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According to the general theory of relativity, the geometrical

properties of space are not independent, but they are determined

by matter. Thus we can draw conclusions about the geometrical

structure of the universe only if we base our considerations on

the state of the matter as being something that is known. We know

from experience that, for a suitably chosen co-ordinate system,

the velocities of the stars are small as compared with the

velocity of transmission of light. We can thus as a rough

approximation arrive at a conclusion as to the nature of the

universe as a whole, if we treat the matter as being at rest.