Also just FYI, concave mirrors can reverse up/down. i.e. spoon
"Eliezer S. Yudkowsky" wrote:
>
> Spike Jones wrote:
> >
> > Emlyn wrote:
> >
> > > My daughter (5 yo) just asked me a question which I can't answer...
> >
> > Emlyn, Ive also been stumped by a 5 year old girl, altho I suspect
> > her father mighta put her up to asking this one.
> >
> > She said: if things in a mirror appear reversed, why dont they
> > also appear upside down?
>
> Mirrors do not reverse right and left. They reverse front and back. When
> you raise your right hand, the image in the mirror does not raise a "left"
> hand; it raises a right hand with front and back reversed, so that you see
> the front of the hand instead of the back.
>
> It so happens that, because humans are roughly symmetrical in the
> right/left plane, it is possible to take an image that with front and back
> reversed and mentally imagine that it is actually a nonreversed human who
> has been rotated 180 degrees around a vertical axis. If humans had two
> arms on the right and one arm on the left, but two heads, we would
> mentally visualize ourselves as rotating around a horizontal axis and we
> would say that a mirror reverses up and down.
>
> -- -- -- -- --
> Eliezer S. Yudkowsky http://singinst.org/
> Research Fellow, Singularity Institute for Artificial Intelligence
-- Brian Atkins Director, Singularity Institute for Artificial Intelligence http://www.singinst.org/
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