It seems that the more I study the "aether" issue, the less I know.
Vacuum energy is an underlying background energy that exists in space
throughout the entire Universe.
[I suppose this is the background energy from the Big Bang]
One contribution to the vacuum energy may be from virtual particles,
which are thought to be particle pairs that blink into existence and then
annihilate in a timespan too short to observe.
They are expected to do this everywhere, throughout the Universe. Their
behavior is codified in Heisenberg's energy-time
uncertainty principle. Still, the exact effect of such fleeting bits of energy
is difficult to quantify.
The effects of vacuum energy can be experimentally observed in various
phenomena such as spontaneous emission,
the Casimir effect and the Lamb shift, and are thought to influence the
behavior of the Universe on cosmological scales.
Using the upper limit of the cosmological constant, the vacuum energy in a
cubic meter of free space has been estimated to be 10-9 Joules.
 However, in both Quantum Electrodynamics (QED) and Stochastic
Electrodynamics (SED), consistency with the
principle of Lorentz covariance and with the magnitude of the Planck Constant
requires it to have a much larger value of 10113 Joules per cubic meter.
Quantum field theory states that all fundamental fields, such as the
electromagnetic field, must be quantized at each and every point in space.
A field in physics may be envisioned as if space were filled with
interconnected vibrating balls and springs, and the strength of the field were
like the displacement of a ball from its rest position. The theory requires
"vibrations" in, or more accurately changes in the strength of, such
a field to propagate as per the appropriate wave equation for the particular
field in question. The second quantization of quantum field theory
requires that each such ball-spring combination be quantized, that is, that the
strength of the field be quantized at each point in space.
Canonically, if the field at
each point in space is a simple harmonic oscillator, its quantization places a
quantum harmonic oscillator at each point. Excitations of the field
correspond to the elementary particles of particle physics. Thus, according to
the theory, even the vacuum has a vastly complex structure and
all calculations of quantum field theory must be made in relation to this model
of the vacuum.
The theory considers vacuum to implicitly have the same properties as a
particle, such as spin or polarization in the case of
light, energy, and so on. According to the theory, most of these properties
cancel out on average leaving the vacuum empty
in the literal sense of the word. One important exception, however, is the
vacuum energy or the vacuum expectation value of the energy.
The quantization of a simple harmonic oscillator requires the lowest possible
energy, or zero-point energy of such an oscillator to be:
Summing over all possible oscillators at all points in space gives an infinite
quantity. To remove this infinity, one may argue
that only differences in energy are physically measurable, much as the concept
of potential energy has been treated in classical mechanics for centuries.
This argument is the underpinning of the theory of renormalization. In all
practical calculations, this is how the infinity is handled.
Vacuum energy can also be thought of in terms of virtual particles (also known
as vacuum fluctuations) which are created and destroyed out of the vacuum.
These particles are always created out of the vacuum in particle-antiparticle
pairs, which in most cases shortly annihilate each other and disappear.
However, these particles and antiparticles may interact with others before
disappearing, a process which can be mapped using Feynman diagrams.
Note that this method of computing vacuum energy is mathematically equivalent
to having a quantum harmonic oscillator at each point and,
therefore, suffers the same renormalization problems.
Additional contributions to the vacuum energy come from spontaneous symmetry
breaking in quantum field theory.
[Roger Clough], [rclo...@verizon.net]
"Forever is a long time, especially near the end." - Woody Allen
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