[IP] more on The Economist: How to weave a cloak that makes you invisible
Begin forwarded message:
From: Denis Russell <D.Russell@xxxxxxxxxxxx>
Date: May 26, 2006 4:07:53 PM EDT
To: dave@xxxxxxxxxx, Ed Gerck <egerck@xxxxxxx>
Subject: Re: [IP] more on The Economist: How to weave a cloak that
makes you invisible
At 15:47 -0400 26/5/06, David Farber wrote:
Begin forwarded message:
From: Ed Gerck <egerck@xxxxxxx>
Date: May 26, 2006 2:10:32 PM EDT
To: dave@xxxxxxxxxx
Cc: ip@xxxxxxxxxxxxxx
Subject: Re: [IP] The Economist: How to weave a cloak that makes
you invisible
From The Economist print edition
http://www.economist.com/science/displaystory.cfm?story_id=6971134
How to weave a cloak that makes you invisible
The invisibility claim does not follow from the theory. The
electromagnetic,
waves, even if they maintain the exact same path and polarization
after the
object, will be delayed by "going around". Since the speed of light
cannot
increase beyond c, there is no way to make up for the delay. The
object can
be seen by a simple interferometer arrangement.
...
Well the body would act much like a lens, with the thicker bits
delaying the light more, but the delay would depend not just on the
thickness (and refractive index), but on the extra delay running
round the object. In the "perfect" case, the interferometer effect
would act at the emitting surface, with the slightly phase shifted
adjacent emitting points interfering with each other and sending the
light off at an angle rather than straight out. (Think of all those
elementary illustrations of how the wave theory of light predicts
refraction at the interface between two materials of different
refractive indices, and remember that refractive index=>speed in the
material => delay on the optical path). The effect would be visible
to the naked eye as a distortion of the image of the stuff behind the
invisible body - like looking through a polythene bag of water with a
funny (and high) refractive index.
Denis
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