Poincare's relativity (split from essence of relativity)

[Strange]

The Principle of Relativity put forward by Henri Poincare is proven to be wrong by experiment! What's your view on this? What does it mean?

My view is that you should provide details of this experiment.

[imatfaal]

!

Moderator Note

 

Winds - your post is hidden until you can show that you have permission to publish an entire article or such a large chunk. The post made was far beyond academic fair use. PM member of staff if you do have permission (or if preprints are available on arxiv or similar). Thanks

 

[swansont]

I don't think any conclusion can be drawn from it (the Lu Shan paper)

 

First of all, the KE of the drop is set as the potential energy, which ignores the translational motion.

 

More egregiously, the speed of the wave is set to sqrt(2gh), with no justification for this whatsoever.

 

Also, there's no real explanation about what they are trying to show, and no experimental results are given.

[studiot]

It would be nice if someone could give us a quick summary of which of Poincare's works is referred to here as Poincare's Relativity.

 

Is it this paper?

 

H Poincare : Recueil de travaux offert par les auters a H A Lorenz : Serie2. Tome5 Arch Neerl 1900 p252

 

English paper title

 

Lorenz's Theory and Principle of Reaction.

[swansont]

It would be nice if someone could give us a quick summary of which of Poincare's works is referred to here as Poincare's Relativity.

 

Is it this paper?

 

H Poincare : Recueil de travaux offert par les auters a H A Lorenz : Serie2. Tome5 Arch Neerl 1900 p252

 

English paper title

 

Lorenz's Theory and Principle of Reaction.

 

 

I agree. Let's establish what's being discussed, and not drag works of a dubious nature into the conversation.

[winds]

Please refer to the paper of remarks (2) in the author's post, there is more details of his experiment.

My view is that you should provide details of this experiment.

Edited May 18, 2017 by winds

[swansont]

(Author's post in http://www.scienceforums.net/topic/103950-the-nature-of-time-and-the-essence-of-relativity/ as this has been split off)

[Country Boy]

If I remember correctly, Poincare postulated that a moving magnetic field would be stronger in the direction of motion so would cause atoms and molecule's to "contract" in that direction giving the Lorentz contraction. However, if you had a series of rods, with spaces in between, that would not cause the space in between to equally contract. Einstein's theory was that "space itself" contracted. Additional experiments, such as the "Kennedy- Thorndike experiment", http://www.conspiracyoflight.com/Kennedy/Kennedy.html, showed that Einstein, not Poincare, was correct.

[Tim88]

If I remember correctly, Poincare postulated that a moving magnetic field would be stronger in the direction of motion so would cause atoms and molecule's to "contract" in that direction giving the Lorentz contraction. However, if you had a series of rods, with spaces in between, that would not cause the space in between to equally contract. Einstein's theory was that "space itself" contracted. Additional experiments, such as the "Kennedy- Thorndike experiment", http://www.conspiracyoflight.com/Kennedy/Kennedy.html, showed that Einstein, not Poincare, was correct.

 

On this point I don't think that there was disagreement between Einstein and Poincare; can you please elaborate how you think that KTX was an issue for Poincare?

 

As far as I remember, Einstein never held that "space itself" contracted; that would even lead to self contradictions such as with Bell's Spaceship paradox (if one rejects Bell's explanation, as his colleagues first did), which is a variant on "a series of rods with space in-between".

Note that it's important to distinguish between contraction of lengths (which is an action, dynamic change), and lengths and distances that are measured to be shorter according to one system than according to another system (which is a difference). "Causing to contract" is dynamic, about things happening.

From the point of view of the launch platform's reference system, the rockets and the string contract while the rockets accelerate, but "space" does not contract - else the string should NOT break and magical, contradictory things would happen.Only objects can Lorentz contract, which is consistent with Maxwell's electrodynamics (indeed, that was a central issue in Bell's "How to teach relativity").

[Eise]

For what it is worth, if I remember correctly: there were no empirical differences between Poincaré and Einstein about relativity. But Poincaré still held to the idea that there was some 'real time', even if it was empirically impossible what the 'absolute time frame' was. Einsteins basic assumptions were less, and simpler.

[Tim88]

For what it is worth, if I remember correctly: there were no empirical differences between Poincaré and Einstein about relativity. [..]

 

Yes, I think that has to be correct, for the simple fact that Poincaré introduced the "Lorentz transformations", that is, the transformations of Lorentz written in the symmetrical form as we know them today. It's hard to see how any empirical difference between predictions can occur when one uses the same calculations for those predictions.

