If there is a container, which is divided into two parts, A and B. There are some hot gases on the left and some low temperature gases with the same composition on the right. After a while, the high-temperature gas transfers heat to the low-temperature gas, and the temperature on the two sides tend to be the same. This change belongs to the increase of entropy, which is consistent with the second law of thermodynamics. Heat transfer from a low temperature object to a high temperature object is an entropy reduction. How can this system reduce entropy?

In order to solve this problem, Maxwell invented a goblin called Maxwell demon. He said that this little goblin is very clever, it can track the whereabouts of each molecule, and can identify their respective speed. Molecules in an air-filled container with a uniform temperature have non-uniform rate of motion, but the average velocity of molecules is uniform. Now suppose there is a small hole in the container boundary, and then imagine that Maxwell's demon can open or close that hole so that fast molecules run from A to B, while slow molecules run from B to A. In this way, without power consumption, the temperature of B increases, the temperature of A decreases, and there is a contradiction with the second law of thermodynamics. So symmetry breaking occurs, and as the entropy decreases, the world can evolve now.

Is Maxwell's demon the real cause of the evolution of the world? Impossible, because it consumes external information even if it does not consume energy when it creates non-equilibrium. The speed of movement of molecules is a kind of information. So it is still a worldwide puzzle to explain the evolution of the world.

So is there a Maxwell demon that does not consume energy and foreign information?  Although the asymmetry of energy is not likely to occur spontaneously, the asymmetry of matter may occur spontaneously. Boltzmann tells us that the essence of energy symmetry is that the structure of matter tends to be symmetrical.

If there are two small balls A and B in two adjacent boxes and the partition in the middle of the box is removed, the symmetrical state has two possible distributions, one is A on the left with B on the right, the second is B on the left with A on the right. There is only one distribution of the two balls on the left or right side together, which is a state of symmetry broken. Therefore, the probability of occurrence of a symmetric state is large, and the probability of a symmetry broken state is small. Boltzmann defines the logarithm of this probability as entropy.

In the example above, if there are two balls in the box, they may be on one side, or they may be evenly distributed on both sides. The possibility of even distribution is big, and the possibility of being on one side is small. However, if we assume that there is an oxygen atom on each side of the box, they will certainly not be on two side and they will soon be combined into one oxygen molecule. In other words, the state with the highest probability we said is not the stable state, and the state of symmetry br