Tin-foil hat
Encyclopedia
A tin foil hat is a piece of headgear
made from one or more sheets of aluminum foil or similar material. Alternatively it may be a conventional hat lined with foil. One may wear the hat in the belief that it acts to shield the brain
from such influences as electromagnetic field
s, or against mind control
and/or mind reading
; or attempt to limit the transmission of voices directly into the brain.
The concept of wearing a tin foil hat for protection from such threats has become a popular stereotype
and term of derision; the phrase serves as a byword for paranoia
and persecutory delusions
, and is associated with conspiracy theorists
.
, "The Tissue-Culture King", first published in 1927, in which the protagonist discovers that "caps of metal foil" can be used to block the effects of telepathy.
Since then, the usage of the term has been associated with paranoia
and conspiracy theories
. The supposed reasons for their use include the prevention of perceived harassment from governments, spies or paranormal beings. These draw on the stereotypical images of mind control operating by ESP or technological means, like microwave radiation
; belief in their necessity is popularly associated with paranoia
.
, reducing the amount of (typically harmless) radiofrequency electromagnetic radiation
inside. A common high school physics demonstration involves placing an AM radio on tin 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 tin foil, as dictated by the skin depth
, the distance the radiation can propagate in a particular non-ideal conductor
. For half-millimeter-thick tin foil, radiation above about 20 kHz (i.e., including both AM and FM bands) would be partially blocked, although tin foil is not sold in this thickness, so numerous layers of tin foil would be required to achieve this effect.
The effectiveness of the tin foil hat as electromagnetic shielding
for stopping radio waves is greatly reduced by it not being a complete enclosure. Placing an AM radio under a metal bucket without a conductive layer underneath demonstrates the relative ineffectiveness of such a setup. Indeed, because the effect of an ungrounded Faraday cage is to partially reflect the incident radiation, a radio wave that is incident on the inner surface of the hat (i.e., coming from underneath the hat-wearer) would be reflected and partially 'focused' towards the user's brain. While tin foil hats may have originated in some understanding of the Faraday cage effect, the use of such a hat to attenuate radio waves belongs properly to the realm of pseudoscience
.
A study by graduate students at MIT determined that a tin foil hat could either amplify or attenuate incoming radiation depending on frequency; the effect was observed to be roughly independent of the relative placement of the wearer and radiation source. At GHz wavelengths, the skin depth is less than the thickness of even the thinnest foil.
Tin foil hats are seen by some as a protective measure against the effects of electromagnetic radiation
(EMR). Despite some allegations that EMR exposure has negative health consequences, at this time, no link has been verifiably proven between the radio-frequency EMR that tin foil hats are meant to protect against and subsequent ill health.
range, hearing them as sounds. The perceived source of induced sound is located inside of or directly behind the head of the recipient, regardless of the location of the transmitter. The effect is believed to be caused by thermoelastic expansion of the brain exposed to microwaves.
During the Cold War
, electromagnetic hearing was clinically studied in the United States
for applications including covert message transmission and use as a non-lethal weapon. As a declassified National Ground Intelligence Center
document points out:
In 1962, Allan H. Frey
discovered that reception of the induced sound can be blocked by a patch of wire mesh (not foil) placed above the temporal lobe
.
s were granted by the United States Patent and Trademark Office
for various mind control methods, including "nervous system excitation" (1968), and remotely monitoring and "altering brain waves" (1974).
Headgear
Headgear, headwear or headdress is the name given to any element of clothing which is worn on one's head.Headgear serve a variety of purposes:...
made from one or more sheets of aluminum foil or similar material. Alternatively it may be a conventional hat lined with foil. One may wear the hat in the belief that it acts to shield the brain
Human brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...
from such influences as electromagnetic field
Electromagnetic field
An electromagnetic field is a physical field produced by moving electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction...
s, or against mind control
Mind control
Mind control refers to a process in which a group or individual "systematically uses unethically manipulative methods to persuade others to conform to the wishes of the manipulator, often to the detriment of the person being manipulated"...
and/or mind reading
Telepathy
Telepathy , is the induction of mental states from one mind to another. The term was coined in 1882 by the classical scholar Fredric W. H. Myers, a founder of the Society for Psychical Research, and has remained more popular than the more-correct expression thought-transference...
