Is the relativity of simultaneity more than just a fudge factor?

[mc Kravitz]

TL;DR Summary

Einstein came up with the idea of the relativity of simultaneity to resolve the many paradoxes of SR but is it's use arbitrary?

<Moderator’s note: a reference to an article published in a predatory journal has been removed. References on PF should be from the professional scientific literature or from other sources consistent with the professional scientific literature>

I read through many posting on various threads in this forum and others regarding the twin/triplet paradox. The conclusions supporting SR generally boil down to using the relativity of simultaneity to eliminate any paradoxes.
Basically any form of acceleration, change in direction etc. allows the use of the relativity of simultaneity to dismiss any further discussion of the topic and get back to discussing the important things about relativity like; why can't anyone detect dark matter, dark energy, or whatever else is needed to further glorify GR.
From much of what I read on the topic, it appears that Einstein himself spent years on resolving the paradoxes before coming up with the idea.

"After seven and more years of toil, Einstein made the breakthrough that brought him his special theory of relativity. Some five to six weeks were then needed to complete his famous 1905 paper, "On the Electrodynamics of Moving Bodies." The breakthrough was his recognition of the relativity of simultaneity: judgments of the simultaneity of events will vary according to the state of motion of the observer. As a reflection of its importance, Einstein later simply talked of the discovery as "The Step." " See: https://sites.pitt.edu/~jdnorton/Goodies/rel_of_sim/index.html

He did not present any formulas to calculate how time/clocks can appear to suddenly move forward or backward and how the acceleration function causes it. He merely postulated it. You do the calculations using the Lorentz transforms and if results in a paradox you are free to use the relativity of simultaneity to eliminate the paradoxes. It always assume that there is one observer who never undergoes any acceleration. and any accelerated observers clocks/age can be adjusted to eliminate any paradoxes.

Simple and easy steps but it just doesn't sound like physics. It sounds more like a recipe (add salt to obtain desired flavor).

 

[PeroK]

Summary:: Einstein came up with the idea of the relativity of simultaneity to resolve the many paradoxes of SR but is it's use arbitrary?

This was all resolved well over 100 years ago. In its simplest formulation Special Relativity is Minkowski geometry. The question is not whether that geometry is self-consistent (it's only some geometry) but whether that geometry matches the local spacetime in our universe. Experiments show that it does.

 

[FactChecker]

Summary:: Einstein came up with the idea of the relativity of simultaneity to resolve the many paradoxes of SR but is it's use arbitrary?

I read through many posting on various threads in this forum and others regarding the twin/triplet paradox. The conclusions supporting SR generally boil down to using the relativity of simultaneity to eliminate any paradoxes.
Basically any form of acceleration, change in direction etc. allows the use of the relativity of simultaneity to dismiss any further discussion of the topic

IMO, the relativity of simultaneity is the quickest and easiest way to point out the flaw in most paradoxes. It is most often overlooked.

He did not present any formulas to calculate how time/clocks can appear to suddenly move forward or backward and how the acceleration function causes it. He merely postulated it. You do the calculations using the Lorentz transforms and if results in a paradox you are free to use the relativity of simultaneity to eliminate the paradoxes.

The Lorentz transformations are the mathematics of the geometry of SR space-time, including the relativity of simultaneity.

It always assume that there is one observer who never undergoes any acceleration. and any accelerated observers clocks/age can be adjusted to eliminate any paradoxes.

Relativity of simultaneity is not just useful to point out flaws in paradoxes related to accelerating frames. It is a flaw of most (all?) paradoxes between two relatively moving inertial reference frames. So it is very basic.

Simple and easy steps but it just doesn't sound like physics. It sounds more like a recipe (add salt to obtain desired flavor).

To me, the relativity of simultaneity follows directly from the experimental verification that the speed of light is the same in any non-accelerating inertial reference frame.

 

[Ibix]

He did not present any formulas to calculate how time/clocks can appear to suddenly move forward or backward and how the acceleration function causes it.

Why would he? Clocks never do appear to suddenly move forward or backward. The "sudden jumps" are changes of interpretation, and the formulae to calculate them are simple applications of the Lorentz transforms. And acceleration doesn't cause clocks to do anything - it just changes your inertial rest frame, so if you want to work in your current inertial rest frame then you need to deal with the changes of your interpretation of your data. That's all.

 

[Ibix]

You do the calculations using the Lorentz transforms and if results in a paradox you are free to use the relativity of simultaneity to eliminate the paradoxes.

