In physics, the zero-point energy (often referred to as the vacuum energy) is the lowest possible energy a system can have. The zero-point energy is an underlying background energy that exists in the space around us even when devoid of matter (known as free space).

After removing all air, heat and light these is still a background energy remaining. This zero-point energy remains even when all other energy is removed from a system.

In simple terms it has been said that there is enough zero-point energy in a volume the size of a cup of coffee to boil away all of Earth’s oceans.

This behaviour is demonstrated by, for example, liquid helium. As the temperature is lowered to absolute zero, helium remains a liquid, rather than freezing to a solid, owing to the irremovable zero-point energy of its atomic motions.
(Increasing the pressure to 25 atmospheres will cause helium to freeze.)

Zero-point effects can be observed in various phenomena (such as spontaneous emission, the Casimir effect, the Van-Der Waals bonds, or the Lamb shift).

For every possible color of light, that includes the ones we can’t see, there is a non-zero amount of that light. Add up the energy for all those different frequencies of light and the amount of energy in a given space is enormous, even mind boggling, ranging from 10^36 to 10^70 Joules/m3.

In simple terms it has been said that there is enough energy in the volume the size of a coffee cup to boil away all of Earth’s oceans.

There is growing interest concerning the possibility of tapping zero-point energy and many claims exist of ”over unity devices” (gadgets yielding a greater output than the required input for operation) driven by zero-point energy. In spite of the dubious nature of these claims (to date no such device has passed a rigorous, objective test), the concept of converting some amount of zero-point energy to usable energy cannot be ruled out
in principle.

Zero-point energy is not a thermal reservoir, and therefore does not suffer from the thermodynamic injunction against extracting energy from a lower temperature reservoir.

In 1993 Cole and Puthoff published a thermodynamic analysis, ”Extracting energy and heat from the vacuum”, in which they concluded that ”extracting energy and heat from electromagnetic zero-point radiation via the use of the Casimir force” is in principle possible without violating the laws of thermodynamics.

The Casimir Effect

The most straight-forward evidence for vacuum energy is the Casimir effect. Get two metal plates close enough together and this vacuum energy will push them together. This is because the plates block out the light waves that are too big to fit between the plates.

Eventually you have more waves bouncing on the outside than from the inside, the plates will get pushed together from this difference in light pressure. This effect has been experimentally demonstrated.

The Casimir force was not measured to high precision until the mid 1990s, when measurements by S. Lamoreux at the University of Washington verified Casimir’s predictions to within five percent in the size range of a few microns.
It has since been verified even more precisely, by U. Mohideen at the University of California at Riverside, again in agreement with Casimir’s formula. Moreover the Casimir force (also called Casimir effect) has become relevant to micro-electro-mechanical structures in which it is both a problem (termed ”stiction”) and a possible mechanism for control.

The Casimir force is widely cited as evidence that underlying the universe there must be a sea of real zero-point energy. This argument follows from Casimir’s analysis and prediction. It is not necessarily true, however. It is perfectly possible to explain the Casimir effect by taking into account the quantum-induced motions of atoms in each plate and examining the retarded potential interactions of atoms in one plate with those in the other.