Suppose I write a hurtful insult on a piece of paper and hand it to you... Remember that light has no mass. Like magnetic fields, light exists in no physical form. When the insult on the note travels across the light path from the note to your eyes it is completely nonphysical for the duration of the trip. The insult encoded in the light is no more real than a horizon. It is a pure transfer of probability from me to you... You might get angry and your neck and forehead might get hot... Light is the messenger of probability, but neither the light nor the message has mass. (page 87-88)
On a side note: Something that bothered me when I was in uni was black holes. They have such a strong gravitational pull that it even pulls in light. But if light doesn't have mass, then how is it affected by gravity? Maybe someone can shed some light on this subject in the comments...
The argument in this chapter is saying that light enables more probabilities. This means that stars produced lots of energy as more God dust pops into existence on top of each other. Also the distance light can travel sets the limit on how far a bit of God dust can travel between popping in an out of existence. (Next time you go to a casino you should also bring some high powered torches with you.)
This book seems to suggest God is now controlled by both something that allows matter to pop back into existence (see point 3 here) and also the limits of the speed of light. This idea makes sense in the framework laid out as if God is in matter. A God that is subjected to his own limits of the universe, seems to not be that powerful at all, in fact it sounds like God would be trapped by his own creation.
Light is an interesting thing. It overcomes darkness. It is needed for life. It has two seemingly contradicting natures as it behaves like a wave and a particle. I wonder if for these reasons the God-man Jesus chose to refer to himself as light.