Dear Dan,
Your post is very important. Indeed, the notion of time is fundamental in order to develop a physical theory. We have to come back to an old debate between Albert Einstein and Ernst Mach concerning the relativity. Ernst Mach thought that all was relative (speed but also acceleration) whereas Einstein has postulated that all is relative with respect to the speed of light and thus nothing can go faster than the speed of light. For another reason, Albert Einstein has introduced the notion of light quanta: the photon. Concerning time, there is a similar debate. You can think that time is totally relative (see the fantastic book of Julian Barbour "The End of Time") or you can think, as me, that time is defined relative to the speed of light. I have developed this idea and I have given a definition of time: "The time coordinate ct represents the possibility of motion for the matter relative to the speed of light c along the geodesics defined by a metric g" (see http://cel.archives-ouvertes.fr/cel-00511837) and then time comes from the time coordinate but it is not a fundamental variable of the General Relativity. Then I have tried to extend the idea of relativity with respect to photons to the fundamental particles. Actually, you can obtain all the fundamental particles starting with photons only, as an evolution of photons depending on the temperature (see the previous posts). Somehow, the fundamental particles are defined relative to photons (I have made a mistake concerning the bosons corrected by Cristi). The next step was to postulate that the fundamental element in the universe is the photon. This is a very different philosophy than the one of the Quantum Gravity, but this is the same goal. The last step is to see if there is a problem with the initial singularity. To my mind, this problem can be compared with the Hawking radiation. If you have only photons at the boundary of the Planck epoch, and with the previous definition of time, the notion of time falls down. Indeed, the notion of time starts with the first pair production at the boundary of the Planck epoch. The Planck area is well defined with known particles: the photons, but there is no time and thus the motion is not defined.
I will read your essay with pleasure.
Emmanuel