A long sought-after goal of modern physics is the formulation of a complete description of all interactions mediated by the four fundamental forces by a grand unified theory that would account for all phenomena within a single theoretical framework.

There are four fundamental forces that occur in nature: the strong, the electromagnetic, the weak, and the gravitational force. The strong force is aptly named because it represents the strongest force and is responsible for binding nuclear particles together. The standard model describes all of the fundamental forces except gravity, the weakest of the fundamental forces. Gravity is described by the general theory of relativity.

Although weak in comparison to the other fundamental forces, gravity acts on all particles that have energy and mass and it is a long-range force. As of 2000, there is no complete quantum theory of gravity. The postulated force carrier for...