One of Nikola Tesla’s major discoveries in the field of electricity was terrestrial stationary waves deriving from natural lightning discharges.
In 1899, at Colorado Springs one night during a huge thunderstorm, Tesla was witness to thousands of lightning discharges within two hours. He recorded in great detail the many branches each flash of lightning and their sizes.
As the storm began to fade away, Tesla connected a rotating coherer (a device he used for telegraphy in New York prior to his visit in both wireless signaling and in investigating the properties of x-rays) to the ground along with a plate above the ground. A condenser was also used to magnify the effects transmitted through the ground. His device was adjusted as the storm gradually dissipated, and he continued to adjust its sensitivity as the distance was extended. The receiver would continue to react even though the storm was up to 50 miles away based solely on sound waves.
After the device stopped responding, Tesla deduced that the storm had passed at a distance too far away to record additional data points. Suddenly though, the receiver began to record again and surprisingly to Tesla, the recordings were also increasing in strength even though the storm had moved on to a point that was essentially out of sight. The device would then cease again for a bit, only to begin functioning once again. Tesla would continue adjusting the sensitivity on the coherer and the same results would occur. The device would continue playing after small intervals of time. To Tesla, this was the most wonderful and intriguing experience because it clearly showed the existence of terrestrial stationary waves. This discovery proved that the Earth is responsive to electrical vibrations of definite pitch just as a tuning fork to certain waves of sound, and these particular electrical vibrations are capable of powerfully exciting the Globe. It proved that power could indeed be transmitted through the Earth to far distances utilizing his oscillator (later known as his Magnifying Transmitter).
Tesla's ultimate plan was to throw the earth into resonant vibration similar to a tuning fork. He would strike the earth with his oscillator sending electrical ripples around the surface of the Earth, and when the energy would return he would again strike it simultaneously in vibrational process known as constructive interference (when two waves overlap in such a way that they combine to create a larger wave). This is NOT electromagnetic radiation such as with visible light and radio waves. This was nothing like the radio antennas we use today. Tesla's goal was actually to minimize the electromagnetic radiation from the system as much as possible by containing 95 percent of the energy in a localized standing wave confined to the Earth, the opposite notion of traditional radio antennas which give off 90 percent of radiation through the air. Tesla measured these electrical ripples traveling around the entire circumference of the earth moving faster than the speed of light, specifically pi divided by 2 times the speed of light (1.57c).
“By this invention every live part of Mother Earth’s body would be brought into action. Energy will be collected all over the globe in amounts small or large, as it may exist, ranging from a fraction of one to a few horse power or more. Every waterfall can be utilized, every coal field made to produce energy to be transmitted to vast distances, and every place on earth can have power at small cost. One of the minor uses might be the illumination of isolated homes. We could light houses all over the country by means of vacuum tubes operated by high frequency currents. We could keep the clocks of the United States going and give every one exact time; we could turn factories, machine shops and mills, small or large, anywhere, and I believe could also navigate the air." –Nikola Tesla