Henri Poincaré predicted gravitational waves in 1905

In connection with recent results on gravitational waves, LIGO, VIRGO and even the French Centre National de la Recherche Scientifique (CNRS) attribute to Albert Einstein the original prediction of gravitational waves. But actually, such a prediction was formulated by Henri Poincaré as early as June 5, 1905.

In connection with recent results on gravitational waves, LIGO, VIRGO and even the French Centre National de la Recherche Scientifique (CNRS) attribute to Albert Einstein the original prediction of gravitational waves. This is, however, a wrong assertion. The existence of gravitational waves traveling at the speed of light was explicitly predicted, as a requirement of space-time geometry, by Henri Poincaré in his article Sur la dynamique de l'électron (On electron dynamics, June 5, 1905) where he formulated special relativity. In this fundamental paper, published by the French Académie des Sciences, Poincaré refers to Hendrik Antoon Lorentz who emphasized that his space-time transformation should apply to all forces and not just to electromagnetism.

In his short article of 5 June 1905 Sur la dynamique de l'électron, C.R. T.140 (1905) 1504-1508 (Académie des Sciences, France), http://www.academie-sciences.fr/pdf/dossiers/Poincare/Poincare_pdf/Poincare_CR1905.pdf , Henri Poincaré explicitly formulated special relativty with an upgrade of the space-time transformations that he called "Lorentz transformations" and to which he referred as the "Lorentz group".

After having discussed the new space-time geometry, Poincaré writes:

(...)

Mais ce n’est pas tout: Lorentz, dans l’Ouvrage cité, a jugé nécessaire de compléter son hypothèse en supposant que toutes les forces, quelle qu’en soit l’origine, soient affectées, par une translation [a change of inertial frame in Poincaré's language], de la même manière que les forces électromagnétiques, et que, par conséquent, l’effet produit sur leurs composantes par la transformation de Lorentz est encore défini par les équations (4).

Il importait d’examiner cette hypothèse de plus près et en particulier de rechercher quelles modifications elle nous obligerait à apporter aux lois de la gravitation. C’est ce que j’ai cherché à déterminer; j’ai été d’abord conduit à supposer que la propagation de la gravitation n’est pas instantanée, mais se fait avec la vitesse de la lumière. (...)

Quand nous parlerons donc de la position ou de la vitesse du corps attirant, il s’agira de cette position ou de cette vitesse à l’instant où l’onde gravifique est partie de ce corps; quand nous parlerons de la position ou de la vitesse du corps attiré, il s’agira de cette position ou de cette vitesse à l’instant où ce corps attiré a été atteint par l’onde gravifique émanée de l’autre corps; il est clair que le premier instant est antérieur au second.

(...)

(end of quote)


According to Poincaré, the requirement of a universal space-time geometry with the speed of light c as the critical speed implies that the gravitational force must be carried by gravitational waves propagating with a speed equal to c

As Poincaré explicitly underlines, the space-time geometry defined by Lorentz tranformations applies to all existing forces including the gravitational ones. Thus, gravitation cannot propagate instantaneously and must instead propagate at the speed of light.

Considering the gravitational interaction between two bodies, Poincaré introduces a "gravific wave" leaving the first body, traveling at the speed of light and reaching the second body at a later time. This was the original formulation of the prediction of gravitational waves.

A decade later, with general relativity, Albert Einstein considered more involved scenarios with an effective space-time curvature generated by gravitation in a static universe. But this does not invalidate the basic principle formulated by Henri Poincaré in 1905.

Poincaré also refers to the previous work byPierre-Simon de Laplace, Count of Laplace (1749-1827), one of the main French scientists of the period of Napoléon Bonaparte, who had already considered the possibility that gravitation propagates at some finite speed.

Le Club est l'espace de libre expression des abonnés de Mediapart. Ses contenus n'engagent pas la rédaction.