Have You Ever Been Called ''Tin Foil Hat'' By Skeptics and The Uninformed..?

Man, wearing a tin foil hat (aluminium)

A tin foil hat is a piece of headgear made from one or more sheets of aluminium foil
or similar material. Alternatively it may be a conventional hat lined
with foil. One may wear the hat in the belief that it shields the brain from electromagnetic fields; to prevent mind control and/or mind reading; or 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.

Origin of concept

The concept was mentioned in a science fiction story by Julian Huxley,
"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.^[1]

Dominic Howard from Muse wearing a tin foil hat

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.^[2]

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.^[3] A well-constructed tin 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 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-millimetre-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.^[4]

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 attenuate incoming radiation
depending on frequency. At WIFI frequencies - 2.4 GHz is attenuated by
up to 90dB; the effect was observed to be roughly independent of the
relative placement of the wearer and radiation source.^[5] At GHz wavelengths, the skin depth is less than the thickness of even the thinnest foil.^[6]

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,^[7]
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.^[8]