Planck energy
Encyclopedia
In physics
, the unit of energy
in the system of natural units
known as Planck units
is called the Planck energy, denoted by EP.
1.956 × 109 J
1.22 × 1028 eV
0.5433 MWh
where c is the speed of light
in a vacuum,
is the reduced Planck's constant, and G is the gravitational constant
. EP is a derived, as opposed to basic, Planck unit.
An equivalent definition is:
where
is the Planck time
.
Also:
where
is the Planck mass.
The ultra-high-energy cosmic ray
s observed in 1991 had a measured energy of about 50 joule
s, equivalent to about 2.5×10−8 Ep. Most Planck units are fantastically small and thus are unrelated to "macroscopic" phenomena (or fantastically large, as in the case of Planck density). One Ep, on the other hand, is definitely macroscopic, approximately equaling the energy stored in an automobile gas tank (57.2 L of gasoline at 34.2 MJ/L of chemical energy).
Even so, Ep is a meaningful quantity in particle physics when gravitation
is taken into account. The Planck energy is not only the energy needed (in principle) to probe the Planck length, but is probably also the maximum possible energy that can fit into a region of that scale. A sphere 1 Planck length in diameter, containing 1 unit of Planck energy, will result in a tiny (and very hot) black hole
.
Planck units are designed to normalize the physical constant
s
, G, and c to 1. Hence given Planck units, the mass-energy equivalence
E = mc² simplifies to E = m, so that the Planck energy and mass are numerically identical. In the equations of general relativity
, G is often multiplied by 8π. Hence writings in particle physics
and physical cosmology
often normalize 8πG to 1. This normalization
results in the reduced Planck energy, defined as:
0.390 × 109 J 
2.43 × 1018 GeV.
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
, the unit of energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
in the system of natural units
Natural units
In physics, natural units are physical units of measurement based only on universal physical constants. For example the elementary charge e is a natural unit of electric charge, or the speed of light c is a natural unit of speed...
known as Planck units
Planck units
In physics, Planck units are physical units of measurement defined exclusively in terms of five universal physical constants listed below, in such a manner that these five physical constants take on the numerical value of 1 when expressed in terms of these units. Planck units elegantly simplify...
is called the Planck energy, denoted by EP.
1.956 × 109 JJoule
The joule ; symbol J) is a derived unit of energy or work in the International System of Units. It is equal to the energy expended in applying a force of one newton through a distance of one metre , or in passing an electric current of one ampere through a resistance of one ohm for one second...
1.22 × 1028 eVElectronvolt
In physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt...
0.5433 MWhMWH
MWH may stand for:* International Air Transport Association airport code for Grant County International Airport* MWH Global, an international water engineering consultancy* Men Without Hats, a Canadian New Wave band...
where c is the speed of light
Speed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...
in a vacuum,
is the reduced Planck's constant, and G is the gravitational constantGravitational constant
The gravitational constant, denoted G, is an empirical physical constant involved in the calculation of the gravitational attraction between objects with mass. It appears in Newton's law of universal gravitation and in Einstein's theory of general relativity. It is also known as the universal...
. EP is a derived, as opposed to basic, Planck unit.
An equivalent definition is:
where
is the Planck timePlanck 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...
.
Also:
where
is the Planck mass.The ultra-high-energy cosmic ray
Ultra-high-energy cosmic ray
In astroparticle physics, an ultra-high-energy cosmic ray or extreme-energy cosmic ray is a cosmic ray with an extreme kinetic energy, far beyond both its rest mass and energies typical of other cosmic rays....
s observed in 1991 had a measured energy of about 50 joule
Joule
The joule ; symbol J) is a derived unit of energy or work in the International System of Units. It is equal to the energy expended in applying a force of one newton through a distance of one metre , or in passing an electric current of one ampere through a resistance of one ohm for one second...
s, equivalent to about 2.5×10−8 Ep. Most Planck units are fantastically small and thus are unrelated to "macroscopic" phenomena (or fantastically large, as in the case of Planck density). One Ep, on the other hand, is definitely macroscopic, approximately equaling the energy stored in an automobile gas tank (57.2 L of gasoline at 34.2 MJ/L of chemical energy).
Even so, Ep is a meaningful quantity in particle physics when gravitation
Gravitation
Gravitation, or gravity, is a natural phenomenon by which physical bodies attract with a force proportional to their mass. Gravitation is most familiar as the agent that gives weight to objects with mass and causes them to fall to the ground when dropped...
is taken into account. The Planck energy is not only the energy needed (in principle) to probe the Planck length, but is probably also the maximum possible energy that can fit into a region of that scale. A sphere 1 Planck length in diameter, containing 1 unit of Planck energy, will result in a tiny (and very hot) black hole
Black hole
A black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that...
.
Planck units are designed to normalize the physical constant
Physical constant
A physical constant is a physical quantity that is generally believed to be both universal in nature and constant in time. It can be contrasted with a mathematical constant, which is a fixed numerical value but does not directly involve any physical measurement.There are many physical constants in...
s
, G, and c to 1. Hence given Planck units, the mass-energy equivalenceMass-energy equivalence
In physics, mass–energy equivalence is the concept that the mass of a body is a measure of its energy content. In this concept, mass is a property of all energy, and energy is a property of all mass, and the two properties are connected by a constant...
E = mc² simplifies to E = m, so that the Planck energy and mass are numerically identical. In the equations of 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...
, G is often multiplied by 8π. Hence writings in particle physics
Particle physics
Particle 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...
and physical cosmology
Physical cosmology
Physical cosmology, as a branch of astronomy, is the study of the largest-scale structures and dynamics of the universe and is concerned with fundamental questions about its formation and evolution. For most of human history, it was a branch of metaphysics and religion...
often normalize 8πG to 1. This normalization
Normalization
Normalization may refer to:- Mathematics and statistics:* Normalization property , term in mathematical logic and theoretical computer science* Noether normalization lemma, result of commutative algebra...
results in the reduced Planck energy, defined as:
0.390 × 109 J 2.43 × 1018 GeV.See also
- Max PlanckMax PlanckMax Karl Ernst Ludwig Planck, ForMemRS, was a German physicist who actualized the quantum physics, initiating a revolution in natural science and philosophy. He is regarded as the founder of the quantum theory, for which he received the Nobel Prize in Physics in 1918.-Life and career:Planck came...
- Planck epochPlanck epochIn physical cosmology, the Planck epoch , named after Max Planck, is the earliest period of time in the history of the universe, from zero to approximately 10−43 seconds , during which, it is believed, quantum effects of gravity were significant...
- Planck particlePlanck particleA Planck particle, named after physicist Max Planck, is a hypothetical particle defined as a tiny black hole whose Compton wavelength is comparable to its Schwarzschild radius. Its mass is thus approximately the Planck mass, and its Compton wavelength and Schwarzschild radius are about the Planck...
- Planck unitsPlanck unitsIn physics, Planck units are physical units of measurement defined exclusively in terms of five universal physical constants listed below, in such a manner that these five physical constants take on the numerical value of 1 when expressed in terms of these units. Planck units elegantly simplify...
- Quantum gravityQuantum gravityQuantum gravity is the field of theoretical physics which attempts to develop scientific models that unify quantum mechanics with general relativity...