; or attempt to limit the transmission of voices directly into the brain.
The concept of wearing a tin foil hat for protection from such threats has become a popular stereotype
Stereotype
A stereotype is a popular belief about specific social groups or types of individuals. The concepts of "stereotype" and "prejudice" are often confused with many other different meanings...
and term of derision; the phrase serves as a byword for paranoia
Paranoia
Paranoia [] is a thought process believed to be heavily influenced by anxiety or fear, often to the point of irrationality and delusion. Paranoid thinking typically includes persecutory beliefs, or beliefs of conspiracy concerning a perceived threat towards oneself...
and persecutory delusions
Persecutory delusions
Persecutory delusions are a delusional condition in which the affected person believes they are being persecuted...
, and is associated with conspiracy theorists
Conspiracy theory
A conspiracy theory explains an event as being the result of an alleged plot by a covert group or organization or, more broadly, the idea that important political, social or economic events are the products of secret plots that are largely unknown to the general public.-Usage:The term "conspiracy...
.
Origin of concept
The concept was mentioned in a science fiction story by Julian HuxleyJulian Huxley
Sir Julian Sorell Huxley FRS was an English evolutionary biologist, humanist and internationalist. He was a proponent of natural selection, and a leading figure in the mid-twentieth century evolutionary synthesis...
, "The Tissue-Culture King", first published in 1927, in which the protagonist discovers that "caps of metal foil" can be used to block the effects of telepathy.
Since then, the usage of the term has been associated with paranoia
Paranoia
Paranoia [] is a thought process believed to be heavily influenced by anxiety or fear, often to the point of irrationality and delusion. Paranoid thinking typically includes persecutory beliefs, or beliefs of conspiracy concerning a perceived threat towards oneself...
and conspiracy theories
Conspiracy theory
A conspiracy theory explains an event as being the result of an alleged plot by a covert group or organization or, more broadly, the idea that important political, social or economic events are the products of secret plots that are largely unknown to the general public.-Usage:The term "conspiracy...
. The supposed reasons for their use include the prevention of perceived harassment from governments, spies or paranormal beings. These draw on the stereotypical images of mind control operating by ESP or technological means, like microwave radiation
Microwave auditory effect
The microwave auditory effect, also known as the microwave hearing effect or the Frey effect, consists of audible clicks induced by pulsed/modulated microwave frequencies. The clicks are generated directly inside the human head without the need of any receiving electronic device...
; belief in their necessity is popularly associated with paranoia
Paranoia
Paranoia [] is a thought process believed to be heavily influenced by anxiety or fear, often to the point of irrationality and delusion. Paranoid thinking typically includes persecutory beliefs, or beliefs of conspiracy concerning a perceived threat towards oneself...
.
Scientific basis
The notion that a tin 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 tin foil enclosure would approximate a Faraday cageFaraday cage
A Faraday cage or Faraday shield is an enclosure formed by conducting material or by a mesh of such material. Such an enclosure blocks out external static and non-static electric fields...
, reducing the amount of (typically harmless) radiofrequency electromagnetic radiation
Radio waves
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies from 300 GHz to as low as 3 kHz, and corresponding wavelengths from 1 millimeter to 100 kilometers. Like all other electromagnetic waves,...
inside. A common high school physics demonstration involves placing an AM radio on tin 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 tin foil, as dictated by the skin depth
Skin effect
Skin effect is the tendency of an alternating electric current to distribute itself within a conductor with the current density being largest near the surface of the conductor, decreasing at greater depths. In other words, the electric current flows mainly at the "skin" of the conductor, at an...
, the distance the radiation can propagate in a particular non-ideal conductor
Electrical conductor
In physics and electrical engineering, a conductor is a material which contains movable electric charges. In metallic conductors such as copper or aluminum, the movable charged particles are electrons...
. For half-millimeter-thick tin foil, radiation above about 20 kHz (i.e., including both AM and FM bands) would be partially blocked, although tin foil is not sold in this thickness, so numerous layers of tin foil would be required to achieve this effect.
