Here's the worldline of a particle in a Spacetime Diagram:
(1) [typical spacetime diagram]
The units of t are seconds and the units of x are meters.
A problem with the diagram is that it treats time as ontologically the same as space. Many philosophers of time hold that time, whatever it is, is not just another dimension of space.
How does one impart actual change ("superseconds" or "qualitative seconds" or "Kairos" or etc.) to this ontology? So suppose we modify the Spacetime Diagram above to one with a "meta time" (it's a kind of "SpaceSuperTime Diagram"):
(2) [same diagram but with a selected point moving along the (static) worldline in a time t' (tangent to the curve)]
This this diagram we imagine that the particle is moving along the static worldline, in a kind of meta-time I've called t'.
The question is, does the second diagram add any information to the first?