[VandD]

 

On this point I don't think that there was disagreement between Einstein and Poincare; can you please elaborate how you think that KTX was an issue for Poincare?

 

As far as I remember, Einstein never held that "space itself" contracted; that would even lead to self contradictions such as with Bell's Spaceship paradox (if one rejects Bell's explanation, as his colleagues first did), which is a variant on "a series of rods with space in-between".

Note that it's important to distinguish between contraction of lengths (which is an action, dynamic change), and lengths and distances that are measured to be shorter according to one system than according to another system (which is a difference). "Causing to contract" is dynamic, about things happening.

From the point of view of the launch platform's reference system, the rockets and the string contract while the rockets accelerate, but "space" does not contract - else the string should NOT break and magical, contradictory things would happen.Only objects can Lorentz contract, which is consistent with Maxwell's electrodynamics (indeed, that was a central issue in Bell's "How to teach relativity").

 

This doesn't make sense. Length contraction occurs because of relativity of simultaneity. Whether there is 'material' between the events or only empty space doesn't make any difference. For a space traveler the distance of empty space to a star gets shorter. Period.

[imatfaal]

 

This doesn't make sense. Length contraction occurs because of relativity of simultaneity. Whether there is 'material' between the events or only empty space doesn't make any difference. For a space traveler the distance of empty space to a star gets shorter. Period.

 

That makes sense to me - otherwise the famous muon detection on earth's surface would not work; we "see" time dilated for muons (hence they reach earth's surface during what would otherwise be their too brief lifespan) - the muons "see" distance contracted thus they can travel the otherwise too long journey in their brief lifespan)

[VandD]

 

On this point I don't think that there was disagreement between Einstein and Poincare; can you please elaborate how you think that KTX was an issue for Poincare?

 

As far as I remember, Einstein never held that "space itself" contracted; that would even lead to self contradictions such as with Bell's Spaceship paradox (if one rejects Bell's explanation, as his colleagues first did), which is a variant on "a series of rods with space in-between".

Note that it's important to distinguish between contraction of lengths (which is an action, dynamic change), and lengths and distances that are measured to be shorter according to one system than according to another system (which is a difference). "Causing to contract" is dynamic, about things happening.

From the point of view of the launch platform's reference system, the rockets and the string contract while the rockets accelerate, but "space" does not contract - else the string should NOT break and magical, contradictory things would happen.Only objects can Lorentz contract, which is consistent with Maxwell's electrodynamics (indeed, that was a central issue in Bell's "How to teach relativity").

 

 

 

This doesn't make sense. Length contraction occurs because of relativity of simultaneity. Whether there is 'material' between the events or only empty space doesn't make any difference. For a space traveler the distance of empty space to a star gets shorter. Period.

 

Tim,

 

to help you understand special relativity and Bell's paradox:

 

In Bell's spaceship paradox it's a given to keep distance (length) constant between the rockets in launch platform frame. Then wonder what happens to the rope. It breaks. Why?

 

Let's start the easy way.

If the rockets would accellerate in such a way that in their common reference frame the distance between rockets remains constant (if they are at rest relative to each other they share same ref system), then for us on launch platform, the rope and the distance (or 'empty space' around the rope if you like) between rockets, would contract.

Or do you think by cutting the contracting rope all of a sudden the rockets would seperate because the space between the rockets can not be contracted?

Do yo think the contraction of the rope pulls both rockets together??

 

In Bell's spaceship paradox we keep the distance between rockets constant by accellerating the rockets equally and simultaneously, per launch platform frame. This - and not because "only objects can Lorentz contract" - actually prevents the rockets -still according to launch platform frame- from getting closer to each other ('empty space' contracting between rockets). But in a rocket frame the other rocket will seperate (both rockets will not share same ref frame) and stretches rope until it breaks.

 

One can say that per launch plaform frame the string wants to contract but is prevented doing so (there will be relativistic stress in the rope) because we (the set up of the paradox) don't allow the distance (of empty space) between the rockets to contract. That's a total different story than pretending only objects can Lorentz contract

Edited June 23, 2017 by VandD

[Tim88]

I wrote in particular:

 

Note that it's important to distinguish between contraction of lengths (which is an action, dynamic change), and lengths and distances that are measured to be shorter according to one system than according to another system (which is a difference). "Causing to contract" is dynamic, about things happening.

