mind & mirrors (puzzle)

Here's a little puzzle I stumbled across that I thought appropriate for this forum:

"Why does a mirror reverse left and right, but not up and down?"

Now, before dismissing it, think about it some more. Why does the mirror flip the scene along one axis but not the other? Does the mirror somehow know what is up and down...? :devil:

Because it doesn't? It's your perception that's flipped..

As ACMarina stated, it doesn't flip left and right.
From here http://answers.google.com/answers/threadview?id=226025
"Why does a mirror reverse left and right, but not top and bottom?"

It doesn't.

The mirror reverses front and back, not left and right (nor top and
bottom).

We are accustomed to having someone or something which is facing away
from us "turn around" to see the front (instead of the back). It is
actually the act of turning around which reverses left and right. The
mirror faithfully puts the left on the left and the right on the
right, which has come to seem "backwards" to us; we "expect" the left
to be on the right and conversely.

Perhaps if we customarily flipped upside down to face one another
(instead of turning around), our perception of the mirror image might
be that it "reverses up and down".

regards, mathtalk-ga

Oh, well - google spoiled this one. You are correct of course. I really thought a long time about this puzzle - I guess that says more about me than the puzzle