The direction of time

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Reply Tue 28 Apr, 2009 12:48 pm
I tend to think of time as flowing in one direction. But it could flow in the exact opposite direction, throughout the entire universe, and still make sense physically. So the way I like to make the distinction, the way to tell which direction time is flowing, is to observe the tendency of events towards entropy or order. Our universe tends towards entropy.

As humans, we have found that most order is achieved through effort, work, and often great amounts of time, and that structures of order are susceptible to destruction. Things fall apart over much smaller time spans than took to build them, in general. This tells me that time flows in the direction in which events tend towards entropy.

If time flowed backward, it would make sense to me that things would take effort, work, and often great amounts of time to fall apart, and structures falling apart would be susceptible to come together (tend toward order).

If anyone knows more about this topic than I do (which is probably a lot of people here), please tell me if this makes sense!
 
Justin
 
Reply Fri 8 May, 2009 06:07 am
@loudthoughts,
I'm bumping this thread for you as it was in the moderation que.
 
rhinogrey
 
Reply Mon 11 May, 2009 07:52 pm
@loudthoughts,
The biggest blunder the early mystics made was in confusing the end for the beginning--in mixing up where we are going with where we've come from.
 
No0ne
 
Reply Mon 11 May, 2009 07:54 pm
@loudthoughts,
loudthoughts wrote:
I tend to think of time as flowing in one direction. But it could flow in the exact opposite direction, throughout the entire universe, and still make sense physically. So the way I like to make the distinction, the way to tell which direction time is flowing, is to observe the tendency of events towards entropy or order. Our universe tends towards entropy.

As humans, we have found that most order is achieved through effort, work, and often great amounts of time, and that structures of order are susceptible to destruction. Things fall apart over much smaller time spans than took to build them, in general. This tells me that time flows in the direction in which events tend towards entropy.

If time flowed backward, it would make sense to me that things would take effort, work, and often great amounts of time to fall apart, and structures falling apart would be susceptible to come together (tend toward order).

If anyone knows more about this topic than I do (which is probably a lot of people here), please tell me if this makes sense!


To go back one must go forward, or one would forget one went back.
No one would remember if they went back without moving forward.
 
Yogi DMT
 
Reply Mon 11 May, 2009 08:12 pm
@loudthoughts,
I've always thought about this and realized time is a constant not a variable. I tend to really differ from common thoughts on this subject. There is no slowing down time, nor speeding it up, nor stopping it, nor making it go backwards. I think we really over analyze and over think time and make it it out to be a measurement, more than just an idea. To me, time just is how it is and cannot change. The closest we will ever be to going back in time is recreation. Time just keeps on going and, at least for me, that's all there is to it. If for some reason things happen slower or faster, even in mass effect there will be another logical yet extremely coincidental reason for the occurance but it always happen in an alotted amount of time. Space on the other hand is a different thing, but my position on time, is that it is over-analyzed and discussion making it more than it is. My definition of time is as follows: the constant periodical and countinous flow of anything, everything, and nothing if happens to be.
 
GoshisDead
 
Reply Mon 11 May, 2009 08:16 pm
@No0ne,
How could time have a direction that we don't give it? The time it takes to get from point a to point B the direction is determined by space. When we measure time with a clock the direction is determined by durative experience and the cycle of days and seasons. neither the future or the past physically exists so tracking them with 'time' one can only really track one moment of present at any given point. Direction and time are only experiential correlates of our experience with the functions of the universe.
 
Astovio
 
Reply Sun 17 May, 2009 09:20 pm
@loudthoughts,
I personally am interested in the M-theory idea of time. Just as the 3d world is the composition of infinite 2d structures (for lack of a better word), the 4d world, supposedly time, consists of infinity 3d structures. The idea being that time is an entity (again for lack of a better word... i'm tired ok lol) that is composed of the present, the past, and the future, all as one entity. We, being in the lower dimension, can only experience it one 3d structure at a time, and it appears to be linear to us.

I did a horrible job explaining that... I doesn't help that I've never actually studied M-theory, I've just seen a couple youtube videos, but they make sense. Maybe someone else can help me out lol
 
CarolA
 
Reply Sun 17 May, 2009 10:53 pm
@Astovio,
I tend to think that it doesn't "flow" anywhere, it all happens exactly at this instant, then the rest is just memory or traces of events that happened prior to just now. So there is no actual "future", but of course we can predict "future". If I throw a stone at you, its path is predictable and you know to duck.
Another idea to play with!
 
Bones-O
 
Reply Mon 18 May, 2009 06:47 am
@loudthoughts,
Many fundamental processes are time-symmetric: they work the same forwards as backwards. Of those that don't, we have no reason to say that one process describes the event more than its inverse. Since we do perceive a direction in time, we simply take all processes to time-evolve with respect to this direction. As such, the thermodynamical time-arrow (that things tend toward maximum entropy) is our natural reference axis for time. We have som ejustification for this insofar as we have an origin for time, but no upper limit. However it is possible this justification itself only arises because of how we think of time.

There's an interesting example in the big bang black holes. Because the universal time-arrow points in the same direction as the themodynamic (the justification for our view of time), the entropy of the big bang was necessarily minimum (it began from no occupiable states, and so zero entropy). In black holes, the prediction was initially that the entropy of matter falling in is lost: the black hole is a zero-entropy system. Because this violates thermodynamics, the black hole was postulated as a maximum entropy system so that overall entropy is not lost. But we know that the spacetime metric of a black hole is the reverse of that of the big bang: it makes sense then that entropy in a black hole tends toward zero just as entropy in an expanding universe tends away from zero. Further, there should be no degeneracy in a singularity, so a maximum-entropy black hole makes as much sense as a maximum-entropy big bang, i.e. none. I can't shake the feeling that maximum entropy black holes are a by-product of imposing our view of time on the universe.
 
