Theory of everything differ both from gravity and from electromagnetism. A further hurdle was the acceptance that in a TOE, quantum mechanics had to be incorporated from the start, rather than emerging as a consequence of a deterministic unified theory, as Einstein had hoped. Gravity and electromagnetism could always peacefully coexist as entries in a list of classical forces, but for many years it seemed that gravity could not even be incorporated into the quantum framework, let alone unified with the other fundamental forces. For this reason, work on unification, for much of the twentieth century, focused on understanding the three "quantum" forces:
Unified growth theory Unified growth theory Unified growth theory was developed to address the inability of growth theory to explain key empirical regularities in the growth processes of individual economies and the world economy as a whole. Unlike endogenous growth theory that focuses entirely on the modern growth regime and is therefore unable to explain the roots of inequality across nations, unified growth theory captures in a single framework the fundamental phases of the process of development over the entire course of human history Unified growth theory was first advanced by Oded Galor and his co-authors who were able to characterize in a