How do relativistic effects change oscillation of the balance wheel in mechanical watch causing it to tick slower?

[Jurgen M]

So now I don’t understand what your question is. You asked about a mysterious other force but you already know that there is no force. So please try to write your question again, but clearly this time. Don’t ask about a force that you know doesn’t exist. Ask your actual question, please.

My question was ,first does watch tick slower and then if answer is yes, explain how constant speed can slow down blance wheel oscilation,because to make wacth to tick slower you must change balance wheel oscilation..

 

[Dale]

explain how constant speed can slow down blance wheel oscilation,because to make wacth to tick slower you must change balance wheel oscilation.

OK, this is the part that I answered already:

Mechanical watches are usually designed using Hooke’s law and Newton’s laws. Neither of those are relativistic in their usual form. If you generalize Hooke’s law and Newton’s laws to their relativistic forms then you naturally get that mechanical watches exhibit time dilation as normal. In other words, it is not any additional force, it is just how the usual forces actually work at high speeds.

 

[PeterDonis]

usualy when you say tick slower that mean it is real and when you say appear that mean it is not real just apper ti be real.

What does "real" mean? What's the difference between "real" and "appear to be real"?

Bear in mind that this is a physics forum, not a philosophy forum. Terms like "real" and "appear to be real" cannot just be thrown around. You have to be able to relate them somehow to the physics that is being discussed. If you can't, then questions involving those terms are meaningless as far as physics is concerned.

 

[DaveC426913]

You have to be able to relate them somehow to the physics that is being discussed.

That's why I stick closely to things that are observed.

 

[Dale]

I don't know, usualy when you say tick slower that mean it is real and when you say appear that mean it is not real just apper ti be real.

This is rather meaningless. What we can meaningfully say is the following:

If we have an inertial lattice of Einstein-synchronized watches and an identical watch that is moving inertially with respect to the lattice, then the time shown on the moving watch will tick slower than the time shown on the lattice watches as the moving watch passes each lattice watch.

 

[PeterDonis]

If we have an inertial lattice of Einstein-synchronized watches and an identical watch that is moving inertially with respect to the lattice, then the time shown on the moving watch will tick slower than the time shown on the lattice watches as the moving watch passes each lattice watch.

Rather than say "tick slower", since that is the phrase that appears to be causing confusion, it might be better to rephrase this as: "the moving watch will show less elapsed time between passing two successive lattice watches than the difference of the times shown on the two lattice watches". That states the invariant observable fact without making any claims about how, or even whether, this fact relates to "tick rates" of clocks.

In the lattice rest frame, the simple way to account for the fact just described is that the moving watch is ticking slower than the lattice watches due to time dilation.

In the moving watch's frame, the simple way to account for the fact just described is that the lattice watches are desynchronized by an amount that more than compensates for the fact that the lattice watches are ticking slower than the moving watch due to time dilation.

However, neither of those frame-dependent explanations is necessary; one can always describe things entirely in terms of invariants, in this case the invariant lengths of the appropriate segments of timelike worldlines.

 

[PeroK]

My question was ,first does watch tick slower and then if answer is yes, explain how constant speed can slow down blance wheel oscilation,because to make wacth to tick slower you must change balance wheel oscilation..

Imagine three observers measuring the time shown on a watch. One observer remains at rest relative to the watch and the observers move at different speeds relative to the watch. Now, all three observers measure the watch ticking at different rates.

As far as the watch is concerned nothing has changed. It can't know it's being observed and can't physically be going at three different rates at the same time. The observed time dilation must be a non-physical effect, caused by the geometry of spacetime and not by mechanical interefence with the watch's mechanism.

 

[Jurgen M]

"The rate at which the watches tick is the same. The number of ticks is different, because one watch experiences a longer elapsed time than the other"

How would you explain these words, is this correct?

 

[PeterDonis]

"The rate at which the watches tick is the same. The number of ticks is different, because one watch experiences a longer elapsed time than the other"

Where do those words come from?

 

[Dale]

"The rate at which the watches tick is the same. The number of ticks is different, because one watch experiences a longer elapsed time than the other"

What does it mean?Is this correct?

As with most statements that don’t explicitly describe an experiment, you can interpret it in a way to refer to a correct experiment or an incorrect experiment. In particular, here the phrase “rate at which the watches tick” can be interpreted as different experiments.

1) measure the rate at which the watch ticks by comparing it to an atomic clock that is at all times co-located with the watch.

2) measure the rate at which the watch ticks by using an inertial lattice of Einstein-synchronized atomic clocks and at each moment comparing the watch time to the time of the momentarily co-located atomic clock.

Then “the rate at which the watches tick is the same” is true for 1) and false for 2).

 

[Nugatory]

"The rate at which the watches tick is the same. The number of ticks is different, because one watch experiences a longer elapsed time than the other"

How would you explain these words, is this correct?

Those words are (with appropriate context and supporting commentary) a reasonable informal explanation of the twin paradox.

They are (at least in my opinion) far less helpful in understanding time dilation, the topic of this thread.

 

[Jurgen M]

Those words are (with appropriate context and supporting commentary) a reasonable informal explanation of the twin paradox.

