Are time dilation experiments conclusive?

[Boro Petrovic]

Before posting reply, please think about time as a concept that is used to describe a change relative to some other change. For example, a traveler will arrive on a destination after Earth completes x rotations. At the beginning, people used Earth rotation as a reference change and called it a "day". Today we use change processes on a mechanical clock or on atomic clock as a reference change . The main point here is that it is all about change.

Theory of relativity postulates that internal changes in an object are slowed down when that object moves very fast. For example, If one twin leaves the earth, travels very high speed then returns to the Earth and finds that his twin aged 50 years more than he did then that means that all changes in his body (cells life cycles, electrons traveling through neurons, brain synapses building, etc) were slower compared to the changes in his twins body. One of the experiments that was used to prove it was comparison of changes on an atomic clock that orbits the Earth with same kind of changes on an atomic clock that is on the earth.

Since our ability to observe changes on the subatomic level is very limited, what are the chances that some other factors caused the difference in between observed changes on the atomic clock on the Earth compared to observed changes on the atomic clock that was orbiting earth?
Is this experiment sufficient to conclude that all subatomic changes , including the atom spin and subatomic particles movements , are slowed down compared to the changes in the atom that moves with slower speed.

Are time dilation experiments so far sufficient to allow general application on a complex system such as a living organism?

 

[phinds]

Theory of relativity postulates that internal changes in an object are slowed down when that object moves very fast.

It absolutely does NOT say that. It says that if an object is moving relative to you, then it APPEARS to you that its time is slowed down, and to it as if your time is slowed down. Both of your clocks, however, continue to tick away at one second per second (and yes, they are the SAME amount of "second").

One of the experiments that was used to prove it was a comparison of changes on an atomic clock that orbits the Earth with same kind of changes on an atomic clock that is on the earth.

No, that just proves that the AMOUNT of time is different for different paths through space-time, not that time passes at different rates for different objects.

Are time dilation experiments so far sufficient to allow general application on a complex system such as a living organism?

Complexity has nothing to do with it, only relative motion and our measurement ability are relevant, and no, we do not have sufficiently good measurement techniques to measure that small an amount of time dilation.

EDIT: and by the way, this is a common misconception because popular science presentations do a rather poor job of explaining time dilation (and often just flat get it wrong and say what you said).

 

[Boro Petrovic]

It seems to me that you are not thinking about time as a concept that describes change. For example, aging of our bodies is a cumulative result of extremely large series of change events in our bodies. If you can imagine two twins aged differently then that MUST mean that changes in one twins body were slower COMPARED to changes in other twins body. The twin who aged less obviously did not EXPERIENCE any slow down because all changes in his body , including his brain synapses connections that happen as result of his thinking, were slower compared to changes in his twins body.

 

[phinds]

It seems to me that you are not thinking about time as a concept that describes change. For example, aging of our bodies is a cumulative result of extremely large series of change events in our bodies. If you can imagine two twins aged differently then that MUST mean that changes in one twins body were slower COMPARED to changes in other twins body. The twin who aged less obviously did not EXPERIENCE any slow down because all changes in his body , including his brain synapses connections that happen as result of his thinking, were slower compared to changes in his twins body.

No, YOU are not understanding how the universe works. It is very un-intuitive, but it is the way it is. Clocks tick at the identical one second per second and biological processes run at the identical rates, regardless of your motion relative to someone else.

Just think about this. You, right now as you read this, are moving at .99999999c relative to a particle at CERN and according to that particle you are MASSIVELY time dilated. Do you feel slowed down? You are ALSO moving at ..5c relative to another frame of reference, so in THAT frame of reference you are only slightly time dilated. Can you be both at the same time?

As I told you in my original answer, the AMOUNT of time is different for different paths through space time.

 

[russ_watters]

Since our ability to observe changes on the subatomic level is very limited, what are the chances that some other factors caused the difference in between observed changes on the atomic clock on the Earth compared to observed changes on the atomic clock that was orbiting earth?
Is this experiment sufficient to conclude that all subatomic changes , including the atom spin and subatomic particles movements , are slowed down compared to the changes in the atom that moves with slower speed.

