Is Time Relative? The Twin Experiment and Its Implications

In summary, time is relative and changes with velocity and gravity according to Einstein's theory of relativity. The thought experiment of the twin paradox, where one twin stays on Earth while the other travels at a high velocity for 5 years and returns to find a significant difference in their ages, has been extensively tested and applied in practical applications such as the Global Positioning System. There have been numerous experiments and applications that confirm both parts of relativity. However, it is difficult to conduct a direct experiment to test time dilation on Earth due to the effects of both gravity and velocity. The correction of GPS signals is necessary due to the effects of general relativity, while the twin paradox comes from special relativity. The mechanism of timekeeping devices,
  • #36
mangaroosh said:
Just to put this in context of physics, or at least to attempt to, I will have to ask the question, as to whether or not the existence of time [as a real force/entity/etc.] is relevant to physics?
Yes, the existence of time is relevant to physics and as far as physics is concerned, time exists. The theories and their equations are based on this and they work. That's enough for physics.

What you are asking* is a different question because what you are asking has no bearing whatsoever on the theories of physics or the outcomes of experiments. Therefore, what you are asking is not physics.

*What you are asking is, essentially, 'could the correctness of physics' treatment of time just be one big coincidence?'
Also, to suggest that entirely new theories of physics need to be developed is not a non sequitor, as it is not suggested that the measurement that is time (as opposed to the measurement of time) be done away with. The measurement can remain, so the results can remain the same. What would be required however, is the assumption about the nature of time, that is inherent in the theory. It simply needs to be viewed differently.
Well if that can be turned into a theory, then it'll become physics. But for right now all you really have here is idle speculation about the possibility that a theory can be constructed that deals with time differently and makes new predictions not already covered by existing experiments and yet also doesn't conflict with existing experimental data.

I don't think you quite grasp how vast of a task it would be to rewrite all of the past 100 years of physics. Nor does it seem you understand the "if it ain't broke don't fix it" principle. Regardless: Idle speculation isn't physics either.
Also, the other suggestion that because the theory has enjoyed success in its predictions, therefore the assumptions upon which it is based is correct, again, does not follow logically, as there is circular reasoning apparent within the assumption with regard to time.
Call it what you want, but making correct predictions is all that is asked of a theory. Since the theories work, there is no reason to be concerned that the starting assumptions are wrong. Again, all you have here is a vague displeasure with the starting assumption but absolutely nothing of substance on which to base a challenge to it.
With regard to the atomic clock, am I right in saying that "time" is measured based on the microwave emissions of changing electrons? Or something relatively similar? If so, why can this be said to be a measurement of the entity known as "time"?
How many times are you going to ask the same question and ignore the answer?

Again, again, again, again, again, and again for the last time before the thread is locked:
Atomic clocks are not the only "clocks" we have that are capable of detecing time dilation. Therefore, you can't just assume that a cesium clock is measuring a clock error due to motion or gravity unless you assume that several other clocks that work on completely different operating principles just happen by coincidence to have the same error.
 
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  • #37
"His (Einsein's) grades were also not the best when he was younger."

Not true at all - his childhood grades were quite good.
 
  • #38
mangaroosh said:
Time is assumed to exist and is measured using a clock. However, what it is that a clock actually measures is what is in question.

Proper time is a mathematical quantity that behaves a certain way in the theory of special relativity. Ideal clocks are postulated (ie. defined) to read proper time. There is no a priori guarantee that ideal clocks exist. However, we have been able to construct clocks whose readings appear to behave as proper time is supposed to behave in the theory. Such clocks are therefore considered extremely good approximate realizations of the theoretical ideal clock.
 
  • #39
BTW, your question actually has some substance, but this circular reasoning is actually how physics is done:

How do we know there's an electric field there?
From the way a charge behaves there.
How do we know that's a charge?
From the way it behaves in an electric field.
 
  • #40
atyy said:
BTW, your question actually has some substance, but this circular reasoning is actually how physics is done:

How do we know there's an electric field there?
From the way a charge behaves there.
How do we know that's a charge?
From the way it behaves in an electric field.

This is not 'circular reasoning' or any other 'reasoning'. This are just related definitions. We observe a set of objects which behave differently in different situations. We call these objects "electric charges" and describe the situation by an "electric field".
 
