Entropy

Entropy is one of several key entities in discribing energy obtained from vacuum reactions. Other entities are the Aharonov-Bohm effect, Casimir effect, Zitterbewegung, Micro cavity, etc.. 

Entropy is a physical state function that describes the increase in order of disorder. Entropy is found to be very useful in calculating the work done by thermal machines where the 2nd law of thermodynamics say that heat can only go from a higher temperature to a lower temperature, not in the other direction.

Analogy:

1. Birds resting on a telephone line are highly coherent and have low entropy
- all birds have the same point vector (the birds rests on the telephone line to view the same direction)
- all birds have the same vector length (the birds are of the same species)
- all birds have the same moment of inertia (no moment of inertia when resting)

2. Swirling flocks of birds are less coherent and have a higher entropy
- the flock acts as if they were a unit
- flocks twist and change shape in the sky (moment of inertia)
- there is no leader but each bird follows simple rules
- each bird reacts to its six or seven nearest neighbors (topological interaction, not fixed distance).
- creates a scale-invariant correlation, where changes propagate directly throughout the flock.
- produces for an observer flowing, wave-like patterns (an illusion to an observer).
- birds fly at uniform speeds, with apparent accelerations which are optical illusions from the observer's 2D perspective.

3. Finally, individual randomly flying birds are incoherent and have the highest entropy.