What are the physical mechanisms behind time dilation and its alternatives?

[lakshminarayan]

what is the exact mechanism by which time dilates for a fast moving object.
Can the time dilation be explained by any other theory other than relativity.

 

[tiny-tim]

welcome to pf!

hi lakshminarayan! welcome to pf!

what is the exact mechanism by which time dilates for a fast moving object.

there is no mechanism for time dilation

there's only the geometry, of space-time

Can the time dilation be explained by any other theory other than relativity.

Nope!

 

[phinds]

what is the exact mechanism by which time dilates for a fast moving object.
Can the time dilation be explained by any other theory other than relativity.

It is an observational effect, not a local one. The moving object does not experience time dilation. Right now, as you are reading this, you are MASSIVELY time dilated from the frame of reference of a particle in the LHC because relative to it, you are traveling at very close to the speed of light.. Do you feel any different?

 

[lakshminarayan]

How can there be geometry to space time, if space time is infinite?

 

[Nugatory]

How can there be geometry to space time, if space time is infinite?

Geometry is about the distances and directions between points. Whether the points are in an infinite space or not doesn't matter.

 

[lakshminarayan]

But time dilation is a real phenomenon which has been tested. I might not experience time dilation, but I know time dilates for the moving object if I test it. How can it be relative when I know the result way before the relation is established between me and the moving object.

 

[HallsofIvy]

You can't possibly know what time dilation is if you do not know how fast the object is moving relative to you.

 

[phinds]

But time dilation is a real phenomenon which has been tested. I might not experience time dilation, but I know time dilates for the moving object if I test it. How can it be relative when I know the result way before the relation is established between me and the moving object.

You misunderstand completely. Reread post #3

 

[Nugatory]

But time dilation is a real phenomenon which has been tested. I might not experience time dilation, but I know time dilates for the moving object if I test it. How can it be relative when I know the result way before the relation is established between me and the moving object.

If some observer is moving relative to you, will be able to calculate that observer's clock dilation - his clock will run slow relative to your clock.

However, we could equally well say that the other observer is at rest and that you are moving relative to him - and then we will calculate that your clock is running slow relative to his clock.

Both calculations are equally correct. This is a real phenomenon that has been observed and tested. (And before you ask which clock is "really" the slow one, google for "relativity of simultaneity").

However, you'll notice that in both cases we are calculating the time dilation between a clock that is at rest relative to an observer and a clock that is moving relative to that observer. The entire calculation of time dilation depends on relative motion.

 

[ghwellsjr]

The best way I know to understand Time Dilation is to look at the geometry of the spacetime diagrams for a couple of Inertial Reference Frames (IRFs) depicting the same situation and using the Lorentz Transformation process to get from one IRF to the other. The situation we will consider is a clock that is stationary in the first IRF. The spacetime diagram is simply a plot of the position (or distance from the spatial origin) of the clock along the horizontal axis versus time along the vertical axis. Here is the first diagram:

Pretty boring, isn't it? It shows that as time progresses from 0 seconds to 10 seconds, the clock stays at the spatial origin with the coordinate at 0. I also show each second of time as a blue dot.

Now we use the Lorentz Transformation to see how an IRF moving to the left at 60% of the speed of light would depict this same situation:

In this IRF, the clock is moving to the right at 0.6c. You can see that because at the Coordinate Time of 10 seconds, the blue line is at the Coordinate Distance of 6 light-seconds. You can also see that what took 10 seconds in the first IRF takes 12.5 seconds in this IRF.

Things take longer when they are moving in an IRF. And this is the simplest explanation of Time Dilation that I know of based on Special Relativity. Does it seem simple to you? If not, please let me know where you need some more explanation.

 

[russ_watters]

But time dilation is a real phenomenon which has been tested. I might not experience time dilation, but I know time dilates for the moving object if I test it. How can it be relative when I know the result way before the relation is established between me and the moving object.

"relative" does not mean unknown or unpredictable.

 

[h_cat]

Time dilation can be explained outside of the framework of relativity. There is even a mechanical explanation. If you assume that all matter is made of some form of electro-magnetic fields which can only propagate at c than you see that any circular process would come to a standstill if the corresponding system moves with c. Better said its clocks freeze.

ob_cat

 

[Mentz114]

Time dilation can be explained outside of the framework of relativity. There is even a mechanical explanation. If you assume that all matter is made of some form of electro-magnetic fields which can only propagate at c than you see that any circular process would come to a standstill if the corresponding system moves with c. Better said its clocks freeze.

