Re: Fabulous Adventures In Coding (Eric Lippert)

From: Al Dunbar [MS-MVP] (alan-no-drub-spam_at_hotmail.com)
Date: 02/13/04 

Date: Thu, 12 Feb 2004 23:50:56 -0700

"Richard Cornford" <Richard@litotes.demon.co.uk> wrote in message
news:c0haec$pd1$1$8302bc10@news.demon.co.uk...
> "Al Dunbar [MS-MVP]" <alan-no-drub-spam@hotmail.com> wrote in message
> news:eQOj9sS8DHA.1040@TK2MSFTNGP10.phx.gbl...
> <snip>
> >But seriously, now, can Eric tell us why things seen in a
> >mirror are reversed side-to-side but not top-to-bottom?
>
> Objects observed in mirrors are not reversed side to side they are
> reversed front to back. That is, assuming a vertical mirror with its
> plane running east to west, the most northerly part of a reflected
> object becomes the apparently most southerly part of the reflection of
> the object. No other transformations take place.

Nice responses all, and thanks.

Here is one I got from a colleague the last time I sprung this little
nugget. He said that things are reversed side to side because our visual
perception is based on our two eyes being side by side, not over/under, if
you will.

Seemed reasonable until I considered the case of the one-eyed man. Applying
the side-by-side eye theory carefully, one would have to conclude that a
one-eyed person would see his reflection reversing alternately top to bottom
and left to right. If fast enough, this could have the effect of causing it
to appear to be spinning around. Perhaps that is why the uni-ocular among us
have so much trouble getting driver's licenses.

Anyway, here are the marks I have assigned - if you don't like them turn
them upside down, reverse them side to side, or discount them altogether,
whichever gives you the best score:

1. Richard. the front-to-back reversal concept comes the closest to helping
me get to sleep after thinking about this too much. In fact, it basically
shoots to heck all of the counter arguments I have come up with regarding
any of the other submissions, either in this thread or elsewhere.

2. Han. I'm still "thinking about stamp"; unfortunately, this makes me even
dizzier than before, so there must be something to your logic.

3. tie: Dave and Jeff. Both said in humour, however, Jeff seems to be in
denial, while Dave is deflecting attention away from his lack of answer by
asking a question (not a bad tactic, by the way).

4. Evertjan. I would have rated you higher, as you seem to have the same
skeptical and questioning attitude that I have. But, like me, you find it
easier to diss the logic of others than to answer the question. While I like
the attitude, there is only room for one of us :-) Oh, OK, I give in, as
your comment about the "would-be" programmers is right on the money.

5. Mark - response 1. Completely faulty physics, but scores well for casting
a favourable light on an oft-forgotten group of disabled people - lefthanded
golfers. And extra for making a reference to a deceased person who could
probably have given a correct answer. As a make-up exam, please consider
explaining the phenomenon of the left-handed pianist, deceased or otherwise.

6. Mark - response 2. giving a perfectly good answer for a question not
asked.

What, did nobody point out that this defect all mirrors have can be easily
fixed? All you have to do is turn out the light, and the mirror will no
longer reverse things any which way.

/Al

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