Loop quantum gravity (LQG) is a theoretical framework that tries to quantize space and time directly. This seems to make a lot of sense, given that general relativity relates gravity to the shape of spacetime itself. If the ultimate goal is a quantum theory that applies to gravity, it stands to reason that space and time will have to be quantized somehow.
Loop quantum gravity is even younger than string theory, so it is also unfinished and still being developed. The basis of LQG is the postulate that space itself is not continuous, but composed of a fine mesh of tiny loops. These loops are about the same size as the strings of string theory, about 10-35 meters wide, and they are the units in which space and time are quantized.
LQG holds promise as a potential theory of everything, and it has some advantages over string theory. It may provide a more direct path to a quantum field theory of gravity without so many extra dimensions. However, it is just as far from making any testable predictions. It is currently most applicable to cosmological issues like the expansion and ultimate fate of the universe, and less directly applicable to fundamental particles and the standard model.
Leave a Reply