We have clearly not observed time dilation in all known physical processes. But look at the issue from the opposite direction: of the several processes that have shown time dilation, none of them have any known mechanism by which speed could affect the rate of the processes (indeed, the ancient principle of relativity forbids it). So there is nothing that would imply anything but the amount of time passed was different for the traveling twin. So yes, the known evidence is quite sufficient.

 

[pervect]

The FAQ gives a number of papers on the topic, one of which, being a review paper, would be an ideal place to start looking at the literature. http://www.worldscientific.com/doi/abs/10.1142/S0217732305017202, Gwinner, "EXPERIMENTAL TESTS OF TIME DILATION IN SPECIAL RELATIVITY". Unfortunately it's paywalled, so if you want the full details rather than an off-the-cuff opinion you'll have to arrange access through your local library.

I did find results of another paper by the same author via google, searching for "heavy ion storage ring tests of time dilation", which was mentioned as the most precise test to date. The successful google hit had the full text of the article, and was at iopscience. How much longer it'll be up I can't say. Reading the full text, I can basically say that the modern experiment was a more accurate update of the Ives-Stillwell experiment (which you'll find numerous references to on wiki and in the litertaure), and that the conclusion was that the experimental results matched the predictions of SR at a level of accuracy considerably better than 1 part per million, when compared to the class of non-relativistic "test theories" that were considered.

So the very short answer is yes, it has been tested.

 

[russ_watters]

No, YOU are not understanding how the universe works. It is very un-intuitive, but it is the way it is...

Phinds, the OP appears to understand how the theory works (what the theory says), but is asking about how we know the evidence couldn't support another conclusion. Just saying 'that's the way it is, accept it' does not answer the question.

 

[Boro Petrovic]

We have clearly not observed time dilation in all known physical processes. But look at the issue from the opposite direction: of the several processes that have shown time dilation, none of them have any known mechanism by which speed could affect the rate of the processes (indeed, the ancient principle of relativity forbids it). So there is nothing that would imply anything but the amount of time passed was different for the traveling twin. So yes, the known evidence is quite sufficient.

Thank you for your reply. I assume that by "Amount of time passed was different" you meant that "amount of events that happened was different". That implies that rate of the processes were different. Right?

 

[Bandersnatch]

I think I'd disagree with phinds' assertion in post #2 and #4 on the basis that it might be confusing time dilation (which is a symmetrical, observer-dependent effect) with differential ageing (which is what the OP is talking about).

Relativity predicts that observers in motion w/r to each other will see each other's clocks to move slower. A clock is understood as the rate of change of some physical process (relativity predicts all processes to be affected).
This observation is symmetrical. Each observer sees their own clocks to run just fine.

However, if one of the travellers gets back and meets the other one, the path through the space-time they will have traveled will be different, and one will be older than the other (accrued more time passage).

Similarly, an observer deeper in a gravity well will see clocks of an observer sent higher up to run at a different rate, and should they ever meet again their age would differ.

 

[Dale]

Closed pending cleanup.

EDIT: reopened, and merged with the previous thread. Some posts have been modified or deleted to make it consistent.

 

[Dale]

Theory of relativity postulates that internal changes in an object are slowed down when that object moves very fast.

That is not a postulate of relativity. It is a derived conclusion.

One of the experiments that was used to prove it was comparison of changes on an atomic clock that orbits the Earth with same kind of changes on an atomic clock that is on the earth.

Since our ability to observe changes on the subatomic level is very limited, what are the chances that some other factors caused the difference in between observed changes on the atomic clock on the Earth compared to observed changes on the atomic clock that was orbiting earth?

Such as what "other factor"? How do you propose that such other factors should conspire to produce exactly the time dilation predicted by relativity and not some other number. It is not enough for the other factors to affect the clock, but they must do so in exactly the correct way as to produce a "false positive".

Is this experiment sufficient to conclude that all subatomic changes , including the atom spin and subatomic particles movements , are slowed down compared to the changes in the atom that moves with slower speed.

