Timekeeping (split from THE TIME-FLOW FALLACY)

[geordief]

Is there any sense in the question "Can one clock measure  another  (less accurate) clock?"

Does the latter clock become simply  a set  or series of events when it becomes thus  the "measured " ?

 

Edited January 31, 2019 by geordief

[swansont]

  On 1/31/2019 at 12:13 AM, geordief said:

Is there any sense in the question "Can one clock measure  another  (less accurate) clock?"

Does the latter clock become simply  a set  or series of events when it becomes thus  the "measured " ?

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Yes, sort of.

If you have identical clocks and don’t know which one is the good clock, all you can say is the one runs fast or slow relative to the other. (As the saying goes, a man with one clock knows what time it is. A man with two clocks is never sure). But if you know one clock is better (some types of clocks are inherently noisier) then you can make an estimate of how much of the difference is due to each clock.

With more than two clocks, you can do a series of pair-wise comparisons and get an idea of which clocks are good, and which aren’t.

[geordief]

Is it correct to say that any timekeeping device is an object moving in spacetime or does that description not apply to devices that keep time  using processes such as radioactive decay ?

Also it it reasonable to say that all timekeepers will inevitably  be inaccurate  to one degree or another?

Could it be conceivable that a perfect method could ever  be found?

[Mordred]

All objects are essentially part of spacetime this includes timekeeping devices. Or any other process such as particle decay. A timekeeping device can be any device with regular intervals of some measurable change in state.

 All devices will always have a certain degree of inaccuracy, regardless of how perfect. The Heisenberg uncertainty would also apply in this regard. So no measurements under a spacetime geometry can ever be perfect. Though without quantum effects one can get incredibly accurate. (often times good enough is just that lol) 

Edited January 31, 2019 by Mordred

[studiot]

 

  On 1/31/2019 at 4:28 AM, geordief said:

Is it correct to say that any timekeeping device is an object moving in spacetime or does that description not apply to devices that keep time  using processes such as radioactive decay ?

Also it it reasonable to say that all timekeepers will inevitably  be inaccurate  to one degree or another?

Could it be conceivable that a perfect method could ever  be found?

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  On 1/31/2019 at 5:02 AM, Mordred said:

A timekeeping device can be any device with regular intervals of some measurable change in state.

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Mordred has already told you in theoriginal thread that

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Mordred

Another common misconception is thinking time controls rate of change

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It is also a common fallacy to think that motion controls time.

They are linked but separate.

Don't forget that motion is relative and that regularity is different for atoms in the Sun and on Earth and the motion of the Sun and Alpha Centauri are different and we say that in the perturbation or change of this regularity.

It is also wrong  to think that this regularity is simple and discrete, like the 'ticking of a clock'.

Time can be measured by a device using a process that is regualr on average, eg radioactivity.
Nor need the regularity be linear (that is each tick is the same).
Each extractable 'tick' of a capacitor discharge clock follows a decreasing exponential, as does a radioactivity based averaging clock.

[swansont]

  On 1/31/2019 at 4:28 AM, geordief said:

Is it correct to say that any timekeeping device is an object moving in spacetime or does that description not apply to devices that keep time  using processes such as radioactive decay ?

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All objects are moving through spacetime, at c. If you are moving, lengths contract, but time slows (in the spacetime interval, and thus the 4-velocity, ct has the opposite sign as x, y and z, so these compensate for each other)

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Also it it reasonable to say that all timekeepers will inevitably  be inaccurate  to one degree or another?

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Yes. There is always noise in the frequency of an oscillator, and time )phase_ is the integral of frequency. The best you can hope for is white frequency noise, and the integral of that is a random walk. Thus, two identical clocks will random walk away from each other. IOW, clocks will never stay synchronized. (This is known in my field as "job security")

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Could it be conceivable that a perfect method could ever  be found?

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No. Noise is present in all physical systems. All you can do is try and make it smaller.

[geordief]

  On 1/31/2019 at 8:47 AM, studiot said:

 

It is also a common fallacy to think that motion controls time.

They are linked but separate.

 

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Yes I held that opinion for a long time  but no longer.

I also understand that time is a property of a system (not a "thing" in itself) but am starting to wonder whether it may be the accelerations  in the system which are the salient feature that  timing devices show up.(perhaps as an aside acceleration is linked to time dilation just as much as relative motion)

[studiot]

  On 1/31/2019 at 12:04 PM, geordief said:

but am starting to wonder whether it may be the accelerations  in the system which are the salient feature that  timing devices show up

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NO.

You can use the pattern changes in the B-Z chemical reaction as a timing device.

What does this have to do with acceleration?

[geordief]

  On 1/31/2019 at 12:13 PM, studiot said:

NO.

You can use the pattern changes in the B-Z chemical reaction as a timing device.

What does this have to do with acceleration?

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Each change in the system (each tick) is accompanied** by an acceleration isn't it?

