Vacuum energy is an underlying background energy that exists in space even when devoid of matter (known as free space). The vacuum energy results in the existence of most (if not all) of the fundamental forces - and thus in all effects involving these forces, too. It is observed in various experiments (like the spontaneous emission of light or gamma radiation, the Casimir effect, Van-Der Waals bonds, the Lamb shift, etc); and it is thought (but not yet demonstrated) to have consequences for the behavior of the Universe on cosmological scales. Space has been an interest for philosophers and scientists for much of human history. ... This article or section does not cite any references or sources. ... In physics, free space is a concept of electromagnetic theory, corresponding roughly to the vacuum, the baseline state of the electromagnetic field, or the replacement for the electromagnetic aether. ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ... Spontaneous emission is the process by which a molecule in an excited state drops to the ground state, resulting in the creation of a photon. ... In physics, the Casimir effect is a physical force exerted between separate objects, which is due to neither charge, gravity, nor the exchange of particles, but instead is due to resonance of all-pervasive energy fields in the intervening space between the objects. ... In chemistry, the term van der Waals force originally referred to all forms of intermolecular forces; however, in modern usage it tends to refer to intermolecular forces that deal with forces due to the polarization of molecules. ... In physics, the Lamb shift, named after Willis Lamb, is a small difference in energy between two energy levels and of the hydrogen atom in quantum mechanics. ... The Universe is defined as the summation of all particles and energy that exist and the space-time in which all events occur. ... Physical cosmology, as a branch of astrophysics, is the study of the large-scale structure of the universe and is concerned with fundamental questions about its formation and evolution. ...

Elementary particle theories

Quantum field theory, which describes the interactions between elementary particles in terms of fields, allows a contribution to the vacuum energy (even when no particles are present) in a form of the zero-point energy of the fields. An example is the Casimir effect, where two metal plates experience a small attractive force between them, which can be attributed to the dependence of the zero-point energy of the electromagnetic field on the distance between the plates. Since potential energy is defined up to an arbitrary constant, the absolute value of the vacuum energy might seem to be unimportant; however, it becomes important when gravity is involved, since gravity couples to the total energy of the system. Quantum field theory (QFT) is the quantum theory of fields. ... Interaction is a kind of action that occurs as two or more objects have an effect upon one another. ... In particle physics, an elementary particle is a particle of which other, larger particles are composed. ... The magnitude of an electric field surrounding two equally charged (repelling) particles. ... In physics, the zero-point energy is the lowest possible energy that a quantum mechanical physical system may possess; it is the energy of the ground state of the system. ... The magnitude of an electric field surrounding two equally charged (repelling) particles. ... In physics, the Casimir effect is a physical force exerted between separate objects, which is due to neither charge, gravity, nor the exchange of particles, but instead is due to resonance of all-pervasive energy fields in the intervening space between the objects. ... In physics, force is an influence that may cause a body to accelerate. ... In physics, the zero-point energy is the lowest possible energy that a quantum mechanical physical system may possess; it is the energy of the ground state of the system. ... The electromagnetic field is a physical field that is produced by electrically charged objects and which affects the behaviour of charged objects in the vicinity of the field. ... Potential energy is the energy that is by virtue of the relative positions (configurations) of the objects within a physical system. ... In mathematics and the mathematical sciences, a constant is a fixed, but possibly unspecified, value. ... Gravity is a force of attraction that acts between bodies that have mass. ... Gravity is a force of attraction that acts between bodies that have mass. ... In physics, two systems are coupled if they are interacting with each other. ...

This has important consequences on cosmological scales, where the vacuum energy is expected to contribute to the cosmological constant, which affects the expansion of the universe. The calculation of the vacuum energy in quantum field theory in terms of Feynman diagrams can be pictured as accounting for virtual particles (also known as vacuum fluctuations) which are created and destroyed out of the vacuum. Additional contributions to the vacuum energy come from spontaneous symmetry breaking in quantum field theory. Physical cosmology, as a branch of astrophysics, is the study of the large-scale structure of the universe and is concerned with fundamental questions about its formation and evolution. ... The cosmological constant (usually denoted by the Greek capital letter lambda: Λ) was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe. ... Wikipedia does not yet have an article with this exact name. ... Quantum field theory (QFT) is the quantum theory of fields. ... A Feynman diagram is a bookkeeping device for performing calculations in quantum field theory, invented by American physicist Richard Feynman. ... In the description of the interaction between elementary particles in quantum field theory, a virtual particle is a temporary elementary particle, used to describe an intermediate stage in the interaction. ... Look up Vacuum in Wiktionary, the free dictionary. ... Spontaneous symmetry breaking in physics takes place when a system that is symmetric with respect to some symmetry group goes into a vacuum state that is not symmetric. ... Quantum field theory (QFT) is the quantum theory of fields. ...

