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The global electromagnetic resonance phenomenon is named after physicist Winfried Otto Schumann who predicted it mathematically in 1952. Schumann resonances are the principal background in the part of the electromagnetic spectrum [2] from 3 Hz through 60 Hz [3] and appear as distinct peaks at extremely low frequencies around 7.83 Hz (fundamental), 14.3, 20.8, 27.3, and 33.8 Hz.
Typical spectrum of ELF electromagnetic waves in the Earth's atmosphere, showing peaks caused by the Schumann resonances. The Schumann resonances are the resonant frequencies of the spherical Earth–ionosphere cavity. Lightning strikes cause the cavity to "ring" like a bell, causing peaks in the noise spectrum.
Very weak electromagnetic fields disrupt the magnetic compass used by European robins and other songbirds, which use the Earth's magnetic field to navigate. Neither power lines nor cellphone signals are to blame for the electromagnetic field effect on the birds; [ 89 ] instead, the culprits have frequencies between 2 kHz and 5 MHz.
This startling coincidence in value led Maxwell to make the inference that light itself is a type of electromagnetic wave. Maxwell's equations predicted an infinite range of frequencies of electromagnetic waves, all traveling at the speed of light. This was the first indication of the existence of the entire electromagnetic spectrum.
Electromagnetic radiation is commonly referred to as "light", EM, EMR, or electromagnetic waves. [2] The position of an electromagnetic wave within the electromagnetic spectrum can be characterized by either its frequency of oscillation or its wavelength. Electromagnetic waves of different frequency are called by different names since they have ...
An electromagnetic field (also EM field) is a physical field, mathematical functions of position and time, representing the influences on and due to electric charges. [1] The field at any point in space and time can be regarded as a combination of an electric field and a magnetic field .
The weakness of the wave theory was that light waves, like sound waves, would need a medium for transmission. The existence of the hypothetical substance luminiferous aether proposed by Huygens in 1678 was cast into strong doubt in the late nineteenth century by the Michelson–Morley experiment.
Up until the 1940s, astronomers used optical telescopes to observe distant astronomical objects whose radiation reached the earth through the optical window. After that time, the development of radio telescopes gave rise to the more successful field of radio astronomy that is based on the analysis of observations made through the radio window.