I think I get the 4d velocity vector and the limit implied by the length of this. I also think I get the difference between a massles particle and a body with rest mass with this way of thinking of things.
The part that I don't get and would appreciate some further explanation of is -
Stationary observers watching you are still moving through time as normal, so you do not appear to have the near infinite velocity you are experiencing. They will see your vector as tipped 45 degrees, equal amounts in time and space. This is what we usually call 'the speed of light'.
The idea of moving in time at the speed of light is in itself quite bizzarre....
So what does this tell us about the rate of the expansion of the universe? Or is the point that I was originally missing the very fact that this has nothing to do with the rate of the epansion of the universe and that the two have absolutely no bearing on each other?