Time, Memory and Change: A Philosophical Exploration

[wespe]

I've been thinking.. If time is what a clock measures, at what rate does time pass? By definition, the same rate as the clock's hand moves, but that's just circular. Then, there's also "everything is stationary wrt itself", so how does any change occur at all? It just dawned on me that it is related to memory. That is, passage of time or any change can be perceived, because we can compare the current status to the previous one in our memory. If we didn't remember a moment ago, we wouldn't have a concept of time, or life or anything for that matter. So it seems that memory (anything that can store information) must be very important, I didn't realize this before. Does anyone have some thoughts on this, or know of a website where this line of thought is explored?

 

[loseyourname]

Everything is spatially stationary wrt itself. The same is not true of temporal movement. Unless frozen to absolute zero, there is always change of some sort and increasing entropy in closed systems. Time is the dimension through which this change (or movement, if you want to call it that) occurs.

 

[jcsd]

How do you define any unit is the problem here? The simple answer is you define it by defining it; if two clocks 'tick' at the same rate (ignoring SR for a minute) they are essenmtially measuring the same thing, just as if two metre rules are the same length they are measuring the same thing.

 

[wespe]

Everything is spatially stationary wrt itself. The same is not true of temporal movement.

I'm becoming confused. Everything is spatially stationary because "here is here", and temporally stationary because "now is now". Isn't experienced proper time different than movement in time dimension?

 

[AWolf]

How do you define any unit is the problem here? The simple answer is you define it by defining it; if two clocks 'tick' at the same rate (ignoring SR for a minute) they are essenmtially measuring the same thing, just as if two metre rules are the same length they are measuring the same thing.

Even though the two clocks produce the same result, they are not measuring the same thing.
Time is not an entity it is a perception directly related to an objects environment. Each clock is measuring its own time.

If you stretch your arms out horizontally, your finger tips would experience time faster than your head because your head is closer to the main mass of your body, and subsequently a larger gravitational force.
The difference would be infinitely small, but there would be a difference.

 

[jcsd]

I said to ignore relativty, but in that case we simply refine it so that the clocks are local and at rest to each other.

 

[AWolf]

I said to ignore relativty, but in that case we simply refine it so that the clocks are local and at rest to each other.

Okay, so the clocks consist of exactly the same quantity of mass, are both at rest to each other and both have exactly the same gravitational force exerted on them - you take relativity out of the equation.

The clocks are still not measuring the same thing.
The movement of the mechanics/electronics of each clock is syncronised, but that is all.

The measurement of time is directly related to the components of the clock. Not the cogs and springs, not even the atoms, but the energy that comprises all the subatomic particles.

Even if one of the clocks is running slow, is measurement would be inacturate, but the clock would still preceive time the same as the other, it just wouldn't display it the same.

 

[ram1024]

time = action

there's no other way to measure time except in the form of "something happening"

glad someone else besides me "gets" this, wespe :D

 

[jcsd]

Okay, so the clocks consist of exactly the same quantity of mass, are both at rest to each other and both have exactly the same gravitational force exerted on them - you take relativity out of the equation.

The clocks are still not measuring the same thing.
The movement of the mechanics/electronics of each clock is syncronised, but that is all.

The measurement of time is directly related to the components of the clock. Not the cogs and springs, not even the atoms, but the energy that comprises all the subatomic particles.

Even if one of the clocks is running slow, is measurement would be inacturate, but the clock would still preceive time the same as the other, it just wouldn't display it the same.

In that case they are essirtially measuring time on different scales, the only useful defintion of time is that which a 'clock measures'

 

[AWolf]

In that case they are essirtially measuring time on different scales, the only useful defintion of time is that which a 'clock measures'

That would imply that time is defined by the movement within a mechanical device.
Clocks provide you with a device that has a mechanical movement with a constant velocity. The amount of angular rotation of the cogs and hands at that velocity is how time is measured, but it is not a definition of time.

For a true definition of time you shouldn't ignore relativity, but rather use it.

A clock here on Earth measures time at a different rate to one aboard an orbiting satelite. Why ?
The easiest answer is Relativity, but that doesn't tell you very much.

A true definition of time must be constant both here and in orbit.

If we take the simplest particle, the photon, and assume for a moment that rather than traveling through empty space that is being transmitted through a granular space, then the transmission of photon energy from one grain to the next would give you the basic definition of time.
The more compressed the grains (gravity well) the longer it will take for the photon to travel a set distance, but each grain is still transmitting the energy at the same rate, there's just more grains to be traversed.
The more dispersed the grains get (a satelite on orbit) the shorter it will take the photon to travel - less grains - same transmission rate.