Implications

Vacuum energy has a number of consequences. For one, vacuum fluctuations are always created as particle/antiparticle pairs. The creation of these "virtual particles" near the event horizon of a black hole has been hypothesized by physicist Stephen Hawking to be a mechanism for the eventual "evaporation" of black holes. The net energy of the universe remains zero so long as the particle pairs annihilate each other within Planck time. If one of the pair is pulled into the black hole before this, then the other particle becomes "real" and energy/mass is essentially radiated into space from the black hole. This loss is cumulative and could result in the black hole's disappearance over time. The time required is dependent on the mass of the black hole, but could be on the order of 10¹⁰⁰ years for large solar-mass black holes. The Grand unification theory predicts a non-zero cosmological constant from the energy of vacuum fluctuations. Examining normal physical processes with knowledge of these field phenomena can lead to an interesting insight in electrodynamics. During discussions of perpetual motion, the topic of vacuum energy usually encourages serious inquiries. In physics, a virtual particle is a particle which exists for such a short time and space that its energy and momentum do not have to obey the usual relationship. ... For the science fiction film, see Event Horizon (film). ... Simulated view of a black hole in front of the Milky Way A black hole is an object with a gravitational field so powerful that a region of space becomes cut off from the rest of the universe – no matter or radiation (including light) that has entered the region can... Stephen William Hawking, CH, CBE, FRS, FRSA, (born 8 January 1942) is a British theoretical physicist. ... In physics, Hawking radiation is thermal radiation thought to be emitted by black holes due to quantum effects. ... In physics, the Planck time (tP), is the unit of time in the system of natural units known as Planck units. ... A googol is the large number 10100, that is, the digit 1 followed by one hundred zeros (in decimal representation). ... It has been suggested that this article or section be merged into Unified field theory. ... Physics (Greek: (phúsis), nature and (phusiké), knowledge of nature) is the branch of science concerned with the fundamental laws of the Universe. ... Process (lat. ... A phenomenon (plural: phenomena) is an observable event, especially something special (literally something that can be seen from the Greek word phainomenon = observable). ... Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, composed of the electric field and the magnetic field. ... This article or section should include material from Parallel Path See also Perpetuum mobile as a musical term Perpetual motion machines (the Latin term perpetuum mobile is not uncommon) are a class of hypothetical machines which would produce useful energy in a way science cannot explain (yet). ...

History

In 1934, Georges Lemaître used an unusual perfect-fluid equation of state to interpret the cosmological constant as due to vacuum energy. In 1973, Edward Tryon proposed that the Universe may be a large scale quantum mechanical vacuum fluctuation where positive mass-energy is balanced by negative gravitational potential energy. During the 1980s, there were many attempts to relate the fields that generate the vacuum energy to specific fields that were predicted by the Grand unification theory, and to use observations of the Universe to confirm that theory. These efforts have failed so far, and the exact nature of the particles or fields that generate vacuum energy, with a density such as that required by inflation theory, remains a mystery. 1934 (MCMXXXIV) was a common year starting on Monday (link will take you to calendar). ... Father Georges-Henri Lemaître (July 17, 1894 – June 20, 1966) was a Belgian Roman Catholic priest, honorary prelate, professor of physics and astronomer. ... An ideal gas or perfect gas is a hypothetical gas consisting of identical particles of zero volume, with no intermolecular forces. ... In physics and thermodynamics, an equation of state is a constitutive equation describing the state of matter under a given set of physical conditions. ... 1973 (MCMLXXIII) was a common year starting on Monday. ... Edward P. Tryon is a professor of physics at Hunter College in Manhattan. ... Unsolved problems in physics: What causes anything to have mass? The U.S. National Prototype Kilogram, which currently serves as the primary standard for measuring mass in the U.S. Mass is the property of a physical object that quantifies the amount of matter and energy it is equivalent to. ... Potential energy is the energy that is by virtue of the relative positions (configurations) of the objects within a physical system. ... The 1980s refers to the years from 1980 to 1989. ... It has been suggested that this article or section be merged into Unified field theory. ...

See also

• Dark energy
• Cosmological constant
• Lambdavacuum solution
• Quantum electrodynamics
• Zero-point energy
• Vacuum state

In physical cosmology, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. ... The cosmological constant (usually denoted by the Greek capital letter lambda: Λ) was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe. ... In general relativity, a lambdavacuum solution is an exact solution to the Einstein field equation in which the only term in the stress-energy tensor is a cosmological constant term. ... Quantum electrodynamics (QED) is a relativistic quantum field theory of electromagnetism. ... In physics, the zero-point energy is the lowest possible energy that a quantum mechanical physical system may possess; it is the energy of the ground state of the system. ... In quantum field theory, the vacuum state, usually denoted , is the element of the Hilbert space with the lowest possible energy, and therefore containing no physical particles. ...

External articles and references

• Saunders, S., & Brown, H. R. (1991). The Philosophy of vacuum. Oxford [England]: Clarendon Press.
• Poincaré Seminar, Duplantier, B., & Rivasseau, V. (2003). Poincaré Seminar 2002: vacuum energy-renormalization. Progress in mathematical physics, v. 30. Basel: Birkhäuser Verlag.