We introduce the scales T, L, and V for time, distance and speed respectively. They represent magnitudes of the different parameters which give large changes in f . By large we mean that ∂ ∂ f ∂ ∂ t T ∼ ∼ f | ∂ ∂ f ∂ ∂ r | L ∼ ∼ f | ∂ ∂ f ∂ ∂ v | V ∼ ∼ f .