Quantum Gravity
Planck length
The Planck length (ℓP) is the fundamental unit of length in the system of Planck units, defined by ℓP = √(ħG/c³). Using the 2022 CODATA adjustment maintained by NIST, its value is 1.616255(18) × 10⁻³⁵ meters with a relative standard uncertainty of 1.1 × 10⁻⁵. It is widely treated as a characteristic scale at which quantum and gravitational effects are expected to become comparable, motivating research programs in quantum gravity.
Quantum Foam
Quantum foam, also known as spacetime foam, is a theoretical concept in quantum mechanics, conceived by John Archibald Wheeler. It describes the fabric of spacetime at the subatomic, Planck scale as a turbulent, fluctuating medium where virtual particles and microscopic black holes are constantly created and destroyed, giving spacetime a "foamy" texture.