To: WSFAlist at keithlynch.net
Date: Sun, 9 Feb 2003 02:49:06 -0500
Subject: [WSFA] Re: invisibility cloak
From: ronkean at juno.com
Reply-To: WSFA members <WSFAlist at keithlynch.net>

On Sat, 08 Feb 2003 15:33:36 -0500 Sam Pierce <scpierce at alum.mit.edu>
writes:
> The news bit on TV yesterday was not impressive.  The image was much
> darker
> than the background so you saw the outline of the guy in the hat and
>
> trenchcoat quite clearly.
>

I'm not surprised that the demo was unimpressive, but not because the
displayed background image seemed too dark.  That problem alone could be
fixed by adjusting the brightness of the display, a seemingly simple fix,
in principle.  And the brightness problem may have been caused by the
unusually bright lights used in TV studios to illuminate the subjects (if
the demo was done in a studio).  The subject was presumably
well-illuminated by the studio lights, but that unusually large amount of
extra light may have 'washed out' the display to some degree.  The
display brightness might have been correctly adjusted for typical
lighting conditions.  They might have forgotten to correct for the
unusually strong studio lighting, or more likely, the display could not
be made bright enough to do so.  An ordinary TV screen is difficult to
view in typical outdoor daylight, and is nearly impossible to view when
strong sunlight happens to be shining directly on the screen.

It would be quite difficult to implement a highly effective invisibility
'cloak' using a display which is flexible and which has an ill-defined
shape, like a typical cloak or trenchcoat, even if the invisibility is
only intended to affect observers looking from a single direction.  The
logical shape for an invisibility shield which needs to work in only one
direction would be a flat panel, for a shield which is to work in all
horizontal directions, a cylinder, and for a shield which is to work when
seen from any direction in three dimensions, a sphere.

Ron Kean

.

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