The author's work over the past years has indicated that the photon has a small mass ∼10−33eV. Recent observations from three different viewpoints -- the time lag in cosmic gamma rays with different frequencies, the observation of the spectra of blazars and an analysis of the CMB power supression from the WMAP data -- all vindicate this conclusion and remarkably, the same value.
Cite
@article{arxiv.0908.2170,
title = {Evidence for a photon mass},
author = {Burra G. Sidharth},
journal= {arXiv preprint arXiv:0908.2170},
year = {2014}
}