This document summarizes information about gravitational waves and the LIGO observatory. It explains that gravitational waves are ripples in spacetime caused by cosmic events like colliding black holes and neutron stars. The document then discusses LIGO, the Laser Interferometer Gravitational-wave Observatory, which was the first to detect gravitational waves in 2015 from colliding black holes over 1.3 billion years ago. LIGO uses two observatories with long arms to detect the tiny squeezing and stretching of spacetime caused by passing gravitational waves using lasers and sensitive instruments.