case, the proposed demarcation is helpful either to design material realizations of a theoretical construction or to compare a physical experiment with the concept it aims to realize.
Another interesting point is about its PF and respective conditions of production. How is it possible to produce a function that does not respect a fundamental law of physics? A harsh answer would be that this system cannot exist, and thus, there is no need to discuss such a metaphysical construction in physics. We argue that the key issue here is the name given to the operating component: demon or a supernatural being. Its attribute is to open and close the door based on the knowledge of microstates of the system (velocity and location of molecules), and it has a specific goal of separating fast molecules to one side and slow to another – the hot and cold side, respectively. This split of the flow component based on its microstates into two different macrostates (hot and cold) leads to a decrease in the system entropy, which is the aim of the system. In today's terminology, Maxwell's demon could be renamed an ideal smart controller.
Clearly, with the knowledge and technology available in the nineteenth century, as well as the general context back then, defining the problem as a thought experiment in reference to a demon is understandable. The proposed change of name is an index that the demon is a computing device that is internal to the closed system. Since computing has its own fundamental laws related dissipation of energy as demonstrated by Landauer in [13], this result indicates that the Maxwell's demon experiment cannot form an isolated system because of the fundamental limits of computation. Therefore, the second law remains valid, and the Maxwell's demon experiment cannot exist as a system whose function is to decrease the entropy of an isolated system.
Given this, we can rectify our demarcation of Maxwell's demon as follows.
1 PS (a) Structural components: a completely isolated box with a door that can open and close in an ideal way, (b) operating components: an ideal smart controller which controls the door; and (c) flow components: a gas with equal temperature composed of molecules moving at different speeds.
2 PF Decrease the entropy of the system through necessary computing processes assuming no exchange of energy between it and its outside except by the unavoidable dissipation related to computing processes.
3 C1 It is physically possible to decrease the entropy of an isolated system without violating the second law of thermodynamics by utilizing necessary computing processes.
4 C2 The demon needs to know the velocity of the particles, their positions, and the sides that are associated with “cold” and “hot” states in order to control the door without using energy aiming at a decrease in the system entropy. These are the computing processes.
5 C3 The system has no relation to the environment (no flow of energy, matter, or information) except by the fundamental heat generation related to the necessary computing processes.
In this way, the conceptual system is posed in scientific terms that allow for experimentation by its material realization. As the result presented in [12] demonstrates, this thought experiment can be materially realized. However, we are not yet done with the Maxwell's demon experiment because of its relations to uncertainty, information, and decision‐making: all topics related to the following chapters! The demon will stay with us for a while more.
2.6 Summary
In this chapter, we went through different meanings of the word “system.” Among its different usages, we employed the definition and conceptualization from Systems Engineering as our theoretical raw material to then produce a scientific concept. From the general formalization of a system based on its components with their own specific attributes combined to perform a specific function or specific functions, we defined and solved the demarcation problem. The demarcation problem refers to how a particular system – determined by its peculiar function – is articulated with everything else by means of its conditions of existence. The demarcation is a theoretical process, exclusively symbolic, that produces objective knowledge of particular engineered objects that are conceptualized as functioning systems, which already exist or might exist. We also indicated different forms into which systems can be classified with respect to their own characteristics. Different examples were presented to illustrate the most important topics. At the end of this chapter, we dedicated a section to analyze as a system one classical thought experiment that will reappear in the following chapters: Maxwell's demon.
Exercises
1 2.1 Residential heating system. There are different ways to heat a house during cold periods as indicated by the USA Energy Department [14]. The idea here is to apply the concepts learned in this chapter to analyze residential heating.Consider an electric heating system connected to the main grid (as any other appliance of your house). Demarcate this system following Example 2.3.Classify the system demarcated in (a) following the examples presented in Section 2.4.During the winter months, the electricity demand in households with electric heating grows as the temperature decreases. Think about a heating system that could function without electricity from the grid. Demarcate this potential heating system and compare it with (a).
2 2.2 Boolean algebra and logic circuits. George Boole, an English mathematician and philosopher from the nineteenth century, proposed in his first book in 1847 a mathematical approach to logic by using mathematical symbols to represent classes of objects and then to manipulate them by mathematics [15]. In another groundbreaking work dating to 1938, Claude Shannon proposed in his Master's thesis a way to materially realize Boolean algebra by circuits [16]. They are represented by truth tables and logical circuits as illustrated in Figure 2.2.Analyze as a system (similar to Exercise 1) the logic gates AND, OR, and NOT, which are the basis of all logic circuits.Figure 2.2 Truth tables and logic gates of AND, OR and NOT operations.Propose a way to materially realize these three logic gates based on (a).Follow the same steps used in (a) to analyze the proposal in (b), identifying the main differences between the conceptual system and its potential material realization.Read Shannon's Master's thesis [16] and discuss the importance of such a discovery.PS The reader is suggested to play with online Boolean algebra calculators (e.g. [17]) as an extra task; a starting point could be the calculation of the truth tables presented in Figure 2.2.
References
1 1 Merriam‐Webster Dictionary. System; 2020. Last accessed 22 October 2020. https://www.merriam-webster.com/dictionary/system.
2 2 Blanchard BS, Fabrycky WJ. Systems Engineering and Analysis: Pearson New International Edition. Pearson Higher Ed; 2013.
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5 5 Beltrami E. Mathematics for Dynamic Modeling. Academic Press; 2014.
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7 7 Wolfram S. A class of models with the potential to represent fundamental physics. Complex Systems. 2020;29(2):107–147.
8 8 Drake GWF. Thermodynamics.
