We know through observations of distant SN that the deceleration parameter is negative and this implies that the universe is accelerating. This is just me but when I think about acceleration, I think of a vector quantity with units of m/s^2 and has magnitude and direction. do we know the magntude and direction of the accleration of the universe? i can see why there would be a magnitude maybe, but a direction? doesn't that violate the principle of isotropy and homogeneity? I guess i don't really get what it means for the universe as a whole to be accelerating. thanks!