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Living under conditions of zero gravity may be taken in stride by denizens of the future, but it is hard to comprehend by those of us with a strictly earthbound upbringing. Yet such conditions of living are on the planning board. Of particular interest to ophthalmologists is the recently issued booklet entitled "Visual Problems of Space Travel" (National Academy of Sciences-National Research Council). In this we read: "orientation in a spacecraft will depend primarily on visual cues in the absence of reliable vestibular... tactual, and kinesthetic cues which are dependent on a gravitational field."
The proverbial fancy of not knowing which way is up is a real problem for the astronaut. His labyrinthine mechanisms which were designed for tree-to-tree hopping under conditions of G one will give him entirely erroneous information in a spacecraft under conditions of G zero. We are told that movement of a person's head when he