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Arrow of time, or arrow of memory?

  1. Jun 28, 2005 #1
    "Arrow" of time, or "arrow" of memory?

    I need help understanding this.
    To me, it seems, well not to be over the top about it, but, well, pretty much ridiculous that there wouldn't be *the appearance* of an "arrow" of time that points in one and only one direction.
    Take the classic question of why no one has ever seen a broken tea cup jump from the floor and reassemble itself whole on a table.
    Well suppose for a moment that that actually did happen, right there in front of your eyes.
    What makes anyone think that there'd be any way at all that you could possibly remember it?
    It seems to me that, unless the time reversal was confined *strictly* to the tea cup, and nothing else, that as time ran backwards, it would also be running backwards with regard to *all* the processes occurring within your brain as well.
    As a result, as the tea cup, from instant to instant, was reassembling itself, moving from one state, to a previous state, to the state before that, the same thing would have to be happening in your brain.
    The human brain isn't magic.
    As it moved, from instant to instant, from one state, to a previous state, to the state before that, there would be no physical mechanism for you to retain the memory of any state representing one beyond what you would perceive as the "present" state.

    Think of your memory as a deck of cards.

    In the first instant you put down a 2 of diamonds.
    In the second instant you put down a 9 of clubs.
    In the third instant you put down a king of hearts.
    In the fourth instant you put down a 5 of spades.

    At this point your memory is clear. 2 of diamonds, followed by 9 of clubs, followed by king of hearts, followed by 5 of spades.

    Now consider what you would experience from instant to instant as time ran backwards.

    The 5 of spades would go back to where it came from, and in the first instant of time reversal what you'd remember is - 2 of diamonds, followed by 9 of clubs, followed by king of hearts.
    You wouldn't remember having seen the 5 of spades because the changes to your brain caused by seeing it would have been undone in the first instant of time reversal.

    So even though time is now running backwards, it would still appear to you to be running forward. What you'd remember after the first instant of time reversal is 2 of diamonds, followed by 9 of clubs, followed by king of hearts. The king of hearts would appear to you to be the present, only because it's the last thing in your memory stack.

    The time reversal continues. Now the king of hearts goes back to where it came from. You no longer remember having seen the king of hearts because the changes to your brain caused by seeing it have been undone during the second instant of time reversal.

    So now in the second instant of time reversal time STILL appears to be running forward, you remember it, clearly. The 2 of diamonds is followed by the 9 of clubs. In this second instant of time reversal the 9 of clubs now appears to be the "present", but only because the 9 of clubs is now the last thing in your memory stack.

    My point here is this. When ever time runs backwards, it would always appear to you to be running forward. All you'd remember is a continuous unbroken stream of time from the past, right up to whatever is the last moment in your memory stack, from instant to instant, and with each instant the "present" would simply appear to be the last thing in your memory stack that hadn't yet been undone by the time reversal.

    So the way I see it there's really no such thing as a "arrow" of time. The only "arrow" is the "arrow" of human memory. Time could be reversing, tea cups could be jumping from the floor and reassembling themselves all the time, but due to the "arrow" of human memory, none of us would have any way at all of experiencing that time reversal.

    The ONLY way, and I do mean THE - ONLY - WAY you could ever, under ANY conditions whatsoever, remember seeing a tea cup jump from the floor and reassemble itself is if the time reversal that caused it where *STRICKTLY* confined to the tea cup, but not your brain.

    In other words the time reversal would have to be highly localized otherwise there'd be no way at all physically to see it.

    And this is where I need help understanding this. To me, there doesn’t' appear to be any mystery here at all. There is no "arrow" to time. The only "arrow" that exists, exists as a very basic and, in my mind at least, obvious and expected limitation to what we can perceive given the nature of the human mind.

    So what's the hoopla about? Why is this even a question? It seems fairly obvious to me that I just don't get the argument. There's something here I'm missing. What is it?
  2. jcsd
  3. Jun 28, 2005 #2
    The entropy of this universe is always increasing.If you think that backward-running-time can be apparently moving forwards and defying the fact that time has only one direction arrow,whatever be the case , going backwards means we are decreasing entropy.Its like avoiding next Thursday.

  4. Jun 28, 2005 #3
    The arrow of memory is based in the arrow of time. Brain processes are irreversible ones. This is the reason of any damage of brain is irreversible.
  5. Jun 28, 2005 #4
    It's the inverse.
    Since we are all the time involved in macro-processes, we feel a physical principle working, that is the increasing of Enthropy, it is still a dramatically open problem, in a statistical approach it is demonstrated that the probability for a cup to turn the ordered kinetic energy of its centre of mass into the disordered kinetic energy of its moleculae is very high, there is no limit for this process.
    If you consider the inverse process, you'll find an amount of problems and limitation.
    On the other hand, in an analytical approach, you will find no reason to prefer one process to the other.

    That's why we feel time, at the speeds which we are used to, time is "separated" from space, Increasing of Enthropy is the sole reason for us to be sure that in our future there is Death and not Birth.
    Last edited: Jun 28, 2005
  6. Jun 28, 2005 #5
    Grrr. !@#Q#!@

    I'm not gettin thru here, which isn't your fault, it's mine, I'm just having difficulty getting this across.

    Forget entropy. This has nuthin at all to do with entropy, at all, that's a legitimate point, but a separate topic altogether.

    What I'm trying to get at is the idea that, if time WERE to run backwards, unless that time reversal was very strickly localized so that you weren't a part of it, there would simply be no way at all for you to precieve it.

