[IP] more on The Economist: How to weave a cloak that makes you invisible
Begin forwarded message:
From: Valdis.Kletnieks@xxxxxx
Date: May 26, 2006 4:08:36 PM EDT
To: dave@xxxxxxxxxx
Cc: ip@xxxxxxxxxxxxxx
Subject: Re: [IP] more on The Economist: How to weave a cloak that
makes you invisible
On Fri, 26 May 2006 15:47:33 EDT, David Farber said:
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
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.
Only if you have a baseline to calibrate the interferometer against.
Yes,
the object can be detected by an interferometer *if* it's standing in
front
of a nicely calibrated wall where you *know* what the values should be:
http://www.digitalblasphemy.com/dbgallery/2/chamelea.shtml
However, if the object is in front of a bush or a field of grass or
similar, it becomes a *lot* harder to do the interferometry trick:
http://www.michaelbach.de/ot/cog_dalmatian/index.html
(The page isn't about this, specifically - but does demonstrate the
difficulty of dealing with a "noisy" background....)
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