Radio waves are a type of electromagnetic radiation with a very long wavelength that are emitted by sources that include astronomical objects and television and radio transmitters. Radio waves, the longest wavelengths in the electromagnetic spectrum, typically carry radio, television and cellphone signals.
Radio waves originate in processes that create electromagnetic radiation, including nuclear reactions occurring at the heart of a star, and alternately applying and removing electrical current to a wire can induce them. Regularly applying and removing electrical current makes radio signal transmission possible. The application of current to a wire creates an electromagnetic field that emits a wave; upon removal of the current, the disappearance of the field emits a new wave. Application to and removal of current from the wire at regular intervals creates a succession of waves with a stable frequency.
Radio astronomy, a branch of astronomy that deals purely with the radio portion of the electromagnetic spectrum, observes and analyzes radio waves emitted by objects in space. Radio waves emitted by a given object provide information about the object's movement and the materials from which it is composed. A key advantage of radio astronomy is that, unlike astronomy that relies on visible light, negative weather does not influence observations.