The second law of thermodynamics, formulated in 1850 by Dr. Rudolf Clausius, professor of physics at University of Zurich, is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system. From the state of thermodynamic equilibrium, the law deduced the principle of the increase of entropy and explains the phenomenon of irreversibility in nature. Entropy is a measure of the energy in a thermodynamic system not available to do useful work, the tendency for a system to become less structured. In nature the over-all entropy of a complete, or closed, system must spontaneously occur. However, in the case of interacting sub-systems of a closed system, some sub-systems may gain entropy, while other sub-systems may lose entropy. For example, a fundamental axiom of thermodynamics is that when heat flows from subsystem A to subsystem B, the entropy of A decreases and the entropy of B increases. The statement that an increase in order can only occur as the result of a directional mechanism or perturbation is misleading. In Nobel-laureate physicist Erwin Schrödinger’s book from 1944 What is Life?, Shrodinger theorizes that life, contrary to the general tendency dictated by the Second law of thermodynamics, decreases or maintains its entropy by feeding on negative entropy. In 1964, Dr James Lovelock, professor of chemistry at University of London, and a consultant to NASA's life detection project, when asked how he would detect life on Mars stated that he would search for "entropy reduction" as a basic characteristic of life.
When used in thermodynamics, probability means that some specific change will occur. Probability is related to the thermodynamic concept of irreversibility. An irreversible physical or chemical change will not spontaneously reverse itself without some perturbation in the surrounding conditions. Irreversible changes have a high degree of probability. The probability of an irreversible change spontaneously reversing itself without an outside perturbation is zero. Further, when change is said to be irreversible, we are stating that the change will not spontaneously reverse itself without some perturbation in the surrounding conditions. Irreversible does not suggest that the condition, or thermodynamic equilibrium, cannot be reversed by some external means.
Moreover, a change that has a high degree of probability under one set of conditions may have a very low degree of probability under a different set of conditions. For example, if the temperature drops below freezing, the probability of water becoming ice is very high, and the reaction from water to ice is thermodynamically irreversible. If the surrounding temperature rises above the freezing point, the probability of water becoming ice, or remaining as ice, is zero. Under these conditions the backward reaction of ice to liquid water is also thermodynamically irreversible.
Failure to understand that in thermodynamics probabilities are not fixed entities has led to a misinterpretation that is responsible for the false belief that the second law of thermodynamics does not permit order to spontaneously arise from disorder, or as Shrodinger would name it, “Negative entropy”. Many examples in nature exist where order does arise spontaneously from disorder, where sub-systems within the closed system exhibit negative entropy. Snowflakes with their six-sided crystalline symmetry are formed spontaneously from randomly moving water vapor molecules. Salts with precise planes of crystalline symmetry form spontaneously when water evaporates from a solution. Seeds sprout into flowering plants, eggs develop into chicks, and aged skin or other organs can become more orderly and structured when acted upon by an outside perturbation.
Thermodynamics is an exact science, indeed this is why there are four laws of thermodynamics, that is based on specific mathematical concepts. The laws are not easily explained using qualitative metaphors, but are best understood as the relationship between probability theory of stochastic processes and the second law. Entropy is a mathematically defined entity that is the fundamental basis of the second law of thermodynamics and all of the 2nd laws’ engineering, biological, physical and chemical ramifications. The mathematical relation between entropy neither precludes the possibility of order spontaneously arising from disorder, nor negative entropy arising from external forces. In describing the laws of thermodynamics we often refer to a "closed system." A closed system is a specific entity or object or region in space and time that can be evaluated in terms of its thermodynamic properties and possible changes. The system can be defined as many things, such as an ice cube, a steam turbine, a man within a defined environment, or even the entire universe itself, and then that defined system can be thermodynamically analyzed. As an example, when using classical thermodynamics to describe events that are not subatomic, such as ion currents across a cellular membrane, we can describe the statistical distribution of particles using the Boltzman Equation described by Dr. Ludwig Boltzman in the late 1800s when he was professor of mathematical physics at the University of Graz. In such a system, the distribution of ion particles will flow across the membrane in such a way as to achieve equilibrium, i.e. an equal number of particles on each side of the membrane such that no work can be performed once equilibrium is achieved. The Boltzmann equation, a first-order differential equation based on Hamiltonian Mechanics, was developed to describe the dynamics of an ideal gas such that:
where ƒ represents the distribution function of single-particle position and momentum at a given time, where F is a force, m is the mass of a particle, t is the time, and v is an average velocity of particles.
If we think of aging, the process is one that obeys the Second Law of Thermodynamics. Considering the body, or a portion of the body, perhaps a cell, as a closed system, then that defined closed system will naturally obey the principles of entropy, and tend towards a state of equilibrium. Equilibrium will bring the closed system, such as a cell, to a point where there is no longer organization and hence there is no longer a chance for the system to create work from the inherent energy. The lack of structure within the closed system and the inability to do work is the death of the cell.
However, if we think of the cell not as a closed system, rather, if we think of the cell as a sub-system within the overall construct of a closed-system, then the cellular subsystem can achieve negative entropy if the other sub-system can support positive entropy.
Therefore life can be thought of as negative entropy. On the other hand, aging is considered by some as no longer an unsolved biological problem and simply positive entropy. This means the understanding of the biological cause of aging is the same as the cause of nonbiological aging and is attributable to the second law of thermodynamics, to increased entropy. As discussed above, all molecules, including biological molecules, dissipate energy, losing structural integrity and functional capacity, headed for a state of equilibrium. Our bodies have sub-systems for enormous repair capacity, which evolved to repair dysfunctional molecules. Some will argue that the repair systems function only until reproductive maturation, after which the repair mechanisms break down and the molecules recoil to a high entropy state. Allowing the repair to occur until the time of reproductive maturation means the species will procreate and survive. However, the accumulation over time of dysfunctional molecules in the high entropy state leads to the properties of aging at the clinical level that we all recognize, and eventually leads to death.
While the laws of physics are inevitable, some people have proposed changing the parts as they wear out. Others argue if you change the parts, the original is no longer the original. However, one may argue that a person naturally changes anyway during maturation, and if you don’t die, you’re really the same person; just the same as when you change during the natural maturation process; one could think of biological replacement or enhancement as an extended maturation process. In this way, the entropic values of the person, a sub-system, decreases, but, of course, the replacement procedure would increase the entropy of the complete system. And, procedures using adult stem cells for tissue repair drive negative entropy in the tissue being repaired (a sub-system), but increase the overall entropy of the system, or the sub-system beyond the tissue that is being repaired. Moreover, while stem cell releasing molecules (SRM) will decrease entropy in the target tissue (a thermodynamic sub-system) that the SRM repairs or rejuvenates, the overall entropy of the system will increase. This is because of the energy used to manufacture the SRM, thus leading to that subsystem to equilibrate and increase in entropy.
The bottom line is that we can use technology, for example using stem cell therapeutics or SRM technology, to produce negative entropy in a subsystem, i.e. human tissue, but the entropy of the overall system will increase. Therefore age management is a means for helping to drive a subsystem, the aging body, towards a more negative entropic state within a world where the inevitable second law of thermodynamics runs its course.