“Einstein’s general relativity, which describes the curvature of spacetime. General relativity is itself a field theory—it describes a field pervading all of space, in this case the gravitational field. And we have very well understood procedures for taking a classical field theory and quantizing it, yielding a quantum field theory. Apply those procedures to the known fields of fundamental physics, and we end up with something called the Core Theory. The Core Theory accurately describes not only particle physics but also gravity, as long as the strength of the gravitational field doesn’t grow too large. It is sufficient to describe every phenomenon that happens in your everyday experience, and quite a bit beyond—tables and chairs, amoebas and kittens, planets and stars.”