File:Energy transmission by rarefied gas.gif

English: Diagram by inventor Nikola Tesla of his experiment demonstrating the possibility of electric power transmission through the atmosphere. He performed it at his New York laboratory January 28, 1898 before G. D. Seely, a US patent examiner. In 1892 - 1900 Tesla was attempting to develop a wireless power system that could transmit electric power from power plants directly to end users in homes and factories. He believed that due to the decline of air pressure the atmosphere at high altitudes (perhaps 30,000 feet) was electrically conductive, and that if electrodes could be raised to this altitude, perhaps by balloons, this layer could be used to conduct alternating electric current at high voltages for hundreds of miles, from a "transmitter" power station to a "receiver". The ground would serve as the return path for the current.

Tesla performed the above experiment to test this theory. He set up a 50 ft nonconductive 3 inch tube with metal electrodes at either end, evacuated to a low pressure, to simulate the upper atmosphere. The electrode at the left end was connected to a high voltage grounded Tesla coil oscillator (A, C) which applied a radio frequency AC voltage. The electrode at the right end is connected to another grounded resonant transformer (A', C') tuned with a capacitor (M) to the same frequency as the Tesla coil, with its secondary connected to an electrical load (L) such as a light bulb. He found that the voltage from the Tesla coil ionized the gas in the tube, allowing it to conduct electricity, powering the load wirelessly. This method never developed into a practical electric power transmission technology.