 

This doesn't make sense. Length contraction occurs because of relativity of simultaneity. Whether there is 'material' between the events or only empty space doesn't make any difference. For a space traveler the distance of empty space to a star gets shorter. Period.

 

It probably did not make sense to you because despite my explicit clarification, you did not catch the difference between a dynamic change according to a single reference system, and a disagreement between two reference systems: for a space traveler the distance of empty space to a star is shorter than it is according to a person at rest with the star. No doubt that linguistic confusion is the only issue that you have, and it is totally unrelated to the topic at hand - thus no reason to elaborate any further.

 

The issue was that no doubt according to both Einstein and Poincare, the space between Bell's rockets which depart simultaneously as determined in the launch platform's reference system, will not shrink according to that same system. After the fuel has run out, the space between them will still be the same but in contrast, the rockets will be length contracted.

Once more, to elaborate further: the issue that Bell had with his colleagues was that he immediately understood this outcome as he was following the physical way of reasoning of Lorentz, Poincare and Einstein. His colleagues, who followed a more complex mathematical path, at first disagreed with him but finally conceded that he was right.

In such cases, there can be no difference between the predictions following Einstein or Poincare.

Edited June 26, 2017 by Tim88

[VandD]

You wrote:

 

 

Only objects can Lorentz contract,

 

 

For a space traveller the distance, empty space, between earth and a star contracts because of Lorentz contraction. Hence not only objects Lorentz contract.

[Tim88]

I explained that:

 

[although] Only objects can Lorentz contract [..,] for a space traveler the distance of empty space to a star is shorter than it is according to a person at rest with the star.

For a space traveller the distance, empty space, between earth and a star contracts because of Lorentz contraction. Hence not only objects Lorentz contract.

 

It appears that you continue to misunderstand the issue; in any case, you lost track of the topic. As a reminder, here the first claimed empirical difference between Einstein and Poincare was:

 

if you had a series of rods, with spaces in between, [the contraction of atoms and molecules] would not cause the space in between to equally contract. Einstein's theory was that "space itself" contracted.

I brought it to your attention that this has effectively been treated by Bell who stressed the importance of the physical understanding of the contraction of atoms and molecules using Maxwell's equations, and Bell's lesson is rather nicely shown in an illustration in Wikipedia in which consequently the empty space does not contract together with the rockets, exactly as Poincare would have it.

 

Please stick to the topic at hand and explain how, if indeed you think so, Einstein predicts such a "space contraction" between the series of rods in disagreement with Poincare and Bell.

PS. the following citation may be useful to clarify my position, which is on this topic the same as that of Bell:

 

"It is my impression that those with a more classical education, knowing something of the reasoning of Larmor, Lorentz, and Poincare, as well as that of Einstein, have stronger and sounder instincts. I will try to sketch here a simplified version of the Larmor-Lorentz-Poincare approach that some students might find helpful.

[..]

In so far as microscopic electrical forces are important in the structure of matter, this systematic distortion of the field of fast particles will alter the internal equilibrium of fast moving material. It is to be expected therefore that a body set in rapid motion will change shape. Such a change of shape, the Fitzgerald contraction, was in fact postulated on empirical grounds by G. F. Fitzgerald in 1889 to explain the results of certain optical experiments."

- Bell, How to teach Special Relativity

[VandD]

You said:

 

As far as I remember, Einstein never held that "space itself" contracted; that would even lead to self contradictions such as with Bell's Spaceship paradox

Is doesn't lead to self contradictions such as Bell's spacehip paradox.

For Einstein "space itself" does contract, but in Bell's case study one prevents that empty space to contract.

 

explain how, if indeed you think so, Einstein predicts such a "space contraction" between the series of rods in disagreement with Poincare and Bell.

In Bell's case study, the space does not contract. Einstein agrees. BUT... not because "only objects Lorentz contract", but because Bell's set up is such that one prevents -per launch frame- the empty space contraction between the rods. Don't you understand the difference?

Now tell me what Poincarés explanation is for the space between the rods NOT contracting. Is it same explanation as Einstein's?

Edited June 27, 2017 by VandD

[Tim88]

[..] Is doesn't lead to self contradictions such as Bell's spacehip paradox. [..]

You misunderstood again: Bell's spaceship paradox is not a self contradiction.

For Einstein "space itself" does contract, but in Bell's case study one prevents that empty space to contract.

