@ong: how about this little tidbit:

note: You can scan back to some of the earliest discussions in this thread to brush up on the relativistic gamma factor, but it works like this:
The faster you go, the more space is contracted in front of you, the more time is dilated all around you, and the more force it takes to accelerate you. That last one is known as the increase in relativistic mass.

As an object's speed approaches the speed of light, that object's relativistic gamma factor approaches infinity. Meaning that the amount of force needed to accelerate it AT ALL is approaching infinity. The result is that nothing with mass > 0 could possibly ever be accelerated to the speed of light, as it would require more energy than the universe (or any universe) can produce by any fathomable means.

Furthermore, if anything which has mass > 0 is actually moving at the speed of light, then it has infinite relativistic mass, and would exert infinite gravitational effect on the universe.


If photons have non-0 mass, then they MUST travel at less than the speed of light.
QED

In order to argue that photons do not move at the speed of light in vacuum, then you need to unravel Einstein's GR. GR is widely accepted as the most elegant theory in all of human history. It is entirely built on the most basic and simple assumptions and it gives us so many predictions. Plenty of these predictions were considered absolutely not physical 100 years ago. Yet, 1 by 1, every one of the predictions to be explored has turned out to be an observable physical phenomenon.

This is not to discourage you. It's to tell you where to start on that Nobel Prize you'll earn for getting this right.