Transcript Document

The Sphinx: An Illusion with Mirrors
Richard Gelderman, Michael Carini, Keith Andrew & Alexander Barzilov
Western Kentucky University, Bowling Green, KY 42101-1077
Torso on a Pole: Our Version of the Illusion
History of the Sphinx Illusion
For our team’s Dematerialization we modified the classic
Sphinx Illusion. The person in the box is introduced to the
audience, sitting cross legged in a box. After this person
annoys the the wizard once too many times, the wizard
dematerializes the man’s lower body.
The expression "it's all done with mirrors" is largely due to
popularity in the mid-1800’s of the Sphinx Illusion. This
illusion wasinvented in 1865 by Thomas Tobin, a science
lecturer at the Royal Polytechnic Institution; and made
famous by English magician Colonel Stodare.
In the Sphinx Illusion, the magician greet the audience with
a tale about during her travels in the deserts of Egypt she
came upon an ancient statue of the Sphinx and the
miraculous coming to life of the Sphinx’s head. The
magician continues to set the scene by relating the tale of
how a curse placed upon an unfortunate priestess by the
wrathful pharaoh Rameses, imprisoning the priestess in the
stone statue of a Sphinx. The magician explains that this
head is now in the box in her hand. Walking to the table she
places the box on the table and after some impressive
words, presto! the Sphinxian head appears. The bodiless
head proceeds to converse with the magician.
Figure 1: Schematic explanation of how the optical
illusion created by the double-mirror creates the classic
Sphinx Illusion.
Initially, the entire person was going to dematerialize; but
we could not get either a limber enough volunteer or a big
enough set of box and mirrors. Our compromise was to
only dematerialize the lower portion of the person, using
mirrors and the small cylinder upon which the box is
mounted. Having the box high allowed for less sensitivity
with the sight lines and gave a place for his legs to go. We
chose to use vertical stripes for the material on the sides of
the box. Any mismatches in the pattern were less noticeable
without complicated or hard to reproduce patterns.
The original trick awed audiences for many nights and
defied explanation until one night a keen observer noted
finger-prints on what proved to be a mirror.
Physical Explanation of the Illusion
Figure 2: Modern example of a table and doubleThe science behind this wizardry is simply the physical
properties of reflected light. The explanation for this
famous illusion is illustrated in Figure 1. If two mirrors are
positioned at right angles with their apex directly behind
the table leg, the mirrors will reflect the sides of the box
and create a false back.
mirror used with the Sphinx Illusion. In this image the
bottom edges of the mirrors can be seen against the rug.
However, when the shag carpet is fluffed up to hide the
edges of the mirrors and the lights are dimmed, the
illusion is stunning.
In reality the head belongs to a body extending downward
from the table-top. This kneeling human being is concealed
from the audience by two very clean plate-glass mirrors,
shown as “M” in sketch at the righthand side of Figure 1.
The walls, floor, and ceiling of the box-like recess in which
the table is placed are covered with the same material.
When properly arranged, the mirrors reflect light from side
walls to form virtual images that the audience assumes to
be portions of the rear wall. Thus the table appears to be
open underneath.
The body associated with the talking head can be hidden in
the V-shaped space behind the mirrors, visible in Figure 2.
The front table leg itself masks where the mirrors are
joined. The audience rarely notices the absence of a fourth
leg, if it noticed this at all assumed the back leg was
obscured by the front leg.
References:
Hiding the Elephant: How Magicians Invented the Impossible and
Learned to Disappear, J. Steinmeyer, 2003, Carroll & Graf
Publishers.
The Haunted Physics Lab, T.H.Zepf, in The Physics Teacher,
October 2004, Volume 42, Issue 7, pp. 404-408.
Our illusion utilizes mirrors that can be swung into place
while a swirl of the wizard’s cape has blocked the
audience’s view. As with the Sphinx Illusion, the body is
hidden in the V-shaped space behind the mirrors, making it
appear that he is just a head and torso. The pole masks
where the mirrors are joined. The basic explanation for our
variation is illustrated below.
Figure 3: Examples of the modern Head on a Platter
Illusion, a variation of the Sphinx Illusion.