I don't think so: please provide a citation of Einstein claiming that ""space itself" does contract".

I explained twice that "contracts" is a verb, referring to dynamics as measured in a single reference system such as in Bell's example. In that example there is even nothing that could be physically able to "contract space"; I find that concept nonsensical.

[..]

Now tell me what Poincarés explanation is for the space between the rods NOT contracting. Is it same explanation as Einstein's?

Sigh. That specific problem was first designed in 1959; Poincare was then long dead. Bell's explanation is, as I already cited, basically the same as the explanation by Poincare and Lorentz, with which Einstein agreed, but with which HallsofIvy apparently disagreed, as you saw. Maybe you also disagree with it; that still hasn't become clear.

 

Thus, for a last time: if you claim that Bell's (and Poincare's) explanation as cited, leads to different predictions from those by Einstein, please show it. Without anyone trying to show a difference, there is nothing to discuss in this thread.

Edited June 28, 2017 by Tim88

[studiot]

Thank you both for this entertaining game of ping-pong

 

and also for introducing me to Bell's paradox, which I had not heard of before.

 

+1 each

 

I don't actually see the issue with Bells.

 

Even in a purely Newtonian universe if you accelerate a compound object hard enough and long enough you will break it.

 

The pair of spaceships and the gossamer thread constitute a compound object.

 

Just as a bag of blood in a centrifuge does.

 

What happens to the bag of blood if you overspin?

 

It demonstrates the Principle of Equivalence very nicely.

 

[VandD]

I explained twice that "contracts" is a verb, referring to dynamics as measured in a single reference system

 

Are you now telling me that "length contraction" only refers to dynamics as measured in a single reference system ?

[Tim88]

 

Are you now telling me that "length contraction" only refers to dynamics as measured in a single reference system ?

 

Should I take that as implying that you also cannot come up with an empirical difference between Einstein's interpretation and that of Bell and Poincare?

 

Still, for completeness I'll wrap up the clarification. You may call it nitpicking, but technically speaking contraction relates to a change. Bell's Spaceship "paradox" may look paradoxical due to a common mix-up in the literature between, on the one hand, a change of length, and on the other hand, a comparison of distances between two reference systems. No doubt that sloppy usage is widespread because in most situations it doesn't matter, so that (as far as I know) no special term has been introduced for the second comparison. As nicely illustrated on the picture in Wikipedia, it does matter in such cases as Bell brought up: only the objects contract according to the launchpad system S, as sketched in the top illustration - just as first brought up in post #8. Nevertheless, when the rockets have reached a speed at which the string breaks, all the pictured distances are a factor γ greater according to the instantaneous co-moving frame S' than according to S.

[VandD]

 

Should I take that as implying that you also cannot come up with an empirical difference between Einstein's interpretation and that of Bell and Poincare?

 

 

Obviously the experimental evidence -in the lauch frame- will be the same, for the simple reason the exercise wants to keep distance to be the same.

But that's not the full story.

With your Bell/Poincaré contraction only applying to objects, there IS empirical difference between Einstein and Bell/Poincaré, ... in a rocket frame, after launch:

In such a frame, for Einstein the distance (space) between rockets increases. For Bell/Poincaré it doesn't.

 

If Bell/Poincaré only applies length contraction to objects, then he only applies the Lorentz Tranformations to objects (?). If he wants to teach special relativity that way, then he is wrong. Because special relativity is not about only objects contracting. The 'contraction' refers to changing of length. Doesn't make a difference whether it's about objects or distance between objects (space).

[Tim88]

I wrote, following the reasoning of Bell:

 

[..] Nevertheless, when the rockets have reached a speed at which the string breaks, all the pictured distances are a factor γ greater according to the instantaneous co-moving frame S' than according to S.

 

Obviously the experimental evidence -in the lauch frame- will be the same, for the simple reason the exercise wants to keep distance to be the same.

But that's not the full story.

With your Bell/Poincaré contraction only applying to objects, there IS empirical difference between Einstein and Bell/Poincaré, ... in a rocket frame, after launch:

In such a frame, for Einstein the distance (space) between rockets increases. For Bell/Poincaré it doesn't. [..]

The picture to which I referred, is exactly what follows from Poincare-Einstein-Bell's physical assumptions. Your "rocket frame" is nothing else but an infinite series of different S' - which is an instantly co-moving inertial frame. There is no empirical difference.

[studiot]