Re: Mirror reflections

This is really a matter of definition of axes.  What we call Left and Right
are centered on ourselves. Up and Down are defined with respect to the 
local direction of gravity.  Now, do this:  Look in the mirror from the 
side, so that one of your eyes appears above (in the gravity sense) the 
other. You will have "left and right" reversed, but "up and down" will 
still seem to be the same, yet now both are on exactly the same axis!

The mirror can not know how we define our axes; it just reverses 
(essentially) the direction of the light going into it. It is this reversal
that is at the heart of the matter. Now, do this: look at your hands, with
the thumbs pointing at your eyes and the fingers curled. There is a 
reversal here of the direction of curvature of the fingers around the thumb 
(the fingers of your left hand curl clockwise around your thumb, those of 
your right hand curl counterclockwise around your thumb). It turns out that
this reversal is the same as a mirror makes (look in the mirror at your
hands), although no mirror was involved here.

Hope this helps. Reflections and axes of symmetry can be mind-bending 
sometimes. I always had trouble with this in organic chemistry, where
some molecules twist one way and the "same" molecule could also be 
constructed except that it twisted the other way...and twisted my brain
along with it.