Chronon
Encyclopedia
A chronon is a proposed quantum
of time
, that is, a discrete and indivisible "unit" of time as part of a theory
that proposes that time is not continuous. While time is a continuous quantity in both standard quantum mechanics
and general relativity
, many physicists have suggested that a discrete model of time might work, especially when considering the combination of quantum mechanics with general relativity
to produce a theory of quantum gravity
.
The term was introduced in this sense by Robert Lévi. Henry Margenau
suggested that the chronon might be the time for light to travel the classical radius of an electron.
A quantum theory in which time is a quantum variable with a discrete spectrum, and which is nevertheless consistent with special relativity,
was proposed by C. N. Yang.
One such model was introduced by Piero Caldirola in 1980. In Caldirola's model, one chronon corresponds to about 6.97×10 seconds for an electron. This is much longer than the Planck time
, another proposed unit for the quantization of time, which is only about 5.39×10 seconds. The Planck time is a universal quantization of time itself, whereas the chronon is a quantization of the evolution in a system along its world line
and consequently the value of the chronon, like other quantized observables in quantum mechanics, is a function of the system under consideration, particularly its boundary conditions. The value for the chronon, θ0, is calculated from:
From this formula, it can be seen that the nature of the moving particle being considered must be specified since the value of the chronon depends on the particle's charge and mass.
Caldirola claims the chronon has important implications for quantum mechanics, in particular that it allows for a clear answer to the question of whether a free falling charged particle does or does not emit radiation. This model supposedly avoids the difficulties met by Abraham-Lorentz
's and Dirac
's approaches to the problem, and provides a natural explication of quantum decoherence
.
Quantum
In physics, a quantum is the minimum amount of any physical entity involved in an interaction. Behind this, one finds the fundamental notion that a physical property may be "quantized," referred to as "the hypothesis of quantization". This means that the magnitude can take on only certain discrete...
of time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....
, that is, a discrete and indivisible "unit" of time as part of a theory
Theory
The English word theory was derived from a technical term in Ancient Greek philosophy. The word theoria, , meant "a looking at, viewing, beholding", and referring to contemplation or speculation, as opposed to action...
that proposes that time is not continuous. While time is a continuous quantity in both standard quantum mechanics
Quantum mechanics
Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...
and general relativity
General relativity
General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics...
, many physicists have suggested that a discrete model of time might work, especially when considering the combination of quantum mechanics with general relativity
General relativity
General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics...
to produce a theory of quantum gravity
Quantum gravity
Quantum gravity is the field of theoretical physics which attempts to develop scientific models that unify quantum mechanics with general relativity...
.
The term was introduced in this sense by Robert Lévi. Henry Margenau
Henry Margenau
Henry Margenau was a German-U.S. physicist, and philosopher of science.-Early life:Born Bielefeld, Germany, Margenau obtained his bachelor's degree from Midland Lutheran College, Nebraska before his M.Sc...
suggested that the chronon might be the time for light to travel the classical radius of an electron.
A quantum theory in which time is a quantum variable with a discrete spectrum, and which is nevertheless consistent with special relativity,
was proposed by C. N. Yang.
One such model was introduced by Piero Caldirola in 1980. In Caldirola's model, one chronon corresponds to about 6.97×10 seconds for an electron. This is much longer than the Planck time
Planck time
In physics, the Planck time, , is the unit of time in the system of natural units known as Planck units. It is the time required for light to travel, in a vacuum, a distance of 1 Planck length...
, another proposed unit for the quantization of time, which is only about 5.39×10 seconds. The Planck time is a universal quantization of time itself, whereas the chronon is a quantization of the evolution in a system along its world line
World line
In physics, the world line of an object is the unique path of that object as it travels through 4-dimensional spacetime. The concept of "world line" is distinguished from the concept of "orbit" or "trajectory" by the time dimension, and typically encompasses a large area of spacetime wherein...
and consequently the value of the chronon, like other quantized observables in quantum mechanics, is a function of the system under consideration, particularly its boundary conditions. The value for the chronon, θ0, is calculated from:
From this formula, it can be seen that the nature of the moving particle being considered must be specified since the value of the chronon depends on the particle's charge and mass.
Caldirola claims the chronon has important implications for quantum mechanics, in particular that it allows for a clear answer to the question of whether a free falling charged particle does or does not emit radiation. This model supposedly avoids the difficulties met by Abraham-Lorentz
Hendrik Lorentz
Hendrik Antoon Lorentz was a Dutch physicist who shared the 1902 Nobel Prize in Physics with Pieter Zeeman for the discovery and theoretical explanation of the Zeeman effect...
's and Dirac
Paul Dirac
Paul Adrien Maurice Dirac, OM, FRS was an English theoretical physicist who made fundamental contributions to the early development of both quantum mechanics and quantum electrodynamics...
's approaches to the problem, and provides a natural explication of quantum decoherence
Quantum decoherence
In quantum mechanics, quantum decoherence is the loss of coherence or ordering of the phase angles between the components of a system in a quantum superposition. A consequence of this dephasing leads to classical or probabilistically additive behavior...
.
See also
- Planck timePlanck timeIn physics, the Planck time, , is the unit of time in the system of natural units known as Planck units. It is the time required for light to travel, in a vacuum, a distance of 1 Planck length...
- Elementary particleElementary particleIn particle physics, an elementary particle or fundamental particle is a particle not known to have substructure; that is, it is not known to be made up of smaller particles. If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which...
- GravastarGravastarA gravastar is an object hypothesized in astrophysics as an alternative to the black hole theory by Pawel Mazur and Emil Mottola. It results from assuming real, physical limitations on the formation of black holes...
- List of particles
- Particle physicsParticle physicsParticle physics is a branch of physics that studies the existence and interactions of particles that are the constituents of what is usually referred to as matter or radiation. In current understanding, particles are excitations of quantum fields and interact following their dynamics...
- Quantum mechanicsQuantum mechanicsQuantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...
- Theoretical physicsTheoretical physicsTheoretical physics is a branch of physics which employs mathematical models and abstractions of physics to rationalize, explain and predict natural phenomena...