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- Robert W. Latzer (1972). Nondirected Light Signals and the Structure of Time. Synthese 24 (1-2):236 - 280.Temporal betweenness in space-time is defined solely in terms of light signals, using a signalling relation that does not distinguish between the sender and the receiver of a light signal. Special relativity and general relativity are considered separately, because the latter can be treated only locally. We conclude that the (local) coherence of time can be described if we know only which pairs of space-time points are light-connected. Other consequences in the case of special relativity: (1) a categorical axiom system exists in terms of nondirected light connection alone, with neither particle nor time order as a primitive concept, though we do not actually present the axioms; (2) any concept definable by coordinates is also definable in terms of nondirected light signals if and only if it is invariant under Lorentz transformations, translations, dilations, space reflections, and time reflections; and (3) any transformation of space-time (not necessarily continuous) which preserves nondirected light connection is a product of transformations just listed above. The bulk of the paper is devoted to proving that the definitions we give correspond to their intended interpretations in the usual space-time continua.
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Touch and sight : the earth and the heavens -- What happens and what is observed -- The velocity of light -- Clocks and foot-rules -- Space-time -- The special theory of relativity -- Intervals in space-time -- Einstein's law of gravitation -- Proofs of Einstein's law of gravitation -- Mass, momentum, energy, and action -- The expanding universe -- Conventions and natural laws -- The abolition of "force" -- What is matter? -- Philosophical consequences.
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In this paper, I start with the opposition between the Husserlian project of a phenomenology of the experience of time, started in 1905, and the mathematical and physical theory of time as it comes out of Einstein’s special theory of relativity in the same year. Although the contrast between the two approaches is apparent, my aim is to show that the original program of Husserl’s time theory is the constitution of an objective time and a time of the world, starting from the intuitive giveness of time, i.e., from time as it appears. To show this, I stress the structural similarity between Husserl’s original question of time and the problem of a phenomenology of space constitution as it was first developed in the his manuscripts from the nineteenth century, in which we find the threefold question of the origin of our representation of space, of the geometrization of intuitive space, and of the constitution of transcendent world space. Finally, I reconsider some of Husserl’s main theses about the phenomenological constitution of objective time in light of the main results of special relativity time-theory, introducing several corrections to central assumptions that underlie Husserl’s theory of time.
Special relativity was based on the theorem that time is affected by motion. Einstein's proof of this was an imaginary experiment with clocks, using light as a synchronizing signal. He has said that the kind of signal was immaterial. Subsequent interpreters have stated that sound signals could just as well have been used. Today any airplane passenger's watch denies Einstein's mathematics, had he used sound. The Lorentz-Einstein transformation equations in which the speed of sound is substituted for the speed of light are unthinkable. But if they do not hold with sound as the signal, no more do they with light, for the process is identical. The transformation equations for space are based on the variability of time, and are therefore likewise denied.
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