where R μ μ is the radius of curvature of spacetime small domain, x μ μ is the coordinate of the small domain, ℓ ℓ P is the Planck length, ℏ ℏ is the reduced Planck constant, G is the Newtonian constant of gravitation, and c is the speed of light. These uncertainty relations are another form of Heisenberg's uncertainty principle at the Planck scale.