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Thermodynamics and the Arrow of Time


Heat transfer is a common process in most machines, especially where two surfaces are in contact. The process is conceptualized as energy in transit. The transfer of heat is used to perform work, for example when the parts of the machine are in motion. Heat can also be generated when energy is transformed from one form to another. For example, a car engine burns fuel and heat is transferred when the fuel turns into a gas. However, most of the heat produced in the process does not perform work on the gas. On the contrary, some energy is released into the environment in the process. What this means is that the engine is not 100% efficient (OpenStax College [OpenStax] 5). The academic field dealing with the study of this phenomenon (heat transfer) is referred to as thermodynamics. Apart from addressing the issue of heat transfer, the academic field also analyzes the relationship between the phenomenon and work.

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The current paper is written against this backdrop. In the paper, the author gives a brief overview of the second law of thermodynamics, which is expressed in various ways. In addition to the overview, the author defines the concept of entropy and how it is related to heat transfer. The different expressions of heat transfer are, however, equivalent to each other. The author explains the relationship between entropy and the arrow of time. Finally, the author outlines ways of overcoming the various problems associated with the arrow of time. The paper will revolve around a main idea. The main idea is a description of how the arrow of time, also referred to as aging, can be anticipated in design.

Thermodynamics and the Arrow of Time

The Second Law of Thermodynamics

It is possible to express the second law of thermodynamics in many specific ways. According to Thomas Kuhn, the second law was first conceptualized by two scientists in this field. The two were Rudolph Clausius and William Thomson. As already indicated in this paper, most expressions of this law have been proved to be more or less equivalent to one another. Basically, the second law of thermodynamics addresses the issue of systems and physical processes taking place within them. It states that in a closed system, one “cannot finish any real physical process with as much useful energy as they had to start with” (Harvey and Uffink 528). What this means is that heat engines that are based on the principles of thermodynamics cannot be 100% efficient (Harvey and Uffink 528). Some energy will be lost to the environment as it is converted from one form to the other.

Furthermore, the second law of thermodynamics deals with the direction taken by spontaneous processes. In most cases, physical processes occur spontaneously and in one direction. The implication here is that the processes are irreversible under a given set of conditions. There are certain processes that never occur, suggesting that there is a law forbidding them to take place. The law forbidding such processes to take place is the second law of thermodynamics (OpenStax 5).

It is important to note that complete irreversibility is a statistical statement that is hard to realize. Therefore, an irreversible process is conceptualized as one that depends on path. Such conceptualization means that if a process can go in one direction only, then the reverse path differs fundamentally and the process cannot be reversed (Hawking 345). As a designer, I have to be alive to this reality. For example, I must be aware of the fact that heat involves the transfer of energy from high to low temperatures. A cold object that is in contact with a hot object will not get colder. On the contrary, heat transfer from the hot object will make raise its temperature. Another important to note as far as the second law of thermodynamics is concerned is the relationship between mechanical energy and thermal energy. According to Maccone (3), mechanical energy can be converted to thermal energy. For example, when two surfaces moving in the opposite direction come into contact (mechanical energy), the friction between them will generate heat (thermal energy). As a designer, I am also aware of this relationship.

Entropy, the Second Law of Thermodynamics, and the Arrow of Time in Design

Entropy is sometimes referred to as the arrow of time. The concept is defined as the quantitative measure of disorder in a given system, whether closed or open. Entropy is conceptualized with references to energy, which is the ability to do work. It is a fact beyond doubt that all forms of energy can be converted from one form to another. In addition, all forms of energy can be used to do work. However, it is not always possible to convert the entire quantity of energy available to work. The unavailable energy is of interest to thermodynamics and to designers like me. The significance of the lost energy is accentuated by the fact that thermodynamics arose from efforts to convert heat to work. Entropy is a thermodynamic property that is used to measure the system’s thermal energy per unit temperature that is not available to perform useful work. As a concept, entropy calls for a particular direction for time (Harvey and Uffink 530).

In an isothermal process, the change in entropy (∆S) is computed in terms of heat and temperature. It is the change in heat (∆Q) divided by the absolute temperature (T). In any reversible thermodynamic process, the change in entropy is represented in calculus as the integral of the progress from initial state to final state (OpenStax 4).

