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Two points here. One about communication with an "intelligent being," andcarbon,
the other about whether there are more "opposites."
(1) Rather than discuss the rotations and reflections as John Denker did,
another way to approach this is from the stereochemistry of molecules. If
we assume the "intelligent being" has never seen a mirror, but knows some
chemistry, and knows some astronomy, we can define mirror images and right
and left handedness by chemistry and astronomy. I will assume we have had
sufficient dialogue with this "intelligent being" that we can discuss
chemicals... that is, the being understands what we mean when we say
hydrogen, chemical bond, etc. If not, you'll have to reach that levelfour
first.
Take a carbon-containing molecule in which at least one carbon atom has
other atoms bonded to it, and one (and only one) of the carbon atoms has"mirror
four "different" atoms attached. A simple example would be CHClFBr
(flourochlorobromomethane).
The geometry around this carbon is tetrahedral. This molecule is also
chiral (handed). Construct two model molecules with balls and sticks, or
whatever. Depending upon how you assembled the two models, they might be
identical (can be stacked so they are superimposed on each other)...
otherwise they will be "mirror images" of each other. Whichever they are
(identical or mirrors) one molecule can be converted to the other form by
switching the positions of any two attachments. Assemble them so they are
not superimposable on each other. We now have two objects that are
images" of each other. This could serve as one type of definition ofThis is where I object. Why do you say that the alien must only get two
"mirror image."
I believe the reduction of other objects into "chiralCrucially - how?
centers" is also possible and would follow the same logic.
Apologies to those of you who have not taken an organic chemistry courseand
do not have experience with the fascinating subject of stereochemistry.Fortunately, I know enough at least to follow your argument. But (as a