@mark noble,
Light has no Mass, ever. "IT" is NOT a PHYSICAL object, that could just sit on the table, motionless. So talk about measuring its "mass" when stationary is moronic, or suggesting that it possesses a different mass at speed is also just as moronic.
How much mass does Love have? Or hot? or Time?
None, because they are not OBJECTS. They don't PHYSICALLY exist.
Physical objects have dimensions, volume, density, Mass, and have properties such as temperature, conductivity etc.
Light has NONE of these attributes.
Nothing is actually "physically moving" from the source to the illuminated object. The effect of light is propagating through the medium, but NOTHING PHYSICAL EXISTS that could "move".
The current Particle Theory of everything is moronic. (photons in this case)