Editing Gravity (section)

===Gravitational radiation===
{{Main|Gravitational wave}}
[[File:LIGO Hanford aerial 05.jpg|alt=LIGO Hanford Observatory|thumb|The [[LIGO]] Hanford Observatory located in Washington, United States, where gravitational waves were first observed in September 2015]]
General relativity predicts that energy can be transported out of a system through gravitational radiation. The first indirect evidence for gravitational radiation was through measurements of the [[Hulse–Taylor binary]] in 1973. This system consists of a pulsar and neutron star in orbit around one another. Its orbital period has decreased since its initial discovery due to a loss of energy, which is consistent for the amount of energy loss due to gravitational radiation. This research was awarded the [[Nobel Prize in Physics]] in 1993.<ref name="npp1993">{{cite web |title=The Nobel Prize in Physics 1993 |publisher=[[Nobel Foundation]] |url=https://www.nobelprize.org/prizes/physics/1993/press-release/ |date=13 October 1993 |quote=for the discovery of a new type of pulsar, a discovery that has opened up new possibilities for the study of gravitation |access-date=22 December 2023 |archive-date=10 August 2018 |archive-url=https://web.archive.org/web/20180810182047/https://www.nobelprize.org/nobel_prizes/physics/laureates/1993/press.html |url-status=live }}</ref>

The first direct evidence for gravitational radiation was measured on 14 September 2015 by the [[LIGO]] detectors. The gravitational waves emitted during the collision of two black holes 1.3 billion light years from Earth were measured.<ref name='Clark 2016'>{{Cite web|title = Gravitational waves: scientists announce 'we did it!'{{snd}}live|url = https://www.theguardian.com/science/across-the-universe/live/2016/feb/11/gravitational-wave-announcement-latest-physics-einstein-ligo-black-holes-live|website = the Guardian|date = 11 February 2016|access-date = 11 February 2016|first = Stuart|last = Clark|archive-date = 22 June 2018|archive-url = https://web.archive.org/web/20180622055957/https://www.theguardian.com/science/across-the-universe/live/2016/feb/11/gravitational-wave-announcement-latest-physics-einstein-ligo-black-holes-live|url-status = live}}</ref><ref name="Discovery 2016">{{cite journal |title=Einstein's gravitational waves found at last |journal=Nature News |url=http://www.nature.com/news/einstein-s-gravitational-waves-found-at-last-1.19361 |date=11 February 2016 |last1=Castelvecchi |first1=Davide |last2=Witze |first2=Witze |doi=10.1038/nature.2016.19361 |s2cid=182916902 |access-date=11 February 2016 |archive-date=12 February 2016 |archive-url=https://web.archive.org/web/20160212082216/http://www.nature.com/news/einstein-s-gravitational-waves-found-at-last-1.19361 |url-status=live }}</ref> This observation confirms the theoretical predictions of Einstein and others that such waves exist. It also opens the way for practical observation and understanding of the nature of gravity and events in the Universe including the Big Bang.<ref>{{cite web|title=WHAT ARE GRAVITATIONAL WAVES AND WHY DO THEY MATTER?|date=13 January 2016 |url=http://www.popsci.com/whats-so-important-about-gravitational-waves|publisher=popsci.com|access-date=12 February 2016|archive-date=3 February 2016|archive-url=https://web.archive.org/web/20160203130600/http://www.popsci.com/whats-so-important-about-gravitational-waves|url-status=live}}</ref> [[Neutron star]] and [[black hole]] formation also create detectable amounts of gravitational radiation.<ref name="PhysRev2017">{{cite journal |last1=Abbott |first1=B. P. |display-authors=etal. |collaboration=[[LIGO Scientific Collaboration]] & [[Virgo interferometer|Virgo Collaboration]] |title=GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral |journal=[[Physical Review Letters]] |date=October 2017 |volume=119 |issue=16 |pages=161101 |doi=10.1103/PhysRevLett.119.161101 |pmid=29099225 |doi-access=free |arxiv=1710.05832 |url=http://www.ligo.org/detections/GW170817/paper/GW170817-PRLpublished.pdf |bibcode=2017PhRvL.119p1101A |access-date=28 September 2019 |archive-date=8 August 2018 |archive-url=https://web.archive.org/web/20180808012441/https://www.ligo.org/detections/GW170817/paper/GW170817-PRLpublished.pdf |url-status=live }}</ref> This research was awarded the Nobel Prize in Physics in 2017.<ref>{{cite web|title=Nobel prize in physics awarded for discovery of gravitational waves|url=https://www.theguardian.com/science/2017/oct/03/nobel-prize-physics-discovery-gravitational-waves-ligo|website=the Guardian|date=3 October 2017|access-date=3 October 2017|last1=Devlin|first1=Hanna|archive-date=3 October 2017|archive-url=https://web.archive.org/web/20171003102211/https://www.theguardian.com/science/2017/oct/03/nobel-prize-physics-discovery-gravitational-waves-ligo|url-status=live}}</ref>