Page 152 - The Cambrian Evidence that Darwin Failed to Comprehend

The Cambrian Evidence That Darwin Failed to Comprehend

transparent, allowing light to pass through. Each calcite lens in the
trilobite eye is biconvex in shape, that is, convex on both sides.
At the bottom of the lenses, Levi-Setti and Clarkson encoun-
tered an extraordinary state of affairs. Every lens actually consisted
of two units. The upper lens unit was made of calcite, and the bot-
tom was chitin-based. Descartes and Huygens’ mathematical de-
signs and the actual intermediate surface where the two units came
together in the trilobite eye lens were in remarkable accord with one
another. Magnesium atoms were arranged along the length of this
surface in the lens, in sufficient quantities to overcome the spherical
aberration. Thanks to these atoms, every light beam curved to the
left was balanced by one to the right, thus enabling light rays initial-
ly refracted at different angles to focus on the same spot. (See dia-
gram opposite.)
Levi-Setti expressed his amazement at the situation:
In fact, this optical doublet is a device so typically associated with hu-
man invention that its discovery in trilobites comes as something of a
shock. The realization that trilobites developed and used such devices
half a billion years ago makes the shock even greater. And a final dis-
covery—that the refracting interface between the two lens elements in
a trilobite’s eye was designed in accordance with optical constructions
worked out by Descartes and Huygens in the mid-seventeenth centu-
ry—borders on sheer science fiction. 115

Extraordinary Sensitivity

The creation in the trilobite lens reveals an extraordinary sensi-
tivity in terms of the calcite and chitin refractive indexes. (Refractive
index is a measure for how much the speed of light is reduced when
passing from one medium into another. For instance, the refractive
index of air is 1, of glass 1.5, of water 1.33, and of diamond 2.42.) The

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