I must put both of them because I want to have an idea of dynamics here, of scattering and of geometry at the same time. I will rewrite what I put in another thread: "Matter field is something that lives on a spin foam like electical fields on a electrical grid structure. Any possible experiment done by whoever lives on that grid will be like obtaing an eigenvalue of a surface operator. But what moves is the matter field, so any measurement of an area will be irrespective of its energy-momentum." By the way, when a measurement is made, a spin network is picked out of a spin foam, right? So, the area measured is one of a spin network.