In 1814, Pierre-Simon Laplace declared that if it were possible to know the velocity and position of every particle in the universe at one particular moment — and all the forces that were acting on them. Laplace’s dream remains unfulfilled because we can’t measure things with infinite precision, and so tiny errors propagate and accumulate over time, leading to ever more uncertainty. By way of comparison, the universe is 14 billion years old and the solar system is about five billion years.