There are significant features of living beings which distinguish them from all else in the known universe and which play a major role in human behaviour. To understand these, it is necessary to enter the realm of physics.
The explanation begins with the concept of time. Our human experience of time is that we move through it in one direction from the past to the present. This is known as “the arrow of time”. However, with two exceptions, the fundamental laws of physics do not dictate the direction of travel. They apply equally whether it is from the past to the future or from the future to the past.
The first exception is the second law of thermodynamics. The first and second laws of thermodynamics were developed in the 1850’s based on the work of Rankine, Clausius and Lord Kelvin. The first law states that energy cannot be created or destroyed and that the total amount of energy in the universe is constant. The second law states that, in a closed system, i.e., one into which energy cannot enter and from which it cannot escape, as energy is transformed from one state to another, some is wasted as heat. Importantly, however, the second law also states there is a natural tendency for any isolated system to degenerate from a more ordered, low entropy state to a more disordered, high entropy state.
An important feature of the second law is that it defines direction in time and, thus, the arrow of time. The degeneration from a low entropy state to a high entropy states takes place as we travel through time from the past to the future. Were we to travel from the future to the past then the reverse would occur.
In the late 19th Century, the Austrian physicist Ludwig Boltzmann explained that entropy was a measure of the ways in which atoms and the energy they carry can be arranged and the probability of that arrangement. If atoms are arranged in an organized system, for example a crystal lattice, then they are in a low entropy state. However, if they are arranged in a more random and unstructured way, for example in a gas, then they are in a high entropy state. However, the probability of atoms being arranged in a crystal lattice is much lower than the probability of them being arranged as a gas. Thus, an orderly system has low probability and low entropy, a disorderly system high probability and high entropy. Entropy and disorder always increase in the direction of the arrow of time because the probability of a high entropy system is greater than that of a low entropy system.
Professor Brian Cox gives an excellent example in this Youtube video https://www.youtube.com/watch?v=uQSoaiubuA0. In summary, the random arrangement of sand particles in a heap is far more likely than an arrangement that forms a sandcastle. So, as time progresses it is far more likely that a sandcastle will decay into a heap of sand than a heap of sand will arrange itself into a sandcastle.
Boltzman also suggested that, at some time in the distant past, the universe was in a low entropy state. This was dubbed the “Past Hypothesis” by Richard Feynman. However, Boltzman was unable to explain why this is the case and, to this day, this remains one of the unsolved problems of physics.
The second exception among the fundamental laws of physics is causality. In the direction of the arrow of time, a cause always precedes its effect and not vice versa. Were it possible for an effect to precede its cause the world would abound with time-travel paradoxes.
Attempts have been made to link, entropy, probability, and causality into a unified theory, but they have met with little success. Most authors believe that there is an undiscovered law associated with the initial and final states of the universe. Others believe that the law is associated with the nature of time and this defines the initial and final states. However, as matters stand at present, we simply have no explanation.
In 1944, another Austrian physicist, Erwin Schrodinger, raised an apparent paradox in his book “What is Life” which can be downloaded at www.whatislife.ie/downloads/What-is-Life.pdf. This was not his famous “Cat” paradox. Rather it is the tendency for living systems to become more organized as time progresses, which appears to contradict the second law of thermodynamics. Schrodinger thought that the basis of living matter evading decay to equilibrium was a “code-script” in the chromosomes of the organism “which determined the entire pattern of the individual’s future development and its functioning in the mature state”. At that time, DNA was yet to be discovered but Schrodinger’s work was significant in inspiring the necessary research.
There is no real paradox, however, because living beings are not closed systems. Rather they use free energy from the sun. In striving to maintain their integrity they increase entropy in their surroundings, and, in total, nett decay still occurs. Nevertheless, this anti-entropic behaviour is a distinctive feature of life.
Another distinctive feature of life, or of reasoning beings at least, is associated with causality. In the non-sentient universe, a cause must be certain and not merely possible if it is to produce its effect. It makes no sense to say “The traffic lights may turn green therefore the traffic moves off”. Rather, the traffic lights must turn to green. However, it does make sense for a human being to reason that “It is possible there will be an accident therefore I will drive carefully”. In this case the possibility of the accident causes careful driving. We are considering a possible risk and behaving in a manner which maintains our integrity.
So, in living beings there is also an association between entropy, causality, and probability but one which is significantly different from that seen elsewhere in the universe. The effect on human nature of this fundamental anti-entropic drive cannot be overstated as will be discussed in future posts.
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