Vacuum energy

Vacuum energy is an underlying background energy that exists in space even when the space is devoid of matter (free space). The concept of vacuum energy has been deduced from the concept of virtual particles, which is itself derived from the energy-time uncertainty principle. The effects of vacuum energy can be observed in various phenomena such as spontaneous emission, the Casimir effect, the van der Waals bonds 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 centimeter of free space has been estimated to be 10−15 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 10107 Joules per cubic centimeter.

The existence of vacuum energy is also sometimes used as theoretical justification for the possibility of free energy machines. It has been argued that due to the broken symmetry (in QED), free energy does not violate conservation of energy, since the laws of thermodynamics only apply to equilibrium systems.

In the Halo universe
Forerunner reaction drives utilize vacuum energy use vacuum energy to expel virtual neutrons from the rear of the vessel, giving it propulsion.

List of appearances

 * Halo: Cryptum