From jcowan@reutershealth.com Thu May 16 10:36:32 2002
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In-Reply-To: <20020516131322.S44426-100000@granite.thestonecutters.net> from "Invent Yourself" at May 16, 2002 01:20:45 PM
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From: John Cowan <jcowan@reutershealth.com>
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Invent Yourself scripsit:

> x1 is the parallax of x2 as seen by x3 who moves to x4 from x5

I don't understand what x3 has to do with it, frankly. I can talk about
the parallax of an object on the opposite wall from one side of a room
vs. the other side, without postulating an observer who actually moves
across the room.

Furthermore, an important case of parallax is the parallax between a single
observer's left and right eyes, which is the basis of depth perception,
and obviously does not involve any sort of motion.

So I propose: x1 is the parallax of x2 at observation point x3 relative to
observation point x4.

-- 
John Cowan <jcowan@reutershealth.com> http://www.reutershealth.com
I amar prestar aen, han mathon ne nen, http://www.ccil.org/~cowan
han mathon ne chae, a han noston ne 'wilith. --Galadriel, _LOTR:FOTR_

