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The Body Electric
outward-flowing aspect. However, the two terms refer to the same phe-
nomenon and are interchangeable. The only meaningful distinction is
between static and time-varying fields.
Each energy wave consists of an electric field and a magnetic field at
right angles to each other, and both at right angles to the direction the
wave is traveling. The number of waves formed in one second is the
frequency; the distance the energy travels (at the speed of light) during
one oscillation is its wavelength. The higher the frequency, the shorter
the wavelength, and vice versa.
EMR spans an enormous range of frequencies. The shortest gamma
rays, a tenth of a billionth of a millimeter long, vibrate sextillions of
times a second. These, along with X rays and the shortest ultraviolet
wavelengths, are termed ionizing radiation, because their high photonic
energy can knock electrons away from atoms, creating highly reactive
ions where they don't belong. Much of the damage from nuclear radia-
tion is caused in this way. All lower frequencies, beginning with the
longer ultraviolet wavelengths, are nonionizing.
Next comes the only energy we can see—the narrow band of visible
light vibrating hundreds of trillions of times a second—and then the
infrared waves we feel as radiant heat. Below these lie the waves we've
harnessed for communication. They begin with microwaves (MW),
whose frequency is measured in gigahertz or megahertz—billions or
millions of cycles per second—and extend through the radio frequencies
(RF) down to ELF waves, whose frequency converges on zero. The MW
and RF spectrum is arbitrarily broken up into a further alphabet of ex-
tremely high, superhigh, ultrahigh, very high, high, medium, low,
very low, and extremely low frequencies (EHF, SHF, UHF, VHF, HF,
MF, LF, VLF, and ELF respectively). As we have seen, ELF waves ap-
proximate the dimensions of the earth; at 10 hertz one wave is about
18,600 miles long.
Except for light and infrared heat, we can't perceive any of these ener-