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Atmospheric Lensing. A Weapon of Selective Destruction
Steven J. Smith
FW: Jan. 16, 2014
1.1.1
Introduction:
When it comes to war, America portrays it self as a nation of compassion. All to often, it is also a nation paralyzed by political division. Therefore from the American political and military perspective, the best weapon system would not go "bang", or leave smoking holes in the ground to be photographed by news reporters. It would be a weapon of stealth, bringing silent death to the opponent. Preferably without the adversary even knowing they are under attack, or what has caused their demise. This ideal weapon system would have the twin characteristics of being both very selective in it's destructive powers, and able to reach inside buildings or other structures without the need for physical intrusion that might be detected, or worse (from a political viewpoint), publicized. If such a weapon were to exist, it would be prized above all others by the American government, since it would serve the twin goals of "compassionate war", and "avoidance by stealth" of political paralysis and/or retribution. If you think such a weapon system is science fiction, prepare for a shock, because it's already deployed and fully operational.
1.1.2
Refraction:
Refraction is the property of transparent materials to bend light. All transparent materials exhibit this property. Refractive index (sometimes called index of refraction) is a numerical measurement of this property. By definition, the refractive index of free space is set to 1. All transparent materials bend light more than free space, and therefore have a refractive index greater than 1. In other words, given two materials of the same thickness, the material with a higher refractive index will bend light more than the material with a lower refractive index.
1.1.3
Secondary Effects:
In most materials, changes in environmental conditions (temperature, pressure, etc.) cause corresponding shifts in refractive index. This is especially true of gaseous materials where pressure and temperature have a large influence over refractive index. The presence of electromagnetic fields can also influence refractive index, and again, gaseous materials are far more susceptible. Further, the refractive index of any given material will change for different wavelengths of light. A prism is a good example of this last phenomena. White light enters the prism, and since different wavelengths (colors) are bent by differing amounts, a spectrum of colored light emerges from the far side.
1.1.4
The Optical Lens and Mirror:
It is the phenomena of refraction, along with geometric shape that allows a lens to focus light. Given a pair lens, made from identical materials, the lens with greater curvature will have a shorter focal length. Given a pair of lens made from differing materials, and with identical curvature, the lens with a higher refractive index, will have a shorter focal length. In other words, both curvature AND refractive index determine lens focal length. Some types of mirrors and optical filters also depend on refraction for their functionality. Reflection from a non-metallic surface is caused by the difference in refractive index between the air and the reflective material. In some situations, a lens or mirror can form inside a single material, due to a shift in refractive index, caused by environmental conditions in differing parts of the material (1.1.3).
1.2.1
Natural Phenomena:
Those who have lived near the great lakes, may have noticed an odd effect. Sometimes the Sun will cast double shadows of objects. The effect is most noticeable with telephone poles or other tall slender objects. It's caused by a large change in relative humidity, over a short distance. The large change in relative humidity results in an abrupt shift in the refractive index of the atmosphere. Under these conditions, the atmosphere can act as a lens (1.1.3, 1.1.4), thereby creating a second "image" of the Sun, and casting a second and generally much weaker shadow of an object. Another related phenomena is seen under desert conditions. Instead of humidity, intense ground heating supplies the abrupt change in atmospheric refractive index (1.1.4). And again, a double image is created, this time not of the Sun, but of distant objects near the horizon. In both situations, the atmosphere is in effect, acting as a giant lens and/or mirror.
1.2.2
Engineered Phenomena, the Early Years:
It's called Cobra Dane (see fig.1 below) and it's known as an over-the-horizon (OTH) radar. Built on the island of Shemya in Alaska at Eareckson air station, first deployed in 1977, and using a 29m (95 foot) phased array antenna, this radar tracks ICBM launches inside Russia & China. Most people believe that radar, like light, is a line-of-sight phenomena, however this is not always true. The Cobra Dane radar uses the top of Earth's atmosphere as a mirror, to reflect it's radar beam over the horizon and look deep inside Russia & China. To accomplish this seeming feat of magic, first it focuses the radar beam at a spot in the atmosphere, some 50-70 miles above the Russian/Chinese border, causing localized heating in the air (radar is microwave energy after all). This spot then acts as a mirror because the heated air has a slightly different refractive index than the surrounding air (1.1.3, 1.1.4, 1.2.1). The atmospheric mirror can then be use to by the radar to "see" around the curvature of the Earth. Also, by selective heating, a curved mirror can be produced, thereby magnifying the view "seen" by the radar. Of course every so often the radar must reheat the atmosphere in order to sustain the mirror.
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