Terrestrial stationary waves
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Terrestrial stationary waves is a persistent spherical conductor “single-wire” surface wave electrical transmission line phenomenon arising across the Earth's surface by virtue of the highly conductive nature of the earth itself. It was considered by Nikola Tesla to be his most important discovery. Earth's surface constitutes an interface that supports the wave.
On July 3, 1899, Tesla claimed discovery of this new geo-electrical phenomenon, which he said would allow for the transmission of electrical energy around the world.
That communication without wires to any point of the globe is practicable with such apparatus would need no demonstration, but through a discovery which I made I obtained absolute certitude. Popularly explained, it is exactly this: When we raise the voice and hear an echo in reply, we know that the sound of the voice must have reached a distant wall, or boundary, and must have been reflected from the same. Exactly as the sound, so an electrical wave is reflected, and the same evidence which is afforded by an echo is offered by an electrical phenomenon known as a "stationary" wave — that is, a wave with fixed nodal and ventral regions. Instead of sending sound-vibrations toward a distant wall, I have sent electrical vibrations toward the remote boundaries of the earth, and instead of the wall the earth has replied. In place of an echo I have obtained a stationary electrical wave, a wave reflected from afar.
Terrestrial stationary waves were first observed by Tesla and formed the basis for his plans regarding the transmission of electrical energy without wires for the purposes of simultaneous point-to-point telecommunications, broadcasting, and the transmission of electrical power.
The discovery of the stationary terrestrial waves, showing that, despite its vast extent, the entire planet can be thrown into resonant vibration like a little tuning fork; that electrical oscillations suited to its physical properties and dimensions pass through it unimpeded, in strict obedience to a simple mathematical law, has proved beyond the shadow of a doubt that the earth, considered as a channel for conveying electrical energy, even in such delicate and complex transmissions as human speech or musical composition, is infinitely superior to a wire or cable, however well designed.
Schumann resonance hypothesis
It has been suggested this phenomenon arises in the Earth's interior space because of the conductive ionosphere's action as a waveguide. The limited dimensions of the earth cause this waveguide to act as a resonant cavity for electromagnetic waves. The cavity is naturally excited by energy from lightning strikes. The Schumann Resonance is a set of terrestrial stationary waves in the extremely low frequency (ELF) portion of the Earth's electromagnetic field spectrum. Lower frequencies and those at or below longwave bands travel most efficiently as a longitudinal wave and create stationary waves. The ionosphere and the Earth's surface constitute an interface that supports the wave. This resonant cavity is a particular standing wave pattern formed by waves confined in the cavity. The waves correspond to the wavelengths which are reinforced by constructive interference after many reflections from the cavity's reflecting surfaces.
The transfer of electrical energy with small losses in this manner is problematic because the standing wave would occur in the earth-ionosphere cavity, which is too lossy to enable a standing wave of sufficient amplitude to be generated. This limitation is independent of the power of the transmitter. In order for the transmitter to feed power to the receiver as efficiently as it would in a closed low-loss circuit, the power transferred to the receiver should be able to transfer power of the same order of magnitude reciprocally back to the transmitter. This is a necessary condition for the transmitter to “feel” the load connected to the receiver and to supply power to it via the standing wave. In order to do this, the required Q of the earth-ionosphere cavity would have to be on the order of 10^6 or so at the lowest Schumann frequency of about 7.3 Hz. Measurements based on the spectrum of natural electrical radio noise yield a Q of only about 5 to 10. [Henry Bradford]
Regarding this recent notion of power transmission through the earth-ionosphere cavity, a consideration of the earth-ionosphere or concentric spherical shell waveguide propagation parameters as they are known today shows that wireless power transmission by direct excitation of a Schumann cavity resonance mode is not realizable.
The conceptual difficulty with this model is that, at the very low frequencies that Tesla said that he employed (1-50 kHz), earth-ionosphere waveguide excitation, now well understood, would seem to be impossible with the either the Colorado Springs or the Long Island apparatus (at least with the apparatus that is visible in the photographs of these facilities).
Furthermore, the maximum recommended operating frequencies of 25 kHz as specified by Tesla is far above the highest easily observable Schumann resonance mode (the 9th overtone) that exists at approximately 66.4 Hz. Tesla's selection of 25 kHz is wholly inconsistent with the operation of a system that is based upon the direct excitation of a Schumann resonance mode.
Terrestrial spherical-conductor surface wave transmission line
On the other hand, Tesla's concept was that of a global wireless electrical power transmission grid and telecommunications network based upon energy transmission by means of a spherical conductor “single-wire” surface wave transmission line and a propagating TM00 mode. A feasibility study using a sufficiently powerful and properly tuned Tesla coil earth-resonance transmitter is called for.
- THE PROBLEM OF INCREASING HUMAN ENERGY, Century Magazine, June 1900
- TUNED LIGHTNING, English Mechanic and World of Science, March 8, 1907, pp. 107, 108
- Bradford, Henry, "Nikola Tesla On Wireless Energy Transmission" The Schumann Cavity Resonance Hypothesis.
- Spherical Transmission Lines and Global Propagation, An Analysis of Tesla's Experimentally Determined Propagation Model, K. L. Corum, J. F. Corum, Ph.D., and J. F. X. Daum, Ph.D. 1996, p. 10.
- Elmore, Glenn, "Introduction to the Propagating Wave on a Single Conductor," Corridor Systems Inc., 2009.
- Marinčić, Aleksandar, "Research of Nikola Tesla in Long Island Laboratory," International Scientific Conference in Honor of the 130th Anniversary of the Birth of Nikola Tesla, 1986.
- Nikola Tesla (1905). "The Transmission of Electrical Energy Without Wires As A Means Of Furthering World Peace". Electrical World And Engineer January 7: 21–24.