Who Was Right - Poincare, Einstein or Neither

[bhobba]

I read that in 1911 Poincare asked Einstein a rather deceptive question. What is the mechanical basis of SR. Einstein replied none, and promtly left, while Poincare was left in shock.

I will not say what I think (yet), but was Poincare right to be shocked Einstein dismissed such a question so glibly? Was he right in saying no?

Would Einstein have answered differently after Noether published her theorems?

What would be the answer today, with our current knowledge Einstein did not have?

Thanks
Bill

 

[Histspec]

It's disputed whether this discussion between Einstein and Poincaré at the Solvay conference 1911 was about SR. The science historian Peter Galison (author of "Einstein's Clocks and Poincare's Maps") argues that "mechanics" rather refers to quantum mechanics, while Thiboult Damour thinks it was about relativistic mechanics (SR).

See Proceedings of the 23th Solvay conference in 2005, which you can fully download here, and p. 19 for the discussion between Galison and Damour.
http://www.solvayinstitutes.be/html/solvayconf_physics.html

 

[martinbn]

What did he mean by mechanical basis?

 

[bhobba]

What did he mean by mechanical basis?

That was Poincare's question. What he meant, and Einsteins response, would be part of discussing who was right.

The following may help:
http://www.ulb.ac.be/sciences/ptm/pmif/ProceedingsHP/Damour.pdf

The question was made at the 1911 Solvay conference, but in the above was from De Broglie's (not THAT De Broglie - I think it was his brother who was older and also a physicist) notes so may not have been the exact wording. It was in French so the exact wording suffers also from translation issues - this is from a translation program:
'I remember one day in Brussels, as Einstein was exposing his ideas [on the "new mechanics" that is to say relativistic], Poincar'e asked him asked: 'What do you think about your reasoning?' Einstein answered him: 'No mechanics', which seemed to surprise his interlocutor.'

Different - but the same gist.

I got the original quote from Ohanian:
https://www.amazon.com/dp/0393337685/?tag=pfamazon01-20

What he wrote may also be subject to the same issues as what De-Broglie remembered. I don't want to say anything yet about what I think, but I can say Ohanian thought it was a very penetrating question Einstein did not give serious enough consideration to.

Answering either would I think bring out the key issues I wanted to explore.

Thanks
Bill

 

[Dale]

Are you asking a question about history or about physics? If you are asking a history question then I have no useful knowledge. But if you are asking a physics question then I am not sure what question it is.

 

[martinbn]

The first version of Poincare question was "What is the mechanical basis of SR." The second you gave is "What do you think about your reasoning?", the actual quote from Damour is "Quelle m´ecanique adoptez-vous dans vos raisonnements?". In my opinion all this requires some context. What was Einstein discussing in 1911? Was it just special relativity or was it already ideas about gravity?

 

[bhobba]

Are you asking a question about history or about physics? If you are asking a history question then I have no useful knowledge. But if you are asking a physics question then I am not sure what question it is.

Definitely a question about physics.

I will rephrase it - is their a mechanical basis to relativity. It may seem their isn't since, in Einstein's time SR, as he thought of it, at least at first, concerned the nature of time and mechanics was about Newton - so Einstein was correct - its not about mechanics. But since then we have things like Noether that puts this in a different light ie symmetry is seen as important and now view SR perhaps differently - it also being a about symmetry. Does this mean their is a deeper connection than Einstein thought - although I don't think it was was Poincare had in mind. He was too close to the old way of thinking, but when I read it I was with Ohanian, if he hadn't dismissed it then perhaps a deeper understanding may have happened earlier - or maybe things like Noether were needed to before you could get a proper answer.

If its still not clear I can give my answer and take it from there.

Thanks
Bill

 

[martinbn]

I don't want to flood and derail, but my problems is with the phrase "mechanical basis" of any theory. What does it mean?