No single experiment, in isolation, is sufficient to make much of a strong conclusion about anything. Reproducibility under different conditions is critical. The one you mention is called the Hafele-Keating experiment. By itself, no, it is not sufficient, but in conjunction with all of the other tests the preponderance of evidence is overwhelming.

Here is a review with a good list of experiments regarding SR:
http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html

Are time dilation experiments so far sufficient to allow general application on a complex system such as a living organism?

Yes. Living organisms are based on the EM force and the strong and weak nuclear forces. Time dilation has been proven for all three.

 

[russ_watters]

I assume that by "Amount of time passed was different" you meant that "amount of events that happened was different".

Yes.

That implies that rate of the processes were different. Right?

When compared across frames (counting the events in one frame against the elapsed time in another frame), yes.

 

[phinds]

Phinds, the OP appears to understand how the theory works (what the theory says), but is asking about how we know the evidence couldn't support another conclusion. Just saying 'that's the way it is, accept it' does not answer the question.

Hm ... I didn't think my replies read that way, but if they did then I agree it was poorly stated. I was attempting to show him that time dilation is totally frame dependent and that all clocks tick at the same rate locally.

 

[phinds]

When compared across frames (counting the events in one frame against the elapsed time in another frame), yes.

Certainly no argument there but I think we are promoting confusion in the OP by not fully emphasizing that processes do not run slow locally even while they appear different from different frames.

 

[russ_watters]

Hm ... I didn't think my replies read that way...

[separate post]
Certainly no argument there but I think we are promoting confusion in the OP by not fully emphasizing that processes do not run slow locally even while they appear different from different frames.

It may take longer to get there by following the OP down the path he wants to go (we assume), but in my experience it tends to be more convincing if we follow the line of logic until it fails than to just take a short-cut to the end.

I was attempting to show him that time dilation is totally frame dependent and that all clocks tick at the same rate locally.

Yes, I think the OP is already aware of that.

 

[phinds]

It may take longer to get there by following the OP down the path he wants to go (we assume), but in my experience it tends to be more convincing if we follow the line of logic until it fails than to just take a short-cut to the end.

Fair enough.

 

[Markus Hanke]

It seems to me that you are not thinking about time as a concept that describes change.

It is worthwhile pointing out that in the context of physics, time is defined to be what clocks measure. Thinking of it in terms of "change" is misleading ( at best ) - you could have a system that is completely static and exhibits no change at all ( e.g. the rest frame of a free elementary particle in an otherwise completely empty region ), yet if you placed a clock into that frame it would still give you a non-zero reading.

 

[A.T.]

Are time dilation experiments so far sufficient to allow general application on a complex system such as a living organism?

No matter how complex you make your "clock", if it stays synchronized with a "simple" local clock in their common inertial rest frame, then they must have the same synchronization in any other frame, where they both move at the same speed. Otherwise you get paradoxes. So all "clocks" or processes must be affected by time dilation from movement in the same way.

 

[Markus Hanke]

I think we have gone way off track here. This thread is about time dilation and the fact that change is perceived to occur at different rates from different frames but locally it always has a rate of one second per second.

Indeed. Coming back to the original point, time dilation is something that is observed as a relationship between the readings on a clock; that can be a mechanical clock, but it could also be digital, or atomic, or a decaying particle. The point is that the dilation factor is the same in all cases, meaning time dilation has nothing to do with the mechanism of the clocks themselves, but everything with their relationship in space-time.

 

[phinds]

. The point is that the dilation factor is the same in all cases, meaning time dilation has nothing to do with the mechanism of the clocks themselves, but everything with their relationship in space-time.

I agree w/ the second part of this but don't understand what you mean by the first part "dilation factor is the same in all cases". Actually the dilation factor is DIFFERENT from the point of view of each object that is moving at different speeds than (i.e. relative to) other objects.

 

[Markus Hanke]

I agree w/ the second part of this but don't understand what you mean by the first part "dilation factor is the same in all cases". Actually the dilation factor is DIFFERENT from the point of view of each object that is moving at different speeds than (i.e. relative to) other objects.

