In addition to light and electromagnetic waves, there is another type of wave that can travel without a medium, and that is gravitational waves. Gravitational waves are ripples in the fabric of space-time caused by the acceleration or movement of massive objects, such as black holes or neutron stars.
According to Einstein's theory of general relativity, gravitational waves propagate through space-time itself, rather than through a medium like air or water. These waves carry energy away from the source and can be detected and measured using specialized instruments such as interferometers.
Gravitational waves were first directly detected in 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO) through the observation of two merging black holes. This discovery confirmed a major prediction of Einstein's theory and opened up a new field of astronomy known as gravitational wave astronomy.
Unlike light waves, which are part of the electromagnetic spectrum, gravitational waves are related to the curvature of space-time caused by massive objects. They provide valuable insights into astrophysical phenomena, such as the merging of black holes or neutron stars, and offer a unique way to study the universe.