This is an utterly bizarre thing to say. If you use the Lorentz transforms correctly, you don't get paradoxes - that's the whole point. The so-called paradoxes in relativity arise when people try to duck using the full Lorentz transforms and do things like apply the time dilation equation (a special case of the Lorentz transforms) to more general cases where they are not applicable.

 

[Orodruin]

IMO, the relativity of simultaneity is the quickest and easiest way to point out the flaw in most paradoxes. It is most often overlooked.

I’d even say that not understanding that simultaneity is relative is the foundation of most - if not all - SR ”paradoxes”. If it is taken into account properly from the beginning there usually is no paradox.

Summary:: Einstein came up with the idea of the relativity of simultaneity to resolve the many paradoxes of SR but is it's use arbitrary?

He did not present any formulas to calculate how time/clocks can appear to suddenly move forward or backward and how the acceleration function causes it.

Nothing appears to ”jump” in time. It is just a change of coordinates on spacetime. Being surprised about it is about the same as being surprised the x-coordinate is discontinuous if you make a sudden finite rotation in Euclidean space.

 

[mc Kravitz]

Factchecker wrote "To me, the relativity of simultaneity follows directly from the experimental verification that the speed of light is the same in any non-accelerating inertial reference frame."

That explains why it took Einstein several years to come up with the idea.

Thanks for your insight.

ibix wrote: "And acceleration doesn't cause clocks to do anything - it just changes your inertial rest frame, so if you want to work in your current inertial rest frame then you need to deal with the changes of your interpretation of your data. That's all."

So when my twin comes back from a long journey and looks much younger than me, I can explain it by a mis -interpterion of the data that I never collected.

Thanks for your insight.

[COLOR=rgb(0, 0, 0)]Orodruin[/COLOR] wrote:

IMO, the relativity of simultaneity is the quickest and easiest way to point out the flaw in most paradoxes. It is most often overlooked.

"I’d even say that not understanding that simultaneity is relative is the foundation of most - if not all - SR ”paradoxes”. If it is taken into account properly from the beginning there usually is no paradox."

I get it. If you add enough salt to start you won't have to add any later.

Thanks for the insight.

If this forum was around back in 1905 it could have saved Einstein several years of hard work.

Thank all of you for the incredibly clear and un ambiguous insights.

 

[Ibix]

So when my twin comes back from a long journey and looks much younger than me, I can explain it by a mis -interpterion of the data that I never collected.

That's not what I said. You are mixing up the relativity of simultaneity (which is what you said you were talking about and what I was talking about) and differential aging (which is what you are actually talking about and which has nothing to do with the relativity of simultaneity).

May I suggest that it would be better to actually learn a theory before attempting to criticize it?

 

[Orodruin]

So when my twin comes back from a long journey and looks much younger than me, I can explain it by a mis -interpterion of the data that I never collected.

No. This is a misunderstanding of how the theory works on your part.

 

[Dale]

The thread is reopened for discussion. An unsuitable reference in a known predatory journal has been removed, as has the resulting (correct) criticism of said reference. Further criticism is unnecessary.

 

[Nugatory]

He merely postulated [the relativity of simultaneity]

On the contrary, it is a logical consequence of the invariant speed of light.

Let's say that I look up at the night sky and I see a star explode. When did the explosion happen? Not when I saw it, because it took a while for the light from the explosion to reach my eyes; if the nova was 100 light-years away and I see it today it happened 100 years ago because that's how long it took for the light to get from there to here... This is just the same common sense that tells us that if a plane lands after four hours in the air, it must have taken off four hours ago.

Now suppose that twenty years later I see another star go nova; this one is 120 light-years distant. Despite the great gap between my observations I will know that both exploded at the same time. Furthermore, anyone who is at rest relative to me will agree, even though their observations may happen at different times and in general will not be 20 years apart (for example, if they happen to be exactly equidistant from both stars they will see both explosions at the same time).

However, someone moving relative to me and applying the exact same logic (take the time the light reaches us, subtract the light travel time to find the time the event happened, use the invariant speed of light to determine that travel time) will find that these two explosions did not happen at the same time (don't take my word for it! try working an example for yourself! It will be easiest to see if we place ourselves exactly midway between the two stars and at rest relative to them).

That's relativity of simultaneity.

 

[Dale]

Summary:: Einstein came up with the idea of the relativity of simultaneity to resolve the many paradoxes of SR but is it's use arbitrary?

