Time and Motion

[geordief]

I have heard that we only have "time" as a result of motion (relative ,of course).

But I have also heard ,(in contradiction) that  there are events that occur which do not exhibit motion  (eg spontaneous decay,random but statistically time ordered.).

If we just address for now the areas where time and motion are seemingly  directly linked (classical physics ,I guess) can I ask which of the two phenomena  could be considered more fundamental ?

 

Does Time  cause motion or does motion cause our perception of time?

 

Also ,in the cases** where we have time without motion,is it completely meaningless to talk about a frame of reference for the  systems at the heart of such processes?

 

** such as radioactive decay.

[Lasse]

On 2018. 04. 01. at 11:37 AM, geordief said:

we have time without motion

How something can be universally static?

Everything has reference points at least in the form of space (time).

 

 

[swansont]

On 4/1/2018 at 6:37 AM, geordief said:

 Does Time  cause motion or does motion cause our perception of time?

Time does not "cause" anything.

Perception of time is a physiological phenomenon, not physics. In physics, though, motion does not cause time. 

[geordief]

19 minutes ago, swansont said:

Time does not "cause" anything.

Perception of time is a physiological phenomenon, not physics. In physics, though, motion does not cause time. 

Yes ,apologies for the use of "perception".

 

If motion does not "cause time" ,does  anything?

 

Can we point to anything that  produces a measurement involving "time" either on the micro or on the macro level? (take away the initial** condition/requirement  and the time measurement will not follow)

 

**is "initial" a time derived term? (it seems to call for/imply  an arrow of time)

 

 

[StringJunky]

11 minutes ago, geordief said:

If motion does not "cause time" ,does  anything?

Motion is d/t. How can it be the 'cause' of time when time is part of it?

[geordief]

Just now, StringJunky said:

Motion is d/t. How can it be the 'cause' of time when time is part of it?

Sorry ,my phrasing was ambiguous. 

My "if" was an acceptance of Swansont's proposition that motion does not cause time

[StringJunky]

1 minute ago, geordief said:

Sorry ,my phrasing was ambiguous. 

My "if" was an acceptance of Swansont's proposition that motion does not cause time

OK.

[geordief]

1 hour ago, Lasse said:

How something can be universally static?

Everything has reference points at least in the form of space (time).

 

 

Yes I agree with that. I don't even think any phenomenon can be locally static ,although what causes change  seems (to me at any rate)  unknown in cases like spontaneous  radioactive emission where statistic likelihood  seem to be the only causative  contributor to the outcome.

[Lasse]

1 hour ago, geordief said:

Yes I agree with that. I don't even think any phenomenon can be locally static ,although what causes change  seems (to me at any rate)  unknown in cases like spontaneous  radioactive emission where statistic likelihood  seem to be the only causative  contributor to the outcome.

Still has a 3D space with(in) the time of recognition of the observable, measurable, determinable physical process.

Edited April 8, 2018 by Lasse

[geordief]

2 minutes ago, Lasse said:

Still has a 3D space within the time of recognition of the observable, measurable, determinable physical process.

You mean a well defined 3d space? Are you talking about "spontaneous  radioactive emission"?

[swansont]

5 hours ago, geordief said:

Yes ,apologies for the use of "perception".

 

If motion does not "cause time" ,does  anything?

What causes length? It's likely the same thing that causes time, if time has a cause.

5 hours ago, geordief said:

Can we point to anything that  produces a measurement involving "time" either on the micro or on the macro level? (take away the initial** condition/requirement  and the time measurement will not follow)

 

**is "initial" a time derived term? (it seems to call for/imply  an arrow of time)

 

A clock or stopwatch produces a measurement involving time. 

[geordief]

12 minutes ago, swansont said:

A clock or stopwatch produces a measurement involving time. 

A stopwatch  is simply an ordered arrangement of moving constituent parts . You could say the same  of any natural physical system  with movements   that could be compared to one another . Ie ,anything at all. There is nothing at all  that could not be used as a rough   timing device .

[swansont]

1 hour ago, geordief said:

A stopwatch  is simply an ordered arrangement of moving constituent parts . You could say the same  of any natural physical system  with movements   that could be compared to one another . Ie ,anything at all. There is nothing at all  that could not be used as a rough   timing device .

Not if it's random. The decay of a specific nucleus, for example, would not work.

[geordief]

1 hour ago, swansont said:

Not if it's random. The decay of a specific nucleus, for example, would not work.

What about the half life? Is that "built into" the randomness ?

Wait long enough and you have your timepiece?

Hope I have not wildly misunderstood the process.

Atomic decay is used in radiocarbon dating ,isn't it?

[swansont]

10 hours ago, geordief said:

What about the half life? Is that "built into" the randomness ?

Wait long enough and you have your timepiece?

Hope I have not wildly misunderstood the process.

Atomic decay is used in radiocarbon dating ,isn't it?

The half life is a result of the randomness. If you have a large enough sample, you know that half of the nuclei will decay in one half-life, precisely because it's random. But you don't know which ones. 