    What I was trying to get across was the idea of what would happen, physically, inside yer noggin, as time ran backwards, and why, even though time WAS running backwards, your peception would still be of time running forward.

    Try re-reading what I'm talking about with the cards a few times, and maybe this will make a bit more sense. I can't think of another way of putting it, which, again, is my fault not yours.
  7. Jun 28, 2005 #6
    There can only be one thing,either time running forward or time running backwards. If the time had been running backwards since forever , we would have perceived it as running in one direction and would think the forwards is not possible.And if we think this same time is running forwards from the beginning, we would have been callow trying to agree that time is running backwards.

    Its all the way we see it and hold it in our brains , we have always seen a falling glass going down and breaking and never the opposite , so this is something stored inside us .Infact physical factors are also responsible , gravity will always take the glass downwards , so this is what has to happen in coming time and will happen unless someone catches it .We switch on the fan , and we see the fan blade starts rotating , because this had to happen , the electrons had to travel in one direction and provide the necessary energy to the fan. aND WHO DID IT ALL? ... It is our brain , we always wante dthat switching on the switch 'should' switch on the fan and we never wanted that 'fan should start moving' even when we do not tell it to.

    Everything is ordered.When you place a group of ordered events in line , it all depends on our brain if we start from left to right or vice-versa, but *strictly* our brain would 'always' stick to only one direction and would take it as 'forwards' ignoring the fact that 'backwards' could have been possible.

  8. Jun 28, 2005 #7
    Logic before all

    1) YOU are telling me that time has a favourite direction, you say: "backwards" just as if a "forwards" existed.

    2) You are trying to make hypothesis on human sensibility from physics, that is impossible by definition!!!!!
    For Physics come from human sensibility, and have no meaning without it.
  9. Jun 28, 2005 #8
    time could not be running forward nor backwards, it could just be there, like the other 3 dimensions... just that our counciusnes experience the "Present moment" but time as it is has not direction, it's like sayng we always move forward in the X direction.... Time is there and it doesn't move,,, is our brain/conciusnes wich work only at "one slice of time".

    I think... :confused:
  10. Jun 28, 2005 #9
    Ok! You know what a vector space is, don't you?

    Do not make confusion between Relativity and Entropy

    1) At our speeds, time is "separated" from space-dimensions, thus the vojage through time is a bit difficult to be done.

    2) If [tex]r(0)=r_{0}[/tex] then with a probability of 99,9999999% [tex]r(1)=r_{1}[/tex], then, if the map is injective, you can take the succession of the [tex]r_{i}[/tex] as a new basis for the space and make time the dependent variable to say it runs in one direction.
    Last edited: Jun 28, 2005
  11. Jun 29, 2005 #10
    Well this is definitely more of a philisophical issue.

    As stated, time is just another dimension with no true 'speed' or direction. Imagine if no 'conscious' beings existed in the universe to 'percieve' time's passing. How fast would things happen? Would time really exist? What direction would it go? Would it even matter? The universe itself, including matter and energy, would still exist though.

    Here is one theory: consciousness itself (in humans atleast), is created by brain processes, which are created by chemical reactions. When these interactions exist in one direction, we get consciousness, and the ability to percieve time and events. Its a feedback loop. It also exists in the other direction, but the reactions 'undo' themselves.

    So with this theory, does time exist for the dead or for those yet to be born? It would not. Nor would reality. However, the universe would still exist. Crazy stuff! :eek: But its only a theory.

    Time to go run around the block a few times to clear my mind...

  12. Jun 29, 2005 #11

    Your theory is interesting but really too "qualitative"
    You need to be more "quantitative".
  13. Jul 19, 2005 #12


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    Yes, and we have time because mass and energy DOES exist, which has nothing to do with consciousness perceiving time. The perception of time is only 'one part of the whole concept' of time itself.

    How do we define consciousness? A computer can process information as well as a human brain, but as far as we know it doesn't possess consciousness. A computer can also 'undo' information as well as 'do' information. Does that undoing of information constitute a reverse of time. Interesting thought.
    Hope you enjoyed the run. I think I need a good jog myself, possibly backwards to get back to where I was before.
  14. Jul 20, 2005 #13
    Think of it in terms of probabilities. This will answer your question I believe, but I am sure there are many other examples and answers which also prove hte passage of time.

    Let's say you shuffle the 4 cards and lay them down again.

    In the first instant you put down a king of hearts.
    In the second instant you put down a 5 of spades.
    In the third instant you put down a 2 of diamonds.

    You can now predict that you will put down a 9 of clubs and this is for certain.

    Let's say you put the card down and it happens to have a wax painting of the north face of the Eiger on it. What were the chances of this happenning?

    Now the other way round.

    You have 4 cards and you clearly see a king of hearts, a 5 of spades, a 2 of diamonds and a card with a wax painting of the north face of the Eiger on it. You lay them down. There is nothing unpredictable about that.


    I think a better example is gravity...

    You pick up a ball and drop it and it bounces on the floor and comes to a rest. This is the most likely set of events to occur.

    You then put the ball on the floor and wait with your hand above it, palms down. Suddenly some energy due to sound and heat coalesces inside the ball and where the ball contacts the floor and causes the ball to contract and bounce up slightly. Then more energy flows in, like ripples in water in reverse and the ball bounces higher and higher, every time the ball impacts the floor or flows through air, the air pressure above the ball increases pushing it down and sound coalesces just as the ball reaches the floor, giving it more kinetic energy until it bounces up to the palm of your hand. What were the chances of this happenning?

    Time can be played backwards, but each direction has different properties. In theory.
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