GW170104: Observation of a 50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2 |journal= [[Physical Review Letters]] |date= 1 June 2017 |author=B. P. Abbott |display-authors=etal |collaboration=[[LIGO Scientific Collaboration]] and [[Virgo interferometer|Virgo Collaboration]] |volume=118 |issue= 22 |pages=221101|arxiv=1706.01812 |bibcode=2017PhRvL.118v1101A |s2cid= 206291714 }}</ref><ref name = SciNews2017.06.01>{{cite journal | last = Conover | first = E. | title = LIGO snags another set of gravitational waves | journal = [[Science News]] | date = 1 June 2017 | url = https://www.sciencenews.org/article/ligo-snags-another-set-gravitational-waves | access-date = 3 June 2017}}</ref> [[Laura Cadonati]] was appointed the first deputy spokesperson.<ref>{{cite web | url=https://news.gatech.edu/news/2017/04/20/college-sciences-professor-appointed-top-role-search-gravitational-waves | title=College of Sciences Professor Appointed to Top Role in Search for Gravitational Waves &#124; News Center }}</ref>

A fourth detection of a black hole merger, between objects of 30.5 and 25.3 solar masses, was observed on 14 August 2017 and was announced on 27 September 2017.<ref>{{cite web|title=GW170814 : A three-detector observation of gravitational waves from a binary black hole coalescence|url=https://dcc.ligo.org/LIGO-P170814/public/main|access-date=29 September 2017}}</ref>

In 2017, Weiss, Barish, and Thorne received the [[Nobel Prize in Physics]] "for decisive contributions to the LIGO detector and the observation of gravitational waves." Weiss was awarded one-half of the total prize money, and Barish and Thorne each received a one-quarter prize.<ref>{{cite web|title=The Nobel Prize in Physics 2017|url=https://www.nobelprize.org/nobel_prizes/physics/laureates/2017/press.html|website=Nobelprize.org|access-date=4 October 2017}}</ref><ref name="BBC-20171003">{{cite news |last1=Rincon |first1=Paul |last2=Amos |first2=Jonathan |url=https://www.bbc.co.uk/news/science-environment-41476648|title=Einstein's waves win Nobel Prize |work=[[BBC News]] |date=3 October 2017 |access-date=3 October 2017}}</ref><ref name="NYT-20171003">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |title=2017 Nobel Prize in Physics Awarded to LIGO Black Hole Researchers |url=https://www.nytimes.com/2017/10/03/science/nobel-prize-physics.html |date=3 October 2017 |work=[[The New York Times]] |access-date=3 October 2017 }}</ref>

After shutting down for improvements, LIGO resumed operation on 26 March 2019, with Virgo joining the network of gravitational-wave detectors on 1 April 2019.<ref>{{Cite web | url= https://www.ligo.org/news/pr-O3resumes.pdf| title=LSC News}}</ref> Both ran until 27 March 2020, when the [[COVID-19 pandemic]] halted operations.<ref name="O3suspended" /> During the COVID shutdown, LIGO underwent a further upgrade in sensitivity, and observing run O4 with the new sensitivity began on 24 May 2023.<ref name=":1" />