Radio waves travel at a velocity that is equal to the speed of light traveling in a vacuum, which is 186,282 miles per second. Top speed is only possible in empty space; passing through transparent liquids and solids like crystals cause waves to bend, which slows down their speed.
The unit that measures radio waves, hertz, was named after Heinrich Hertz, who first proved the existence and speed of radio waves. Hertz also proved that radio waves are actually a form of light. Albert Einstein and other scientists have established that nothing with mass can travel as fast as light speed, but light and sound waves sometimes travel slower.