CSW's Ideal Gas 

The physics of this twodimensional gas (below) are reversible. Time can be run forwards and backwards. Energy is perfectly conserved. Please press 'GO'. Chris Wallace showed that this artificial gas obeys many of the properties of real gases – see the Feathers on the Arrow of Time chapter in the "MML book." EntropyThe entropy that is displayed is the entropy of the velocity distribution. It can be seen that from a randomly selected state, the entropy is equally likely to be higher or lower in the next (or previous) state. However, if the gas is observed to be in a low entropy (ordered) state at time t, it will almost certainly be in a higher entropy state at time t+1, and the timereversibility implies that it was almost certainly in a higher entropy state at time t1. Determinism: 11 State TransitionsThe physics of the gas are deterministic. Therefore the states will cycle  over a v e r y l o n g period, N. So from this point of view the entropy of every state is the same, log(N). © C.S.Wallace & L.Allison, 2007, 2017. (The figures in the "MML Book" that illustrate the gas were generated by a C programme – which cannot be run via the web.) 

