Editing General relativity (section)

=== Gravitational-wave astronomy ===
{{Main|Gravitational wave|Gravitational-wave astronomy}}
[[File:LISA.jpg|thumb|upright=0.8|Artist's impression of the space-borne gravitational wave detector [[Laser Interferometer Space Antenna|LISA]]]]
Observations of binary pulsars provide strong indirect evidence for the existence of gravitational waves (see [[#Orbital decay|Orbital decay]], above). Detection of these waves is a major goal of current relativity-related research.<ref>{{Harvnb|Barish|2005}}, {{Harvnb|Bartusiak|2000}}, {{Harvnb|Blair|McNamara|1997}}</ref> Several land-based [[gravitational wave detector]]s are currently in operation, most notably the [[Interferometric gravitational wave detector|interferometric detectors]] [[GEO 600]], [[LIGO]] (two detectors), [[TAMA 300]] and [[Virgo interferometer|VIRGO]].<ref>{{Harvnb|Hough|Rowan|2000}}</ref> Various [[pulsar timing array]]s are using [[millisecond pulsar]]s to detect gravitational waves in the 10<sup>−9</sup> to 10<sup>−6</sup> [[hertz]] frequency range, which originate from binary supermassive blackholes.<ref>{{Citation | last1=Hobbs | first1=George |title=The international pulsar timing array project: using pulsars as a gravitational wave detector | last2=Archibald | first2=A. | last3=Arzoumanian | first3=Z. | last4=Backer | first4=D. | last5=Bailes | first5=M. | last6=Bhat | first6=N. D. R. | last7=Burgay | first7=M. | last8=Burke-Spolaor | first8=S. | last9=Champion | first9=D. | display-authors = 8| doi=10.1088/0264-9381/27/8/084013 | date=2010 | journal=Classical and Quantum Gravity | volume=27 | issue=8 | page=084013 |arxiv=0911.5206 |bibcode = 2010CQGra..27h4013H | s2cid=56073764 }}</ref> A European space-based detector, [[Laser Interferometer Space Antenna|eLISA / NGO]], is currently under development,<ref>{{Harvnb|Danzmann|Rüdiger|2003}}</ref> with a precursor mission ([[LISA Pathfinder]]) having launched in December 2015.<ref>{{cite web|url=http://www.esa.int/esaSC/120397_index_0_m.html|title=LISA pathfinder overview|publisher=ESA|access-date=23 April 2012}}</ref>

Observations of gravitational waves promise to complement observations in the [[electromagnetic spectrum]].<ref>{{Harvnb|Thorne|1995}}</ref> They are expected to yield information about black holes and other dense objects such as neutron stars and white dwarfs, about certain kinds of [[supernova]] implosions, and about processes in the very early universe, including the signature of certain types of hypothetical [[cosmic string]].<ref>{{Harvnb|Cutler|Thorne|2002}}</ref> In February 2016, the Advanced LIGO team announced that they had detected gravitational waves from a black hole merger.<ref name="Discovery 2016" /><ref name="Abbot" /><ref name="NSF" />