There are some important implications to photon rest mass. Note in the first link the statement, “it is possible to consider some far-reaching implications of a massive photon, such as variation of the speed of light, deviations in the behaviour of static electromagnetic fields, longitudinal electromagnetic radiation and even questions of gravitational deflection.” Note specifically the statement, “even questions of gravitational deflection”. That is the subject of this thread, i.e. a photon with rest mass as opposed to curved space time.
And from the second link, "A new limit on photon mass, less than 10-51 grams or 7 x 10-19 electron volts, has been established by an experiment in which light is aimed at a sensitive torsion balance; if light had mass, the rotating balance would suffer an additional tiny torque. This represents a 20-fold improvement over previous limits on photon mass. Photon mass is expected to be zero by most physicists, but this is an assumption which must be checked experimentally. A nonzero mass would make trouble for special relativity, Maxwell's equations, and for Coulomb's inverse-square law for electrical attraction."
Is anyone interested in this topic?
http://www.iop.org/EJ/abstract/0034-4885/68/1/R02/
Liang-Cheng Tu1, Jun Luo1,3 and George T Gillies2
1 Department of Physics, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China
2 School of Engineering and Applied Science, University of Virginia, Charlottesville, VA 22904, USA
3 Author to whom any correspondence should be addressed.
E-mail:
junluo@mail.hust.edu.cn and
gtg@virginia.edu
Abstract. Because classical Maxwellian electromagnetism has been one of the cornerstones of physics during the past century, experimental tests of its foundations are always of considerable interest. Within that context, one of the most important efforts of this type has historically been the search for a rest mass of the photon. The effects of a nonzero photon rest mass can be incorporated into electromagnetism straightforwardly through the Proca equations, which are the simplest relativistic generalization of Maxwell's equations. Using them, it is possible to consider some far-reaching implications of a massive photon, such as variation of the speed of light, deviations in the behaviour of static electromagnetic fields, longitudinal electromagnetic radiation and even questions of gravitational deflection. All of these have been studied carefully using a number of different approaches over the past several decades. This review attempts to assess the status of our current knowledge and understanding of the photon rest mass, with particular emphasis on a discussion of the various experimental methods that have been used to set upper limits on it. All such tests can be most easily categorized in terms of terrestrial and extra-terrestrial approaches, and the review classifies them as such. Up to now, there has been no conclusive evidence of a finite mass for the photon, with the results instead yielding ever more stringent upper bounds on the size of it, thus confirming the related aspects of Maxwellian electromagnetism with concomitant precision. Of course, failure to find a finite photon mass in any one experiment or class of experiments is not proof that it is identically zero and, even as the experimental limits move more closely towards the fundamental bounds of measurement uncertainty, new conceptual approaches to the task continue to appear. The intrinsic importance of the question and the lure of what might be revealed by attaining the next decimal place are as strong a draw on this question as they are in any other aspect of precise tests of physical laws.
Print publication: Issue 1 (January 2005)
Received 11 July 2004
Published 23 November 2004
And there is this one:
http://www.aip.org/pnu/2003/split/625-2.html
Number 625 #2, February 19, 2003 by Phil Schewe, James Riordon, and Ben Stein
A New Limit on Photon Mass
A new limit on photon mass, less than 10-51 grams or 7 x 10-19 electron volts, has been established by an experiment in which light is aimed at a sensitive torsion balance; if light had mass, the rotating balance would suffer an additional tiny torque. This represents a 20-fold improvement over previous limits on photon mass.
Photon mass is expected to be zero by most physicists, but this is an assumption which must be checked experimentally. A nonzero mass would make trouble for special relativity, Maxwell's equations, and for Coulomb's inverse-square law for electrical attraction.
The work was carried out by Jun Luo and his colleagues at Huazhong University of Science and Technology in Wuhan, China (junluo@mail.hust.edu.cn, 86-27-8755-6653). They have also carried out a measurement of the universal gravitational constant G (Luo et al., Physical Review D, 15 February 1999) and are currently measuring the force of gravity at the sub-millimeter range (a departure from Newton's inverse-square law might suggest the existence of extra spatial dimensions) and are studying the Casimir force, a quantum effect in which nearby parallel plates are drawn together. (Luo et al., Physical Review Letters, 28 February 2003)