They are (at least in my opinion) far less helpful in understanding time dilation, the topic of this thread.

What is difference between my topic and two clocks in twin paradox?

 

[PeroK]

What is difference between my topic and two clocks in twin paradox?

You are asking about time dilation. The twin paradox is about differential ageing.

 

[Jurgen M]

You are asking about time dilation. The twin paradox is about differential ageing.

In twin paradox clock that was on rocket, when comes back to Earth , show less time than clock at earth.
Isnt this same question as my?

And how this can happened if both clocks can say " I am clock that is at rest" ?

 

[PeroK]

In twin paradox clock that was on rocket, when comes back to Earth , show less time than clock at earth.
Isnt this same question as my?

No. It's not the same question. Time dilation is symmetric and motion is relative.

Differential ageing results from two objects taking different paths through spacetime. The length of a spacetime path is an invariant quantity.

And how this can happened if both clocks can say " I am clock that is at rest" ?

It can happen because of the properties of Minkowski spacetime geometry.

If you want to discuss the twin paradox, you should open a new thread. But, unless you understand the basics of time dilation, then discussion of the twin paradox will be even more painful.

 

[jartsa]

A clock whizzes past Bob. Bob says: "In my opinion that clock is moving. And in my opinion the balance wheel of that clock has extra rotational inertia. And in my opinion the spring constant of the spring connected to the balance wheel of that clock is extra small. And in my opinion that clock is ticking slowly."So according to Bob the clock is moving. And according to Bob the balance wheel of the clock has extra rotational inertia. And according to Bob the spring constant of the spring connected to the balance wheel of the clock is extra small. And according to Bob the clock is ticking slowly.In my opinion this is a correct way to speak.

 

[PeroK]

In my opinion physics is about measurements and not opinions!

 

[Jurgen M]

In my opinion physics is about measurements and not opinions!

But different observers, different results.

 

[Dale]

But different observers, different results.

Actually, no. The result of any actual experimental measurement is frame invariant. It is only the “explanation” that is frame variant, not the measured result.

 

[Jurgen M]

Actually, no. The result of any actual experimental measurement is frame invariant. It is only the “explanation” that is frame variant, not the measured result.

Observer with watch see normal clock tick rate, observer moving in relation to clock see slower tick rate.
So we have two different results.

Isnt it?

 

[PeroK]

Different observers, different results.

Better is: different frames of reference, different measurements.

This has always been the case. We routinely talk about, say, a car having "stopped" at traffic lights. But, the surface of the Earth is rotating at about ##1000 km/h## and the Earth is orbitting the Sun at about ##30,000 m/s##. The car is only at rest relative to the surface of the Earth.

Also, we may consider a collision in the "lab" frame where one object is at rest and another object is moving towards it; and, in the centre of mass/zero momentum frame where the objects are moving with equal and opposite momenta towards each other.

Sometimes it's a problem even to convince students that motion is relative and that both the "lab" and "zero momentum" frames are valid reference frames in which Newton's laws hold.

And, if the student ovrecomes that hurdle and then starts to learn SR, there is then the intellectual hurdle that lengths, elapsed times and simultaneity are also frame-dependent. This is the point at which a lot more students have problems understanding modern physics.

Nevertheless, lengths, times between events and simultaneous events are frame dependent.

 

[Dale]

Observer with watch see normal clock tick rate, observer moving in relation to clock see slower tick rate.
So we have two different results.

Isnt it?

No, we have two different experiments. Everyone agrees on the measurement results of each experiment.

That is why I insisted on describing the experiments above. If you don’t use “shortcut words” then it takes more effort to say things, but what you say is more clear.

“it takes a long time to say anything in Old Entish. And we never say anything unless it is worth taking a long time to say.” -Treebeard

 

[Jurgen M]

No, we have two different experiments. Everyone agrees on the measurement results of each experiment.

That is why I insisted on describing the experiments above. If you don’t use “shortcut words” then it takes more effort to say things, but what you say is more clear.

“it takes a long time to say anything in Old Entish. And we never say anything unless it is worth taking a long time to say.” -Treebeard

I don't agree.
This is not two different experiments, it is same experiment just looked from different perspective/frame...

 

[Jurgen M]

Better is: different frames of reference, different measurements.

It is the same thing. Observer sit at origin of frame and obsreves what is going on with objects ...

 

[Dale]

I don't agree.
This is not two different experiments, it is same experiment just looked from different perspective/frame...

Well, then what you say disagrees with the principle of relativity. The principle of relativity says that the same laws of physics apply in all inertial frames. The laws of physics are used to predict measurement results. So that implies that all frames must agree on the results of all measurements. Otherwise the predictions of some frames would be falsified by the actual measurement result.

It would help you greatly if you would start describing specific experiments and measurements. I think that you are getting confused by vague statements, both your own and from others.

 

[PeroK]

It is the same thing. Observer sit at origin of frame and obsreves what is going on with objects ...

This is perhaps a bad example, but ...

If two people are watching a soccer match from opposite sides, then one may observe a goal scored to the right and the other observe a goal scored to the left. These are measurements and are not meaningful. They agree, however, about which team has scored.

