English: The (x,s) coordinate chart of a maximally symmetric causal diamond. The coordinate s ∈ (−∞,∞) is the conformal Killing time, defined as the function that vanishes on the maximal slice Σand satisfies ζ·ds = 1. The coordinate x ∈ [0, ∞) is spherically symmetric and satisfies ζ·d x = 0 and |dx| = |ds|. Constant s and x lines are plotted at equal coordinate intervals of 0.5. Btw ds and dx are everywhere orthogonal, and for the line element in these coordinates.