Life as a manifestation of entropy

“There is nothing over which a free man ponders less than death; his wisdom is, to meditate not on death but on life.” - Spinoza

In 1943 Erwin Schrödinger the famous Nobel laureate, also known for his inability to determine whether a cat is alive or dead, wrote a small book called What is Life?, in which he attempted to draw together the fundamental principles of physics and biology. He noted that life is comprised of two fundamental processes “order from order” and “order from disorder”.

The first notion is not so surprising, as life itself is an ordered structure with the only purpose to replicate itself, to create more of its ordered body. But the latter notion is more interesting. At first glance living systems seem to defy the second law of thermodynamics as it states that, within closed systems, entropy should be maximized and disorder should reign. Life itself with its structured being, however, is the antithesis of such disorder.

The first & second laws of thermodynamics

To understand why the second law of thermodynamics is so important and dazzling, first, we have to look at the first law: the first law of thermodynamics states that energy cannot be created nor destroyed and that despite the constant transformations that energy is undergoing in nature, the total energy within a closed system remains unchanged. But it doesn’t state that the quality of energy in a closed system will remain unchanged. This will be important as we get to the second law.

The second law is best known as the principle that rules out perpetual motion, resulting from the original question “how efficient can we make steam engines?”

Scientists in the 19th century discovered that, when trying to convert one form of energy (e.g. heat) into another form of energy (e.g. motion), they were never able to make the transfer complete, there was always some energy lost.

Same as money exchange, when you transform money from one currency to the other, the bank snips a small amount in the process. No money was printed nor destroyed, but you have less money than before. Some of your money dissipated to the bank.

Because of the first law of thermodynamics, researchers sought a means of quantifying and explaining this energy transaction fee. This led them to posit a strange quantity, not directly observable: entropy.

Entropy measures the disorder of a system in terms of the arrangements of molecules. They have found that in any process where energy goes from one state to another, entropy tends to increase.

This tends to increase part sparked a firestorm between physicists, with one side who took Clausius’s view that this quantity is a subject to absolute and deterministic rules, therefore it must increase, and on the other side who took Boltzmann’s position, that in thermodynamics quantities were statistical averages inside the closed system, and that entropy probabilistically speaking, most likely increases.

Boltzmann eventually won the argument, and entropy is best thought of as the set of all possible states of a thermal system. And since heat flows from warm to cold, a system not in equilibrium is in flux, it is in constant change. This means that the number of possible states in which the system could be found increases with time.

Dissipative systems

But what does this mean? These don’t suggest anything, what will happen in the universe, nor that life is an inherent result of entropy. That’s what George N. Hatsopoulos and Joseph Keenan proposed, a unified theory of thermodynamics which not only tells what the universe can’t do but what will it do:

“When an isolated system performs a process after the removal of a series of internal constraints, it will reach a unique state of equilibrium: this state of equilibrium is independent of the order in which the constraints are removed.”

Why this statement is so important, that, unlike the earlier statements which show that all real processes are irreversible, this dictates a direction and an end state for all real processes. This statement tells us what systems will do.

This allows strange open systems to emerge in the universe. In non-equilibrium systems, who through their exchange of energy with the outside world, can maintain themselves for a period of time away from thermodynamic equilibrium in a locally reduced entropy steady state. This is done at the cost of increasing the entropy of the larger global system in which this system is embedded, thus following the second law that overall entropy must increase. This was famously formulated by Ilya Prigogine in his research paper Theory of dissipative structures in 1973.

Prigogine also showed that dissipative systems self-organize through fluctuations and small instabilities which led to irreversible and new stable system states. An example of which are the Bénard cells, occurring in a plane of fluid heated from below, in which the fluid develops a regular pattern of convection cells.

So no longer is the emergence of self-organizing structures a surprise, but rather it is an expected response of a system as it attempts to resist and dissipate externally applied gradients which move the system away from equilibrium.

The development of temperature gradients (difference) between the warm earth and the cooler overlying atmosphere results in highly organized convection cloud patterns which reduce the troposphere temperature gradient. The destructive power of tornadoes and hurricanes is a manifestation of the ability of these self-organizing structures to rapidly dissipate strong temperature gradients.

