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:
A Brief History of Time to make a theory that combines the electromagnetic force, the weak nuclear force, and the strong nuclear force. This theory is called a "grand unified theory" (or a GUT). This theory tries to explain these forces in one big unified way or theory. Black holes are talked about in this chapter. Black holes are stars that have collapsed into one very small point. This small point is called a "singularity". Black holes suck things into their center because they have very strong gravity. Some of the things it can suck in are light and stars. Only very large stars, called