Chapter IV
Frame of Reference

Such things do not exist and cannot exist and never have existed ...  Yet when people see these frauds, they find no fault with them but on the contrary are delighted, and do not care whether any of them can exist or not.

- Vitruvius

I am not in favor of compact designs which give an impression of solidity and recall heavy earthly buildings.  Other laws prevail in space and there is no reason why the old architectural rules should be followed.

- Hermann Oberth

Artificial gravity is often presented as a panacea for all of the ills associated with prolonged weightlessness.  While extensive study has been devoted to the design of the artifact (structure, stability, propulsion, and so on), relatively little has been written about the design of the environment, from the point of view of an inhabitant living and moving within it.  It has often been implied, and sometimes stated outright, that artificial gravity should permit the adoption of essentially terrestrial designs; the artificiality of the gravity has been downplayed.  But saccharin is not sucrose, and centripetal acceleration is not gravity as we know it.

Human tolerance and adaptation to artificial gravity have been studied in centrifuges and slow rotation rooms.  Boundary values for radius, angular velocity, and acceleration have been presented in various hard-edged comfort charts that characterize a set of values as being either in or out of a hypothetical "comfort zone".  The tendency has been to reject any design that falls outside the zone, but to accept as "essentially terrestrial" any design within.  Yet there are significant discrepancies between the comfort boundaries proposed by various authors, and all of them include conditions that hardly qualify as "Earth-normal".  This suggests that the comfort boundaries are fuzzier than the individual charts imply, and that comfort may be influenced by task requirements and environmental design considerations beyond the basic rotational parameters.

This chapter examines the relationship between the physics of rotation and the perception of comfort.  Using mathematical derivations and computer simulations, it analyzes the abnormalities inherent in relative motion through artificial gravity, from the point of view of a person living and moving within a rotating environment.