Changes

The results of his findings were published in 1916 as ''Näherungsweise Integration der Feldgleichungen der Gravitation'' (''"Approximate Integration of the Field Equations of Gravitation"''),<ref>Einstein,  Albert.  "Näherungsweise Integration der Feldgleichungen der Gravitation"; ''Proceedings of the Royal Prussian Academy of Sciences'' (1916), Berlin, Germany.</ref> but serious errors led him to a revision, published in 1918 as ''Über Gravitationswellen'' (''"About Gravitational Waves"'').<ref>Einstein, Albert.  "Über Gravitationswellen"; ''Proceedings of the Royal Prussian Academy of Sciences'' (1918), Berlin, Germany.</ref>

The results of his findings were published in 1916 as ''Näherungsweise Integration der Feldgleichungen der Gravitation'' (''"Approximate Integration of the Field Equations of Gravitation"''),<ref>Einstein,  Albert.  "Näherungsweise Integration der Feldgleichungen der Gravitation"; ''Proceedings of the Royal Prussian Academy of Sciences'' (1916), Berlin, Germany.</ref> but serious errors led him to a revision, published in 1918 as ''Über Gravitationswellen'' (''"About Gravitational Waves"'').<ref>Einstein, Albert.  "Über Gravitationswellen"; ''Proceedings of the Royal Prussian Academy of Sciences'' (1918), Berlin, Germany.</ref>

== The LIGO observations of 2015 ==

== The LIGO observations ==

Because gravitational waves from distant (billions of light years away) phenomena are incredibly faint, detecting them has been a daunting task.  Decades of work have gone into the development of sufficiently sensitive detectors.  In 2015, the [[LIGO]] detectors (one in Hanford, Washington and one in Livingston Louisiana) made the first detection of the waves. <ref>http://www.ligo.org/news/pressreleases.php</ref>

Because gravitational waves from distant (billions of light years away) phenomena are incredibly faint, detecting them has been a daunting task.  Decades of work have gone into the development of sufficiently sensitive detectors.  In 2015, the [[LIGO]] detectors (one in Hanford, Washington and one in Livingston Louisiana) made the first detection of the waves. <ref>http://www.ligo.org/news/pressreleases.php</ref>

A second black hole merger was detected two months later.<ref>http://www.nbcnews.com/science/science-news/it-wasn-t-fluke-scientists-see-black-holes-collide-again-n593156</ref><ref>http://www.cbsnews.com/news/scientists-detect-second-gravitational-wave-einstein-predicted/</ref><ref>https://www.ligo.caltech.edu/news/ligo20160615</ref>

A second black hole merger was detected two months later.<ref>http://www.nbcnews.com/science/science-news/it-wasn-t-fluke-scientists-see-black-holes-collide-again-n593156</ref><ref>http://www.cbsnews.com/news/scientists-detect-second-gravitational-wave-einstein-predicted/</ref><ref>https://www.ligo.caltech.edu/news/ligo20160615</ref>

Here is a comparison of the "chirps" from the two events.  The December event was significantly less powerful that the September one<ref>https://www.ligo.caltech.edu/video/ligo20160615v2</ref>

Here is a comparison of the "chirps" from the two events.  The December event was significantly less powerful that the September one.  It was 1.4 billion light years away.<ref>https://www.ligo.caltech.edu/video/ligo20160615v2</ref>

 

 

A third event was detected in early 2017.  This one was 3 billion light years away.<ref>https://phys.org/news/2017-06-gravitational-insight-black-holes.html</ref>

== The LISA project ==

== The LISA project ==