Searching for a Quantum Theory of Gravity
by Owen Borville
July 17, 2024
Physics
The search for a "Quantum Theory of Gravity" seeks to describe gravity according to the principles of quantum mechanics, and thereby unite all forces of nature into quantum theory.
There currently is no quantum theory of gravity and physicists have been working on this issue for a long time, since at least the 20th century and the age of modern physics.
A quantized theory of gravity is still an unsolved problem in the field of physics.
Gravity is one of the four fundamental forces in physics in the universe, along with electromagnetism, the strong nuclear force, and the weak nuclear force.
Three of these forces have a quantum description, while gravity does not.
The main challenge with finding a quantum theory or quantum description of gravity is that there is a lack of experimental data.
The term quantum refers to the smallest discrete unit of a phenomenon.
Without having a quantum theory of gravity, physicists cannot create a unified theory for all forces in nature.
A unified theory of gravity would help explain how the universe began and would help explain what happens inside black holes.
The closest that physicists have come to a theory of everything, or a theory of all forces is the Standard Model, which describes three of the four fundamental forces in nature and classifies all known elementary particles.
Quantum gravity is an attempt by physicists to explain two theories in physics.
One theory, quantum mechanics, explains how physics works at very small scales, such as with subatomic particles, while the other theory, gravity, explains how physics works at very large scales, such as planets, solar systems, galaxies, stars, and black holes.
Gravity is a real force, because it describes the resulting interaction between two masses and physicists have not been able to quantize gravity like the other forces of physics.
However, 20th century physicist Albert Einstein viewed gravity as the result of curved space. He believed that the entire universe existed within four dimensions called space-time, with three physical dimensions and the fourth dimension as time.
The largest objects in the universe, like stars, galaxies, and black holes, warp the space-time around them, according to Einstein's theory.
Despite not having a complete quantum theory of gravity, there are several theories that have attracted attention in the physics world.
One is string theory and the other is loop quantum gravity theory.
The main idea of string theory is to replace the point particles of quantum field theory, like photons and electrons, with one-dimensional extended objects called strings.
Loop quantum gravity theory postulates that the structure of space and time is composed of finite loops woven into an extremely fine fabric or network.
This theory attempts to incorporate the Standard Model, the quantum theory of the three other forces, with gravity, instead of keeping gravity as a separate, unique force.
Quantum mechanics suggests everything is made up of quanta, or packets of energy, that can behave as both a particle and a wave.
Some other physicists say that gravity cannot be quantized and it must be expressed in its standard classical form, and therefore treated separately from the other three forces.
Still other physicists include the classical form of gravity within a hybrid model with the other forces.
The research on quantum theory and gravity is ongoing, and new breakthroughs could be possible in the future.
wikipedia.org/quantumgravity
space.com
plato.stanford.edu
scientificamerican.com
by Owen Borville
July 17, 2024
Physics
The search for a "Quantum Theory of Gravity" seeks to describe gravity according to the principles of quantum mechanics, and thereby unite all forces of nature into quantum theory.
There currently is no quantum theory of gravity and physicists have been working on this issue for a long time, since at least the 20th century and the age of modern physics.
A quantized theory of gravity is still an unsolved problem in the field of physics.
Gravity is one of the four fundamental forces in physics in the universe, along with electromagnetism, the strong nuclear force, and the weak nuclear force.
Three of these forces have a quantum description, while gravity does not.
The main challenge with finding a quantum theory or quantum description of gravity is that there is a lack of experimental data.
The term quantum refers to the smallest discrete unit of a phenomenon.
Without having a quantum theory of gravity, physicists cannot create a unified theory for all forces in nature.
A unified theory of gravity would help explain how the universe began and would help explain what happens inside black holes.
The closest that physicists have come to a theory of everything, or a theory of all forces is the Standard Model, which describes three of the four fundamental forces in nature and classifies all known elementary particles.
Quantum gravity is an attempt by physicists to explain two theories in physics.
One theory, quantum mechanics, explains how physics works at very small scales, such as with subatomic particles, while the other theory, gravity, explains how physics works at very large scales, such as planets, solar systems, galaxies, stars, and black holes.
Gravity is a real force, because it describes the resulting interaction between two masses and physicists have not been able to quantize gravity like the other forces of physics.
However, 20th century physicist Albert Einstein viewed gravity as the result of curved space. He believed that the entire universe existed within four dimensions called space-time, with three physical dimensions and the fourth dimension as time.
The largest objects in the universe, like stars, galaxies, and black holes, warp the space-time around them, according to Einstein's theory.
Despite not having a complete quantum theory of gravity, there are several theories that have attracted attention in the physics world.
One is string theory and the other is loop quantum gravity theory.
The main idea of string theory is to replace the point particles of quantum field theory, like photons and electrons, with one-dimensional extended objects called strings.
Loop quantum gravity theory postulates that the structure of space and time is composed of finite loops woven into an extremely fine fabric or network.
This theory attempts to incorporate the Standard Model, the quantum theory of the three other forces, with gravity, instead of keeping gravity as a separate, unique force.
Quantum mechanics suggests everything is made up of quanta, or packets of energy, that can behave as both a particle and a wave.
Some other physicists say that gravity cannot be quantized and it must be expressed in its standard classical form, and therefore treated separately from the other three forces.
Still other physicists include the classical form of gravity within a hybrid model with the other forces.
The research on quantum theory and gravity is ongoing, and new breakthroughs could be possible in the future.
wikipedia.org/quantumgravity
space.com
plato.stanford.edu
scientificamerican.com