The conclusions supporting SR generally boil down to using the relativity of simultaneity to eliminate any paradoxes

So it seems like your objection is that the relativity of simultaneity resolves paradoxes. That seems like a good thing, not something objectionable

 

[Sagittarius A-Star]

Summary:: Einstein came up with the idea of the relativity of simultaneity to resolve the many paradoxes of SR but is it's use arbitrary?

You do the calculations using the Lorentz transforms and if results in a paradox you are free to use the relativity of simultaneity to eliminate the paradoxes.

The Lorentz transforms contain the term for relativity of simultaneity. So you would take it automatically into account.

It always assume that there is one observer who never undergoes any acceleration. and any accelerated observers clocks/age can be adjusted to eliminate any paradoxes.

Wolfgang Rindler argued, that the effect of a hypothetical unknown adjustment of the clock by an acceleration could be dwarfed, if you extend the inertial parts of the travel:

This 'time dilation', like length contraction, is no accident of convention but a real effect. Moving clocks really do go slow. If a standard clock is taken at uniform speed v through an inertial frame S along a straight line from point A to point B and back again to A, the elapsed time T0 indicated on the moving clock will be related to the elapsed time T indicated on the clock fixed at A by the Eq. (21) -- except for small unknown effects caused by the brief accelerations needed to initiate, reverse, and terminate, the journey. What happens to a clock during acceleration depends on the mechanism of the clock, whereas what happens during periods of uniform motion is totally mechanism-independent, as we saw in deriving Eq. (21). However, no matter what the effect of the three accelerations might be, it would be the same for long as for short journeys, and so it can be dwarfed by simply extending the lengths of free fall. So, at least in theory, an astronaut undertaking such a journey -- and, of course, aging exactly in accordance with her clock on board -- could come back finding her stay-at-home twin to have aged more than she during their separation by a γ-factor (neglecting what might have happened to her own aging during lift-off, turn-around and landing.)

Source:
http://www.scholarpedia.org/article/Special_relativity:_kinematics#Special_relativistic_kinematics

It was shown experimentally by Bailey et al. (1977), that the acceleration has no direct effect on the time dilation:

Clock hypothesis - lack of effect of acceleration

The clock hypothesis states that the extent of acceleration does not influence the value of time dilation. In most of the former experiments mentioned above, the decaying particles were in an inertial frame, i.e. unaccelerated. However, in Bailey et al. (1977) the particles were subject to a transverse acceleration of up to ∼10^18 g. Since the result was the same, it was shown that acceleration has no impact on time dilation.[27]

In addition, Roos et al. (1980) measured the decay of Sigma baryons, which were subject to a longitudinal acceleration between 0.5 and 5.0 × 10^15 g. Again, no deviation from ordinary time dilation was measured.[29]

Source:
https://en.wikipedia.org/wiki/Exper...k_hypothesis_-_lack_of_effect_of_acceleration

As a reaction on similar objections, Einstein published in 1918 a description of the twin paradox in both reference frames. Source:
https://en.wikisource.org/wiki/Translation:Dialog_about_Objections_against_the_Theory_of_Relativity

 

[PeterDonis]

I read through many posting on various threads in this forum and others regarding the twin/triplet paradox. The conclusions supporting SR generally boil down to using the relativity of simultaneity to eliminate any paradoxes.

You don't give any specific references to other threads, so I have no way of knowing if your understanding of what was said in them is correct, but it doesn't seem like it. Twin paradox senarios are about differential aging, and differential aging can always be calculated without involving any simultaneity convention at all, let alone having to use relativity of simultaneity to "eliminate any paradoxes".

Basically any form of acceleration, change in direction etc. allows the use of the relativity of simultaneity to dismiss any further discussion of the topic and get back to discussing the important things about relativity like; why can't anyone detect dark matter, dark energy, or whatever else is needed to further glorify GR.

This is not a fair description of any valid method of analyzing scenarios in relativity. I strongly suspect you have not actually done any problem solving in relativity. Anyone who has done so would know better than to say such things.

From much of what I read on the topic, it appears that Einstein himself spent years on resolving the paradoxes before coming up with the idea.

