Gravity and Electromagnetism are now naturally married in a brilliant re-derivation of Einstein's General Theory of Relativity. Sachs uncovers a long forgotten paper by Einstein and Mayer that holds the secret. But Einstein missed its fundamental importance. The vector basis used by Einstein in deriving the General Theory is incomplete. Just as Maxwell (and Tait) used the more complete basis of quaternions in deriving Maxwell's equations, Sachs builds a complete theory of General Relativity but using a quaternionic basis. Hamilton and his quaternions are finally vindicated....
The additional key insight is that Sachs realises that Einstein needed to eliminate the discrete symmetries of reflections in space and time....
Sachs can lay a strong claim to having merged all the known forces in this brilliant work....