Radiocarbon — C-14 decay, is one process. Half-life is 5730 years. But if you look at one atom, you don't know if it's going to decay in the next ten seconds, or not until ten thousand years have passed. 

[StringJunky]

2 minutes ago, swansont said:

The half life is a result of the randomness. If you have a large enough sample, you know that half of the nuclei will decay in one half-life, precisely because it's random. But you don't know which ones. 

Radiocarbon — C-14 decay, is one process. Half-life is 5730 years. But if you look at one atom, you don't know if it's going to decay in the next ten seconds, or not until ten thousand years have passed. 

If it's random, how do elements have particular half-lives?

[swansont]

9 minutes ago, StringJunky said:

If it's random, how do elements have particular half-lives?

The probability is not the same for each isotope.

If the probability of decay in time dt is L, and you start with N atoms, then in that time, the number of atoms undergoing decay is LN. L (often represented by lambda) is the constant of proportionality

dN/dt = -LN

[StringJunky]

1 minute ago, swansont said:

The probability is not the same for each isotope.

If the probability of decay in time dt is L, and you start with N atoms, then in that time, the number of atoms undergoing decay is LN. L (often represented by lambda) is the constant of proportionality

dN/dt = -LN

I'll play with that formula, thanks.

[swansont]

2 minutes ago, StringJunky said:

I'll play with that formula, thanks.

Rearrange and integrate (and some more math) and you will eventually come up with the exponential decay formula

[StringJunky]

Just now, swansont said:

Rearrange and integrate and you will come up with the exponential decay formula

Right. Thank you.

[geordief]

44 minutes ago, swansont said:

The half life is a result of the randomness. If you have a large enough sample, you know that half of the nuclei will decay in one half-life, precisely because it's random. But you don't know which ones. 

Radiocarbon — C-14 decay, is one process. Half-life is 5730 years. But if you look at one atom, you don't know if it's going to decay in the next ten seconds, or not until ten thousand years have passed. 

Is L  a universal constant** and the period of time applicable open ended  ?( so "ten thousand years" for any particular atom could as well be the life of the universe....simply  less likely  )

** just experimentally verified without any a priori  reason that it should have that particular value.....

[Eise]

On 4/1/2018 at 12:37 PM, geordief said:

Does Time  cause motion or does motion cause our perception of time?

Neither.

In the first place I would replace 'motion' with 'change'. Every motion is a change (of location). but maybe not all changes are motions. 

To ask for the cause of time is a category error. There only exist causal relationships between events. And events exist in space and time. On the other side, we conclude that there are causal relationships, because we recognise that there are regularities in the occurring of events that are close in space and in time. So change, motion, space, time and causality are conceptually linked to each other. 

With that in mind, I am inclined to say that time is the most generic abstraction of change. (whereby 'change' is already a highly abstract concept: the sun going under, a car accelerating, me writing this sentence: they are all changes.)

A relationship between concepts must not be causal at all: it can be a relationship of generality. 'Change' e.g. is more general than 'motion', like 'car' is more general than 'SUV'. And you would not say that cars are the causes of SUVs.

21 hours ago, StringJunky said:

Motion is d/t. How can it be the 'cause' of time when time is part of it?

Depends on how you build up your conceptual system. If I might rephrase:

v = d/t => t = d/v

Now we have defined t as 'distance per motion'. The faster the motion, the shorter the time. 

I think what you prefer is what is the easiest understandable, or the easiest to measure. As long as the conceptual meaning stays the same, it is OK. But do not mixup a conceptual relationship with causality.

[geordief]

15 minutes ago, Eise said:

Neither.

In the first place I would replace 'motion' with 'change'. Every motion is a change (of location). but maybe not all changes are motions. 

 

Have you an example of a physical change which  does not involve a motion?

Since motion appears to me to be inbuilt into   everything I can see that it may be impossible to show this as  the "environmental"   ever present motion would  drown out the signal of any change that occurred with no "additional"  motion.

 

Or we can just accept perhaps that all changes do involve a motion (some motions being apparently continuous and some with no intervening physical locations) 

 

[studiot]

37 minutes ago, Eise said:

In the first place I would replace 'motion' with 'change'. Every motion is a change (of location). but maybe not all changes are motions. 

As ever I come in to say that Nature is never that simple.

 

Suppose I my watch is displaying 1200 noon and I check my watch against the national time signal every 12 hours for a week and each reading show 1200.

 

Should I conclude that

 

1) The watch is keeping correct time and that the hands are moving?

or

2) That the watch has stopped and the hands are not moving?

Edited April 9, 2018 by studiot

[swansont]

1 hour ago, geordief said:

Is L  a universal constant** and the period of time applicable open ended  ?( so "ten thousand years" for any particular atom could as well be the life of the universe....simply  less likely  )

** just experimentally verified without any a priori  reason that it should have that particular value.....

L has a different value for each unstable nucleus. There are models that give answers, though I couldn't tell you how precise they are. Alpha decay, for example, can be modeled as an alpha particle tunneling out of a potential well.  And there are trends one can apply — for a given type of decay, a larger release of energy typically correlates to a shorter half-life.