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From: crummer@AEROSPACE.ARPA
Newsgroups: net.physics
Subject: Right for Left
Message-ID: <257@sri-arpa.ARPA>
Date: Fri, 7-Jun-85 18:43:53 EDT
Article-I.D.: sri-arpa.257
Posted: Fri Jun  7 18:43:53 1985
Date-Received: Tue, 11-Jun-85 03:19:52 EDT
Lines: 23

From:  Charlie Crummer <crummer@AEROSPACE.ARPA>

> Date:     Thu, 30 May 85 15:40:22 EDT
> From:     Doug Gwyn (VLD/VMB) <gwyn@Brl.ARPA>
> Subject:  Re:  Reversal

> Andrew Knutsen is right; a mirror does not reverse right & left
> but appears to do so only because of the way we think about
> comparing the image seen "in" the mirror against the original
> object, namely via a 180-degree rotation about a vertical axis
> combined with a translation to superimpose the two.

  A mirror reverses right and left HANDEDNESS.  It is sort of like
  turning the image inside-out.  A left glove becomes a right glove
  when it is turned inside-out.  In differential geometry the term for
  mirror reversal is screw-sense transformation; in physics it is called
  parity.  

> Could we leave the SDI discussion out of net.physics?

  It's hard when the subject is Right and Left.

  --Charlie