The CMB Rest Frame as a Physically Motivated Interpretation of Time Dilation in Special Relativity

The twin paradox in special relativity admits multiple interpretations regarding whichreference frame determines differential aging. The standard interpretation invokes acceleration as the tiebreaker; we develop an alternative interpretive framework in whichthe reference frame defined by the isotropy of the cosmic microwave background (CMB)serves as the physically privileged frame for determining time dilation. We demonstratethat acceleration functions as a proxy for velocity history integration rather than a causalagent, using a triple-brother scenario that avoids acceleration entirely. We justify treatingthe CMB frame as approximately Minkowskian on the scales relevant to our experimental proposal. We present a decisive experimental test: comparing the fractional-periodintegrated proper times of high-precision clocks at different Earth longitudes, where thecross-term between Earth’s rotational velocity and the solar system’s CMB-frame velocityyields a longitude-dependent signal that does not vanish when clocks are compared overnon-integer multiples of the sidereal day. We provide a quantitative assessment of thedistinguishing power and honestly evaluate the conditions under which the interpretationremains empirically indistinguishable from the standard one. This work does not challengethe mathematical formalism of special relativity but clarifies its interpretive foundations.