Audio Guide：

Albert Einstein predicted the phenomenon of gravitational waves in his general theory of relativity. Gravitational waves are ripples caused by spacetime fluctuations. Gravitational waves do not interact with matter in their path and are therefore able to accurately transmit information from deep space. However, they are very hard to detect because they are so faint. On February 11, 2016, the Laser Interferometer Gravitational-Wave Observatory, or LIGO, detected gravitational waves from the collision of two black holes and broke new grounds for the emerging field of gravitational-wave astronomy.