Loop Quantum Gravity

Loop quantum gravity is an approach to unifying general relativity with quantum mechanics that quantizes the geometry of spacetime itself, representing it as a network of discrete loops rather than as a smooth continuum. The approach grew out of a reformulation of general relativity introduced by Abhay Ashtekar in 1986, known as Ashtekar variables, which recast the theory in a form amenable to the quantization techniques used elsewhere in physics, and was developed through the late 1980s and 1990s largely by Carlo Rovelli, Lee Smolin and collaborators. A central prediction of the theory is that space is not infinitely divisible but has a granular, discrete structure at the Planck scale, with area and volume themselves taking on quantized values. Loop quantum gravity is one of the two most developed candidate approaches to a full theory of quantum gravity, alongside string theory, and as of the theory's current state neither has yet produced an experimentally testable, confirmed prediction distinguishing it from the other.