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Another Passage of Time Question

  1. Jan 4, 2008 #1
    If the universe were deterministic à la Laplace's Demon, in the sense that every event - every physical phenomenon and every attribute of physical phenomena - is completely and necessarily caused by previous events then all of time, past and future, is merely a stack of moments and our conscious experience of time passing is simply like a pointer moving along the stack of moments. (Well, not strictly a stack of moments due to relativity, but something like a mathematical partial order of them.)

    But if on the other hand the universe is really non-deterministic - not in the sense that humans are unable to predict the future even with unlimited information, but in the sense that the particular outcomes of interactions within quantum phenomena that we can't predict with certainty are uncaused - then does it become a legitimate question: What is special about the present moment that makes it the point at which the uncertain probabilities of the future coalesce into the apparent certainties of the past?

    Of course, one possible response is that only the parts of the past which we have present evidence of are actually certain, so the past isn't really that certain. But I'm really more interested in whether people think that's a scientifically intelligible question or if there's a better way to formulate it. It seems important because possible answers might be related to the nature of consciousness.
  2. jcsd
  3. Jan 4, 2008 #2
    I'm not sure If I understand the question correctly. The only quantity I can think of that will allow us to distinguish past from present is entropy. Entropy roughly speaking is proportional to disorder of matter, and energy. According to the second law of thermodynamics, entropy increases with time. So the disorder of the universe increases.

    The difference then between past and future is that the future will be more disordered.

    Also, from Chaos Theory there is a concept of the "strange attractor." The strange attractor is sort like a subset of certain outcomes of events that were generated randomly. So in a sense, random behavior might exhibit a pattern of regularity. We have observed this phenomena in nature, but we don't know whether or not there is a strange attractor for the entire universe.

    Hope that helps.
  4. Jan 4, 2008 #3
    Thanks for the response waht. I'm sorry, I realize I was being pretty opaque with my language. Let me try again:

    Back when everyone thought the universe was like a huge clockwork, a continuum of determined events, our conscious experience of the present would simply be like playing a movie, reeling through a pre-ordained history.

    But quantum phenomena look as though they're a product of some degree of randomness. If they really are, if what's going on at the quantum scale are indeterminate uncaused "events", does it make sense to ask why it's in the present moment that the indeterminate future becomes the determinate present and determinate past, rather than that resolution of indeterminacy occurring at some other moment in the past or future instead?

    It might also help to check out solidon's passage of time thread, I formed this question while thinking about his.
  5. Jan 4, 2008 #4


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    From what I gather, there is some degree of unknown-ness as to whether quantum mechanics actually explains what the hell is going on, or simply is a formalism that says with such and such a starting point you will find that such and such an end point is most likely. So it could very well be the case that it's deterministic but also very complex so quantum mechanics would be a simplified description of what's actually going on, in the same way that Ohm's law is a very simplified description of what's going on in a wire. Of course I'm not qualified to talk about anything with the word "quantum" in it so that's as far as my knowledge goes.

    Your question answers itself because it's circularly defined - the present is significant because it marks the point where the future is observed and hence becomes the past. In other words, the past is the set of all events that have been observed, and the future is the set of all events that may possibly be observed. The present, to go back to your computer analogy, would then be like a function which takes psuedorandom data (the future) as its input and outputs a set of constants (the past) that describe that data, in other words, it takes the randomness out of the future.

    You could also denote the present as what processes everything in the past, using concretely known information from the macroscopic world and psuedorandom information from the microscopic world to create new constants. In another way, let's say an object with a displacement s is moving at a velocity v, already, and has a function that describes its acceleration. Then the 'present' would simply be the point in time that v and f(s) are integrated to give a new co-ordinate for s. That happens continuously the same way a curve on a graph changes gradients continuously over time. So the present would then be a set of mathematical operations, taking the description of everything in the universe and carrying out a set of calculations that then gives the next basic properties of each thing in the universe (such as charge, mass, etc) and what carries out those operations? Light? Personally something like that forms my idea of 'god', a grand computer of which we are the currently running program.

    I don't how else you can answer this question.
    Last edited: Jan 4, 2008
  6. Jan 4, 2008 #5
    Thanks, dst. Yeah, from my understanding the assumption of indeterminacy / randomness in quantum mechanics is just that it's the simplest thing to work with, rather than being drawn from any positive indications that the universe is indeterminate. But there do seem to be some physicists who think that the indeterminacy is "real". I'm hoping to attract some of the heavy-duty physics guys around here to find out if they think the question makes sense.

