A tin foil hat is a hat made from one or more sheets of aluminum foil, or a piece of conventional headgear lined with foil, worn in the belief it shields the brain from threats such as electromagnetic fields, mind control, and mind reading. The notion of wearing homemade headgear for such protection has become a popular stereotype and byword for paranoia, delusions, and belief in pseudo science and conspiracy theories.
One story states that the tin foil hat has its origins tied into the opposition of freemasonry when it began in 1717. As the story goes, non Freemasons were suspicious of the brotherhood and believed that the Mason were using forms of mind control on them. They began their own fraternity, called the “Mad Hatters” and upon learning about the protective properties of aluminum foil, they created their own hats made of this substance.
The concept of a foil hat for protection against interference of the mind was mentioned in a science fiction short story by Julian Huxley, "The Tissue-Culture King", first published in 1927, in which the protagonist discovers that "caps of metal foil" can block the effects of telepathy.
The notion that a metal foil hat can significantly reduce the intensity of incident radio frequency radiation on the wearer's brain has some scientific validity, as the effect of strong radio waves has been documented for quite some time. A well-constructed aluminum foil enclosure would approximate a Faraday cage, reducing the amount of (typically harmless) radiofrequency electromagnetic radiation passing through to the interior of the structure. A common high school physics demonstration involves placing an AM radio on aluminum foil, and then covering the radio with a metal bucket. This leads to a noticeable reduction in signal strength. The efficiency of such an enclosure in blocking such radiation depends on the thickness of the foil, as dictated by the skin depth, the distance the radiation can propagate in a particular non-ideal conductor. For half-millimetre-thick aluminum foil, radiation above about 20 kHz (i.e., including both AM and FM bands) would be partially blocked, although aluminum foil is not sold in this thickness, so numerous layers of foil would be required to achieve this effect.
The possibilities of Freemason mind control, as well as the malfeasance by African Heads of State, have both been discounted. But that still leaves “The Government” and “The Corporations.” At MIT, experiments were conducted to get to the bottom of the subject using cold, hard math.
Tests were conducted over a spectrum ranging from 10 KHz to 3 GHz. Results were tabulated for three different specifications of tinfoil hats: the classical, the fez and the centurion. Measurements were made at the subjects’ frontal, occipital and parietal lobes both with and without each type of helmet.
Similar results were obtained for all of the three helmet types, and each one did provide 20dB of attenuation at 1.5 GHz when measured against signal levels that were recorded when the wearer’s head was bare. There was little attenuation noted anywhere else in the spectrum.
But, shockingly, a 20dB amplification was noted at 1.2 GHz, and a glaring 30dB amplification was noted at 2.6 GHz. The former range is what the government says it uses for GPS, and the 2.6 GHz band is what corporations use for cellular communications. For conspiracy theorists, the data indicates that tinfoil hats may actually make government and corporate mind-reading easier, rather than more difficult.
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