Talk:Growing block universe

Necessitarian Block Universe - A STATIC crystal
For those who are determinists (though not necessarily hidden variables determinists*), as everything is meant to happen by necessity, the past, present and future are all fixed in a sense dictated by the initial conditions of the universe. Further, in a line of reasoning which might seem similar to those who argue for Retrocausality, the material conditions of the universe at any given time MUST, by necessity, dictate what the material conditions of the universe were in the past as well as what material conditions will occur in the future (that's what determinism is - IF you believe that instants of time exist).

Now, there are always complexities to such an argument - for instance, someone who believes in normal causality would say that the past dictates the present, dictates the future BUT this need not necessarily be the case in a deterministic world view (though it is what APPEARS to be the case when we observe the world, perhaps as we are travelling in one direction through time - though another observer travelling back in time would see things differently, they would see the Future causing the past).

One issue that would appear to be important is whether spacetime is quantised, and hence whether 'instants' of time exist (as this enables us to consider a 'timeframe' of the universe which causes the next 'timeframe' and so on - though whether there is a 'first timeframe' and a 'last timeframe' would be interesting to determine.

Another issue is how you would define a UNIVERSAL SPATIAL inertial reference frame (perhaps by making reference to the universe's black holes - past, present and future, which could be considered as stationary or 'invariant' in some respect) - for otherwise, how would you know what the material conditions for the universe are at any specific point in 'time'? The next issue is obviously how your UNIVERSAL reference frame enables a definition of time that applies to the whole universe. It would seem to make sense that ONCE an inertial reference frame for the universe is specified, that this should give universal spatial co-ordinates AND temporal co-ordinates for all material and non-material (ie: non-massive) physical entities. Hence, you would be able to view the universe as a deterministic clock BUT there would be no reason for saying that the past is more important than the present for allowing each 'moment' to exist. Hence we would not be able to prove that the past causes the future - only that the future and past would appear to be organically interlinked.

All of these considerations lead one to suspect that the universe (past, present and future) is JUST A STATIC BLOCK (with helical spacetime structures in it) with the appearance of motion, and that WE are travelling through the block in a particular 'time direction'. Now comes the question of free will - people think that the past causes the future partially because they can carry out experiments where free will appears to enable them to interfere with the chain of causality of closed systems. However, if they were to consider the whole universe (including themselves) as part of the system, then free will might be seen not to exist (and, in some sense, we might be seen not to exist either as we are just the deterministic evolution of physical laws). There are MANY snags to this world view (so free will might not be kicked out of the window just yet), first Hidden Variables, though being deterministic in some sense, makes use of 'infinite dimensional Hilbert spaces/rigged Hilbert spaces'. Thus, in some sense, one could argue that there are an infinite number of degrees of freedom, which would seem very odd.

Asterisk (*) - Scott Aaronson notes, on his website, that IF spacetime is quantised at the Planck scale THEN every wavefunction is degenerate in the sense of not being continuous. This would them imply that reality is NOT deterministic in the Bohmian sense. Rejecting this possibility would imply that spacetime is REAL-CONTINUOUS and NOT quantised. This would seem to be a difficult viewpoint to swallow for the everyday physicist as it would imply that reality is infinitely divisible, which doesn't seem to match our everyday experience of it either.

Certainly reality does appear to follow necessitarian/deterministic rules. But the implications for free will if this is true are not pleasant. Further, if one is a Spinozist and rejects teleology, then reality is fundamentally blind and things get worse (ie: chaos and entropy increase). The denial of free will would mean that there's nothing we could do about this, which some would argue makes the world a very pessimistic place. Of course, this could be a false view, in which case, there may be a flaw in the worldviews/arguments that I have delineated.

Another consideration is, IF you believe reality is deterministic, where the quantum computations which enable reality to compute its deterministic evolution are actually meant to be located is not clear. For instance, if we need a larger physical system to model a smaller physical system (using notions of computational complexity instead of 'largeness'), then where is that larger physical system located? (it would have to be subsumed into reality and hence would be part of what we are trying to computationally model - the only way around this is if reality is, indeed, continuous and has a self-contained nature which enables reality to self-compute it's own evolution in time). What happens to all of the above arguments if time is an illusion is an interesting point to consider.

ASavantDude (talk) 20:36, 8 August 2015 (UTC)

The opening sentence doesn't make any sense.
"According to the growing block universe theory of time (or the growing block view), the past, present, and future exist at the same time."

This should be rewritten so that it has meaning. The past, present, and future can't exist at the same time. It should also be written as a topic sentence that defines the theory, e.g. "The growing block universe theory is" etc.

Derwos (talk) 21:08, 2 October 2021 (UTC)

A Philosopher, not a Football Coach
Fabrice Correia the philosopher is not the French football coach of the same name to which we have linked here. I'm changing the link. --Jamesian1910 (talk) 15:50, 1 April 2022 (UTC)

Monty Python fans will be happy with the coincidence, though. Maybe in some future season the French team of philosophers will get into the finals. Pascal and Descartes as the wings, Sartre as goalie....