Life as the ultimate form of dissipative structures

Boltzmann recognized the apparent contradiction between the thermodynamically predicted randomized cold death of the universe and the existence of life in nature by which systems grow, complexify and evolve, all of which reduce their internal entropy. He also realized that the gradient on earth, caused by the energy provided by the sun, drives the living process and suggested a Darwinian-like competition for entropy in living systems.

As we have seen Boltzmann’s ideas were further explored by Schrödinger in What is Life?. He, like Boltzmann, was intrigued. He also noted that some systems, like life, seem to defy the classical second law of thermodynamics. However, he also recognized that living systems are open and not adiabatic closed boxes.

An organism stays alive in its highly organized state by taking energy from outside itself, that is from a larger encompassing system, and processing it Ito produce a lower entropy state within itself. Life can be viewed as a far-from-equilibrium dissipative structure that maintains its local level of organization, at the expense of producing entropy in the larger system it is part of.

If we view the earth as an open thermodynamic system with a large gradient imposed on it by the sun, the thermodynamic imperative of the restated second law is that the system will strive to reduce this gradient by using all physical and chemical processes available to it. Self-organizing processes are an effective means of reducing gradients.

Life exists on earth as another means of dissipating the solar induces gradient and as such is a manifestation of the restated second law of thermodynamics. Much of this dissipation is accomplished by the plant kingdom through photosynthesis.

The origin of life

The origin of prebiotic life is the development of another route for the dissipation of induced energy gradients. Life with its ability to replicate itself and reproduce ensures that these dissipative systems continue, and it has evolved strategies to maintain these dissipative structures in the face of fluctuating physical environment. The gene enables these living dissipative systems to continue without having to restart this dissipative process through stochastic events.

I suggest that living systems are sophisticated natural dissipative systems whose Aristotelian final cause is the second law of thermodynamics. But I should add that the second law is a necessary but in itself not a sufficient condition for life.

The origin of life should not be seen as a single isolated event, rather a continuous and evolving class of processes whose goal is the dissipation of energy gradients.

It should be viewed as the most sophisticated dissipative system from physical to chemical to autocatalytic to living systems. Autocatalytic chemical dissipative systems are the precursor and backbone of self-reproducing macromolecular species with a thermodynamic vision of the origin of life.

Presumably, at the dawn of life, in the structureless soup of the Panthalassa (“all-sea” surrounding Pangea), huge energy gradients induced by the sun, facilitated the pre-biological self-organization of macromolecular structures such as nucleic acids and proteins. Which then formed the first “living” structure the self-replicator, which were structures of proteins capable of copying themselves with the help of the vast amounts of free-floating material in the ocean, and high energies induced by the sun.

Seen from a distance, the law of large numbers makes this process seem an inevitable event, given the presence of certain matter with autocatalytic properties under the maintenance of quasi-infinite energy flow necessary to compensate for the steady production of entropy.

Summing up

In this lengthy post, I have tried to impose a rather controversial explanation for the origin of life, relying on the restatement of the second law of thermodynamics from the cliché of “entropy increase” into a statement that describes systems undergoing processes so that they reach a unique state of thermodynamical equilibrium.

I drew from the work of Schrödinger, Boltzmann, Hatsopulos & Keenan, and Prigogine, to allow for a discussion of a system in non-equilibrium. We have overcome the difficulty of describing these non-equilibrium systems in the terms of entropy. And suggested that systems will take advantage of all available means to resist and dissipate the gradients responsible for the non-equilibrium state. Furthermore, the emergence of coherent self-organizing structures is the expected response of systems as they attempt to dissipate the external gradients that are moving them away from equilibrium.

Living systems are not only permissible under the second law of thermodynamics, but the law itself is what mandates living processes and is a necessary but not sufficient cause for life itself.

TL;DR

Life is not in contradiction, but rather the result of entropy. Living systems are an efficient way to transform high energies into lower energy states with higher entropy, thus increasing the overall entropy in the Universe faster.