Radio Fundamentals Radio waves are simply a form of electromagnetic radiation, like sunlight, X-rays, cosmic rays, or infrared waves. The difference is that each has a different frequency and therefore different characteristics.
All electromagnetic radiation travels in straight lines at the speed of light.
Earth is now surrounded by a sphere of radio and TV signals about 80 light years in diameter and expanding at warp speed. Because we on earth began radio broadcasting about 80 years ago. Something out there is listening to us. Real science fiction. Appropriately these layers are called the ionisphere.