"After seven and more years of toil, Einstein made the breakthrough that brought him his special theory of relativity. Some five to six weeks were then needed to complete his famous 1905 paper, "On the Electrodynamics of Moving Bodies." The breakthrough was his recognition of the relativity of simultaneity: judgments of the simultaneity of events will vary according to the state of motion of the observer. As a reflection of its importance, Einstein later simply talked of the discovery as "The Step." " See: https://sites.pitt.edu/~jdnorton/Goodies/rel_of_sim/index.html

This is about the history of how Einstein came up with SR; but that is actually irrelevant to how SR as it is understood today works or whether it is valid. The title question of this thread is not about the history of how Einstein came up with SR. It is about SR. That means you should not be looking at how Einstein came up with SR; you should be looking at our best modern understanding of SR. And you clearly are not.

He did not present any formulas to calculate how time/clocks can appear to suddenly move forward or backward and how the acceleration function causes it.

That's because no such things happen. You should not expect any theory to give you formulas for things that don't happen.

He merely postulated it.

As noted above, whatever Einstein did in coming up with SR is irrelevant. The question is, does SR, as a theory, postulate relativity of simultaneity? And the answer is, no, it doesn't. It is a logical consequence of the theory, not a postulate of it.

You do the calculations using the Lorentz transforms and if results in a paradox you are free to use the relativity of simultaneity to eliminate the paradoxes.

This, again, is not a fair description of any valid method of analyzing scenarios in relativity, and nobody who had actually solved problems using relativity would say such a thing. I think you need to spend some time actually learning relativity instead of criticizing it on the basis of your lack of knowledge.

It always assume that there is one observer who never undergoes any acceleration.

Wrong. SR can handle scenarios in which all observers undergo proper acceleration just fine.

any accelerated observers clocks/age can be adjusted to eliminate any paradoxes.

See my comments above about not being a fair description of analyzing scenarios in relativity.

Simple and easy steps but it just doesn't sound like physics. It sounds more like a recipe (add salt to obtain desired flavor).

I understand that the inaccurate straw man picture of relativity that you have in your head seems like this. But that picture has nothing to do with the actual theory of relativity.

 

[Vanadium 50]

But that picture has nothing to do with the actual theory of relativity.

Interesting that this message was posted about the same time another person with similar misunderstandings was vacationed. Almost... simultaniously.

 

[mc Kravitz]

Dale wrote: So it seems like your objection is that the relativity of simultaneity resolves paradoxes. That seems like a good thing, not something objectionable.

 

[mc Kravitz]

I must confess to all participants on this forum that I did not read the rules prior to posting. I am in communications with a moderator now making sure I fully understand the rules prior to any future postings.

Thank you all for your insights

 

[pervect]

The relativity of simultaneity is an important part of special relativity (SR), the theory won't work without it. It's also the part of SR which is most misunderstood. It's not a "fudge factor" by any means, it arises naturally from the mathematics, whether the mathematics is based on Einstein's original idea of the constancy of the speed of light, or the more modern notions of Lorentzian geometry.

A "fudge factor" generally involves "tweaking" adjustable parameters to make a theory work. There are no such "free parameters" in SR. It arises from small set of simple fundamental assumptions that don't involve "tunable" parameters.

I would suggest studying the mathematical formulation of SR more closely if this is not clear. Einstein's papers are of course the most historical, but may not be the easiest to learn from. I would personally recommend an approach based on Bondi's k-calculus, such as Bondi's book "Relativity and Common Sense". At a more advanced level, the geometrical approach in "Space-time physics" is also good to learn from, though I'd say Bondi's approach could be productively studied with a lower requirement on background mathematical knowledge. High school algebra should suffice for Bondi's approach.

[add]. I should also mention an approach which use no mathematics, such as "Relativity on Rotated Graph Paper", references of which can be found with a search of PF. While it does not require mathematics, it does require the ability to draw and interpret space-time diagrams.

 

[A.T.]

You do the calculations using the Lorentz transforms and if results in a paradox you are free to use the relativity of simultaneity to eliminate the paradoxes.

The Lorentz transforms contain the term for relativity of simultaneity. So you would take it automatically into account.

Exactly. Also visualized here:

 

[sysprog]

Exactly. Also visualized here:

I'm swiping this for the 8-year-old's thread (https://www.physicsforums.com/threa...irst-post-im-8years-old.1012042/#post-6596804).

 

[mc Kravitz]

Dale wrote: So it seems like your objection is that the relativity of simultaneity resolves paradoxes. That seems like a good thing, not something objectionable.

 

[A.T.]

Dale wrote: So it seems like your objection is that the relativity of simultaneity resolves paradoxes. That seems like a good thing, not something objectionable.

In other words: Failing to account for relativity of simultaneity is what creates the apparent paradoxes in the first place. If you use the full Lorentz transform right away, you don't get any paradoxes.