 

All relative motion started with an acceleration at source

 

Don't all changes in any physical system require an acceleration  to get things moving?

 

I had a quick look at your example--it requires an initial acceleration to set it up,doesn't it and subsequent oscillations would be derived from that.

 

(hope I am not being obtuse)

 

** well from your example "accompanied" is  wildly overstating it  but still is there an association at the outset?

[Mordred]

  On 1/31/2019 at 12:29 PM, geordief said:

Each change in the system (each tick) is accompanied** by an acceleration isn't it?

All relative motion started with an acceleration at source

Don't all changes in any physical system require an acceleration  to get things moving?

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A change in inertia requires acceleration, however objects undergo motion without acceleration being involved. So they are changing coordinates from one location to another. It isn't a reason for time dilation in and of itself, though it does have consequences (rotations of the Lorentz transformations under SR) (rapidity). Each tick of a mechanical clock may require acceleration to occur but this does not relate to the average rate of time  in a given locale. 

 

[swansont]

  On 1/31/2019 at 12:04 PM, geordief said:

Yes I held that opinion for a long time  but no longer.

I also understand that time is a property of a system (not a "thing" in itself) but am starting to wonder whether it may be the accelerations  in the system which are the salient feature that  timing devices show up.

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No, I don’t think so. One kind of clock is an ion held in a trap, as close to motionless as possible. Acceleration is not really a feature of the device.

  3 hours ago, geordief said:

(perhaps as an aside acceleration is linked to time dilation just as much as relative motion)

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You can’t equate the two. The time dilation is a function of velocity, which does not tell you what the acceleration is, and it can be zero.

[geordief]

  On 1/31/2019 at 3:16 PM, swansont said:

No, I don’t think so. One kind of clock is an ion held in a trap, as close to motionless as possible. Acceleration is not really a feature of the device.

You can’t equate the two. The time dilation is a function of velocity, which does not tell you what the acceleration is, and it can be zero.

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When time dilation occurs as a result acceleration  is it really caused by the relative motion produced by the acceleration?

 

Or can we have time dilation  caused by acceleration when objects  are stationary wrt each other? (if such a scenario exists :I have a vague idea it might)

  On 1/31/2019 at 1:06 PM, Mordred said:

A change in inertia requires acceleration, however objects undergo motion without acceleration being involved. So they are changing coordinates from one location to another. It isn't a reason for time dilation in and of itself, though it does have consequences (rotations of the Lorentz transformations under SR) (rapidity). Each tick of a mechanical clock may require acceleration to occur but this does not relate to the average rate of time  in a given locale

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There was an initial acceleration  going back to the BB. Is that being played out ever since?

 

When you say "the average rate of time  in a given locale" do you mean as measured from another frame of reference?

You are not referring to proper time in different locales,do you?

 

I am not quite clear what the "ii" I have bolded in your quote refers to....acceleration? "changing co-ordinates" ? motion?   -I think you are saying "acceleration is not a reason  for time dilation in and of itself"

Edited January 31, 2019 by geordief

[swansont]

  On 1/31/2019 at 3:55 PM, geordief said:

When time dilation occurs as a result acceleration  is it really caused by the relative motion produced by the acceleration?

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Yes. Acceleration does not appear in the SR time dilation formula

  1 hour ago, geordief said:

Or can we have time dilation  caused by acceleration when objects  are stationary wrt each other? (if such a scenario exists :I have a vague idea it might)

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You would need to describe this scenario. 

[geordief]

  On 1/31/2019 at 5:00 PM, swansont said:

Yes. Acceleration does not appear in the SR time dilation formula

You would need to describe this scenario. 

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Well what about if 2 massive  objects are prevented from approaching one another(=accelerated in a direction away from each other)?

 

They are stationary wrt each other . Is there time dilation between the two objects and is it caused  by the continuous movement away from their natural trajectory

Edited January 31, 2019 by geordief

[swansont]

  On 1/31/2019 at 5:41 PM, geordief said:

Well what about if 2 massive  objects are prevented from approaching one another(=accelerated in a direction away from each other)?

 

They are stationary wrt each other . Is there time dilation between the two objects and is it caused  by the continuous movement away from their natural trajectory

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That would be covered by GR, not SR, but the time dilation would, in general, not be the same. Only for particular values of M and r would you get such a solution.

[Mordred]

  On 1/31/2019 at 3:55 PM, geordief said:

When you say "the average rate of time  in a given locale" do you mean as measured from another frame of reference?

You are not referring to proper time in different locales,do you?

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Depending on the extremes of examination, technically each coordinate has its own rate of time, two coordinates side by side could have extremely small differences. For example the rate of time at you feet is different than your head. So by average I mean for the volume of the state being examined or a region where Newton's laws of inertia and Galilean vector addition apply to good approximation or where one can consider that region as homogeneous and isotropic in mass density (Euclidean flat). As each coordinate in that region can have different time rates one must average the mass density of the region.