Since the photon is unsigned energy, whatever rules it has to adhere to, so too all the subatomic particles.

This would give you the most fundamental definition of time, its value would be the same anywhere in the Universe.

 

[jcsd]

A clock only measures it's proper time.

We know that there is no global defitnion of time as it would not be Lorentz invariant.

 

[wespe]

A clock only measures it's proper time.

This is what I meant in post #4. A clock doesn't measure movement in time dimension.

Jcsd, do you think the following statement is okay?
Everything is spatially stationary wrt itself because "here is here",
and temporally stationary wrt itself because "now is now"

Actually my emphasis in this thread was: if we didn't remember a momement ago, we couldn't compare it to now, and we wouldn't perceive a passage of time. More like philosophy than physics.

 

[geistkiesel]

I've been thinking.. If time is what a clock measures, at what rate does time pass? By definition, the same rate as the clock's hand moves, but that's just circular. Then, there's also "everything is stationary wrt itself", so how does any change occur at all? It just dawned on me that it is related to memory. That is, passage of time or any change can be perceived, because we can compare the current status to the previous one in our memory. If we didn't remember a moment ago, we wouldn't have a concept of time, or life or anything for that matter. So it seems that memory (anything that can store information) must be very important, I didn't realize this before. Does anyone have some thoughts on this, or know of a website where this line of thought is explored?

There are three basic states of time.

1. The Past.
2. The Future.
3. The Here and Now.

 

[wespe]

There are three basic states of time.

1. The Past.
2. The Future.
3. The Here and Now.

Am I supposed to extract anything useful out of that? What do you mean by "state of time"? If these are the basic ones, what are the more complex "states of time"? Why do you include "Here" with now?

 

[AWolf]

There are three basic states of time.

1. The Past.
2. The Future.
3. The Here and Now.

There is only one state of time and that is NOW

Everything else is a measurement of elapsed time.

• Past -> positive elapsed time

• Future -> Negative elapsed time

 

[Opethian]

I see a clock as being nothing more than a device which relates numbers to time in such a way as to make it easy for the general population to understand a difficult to explain phenomenon.

Clocks, and calenders too for that matter, are nothing more than number based systems which makes the average Joe's life easier and more productive. For example; if you had no idea what year you were born you could not possibly know how old you are. Thanks to the calender, average Joe knows he's 35 years old, or whatever the case may be.

Similarly we can use an egg timer to cook an egg for 7 minutes, but wtf is 7 minutes besides 7 full rotations of the second hand on the clock?

 

[Prometheus]

There is only one state of time and that is NOW

What do you mean by state of time. Perhaps that is where you lose me. What does this statement mean?

Everything else is a measurement of elapsed time.

You seem hung up on the word measurement. How Newtonian of you. Time is more than its measurement by mankind.

• Past -> positive elapsed time

• Future -> Negative elapsed time

I agree with geistkiesel. The most fundament awareness of time is the present. This is followed by the past and then the future. There are more complex states of time, but you seem not ready for them yet, as you seem hung up on measuring time.

The universe is not all at the same time. Time does not flow at constant speed, and no two entities move at the same rate through time. I have no idea what you mean by there is only one state of time, now. What do you mean?

You use the word elapsed. Elapsed is a verb expressed in the past tense. The past tense refers to time that has occurred in the past. Yet, you would speak of past time in the future, and use the word negative to do that. I challenge this. What do you mean?

 

[Prometheus]

If time is what a clock measures,

This is a Newtonain concept. In Einsteinian physics, time is much more than what a clock measures. Are you not aware of this? Are you not aware of space-time? I recommend that you investigate this.

 

[Antonio Lao]

... at what rate does time pass?

No physical theory can answer this question. Time flows uniformly even in the theory of relativity but there is a component of spacetime that can be curved as warping of time but this warpage of time is linked to the warpage of space. The two warpages cannot be separated into rate of time and rate of space.

...passage of time or any change can be perceived...

This is the time's arrow. And theoretically, there are four arrows. And nobody can answer these mysteries of one directional arrows.

