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Sin Jeong-hun

Basic understanding of time

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I disagree. I think it's getting too worked up about an analogy, and angry because someone is trying to understand a concept in a different way than you understand it. It's not meant to be taken literally. If someone is taking the analogy too far (e.g. thinking that time is made up of water molecules) then by all means take them to task for it, but the true test is whether you can do something correct with your understanding. So if "time flows" is useful for someone to understand something and they reliably come to the right conclusion when they apply it.

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Your challenge, I think, is to reconcile how time behaves objectively, as a physicist measures it and how you, as a psychologist, understand it relying more on human experiential and physiological data .

 

Well, yes, but don't misunderstand me - I'm not naively thinking that objective measures of time should map directly to subjective temporal perception. Even psychologists talk about "veridical" time as opposed to "subjective" time. I do think that we need to be aware that objective models of time arise from minds, and that our ideas about causality, for instance are rooted in the way we make sense of the world - in our intuitive models.

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I disagree. (And I am not alone, see below)

 

 

Fine, I didn't actually say I agreed or otherwise.

 

That quote was from the contibution to the book by one time particle physicist John Polkinghorne KBE, the quote started his analysis of the flow statement, in relation to the block universe (which I also linked to) which mirrors that here between Lizzie L and the hard physicists here.

 

Pretty well all aspects and all theories of the subject as discussed in this book by the range of experts indicated, including the originator of the light cone.

The other quote was from the objectives of the book.

 

It was all supplied in the spirit of adding informatuion for those who might wish to follow it up.

 

:)

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Definitely a different beast. Which is why I've been arguing that we operationally define time, for scientific purposes, in terms of clocks. There doesn't seem to be a more fundamental definition than that.

 

Rather we quantify time based on oscillations because it is convenient. Another, perfectly valid oscillationless and far more fundamental definition of a unit of time is that of the planck time; the amount of time required for light to travel a planck length. We can use that as the unit length on a time ruler.

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Isn't the planck length defined in terms of the speed of light?

 

Yes it's [math] \sqrt{\frac{\hbar G}{c^3}}[/math]

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In that case this definition:

 

Rather we quantify time based on oscillations because it is convenient. Another, perfectly valid oscillationless and far more fundamental definition of a unit of time is that of the planck time; the amount of time required for light to travel a planck length. We can use that as the unit length on a time ruler.

 

is circular.

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Isn't the planck length defined in terms of the speed of light?

 

I think all Planck units have c somewhere in the derivation. The most basic of the five equations with five universal constants is that

[latex]

l_P =ct_P

[/latex]

In that case this definition:

 

is circular.

 

Yes - that's kind of the point. Everything both defines the other units and is in turn defined by them - they hang together as a self-referential, self-consistent, and self-contained set. That's why they are so neat.

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Yes - that's kind of the point. Everything both defines the other units and is in turn defined by them - they hang together as a self-referential, self-consistent, and self-contained set. That's why they are so neat.

 

It's also expected. It's why some units have to just be defined, rather than derived.

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It's also expected. It's why some units have to just be defined, rather than derived.

 

Is there anything you cannot get a planck unit of without further arbitrary definition (ie based on just h_bar, c, G, k_B, and 4.pi.epsilon_0). Luminoous Intensity ie like SI Candela?

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Is there anything you cannot get a planck unit of without further arbitrary definition (ie based on just h_bar, c, G, k_B, and 4.pi.epsilon_0). Luminoous Intensity ie like SI Candela?

 

Candela and mole, I think, are the SI base units not represented.

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It's also expected. It's why some units have to just be defined, rather than derived.

 

I don't have a problem with that.

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New here. Wow, 287 posts on this topic. Confession: I read the first 5 pages and the last page. I hope I do not repeat what others have posted.

 

I believe that what is usually called time is an artifact of memory. I think that saying this is not equal to saying that it is an illusion. Several posters connect time with change. Recognition of change requires memory, or another accepted record in place of one's own memory. I see the "passage of time" as recognition of change, but the "passage of time" is not the same as "time".

 

Einstein is quoted as saying that "time is what we see when we look at the face of a clock". I accept that he was correct. The face of a clock provides us with the state of an object (two objects if you prefer, the hands) relative to the state of another object, the face. What we see at any moment is just the face and the hands. In order to infer the passage of time, we must have some memory of what we saw at another moment. Additionally, we must have some confidence that we can tell which of the two observations was taken first. (Two photos of a clock showing different positions of the hands requires assumptions to infer any passage of time). Our experience tells us that the two observations cannot have been taken concurrently. (Two objects, the two sets of hands - one set in each photo - cannot have the same state).

