"Etheric force" and the early stages of radio

In 1875, Edison and his team were experimenting with new ways to improve the telegraph, when they noticed a strange phenomenon happening between the machines.

Each time the device vibrated, metal objects that came in contact with it would generate sparks. Edison became curious about this reaction, and determined that it must be the workings of an unknown force, which his team dubbed "etheric force."

He then developed an etheroscope, a device that would measure different ways this force could be transmitted and observe the sparks more closely, but he never quite understood what it meant.

Eventually, it became known that his telegraph was actually producing radio frequency electromagnetic waves, which later become the basis for the development of radio technology.