Whitehead's Principle of Relativity - Unpublished Lectures by J. L.   Synge, FRS
  In Appendix B, there is a proposal about the Limb Effect which could be of great significance for Solar Physics.   In his PRINCIPLE OF RELATIVITY, Cambridge University Press, 1922 (republished Dover, 2004) A. N. Whitehead, making no use of ''curved'' space-time, derived the same values as Einstein for the red-shift, perihelion advance and the deflection of light. Synge expounds Whitehead's arguments in modern notation making it more accessible for contemporary Physicists but also obtains the Shapiro retardation of electromagnetic radiation by a gravitational field. Synge compares Einstein's GRT and Whitehead's PR, finding the observational evidence equally strong for both theories. He alluded to Whitehead's prediction of a Limb Effect remarking that to pursue its consequences would require a knowledge of QM which did not exist in 1922. Possibly this was not done because of physicist's Obsession with GRT since 1919. 
John Coleman