    I don't think I'm using circular definitions because you picked up what I'm suggesting - that the present, rather than simply being our viewpoint traversing "spacetime", is additionally processing or altering it in some way that relates to quantum indeterminacy. Sorry if I'm continuing to be obscure or opaque in the way I'm talking.
  7. Jan 11, 2008 #6
    There is no empirical way of testing whether time flows or if the entire universe is stationary at the instantaneous time in which we are now I think.
  8. Jan 12, 2008 #7

    But the past and the future do not exist as such, do they? Only "now" is part of the world, isn't it? All what's left of the past are the traces of what has happened. And our conception of future is connected to our intuitive understanding of how the system we are in functions.

    Biological systems certainly seem to be not deterministic. The survival of an individual can rely on whether a cell is hit by radioactivity from decay of particles - decay which seems to be governed by probabilities. On the other hand the survival of an indvidual can make the difference in whether a species evolves to be able to manipulate the surroundings in one way or another.

    In what way does it seem to you that the answer of whether the world is deterministic or not is related to consiousness? I ask,beacuse I am curious about it but also because the concept of future - as far as I have understood it - is heavily related to the function of our brains. It is possible that the main point of our mind is to predict what's going to happen next. This ability to predict the future is very important for our chances of survival and hence succesful reproduction. But would it make a difference to the usefulness of predicting the future whether the world simply is played back og not?

    - Hernik
  9. Jan 13, 2008 #8
    That depends upon how entirely you think your conscious perceptions reveal the existent world to you.

    Because human consciousness seems to exclusively experience the present, rather than the past or the future or multiple points in time.

    If the universe is non-deterministic, and therefore the present is the point at which the possible values of QM entities become certain values in their interactions with each other, it seems that the present's other status as the point in time which consciousness perceives may be more than coincidence. Or it might just be a trick of perception, from having to ask such a thing with conscious thoughts.
  10. Jan 13, 2008 #9
    Well as I understand the mind, the experience we have in our head is to a very high degree something the mind generates. The mind gets input from the senses and checks in the memory what to think of the input. It then generates a sort of movie - somewhat like a 3d-model complete with what you think other people might think and so on - of the world around you in a way so that you do not experience the world as such (This is maybe why we have such difficulties understanding quantum mechanics and have to just shut up an calculate!) but experience a representation of the world build on your expectations, your former experiences and your sensorial inputs (and probably more). Now many of the sensorial inputs are mingled with before they reach the mind. The eye for example has build in mechanisms which act as amplification and filtering on the signal going to the brain. Anything that moves will be amplified. Anything that has high contrast will be amplified. And so moving objects or lines or points representing high contrast have a higher chance of ending up in your consiousness and thus be part of your experience. Anything that the mind thinks it already knows is just filled in without any consideration. That's how the magician tricks you.

    Another reason to not believe we conceive the world as it is, but rather as we think it is is, the fact that we can only hold three to four things in our consiousness at once. So the rest has no way of becoming part of our world. You know it from when you for example have a small pebble in the shoe but because you are busy doing something you find important it is not until you relax that the pain from your foot becomes part of your experience and start to irritate you. So there is nothing like a real world in a mind. We each live in our own as far as I understand, mice, men, bird, fish all experience a world which makes evolutionary sense. No need to waste thoughts on something which is not important.

    The senses deal with the input they get right now. That puts a limit on the mind. And it becomes an anchor which keeps your mind from drifting away. But the human mind may be anywhere in my opinion. You read a science fiction novel and you're in the future. Or you think about how your kid is doing at the ball game, and you're are there for a short instant. You can be other places than where the senses can register your surroundings. Also you don't have to sit behind your eyes and look at the world from there. You can close your eyes and try to guess a thing somebody placed in your hands and you will notice your consiousness seems to be in your fingertips instead of in your head. Some people have out of body experiences and fly in the room looking down on themselves. You can be anywhere your mind can imagine - anywhere it can construct from memory - also places it has never been. It's a very flexible thing that world, your head lets you be in. But because you only get sensory inputs from "now" - and because of course what can happen to you happens now and not then and not in the far off future - that is where the consiousness is rooted. It is now the lion might eat you - not in two years or yesterday - it makes evolutionary sense to be aware of the very instant now.

    That's my opinion.
  11. Jan 21, 2008 #10
    I can see how in an otherwise indeterministic universe with a "determined" past the "point of determination" might be at some point in the future rather than at the precise present moment (how could we tell? - interesting to think of possible experiments that might throw light on this) - but I don't see how this "point of determination" could be in the past?

    The problem, however, is that there is no way (as far as I know) that you can prove conclusively that the world IS either strictly deterministic or indeterministic - so what hope do we have of showing (assuming that its indeterministic) that the point of determination is either in the present or the future?

    The whole "ugly" and asymmetric nature of having an indeterministic future coupled somehow with a determined past is (to me) one of the strongest arguments in favour of the more beautiful deterministic 4D block universe view.
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