Matter is not 'made of some form of electro-magnetic fields', so that balloon won't fly.

 

[Forcer]

Impulse is force by time. It's normal, if you give impulse to a particle also you give it time. Moreover, when a particle receives impulse, mass and time are increased in the same proportion.

 

[Forcer]

Can the time dilation be explained by any other theory other than relativity.

No, but if it is possible to improve the understanding of relativity and what it describes.

 

[h_cat]

Matter is not 'made of some form of electro-magnetic fields', so that balloon won't fly.

There are theories which explain matter this way. And that was the questions right? Those who have brains to think for them self can look into them and take their conclusions. I know of course that the standard model doesn't explain the structure of matter that way. In fact it doesn't explain it at all. So any theory which does should be welcomed to enriched our understanding of our particles structure. That doesn't mean that they are complete or without contradictions. But they exist and that is a truthful answer to the posters question, right?

vb_cat

 

[Mentz114]

There are theories which explain matter this way.

Where ? Can you give a reference ?

 

[krash661]

interesting.

 

[h_cat]

This is one of them, not very complete but interesting nevertheless. That said one has to look for themself there are a lot of weird theories out there some have a few good ideas. These are not my theories I only point out that there are theories which of course do not fit well into the standard model.
<<link deleted>> - the only one I can remember the link you need to google for more.

lc_cat

 

[phinds]

This is one of them, not very complete but interesting nevertheless. That said one has to look for themself there are a lot of weird theories out there some have a few good ideas. These are not my theories I only point out that there are theories which of course do not fit well into the standard model.
<<link deleted>> - the only one I can remember the link you need to google for more.

lc_cat

La-la-land blogs do not count as valid references on this forum.

 

[h_cat]

Somebody wanted some reference so that's the best I can do. But I got more and more the feeling I landed on the Spanish inquisition's forum. So I understand you right it is better to be quiet than two mention that there are theories out there which try two give answers.

ml_cat

 

[Nugatory]

So I understand you right it is better to be quiet than to mention that there are theories out there which try to give answers.

To quote the mission statement on the main physics forum landing page (emphasis mine):

Our mission is to provide a place for people (whether students, professional scientists, or others interested in science) to learn and discuss science as it is currently generally understood and practiced by the professional scientific community.

 

[phinds]

Somebody wanted some reference so that's the best I can do.

You agreed to the rules when you signed up and the rules include not posting unsupported speculation and not using unqualified references.

But I got more and more the feeling I landed on the Spanish inquisition's forum. So I understand you right it is better to be quiet than two mention that there are theories out there which try two give answers.

ml_cat

It is unfortunate that you feel that way, but this is a serious physics forum and if/when you make posts that do not follow the rules, you are likely to be called on it.

There ARE forums out there where you can post whatever you want, but this is not one of them because allowing that always ends up generating more heat than light.

 

[Mentz114]

Somebody wanted some reference so that's the best I can do. But I got more and more the feeling I landed on the Spanish inquisition's forum. So I understand you right it is better to be quiet than two mention that there are theories out there which try two give answers.

ml_cat

It's not unreasonable to ask for references. The one you gave is a collection of incorrect outdated theories or proto-theories. The last line of the article is

"The result is that all things in nature must experience a distortion of space and time that is relative to their absolute motion through space."
Absolute motion through space is a deprecated concept.


The correct answer regarding time dilation was given by Tiny-Tim in an early post.

 

[krash661]

There ARE forums out there where you can post whatever you want, but this is not one of them because allowing that always ends up generating more heat than light.

oh my...
about those forums.. so chaotic...

ahh, awesome, i just discovered this little window with symbols as i typed this response..
this is awesome, now i do not need a scientific key bored with this site..
awesome.

 

[Dale]

FYI. I would just like to remind everyone of the "report" feature. If you know that a post violates the forum rules then it really helps the mentors to report it and not respond (don't feed the trolls). We are trying to delete fewer posts from members in good standing, so using the report feature allows us to delete the offending post without deleting your responses.

 

[phinds]

FYI. I would just like to remind everyone of the "report" feature. If you know that a post violates the forum rules then it really helps the mentors to report it and not respond (don't feed the trolls). We are trying to delete fewer posts from members in good standing, so using the report feature allows us to delete the offending post without deleting your responses.

I've been accused in the past (correctly, probably) for being overly harsh with <expletive deleted>'s so I now sometimes go overboard trying to be understanding with them. Thanks for the reminder.

