  It is commonly anticipated that gravity is subject to the standard principles
of quantum mechanics. Yet some (including Einstein) have questioned that
presumption, whose empirical basis is weak. Indeed, recently Freeman Dyson has
emphasized that no conventional experiment is capable of detecting individual
gravitons. However, as we describe, if inflation occurred, the Universe, by
acting as an ideal graviton amplifier, affords such access. It produces a
classical signal, in the form of macroscopic gravitational waves, in response
to spontaneous (not induced) emission of gravitons. Thus recent BICEP2
observations of polarization in the cosmic microwave background will, if
confirmed, provide empirical evidence for the quantization of gravity. Their
details also support quantitative ideas concerning the unification of strong,
electromagnetic, and weak forces, and of all these with gravity.
