Physicists have long assumed detection of absolute velocity to be impossible, even that “absolute velocity” is without meaning. The firmness of this belief is associated with the peculiar success of Einstein's special relativity theory. Special relativity theory (1905)[1] asserts that, when a certain definition of “simultaneous events” is employed, observations will fail to detect motion relative to the absolute reference frame, a.k.a. the luminiferous ether, and that the failure is inconsequential inasmuch as the laws of mechanics and electrodynamics will hold in any inertial frame of reference. The definition of "simultaneous events" employed in relativity theory was simply the formalization of the best available practice for clock synchronization in that era.

… we establish by definition that the “time” required by light to travel from A to B equals the “time” it requires to travel from B to A. (Einstein, 1905)
It has two disadvantages, (1) it abandons the intuitive notion that simultaneity is an equivalence relationship for time regardless of motion, and (2) rather than being a proper definition, it is an unjustified assertion, inconsistent with the current SI atomic standard of time; back in 1905, time was defined astronomically by Earth's motion.

Concerning the second disadvantage, one ought not assign by definition a value that is essentially an empirical quantity. With the atomic clock standard for time, one way time of light communication is now an empirical quantity. Two ideal clocks, which keep accurate time even if moved, can be used to measure one way speed of light each way between them after first being synchronized while together before being moved some distance apart. The definition of simultaneity cannot be independent of the definition of time itself. That relativity theory defines simultaneity in a way that precludes universal agreement on the measure of time is well known; time is not well-defined in special relativity theory.

In this appendix simultaneity is defined as an equivalence of time consistent with our intuition and the SI definition of time. Because it is different from the relativistic definition, statements made based on this definition may appear false if one attempts to understand them in relativistic terms. With this definition, relying on highly accurate clocks such as exist today, our assertions relate more readily to classical physics than to relativistic physics. A logical consequence of this new definition, considered together with empirical evidence, is the possibility of detecting and measuring velocity relative to an absolute frame of reference.

To establish the meaning of absolute velocity, I begin by extending the conclusion from de Sitter's (1913)[2] astronomical proof of the constancy of light speed. To create consistency with a set of transformations that does not include time dilation, I present a reasonable re-interpretation of the Michelson-Morley experiment (1887)[3]. The empirical foundation laid by de Sitter and Michelson-Morley, with the equivalence property of synchronization, gives rise to a set of transformations different from the Lorentz transformations (1895)[4] used in relativity theory, from the Voigt transformations (1887), and from Ivanov's transformations (1981) which differ in the time element only but which are the same that Einstein derived up to "Substituting for x' its value ...". Relative time is replaced by universal time, and all influences that tend to disturb clock rate will be will be compensated for. The proposed method to determine absolute velocity, unlike the Michelson-Morley experiment, uses clocks to time one-way light propagation.

[1] Einstein, Albert, “Zur Elektrodynamik bewegter Körper,” Annalen der Physik 17:891, 1905, “On the Electrodynamics of Moving Bodies,” online in English

[2] de Sitter, Willem, “Ein astronomischer Beweis für die Konstanz der Lichgeshwindigkeit," Physik. Zeitschr, 14, 429 (1913). “A proof of the constancy of the velocity of light,” Proceedings of the Royal Netherlands Academy of Arts and Sciences 15 (2): 1297-1298, online in English

[3] Michelson, Albert Abraham & Morley, Edward Williams (1887). “On the Relative Motion of the Earth and the Luminiferous Ether.” American Journal of Science 34: 333-345. online

[4] Lorentz, Hendrik Antoon, “De relatieve beweging van de aarde en den aether,” Zittingsverlag Akad. V. Wet. 1: 74-79, (1892), online in English

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