 

[bhobba]

The first version of Poincare question was "What is the mechanical basis of SR." The second you gave is "What do you think about your reasoning?", the actual quote from Damour is "Quelle m´ecanique adoptez-vous dans vos raisonnements?". In my opinion all this requires some context. What was Einstein discussing in 1911? Was it just special relativity or was it already ideas about gravity?

Interesting point. I do not know other parts of the conversation so there may be more to it. And yes while the gist of the two quotes are the same they are different.

I was taking it at face value. Poincare and those of the old guard such as Lorentz, always stuck with LET, Einstein thought it about the nature of time. Interestingly in modern times Bell extolled its virtues (I most definitely do not agree with Bell here - but its a legit argument):
http://philsci-archive.pitt.edu/5454/1/Bell.pdf

Minkowski I think by 1911 had mathematically made it about the geometry of space-time, but Einstein took a while to cotton onto that. I don't know if he had by 1911 - of course by 1915 and his formulation of GR he must have.

So rephrasing it - is SR about symmetry/geometry, is such just philosophy like Bell thought and SR is better viewed as what happens in classical models of atoms and electrons, or is it something else. Again. without saying what I think (you can probably guess it) I think Bell has it wrong - but can't prove it.

Again if its still unclear just give the word and I will post what I think so we can take it from there.

Thanks
Bill

 

[Histspec]

http://www.ulb.ac.be/sciences/ptm/pmif/ProceedingsHP/Damour.pdf

The question was made at the 1911 Solvay conference, but in the above was from De Broglie's (not THAT De Broglie - I think it was his brother who was older and also a physicist) notes so may not have been the exact wording. It was in French so the exact wording suffers also from translation issues - this is from a translation program:
'I remember one day in Brussels, as Einstein was exposing his ideas [on the "new mechanics" that is to say relativistic], Poincar'e asked him asked: 'What do you think about your reasoning?' Einstein answered him: 'No mechanics', which seemed to surprise his interlocutor.'

No, that is a widespread misinterpretation: The text within square brackets concerning relativity was a comment by Damour - it isn't present in the original line of de Broglie. Here is the complete text by Maurice de Broglie ("Poincare et la philosophie, Oeuvres t. 11, p. 76"). He first paraphrases some statements made by Poincaré in his essay "The quantum theory" from 1912, followed by his recollection of the discussion between Einstein and Poincaré in 1911::

Laissons de côté les réflexions mathématiques sur l'espace, la logique do l'infini, et venons-en aux derniers chapitres, inspires par le voyage de l'auteur a Bruxelles pour le Congres Solvay de 1911. "On peut se demander", écrit-il, "si la Mécanique n'est pas a la veille d'un nouveau bouleversement, les physiciens de Bruxelles parlaient d'une mécanique nouvelle qu'ils opposaient a la mécanique ancienne, or, qu'e'tait-ce que cette mécanique ancienne, était-ce celle de NEWTON? non, c'était celle de LORENTZ avec le principe de relativité, qui, il y a cinq ans a peine, paraissait le comble de la hardiesse". Je me rappelle qu'un jour a Bruxelles, comme EINSTEIN exposait ses idées, POINCARÉ lui demanda: "Quelle mécanique adoptez-vous dans vos raisonnements?" EINSTEIN lui répondit : "Aucune mécanique" ce qui parut surprendre son interlocuteur.

Translation: Let us leave aside the mathematical reflections on space, the logic of the infinite, and come to the last chapters, inspired by the author's trip to Brussels for the Solvay Congress of 1911. "One may wonder", he wrote, "if mechanics is not on the eve of a new commotion, the physicists of Brussels spoke of the new mechanics which they contrasted with the old mechanics, and what was this old mechanics, was it that of Newton? No, it was that of LORENTZ with the principle of relativity, which, hardly five years ago, seemed to be the height of boldness". I remember that one day in Brussels, as EINSTEIN exposed his ideas, POINCARÉ asked him: "What mechanics do you adopt in your reasoning?" EINSTEIN replied: "No mechanics" which seemed to surprise his interlocutor.

