Quantum gravity seeks to describe gravity according to quantum mechanics instead of classical physics. It attempts to explain quantum effects in objects such as black holes or similar, as well as in the early stages of the Big Bang.
General relativity has limitations in explaining:
- gravitational singularities inside black holes
- dark matter and dark energy
- effects approaching the Planck length
- quantum fluctuations of spacetime
Two competing theories of quantum gravity are:
- String theory or M-theory
- Loop quantum gravity
Direct observation of quantum gravitational effects is thought to only appear at length scales near the Planck scale, around 10−35 meters, a scale that could only be accessible to scientific observation in the far future.