Ulam began imagining how, in a one-dimensional universe, cosmology might evolve. “Has anybody considered the following problem—which appears to me very pretty,” he wrote to von Neumann in February 1949. “Imagine that on the infinite line –∞ to +∞ I have occupied the integer points each with probability say ½ by material point masses—i.e. I have this situation,” and he sketched a random distribution of points on a line. “This is a distribution at time t = 0.”
