We will work in d spacetime dimensions with coordinates ( t , r , x 1 , . . . , x d − − 2 ) where r ≥ ≥ 0 and − − ∞ ∞ < t , x 1 , . . . , x d − − 2 < ∞ ∞ . The line element for a spacetime that is stationary, time reversal invariant, space inversion invariant, rotationally invariant