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Philosophy of Time

Posted 4 years ago

If the universe is a deterministically evolving hypergraph - is the state of previous cycles preserved?

This is another way of asking (in this model) if the past is real? Is the future real? or is this model an example of Presentism rather than a Block Universe?

POSTED BY: Barry Silverman
11 Replies
POSTED BY: Jarek Duda
POSTED BY: Jarek Duda

I would say yes. Look up "rulial multiway graph" and you will see that there is a structure that does all rules on each step. Half of the rules would be to go "back" one step while the other half go "forward" a step, so not only is the present being generated by the rules, but the past and future are constantly being (re)generated.

POSTED BY: Jeff Yates
Posted 4 years ago
POSTED BY: Steve Paige

If I understood your reply - you are saying that the stepwise evolution of the hypergraph is deterministic, and unique for the whole universe. Is it correct to say that here is no concept of reference frame at this level of representation?

But - to any entity inside the universe - this stepwise evolution (represented by the hypergraph) is not directly visible - but is visible as a derived causal graph which represents spacetime in the reference frame of the observing entity.

If this is the case, would it not be easier to use a different terminology describe the t=0 => t=N evolution steps as something other than time?

Am I correct in assuming that any causal graph Time T will always point back to a unique Hypergraph step? They are not necessarily contiguous, or in the same order as the hypergraph?

POSTED BY: Barry Silverman
Posted 4 years ago

Particular hypergraph states are always reference-frame dependent. One possible ("cosmological)" reference frame is updating the entire hypergraph at once at each step, but other choices are possible as well.

And we are not generally using the word "time" to describe evolution steps, we either call them steps or generations.

For any single branch's causal graph, any space-like slice through it (including horizontal slices in between layers corresponding to steps) would produce a unique space hypergraph. But, of course, multiway branching is possible, in which case you would not get a unique graph at any given step.

POSTED BY: Max Piskunov
Posted 4 years ago

I should clarify that the hypergraph, which is the state of the model, represents only space at a particular instance in time (in some reference frame). And rules operate only on that hypergraph.

From these rule applications, one can compute a causal graph, which represents spacetime. But rules don't operate on the causal graph directly, which is why the past is "protected".

Whether the past is "real", I think, is a philosophical question that our model does not answer, and it seems to me it fundamentally depends on what "real" means. To compute the future evolution of the hypergraph (on any of the multiway branches) past is not needed, so in that sense, it is not real. Whether the past can be reconstructed from the present would be rule-dependent. However, the causal (i.e., spacetime) graph can be computed from the evolution. So the past does exist in that sense.

POSTED BY: Max Piskunov

Thank you for your reply. I did not understand that the evolution of the graph is not somehow relate to time as observed from inside.

How then, does the evolution of the system by running the rule relate to "time" as perceived by an observer inside the system? How is the Arrow of Time represented, and how is the portion of the graph representing the past protected from further "evolution" by future events?

POSTED BY: Barry Silverman

If the universe is a deterministically evolving hypergraph - is the state of previous cycles preserved?

This is another way of asking (in this model) if the past is real? Is the future real? or is this model an example of Presentism rather than a Block Universe?

POSTED BY: Arsalan Lavang

An interesting and subtle question!

Of course, our model is only deterministic up to measurement. As detailed in my quantum mechanics paper (https://www.wolframphysics.org/technical-documents/) different choices of quantum observation frame, corresponding to different choices of measurement sequence, generally distinct causal graphs (in much the same way as different foliation choices in the causal graph generally yield distinct spatial hypergraphs). So I'd argue that our model implies a refinement of the block universe concept, in which it is not spacetime (i.e the causal graph), but rather branchtime (i.e. the multiway causal graph), that is the invariant structure containing all past, present and future events.

POSTED BY: Jonathan Gorard

I was listening to the working session on April 30th, and Stephen seemed to be saying that Time is special, and the idea of a block future universe (where the future is "calculated" in advance) can't happen because of computational irreducibility.

Did I misunderstand the discussion?

POSTED BY: Barry Silverman
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