Today, the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) is expected to announce a monumental discovery that is 100 years in the making.  Theorized by Einstein’s general relativity in 1915, gravitational waves are ripples in space-time, similar to sound waves, but much tinier.  The search has been ongoing for decades, with no results.  Until now. LIGO has the most sensitive gravitational wave detector ever conceived – in two interferometer facilities in Livingston, Louisiana and Hanford, Washington.  They use a laser split along two axes to give an in-phase beam.  If gravitational waves along one of the axes affect the beam, it...