Apologies for the confusion ! What I meant to say is that time dilation is the same no matter what type of clock is used - two mechanical clocks in separated frames will be dilated by the same factor as ( e.g. ) two atomic clocks in the same two separated frames. In other words, time dilation is independent from the mechanism of the clocks themselves.

Yes, I do understand that gravitational time dilation is of course not symmetric, unlike kinematic time dilation between inertial frames in flat space-time.

 

[phinds]

OK, I agree w/ all that. Thanks.

 

[Markus Hanke]

OK, I agree w/ all that. Thanks.

No, I should thank you, and all the rest of the regular contributors here - this forum is invaluable for an interested amateur like myself, who is wanting to test his existing understanding on matters of physics, and hopefully further it as I go along

 

[phinds]

I'm sure I'm just as much an amateur as you are, I just happen to have found the site a few years earlier and can now parrot some of the stuff stated by the folks here who actually DO know what they are talking about

 

[Markus Hanke]

I'm sure I'm just as much an amateur as you are, I just happen to have found the site a few years earlier and can now parrot some of the stuff stated by the folks here who actually DO know what they are talking about

Ha ha, ok Either which way, it is very helpful to me. I have spent the last few years moderating other amateur forums, but I have now gotten to the stage where the incessant bickering about old chestnuts like aether, relativity being wrong, electric universe, gravity being EM in nature etc etc just gets on my nerves - it was holding me back in my own journey of learning, so I am now moving my focus to more advanced forums such as this one. Here I am just another newbie at the bottom of ladder, but I find that every time I open and read a thread, I am actually learning something, and be it just another way to look at things I already know. Often I come across stuff ( mainly maths ) that I don't really understand, and that then gives me the impetus to either ask about it, or go and do my own research. The entire experience here is invaluable for anyone who really wants to learn more about how the universe works

 

[Bruce Williams]

First one must understand that an equation such as those in Relativity explains the result of a process, they do not and are not meant to explain a physical process. This is something that most people do not understand and try to use the equations to describe the process, which it does not. It's like the equations for thermodynamics. They can calculate the results of thermal processes, but they are not the chemical/nuclear reactions themselves. Those process require many more physical considerations to understand.

Since the 0.99999999 particle did not cause your clock to change but it did change its clock at the end of the experiment then the logical conclusion is there is something we do not understand that acts as a 0 reference for the two of us, causing the 0.999999 particle to undergo some fundamental physical process to change different from you.
If it was truly only relative speed then we would perceive the slowing down of the other particle and it would perceive our slowing down but when brought back together we would both have changed the same and would need to adjust relativity appropriately. (the two twins going in opposite directions and back thought experiment)
But all the experiments say that the change is "real and permanent" and only happens to the object that changed speed.
Take the cocks flown around the world. When brought back to their original location there was a difference in their time vs the "stationary" clocks time.

So, if time dilation is true we can determine an absolute 0 frame of reference. Send clocks out at relativistic speeds in all 6 cardinal directions and have them return at the same speed. If there are changes in the clocks then there must be a 0 reference for them to change against. If there is no change then there is no physical property working (has been disproved so many times!), or if the change is identical in all 6 then their 0 reference is the starting frame. If the clocks changes are different then the 0 reference frame is solved through relativistic time dilation calculations. And one must remember that the experiment must occur such that any local gravity effect is swamped out or calculated out.

Unfortunately this experiment would have to be conducted in an area with an extremely low gravitational field so it may be a while before it can be done.

 

[mfb]

Send clocks out at relativistic speeds in all 6 cardinal directions and have them return at the same speed.

They will all 6 show exactly the same result, but all deviate from a reference clock on Earth. You can do a sub-experiment on one of the spacecraft s, again sending 6 smaller spacecraft s in all directions. Same result: the clocks on the sub- spacecraft s will all agree with each other, but they will disagree with the reference clock on the mother spacecraft . There is no "0 reference".

There is no preferred reference frame, but acceleration (as yes/no question) is frame-independent - everyone will agree that the spacecraft s changed their speed, while the Earth did not.

