Relativity Explained Via Movement, Not Time

[atyy]

OK, let's try to see if some version of Hassan's proposal can hold. How about "time requires movement, but movement does not require time"?

Let me define movement as change dy/dx. dy/dx does not require time, since x, especially if x is 3D Euclidean space in Newtonian physics, doesn't seem to be necessarily time.

However, time requires dy/dx to be operationally defined, in some special cases where x = "time".

In this sense movement is primary, but time is not.

 

[Dale]

I believe that explanations of physical phenomenon -including relativity- would be so much easier using *movement* instead...

IH

How would you explain relativity using movement instead of time? In particular, how would you make the quantitative experimental predictions of relativity without time?

 

[my_wan]

The thing is the thesis of this post: Relativity explained via Movement, not "Time". In fact, we could re-write the title:

'Relativity Explained by L/t, not "t".'

Well enough. I don't think that's too far from what Einstein said, the L/t in question being c, which is a constant in all observers' frames of reference. Sorta QED, no?

There it is. A lot of OPs are started with a sliver of recognition followed by alphabet soup.

 

[danR]

Originally Posted by danR
The thing is the thesis of this post: Relativity explained via Movement, not "Time". In fact, we could re-write the title:

'Relativity Explained by L/t, not "t".'

Well enough. I don't think that's too far from what Einstein said, the L/t in question being c, which is a constant in all observers' frames of reference. Sorta QED, no?

There it is. A lot of OPs are started with a sliver of recognition followed by alphabet soup.

Let me clean it up a bit then:

The OP could be titled:

'Relativity Explained by Length/time, not time.'

For Einstein the Length/time in question being distance traveled by light/time, which is a constant in all frames of reference. So we are right back stuck with time, and Einstein and everyone still using time are actually still right to do so, Which was the thing to be demonstrated (by way of rebuttal).

 

[danR]

OK, let's try to see if some version of Hassan's proposal can hold. How about "time requires movement, but movement does not require time"?

Let me define movement as change dy/dx. dy/dx does not require time, since x, especially if x is 3D Euclidean space in Newtonian physics, doesn't seem to be necessarily time.

However, time requires dy/dx to be operationally defined, in some special cases where x = "time".

In this sense movement is primary, but time is not.

Only by treating time as a spatial axis. This seems akin to a Minkowski manifold.

But now there is no movement!

 

[Islam Hassan]

Let me formulate the subject a little differently then: does time exist in the sense of some immaterial yet physically effective 'ether' flowing through space? To my (rather confused) mind if it is immaterial in the sense that it is not observable *in itself*, it does not exist per se but is a practical concept we evolved in order to facilitate communication.

IH

 

[ZapperZ]

Let me formulate the subject a little differently then: does time exist in the sense of some immaterial yet physically effective 'ether' flowing through space? To my (rather confused) mind if it is immaterial in the sense that it is not observable *in itself*, it does not exist per se but is a practical concept we evolved in order to facilitate communication.

IH

This is a very tired topic because it has been discussed ad nauseum in this forum.

It is also quite confusing because you are asking for whether time, which can be measured quantitatively, can be defined using some esoteric, undefined quality ("immaterial yet phyically effective ether flowing through space"). That's like asking how physics can be defined using metaphysics! All of this is ignoring the fact that space itself can't be decoupled and separately measured without time!

Considering that there are numerous phenomena that are characterized by their broken time reversal symmetry, from that point of view, it is awfully silly to ask if time exists.

Zz.

 

[dx]

Independent 'existence' of space, time as well as matter is charactertic of Newtonian physics, i.e. we imagine a 'space' which is 'unaccelerated', and point particles (which in principle are imagined to constitute material objects) moving in this space. Thus we ascribe physical reality to space as well as to its state of motion. This is necessary because the idea of acceleration appears in Newton's law of motion. The same applies to time, which likewise enters into the concept of acceleration. So to summarize, in Newtonian physics 'physical reality' consists of space, time and material points moving with respect to space and time.

In the special theory of relativity, the four dimensional continuum of spacetime is no longer objectively resolvable into space and time, but this space (Minkowski space) occurs as an independent component in the representation of physical reality as carrier of matter and field.

In the general theory of relativity, the inertial frame loses its objective significance for the following reason. A frame accelerated with respect to an inertial frame can be thought of as an inertial frame together with a uniform gravitational field. Thus, space, as opposed to what fills space (represented by fields, and which depend on the coordinates) has no independent existence.

