Energy Density of Empty Space
In physics, "vacuum energy" or "zero-point energy" is the volumetric energy density of empty space. More recent developments have expounded on the concept of energy in empty space.
Modern physics is commonly classified into two fundamental theories: quantum field theory and general relativity. Quantum field theory takes quantum mechanics and special relativity into account, and it's a theory of all the forces and particles except gravity. General relativity is a theory of gravity, but it is incompatible with quantum mechanics. Currently these two theories have not yet been reconciled into one unified description, though research into "quantum gravity" and, more recently, stochastic electrodynamics, seeks to bridge this divide.
In general relativity, the cosmological constant is proportional to the energy density of empty space, and can be measured by the curvature of space.
Quantum field theory considers the vacuum ground state not to be completely empty, but to consist of a seething mass of virtual particles and fields. These fields are quantified as probabilities—that is, the likelihood of manifestation based on conditions. Since these fields do not have a permanent existence, they are called vacuum fluctuations. In the Casimir effect, two metal plates can cause a change in the vacuum energy density between them which generates a measurable force.
Some believe that vacuum energy might be the "dark energy" (also called Quintessence) associated with the cosmological constant in general relativity, thought to be similar to a negative force of gravity (or antigravity). Observations that the expanding universe appears to be accelerating seem to support the cosmic inflation theory—first proposed by Alan Guth in 1981—in which the nascent universe passed through a phase of exponential expansion driven by a negative vacuum pressure (although the energy density is positive.)
Read more about this topic: Energy Density
Famous quotes containing the words empty space, energy, empty and/or space:
“Of all the diversions of life, there is none so proper to fill up its empty spaces as the reading of useful and entertaining authors.”
—Joseph Addison (1672–1719)
“The principle of avoiding the unnecessary expenditure of energy has enabled the species to survive in a world full of stimuli; but it prevents the survival of the aristocracy.”
—Rebecca West (1892–1983)
“I wish my deadly foe no worse
Than want of friends, and empty purse.”
—Nicholas Breton (c.1545–1626)
“The woman’s world ... is shown as a series of limited spaces, with the woman struggling to get free of them. The struggle is what the film is about; what is struggled against is the limited space itself. Consequently, to make its point, the film has to deny itself and suggest it was the struggle that was wrong, not the space.”
—Jeanine Basinger (b. 1936)