 

So, what we see when we look at a clock is the state of the clock. Einstein said the state of the clock is time. Now, all objects have only one state, their current one. Objects do not have a past state or a future state. The current state of all objects is only "now", and thus time has only one state, the "now". I acept that we don't actually experience anything independent of the observed objects which we could call time. We only experience the objects. I conclude that time (not the passage of time) is the aggregate experience of a particular state, per Einstein: our experience of the face and the hands of the clock.

 

To be a bit more clear, I conclude that there is no phenomenon which we can call time. The term "time" is a shorthand way of describing our recognition of a particular state of existence.

 

Way too many words. Wrote this on-line. I hope it is not too disjointed.

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New here. Wow, 287 posts on this topic. Confession: I read the first 5 pages and the last page. I hope I do not repeat what others have posted.

 

I believe that what is usually called time is an artifact of memory. I think that saying this is not equal to saying that it is an illusion. Several posters connect time with change. Recognition of change requires memory, or another accepted record in place of one's own memory. I see the "passage of time" as recognition of change, but the "passage of time" is not the same as "time".

 

Einstein is quoted as saying that "time is what we see when we look at the face of a clock". I accept that he was correct. The face of a clock provides us with the state of an object (two objects if you prefer, the hands) relative to the state of another object, the face. What we see at any moment is just the face and the hands. In order to infer the passage of time, we must have some memory of what we saw at another moment. Additionally, we must have some confidence that we can tell which of the two observations was taken first. (Two photos of a clock showing different positions of the hands requires assumptions to infer any passage of time). Our experience tells us that the two observations cannot have been taken concurrently. (Two objects, the two sets of hands - one set in each photo - cannot have the same state).

 

So, what we see when we look at a clock is the state of the clock. Einstein said the state of the clock is time. Now, all objects have only one state, their current one. Objects do not have a past state or a future state. The current state of all objects is only "now", and thus time has only one state, the "now". I acept that we don't actually experience anything independent of the observed objects which we could call time. We only experience the objects. I conclude that time (not the passage of time) is the aggregate experience of a particular state, per Einstein: our experience of the face and the hands of the clock.

 

To be a bit more clear, I conclude that there is no phenomenon which we can call time. The term "time" is a shorthand way of describing our recognition of a particular state of existence.

 

Way too many words. Wrote this on-line. I hope it is not too disjointed.

I disagree.

 

Time is evrywhere in physics. Almost all equations include somewhere this little "t".

to me, time is a very real phenomenon. The problem is that we are embedded in time (and space), so we have to analyze from the inside, which is extremely difficult.

 

If you take a step back and think very deeply not about time anymore, but about space, you may find out that space is equally mysterious with time, although more easily 'touchable".

IMHO we (I mean the human beings) haven't grasp what it's all about, yet.

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One thing I know for sure is that you cannot think of time as of something that doesn't quantize, so there is some limit to the smallest amount of time we can have. if we have two runners one 1 m away from another, where the lagger runs twice as fast, we can make an argument that while the lagger gets to where the leader is, the leader will move a half meter, then by the same algorithm by 1/4 meter, etc. and according to such an argument the lagger will never catch the leader because he will always be (1/2)^n meters behind. we know what that series converges to, and we know that after the leader runs for approximately 1 m the lagger will catch up to him, but if time was indeed forever divisible it would never happen.

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One thing I know for sure is that you cannot think of time as of something that doesn't quantize, so there is some limit to the smallest amount of time we can have. if we have two runners one 1 m away from another, where the lagger runs twice as fast, we can make an argument that while the lagger gets to where the leader is, the leader will move a half meter, then by the same algorithm by 1/4 meter, etc. and according to such an argument the lagger will never catch the leader because he will always be (1/2)^n meters behind. we know what that series converges to, and we know that after the leader runs for approximately 1 m the lagger will catch up to him, but if time was indeed forever divisible it would never happen.

 

That does not follow from your explanation. There is no quantized unit or smallest length of time if you are solving this problem. You have a finite duration and an infinite number of intervals, which is inconsistent with a minimum length of time.

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That does not follow from your explanation. There is no quantized unit or smallest length of time if you are solving this problem. You have a finite duration and an infinite number of intervals, which is inconsistent with a minimum length of time.