As you can see, he calls the mechanics of Lorentz (including the principle of relativity) the "old mechanics", which is endangered by the new mechanics - which is of course quantum mechanics because that was the topic of the paper in which Poincaré originally made that statement. Here is the translation of the Original of Poincaré's 1912 essay on quantum theory (emphasizes by me), posthumously published in "Dernieres Pensees", 1913 (English translation "Last essays", 1963):

THE QUANTUM THEORY
One may wonder if mechanics is not on the eve of a new commotion. A congress of about twenty physicists from different countries assembled recently in Brussels, and at every moment they could be heard talking of the new mechanics which they contrasted with the old mechanics. Now, what was that old mechanics ? Was it that of Newton, the one which still reigned uncontested at the close of the nineteenth century ? No, it was the mechanics of Lorentz, the one dealing with the principle of relativity; the one which, hardly five years ago, seemed to be the height of boldness.
Does this mean that this mechanics of Lorentz has had only an ephemeral fortune; that it has been merely a vagary, and that we are about to return to the ancient gods whom we had imprudently abandoned ? Not in the least. The conquests of yesterday are not jeopardized. In all instances in which it differs from that of Newton, the mechanics of Lorentz endures. We continue to believe that no body in motion will ever be able to exceed the speed of light ; that the mass of a body is not a constant, but depends on its speed and the angle formed by this speed with the force which acts upon the body; that no experiment will ever be able to determine whether a body is at rest or in absolute motion either in relation to absolute space or even in relation to the ether.
To these strokes of boldness, however, we wish to add more, and much more disconcerting ones. We now wonder not only whether the differential equations of dynamics must be modified, but whether the laws of motion can still be expressed by means of differential equations. And therein would lie the most profound revolution that natural philosophy has experienced since Newton.

So Galison was right - the discussion between Einstein and Poincaré was concerned with quantum theory, not SR.

Here is another misquote concerning Einstein and Poincaré and the Solvay congress, from a letter by Einstein to Zangger in 1911, as quoted by Pais (Subtle is the Lord, p.170) and unfortunately many others:

Poincaré war (gegen die Relativitätstheorie) einfach allgemein ablehnend, zeigte aber bei allem Scharfsinn wenig Verständnis für die Situation.

Translation: Poincaré was simply generally antipathetic (in regard to relativity theory) and showed little understanding for the situation despite all his sharp wit.

Again, the text within brackets concerning relativity was a comment by someone, it is not present in the original letter, see Collected papers, vol. 5, p. 379:
http://einsteinpapers.press.princeton.edu/vol5-doc/399
Translation: http://einsteinpapers.press.princeton.edu/vol5-trans/244

The science historian Olivier Darrigol, like Galison, argues that Einstein in his letter to Zangger was actually alluding to Poincaré’s attitude toward the quantum problem.
Darrigol, O. (2004), "The Mystery of the Einstein-Poincaré Connection", Isis, 95 (4): 614–626

 

[bhobba]

I don't want to flood and derail, but my problems is with the phrase "mechanical basis" of any theory. What does it mean?

No derailing with that question - very penetrating.

By mechanics I am thinking the laws of physics as espoused by Newton. A hint about what I am getting at is its reformulation using the PLA and then Noether. What then is the 'extra' factor that gives mechanics? Is it the same thing that gives SR? If so Einstein should not be so quick to dismiss Poincare - but then again things were not quite the same in 1911 as later so maybe it was just the state of physics at the time. BTW I don't agree with Bell, but can't prove it. Is it as he says just philosophy? That would be slightly disturbing to me.

Thanks
Bill

 

[bhobba]

No, that is a widespread misinterpretation:

Ahhhhhh. So Ohanian goofed. That explains a LOT. Thank you so much for a clarification of that part.

Now forgetting the quote, that you clarified as wrong, I can state precisely my question.

