In this paper I present a personal and scientific biographical sketch of Poincare,... He was so encyclopedic that he dealt with the outstanding questions in the different branches of physics and mathematics; he had altered whole fields of science such as non-Euclidean geometry, Arithmetic, celestial mechanics, thermodynamics and kinetic theory, optics, electrodynamics, Maxwell's theory, and other topics from the forefront of Fin de Siecle physical science. It is interesting to note that as opposed to the prosperity of biographies and secondary papers studying the life and scientific contributions of Albert Einstein, one finds much less biographies and secondary sources discussing Poincare's life and work. As opposed to Einstein, Poincare was not a cultural icon. Beginning in 1920 Einstein became a myth and a world famous figure.She makes several comparisons, including this:

In 1900 Poincaré was indeed in his highest ranks, and he was the most successful scientist in France and maybe in the whole world. However, Poincaré felt deep inside a very big crisis. The contents of his lectures, which he presented in the two international conferences (of physics and philosophy), and the talk presented in the Lorentz Festschrift celebrations, reveal this crisis pertaining to reconciling Lorentz's theory with the principle of relativity and the principle of reaction.QYes, they had different routes. Poincare's approach was to use the constant speed of light to synchronize clocks and define space and time; insist on the relativity principle as the best explanation of the Michelson-Morley experiment; invent a non-Euclidean geometry for four-dimensional spacetime using the Lorentz group and Minkowski metric; prove the covariance of Maxwell's equations for electromagnetism; and use symmetry invariance to find new laws of physics so that relativity becomes a spacetime theory that applies to everything.

It is interesting to note that Einstein had a crisis at about the same time. Einstein appeared to have been trying to solve the conflict between the principle of Galilean relativity and that of the constancy of the velocity of light in Maxwell's theory; and the conflict between the principle of Galilean relativity and Maxwell's theory and Faraday's law. Although both Einstein and Poincaré were feeling a crisis at about the same time, they followed completely different routes.

Einstein's approach was to make Lorentz's theorem of corresponding states into a postulate, and to use Poincare synchronization to give an exposition of Poincare's physical interpretation of Lorentz's local time. He is thus able to give a presentation of Lorentz's electron theory. Lorentz explained, "Einstein simply postulates what we have deduced".

Poincare's approach quickly became the backbone of special relativity. This is all explained in my book.

This is a bit of a repetition of Whitaker's old and mostly debunked noise though.

ReplyDeleteOne might ask, considering some people claim Einstein plagiarized Poincaré, what differences made Einstein’s work his own original venture?

*Einstein completely discarded the ether, as he predicted and theorized that the expressions of the laws of physics should be the same/similar for any inertial frame. Also: as mentioned before, his meaning of "new kinematics" meant that time and space, measured in differing inertial systems, were on the exact footing.

*Poincaré didn't exclude the aether, as he viewed it as the privileged reference-frame wherein "true" space and time were defined.

*Einstein viewed the radiation paradoxes of Poincaré to be only solved by assuming the inertia of energy.

*Poincaré didn't bring up this paradox problem again.

*Einstein brought forth the operational meaning of time dilation.

*Poincaré didn't consider the aspect above therefore

The essence of special relativity lies in the thesis that Newton's account of space and time is incorrect and that all processes unfold against a space and time governed by SR. That thesis was laid out clearly in Einstein's 1905 paper. Poincaré did not build on two kinematical postulates, but worked in terms of the Maxwell equations. He also didn’t take the following steps necessary and it is these differences that set Einstein's work sharply apart from his. Poincare never laid out that central thesis. He did make some suggestive remarks about the speed of light and simultaneity: yes. But most importantly: they were never developed into the simple (nor a provable and testable) claim that Newton was wrong on space and time.

One of the more fundamental differences between Poincaré's theory and Einstein's concerns the form of a light-pulse for observers at rest and observers in motion. For Poincaré a light-pulse that is spherical for an observer at rest with respect to the ether is actually an elongated ellipsoid for all other observers in inertial motion. For Einstein; on the other hand, a spherical light-pulse actually has a spherical form for all inertial observers.

Another difference; concerning the years that went on as Poincaré and Einstein continued their work on relativity, was the choice of space-time. Now one of the consequences of using the convention of either Minkowski or Galilei space-time comes from the fact that the geometry of phenomenal space is set by this choice and the spatial geometry in both of the given space-times is that of Euclid. Poincaré knew of this problem, but he didn't understand that his roots in pre-relativist physics guided him erronously. He began with the choice of the wrong space-time for his work. Poincaré did not feel his own approach, which involves the adoption of Galilei space-time, to be less promising in 1912 than the Einstein-Minkowski alternative, which involves the adoption of Minkowski spacetime. Since Einstein's general relativity (1915) is incompatible with Galilei space-time and compatible with Minkowski spacetime (as the tangent space, valid for any infinitesimal patch of curved spacetime): Poincaré (in retrospect) chose his spacetime unwisely.

Poincare said in the talk at the 1904 St. Louis Congress of Arts and Science:

ReplyDelete"The principle of relativity, according to which the laws of physical phenomena should be the same, whether for an observer fixed, or for an observer carried along in a uniform movement of translation; so that we have not and could not have any means of discerning whether or not we are carried along in such a motion . . .

Perhaps, likewise, we should construct a whole new mechanics, of which we only succeed in catching a glimpse, where inertia increasing with the velocity, the velocity of light would become an impassable limit. The ordinary mechanics, more simple, would remain a first approximation, since it would be true for velocities not too great, so that we should still find the old dynamics under the new.

...