The effectiveness of the tin foil hat as electromagnetic shielding
Electromagnetic shielding
Electromagnetic shielding is the process of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive and/or magnetic materials. Shielding is typically applied to enclosures to isolate electrical devices from the 'outside world' and to cables to isolate...
for stopping radio waves is greatly reduced by it not being a complete enclosure. Placing an AM radio under a metal bucket without a conductive layer underneath demonstrates the relative ineffectiveness of such a setup. Indeed, because the effect of an ungrounded Faraday cage is to partially reflect the incident radiation, a radio wave that is incident on the inner surface of the hat (i.e., coming from underneath the hat-wearer) would be reflected and partially 'focused' towards the user's brain. While tin foil hats may have originated in some understanding of the Faraday cage effect, the use of such a hat to attenuate radio waves belongs properly to the realm of pseudoscience
Pseudoscience
Pseudoscience is a claim, belief, or practice which is presented as scientific, but which does not adhere to a valid scientific method, lacks supporting evidence or plausibility, cannot be reliably tested, or otherwise lacks scientific status...
.
A study by graduate students at MIT determined that a tin foil hat could either amplify or attenuate incoming radiation depending on frequency; the effect was observed to be roughly independent of the relative placement of the wearer and radiation source. At GHz wavelengths, the skin depth is less than the thickness of even the thinnest foil.
Tin foil hats are seen by some as a protective measure against the effects of electromagnetic radiation
Electromagnetic radiation
Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...
(EMR). Despite some allegations that EMR exposure has negative health consequences, at this time, no link has been verifiably proven between the radio-frequency EMR that tin foil hats are meant to protect against and subsequent ill health.
Electromagnetic hearing
Humans are able to detect modulated radio-frequency electromagnetic signals in the microwaveMicrowave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
range, hearing them as sounds. The perceived source of induced sound is located inside of or directly behind the head of the recipient, regardless of the location of the transmitter. The effect is believed to be caused by thermoelastic expansion of the brain exposed to microwaves.
During the Cold War
Cold War
The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...
, electromagnetic hearing was clinically studied in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
for applications including covert message transmission and use as a non-lethal weapon. As a declassified National Ground Intelligence Center
National Ground Intelligence Center
The National Ground Intelligence Center is part of the United States Army Intelligence and Security Command. The NGIC provides scientific and technical intelligence and general military intelligence on foreign ground forces in support of the warfighting commanders, force and material developers,...
document points out:
In 1962, Allan H. Frey
Allan H. Frey
Allan H. Frey is an American neuroscientist known for his research and writing during the Cold War on the nature of the microwave auditory effect, also called the "Frey effect". He worked at General Electric's Advanced Electronics Center at Cornell University...
discovered that reception of the induced sound can be blocked by a patch of wire mesh (not foil) placed above the temporal lobe
Temporal lobe
The temporal lobe is a region of the cerebral cortex that is located beneath the Sylvian fissure on both cerebral hemispheres of the mammalian brain....
.
Other mind control methods
A number of patentPatent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....
s were granted by the United States Patent and Trademark Office
United States Patent and Trademark Office
The United States Patent and Trademark Office is an agency in the United States Department of Commerce that issues patents to inventors and businesses for their inventions, and trademark registration for product and intellectual property identification.The USPTO is based in Alexandria, Virginia,...
for various mind control methods, including "nervous system excitation" (1968), and remotely monitoring and "altering brain waves" (1974).
See also
- Electromagnetic radiation and health
- List of headgear
- Tinfoil
- VelostatVelostatVelostat is a packaging material impregnated with carbon black to make it electrically conductive. It is used for the protection of items or devices that are prone to damage from electrostatic discharge. It was developed by Custom Materials, now part of 3M....
External links
- Do tinfoil helmets provide adequate protection against mind control rays? – from The Straight Dope
- Tinfoil hats attract mind-control signals, boffins learn
- Mind Games -Washington Post
- On the Effectiveness of Aluminium Foil Helmets: An Empirical Study, Electrical Engineering and Computer Science department, MIT