Albert Einstein was not the first person to predict that gravitational effects
propagate at light speed. George-Louis Le Sage stated that gravity might propagate at light speed in the eighteenth century.
In the 1870's, S. Tolver Preston created a formal theory
around Le Sage's idea, and attempted to explain how gravity might propagate at light speed. Paul
Gerber predicted that gravity propagates at light speed, in 1898,
and presented the correct equations for the perihelion motion of the planet
Mercury based on his idea, which equations Einstein plagiarized in 1915.
Henri Poincare predicted that gravity propagates at light speed,
in 1905, and created the first relativistic (scalar) covariant theory
of gravitation, long before Einstein plagiarized his ideas.
* * *
1. G. L. Le Sage, read by P. Prevost to the Berlin Academy in 1782, "Lucrece
Neutonien", Nouveaux Memoires de l'Academie royale des Sciences
et Belles-Lettres de Berlin,Year 1782, (Berlin, 1784), pp. 404-427;
reprinted in Notice de la Vie et des Ecrits de George-Louis Le Sage,
Chez J. J. Paschoud, Geneve, (1805), pp. 561-604; English translation
by C. G. Abbot with an introduction by S. P. Langley appears in: "The
Le Sage Theory of Gravitation", Annual Report of the Board
of Regents of the Smithsonian Institution Showing the Operations, Expenditures,
and Condition of the Institution for the Year Ending June 30, 1898,
(U.S.) Government Printing Office, Washington, (1899), pp. 139-160.
S. Tolver Preston, Physics of the Ether, E. & F. N. Spon,
P. Gerber, "Die raeumliche und zeitliche Ausbreitung der Gravitation",
Zeitschrift fuer Mathematik und Physik, Volume 43, (1898),
pp. 93-104; and Die Fortpflanzungsgeschwindigkeit der Gravitation,
Programmabhandlung des staedtischen Realgymnasiums zu Stargard in Pommerania,
(1902); reprinted "Die Fortpflanzungsgeschwindigkeit der Gravitation",
Annalen der Physik, Series 4, Volume 52, (1917), pp. 415-441.
J. H. Poincare, "Sur la Dynamique de l'Electron", Comptes
rendus hebdomadaires des seances de L'Academie des sciences, Volume
140, (1905), pp. 1504-1508; reprinted Oeuvres de Henri Poincare,
Volume IX, Gautier-Villars, (1954), pp. 489-493; English translations
appear in : G. H. Keswani and C. W. Kilmister, "Intimations of
Relativity before Einstein", The British Journal for the Philosophy
of Science, Volume 34, Number 4, (December, 1983), pp. 343-354,
at pp. 350-353; and, translated by G. Pontecorvo with extensive commentary
by A. A. Logunov, On the Articles by Henri Poincare ON THE DYNAMICS
OF THE ELECTRON, Publishing Department of the Joint Institute for
Nuclear Research, Dubna, (1995), pp. 7-14; and "Sur la Dynamique
de l'Electron", Rendiconti del Circolo matimatico di Palermo,
Volume 21, (1906, submitted July 23rd, 1905), pp. 129-176; reprinted
Oeuvres, Volume IX, pp. 494-550; English translation by H.
M. Schwartz, "Poincare's Rendiconti Paper on Relativity",
American Journal of Physics, Volume 39, (November, 1971), pp.
1287-1294; Volume 40, (June, 1972), pp. 862-872; Volume 40, (September,
1972), pp. 1282-1287; and English translation by G. Pontecorvo with
extensive commentary by A. A. Logunov, On the Articles by Henri
Poincare ON THE DYNAMICS OF THE ELECTRON, Publishing Department
of the Joint Institute for Nuclear Research, Dubna, (1995), pp. 15-78.