ABSTRACT
You are standing before a full-length mirror; why is it that while your left and right sides are reversed, flipped, this is not true of your top and bottom, your head and feet? This question has exercised some very acute minds for hundreds of years, and there is room still for more debate. I won’t answer it here, except to comment that the top-bottom axis or coordinate is determined by external, physical constraints, including gravity, while left-right is more a matter of human convention. A related issue is the question as to why, if you hold your knickers or underpants at the sides as if about to step into them, and without letting go, flip them inside out, left and right don’t change, but the front now becomes the back. And if you turn a left-hand latex glove inside out, it becomes a perfectly serviceable right-hand glove. Next, and for obvious reasons this demonstration may be more readily performed on the male torso, get someone to stand, topless, with eyes closed, and trace, with a blunt stylus (a ‘dead’ ballpoint will do just fine), on his chest a cursive lower-case letter p or q, or b or d, which are left-right ambiguous, and ask him which letter it felt like. Do this several times, noting his answers, and repeat this time on his back. If you can, persuade someone else also to contribute, this time start on the back and then ‘do’ the chest. Even better, maybe, randomly alternate front and back and p, q, b, d. Then do the same but now on the hand – palm and back of hand when hand is held up, as if in salutation, with either palm or back facing forward. Maybe do all of this, as a party game if you like (kids and even adults will be intrigued), under three conditions: when the hand is in a plane further forward than the rest of the body, when it is further behind the plane of the body, and when it is in exactly the same plane as the upright body. Have fun at your local night club, and I won’t spoil it by boring explanations!
