Entropy of a gas. Numerical simulation of sixteen gas atoms (green spheres) moving within a box. The plot in the background shows how often a certain number of atoms is located in the left side of the box. The most frequent case (maximum entropy) is when one half of the atoms are in the left side, the other half in the right side of the box. The most unusual case (lowest entropy) is the situation where all atoms are in one side of the box. With time, the distribution (red) of the atoms approaches a Gaussian curve.