Bell thought this whole geometry space-time thing pure philosophy and seemed to prefer a presentation of SR along the lines of LET. In light of modern physics with things like Noether etc can such a position be maintained I think symmetry is the foundation of modern physics so is more than mere philosophy - it a very real unifying concept.

IMHO It is the basis of mechanics, SR, QM, QFT - pretty much all of physics up to now. But is this right - or is Bell on the right track?

Thanks
Bill

 

[Paul Colby]

Relativity is a space-time symmetry. According to the way physics as a subject is organized, symmetries precede or is more basic than subjects like mechanics.

 

[martinbn]

Bell's position is a mystery to me. It is shared by other people who like Bohmian mechanics. Why would anyone, after Minkowski, even talk about LET except in historical discussions!

 

[bhobba]

Bell's position is a mystery to me. It is shared by other people who like Bohmian mechanics. Why would anyone, after Minkowski, even talk about LET except in historical discussions!

As I said I don't agree with Bell. But he is not to be dismissed easily. His rational is symmetry/geometry is philosophical rather than physical, while LET is physical. For me physical/philosophical is useless semantics - but we deal in science so provided its in accord with experiment its pure preference what you go for - just like BM in QM. Its interesting it still seems to infest some parts of SR even now. Science can be maddening like that - you go into it because for you curiosity holds a strong sway and you want answers - then you find it's not quite as clear cut as what you thought when you started - but perhaps even more interesting.

Thanks
Bill

 

[PeterDonis]

His rational is symmetry/geometry is philosophical rather than physical, while LET is physical. For me physical/philosophical is useless semantics - but we deal in science so provided its in accord with experiment its pure preference what you go for - just like BM in QM.

Yes, strictly speaking, I would say that "symmetry/geometry" vs. "LET" is a question of interpretation of SR, not physics, much like, say, "Copenhagen" vs. "Bohmian" is a question of interpretation of QM. In both cases, the different "interpretations" use the same underlying math and make the same predictions for all experimental results, so there's no difference between them as far as physics is concerned. It's a matter of personal preference about what kind of story you want to tell about the physics.

 

[pervect]

I read that in 1911 Poincare asked Einstein a rather deceptive question. What is the mechanical basis of SR. Einstein replied none, and promtly left, while Poincare was left in shock.

I will not say what I think (yet), but was Poincare right to be shocked Einstein dismissed such a question so glibly? Was he right in saying no?

Would Einstein have answered differently after Noether published her theorems?

What would be the answer today, with our current knowledge Einstein did not have?

Thanks
Bill

I would have thought that Poincare was angling towards the answer "Geometry" to his question about a mechanical basis. But that's just a gut reaction.

This also fits in with Einstein's rejection - he only later came to acknowledge the usefulness of the geometrical explanations of special relativity.

 

[Dale]

I will rephrase it - is their a mechanical basis to relativity.

Well, the basis of relativity is the two postulates. And the two postulates apply to mechanical laws as well as electromagnetic laws.

 

[strangerep]

Well, the basis of relativity is the two postulates.

Ahem,... 1 postulate.

 

[bhobba]

Well, the basis of relativity is the two postulates. And the two postulates apply to mechanical laws as well as electromagnetic laws.

I STRONGLY believe in the POR, and also STRONGLY in what you wrote - in fact I just love proofs of it based on just the POR where the constant speed automatically pops out of the math (it may be infinity in which case you get the Galilean transformations):
http://www2.physics.umd.edu/~yakovenk/teaching/Lorentz.pdf

With LET though you have an un-observable aether whose wind is different in different frames breaking the isotropy of the symmetry requirements of the POR. IMHO such a position has all sorts of issues eg how do you incorporate LET into Quantum Field Theory.

The maddening thing is you can't prove it wrong - it feels wrong, cumbersome, inelegant, kludgy - I could probably think of a few others additives, however will spare the reader - but it's perfectly valid. Bell - was a great physicist but for the life of me I don't know why he took the position he did, It may be a quirk he had - he was very much inclined to BM as well - some say that has an implied aether, but I don't know enough about BM to be sure of that one. Demystifyer may be able to give some detail on that. It could be part of what made Bell, well Bell, and because of that was able to do what he did.