 

[atyy]

Let me formulate the subject a little differently then: does time exist in the sense of some immaterial yet physically effective 'ether' flowing through space? To my (rather confused) mind if it is immaterial in the sense that it is not observable *in itself*, it does not exist per se but is a practical concept we evolved in order to facilitate communication.

All quantities in physics are not observable "in themselves". For example, what is a charge? What is an electric field? There isn't a concept of charge independent of the field, and there isn't a concept of the field independent of the charge. Although there are formal solutions for fields without charges, we cannot observe these fields unless we have a charge.

All quantities in physics are concepts we evolved to consistently describe our observations, communicate with each other, and design devices that work the way we predict. But they are all (as far as we know) wrong at some level.

So a question about what "time" is, must take place within each of our limited but useful theories. Each theory will have its own definition of "time", which may overlap only partially with the notion of "time" in another one of our theories. Among these different notions of time are coordinate time and proper time of general relativity, cosmological time in the FRW solution of general relativity, thermodynamic time in the second law of thermodynamics, Newtonian coordinate time in Newtonian physics, psychological time in psychological experiments etc.

 

[Arens]

All quantities in physics are not observable "in themselves". For example, what is a charge? What is an electric field? There isn't a concept of charge independent of the field, and there isn't a concept of the field independent of the charge. Although there are formal solutions for fields without charges, we cannot observe these fields unless we have a charge.

Taken from wiki:
Electric charge is a physical property of matter which causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two negatively charged objects. the electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic fields.

Time is not matter, is a notion we use to determine movement of an object from A position to B , respective to another movement made from another object from C to D.

 

[DaveC426913]

Electric charge is a physical property of matter which causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two negatively charged objects. the electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic fields.

Well there you go atyy; you have been educated on what electric charge is. :rofl:


Arens, seriously though. Quoting someone else's material - http://en.wikipedia.org/wiki/Electric_charge" - without credit is forbidden, and will result in infractions.

 

[Islam Hassan]

Ok thanks to everyone! Sorry I didn't realize that this topic had been discussed 'ad nauseam' before in PF: it was my very first post here. Will be more careful with my posts in the future.

At any rate, it seems that time is a considerably more intricate subject than I imagined; thank you again for your kind forebearance.

IH

 

[Selraybob]

I'm with you, Islam, except Time's not that complicated. Time's a count. Nothing more. I don't know why people make it so complicated. Aristotle started off okay, calling it a count, but he mucked it all up with the Now. And Einstein made it a fourth dimension and got everyone excited about space-time. But Time's a count. Even the NIST guys, who are supposedly measuring 'Proper Time' call Time a count right outside their clock. (Yep, I was there. It’s a big tube with mirrors all around. I even saw the new one, which wasn’t working. Really cool, the NIST guys and the clocks.) Here’s what the sign says:

“Time is defined as the accumulation of atomic seconds beginning 0000 Hours UT (Earth time) 1 January, 1958.”

That's why I can't go with ZapperZ:

"It is also quite confusing because you are asking for whether time, which can be measured quantitatively..."

Unless Time is defined as the changes in a cesium atom, or a count of changes, then Time can't be measured quantitatively. Every time you ask someone to measure Time, they find some counter that measures some change in something else. Clocks, sundials, whatever, they're all counters. And none of them works the same.

Even the NIST guys have to synchronize their clocks. They’ve got a few, and they only start the main one for a week every month so that they can set the others and then send out the official count all over the world. No clock counts the same all the time. It depends on where they are and the temperature and all sorts of things.

Atyy, though, got me thinking when he said that concepts in physics are wrong in some way. My problem is that whenever you look at a measure for just about anything, somewhere back there is little t. And little t is a count of some counter, which always changes, because how your counter works depends on where it is and what all the conditions are around it. Still, thinking’s good.

 

[Dale]

Time's a count.

A count of what?

 

[my_wan]

A count of what?

Events. Nobody can claim to absolutely know what a base event is or even if there is such a thing as a base event predicated on any particular ontology. Yet as long as there are events and systems are defined by sets of event, or sets of sets, and so on, then certain higher order events, linear relative to the base event sets of whatever ontology, can then be used as proxies to count said events. It works that way whether the system is purely mechanistic or it is merely relative to some abstraction of the laws of physics. Hence we have higher order measuring devices called clocks that count these linear events.

