Righthanded Pretzel |
It is obvious that these two pretzels are not made by photo chicanery. They are not exactly the same shape and the flash went off on the lefthand photo and not on the right one. To a first approximation these two pretzels are mirror images, or in chemical terms, enantiomers. The handedness, or chirality, of the pretzel is determined by the spiral, or twist. When a pretzel is made by hand, a length of dough is held, one end in each hand as one might do with a length of rope. This arrangement is achiral (without handedness) since a vertical plane passes through the center of the length of dough and the preparer. |
Lefthanded Pretzel |
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To make the twist or spiral, the plane of symmetry must be broken. The tendency for a lefthanded person is to lead outward with the lefthand and to produce a righthanded spiral while the righthanded person tends to lead outward with the righthand to produce a lefthanded spiral. Of course, left outward is the same as right inward and visa versa. |
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When the same two pretzels are placed in
a handed environment --- namely --- the newspaper, the two
images below are no longer mirror one another. The text on
the right would have to read from right to left. Clearly,
there is no photo chicanery going on here. Although the
pretzels are mirror images, the newspapers are identical.
Therefore, the two pictures are different. If these two
pictures were chemical compounds, they would be called
diastereomers. |
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