Index
      
      Gravitational
                Waves
                
          
          
          
           
        
      
      
      Gravitational waves are disturbances in the curvature of
      spacetime, generated by accelerated masses,
      that propagate as waves outward from their source at the speed of
      light.
      They were proposed by Henri Poincaré in 1905
       and subsequently predicted in 1916 by Albert Einstein on the
      basis of his general theory of relativity.
      On 11 February 2016, the LIGO and Virgo Scientific Collaboration
      announced
      they had made the first direct observation of gravitational waves.
      The observation was made five months earlier, on 14 September
      2015,
      using the Advanced LIGO detectors. The gravitational waves
      originated from a pair of merging black holes.