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From: billp@azure.UUCP (Bill Pfeifer)
Newsgroups: net.philosophy
Subject: Re: Why do mirrors reverse left & right, not up & down?
Message-ID: <2522@azure.UUCP>
Date: Fri, 3-Feb-84 13:10:16 EST
Article-I.D.: azure.2522
Posted: Fri Feb  3 13:10:16 1984
Date-Received: Wed, 8-Feb-84 07:45:26 EST
Organization: Tektronix, Beaverton OR
Lines: 23

*
>> How about "doing" some philosophy on the net?  Can anyone provide
>> a convincing account of why mirrors perversely do such things?

Mirrors aren't perverse, and they do no such thing.  They simply reflect
light back the same way they receive it.  Think of the image in the mirror
as that on a photographic slide.  Orient the slide such that if you look
through it, it matches the original scene.  This corresponds to you standing
behind the mirror.  In order to see the mirror's reflected image, however,
you must move to the other side of the mirror and rotate your body 180 degrees.
This corresponds to flipping the slide over.  The way you rotate you body
or flip the slide, determines whether you, not the mirror, exchange
left & right or up & down.

If you simply turn around, this corresponds to rotating the slide about
its vertical axis.  You have now exchanged left & right, but not up & down.

If you were to stand on your head and look at the image in the mirror,
this would correspond to rotating the slide about its horizontal axis.  You
have now exchanged up & down, but NOT left & right.

	Bill Pfeifer
{cbosg,decvax,harpo,ihnss,ogcvax,pur-ee,ucbvax,zehntel} !tektronix!tekmdp!billp