# If a system has an internal energy equal to 0, does this mean it doesn't exist?

Enthalpy is a measure of energy in a thermodynamic system:

It includes the internal energy, which is the energy required to create > a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure.

Source: Wikipedia / Enthalpy

My question is related to internal energy not enthalpy.

• That depends on your precise definition of internal energy and what you mean by "exist", but e.g. an ideal gas at zero temperature would probably have zero internal energy. – ACuriousMind Feb 3 '16 at 16:31
• It depends on what you mean by "system". One could argue that a mechanical system such as a point mass, or a solid, has zero internal energy as it has no microscopic internal structure. All its energy is in the form of marcroscopic mechanical energy. – Dimitri Feb 3 '16 at 16:33
• null internal energy is just a reference. In most thermodynamics systems ( try to account of the energy vacuum ) , it is impossible to calculate the total internal energy ( wiki ). – user46925 Feb 3 '16 at 16:36
• Complete vaccum has no internal energy. But still, you may consider it as a system which can have coordinates.Doesn't complete vaccum exist!! – Anubhav Goel Feb 3 '16 at 16:50
• Also, remember that only $\mathrm dU$ is defined: $U$ is always underdetermined (you can shift $U\to U+\text{const}$ for any constant, without changing the physics). – AccidentalFourierTransform Feb 3 '16 at 19:00