 

[Dale]

Events.

Well, it can't just be any events since some events are space-like separated, and even for timelike separated events I can think of examples where you wouldn't call the resulting count time.

 

[Selraybob]

It is events. When I say "Time is a count", it's really saying that since the first caveman looked at the moon and grunted out something like, "moon above again," and then made a mark on the wall, and then another the next time the moon was above, is counting up some events and calling that Time. It's the counting that comes first and the definition of Time that comes after. You can count moons moving around the Earth or suns appearing to move around the Earth or the ticks of a grandfather clock or water clock or atomic clock. But for comparing our lives against, and meeting someone down at the dock, it's good to have some sort of counter that's pretty regular. Doesn't matter what it is though.

 

[Dale]

It is events. ... Doesn't matter what it is though.

So counting ticks on my Geiger counter is time. If I put my Geiger counter in a lead box time stops. Is that really what you meant, because that is what you said.

Here is another set of events, the tick marks on my ruler when illuminated by a specific of light. The count is 12. So time is 12. Doesn't sound like your definition is related to the usual idea of time.

 

[my_wan]

Well, it can't just be any events since some events are space-like separated, and even for timelike separated events I can think of examples where you wouldn't call the resulting count time.

True, which is exactly what gets us into trouble with simultaneity, which I even recently embarrassed myself with. Yet even then the one constraint that allows us to define the relativity of simultaneity is the constraint that a 'local' event set sequence, E_i --> E_j --> E_k, cannot place any event in the set both before and after some other event in that set. That would amount to time travel.

Even if we assumed some 'toy' model of purely mechanistic events such as molecular collisions, if the background is undefined then local event sets must disagree on clock rates in many different circumstances.

 

[Dale]

True, which is exactly what gets us into trouble with simultaneity, which I even recently embarrassed myself with. Yet even then the one constraint that allows us to define the relativity of simultaneity is the constraint that a 'local' event set sequence, E_i --> E_j --> E_k, cannot place any event in the set both before and after some other event in that set. That would amount to time travel.

Even if we assumed some 'toy' model of purely mechanistic events such as molecular collisions, if the background is undefined then local event sets must disagree on clock rates in many different circumstances.

So then what sets of events can you count and call the resulting count "time"?

 

[my_wan]

So counting ticks on my Geiger counter is time. If I put my Geiger counter in a lead box time stops. Is that really what you meant, because that is what you said.

Here is another set of events, the tick marks on my ruler when illuminated by a specific of light. The count is 12. So time is 12. Doesn't sound like your definition is related to the usual idea of time.

If you insure that those ticks are scaled properly yes, which is why we can do carbon dating. Yet like the linear discontinuities you can get from any given pair of individual clicks we have the uncertainty principle telling us we are getting these small scale discontinuities at a fundamental level also. But averaged over they go away.

 

[Dale]

If you insure that those ticks are scaled properly yes

OK, so now we are no longer counting, but counting and scaling our count. That is fine, how do we determine the correct scaling factor for the count?

 

[my_wan]

OK, so now we are no longer counting, but counting and scaling our count. That is fine, how do we determine the correct scaling factor for the count?

Relative to any other local event set with has a reasonably stable linearity. The most fundamental of which is apparently a Planck unit of time, which is subject to the Uncertainty Principle. If you arbitrarily presume some mechanistic basis then what makes it linear does not mean linear in any absolute sense, it just means linear with respect to the mean local fundamental event sets defining the system. After all, relative to a clock under an acceleration of proper motion, linearity in terms of time alone loses relevance.

 

[my_wan]

The scaling is required simply so that our choice of event sets to count time is independent of the particular set of events used to do the counting.

 

[Dale]

Relative to any other local event set with has a reasonably stable linearity.

So the tick marks on a ruler is a good example since it is stable and very linear.

 

[Dale]

The scaling is required simply so that our choice of event sets to count time is independent of the particular set of events used to do the counting.

That doesn't make any sense at all if time IS the count. How can time be the count of events and yet be independent of the events counted?

 

[my_wan]

That doesn't make any sense at all if time IS the count. How can time be the count of events and yet be independent of the events counted?

It is not independent of the count, which is the point. But if you have an event set, and many different ways of combining those set and subsets, then to get any meaningful count they all must be given a consistent scale, even though nature is scale independent in general. The reason they can be scaled together would be because they are are mere regrouping of the same sets.

