Time I got back to time.
Time/Space is the 4th Dimension that is created by gravity
I'm going to leave inertia alone for now and skip ahead. I'm not crazy about how Aaron handles this so I'll just give you my version which I'm only slightly happier about. Again, "Space" has but 1 actual dimension, space. Various coordinates can be used to locate points within. We think volume (3D) vs. plane (2D) vs line (1D) but it can all be seen as contained by and definable within the same space.
But what of Time? Dimension? Maybe. I don't think so. I think of it as a higher order point coordinate in Space. Time is more important than x,y, or z because the distance between two points will often depend upon what time it is, and less so vice versa. Though we measure time in periodic increments, it simply marches on and clearly doesn't care. One might ask for the time, another answer "2 o'clock," and the first respond "What year?"
In outer space we most often measure time in light years. We observe the speed of light as a constant because the Aether makes it appear so regardless of its local density. Time may simply be motion through the Aether. Aaron describes it as being relative to the movement of the local Aether, but I don't think the Aether necessarily moves. I just see its density changing which seems all that's required. May help explain why some have seen results with an interferometer while others didn't.
If one could have an absolute perspective, they could see light travelling faster in less dense Aether and slower where denser. But, in reality, as light enters our hood, the Aether makes it all look and measure like it's going c. How's this amount to an "arrow" and stuff? I dunno.. Maybe get back to it eventually..