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Is life against the second law of thermodynamics?

Joseph X. Zhou's picture

The second law of thermodynamics is ubiquitous, which can explain many phenomena from the ink diffusion in the water and the heat conduction from the hot to the cold etc. Or simply put, order is always decreasing in nature. Even an ancient Chinese philosopher, Laozi once said “ It is the nature’s law nature's law to decreases those who have more than they need and increases those who need more than they have. it is not so with man. Man decreases those who need more than they have and increases those who have more than they need”. It seemed that nature always destroys the order and evens out everything in the world. Then how could life maintain its order? Why life is so unique? What are the differences between the matters with life and without? Order is important for life because losing order of life means that the atoms made of life will mix up with others in the universe. It is nothing but death.

The question can be best answered by an experiment given in Nelson’s classic book “Biological physics”. We have a glass tube with two freely sliding pistons and a membrane which only allow the water molecules to pass. It is full of water between two pistons. If we put some sugar in the right chamber of the tube, what will happen?


At beginning nothing happens except that we see the sugar gradually melts in the water and disappears. Then something strange happens: a mysterious force will slowly push the pistons to the right. If we put some small weight on the left end, it will left up the weight. i.e. it can do work. It seemed that we get some work done from nowhere.

However, when we look more closely, we found that the sugar only occupies half of space at the beginning and gradually it occupies the whole space as water flows through the membrane. The system loses its order and absorbs the heat in the air to do honest mechanical work. It is called the entropy force, which is actually the molecular driving force existed everywhere in the cell. This is one of the most important forces which underpin every form of life on earth.

Interestingly, the whole system can be turned around. If we put a heavy weight on the left side at the end of last experiment, the pistons will move to the left and the water will flow back to the left side as well, the sugar concentration will be higher and higher, and the whole system will gain order again. Here the mechanical energy is changed to be heat which dissipated into air around the tube. So if there is an energy flow from the higher order (mechanical one) to the lower order (heat), the system can gain order through the energy flow.

Aha, there we are. Life is NOT against the second law of thermodynamics. Neither is it an entropy-decreasing process which is defined by somebody as the essential feature of life. If we put the life and its environment together, the total entropy is still increasing. When we eat the food, the higher order chemical energy is changed to be lower order heat (Some are stored in the universal energy currency of life - ATP and they finally will be changed to be heat as well), we human being maintain our order of life

Life goes beyond the  second law of thermodynamics

However, the story does not end here. If so, our life is just a biological car in a molecular sense, which could burn the fuel and do some useful work. Then life is mechanical and boring. The good news is, far from that, life is much more fascinating. For example, no matter how expensive gasoline you fill into your car, your Volkswagen will never be automatically changed to a Merced-Benz. There is no mechanical system can intrinsically increase its order and gain its complexity (Crystal can grow to be very large. But its periodic structure is simple). If we look at the history of life, which evolved from a single-cell organism, to multi-cell ones; from invertebrates to vertebrates, from fish, birds to primates and finally to human beings. Life not only maintains its order, it increases its order and complexity dramatically in the past 4 billion years. If we look back what leads us to the second the law of thermodynamics, we find that we couldn’t explain why only a rock hits the mud and the mud gets warm, but we never find that the mud pops up the rock and gets colder afterwards even it perfectly agrees with the energy conservation principle. Here we have a perfect parallel case:  if we put the environment and life together, we only see that heat (or lower order energy) increases while life evolves to the higher order and complexity; we never see that the higher order energy in the environment increases while life degenerates and lose its order and mix up with the world totally, even it also agrees with the second the law of thermodynamics totally.

Maybe this could be a new law of life, which is predicted by Schrodinger:
“Living matter, while not eluding the 'laws of physics' as established up to date, is likely to involve 'other laws of physics' hitherto unknown……. from all we have learnt about the structure of living matter, we must be prepared to find it working in a manner that cannot be reduced to the ordinary laws of physics. And that not on the ground that there is any 'new force' or what not, directing the behaviour of the single atoms within a living organism, but because the construction is different from anything we have yet tested in the physical laboratory. We must therefore not be discouraged by the difficulty of interpreting life by the ordinary laws of physics. For that is just what is to be expected from the knowledge we have gained of the structure of living matter. We must be prepared to find a new type of physical law prevailing in it.”

In conclusion, Schrodinger just pointed out that the new law will NOT be against Newton’s law, or law of Quantum Mechanics, or any other law of physics. Instead, it could be some new law due to the complex and unique structure of the form of life. The key word of the new law could be Evolution, Order and Complexity.

This is truly a difficult problem. There are some intensive research in this field: 

1) System study of the dynamic of an adaptive complex system. There are already some examples which show the order of a network can grow if certain rules are set. I would like write some articles about it later.

2) Chaotic and non-linear many-body dynamics. How to generate order from a chaotic system? Is there some universal rule to cause phase transition in chaos?

3) Mathematical Evolution theory and the mechanism to explain the order accumulation in nature.

They could lead us to some answers as well as they could be totally wrong. That’s the reason why research is so fun.  Physics does not see the beginning of its end; instead, it is just the end of the beginning.


zhan-sheng guo's picture

it is very interseting

Thank you for writing this. Your previous post about Andrew Wiles was very much appreciated as well.

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