And, again, to look at classical mechanics, two observers might describe a collison differently: one observes a moving ball hit a stationary ball ...; and the other observe two balls moving towards each other, colliding and each bouncing back the way they came. The key is to establish what contintutes a physically meaningful description of the collision. E.g. they will agree about whether it was an elastic or inelastic collision and how much kinetic energy was lost.

In SR, we have to stop thinking about things like simultaneity of events being physically meaningful and, instead, concentrate on frame invariant quantities that constitute a better description of the physics.

 

[PeroK]

Well, then what you say disagrees with the principle of relativity. The principle of relativity says that the same laws of physics apply in all inertial frames. The laws of physics are used to predict measurement results. So that implies that all frames must agree on the results of all measurements.

We're talking at cross purposes here. Everyone agrees what everyone else measures, but if two people measure the same quantity (e.g. KE of an object), then they won't necessarily get the same results as each other.

 

[Dale]

We're talking at cross purposes here. Everyone agrees what everyone else measures, but if two people measure the same quantity (e.g. KE of an object), then they won't necessarily get the same results as each other.

Right, they will do different experiments to measure the quantity, the different experiments will produce different results, and all frames will agree on what each measurement result should be. They will disagree on the meaning of the measurement, but not on the measurement results.

 

[PeroK]

Right, they will do different experiments to measure the quantity, the different experiments will produce different results, and all frames will agree on what each measurement result should be. They will disagree on the meaning of the measurement, but not on the measurement results.

To take an example: the specific energy-momentum in each frame is different, but the law of physics is that energy-momentum is conserved.

 

[PeroK]

This is not two different experiments, it is same experiment just looked from different perspective/frame...

I'm inclined to agree with this. In particle collisions, we routinely move from the lab frame to the zero momentum frame and back again.

The fact that we can do that requires the change of frame to be physically meaningless!

This also highlights the problem with talking about different frames "disagreeing" about things. I've never liked the Alice and Bob approach, although I know others do like to use it. If we talk about "lab frame" and "zero momentum" frame, then it's much more explicit that we are using the laws of physics to look at the problem two different way. Whereas, the Alice and Bob approach seems like more of a challenge to the laws of physics.

The important point, however, is that any time you can say a clock is moving inertially, you may consider an inertial reference frame where the clock is at rest. And the laws of physics must apply equally in both frames.

 

[Janus]

In twin paradox clock that was on rocket, when comes back to Earth , show less time than clock at earth.
Isnt this same question as my?

And how this can happened if both clocks can say " I am clock that is at rest" ?

Your original question deals with 2 inertial frames with each clock always at rest to respect to one of the two.
The twin paradox has 3: Earth frame, rocket outbound frame and rocket inbound frame. In addition, the rocket has to transition between the outbound and inbound frames. So while in your original question each clock only has to account for time dilation when considering the other clock, with the twin paradox, the rocket clock has to take the relativity of simultaneity into account, and during the transition between outbound and inbound legs concludes that the Earth clock goes from having ticked of less time than itself to having ticked off more time.
The Earth clock, on the other hand remains at rest with respect to a single inertial frame and still only has to account for time dilation when considering the rocket clock;s relative tick rate.

The upshot is that while both clocks, upon being brought back together, agree as to which clock recorded more time during the separation, they will not agree on how it came about. And each clock's claim is equally valid.

 

[Ibix]

It is the same thing. Observer sit at origin of frame and obsreves what is going on with objects ...

...but has to subtract out the light travel time to interpret what he sees. And how he does that turns out to be equivalent to making a choice of reference frame. Ultimately, this is the source of all the differences. The wheel is a 4d object, with extent in three spatial directions and a duration. Depending on your simultaneity criterion you may take different 3d slices through it as "the wheel, now", and some of those slices are funny shapes and not necessarily rotating at the same speed.

 

[Jurgen M]

...but has to subtract out the light travel time to interpret what he sees. And how he does that turns out to be equivalent to making a choice of reference frame.

Isnt frame of reference same as observer, abstract coordinate system from which we are observes object?

 

[Ibix]

Isnt frame of reference same as observer, abstract coordinate system from which we are observes object?

The frame of reference is what an observer uses to interpret his observations. What a person actually sees is an invariant - you can't change the light falling on your retina/camera/whatever by changing your mind about what coordinate system you want to use. However, that light left its source some time ago - and when we are talking about things moving at relativistic speed you need to be very careful about how you go about subtracting out the light travel time. The exact methodology depends on the reference frame you chose, because that includes your definition of "distance" and "simultaneity", both of which you need to take "what I'm seeing now" and deduce "what was happening at a particular time".

 

[PeterDonis]

if two people measure the same quantity (e.g. KE of an object), then they won't necessarily get the same results as each other.

They're not measuring the same quantity. They're measuring different quantities that, because they are using frame-dependent language, they happen to each call by the same name. It would be better to avoid the sloppy terminology altogether and make it clear that they are measuring two different invariants, for example by describing each one mathematically as a contraction of the same object's 4-momentum with different 4-vectors describing different measurement devices in different states of motion.