We should not have to regret having believed in the principles, and even, since velocities too great for the old formulas would always be only exceptional, the surest way in practice would be still to act as if we continued to believe in them. They are so useful, it would be necessary to keep a place for them. To deterrnine to exclude them altogether, would be to deprive oneself of a precious weapon. I hasten to say in conclusion we are not yet there, and as yet nothing proves that the principles will not come forth from the combat victorious and intact."

Still stuck on the ether of classical mechanics. One of Poncairé's hypotheses at the ”La Mécanique Nouvelle” Göttingen-lecture was that a body which is in translatory motion experiences a change of deformation in the direction of motion. So still; after about four years post Einstein's initial paper on this matter, he clearly didn't understand or accept that length contraction was a consequence of Einstein's two postulates!

On the one hand he very often critiqued the stationary ether of classical mechanics, but at the same time was unable to do away with it himself. He continously brought such a premise into his work and left what ever doubts he had about his own work and others in his philosophical lectures on the metaphysical possibilities, which is where he at times hinted that an ether might one day not be necessary at all.

In his 1905 publications, Einstein did describe the construction of inertial coordinate systems, and he implicitly asserted that the propagation of light was isotropic with respect to the same class of coordinate systems, in terms of which mechanical inertia is isotropic.

The fact that Lorentz work was notably important is not disputable. The fact that Poincaré was skirting the bush, coming close to arriving at a correct and provable theory of special relativity is correct. The fact that Einstein's work on Special Relativity put the pieces together and revealed the complete theory in a coherent, correct and provable formulation is not really disputable.

Lorentz and Poincare developed most of the math used, but never fully embraced the principles behind it. As late as 1909, Poincare apparently still held some doubts as to whether Einstein was right or just plan crazy! (Of course, many others also had similar doubts). On some level Lorentz grasped the superiority of the purely relativistic approach, as is evident from the words he included in the second edition of his "Theory of Electrons" in 1916:

"If I had to write the last chapter now, I should certainly have given a more prominent place to Einstein's theory of relativity by which the theory of electromagnetic phenomena in moving systems gains a simplicity that I had not been able to attain. The chief cause of my failure was my clinging to the idea that the variable t only can be considered as the true time, and that my local time t' must be regarded as no more than an auxiliary mathematical quantity."

These comments seem to be copied from Karl Radl. I also found them here and here. Saying that Poincare chose "the wrong space-time for his work" instead of "the Einstein-Minkowski alternative" is grossly incorrect. Minkowski spacetime is named after Minkowski who got it from Poincare. Einstein had nothing to do with it, and initially rejected it. All this is explained in my book and this blog.

ReplyDeleteThe comments are written by myself, posted at the SC-blog by Karl Radl, and elsewhere by yours truly. Poincaré didn't originate it Minkowski spacetime, which is what Einstein applied in contrast to Poincaré. This was however just an added note of curiosa on the previously mentioned differences. And it was Poincaré who didn't accept or understand Einstein's work on a very crucial bit, like I said above; "One of Poncairé's hypotheses at the ”La Mécanique Nouvelle” Göttingen-lecture was that a body which is in translatory motion experiences a change of deformation in the direction of motion. So still; after about four years post Einstein's initial paper on this matter, he clearly didn't understand or accept that length contraction was a consequence of Einstein's two postulates!"

ReplyDeleteHowever, just to add, it is correct that Minkowski's spacetime was influenced by musings done by Poincaré. However, it needs to be noted that actual spacetime of Minkowski is a reformulation and notably different in influence, not a direct one from when he restated Maxwell's calculations on behalf of invariance of L-T (Lorentz Transformation). Minkowski was able to do the nice reformulation in light of Einstein's work, not Poincaré's, for reasons stated quite clearly above.

ReplyDeleteRegarding Special Relativity, Poincaré did maintain an inclusion of an aether as crucial, even as late as in his 1909 Lille address.

ReplyDeleteEven if Poincaré did equations to explain why the Michelson Morley experiment hadn't yielded proof for an aether, he continued to base his predictions and assumptions that there was an aether. Mind you that Poincaré's paper, "Sur la Dynamique de l'Électron", on the Lorentz contraction, deals through dynamic explanations.

Poincaré's theory tried to reconcile two incompatible ideas, which were, the existence of a preferred inertial frame and the relativity principle. Einstein discarded the idea of this given and privileged reference frame, which was the correct and revealing move to do at the time of these predictions.

I would resist the idea that special relativity consists essentially in identifying that the Lorentz group can be found in electrodynamics. That is a mathematical fact about Maxwell's electrodynamics yes, however the essence of special relativity lies in the thesis that Newton's account of space and time is incorrect and that all processes unfold against a space and time governed by SR.

Hans, much of what you say is incorrect. Poincare had the 4-dimensional spacetime geometry and electromagnetic covariance in his long 1905 paper. These concepts are at the core of special relativity and they are absent from Einstein's 1905 paper. Minkowski used these concepts from Poincare, not Einstein. Einstein wrote a review paper on relativity after Poincare's paper, and Einstein obviously did not understand the 4-dimensional spacetime geometry and electromagnetic covariance at all.

ReplyDeleteBy 1909, Einstein's approach was obsolete. Poincare understood the approach but was not impressed by it.

It was Poincare who explicitly rejected the aether; he said that it was just a convention. No part of Poincare's theory depended on the existence of the aether. Einstein denied that he rejected the aether.

If you are going to quote Lorentz, you should mention that he credited Poincare over Einstein.

I have a lot of explanations in my book and this blog addressing these points. Go ahead and tell me if I am wrong in anything I say. I cannot reproduce it all in these comments. But if you think that Einstein said something original in 1905, just tell me what it is.

ReplyDelete