Quote by Passionflower
I know some disagree but I think that time is a path in spacetime not a dimension of spacetime.
One can choose a coordinate system as such that the path in spacetime overlaps one axis (which we then call time) but such a coordinate would only be valid for user at rest to this coordinate system in flat spacetime. In curved spacetime even that is no longer true.

You may be on to something, Passionflower. Could you expand on that idea a little? For example, what is the 4th dimension then, if it is not always time? And is it different in curved spacetime?