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| Heavy optics |
How can cats see in the dark? Ancient authors had some very amusing explanations. The physician Alexander of Tralles, writing about the year 600, stated that cats and bats and other night creatures had a brighter “optical spirit” within their eyes, allowing them to see at night.
Humans and other day creatures, on the other hand, had a heavy optical spirit, which allowed them to see by day but not at night.
