A discussion of the Einstein general theory of relativity as the most widely accepted theory for describing gravitational phenomena. However, this theory is not as simple as might be desired, and a full understanding of its implications is not easily acquired. This memorandum gives those intuitively elusive objects, "null geodesics," a mechanical interpretation which may help to explain them in terms of more concrete quantities. The study shows that the normal trajectories to any moving, two-dimensional surface which carries a mechanical disturbance through a material body are the projections into that body of light rays in an Einstein-Riemann space whose local velocity of light is equal to the normal velocity of the surface through the material body at corresponding points.
This report is part of the RAND Corporation Research memorandum series. The Research Memorandum was a product of the RAND Corporation from 1948 to 1973 that represented working papers meant to report current results of RAND research to appropriate audiences.
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