Einstein himself did not explicitly predict the existence of gravitational waves. The concept of gravitational waves was actually deduced by others based on Einstein's theory of general relativity.
In 1916, Einstein published his theory of general relativity, which described gravity as the curvature of spacetime caused by mass and energy. Although his equations allowed for the possibility of gravitational waves, Einstein himself was initially skeptical of their existence and believed they were merely a mathematical artifact.
It was not until the 1960s that scientists, including Joseph Weber, began conducting experiments to directly detect gravitational waves. However, their early attempts did not provide conclusive evidence.
It was in the 1970s and 1980s that the groundwork for gravitational wave detection was established by scientists such as Kip Thorne, Rainer Weiss, and Ronald Drever. They developed the concept and design of interferometric detectors, such as the Laser Interferometer Gravitational-Wave Observatory (LIGO), which became instrumental in the first direct detection of gravitational waves.
Finally, in 2015, the LIGO collaboration announced the first direct detection of gravitational waves, confirming their existence and providing strong support for Einstein's theory of general relativity.