Air: Radio and the Satellite

Wires were fast, but they still had to be laid, mile after physical mile. The next arbitrage removed the wire entirely. A signal no longer needed anything between sender and receiver but open sky, and the fixed infrastructure cost went with it.

Key Milestones

• Radio, 1890s to 1901, Guglielmo Marconi. Marconi's wireless transmissions proved a message could cross an ocean with no cable at all, culminating in a transatlantic signal in 1901.
• Commercial broadcast radio, from 1920, with KDKA in Pittsburgh. Radio moved from a point-to-point signal into a one-to-many broadcast, reaching an entire country at once and giving rise to true mass communication.
• Communications satellites, 1962 to 1978, from Telstar to the first GPS satellite. A relay station in orbit did for global signals what the Persian Royal Road's relay stations had done for a horse messenger, except now at the speed of light.

The Energy, Social, and Economic Impact of Air Transmission

Radio's adoption curve is among the steepest in this history. In 1923, essentially no American household owned a radio; by 1930, 40% did; by 1940, 83%. In under two decades, radio went from a novelty to more common than indoor plumbing had been a generation earlier.

View chart in the full report

Satellites later did to radio what radio had done to the wire: they removed the last physical constraint, the need for a receiving tower within line of sight of a transmitter. A signal bounced off a satellite could reach anywhere on Earth with a clear view of the sky.