Today, Ellis and Rothman introduce a significant new type of block universe. They say the character of the block changes dramatically when quantum mechanics is thrown into the mix. All of a sudden, the past and the future take on entirely different characteristics. The future is dominated by the weird laws of quantum mechanics in which objects can exist in two places at the same time and particles can be so deeply linked that they share the same existence. By contrast, the past is dominated by the unflinching certainty of classical mechanics.
What's interesting is that the transition between these states takes place largely in the present. It's almost as if the past crystallizes out of the future, in the instant we call the present. Ellis and Rothman call this model the "crystallizing block universe" and go on to explore some of its properties.