Tuesday, December 31, 2013

Site compares Poincare to Einstein

Craig Feinstein sends this 2010 site:
The father of relativity theory : Einstein vs Poincaré

We saw that it is Poincaré who names and formulates the principle of relativity, names and corrects Lorentz transformations, reports and exploits its group structure. To these examples, we could add that he establishes the method for synchronizing clocks by light signals (La mesure du temps, Revue de métaphysique et de morale, T.6, janv 1898), the formula of additivity of velocities, the invariance of Maxwell's equations in vacuum, and the hypothesis of the speed of light limit (Poincaré, 1905). Let's not forget that he also already uses a quadridmensional formalism that will inspire the future works of Minkowski, and then some. What is left?

He clearly masters most of the concepts and technical tools of what we call now the special relativity theory, except (and it is fundamental!) that it is to him just corrections brought to Lorentz works, part of a dynamics, and what's more, depending upon Maxwell's electromagnetic theory.
That is correct. Lorentz created special relativity theory as a way of reconciling Maxwell's electromagnetic theory with the Michelson-Morley experiment, and Poincare perfected Lorentz's theory.
Moreover, the principle of relativity concerns space-time and gives to it a physical meaning even if this space is empty, baring no body (it is a kinematics, that is to say a condition for the expression of dynamics), which Poincaré thinking about dynamics only could neither conceive, nor accept (Paty, 1987, p15).
This is crazy. Einstein does not have a spacetime theory. Poincare certainly did conceive and accept a spacetime theory where the Lorentz transformations are realized as the isometries of a 4-dimensional non-Euclidean geometry.

Like most everyone else, Johann reviews the facts and somehow credits Einstein anyway:
That's what makes Einstein the real father of the theory, because he presents in his 1905 paper all of these points (except the importance of the group structure of Lorentz transformations) in a coherent theory, building a kinematics on which the laws of physics will depend (and not the other way around), including those of electromagnetism.

Still, Poincaré surely stays a great and major precursor amongst all physicists and mathematicians who played a role in the history of the theory of special relativity.
No, Einstein did not present all of those points. He did not have the Lorentz group, the covariance of Maxwell's equations, or the 4-dimensional structure of spacetime. And where Einstein is getting relativity points correct, he is mostly recapitulating what was done years earlier by Lorentz and Poincare.

The main credit for Einstein is for claiming a theory broad enough for all the laws of physics. But it was Poincare who did that, not Einstein. Poincare had a spacetime theory that he applied to gravity. Einstein only had a way of understanding electromagnetism.

Johann admits that Einstein did not have the 4-dimensional spacetime, and only got it from Poincare and Minkowski years later:
To respond ..., first you're right saying that Minkowski popularized Poincaré's work and influenced Einstein, but it was AFTER its Cologne lecture of 1908. ... You could say that Einstein didn't grasp the 4 dimensionality of the theory before Minkowski and you would be right! He even said to Minkowski that it was an unnecessary complication, and recognized only later when working on the generalized theory that he was wrong.
That's right, and if you view the 4-dimensional spacetime as the crucial idea, that idea can be traced from Lorentz to Poincare to Minkowski to widespread acceptance, without Einstein having anything to do with it.
To conclude, I'd like to add that even if Einstein had read "La dynamique des électrons" (which I firmly believe he didn't, even if I can't prove it any more than you can prove he did), contrary to what you say his article did bring something fundamentally new and different than any previous work, including Poincaré's, namely 1° the concept of condition for the laws of physics, 2° the correct interpretation of space and time measurements and 3° A STRUCTURED AND CLEAN THEORY.
A condition for the laws of physics? Only Poincare explicitly looked for laws of physics obeying Lorentz group invariance. Only Poincare said relativity was a theory about our methods of measurement. And the only way I know to describe relativity as a coherent structured clean theory is to express it a non-Euclidean geometry, and that was done by Poincare in 1905 and Minkowski in 1908.

A separate post says:
Note that Henri Poincaré was already looking for all the invariants of the Lorentz group, using infinitesimal generators (which relates to the Lie algebra approach of our days) ! and this in 1905 (see our second bibliographic reference), the same year Einstein published his article, which Poincaré had still no knowledge...

However, let's not make the mistake of attributing relativity theory to Poincaré, since he never built any complete theory (in physics anyway), and was merely correcting and improving other physicists' work (Maxwell, Lorentz, etc.).
Not a complete theory? Poincare has all of the relativity formulas that Einstein had in 1905 and more, and somehow it was not a complete theory? That is ridiculous.

Crediting Einstein has to be based on what was different about Einstein's 1905 work, and his main virtue here seems to be that he never credited his sources. Lorentz and Poincare showed how their work built on previous work, so I guess they "merely" improved it. All science is correcting and improving previous work.

Craig writes:
If this is true, I can't see how Einstein got credit. Poincare's theory predicts everything that Einstein's theory predicts. The only thing that Einstein did was clean it up, get rid of the aether, make it sound nicer. But that is not science.

I think in that period of time, the early 1900's, the idea that there are no absolute standards was becoming popular in intellectual circles. Einstein came along and showed that physics could be put into this relativistic framework. Because of this, the intellectuals of that time crowned Einstein a hero, since it justified their worldview.

Today, society accepts the idea that there are no absolute standards. And Einstein is still the king. He was even made Time's man of the century. Poincare was just a man who played along with equations that predicted the motion of bodies, while Einstein was a man who got rid of absolutism in nature. So what if Poincare was just as right as Einstein?
Poincare was the one who wrote a popular 1902 book saying that there is no absolute space or time, and no aether.

I have heard it claimed that relativity and Einstein were popular among intellectual non-scientists because of confusion with relativism.


  1. I should say that I don't know for sure if what I wrote you above is true, as I am no expert on this matter. It's just my guess.

    I remember reading Poincare's 1902 book in college. I'll have to read it again.

  2. On the other hand, it is Einstein's way of thinking, that there is no aether and that c is the same in all frames of reference is what led him to formulate General Relativity. So perhaps, this is why he is credited for Special Relativity instead of Poincare? Since his thinking led to General Relativity?

  3. I think that Einstein would deny that he was led to general relativity by saying that there is no aether and that c is the same.

  4. Where exactly is the part in Poincare's book where he says there is no absolute space or time, and no aether?

  5. But he says after his statement on ether, "what is essential for us is, that everything happens as if it existed, and that this hypothesis is found to be suitable for the explanation of phenomena."

    So he's not entirely getting rid of the ether like Einstein. Of course, none of this matters scientifically.