Fleeting electromagnetic waves and virtual particles that pop into and out of existence at a whim

In quantum field theory, the vacuum state is the quantum state with the lowest possible energy; it contains no physical particles, and is the energy of the ground state. This is also called the zero point energy; the energy of a system at a temperature of zero. 

But quantum mechanics says that, even in their ground state, all systems still maintain fluctuations and have an associated zero-point energy as a consequence of their wave-like nature. Thus, even a particle cooled down to absolute zero will still exhibit some vibrations.

Liquid helium-4 is a great example: Under atmospheric pressure, even at absolute zero, it does not freeze solid and will remain a liquid. This is because its zero-point energy is great enough to allow it to remain as a liquid, even if a very cold one. 

Everything everywhere has a zero-point energy, from particles to electromagnetic fields, and any other type of field. Combine them all together and you have the vacuum energy, or the energy of all fields in space. This would seem to imply that a vacuum state -- or simply vacuum -- is not empty at all, but the ground state energy of all fields in space, and may collectively be called the zero point field. 

The vacuum state contains, according to quantum mechanics, fleeting electromagnetic waves and virtual particles that pop into and out of existence at a whim.


https://www.huffingtonpost.com/peter-baksa/zero-point-field_b_913831.html