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If an entity is to be considered as a scientific entity we must be able to say what would enable us to detect it. This is the basis of Einstein's objection to Newton's . There are no physical operations, according to Einstein, which enable us to distinguish absolute space. As regards absolute time, Newton himself confessed that there may be no natural processes which enable us to measure it. We can never, in the nature of things, say whether we are dealing with absolute time or not. Both these entities, therefore, are described by Einstein as metaphysical, with no real place in science.
— J. W. N. SULLIVAN