Lost phil
 
Reply Mon 18 May, 2009 09:13 pm
@Bones-O,
I do not believe time exists. I believe time, like many other human inventions, was and continues to be this ficticious realm we can base our existence on. Change, is a better term. Time implies a begining and an end. Time is great for knowing when i have to getup for work in the morning. But the concept of time is not necessary for me to exist and i do not understand why we as a species place so much importance on a ficticious notion we devised ourselves.
 
JeffD2
 
Reply Sun 24 May, 2009 01:48 pm
@loudthoughts,
loudthoughts wrote:
I tend to think of time as flowing in one direction. But it could flow in the exact opposite direction, throughout the entire universe, and still make sense physically. So the way I like to make the distinction, the way to tell which direction time is flowing, is to observe the tendency of events towards entropy or order. Our universe tends towards entropy.

As humans, we have found that most order is achieved through effort, work, and often great amounts of time, and that structures of order are susceptible to destruction. Things fall apart over much smaller time spans than took to build them, in general. This tells me that time flows in the direction in which events tend towards entropy.

If time flowed backward, it would make sense to me that things would take effort, work, and often great amounts of time to fall apart, and structures falling apart would be susceptible to come together (tend toward order).

If anyone knows more about this topic than I do (which is probably a lot of people here), please tell me if this makes sense!





Time appears to move forward 100 percent. This is because at any given moment in time, we possess memories of previous moments in time, and lack memories of any following moments in time. We can never be certain whether time is moving forwards or backward.
Let [x,y] be a closed interval of time where x and y are distinct point in time. Assume by contradiction that when at y, time moves backwards to x, and when at x, we know that time began to move backwards at y. If we know that time began to move backwards at y when we are at x, then we know the future. Therefore, we know the future. It is impossible to know the future. Therefore, if time moves backwards from y to x, we cannot know.


I'm not saying this is the correct answer. This is just my view on the situation. Correct me if I'm wrong.

Also, how does entropy and the 2nd law of thermodynamics fit into all of this? I don't get it.
 
Bones-O
 
Reply Sun 24 May, 2009 02:09 pm
@loudthoughts,
The 2nd law of thermodynamics has its own arrow of time. Entropy always increases in the Universe. Even if I build a highly ordered system, the disorder I create in doing so outside that system outweighs the order I create. Booklearnin' for instance: the heat my brain gives off adds to the disorder of the Universe much more than the ordering of neurons in my brain subtracts.

The relationship between the thermodynamical arrow of time and the others (cosmological and psychological) is interesting. The cosmological arrow of time is in the direction of Universal expansion. As the universe expands, the number of possible configurations of matter within the universe necessarily increases. Entropy is simply a count of this number of configurations, so there is some link there.

A firmer link lies between thermodynamic and psychological time. Building memories, that is storing information about events, necessarily lowers the entropy of the brain and increases the entropy of the Universe as a whole. The reverse is something we'd probably have no control over: reducing entropy would likely yield information spontaneously rather than practically. So the psychological arrow of time is probably built on the thermodynamic one.
 
JeffD2
 
Reply Sun 24 May, 2009 05:03 pm
@Bones-O,
Bones-O! wrote:
The 2nd law of thermodynamics has its own arrow of time. Entropy always increases in the Universe. Even if I build a highly ordered system, the disorder I create in doing so outside that system outweighs the order I create. Booklearnin' for instance: the heat my brain gives off adds to the disorder of the Universe much more than the ordering of neurons in my brain subtracts.

The relationship between the thermodynamical arrow of time and the others (cosmological and psychological) is interesting. The cosmological arrow of time is in the direction of Universal expansion. As the universe expands, the number of possible configurations of matter within the universe necessarily increases. Entropy is simply a count of this number of configurations, so there is some link there.

A firmer link lies between thermodynamic and psychological time. Building memories, that is storing information about events, necessarily lowers the entropy of the brain and increases the entropy of the Universe as a whole. The reverse is something we'd probably have no control over: reducing entropy would likely yield information spontaneously rather than practically. So the psychological arrow of time is probably built on the thermodynamic one.




Thanks Bones-O, that makes sense.

I dont see why entropy would force time to move forward. In fact, I don't know of any physical law that forces time to move forward.

The way I see it, if time moves forward, then entropy increases. Also, if time moves backward, then entropy decreases.

Time doesnt appear to move backward though simply because at any given moment in time, we possess memories of previous moments in time, and lack memories of any following moments in time (Like I said before).

Overall, I believe that it is impossible to know the direction that time is flowing at any given moment in time.

Of course, the only way any of this can be true is if we assume that time exists in the first place.
 
Bones-O
 
Reply Sun 24 May, 2009 05:39 pm
@JeffD2,
JeffD2 wrote:

The way I see it, if time moves forward, then entropy increases. Also, if time moves backward, then entropy decreases.


But there's no difference between those two descriptions. You're describing the same timeline. Us saying it moves forward is with respect to our psychological time - that's arbitrary, we could say time is moving backward with entropy decreasing in a contracting universe, but since none of us perceive it that way it's not useful communicatively.

JeffD2 wrote:

Overall, I believe that it is impossible to know the direction that time is flowing at any given moment in time.


It's more precise to speak of antisymmetries than flow or direction. The universe is always more expanded in the future and more contracted in the past - that's one asymmetry. The entropy of the universe is always greater in the future and lesser in the past than it is now - that's another. I remember the past but not the future - that's a third.
 
 

 
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