Regarding the original question it has been answered - what Ohanian quoted was not in the context he tried to imply - as someone much more knowledgeable in these things than me pointed out. I now have a couple of issues with him - a few from his standard textbook on GR and now this. But to be fair nobody, including me (actually especially me) is perfect, and some of the issues were fixed in the latest version of the text - so at least he does try to fix his 'mistakes'.

Thanks
BIll

 

[bhobba]

Ahem,... 1 postulate.

Yes - as per the link I gave for those that want the gory detail.

Thanks
Bill

 

[martinbn]

I must say I am a little surprised by Poincare. Of course this is based on pure speculation on my part. I don't know enough history to be surprised and from this thread it seems that it would be very difficult if at all possible to disentangle the fact from anecdote from misinterpretation. It seems possible that Poincare at that time was still thinking that Einstein's approach needed ether, and asking about its mechanical properties. If I am not mistaken he (and possibly Lorentz) had a derivation for the mass energy relation prior to Einstein, but had additional assumptions and it held for the electron only. So he might have been asking about the mechanical properties of matter that Einstein needed for his derivation. To both of these Einstein would have answered no mechanical assumptions. What surprises me is that Poincare that late (1911) still did not understand Einstein. The other thing is that surely Poincare must have been aware of Minkowski's work. So why was he, as a mathematician, not converted to SR and Minkowski space-time!

 

[bhobba]

So why was he, as a mathematician, not converted to SR and Minkowski space-time!

Poincare is a hero of mine, but I think its important to realize he dies a year later - maybe his mind wasn't quite as sharp as one of the greatest polymaths of all time would suggest.

Thanks
Bill

 

[martinbn]

Well,yes, but he was not that old, not 60 yet.

 

[Dale]

Ahem,... 1 postulate.

You still need two postulates. The POR alone gets you to a transform with one parameter which may be finite (Lorentz transform) or infinite (Galilean transform). So you still need a second postulate that it is finite and equal to c. Of course, you can substitute experiments for postulates.

 

[Histspec]

What surprises me is that Poincare that late (1911) still did not understand Einstein.

While it's true that Poincaré didn't have the complete SR in 1905, we should not forget that he discussed the principle of relativity (1900, 1904), clock synchronization with light signals assuming constant speed (1900, 1904), conventionality of simultaneity (1898), etc. several years before Einstein.
https://en.wikipedia.org/wiki/Henri_Poincaré#Work_on_relativity
So Poincaré was probably upset by the fact that Einstein didn't give him credit, and therefore Poincaré chose to ignore him. Or he ignored Einstein because he didn't like the idea of giving up the mechanical aether. We'll never know...

The other thing is that surely Poincare must have been aware of Minkowski's work.

Let's not forget that Poincaré himself introduced most of this stuff in 1905/1906 (Lorentz transformation as a rotation in 4-space, four-position, four-velocity, four-force, etc.).
https://en.wikisource.org/wiki/Translation:On_the_Dynamics_of_the_Electron_(July)
He probably ignored Minkowski for the same reasons, why he ignored Einstein. We'll never know...

So why was he, as a mathematician, not converted to SR and Minkowski space-time!

It seems that he was undecided in terms of the reality of these concepts. He wrote in one of his "Last essays" named "Space and Time" about the views of "some physicists" in 1912:

Everything happens as if time were a fourth dimension of space, and as if four-dimensional space resulting from the combination of ordinary space and of time could rotate not only around an axis of ordinary space in such a way that time were not altered, but around any axis whatever. For the comparison to be mathematically accurate, it would be necessary to assign purely imaginary values to this fourth coordinate of space. The four coordinates of a point in our new space would not be x,y, z, and t, but x,y, z, and it. But I do not insist on this point; the essential thing is to notice that in the new conception space and time are no longer two entirely distinct entities which can be considered separately, but two parts of the same whole, two parts which are so closely knit that they cannot be easily separated.
...
What shall be our position in view of these new conceptions? Shall we be obliged to modify our conclusions? Certainly not; we had adopted a convention because it seemed convenient and we had said that nothing could constrain us to abandon it. Today some physicists want to adopt a new convention. It is not that they are constrained to do so; they consider this new convention more convenient; that is all. And those who are not of this opinion can legitimately retain the old one in order not to disturb their old habits. I believe, just between us, that this is what they shall do for a long time to come.