 

[phyti]

what is the exact mechanism by which time dilates for a fast moving object.
Can the time dilation be explained by any other theory other than relativity.

what is the exact mechanism by which time dilates for a fast moving object.
Can the time dilation be explained by any other theory other than relativity.

The mechanism:

The simplest example is the light clock, with photons oscillating vertically, between two mirrors. When the clock moves horizontally relative to the emission of the photon, the path between mirrors is extended, requiring more time, as viewed by someone who remains at the emission site. Since light interaction is common to all processes at the atomic/ molecular/biological level, the person moving with the clock is affected to the same degree, and therefore not aware his clock rate has changed.

Moving clocks:

Bill is launched into space, sets his course, and synchs his clock to Ann's, as he passes at a constant speed v. Ann views Bill's clock as running slower than her clock, while Bill views Ann's clock as running slower than his clock. After Bill decelerates to -v, Ann views Bill's clock as running faster than her clock, while Bill views Ann's clock as running faster than his clock. Since clocks are frequencies, Ann and Bill are only viewing a relativistic doppler shift, dependent on speed of convergence or divergence, and thus reciprocal. Time dilation for each (and subsequent aging) can only be determined with reunited clocks. The aging can be calculated easily using doppler info in a spacetime drawing, as georgewellsjr does so well, but that still requires selecting the returning clock. If Ann had launched into space later, at a speed greater than v, and Bill did not decelerate, she would have aged less at reunion.

Questions:

If time dilation is not real, i.e. if there is no actual changing rates, why do the clocks in the Hafele-Keating experiment record different times when compared after the trips?

Why is the surviving sample of high speed muons m greater than the lab sample n?
You can't use the irrelevant reverse point of view, because the sample sizes have the same ratio m/n in either frame!

 

[ghwellsjr]

Moving clocks:

Bill is launched into space, sets his course, and synchs his clock to Ann's, as he passes at a constant speed v. Ann views Bill's clock as running slower than her clock, while Bill views Ann's clock as running slower than his clock. After Bill decelerates to -v, Bill immediately views Ann's clock as running faster than his clock, while Ann doesn't view Bill's clock as running faster than her clock until a long time later. Since clocks are frequencies, Ann and Bill are only viewing a relativistic doppler shift, dependent on speed of convergence or divergence, and thus reciprocal after some possible period of light propagation time. Time dilation for each can be determined if we know their speeds in an IRF but subsequent aging can only be determined with reunited clocks. The aging can be calculated easily using doppler info in a spacetime drawing, as georgewellsjr does so well, but that still requires selecting the returning clock. If Ann had launched into space later, at a speed greater than v, and Bill did not decelerate, she would have aged less at reunion.

To be precise, I would make the above changes in bold.

Questions:

If time dilation is not real, i.e. if there is no actual changing rates, why do the clocks in the Hafele-Keating experiment record different times when compared after the trips?

It's not that Time Dilation is not real-it's that it is frame dependent which means that we cannot establish an absolute reality to it. Clocks can change their actual rates when they accelerate, it's just that we cannot say that a clock is Time Dilated after it accelerates and not before or vice versa unless we specify an IRF.

Let me illustrate with a couple spacetime diagrams based on a modification to the ones in post #10. Let's say in the first diagram that the clock started out traveling to the left at 0.6c and that at a time of 4 seconds, the clock changes to being at rest:

Now we will transform this scenario just like we did before and we get:

Now looking at these two diagrams which represent exactly the same scenario, we see that the clock is Time Dilated to begin with in the first diagram and ends up being Time Dilated in the second diagram.

We can even find an IRF in which there is no change in the clock's Time Dilation as a result of the same acceleration:

This IRF is moving at -0.333c with respect to the first one which results in the clock changing direction but maintaining the same speed before and after the acceleration.

There are even IRF's where the clock is Time Dilated before and after the acceleration to different degrees. We can never say what the Time Dilation of a clock is without specifying the IRF.

Why is the surviving sample of high speed muons m greater than the lab sample n?
You can't use the irrelevant reverse point of view, because the sample sizes have the same ratio m/n in either frame!

Because the muons are at high speed in the Earth frame and at rest in the lab. In the rest frame of the muons entering the Earth's atmosphere, they are not Time Dilated while the ones in the lab are.

 

[phyti]

To be precise, I would make the above changes in bold.