 

[phinds]

Since the 0.99999999 particle did not cause your clock to change but it did change its clock at the end of the experiment then the logical conclusion is there is something we do not understand that acts as a 0 reference for the two of us, causing the 0.999999 particle to undergo some fundamental physical process to change different from you.

No, not at all. It just traveled through a different space-time path and therefore has seen a different amount of time passage. This is a completely common misperception.

 

[Nugatory]

Since the 0.99999999 particle did not cause your clock to change but it did change its clock at the end of the experiment then the logical conclusion is there is something we do not understand that acts as a 0 reference for the two of us, causing the 0.999999 particle to undergo some fundamental physical process to change different from you.

There's nothing that we don't understand here - the two travelers took different paths through spacetime so covered a different amount of time.

It's no more mysterious than when two drivers in two cars zero their trip odometers before they leave yet find different numbers on their odometers when they arrive at their common destination - they took different routes through space, they covered a different distance in space.

 

[A.T.]

if the change is identical in all 6 then their 0 reference is the starting frame

The change is identical for any inertial starting frame, so your "0 reference" is just another word for "inertial frame"?

 

[harrylin]

First one must understand that an equation such as those in Relativity explains the result of a process, they do not and are not meant to explain a physical process. [..]

Yes indeed; this is also explained in the FAQ, you may want to have a look at it.
Consequently everyone has his/her own explanation as to the "why" (see also next).

But all the experiments say that the change is "real and permanent" and only happens to the object that changed speed. Take the cocks flown around the world. When brought back to their original location there was a difference in their time vs the "stationary" clocks time.

Well yes, only clocks that change their state of motion alter their count of elapsed time compared to clocks that do not change their state of motion (but not only compared to what you consider "stationary" clocks!).

So, if time dilation is true we can determine an absolute 0 frame of reference. [..]

Certainly not; but others already sufficiently clarified that. In a nutshell, the SR equations are based on the relativity principle, so that you cannot expect to find something else with those!

[..] It's no more mysterious than when two drivers in two cars zero their trip odometers before they leave yet find different numbers on their odometers when they arrive at their common destination - they took different routes through space, they covered a different distance in space.

In order to give that illustration physical content, can you please clarify what according to you the equivalence is with the ground that drives the odometers.

 

[Wuberdall]

It is worthwhile pointing out that in the context of physics, time is defined to be what clocks measure. Thinking of it in terms of "change" is misleading ( at best ) - you could have a system that is completely static and exhibits no change at all ( e.g. the rest frame of a free elementary particle in an otherwise completely empty region ), yet if you placed a clock into that frame it would still give you a non-zero reading.

That is entirely depending up on your philosophical believes of time; realist, non-realist, etc.

You will be correct in a realist descriotion of time.. But wrong for a non-realist on time. And i think that Boro Petrovic tendency to talk and descripe time as physical change in a system, suggest that he either is a non-realist on time or do not regard it as fundamental but instead as a derived concept (but still real).

 

[phinds]

That is entirely depending up on your philosophical believes of time; realist, non-realist, etc.

No, as Markus pointed out, in terms of physics it's a DEFINITION, not an opinion. Physicists agree that this is what time is. This forum is not about philosophy.

 

[Wuberdall]

No, as Markus pointed out, in terms of physics it's a DEFINITION, not an opinion. Physicists agree that this is what time is. This forum is not about philosophy.

Yes, as it's for now (and it has far from always been so).. But it wil be worth mentioning that there are a large amount of work and articles beeing produced by physicist on these vary topics of the nature of time; is it Real?, is it fundamental or derived ?
So it is not entirely philosophical, but 'physical' to.

I, myself is a realist on time and completely do not care whether time is fundamental or not. So I completely agress with your previus post.
I only bring this up becouse Boro Petrovic sounds like he is of a different believe of the nature of time.

 

[phinds]

I only bring this up becouse Boro Petrovic sounds like he is of a different believe of the nature of time.

And does his point of view solve problems in physics and get the right answers?