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Seeing
through
Raj
Kaushik
HUMAN beings have always longed to become invisible
to others. Philosophers and thinkers have been imagining about human
invisibility for centuries.
In ancient times, it was thought
that rays emitted from one’s eyes enabled people to see things.
“Concentration and meditation can deactivate the rays emitted from
the eyes of the observer and thus make the body of a yogi
invisible,” wrote Patanjali, in Yoga Sutra. According to him
invisibility had to do with the power of mind over matter.
In
Greek mythology, a special helmet renders its wearer invisible. This
helmet of invisibility is most often linked with the underworld god,
Hades, also referred to as Pluto.
Shamanism, or the ability to
vanish, has been discussed in many cultures, for example, by the
aboriginals of Australia, the original people of America, and those
who live in the polar regions.
In the late 19th century novel,
The Invisible Man by HG Wells, Jack Griffin, a chemist, invents an
amazing serum that can render both objects and humans invisible. In
Shekhar Kapoor’s Mr India, when the hero puts on a wristband, it
makes him invisible. Also, in JRR Tolkien’s trilogy, The Lord of the
Rings, any person who wears the ring becomes invisible immediately.
Becoming invisible with the help of a device is no longer
possible only in the realm of ancient mythical scriptures or
science-fiction movies. A Japanese scientist has translated the idea
into reality. Susumu Tachi, a professor of computer science and
physics at the University of Tokyo, has invented an invisibility
cloak – a shiny overall. His feat has been acknowledged by The Time
magazine, which has chosen “Invisible Technology” using
Retro-reflective Projection Technology (RPT) as one of the coolest
inventions made in the year 2003.
The coat is made up of
retro-reflective material coated by tiny light-reflective beads
covering its entire length. The beads reflect the light back towards
the same direction as it came from. It is also fitted with cameras
that project the background of the wearer on to the front, and vice
versa. In reality, the coat doesn’t do anything except producing an
optical camouflage by blending the body of the wearer with its
background, just the same way as Nature protects some animals from
those who hunt them. These often have coloured or patterned skins
that blend with the background. A chameleon, for instance, can
change its colour to blend in with its environment. A white polar
bear is hard to spot in the snow. A striped zebra in a herd is
difficult to single out, because its outline gets lost in a
continuous spectrum of stripes.
Perfect blend
Tachi’s
cloak is not perfect; the outline of the subject is still quite
prominent. Besides, it doesn’t project a separate image of its
surroundings from all perspectives. As a result, to observe the
effect of invisibility, one has to view it from a particular point.
One may be able to see the wearer of the cloak from a distance of a
few meters, when viewed from the side.
Is it possible to develop
a real invisibility cloak? Scientists feel it is. To capture
separate images of the background from all angles simultaneously, at
least six cameras arranged in stereoscopic pairs — facing forward
and backward, up and down, and right and left — are required.
The camera needs to project the captured images on a dense array
of display elements. To be invisible at a distance of about 2
metres, the resolution should match the granularity of human vision
at that distance. It amounts to about 289 pixels per square
centimetre.
It is easy to fit 289 display elements in one square
centimetre area. Creating life-like colours is also not a problem.
Commonly used 16-bit display is sufficient to reproduce all
combinations of colours present even in a complex background.
But producing images of the background that stand out in
daylight, for instance, is surely going to put severe demands on
display technology. The display element must be able to reproduce
anything from the faintest perceptible flicker to intense sunlight
reflected from high-rise glass buildings. Billboards at Times
Square, which look magnificent in the night, become almost blank in
full daylight. Obviously, we’ll need many times more powerful
display elements than those used in billboards.
The second
challenging area is response time. Like a movie screen, the cloak’s
display must be able to beat the eye’s ability to perceive the
flickering. Moreover, it needs to register motion in real-time
without the blurring, fringing and ghosting. A laptop Liquid Crystal
Display (LCD) screen isn’t going to help it. A lattice of
super-bright Light Emitted Diode (LED) microarrays probably will be
handy.
The third, and perhaps the most complex, challenge is to
use video images from different cameras to produce a realistic
picture. What makes it more problematic is that the coat is not as
flat and smooth as a TV screen.
Some critics suggest that
Tachi’s invention is nothing but a hoax. True, in its present form,
the cloak is not that impressive. But there is noticeable
improvement in the cloak demonstrated at the Nextfest, an exhibition
of engineering technology held in May 2004, in San Francisco, over
the ones used in previous demonstrations.
When TV was
demonstrated for the first time, the transmitted picture was nothing
more than a vague collection of flickering dots on a screen. Today
the quality of the picture is unprecedented. It seems reasonable to
predict that in the next decade scientists would be able to make
humans invisible in a convincing way.
Invisibility at
work
Tachi’s cloak is getting attention from military experts who
could exploit the technology to make their troops sneak into the
enemy area without being spotted, just like Harry Potter. In Harry
Potter and the Prisoner of Azkaban, Harry used the invisibility
cloak to move around the wizard village of Hogsmeade unnoticed.
It’s hoped that the technology will be useful for surgeons
frustrated with their own hands and surgical tools, when they block
their view of operations. Pilots would also be able to see through
the cockpit floor during landings.
However, questions of
potential misuse could not be ignored, given that the mechanism
could aid and abet crime and terror. Criminals will conveniently
wait for their prey near bank ATMs, in parks and narrow lanes.
Imagine the damage terrorists can inflict if they are able to sneak
into a high-security area inside the airport or nuclear
installations.
Like the ring in The Lord of the Rings, the
invisibility cloak may have an evil influence on the wearer’s
mind.
(A former project coordinator with the National Council
of Science Museums, India, and exhibits manager at the Discovery
Centre, Halifax, the author now works as a senior server developer
in Toronto.)
Invisible underwater creatures
THE
oceans are home to some of the most amazing creatures on our planet.
Whales, sharks, manatees, seals, and sea turtles fascinate us
because we see them doing acrobatics. Scientists are now tracking
down other mystic creatures, too.
Fan-fin anglerfish, sea
cucumber, fangtooth fish, amphipod and medusa are some of the mystic
creatures because they are transparent. The sea cucumber can grow up
to a foot in length; it feeds on the ocean bottom and then swims
slyly up into the water.
The Irukandji is an invisible, deadly
jellyfish. With a bell and tentacles just 2.5 centimetres across, it
is almost impossible to detect. Its sting is often felt as nothing
more than a painful irritation due to a minor rash. By the time more
serious symptoms appear, it may be too late to save a life. The
mysterious “Irukandji Syndrome” was discovered in 1966 and may have
caused hundreds of deaths.
The clue to invisibility among sea
creatures lies in the structure of the proteins, making up the skin
and tissues. A jellyfish is an invertebrate, made up mostly of
water; it has no heart, brain or bones. It is made up of 95-97 per
cent water, 3 per cent protein and 1 per cent minerals.
The lens
inside the human eye is transparent. About 35 per cent of the lens
is made up of proteins and the remaining 65 per cent is water. The
protein is arranged in a way that keeps the lens clean and at the
same time allows the light to pass through it.
With some serious
genetic manipulation, it is possible to develop earth-bound
invisible creatures, on the lines of transparent sea
animals.
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