  • #41
mangaroosh said:
Just to put this in context of physics, or at least to attempt to, I will have to ask the question, as to whether or not the existence of time [as a real force/entity/etc.] is relevant to physics? I could quite easily be wrong, but I would have thought it would be pretty relevant. It could be a misinterpretation but from what I understood time was bundled together with space to form something quite real, measureable and existant. If this is incorrect, then perhaps the issue has no relevance, however if it is the case, and spacetime supposedly makes up part of "the fabric of reality", to the extent that perhaps, at some point in the future, it could be torn in order to create such things as wormholes, then the issue I feel has real and direct relevance.

I will try to steer clear of fallacious, ad hom arguments, as much as possible, as they have little relevance to the question being raised. Also, to suggest that entirely new theories of physics need to be developed is not a non sequitor, as it is not suggested that the measurement that is time (as opposed to the measurement of time) be done away with. The measurement can remain, so the results can remain the same. What would be required however, is the assumption about the nature of time, that is inherent in the theory. It simply needs to be viewed differently.

Also, the other suggestion that because the theory has enjoyed success in its predictions, therefore the assumptions upon which it is based is correct, again, does not follow logically, as there is circular reasoning apparent within the assumption with regard to time. Time is assumed to exist and is measured using a clock. However, what it is that a clock actually measures is what is in question.

But to try and simplify the question, because in part, may lack of scientific training is probably a barrier to communication here, but here goes:

With regard to the atomic clock, am I right in saying that "time" is measured based on the microwave emissions of changing electrons? Or something relatively similar? If so, why can this be said to be a measurement of the entity known as "time"?

A clock is to time as a measuring rod is to space. They both have to satisfy certain conditions to serve their purpose. Spatial measurement raises philosophical difficulties too. But if it works, use it. If you can find out how it works, so much the better. I don't know how a car works, but it gets me places.

Matheinste.
 
  • #42
mangaroosh said:
spacetime supposedly makes up part of "the fabric of reality"
Again, you still haven't defined what you mean by "the fabric of reality". What experiment could one perform to determine if something is part of "the fabric of reality" or not?
mangaroosh said:
What would be required however, is the assumption about the nature of time, that is inherent in the theory. It simply needs to be viewed differently.
Again, why does it need to be viewed differently? You have yet to provide any scientific motivation for viewing it differently. You have yet to identify any observation which the current view fails to explain and which your proposed view explains.
mangaroosh said:
Also, the other suggestion that because the theory has enjoyed success in its predictions, therefore the assumptions upon which it is based is correct, again, does not follow logically
Yes, it does, that is the core of the scientific method.

The first step of the scientific method is developing a theory. A scientific theory consists of two key elements: a mathematical framework for performing calculations, and a way of relating those calculations to the measurable outcomes of experiments. In the course of making a scientific theory the scientist is allowed to make absolutely any weird assumptions that they want to make, all they have to do is provide the mathematical framework that embodies the assumptions and relate the results to experimental outcome.

The second step of the scientific method is designing an experiment to test a specific hypothesis. The hypothesis is the theory's prediction of the measured outcome for the specific experiment. A good experiment will be one that tests an outcome where the theory disagrees with previous theories.

The third step of the scientific method is performing the experiment and analyzing the data. If the data matches the predictions then the theory is said to be verified and if the data matches the predictions then the theory is said to be falsified. If the theory is verified then that lends credence to the theory, regardless of anyone's discomfort with the assumptions. If the theory is falsified then that leads us to reject the theory as formulated.

The final step of the scientific method is to report the results to the scientific community at large. The experiment should be repeated by other independent members of the scientific community to establish the experimental results. The cycle is repeated and the results (whether they verify or falsify the theory) are used to develop the next theory.

Science does not seek to provide a logical "proof" of the assumptions of a theory. Instead, experiment is the final arbiter as to the validity of the assumptions. If they lead to correct predictions then they are accepted, if not they are rejected.

I hope this brief outline of the scientific method helps you understand better. The point is that in science a theory can assume "time exists" (or "quarks" or "wavefunctions" or "pink elephants" or whatever) without any justification whatsoever. All that is needed is to use those assumptions to provide a mathematical framework that can be used to predict the results of experiments. Contrary to your assertion above, the "success in its predictions" is the one and only criterion for determining the validity of the assumptions, a criterion which time-based theories have overwhelmingly met and which time-free theories have overwhelmingly failed.
 
  • #43
russ_watters said:
Yes, the existence of time is relevant to physics and as far as physics is concerned, time exists. The theories and their equations are based on this and they work. That's enough for physics.

What you are asking* is a different question because what you are asking has no bearing whatsoever on the theories of physics or the outcomes of experiments. Therefore, what you are asking is not physics.

