Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site rabbit.UUCP Path: utzoo!watmath!clyde!burl!ulysses!harpo!eagle!allegra!alice!rabbit!ark From: ark@rabbit.UUCP (Andrew Koenig) Newsgroups: net.philosophy Subject: Re: Why do mirrors reverse left & right, not up & down? Message-ID: <2471@rabbit.UUCP> Date: Thu, 2-Feb-84 22:13:51 EST Article-I.D.: rabbit.2471 Posted: Thu Feb 2 22:13:51 1984 Date-Received: Wed, 8-Feb-84 01:50:55 EST References: <537@bbncca.ARPA> Organization: AT&T Bell Laboratories, Murray Hill Lines: 26 This is a trick question. Defining terms carefully makes the problem go away. Imagine yourself standing in front of a full-length mirror. The reflection of your right hand is nearest the right edge of the mirror, and the reflection of your left hand is nearest the left edge. The reflection of your head is nearest the top edge, and the reflection of your feet is nearest the bottom. In what way, then, can a mirror be said to reverse left and right, any more than it reverses top and bottom? Well, now, you may say, suppose there's a person standing behind you. Her right hand is also nearest the right edge of the mirror and her left hand is nearest the left edge. If you turn around to look at her, though, her right hand will be on your left and her left hand will be on your right. In that sense, what you see when you look directly at her is reversed left for right compared to what you see in the mirror. However, that has nothing to do with the mirror. Rather, it has to do with what you did when you turned around to look directly at her. You turned around a vertical axis. If instead you had turned around a horizontal axis (by standing on your head), her left hand would still be nearest to your left hand and her right hand would still be nearest your right hand. Her head, though, would now be near your feet and her feet near your head.