Hey I think I've figured out 4th dimension speed. (speed of time)
The big bang expanded the universe, throwing light in all directions, and also throwing the edge of the universe with it.
So it must be conceived that the universe and all it's space are expanding at the same speed as that of light. So, c=u
where "U" = the speed of the universe expanding, and "C" = the speed of light
According to Einstien, space and time are the same thing.
So, assuming the theories of Relativity and the Big Bang are accurate, the speeds of: light, the universe expanding, and time are all the same.
C=U=T
Where "C" = the speed of light, "U" = the speed of the universe expanding, and "T" = the speed of time.
Time moves at the speed of light.