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Entropy increases when heat is transferred from hot to cold regions since the change at low temperatures is larger than the one at high temperatures. Therefore, the decrease in entropy associated with a hot object is less than the increase in entropy of a cold object. However, for a reversible change process, entropy remains constant. To this end, the second law of thermodynamics can be stated in terms of entropy. It is stated as “…..the total entropy (of) a system (that) either increases or remains constant in any process” (Hawking 365).

The level of entropy increases with time. What this means is that things become more disorderly as time goes by. Thus, if one happens to find a stack of papers on their desk in a mess, they should not be surprised even if they had left them neatly stacked. They should realize that it is entropy at work. The scenario described above illustrates the nature of the relationship between entropy and the arrow of time (OpenStax 5).

Anticipating the Arrow of Time as Part of Design

The various laws of physics, including the thermodynamic laws, are described by Lieb and Yngvason (6) as “time invariant”. What this means is that the laws still hold even if time is reversed. But, according to OpenStax (4), time reversal contradicts nature and logic. The reason for this is that time progresses forward as opposed to backward. The contrast between time reversal and reality has created a reversibility paradox, which scientists are trying to understand (OpenStax 6).

In anticipating the arrow of time, scientists have proposed numerous solutions to address the reversibility paradox. One solution suggested by the scientists involves embedding irreversibility on physical laws. Another possible solution is establishing low-entropy initial states. One of the various solutions in this area was suggested by Maccone. The scholar assumes that quantum mechanics remain constant regardless of the nature of the scale used (Hawking 350). The scholar proves that entropy can either increase or decrease. In cases where an occurrence leaves at its wake a trail of information, nature dictates that the phenomenon should increase. However, entropy decreases for some phenomena. But such phenomena do not leave any information behind to show that they have happened. The solution allows for time reversibility to exist, but not to be observed. The condition is in line with the laws of physics and the second law of thermodynamics (Maccone 5).

Hawking (350) is of the view that it is possible to reduce the direction of time to achieve an entropy gradient. The scholar bases this on the assertion that our brains act like computers, which supposedly incur an entropic cost, using memory in the process. It follows that the states of the world we remember are those with lower entropy than present and future states. The reason for this is that all subsystems of the universe partake in the same entropic flow. Hawking (355) concludes that the psychological arrow of time coincides with the thermodynamic arrow of increase in entropy.

Earman (45) formulated a condition that needs to be met if a theory is to be ‘time reversal invariant’. However, subjecting thermodynamics to conditions and criteria is not completely straightforward. The only clear instance where reference to time is explicitly made is in the distinction between the ‘initial’ and the ‘final’. The distinction is evidenced in the adiabatic accessibility relation (Earman 45).

Lieb and Yngvason (6) approach the problem of arrow of time by taking into consideration the recent axiomatization of thermodynamics. The two scholars make efforts to establish the existence of a simple entropy function. The function so established is proved to increase under adiabatic processes. The approach adopted by the two scholars does not presuppose the differentiability of T, which means that it is capable of handling phase transitions. Furthermore, the approach guarantees that entropy is defined globally on T terms (Lieb and Yngvason 5).

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In this paper, the author briefly explained the second law of thermodynamics and ways in which it the law is expressed. For the purpose of this paper, the author expressed the second law of thermodynamics in terms of entropy. The author explained the relationship between entropy and the arrow of time. Finally, the author outlined possible ways of overcoming the problem of the arrow of time. Throughout the paper, the author was describing how the arrow of time, also defined as aging, can be anticipated in design. The description was the underlying theme of the paper. The definition of the second law of thermodynamics, the expression of the law in terms of entropy, as well as the description of solutions to address entropy, were all constructed around the underlying theme.


Harvey, Brown and Jos Uffink. “The Origins of Time-Asymmetry in Thermodynamics: The Minus First Law.” Philosophy of Science 32.4 (2001): 525-538. Print.

Earman, Joseph. “An Attempt to Add a Little Direction to ‘The Problem of the Direction of Time’.” Philosophy of Science 41.1 (2004): 15–47. Print.

Hawking, Stephen. The No Boundary Condition and the Arrow of Time, New York: Free Press, 2004. Print.

Lieb, Eric and Jose Yngvason. “A Fresh Look at Entropy and the Second Law of Thermodynamics.” Physics Today 3.2 (2000): 3-7.

Maccone, Lorenzo. “Quantum Solution to the Arrow-of-Time Dilemma.” Physical Review Letters 103.8 (2009): 2-5.

OpenStax College. 2012. College Physics. Web.

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