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What I mean is, is there a past, future and present? or just a NOW which changes?

I'm a computer programmer so the second alternative is from my programming experience. In this second alternative, I mean to ask, are we just in a stateful system like Conways game of life where there is just a NOW and then the system updates and then we are in a different NOW. In the conways game of life, there is never any past stored in the computer memory. In this case, the past is just an illusion from us recording events which have happened in our brain.

There is a distinct difference between the two, if there is actually a past, future and present then there is opportunity for things in the future to affect things in the past or time-travel might be possible. However in a stateful system like the game of life, then that really cannot happen.

Secondly, do any experiments confirm or deny either of these two options, is this already a decided problem in physics?

Conways game of life

Updated:

A system with a "real" (real as I describe) past, present and future could allow for travel in the time dimension just as you would travel in the x,y or z dimension. One person could travel slowly backwards in time to a point in the past, then move forward slowly and see events as they happen slowly. Not everyone is moving "forwards" together like in conways game of life. In a conways game of life, everyone is moving forwards.

In a system with a real time dimension, potentially a person could make a machine to move backwards, which you cannot do in conways game of life, you cannot move backwards to the older state, you cannot see time in reverse as well which you would see if you moved backwards as you would with a film playing backwards or sound recording playing backwards.

The rules of the conways game of life wouldn't permit travelling backwards, so there's no real time dimension to it, only a collective NOW.

The distinction between a system with a real time dimension (as I describe) would be that you can move forwards or backwards in the time dimension.

In a world without a real time dimension there is only conways game of life where everyone is moving forward and there is only a NOW at all times.

Now you could say that the system which I described with a real time dimension could be simulated by a suitable conways game of life, a suitable rules based system, but I think that you could make a distinction between the two, just as you can determine there is a real x dimension in 3 dimension space which is not a result of a conways game of life in the x dimension.

So my question is, is there a real time dimension or is there just a now that everyone is at all the time?

This question was closed because I have not proposed an experiment which can distinguish between the two conditions. Using the same argument, any discussion of string theory should be closed as there are no existing experiment which provides testable evidence of string theory and therefore it should be considered as much as a fiction as the difference between the two cases I suggested here.

Also by my own reasoning, anything fictional should be considered a valid question. :)

Phil
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  • Actually, Phil, this is not a topic addressed by physics in part because there is not any observable difference between the two interpretations. A "stateful system" can simulate time travel just as well as if there is "actually" a past, present, and future, for example. You might have better luck taking this question to [philosophy.SE]. – David Z Dec 13 '11 at 10:00
  • how can time travel be possible in the stateful system I described? If someone time travelled backwards in time, although they are in a different "state", the people he left behind in the future are still going on with their lives. In this case, it is different to the stateful system I described. – Phil Dec 13 '11 at 13:28
  • I mean, the stateful system I described cannot do time travel because it cannot go backwards according to the rules. ... well, I see a difference between the two systems. I had hoped others would see a difference. – Phil Dec 13 '11 at 13:59
  • I think its amazing that this is seen as a physics question http://physics.stackexchange.com/q/2605/ which I would consider a biology question, but this question is not. – Phil Dec 13 '11 at 14:17
  • If you can propose an experiment which would distinguish between your two interpretations, that would be a first step toward making this a physics question. – David Z Dec 13 '11 at 15:02
  • The Game of Life doesn't allow time travel, only because of its causal structure. You could have a cellular automaton with time loops; but certainly then you have to think of all times as existing... I posted about nature of time here http://philosophy.stackexchange.com/q/1683/ – Mitchell Porter Dec 14 '11 at 01:51
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    Mitchell, any computational system can fake time loops, the system could return to a previous state or hold state within its system. I.e. it can be a simulation of a system which allows past, present and future. However, everything could be a simulation of course. However, it is still not the same as a system which has a real past, present and future. – Phil Dec 14 '11 at 02:57
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    @Phil There's a loop in the title... – Volker Siegel Jun 18 '14 at 11:26
  • duplicate of http://physics.stackexchange.com/q/13001/ actually. as one cannot go faster than light one cannot travel backward in time. – anna v Jun 18 '14 at 17:22
  • I would say that while a question without experimental answer is not really scientific, it may be considered as valid for physics discussion because how do we think about the system is also important, not just what experimental results we predict. Otherwise, questions about which models are better/more useful won't be discussed here?

    I think you will be interested in reading about Julian Barbour, a proponent of timeless physics: http://en.wikipedia.org/wiki/Julian_Barbour. He mentions the Wheeler-DeWitt equation as an example of theoretical formalism that doesn't include time

     – guillefix Jun 18 '14 at 20:26
  • Here is a talk which I haven't watched, but seems to cover the same as one which I have seen at our physics department: https://www.youtube.com/watch?v=1ogiQ2E6n0U – guillefix Jun 18 '14 at 20:29
  • "A stateful system which is updated" is exactly the formulation I was looking for for some time now, but could not say it so succintly. Considering this off topic because the two options cannot be distinguished is a bit short sighted, because analysing the question may change exactly that. Except if there is a mathematical proof of indistinguishability. Nevertheless I understand the decision. – Harald Feb 27 '15 at 06:35
  • Why would only one now exist if past and future is part of the state? Parallell/Threaded reality... would be confusing :-) – Emil Aug 16 '16 at 05:41

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