*What you are asking is, essentially, 'could the correctness of physics' treatment of time just be one big coincidence?' Well if that can be turned into a theory, then it'll become physics. But for right now all you really have here is idle speculation about the possibility that a theory can be constructed that deals with time differently and makes new predictions not already covered by existing experiments and yet also doesn't conflict with existing experimental data.

I don't think you quite grasp how vast of a task it would be to rewrite all of the past 100 years of physics. Nor does it seem you understand the "if it ain't broke don't fix it" principle. Regardless: Idle speculation isn't physics either. Call it what you want, but making correct predictions is all that is asked of a theory. Since the theories work, there is no reason to be concerned that the starting assumptions are wrong. Again, all you have here is a vague displeasure with the starting assumption but absolutely nothing of substance on which to base a challenge to it. How many times are you going to ask the same question and ignore the answer?

Again, again, again, again, again, and again for the last time before the thread is locked:

I will ignore the above for the time being, but will return to it if absolutely necessary. The reason being that I think the below goes more to the crux of the issue.

russ_watters said:
Atomic clocks are not the only "clocks" we have that are capable of detecing time dilation. Therefore, you can't just assume that a cesium clock is measuring a clock error due to motion or gravity unless you assume that several other clocks that work on completely different operating principles just happen by coincidence to have the same error.

The assumption that is inherent with the above, is that:
all "clocks" measure the external force of time.

However, this is the assumption that needs to be examined. It is therefore erroneous to use the evidence of time dilation as evidence for the existence of time, because what it is that those clocks actually measure, is what is in question.

As I have said, a clock, regardless of whether it is a wristwatch, an atomic clock, a muon clock, a cesium clock, or whatever else, does not actually measure the external force of time (or the entity that is time, or however time is classified).

Instead what it measured, is the change of an object relative to itself, or rather its past state. This change is then taken as a unit of measurement, against which other things are compared.

It is no problem to take this unit of measurement and give it the name "time", however, to assert that it measures an external force is illogical, it's a non sequitor.
 
  • #44
matheinste said:
A clock is to time as a measuring rod is to space. They both have to satisfy certain conditions to serve their purpose. Spatial measurement raises philosophical difficulties too. But if it works, use it. If you can find out how it works, so much the better. I don't know how a car works, but it gets me places.

Matheinste.

I have no issue with the use of the measurement devices, however, there are certain things that follow from the assumptions of the existence of time as a real, external (or even intrinsic) factor in reality, that are both philosophical and practical.

I simply believe that they should be classified correctly, so that whatever assumptions that flow from them are more correct. What the manifestation of these assumptions is, is perhaps beyond my scope, but regardless, the correct classification of various forces, entities etc. is I believe important, not only for philosophy but for the sciences as well. It may or may not pose more problems than it answers, however, to accept something or dismiss something on this basis is illogical.


I agree to a certain extent with idea of not understanding completely how a car works, but the fact that it functions then so be it - I operate on a similar basic assumption. However, even cars need to be examined, and there are people who know exactly how they work. Indeed there are very real implications with understanding how a car works, not least the environmental issues. So it is important for those who work on cars, and who work on basic assumptions about cars, know the "ins and outs" of a car to a very high level, otherwise the decisions they make, based on the assumptions they take for granted, could have very real implications. Perhaps only on a limited basis, but also perhaps on a much wider level for society.

With regard to the issue of time, it is something which affects all of mankind, and so something which all of mankind is open to questioning. The fundamental assumption of the existence of time has very a real psychological bearing on the psyche of mankind, and so it is something that is open to examination, by anyone. It ultimately boils down to a persons examination of reality. This, to a large extent, manifests itself in the form of scientific investigation, but it also manifests in the form of philosophical enquiry. It is merely prudent to apply a certain level of philosophical inquiry in conjunction with scientific investigation.
 
  • #45
mangaroosh said:
As I have said, a clock, regardless of whether it is a wristwatch, an atomic clock, a muon clock, a cesium clock, or whatever else, does not actually measure the external force of time (or the entity that is time, or however time is classified).

Instead what it measured, is the change of an object relative to itself, or rather its past state. This change is then taken as a unit of measurement, against which other things are compared.
We're done here. You are not obligated to accept reality, but we are not obligated to indulge this crackpottery either.

But hey, when you've rewritten the last 100 years of physics in a way that incorporates this assertion of yours and have it published, by all means come back and we'll discuss this idea.

Thread locked.
 

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