Stellar Aberration and the Determination of the Velocity Ratio - A Common Root in L-ARF

Abstract

Stellar aberration, discovered by James Bradley in 1727, and the determination of absolute velocity from forward and return light times in L-ARF (Light - Absolute Reference Framework, Sec. 2.1 and Ch. 7.5) share a common physical root. Both methods determine the dimensionless ratio v/c: - Bradley aberration: tan(alpha) = v_perp / c ≈ 20.5" for Earth's orbital velocity (relative velocity with respect to the Sun, ~29.8 km/s), measured as angular shift.- L-ARF forward-return method: v_parallel / c = Delta t / Sigma t, where t+ = L/(c-v), t- = L/(c+v), Sigma t = t+ + t-, Delta t = t+ - t-, measured as time difference. This gives absolute velocity with respect to vacuum's IRF (space itself). Common postulate (L-ARF Sec. 2.1): The velocity vector of light in vacuum is independent of the motion of source and observer. Light does not follow the observer. Therefore both rely on the same postulate that light does not follow the observer; if it did, neither tilt alpha nor Delta t would occur. They are complementary first-order measurements for orthogonal components: v_perp from angular shift and v_parallel from time difference. The paper also discusses the connection to Michelson-Morley 1887: Bradley used an open-tube instrument (v/c visible as angle), Michelson-Morley used a closed interferometer. In L-ARF, light does not follow the mirrors in vacuum's IRF. Bradley's open one-way path makes v_perp/c visible as angular shift, while MME's closed two-way path makes v_parallel/c visible as time difference Delta t. The classical interpretation searched for a second-order fringe shift proportional to v^2/c^2 and reported a null result for Delta t. This point was considered earlier by the author in connection with MME in Special Relativity is Nonsense (2020) and Light - The Absolute Reference in the Universe (2021), but not as a separate article. The present comparison makes the connection explicit.