Empirical evidences in favor of a varying-speed-of-light

TL;DR

This paper presents empirical evidence supporting the hypothesis that the speed of light decreases over time, explaining phenomena like the Pioneer anomaly and cosmic acceleration, while discussing constraints from fundamental constants.

Contribution

It provides observational support for a varying speed of light and discusses implications for fundamental physical constants and cosmological phenomena.

Findings

Lunar laser ranging data is consistent with a decreasing speed of light.

A varying speed of light explains the Pioneer anomaly and cosmic acceleration.

Constancy of physical constants implies multiple constants must vary if light speed changes.

Abstract

The empirical evidences in favor of the hypothesis that the speed of light decreases by a few centimeters per second each year are examined. Lunar laser ranging data are found to be consistent with this hypothesis, which also provides a straightforward explanation for the so-called Pioneer anomaly, that is, a time-dependent blue-shift observed when analyzing radio tracking data from distant spacecrafts, as well as an alternative explanation for both the apparent time-dilation of remote events and the apparent acceleration of the Universe. The main argument against this hypothesis, namely, the constancy of fine-structure and Rydberg constants, is discussed. Both of them being combinations of several physical constants, their constancy imply that, if the speed of light is indeed time-dependent, then at least two other "fundamental constants" have to vary as well. This defines strong constraints which will have to be fulfilled by future varying-speed-of-light theories.