Classical unified field theories a survey of classical relativistic field theories of gravitation that have been motivated by theoretical concerns other than unification, see Classical theories of gravitation. For a survey of current work toward creating a quantum theory of gravitation, see quantum gravity. The early attempts at creating a unified field theory began with the Riemannian geometry of general relativity, and attempted to incorporate electromagnetic fields into a more general geometry, since ordinary Riemannian geometry seemed incapable of expressing the properties of the electromagnetic field. Einstein was not alone in his attempts to unify electromagnetism and gravity; a large number of mathematicians and
Unified growth theory take-off from an epoch of stagnation to the modern era of sustained growth. The testable predictions of this evolutionary theory and its underlying mechanisms have been confirmed empirically and quantitatively. Unified growth theory contributes to Macrohistory. It sheds light on the divergence in income per capita across the globe during the past two centuries. It identifies the factors that have governed the transition from stagnation to growth and have thus contributed to the observed worldwide differences in economic development. It highlights the persistent effects that variations in historical and prehistorical conditions have had on the composition of human capital and