Attempts to unify relativity, gravitation, and quantum mechanics
A depiction of the cGh cubeDiagram showing where quantum gravity sits in the a near-cube hierarchy of physics theories. Note that electromagnetism and quantum field theory in curved spacetime are added in as an extra and distinct items.
If one considers these three universal constants as the basis for a 3-D coordinate system and envisions a cube, then this pedagogic construction provides a framework, which is referred to as the cGh cube, or physics cube, or cube of theoretical physics (CTP).[3] This cube can be used for organizing major subjects within physics as occupying each of the eight corners.[4][5] The eight corners of the cGh physics cube are:
While there are several other physical constants, these three are given special consideration, because they can be used to define all Planck units and thus all physical quantities.[6] The three constants are therefore used sometimes as a framework for philosophical study and as one of pedagogical patterns.[7]