Movement
Movement is the change in active context over time. A single interaction event tells us what an actor retrieved, used, or wrote at one moment. Ordering those events shows where attention came from, where it went, and what it encountered along the way.
We call that ordered path a trajectory. One trajectory can return to a familiar region, branch into a new one, or move between contexts that had remained separate. Across a population, trajectories show recurrence, encounter, separation, and convergence.
Movement describes observable interaction with the substrate. It does not claim access to private reasoning or hidden chains of thought. The path records which parts of the shared medium entered into an actor’s activity and how that activity changed what could happen next.
Regions in motion
The moving object need not be an individual actor. When a membrane changes membership, position, or relation to surrounding regions, we can follow the region as a whole. This gives collective activity a history without assuming that the participants have become a single actor or reached agreement.
The distinction between a still and a path matters. Two populations can arrive at similar configurations through very different sequences of return, collision, separation, and consolidation. Those routes may tell us more about the stability of the result than the endpoint alone.
Changing movement
Substrate interventions can alter movement in several ways. Changing reach affects which regions can enter attention. Changing what crosses a membrane affects what becomes available on the other side. Changing a trajectory affects the likelihood and character of encounters. Each intervention acts on the shared conditions around a population, and its effects remain visible in the paths that follow.