 

[Paul Colby]

I always assumed Einstein put most weight on electrodynamics. The relativity principle and ensuing discussion must preserve electrodynamics. All the discussion of clocks and simultaneity are coming to grips with c being related to physical constants in Maxwell's equations. Einstein's reply is saying "mechanics is not electrodynamics, go away." Hence the title "On the Electrodynamics of Moving Bodies"

 

[strangerep]

You still need two postulates. The POR alone gets you to a transform with one parameter which may be finite (Lorentz transform) or infinite (Galilean transform). So you still need a second postulate that it is finite and equal to c. Of course, you can substitute experiments for postulates.

Heh, I'm not sure why any modern physicist would prefer a postulate over an experiment.

 

[Demystifier]

Relativity is a space-time symmetry. According to the way physics as a subject is organized, symmetries precede or is more basic than subjects like mechanics.

That's certainly true in high-energy physics, but not in condensed-matter physics. In the latter, one starts with non-relativistic QM (without any particularly interesting symmetries) and arrives at emergent symmetries as collective macroscopic effects in specific phases of matter.

 

[Demystifier]

So why was he, as a mathematician, not converted to SR and Minkowski space-time!

Maybe because Poincare thought that math should be consistent with the common sense. That would be perfectly consistent with the Poincare's oppositions to the Cantor's theory of infinite sets.

 

[martinbn]

Maybe because Poincare thought that math should be consistent with the common sense. That would be perfectly consistent with the Poincare's oppositions to the Cantor's theory of infinite sets.

I wasn't aware of this. Quite interesting, i'll have to look up the details.

 

[Demystifier]

I wasn't aware of this. Quite interesting, i'll have to look up the details.

What you were not aware of? That Poincare didn't like Cantor's theory, or that Poincare thought that math should be consistent with common sense? The former is a historical fact, the latter is my interpretation of that fact.

Another personal interpretation. Poincare studied dynamical systems. The very concept of a dynamical system implicitly assumes that the concept of time has a special role which, among other things, makes it different from the concept of space. From that point of view, Minkowski space-time looks like a rather foreign concept.

 

[martinbn]

What you were not aware of? That Poincare didn't like Cantor's theory, or that Poincare thought that math should be consistent with common sense? The former is a historical fact, the latter is my interpretation of that fact.

The first.

Another personal interpretation. Poincare studied dynamical systems. The very concept of a dynamical system implicitly assumes that the concept of time has a special role which, among other things, makes it different from the concept of space. From that point of view, Minkowski space-time looks like a rather foreign concept.

He also studied many other things, where there is no notion of time whatsoever. For example he was interested in geometry/analysis on the upper half plane. Minkowski space-time should have been very appealing to him.

Here is my personal speculation. Poincare was too burdened by philosophy and in questions like this one was not thinking like a mathematician.

 

[PAllen]

I also think the credit issues were important to Poincare. His letters with Felix Kein were quite biting at times when Poincare felt Klein was implying priority.

 

[Paul Colby]

That's certainly true in high-energy physics, but not in condensed-matter physics. In the latter, one starts with non-relativistic QM (without any particularly interesting symmetries) and arrives at emergent symmetries as collective macroscopic effects in specific phases of matter.

Good point on emergent symmetries. It's not clear to me crystal symmetries emerge if the underlying space isn't translationally and rotationally symmetric, though. I think Einstein' s answer today would have been the same and for the same reasons.