Radio waves travel at the speed of light because they are a form of electromagnetic radiation. Electromagnetic waves, including radio waves, travel through space at a constant speed of approximately 299,792,458 meters per second, which is the speed of light in a vacuum. This speed is a fundamental constant in physics and is the fastest speed at which any information or energy can travel in the universe. Therefore, radio waves, being a type of electromagnetic wave, also travel at the speed of light.