1. Thermodynamics arrow - heat flows from hot to cool. The 2nd law. The increase of entropy.

2. Electromagnetic arrow - EM radiation always emanates outward from the source never inward.

3. Cosmology arrow - The expansion of the universe. The domination of redshifts over blueshifts.

4. Psychology arrow - We remember the past but not the future.

 

[wespe]

This is a Newtonain concept. In Einsteinian physics, time is much more than what a clock measures. Are you not aware of this? Are you not aware of space-time? I recommend that you investigate this.

well if my clock measures different values than your clock (they are identical, but due SR effects), then my time is different than your time, which means time is relative. that's what I understand from time is what clock measures.

I am aware of spacetime but in spacetime diagrams there's a formula like sqrt(dx^2-dt^2) to find the elapsed proper time, so you don't just use dt as elapsed time, so I don't know why the 4th dimension is labelled time.

Actually I don't know what I'm talking about so feel free to embarras me.

I was trying to relate passage of time with memory but no one was interested so let the thread die..

 

[Prometheus]

if my clock measures different values than your clock

Clocks measure clock time.

then my time is different than your time,

Your time is different from everyone else's time, always.

If you and I are unable to recognize that our time is different, then we can use an irrelevant third object, a clock, to define for us a shared, objective time. We can use the irrelevant clock time for its simplicity of undersanding and measuring.

This objective time is extremely useful. However, neither your time nor my time is dependant on the clock time. Each person's space passes through its time at its own rate. That is the nature of space-time.

Clocks are useful to give a context to relative times. However, as useful as clocks are, their use ignores the fact that objective time is approximate, and the lost information is the most important information.

 

[Prometheus]

Clocks, and calenders too for that matter, are nothing more than number based systems which makes the average Joe's life easier and more productive.

I disagree completely. Calendars track the solar and lunar cycles. Without calendars, how could society, and the people within it, maintain awareness of the cycles of the month and the year?

Without awareness of the cycles of the day, month, and year, our species would not have the level of consciousness, the level of science, or the level of religion that it has now.

 

[wespe]

Clocks measure clock time.

if "time is what a clock measures" then "clocks measure time" not "clocks measure clock time"

Your time is different from everyone else's time, always.

even if we are in the same inertial frame?

Clocks are useful to give a context to relative times. However, as useful as clocks are, their use ignores the fact that objective time is approximate, and the lost information is the most important information.

What is this lost information? Are we talking about Einstein's relativity or are you promoting a different theory?

 

[Prometheus]

"time is what a clock measures"

Do you subscribe to this? This is a pretty shallow understanding of time.

even if we are in the same inertial frame?

Yes

What is this lost information? Are we talking about Einstein's relativity or are you promoting a different theory?

If a clock is measuring time, then it must be involved in motion through space, as there is no other way for a clock to "measure" time. If a clock is in its own motion through space, doing whatever enables it to measure time, then it is involved in motion that other objects that are observing the clock are not. Since motion through space-time is dependent upon both motion through space and motion through time, and since there is a discrepancy in motion through space due to whatever motion through space it is that is enabling the clock to measure time, there must be a differential in motion through time between a clock and any object that observes it.

 

[wespe]

Do you subscribe to this? This is a pretty shallow understanding of time.

What is your exact definition of time?

If a clock is measuring time, then it must be involved in motion through space, as there is no other way for a clock to "measure" time. If a clock is in its own motion through space, doing whatever enables it to measure time, then it is involved in motion that other objects that are observing the clock are not.

ok let's think of a light clock: light continually bouncing back and forth between two parallel mirrors. If I am stationary wrt the mirrors, what would be the error in the measurement of this clock?

 

[Prometheus]

What is your exact definition of time?

I don't have an exact definition of time. However, the universe is composed of two fundamental entities, time and space. The Big Bang caused time and space to interact, in the form of space-time. All of time is bound up in space, and all of space is bound up in time, as space-time.

Clocks can measure time. However, such usage of time is quite limiting, as each unit of space, such as the observer of a clock, relates to his own time in a unique way. His space is bound up with his time, not with the clock's time.

To say that time is what a clock measures is to ignore the significance of space-time.

ok let's think of a light clock: light continually bouncing back and forth between two parallel mirrors. If I am stationary wrt the mirrors, what would be the error in the measurement of this clock?

You ask about the error in the measurement of the clock. I ask about the value of it.

As far as clocks are concerned, yours is an excellent example. Let us consider two observers, you and me. You body is in motion through space. Consider that chemical processes are going on within your body, metabolism, etc. My body is in motion through space, in the same way. They are not moving through space at the same rate of time. How is it relevant that we can use some objective third object to measure time? My rate of motion through time is different from your motion through time, as my body interacts with space in a manner different from yours. Using a light clock, or a mechanical clock, or watching the sun rise and set is very useful to create an objective time for us to share. However, how can you consider it completely applicable to either of us, let alone to both of us? Where is the effect of the interaction of space-time? If you are searching for a close approximation, as close as is possible given that you must use a clock, then I accept your example as close, forgiving the fact that you must use a clock.

