There are also at least two event horizons: one at the largest solution of 1 − − 2 m / r − − H 0 2 r 2 = 0 , and space-like, protecting the Big-Bang singularity at finite past time; and one at the r = r − − smallest root of the equation, also at finite time. The second event horizon becomes a black hole horizon for the H 0 > 0 case.