- Loop Quantum Gravity (Wikipedia.org)
"Loop quantum gravity (LQG) is a proposed theory of spacetime which is built from the ground up with the idea of spacetime quantization via the mathematically rigorous theory of loop quantization. It preserves many of the important features of general relativity, such as local Lorentz invariance, while at the same time employing quantization of both space and time at the Planck scale in the tradition of quantum mechanics."
"This is not the most popular theory of quantum gravity; many physicists have philosophical problems with it. For one thing, the critics of this theory say that LQG is one theory of gravity and nothing more. There are many other theories of quantum gravity, and a list of them can be found on the Quantum gravity page." 01-06
- Planck Scale (Wikipedia.org)
"The Planck units are often semi-humorously referred to by physicists as 'God's units'. They eliminate anthropocentric arbitrariness from the system of units: some physicists believe that an extra-terrestrial intelligence might be expected to use the same system."
"At the 'Planck scales' in length, time, density, or temperature, one must consider both the effects of quantum mechanics and general relativity. Unfortunately this requires a theory of quantum gravity which does not yet exist."
"Most of the Planck units are either too small or too large for practical use, unless prefixed with large powers of ten." 01-06
- Quantum Field Theory and Quantum Gravity (SimonFoundation.org)
"The revelation that particle interactions, the most basic events in nature, may be consequences of geometry significantly advances a decades-long effort to reformulate quantum field theory, the body of laws describing elementary particles and their interactions. Interactions that were previously calculated with mathematical formulas thousands of terms long can now be described by computing the volume of the corresponding jewel-like “amplituhedron,” which yields an equivalent one-term expression."
"The new geometric version of quantum field theory could also facilitate the search for a theory of quantum gravity that would seamlessly connect the large- and small-scale pictures of the universe. Attempts thus far to incorporate gravity into the laws of physics at the quantum scale have run up against nonsensical infinities and deep paradoxes. The amplituhedron, or a similar geometric object, could help by removing two deeply rooted principles of physics: locality and unitarity." 09-13
- Quantum Gravity (Cambridge University)
Provides various models for handling quantum gravity. 01-06
- Quantum Gravity (Stanford Encyclopedia of Philosophy)
"Quantum Gravity: A physical theory describing the gravitational interactions of matter and energy in which matter and energy are described by quantum theory. In most, but not all, theories of quantum gravity, gravity is also quantized. Since the contemporary theory of gravity, general relativity, describes gravitation as the curvature of spacetime by matter and energy, a quantization of gravity implies some sort of quantization of spacetime itself. Insofar as all extant physical theories rely on a classical spacetime background, this presents profound methodological and ontological challenges for the philosopher and the physicist." 01-06
- Quantum Gravity (Wikipedia.org)
"Quantum gravity is the field of theoretical physics attempting to unify the theory of quantum mechanics, which describes three of the fundamental forces of nature, with general relativity, the theory of the fourth fundamental force: gravity. The ultimate goal of some is a unified framework for all fundamental forces—a theory of everything." 01-06