If you use a clock as an objective way to relate your motion through space-time with mine, then you are ignoring the fact that each object has a unique relationship to space-time.

How can you compare two unique objects in space-time by relating them to a third, irrelevant object in space-time? What is the value of your comparsion. It does have value, I admit. Do you recognize its limitation?

 

[RAD4921]

The arrow of time

Time flies like an arrow. Fruit flies like an apple.

 

[jcsd]

Time is what a clock measures. It may be frame depedent, but so what? It doesn't mean that the clock is not measuring time.

 

[RAD4921]

What a clock measures

Clocks measure motion. A twelve hour clock measure half of the Earth's rotation on its axis in relation to the sun. Hour glasses measrue the movement of sand, quartz clocks keep arcurate time by measuring vibration of an electric current passing through a crystal. Atomic clocks measure the frequencies of the movement of atoms. Yearly calendars measure the movement of the Earth orbiting the sun. All measuring devices of "Time" (whatever that is) measures movement.

 

[jcsd]

Clocks measure motion. A twelve hour clock measure half of the Earth's rotation on its axis in relation to the sun. Hour glasses measrue the movement of sand, quartz clocks keep arcurate time by measuring vibration of an electric current passing through a crystal. Atomic clocks measure the frequencies of the movement of atoms. Yearly calendars measure the movement of the Earth orbiting the sun. All measuring devices of "Time" (whatever that is) measures movement.

what is motion? clearly it is depedent on time, e.g. v = dx/dt.

 

[Prometheus]

Time is what a clock measures. It may be frame depedent, but so what? It doesn't mean that the clock is not measuring time.

Doesn't it?

If a clock is in greater motion through space than another, then the time that it measures is slower. Clocks do not measure motion through time, they measure motion through space-time.

 

[Prometheus]

All measuring devices of "Time" (whatever that is) measures movement.

I agree with this statement. However, I do not agree with your examples.

All of your examples of motion are motion through space. You use time as a measure of motion through space. This is a Newtonian usage of time, and does not take into account motion through space-time.

 

[jcsd]

Doesn't it?

If a clock is in greater motion through space than another, then the time that it measures is slower. Clocks do not measure motion through time, they measure motion through space-time.

I'm not sure 'motion through spacetime' could be given a reasonable defintion. Personally if I had to give a defitnion tho' it would be the velocity 4-vector which is not analogus to time and always has a square norm of c^2 (so you could say that we move through spacetime at the same 'speed'). Also remember there is certainly no such thing as a 'greater motion' as all motion is relative as is time dialation.

So time is what a clock measures and what a clock measures is not Lorentz invariant, but that shouldn't be suprising as time isn't Lorentz invariant.

 

[jcsd]

Hmm I suppose you could say that the proper time of a clock between two events local to the clock relates to the 'length' of that clocks worldline between those two events.

 

[Prometheus]

IAlso remember there is certainly no such thing as a 'greater motion' as all motion is relative as is time dialation.

Huh?

There is greater motion through space and there is greater motion through time.

There is no such thing as greater motion through space-time, as there is only one rate of motion through space-time.

How can you say that there is no such thing as greater motion? or, what do you mean?

 

[jcsd]

Huh?

There is greater motion through space and there is greater motion through time.

There is no such thing as greater motion through space-time, as there is only one rate of motion through space-time.

How can you say that there is no such thing as greater motion? or, what do you mean?

What I mean is that 'motion' (i.e. velcotiy) is reative, so it is impossible to order it in such a manner that is frame invariant. i.e. in one frame my speed is greater than yours, but there must also exist another frame where my speed is less than yours. Think of the twin paradox and how both twins observe each others clocks to be slowed.

 

[Prometheus]

What I mean is that 'motion' (i.e. velcotiy) is reative, so it is impossible to order it in such a manner that is frame invariant.

I still do not understand what you mean by motion. Do you mean motion through space or motion through space-time?

If we race, and I run faster than you, am I or am I not in greater motion than you? I do not understand your perspective.

Think of the twin paradox and how both twins observe each others clocks to be slowed.

OK. Think of a clock, and two observers observing the clock. How can they relate themselves to each other on the basis of observing some clock?

