Tin-foil hats among the delusional
There have been some people who believe in the actual
utility of tin-foil hats and similar devices. Reasons for
use include preventing abduction by alien beings, or stopping
unpleasant experiences such as hearing voices in one's head.
This draws on the stereotypical image of mind control operating
by means of ESP, microwave radiation or other technological
means. In some cases, belief in tin-foil hats could be a
manifestation of a disorder such as paranoid schizophrenia.
The delusion of "mind control rays" or other
invasive mental activity may seem very real to those afflicted
with severe paranoid delusions, and such persons have been
known to make and wear improvised defences against the imagined
invasion. A placebo effect may even convince the sufferer
that the device actually works. While aluminium foil or
tin-foil is traditional, less fragile materials such as
3M Velostat (a kind of metallised plastic) and metal window-screen
mesh are now more commonly used. Electrical conductivity
is seen as a key quality
There is a small amount of truth or reason to be found
in the tin-foil hat story. A well constructed tin-foil enclosure
would approximate a Faraday cage, reducing the amount of
(notionally harmless) radiofrequency electromagnetic radiation
inside. A common high school physics demonstration involves
placing an AM radio on tinfoil, 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. The effectiveness of the tin-foil hat in stopping
radio waves is greatly reduced by the fact that it is not
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 belong properly to
the realm of pseudoscience.
Tin-foil hats in pop culture
The paranoid centaur Foaly, in Eoin
Colfer's Artemis Fowl series
of books, wears a tin-foil hat to protect
In an episode of The Simpsons,
Bart (while paranoid under the influence
of a drug to cure hyperactivity) wears
a tin-foil hat.
In the film Lovesick, Dudley
Moore plays a psychiatrist who gives
a homeless patient some aluminum foil
to "protect" the patient from
the "mind control rays" his
patient claims are bombarding him.
In Total Recall, the hero
(Douglas Quaid, played by Arnold Schwarzenegger)
wraps a wet towel around his head to
stop outgoing radiowaves from
a transmitter inside his head.
In Signs, the children and
younger brother of the lead character
wear tin-foil hats to prevent their
minds from being read.
- Tin-foil hats are often referenced
on Internet forums.