The Crystallizing Block Universe

The Flicker-Filter stuff on New Thinking Allowed (this thread) recalled this idea:

Time and Spacetime: The Crystallizing Block Universe

Ellis & Rothman

The nature of the future is completely different from the nature of the past. When quantum effects are significant, the future shows all the signs of quan
tum weirdness, including duality, uncertainty, and entanglement. With the passage of time, after the time-irreversible process of state-vector reduction has taken place, the past emerges, with the previous quantum uncertainty replaced by the classical certainty of definite particle identities and states. The present time is where this transition largely takes place, but the proces s does not take place uniformly: Evidence from delayed choice and related experiments shows that isolated patches of quantum indeterminacy remain, and that their transition from probability to certainty only takes place later. Thus, when quantum effects are significant, the picture of a classical Evolving Block Universe (‘EBU’) cedes place to one of a Crystallizing Block Universe (‘CBU’), which reflects this quantum transition from indeterminacy to certainty, while nevertheless resembling the EBU on large enough scales.

There's also a layperson article on Plus Maths by Kate Becker:

The crystallising Universe

The view that the past, the present and the future are of exactly the same physical character seems to be supported by Einstein's special theory of relativity, which describes how observers moving relative to one another may disagree about the order that events occur, preventing them from defining a unique and universal now (see the Plus article What is time?). However, in his prize-winning FQXi essay On the flow of time Ellis maintains that the most important property of time is that it unfolds. The past is already written, yes, but the future contains endless possibilities. To Ellis, the history of the Universe is a film that is still being made.

"People must take seriously the fact that time does evolve," says Ellis. If the models don't jibe with our perception of reality, he argues, maybe the problem is with the models. "Some of my colleagues seem to think their models trump reality!"

Ellis, along with his collaborator Tony Rothman at Princeton University, New Jersey, is proposing a modification to the standard block Universe picture in which the present marks the boundary between the flexible future and the frozen past, the moment when the film rolls through the movie camera and is imprinted with an indelible image. They dub this the crystallising block Universe.

It's a nice idea, but just how does the present become the past in this picture? Ellis found an elegant answer in quantum mechanics. In the quantum world, particles do not exist in a definite state until they are observed. Prior to observation, they are mathematically described by a wavefunction that encompasses all the possible states and properties that could be attributed to them. Ellis argues that the present is the moment when these quantum potentialities are transformed into a single observed reality. As physicists put it, the wavefunction collapses.
In the crystallising block Universe time does not roll out quite as uniformly as film spooling out from a reel. Wavefunctions created at the same moment need not collapse in unison, Ellis points out. Two photons, created in the same instant and headed toward a physics experiment where they will be observed, may hit the apparatus at different moments. One photon would then move into the past just a little sooner than its twin.

There is another pretty dramatic wrinkle in the neat line between past and present, too: sometimes, the present can influence the past.

Muller has a similar idea:

In exploring the ‘now,’ new book links flow of time with Big Bang

Muller’s new idea: Time is expanding because space is expanding.

“The new physics principle is that space and time are linked; when you create new space, you will create new time,” Muller said.

Muller takes his lead from Albert Einstein, who built his theory of general relativity – the theory that explains everything from black holes to cosmic evolution – on the idea of a four-dimensional spacetime. Space is not the only thing expanding, Muller says; spacetime is expanding. And we are surfing the crest of that wave, what we call “now.”

“Every moment, the universe gets a little bigger, and there is a little more time, and it is this leading edge of time that we refer to as now,” he writes. “The future does not yet exist … it is being created. Now is at the boundary, the shock front, the new time that is coming from nothing, the leading edge of time.”

Because the future doesn’t yet exist, we can’t travel into the future, he asserts. He argues, too, that going back in time is equally improbable, since to reverse time you would have to decrease, at least locally, the amount of space in the universe. That does happen, such as when a star explodes or a black hole evaporates. But these reduce time so infinitesimally that the effect would be hidden in the quantum uncertainty of measurement – an instance of what physicists call cosmic censorship.