The thing that I really have trouble wrapping my head around is where each "thing" begins and ends, ex. for astronomically large bodies that take light years to travel across, how does it move and how does information propagate through it? I assume the simplest way to think of it is for every atom to have its own bar in the graph, and every "thing" is kind of "wiggly" as information travels through it.

But then that sounds like I'm describing the speed of sound, no? Maybe I'm confusing two concepts.