Radio transmissions, including the type we know as radio broadcasts, travel much further than an antenna to your receiver. Depending on the strength of the transmission, they can also travel beyond the Earth's atmosphere and into space at the speed of light. They will keep moving at the same speed for thousands or even millions of years, though their strength diminishes with distance travelled. The Inverse Square law says that the intensity of radio waves decreases with the square of the distance from the source.

We have been sending radio waves hither and thither for over 130 years, meaning that some may have reached a distance of 130 light years from the Earth. Of course, they would be much weakened and perhaps impossible to distinguish, should someone have a powerful enough receiver, from the background noise of the universe.

Still, it's fun to think of all those broadcasts, including ones I have been doing for the past six years, spreading out into space and heading off with their human-made content. The first episode of 'What's in Space' is two-thirds to Proxima Centauri. 'Writer's from the Vault' has breached the heliosphere and is whizzing into interstellar space. Who cares if no one is listening, its still a wonderfully romantic notion, split infinitives notwithstanding.