Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ucbvax!sdcsvax!sdcc6!ir353
From: ir353@sdcc6.ucsd.EDU (Matthew Grayson)
Newsgroups: sci.misc
Subject: Re: quick question
Message-ID: <3596@sdcc6.ucsd.EDU>
Date: 25 Jan 88 00:54:58 GMT
References: <760@aucs.UUCP> <1170@petsd.UUCP> <3033@zeus.TEK.COM> <676@mit-caf.UUCP>
Reply-To: ir353@sdcc6.ucsd.edu.UUCP (Matthew Grayson)
Distribution: na
Organization: University of California, San Diego
Lines: 45

In article <676@mit-caf.UUCP> herb@mit-caf.UUCP (Herbert Neuhaus) writes:
>In article <3033@zeus.TEK.COM> rob@amadeus.UUCP (Dan Tilque) writes:
>>C. J. Henrich writes:
>>>In article <760@aucs.UUCP> 820785gm@aucs.UUCP writes:
>>>>	So just why DOES a mirror reverse left and right, but not up and down?
>>>The mirror, by itself, reverses front-to-back.  Our sense of vision,
>>>seeing the result, mentally applies a rotation to the mirror image.
>>>... close as possible to one's "body image.  ...
>>Not quite true.  Mirrors do reverse front-to-back.  But we interpret our
>>body image as if we were meeting someone else.  Thus we expect our image's
>>right hand to be on the left.  ...
>
>If our interpretation of mirror images is related to expectations of meeting
>"someone", then why do inanimate objects seem to beahve the same way in 
>mirrors as people do?
>
>I agree the trick is in our sense of vision, but reject the idea that
>its an anthropomorphic reaction.
>.....

>What do you think?
>
>Herb ( on his side in front of a mirror).

Suppose that you had a book in which the pages are printed with
random orientations, some reversed, some rotated. You open the
book at random and aim it at the mirror. You see a page in the
mirror, and you ask yourself: What does it look like on the page?
Slow Motion now.... You turn the book around!
	Any rotation in an odd dimensional space has a fixed axis.
In order to see the real page, you must choose an axis about which to
rotate. O.K., you say, I'll leave the book still and go look....
No good, you still have to turn around somehow, and that turning requires
a choice of orientation. It's impossible to see the real page without
making this choice. If you turn the book around a vertical axis, it 
appears reversed left-right. If you turn it around a horizontal axis,
it's upside-down. Axes at other angles yield different answers.
	Ahah! I'll make the book transparent and look straight through
it! Surprise! I see exactly the same image as in the mirror! This
yields a disturbing conclusion. Mirrors don't reverse images at all,
they reverse orientation (we see the back of something instead of the front).
In order to convert the mirror image to a front view, we introduce the
choice of axis which results in a reversed (or upside-down or whatever)
image.
	Matt