 

[Dale]

It is not independent of the count

You just said that you needed to scale it so that it was independent.

to get any meaningful count they all must be given a consistent scale

And exactly what is it that must be consistent about the scale? In other words, you have two valid sets of events to count and you scale one by a factor of two in order to achieve consistency, what is it about the events that required a factor of two scaling to achieve consistency, and how can you know that you need a factor of two and not three?

 

[my_wan]

You just said that you needed to scale it so that it was independent.

I said independent of our "choice" of event sets, not independent of the events themselves.

And exactly what is it that must be consistent about the scale? In other words, you have two valid sets of events to count and you scale one by a factor of two in order to achieve consistency, what is it about the events that required a factor of two scaling to achieve consistency, and how can you know that you need a factor of two and not three?

Two parts:
1: "events that required a factor of two"
If you have a single finite superset of events and you have a measuring device that measures ticks for ever pair of events, then that MUST relativistically scale as 2 times every event. How much linearity there is between the individual events is immaterial, like claiming you can stop time for some specified period of time. Even if it we overlook the silliness and presumed it did occur it has NO empirical meaning.

2: "how can you know that you need a factor of two and not three"
Because the clock that counted one event for every two events would not be linear by any measure other than a 2 to 1 ratio. This ratio is what defines what we can measure, not the naked quantity in itself. That would require absolutes like in Newtonian physics.

 

[Dale]

Unfortunately, I will not be able to continue the conversation tonight. I thought it would take fewer iterations than it did.

The point is that this definition of "time is counting events" is not sufficient. There are some events which counting them doesn't measure time because the events are separated by space, not time. There are other events which counting them does not measure time because they are at random intervals. For still other sets of events you have a good feeling that they are measuring time, but you have to scale your counts in order to say that they are all measuring time. So for all of these reasons there is more to measuring time than simply counting events.

All of these objections can be addressed, but to do so requires that you identify something about the various counts beyond the mere counting itself. The very fact that you can use counts of a variety of sets of events (properly scaled) to measure time indicates that there is something else besides simply the counting.

Unless you already have some concept of time already then there is no way to distinguish between spacelike sets of events and timelike sets of events. Unless you already have some concept of time then there is no way to determine if the scaling is correct.

What the counts and their scaling do is to define a unit of time, not to define time.

 

[danR]

I don't know how this post 'relativity explained by movement, not time' got so far off track.
You got movement, you got:

(amount of) space/time.

Time will always be around in the physics-conversation.

 

[my_wan]

Unfortunately, I will not be able to continue the conversation tonight. I thought it would take fewer iterations than it did.

I am accustomed to certain people, including physicist, who seem to grasp it straight away as though it was too obvious to mention, and others who find it very difficult.

The point is that this definition of "time is counting events" is not sufficient.

Is actually is sufficient. In fact from a purely empirical perspective some form of event counting is ALL we have. The derivation of the relativity of simultaneity is possible exactly because we can count event rates of external observers as measured by our own evet rate counters and compare the compare the incongruities. If time existed independently of these event counts why would the difference in events counts result in an actual difference in time rates per Lorentz? The one issue that imposes any other constraints that might qualify as indicating "count" is not "sufficient" is the extra constraint imposed by causality itself, i.e., the same event cannot occur both before and after a reference event at a point in space.

There are some events which counting them doesn't measure time because the events are separated by space, not time.

In those situations where the event count does not match your own local event count then you are measuring is not your own event count but somebody else's. Which we know to be real differences in real time else you could not come back younger than your own kids. The separation by space rather than time is moot by the inverse relation between space and time such that empirically they are not separate quantities.

There are other events which counting them does not measure time because they are at random intervals.

The randomness of an interval does not invalidate the linearity of those intervals on average. The rate of molecular collisions also have highly random intervals. Yet in order for Gibbs ensembles to have any empirical meaning they must average to a constant if equilibrium is maintained. This is the physical basis of emergent gravity theories based on relations defined by Brustein and Hadad and others where equilibrium is not maintained.
http://arxiv.org/abs/0903.0823

Randomness of intervals do not have any relevance to the constancy of average intervals one way or the other, but it would have relevance to the certainty with which we could, even in principle, determine a precise location in space or time relative to any observer.

For still other sets of events you have a good feeling that they are measuring time, but you have to scale your counts in order to say that they are all measuring time.

