Gravitational waves are caused by the acceleration or movement of massive objects in space. According to Einstein's general theory of relativity, any object with mass or energy can generate gravitational waves as it undergoes acceleration.
When massive objects, such as black holes or neutron stars, orbit each other, merge, or experience other extreme events, they produce gravitational waves. These waves are ripples in the fabric of spacetime itself, propagating outward at the speed of light.
Gravitational waves are similar to waves on the surface of a pond caused by a disturbance. In the case of gravitational waves, the disturbance is the motion of massive objects. As these objects accelerate, they cause the spacetime around them to stretch and compress, creating a ripple effect that travels outward.
These waves carry energy away from the system that created them, causing the objects to gradually lose energy and come closer together. This energy loss in the form of gravitational waves has been observed in binary star systems, where two stars orbit each other.
Gravitational waves were directly detected for the first time in 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO) through the detection of the gravitational waves produced by the merger of two black holes. Since then, several other detections have been made, providing valuable insights into astrophysics, the nature of gravity, and the properties of massive objects in the universe.