It's not that Time Dilation is not real-it's that it is frame dependent which means that we cannot establish an absolute reality to it. Clocks can change their actual rates when they accelerate, it's just that we cannot say that a clock is Time Dilated after it accelerates and not before or vice versa unless we specify an IRF.

Let me illustrate with a couple spacetime diagrams based on a modification to the ones in post #10. Let's say in the first diagram that the clock started out traveling to the left at 0.6c and that at a time of 4 seconds, the clock changes to being at rest:

Now we will transform this scenario just like we did before and we get:

Now looking at these two diagrams which represent exactly the same scenario, we see that the clock is Time Dilated to begin with in the first diagram and ends up being Time Dilated in the second diagram.

We can even find an IRF in which there is no change in the clock's Time Dilation as a result of the same acceleration:

This IRF is moving at -0.333c with respect to the first one which results in the clock changing direction but maintaining the same speed before and after the acceleration.

There are even IRF's where the clock is Time Dilated before and after the acceleration to different degrees. We can never say what the Time Dilation of a clock is without specifying the IRF.


Because the muons are at high speed in the Earth frame and at rest in the lab. In the rest frame of the muons entering the Earth's atmosphere, they are not Time Dilated while the ones in the lab are.

Technically you are correct about the bold edits, and a spacetime diagram would easily show the additional details. The statements were not intended to be exacting as 'engineering to the nth degree', or 'politically correct'. I could raise the same issue for st diagrams with instantaneous speed changes, which are unreal.
Since one viewer cannot measure his speed relative to light speed (in an absolute sense), we know we are measuring the difference in speed, and the difference in clock rate, and the difference in length contractions. This is not new, nor is it a revelation.
If two metal surfaces insulated from the ground and each other, are charged to 1000 volts and 1010 volts respectively, someone on the first measuring the second will get a reading of 10 volts. From the beginning of civilization, people have dealt with gradients or differences. Every measuring device from a ruler to an atomic clock uses standards that are defined and relative.
The issue here is not time dilation but the response implying there is no physical cause.
In the Hafele-Keating experiment, the clocks differed in accumulated time, and it wasn't because someone was looking at them. In the muon experiment, the larger fraction of survivors for the high speed particles was not because someone was looking at them. Viewing from the fast muon frame does not alter the percentage of survivors in the lab particles, i.e. you can't change the qty of particles in a sample by looking at it from a different reference point. The differences are real between objects compared together, therefore there are explanations in terms of physical processes. If time dilation cannot be explained in terms of fundamental physical processes, then there is no understanding. It's like pressing buttons on a TV, without knowing how the picture gets there! The coordinate transformations don't explain anything, they just provide a means of calculation from one frame to another.

 

[Mentz114]

If time dilation cannot be explained in terms of fundamental physical processes, then there is no understanding.

I hope you are not confusing time dilation, the coordinate effect, with differential ageing, which is coordinate independent. The examples you give are based on proper times, and so confirm differential aging, not time dilation.

The problem with ascribing a physical change to a coordinate dependent quantity is that it immediately leads to a contradiction or paradox.

 

[ghwellsjr]

The issue here is not time dilation but the response implying there is no physical cause.
In the Hafele-Keating experiment, the clocks differed in accumulated time, and it wasn't because someone was looking at them. In the muon experiment, the larger fraction of survivors for the high speed particles was not because someone was looking at them. Viewing from the fast muon frame does not alter the percentage of survivors in the lab particles, i.e. you can't change the qty of particles in a sample by looking at it from a different reference point. The differences are real between objects compared together, therefore there are explanations in terms of physical processes. If time dilation cannot be explained in terms of fundamental physical processes, then there is no understanding. It's like pressing buttons on a TV, without knowing how the picture gets there! The coordinate transformations don't explain anything, they just provide a means of calculation from one frame to another.

As Mentz alluded to, Time Dilation does not have a physical cause but Differential Aging does and it is the Lorentz Transformation that provides that mechanism, not as applied to the coordinates of events in different frames but rather as it is applied to the laws of physics. Prior to Einstein, Lorentz and other scientists assumed that there was an absolute rest state in which light propagated at c and in which clocks and rulers were correct. They assumed that our clocks and rulers were incorrect and were physically distorted by moving through the ether and so they looked for an explanation. Einstein, on the other hand, determined that the same Transformation that Lorentz had figured out as applied to the laws of optics needed to be applied to every law of physics and so all the laws were modified to make them invariant under a Lorentz Transformation and that provides all the mechanism or physical explanation for differential aging and all the other observables that are the result of the Principle of Relativity.