If I locally measure an inertial string and say it has a lengths of X and you measure it locally and say it has has a length of Y, why must we scale X and Y so to be equivalent? Because we are measuring the "same" string. Same thing if we are both measuring the "same" general set of local events. How do you treat background independence by any other means?

So for all of these reasons there is more to measuring time than simply counting events.

For all those same reasons, plus background independence causality, "counting events" is completely "sufficient".

All of these objections can be addressed, but to do so requires that you identify something about the various counts beyond the mere counting itself.

Yes, they can be enumerated as such:
1: Causality - The same event A cannot occur 'both' before and after event B at any given point in space-time.
2: Background Independence - The rate of a non-observable is empirically moot irrespective of what role it plays in the theoretical framework.
3: Relational, i.e., Relativity - The only value we can measure are not naked values, rather ratios which we assign a specific value to as though our local base event sets defined absolutes.

The very fact that you can use counts of a variety of sets of events (properly scaled) to measure time indicates that there is something else besides simply the counting.

Yes causality constraints. Yet the fact that locally the event sets being measured in for all practical purposes the same set of events requires that both measures scale together. Hence the scaling requirement is a physical requirement of consistency. Not some magical entity that exist in a matter free background.

Unless you already have some concept of time already then there is no way to distinguish between spacelike sets of events and timelike sets of events.

Absolutely true and well established physics, which is precisely why we get the so called clock paradox in SR. We can only make such distinction locally, due to the fact that we are essentially measuring the same space-like and time-like sets. Once you consider other points in space-time what you say here about the event count ideology is exactly true and well defined by Relativity. You can only pretend that space and time-like intervals are unique in pair of reference frames by assuming that one of those frames has a special status in its capacity to define those distinctions.

Unless you already have some concept of time then there is no way to determine if the scaling is correct.

If a ruler and a string were all that existed in the Universe how do you know the scaling of the ruler is correct. With background independence (also called coordinate independence) 'correctness' of a scale makes no difference whatsoever. We know that the ruler can linearly scale to itself and we know the ratio between the ruler and the string, what else empirically matters? How big the ruler and the string both are is a physically absurd empirically moot question.

What the counts and their scaling do is to define a unit of time, not to define time.

So if a Hilbert space is a mathematical tool with no 'real' physical significance, what makes the mathematics of defining time so special that somehow it is not only more real but 'real' independently of the intervals we measure? (That is not saying it is dependent on our choice of interval sets.)

 

[atyy]

@DaleSpam: @my wan: Is the difference between your points of view that physics is always the study of change dy/dx, but if there is only one "dimension" DaleSpam would call that "space" and my wan would call it "time"?

 

[Dale]

In those situations where the event count does not match your own local event count then you are measuring is not your own event count but somebody else's.

No, the count of a set of spacelike separated events is not measuring anyone's time.

For all those same reasons, plus background independence causality, "counting events" is completely "sufficient".

Yes, they can be enumerated as such:
1: Causality - The same event A cannot occur 'both' before and after event B at any given point in space-time.
2: Background Independence - The rate of a non-observable is empirically moot irrespective of what role it plays in the theoretical framework.
3: Relational, i.e., Relativity - The only value we can measure are not naked values, rather ratios which we assign a specific value to as though our local base event sets defined absolutes.

Yes causality constraints.

You are contradicting yourself saying that "counting events" is completely sufficient and then adding constraints. The "time is counting events" definition is clearly insufficient as you have de facto conceded. You must add such enumerated constraints or clarifications as above.

The causality constraints are particularly problematic for a definition of time. Causality requires a notion of time, so putting a causality constraint into your definition of time makes the definition circular. In particular, without a definition of time how do you determine "before" and "after"?

Btw, I am not opposed to a background independent relational definition of time. I just think that "time is counting events" is way oversimplified. Something this important needs quite a bit more effort and care than that. Many things which qualify as counting events do not qualify as measuring time.

 

[Dale]

@DaleSpam: @my wan: Is the difference between your points of view that physics is always the study of change dy/dx, but if there is only one "dimension" DaleSpam would call that "space" and my wan would call it "time"?

I have not asserted a point of view here, I am only pointing out that "time is counting events" does not work. I believe that I understand my_wan's motivation, I think he wants to avoid the Newtonian idea of time as some undetectable thing which flows and instead focus only on the physical observables. I agree with that goal; I just think that his approach is not right.