Planck length
where formula_2 is the radius of curvature of spacetime small domain, formula_3 is the coordinate of the small domain, formula_4 is the Planck length, formula_5 is the reduced Planck constant, formula_6 is Newton's gravitational constant, and formula_7 is the speed of light. These uncertainty relations are another form of Heisenberg's uncertainty principle at the Planck scale.