 

[jcsd]

I still do not understand what you mean by motion. Do you mean motion through space or motion through space-time?

If an object is in motion it means that it changes it's postion as I said earlier it doesn't mean to much in terms of spacetime, so I mean motion through space (which in can be transformed away by choosing the apporpoiate refernce frames).

If we race, and I run faster than you, am I or am I not in greater motion than you? I do not understand your perspective.

No, because in your rest frame your speedis zero whilst mine is non-zero. This is a key point in relativity, whetehr it be Einsteinian or Galiliean

OK. Think of a clock, and two observers observing the clock. How can they relate themselves to each other on the basis of observing some clock?

Assuming all clocks are equal they could work out their relative velocities.

 

[wespe]

You ask about the error in the measurement of the clock. I ask about the value of it.

As far as clocks are concerned, yours is an excellent example. Let us consider two observers, you and me. You body is in motion through space. Consider that chemical processes are going on within your body, metabolism, etc. My body is in motion through space, in the same way. They are not moving through space at the same rate of time. How is it relevant that we can use some objective third object to measure time? My rate of motion through time is different from your motion through time, as my body interacts with space in a manner different from yours. Using a light clock, or a mechanical clock, or watching the sun rise and set is very useful to create an objective time for us to share. However, how can you consider it completely applicable to either of us, let alone to both of us? Where is the effect of the interaction of space-time? If you are searching for a close approximation, as close as is possible given that you must use a clock, then I accept your example as close, forgiving the fact that you must use a clock.

If you use a clock as an objective way to relate your motion through space-time with mine, then you are ignoring the fact that each object has a unique relationship to space-time.

How can you compare two unique objects in space-time by relating them to a third, irrelevant object in space-time? What is the value of your comparsion. It does have value, I admit. Do you recognize its limitation?

I see your point. However, I think the limitation applies to large objects. For example when I'm walking, my feet experience time a bit differently than my brain. But let's go to smaller scales. Say, we have two electrons stationary wrt each other. Can they not experience the same time, as measured by light clock? I don't know if an electron has smaller particles in it moving (or something). OK, what about a muon? Does its decay time depend on any movement inside itself? (not sure if that make sense, don't know really what I'm talking about)

 

[jcsd]

Yep, I think it's careful you shouldn't get confused the time-depedency of motion with motion actually being time itself.

 

[jcsd]

For example the unitary evolution of the wavefuction in the Schroedinger equation is time-depednet but actually assigning this time-depedncy to motion in the classical sense is something that you can't or will have great problems doing.

 

[Prometheus]

If an object is in motion it means that it changes it's postion as I said earlier it doesn't mean to much in terms of spacetime, so I mean motion through space

Are you saying that an object cannot be in motion through time. It seems that you deny that there is motion through time. How can you say that it doesn't mean much that there is motion through space-time? I think that this is a big point of disagreement between us.

No, because in your rest frame your speedis zero whilst mine is non-zero.

By this standard, no two objects or people can ever have the same frame, and so any measurement is meaningless.

Assuming all clocks are equal they could work out their relative velocities.

An impossible assumtption, in my opinion.



Do you consider that the speed of light is constant? If so, is it constant in space, in time, or in space-time?

 

[Prometheus]

Say, we have two electrons stationary wrt each other.

What is the duration of this stationary relationship? I think that this is not a valid or realistic assumption.

Can they not experience the same time, as measured by light clock?

What does time reflect in this case? They cannot experience the same time. However, as measured by a clock, they can be related, assuming that the value of the creatd relationship is what is important, and what is ignored is not valued.

 

[jcsd]

Are you saying that an object cannot be in motion through time. It seems that you deny that there is motion through time. How can you say that it doesn't mean much that there is motion through space-time? I think that this is a big point of disagreement between us.

what is motion through time tho'? dt/dt? (though the time component of the velcoity 4-vector can be thought of as dt/dT mutplied by c and relatvistic gamma where T is the proper time)

By this standard, no two objects or people can ever have the same frame, and so any measurement is meaningless.

This is relativity, two objects share the same rest frame if they are at rest to each other if they're not they have different rest fra,es; it's simple as that. Spacetime wouldn't be so useful if this wasn't the case.

An impossible assumtption, in my opinion.

Not really, clocks that measure the time perfectly are not disallowed in this model.

Do you consider that the speed of light is constant? If so, is it constant in space, in time, or in space-time?

The speed of light is the same in all inertial frames this is a postulate of relativity.