Perhaps I did not make myself clear. Hmm. Ok. If you were able to divide time indefinitely you can look at the problem as an infinite sum of infinitely small quantities, that get smaller and smaller, and tend to 0. I think it is effectively a rhetoric of how you define limits, and you're right that in the case of such a series I suggested there is no ambiguity. Thank you for correcting me.

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I haven't read the whole thread, but it's fascinating to see people so fascinated by time. I give my opinion. Time is the various sequences of movement, is not a poetic dimension, but even Einstein I suppose was aware of this, even when he was talking about time or spacetime.

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I visualize time as a kind of virtual 4th dimension.

In Hinduism Shiva is said to have had a third eye that was endowed with extra-sensory perception.

Time exists as long as a "third-eye" is there to observe it.

Recall that there is no such thing as absolute time.

Time is observer dependent and without one, time ceases to exists (or could be visualized to be decoupled from space time) to leave space which is temporal and perceptible regardless of the observer.

I visualize time as "quantum time" !!!

Time is what the observer sees depending on what he wants to see, (frame of reference dependent).

Time both does and does not exist.

It exists when a observer conceptualizes it related to his frame of reference but in essence it actually does not exist !!! :wacko:

Edited by petrushka.googol

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It is also very peculiar, that although according to Einstein's space time continuum and the whole concept of a four space, time behaves very different from position. You can always move an object to a negative direction in terms of position, but with time, although theoretically you can make calculations and predictions about what happened before right now, you can never go back to that particular moment.

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It is also very peculiar, that although according to Einstein's space time continuum and the whole concept of a four space, time behaves very different from position. You can always move an object to a negative direction in terms of position, but with time, although theoretically you can make calculations and predictions about what happened before right now, you can never go back to that particular moment.

I think it is a wrong interpretation. Negative direction is simply a rotation 180 degrees, it is not exactly a negative.

Truly negative space would be negative distance and we know that negative distance does not exist.

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It is also very peculiar, that although according to Einstein's space time continuum and the whole concept of a four space, time behaves very different from position. You can always move an object to a negative direction in terms of position, but with time, although theoretically you can make calculations and predictions about what happened before right now, you can never go back to that particular moment.

 

My thoughts on this :

As I have said before time is relative to the observer and our choice of reference axes are purely arbitrary. If we consider the direction of increasing entropy to be negative (correlated with state of greater disorder) then the big bang becomes our origin and we could assume that time actually is moving backwards with respect to it. (negative is correlated with increased magnitude of entropy). Hence we could assume that we are actually moving back in time. It is purely subjective. Back to the future anyone ? :P

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I think it is a wrong interpretation. Negative direction is simply a rotation 180 degrees, it is not exactly a negative.

Truly negative space would be negative distance and we know that negative distance does not exist.

 

Then what it means is you can't rotate 180º on the time axis.

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I think it is a wrong interpretation. Negative direction is simply a rotation 180 degrees, it is not exactly a negative.

Truly negative space would be negative distance and we know that negative distance does not exist.

 

I don't think that's a good way to look at it. We can always define an origin at some point in space, and in time. No matter where it is, we can always plot a position and time of a certain event that occured. Suppose that event occured right now. Any other event that we observe will be observed with a positive time separation from this current event. However in terms of space the location could vary in either positive or negative (or be the same) as the current event. Therefore it's not that you are defining negative distance, it is a negative position, which is compared to a certain origin which is completely possible, however it's not possible in terms of time. What petrushka.gogol said before makes sense, however us as living beings see, and consider direction of increasing entropy to be positive, and you can make an argument that it's the same as saying that for us time is always running in the positive direction. It would be really cool to do the whole back to the future thing though :)

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I don't think that's a good way to look at it. We can always define an origin at some point in space, and in time. No matter where it is, we can always plot a position and time of a certain event that occured. Suppose that event occured right now. Any other event that we observe will be observed with a positive time separation from this current event. However in terms of space the location could vary in either positive or negative (or be the same) as the current event. Therefore it's not that you are defining negative distance, it is a negative position, which is compared to a certain origin which is completely possible, however it's not possible in terms of time. What petrushka.gogol said before makes sense, however us as living beings see, and consider direction of increasing entropy to be positive, and you can make an argument that it's the same as saying that for us time is always running in the positive direction. It would be really cool to do the whole back to the future thing though :)

:P ....

Edited by petrushka.googol

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