A short list of the laws of thermodynamics, in simple terms:
Zeroth law: Objects in contact tend to reach the same temperature.
First law: Energy is conserved (if you consider all the forms, including heat).
Second law: You can’t extract heat energy without a temperature difference.
Third law: Nothing can reach the temperature of absolute zero.
The second law can also be understood as the fact that all objects in contact with each other tend toward equilibriun — i.e., they all tend toward the same temperature. A famous consequence of the second law is that whenever heat flows, the total “disorder” in the Universe tends to increase. The third law is plausible, since it is hard to remove heat from an object without having something that is colder, and so it is difficulty to remove heat from any object that is close to absolute zero.
The laws of thermodynamics are fundamental principles governing the behavior of energy and its transformation in natural systems. Developed through the contributions of various scientists and philosophers over time, these laws have played a crucial role in shaping our understanding of physics, chemistry, engineering, and other fields. Here's an overview of each law, their historical development, and philosophical importance:
Zeroth Law of Thermodynamics
The Zeroth Law was named after the First and Second Laws but is more fundamental. It was introduced by Ralph H. Fowler in the early 20th century. This law states that if two systems are in thermal equilibrium with a third system, they are also in thermal equilibrium with each other. It establishes the concept of temperature and provides the basis for temperature measurement. Philosophically, the Zeroth Law demonstrates the transitive property of thermal equilibrium, emphasizing the importance of temperature as a fundamental physical property.
First Law of Thermodynamics (Conservation of Energy)
The First Law, also known as the law of energy conservation, was formulated in the mid-19th century by James Joule, Julius von Mayer, and Hermann von Helmholtz. This law states that energy cannot be created or destroyed, only converted from one form to another. In a closed system, the total energy remains constant, and the change in internal energy (∆U) is equal to the heat (Q) added to the system minus the work (W) done by the system: ∆U = Q - W. The First Law affirms the ancient philosophical idea of "nothing comes from nothing," revealing the fundamental nature of energy and its conservation in the universe.
Second Law of Thermodynamics
The Second Law emerged in the 19th century from the works of Sadi Carnot, Rudolf Clausius, and Lord Kelvin, who were investigating heat engines and the efficiency of energy conversion. This law states that natural processes tend to increase the overall entropy (disorder) of a system and its surroundings. In other words, energy tends to disperse and spread out, making some forms of energy less available for doing useful work. Philosophically, the Second Law highlights the arrow of time and the irreversible nature of many processes, providing a deep insight into the progression of the universe and the nature of order and disorder.
Third Law of Thermodynamics:
The Third Law was developed in the early 20th century by Walther Nernst. This law states that as the temperature of a system approaches absolute zero (0 Kelvin), the entropy approaches a minimum value. In a perfect crystalline substance at absolute zero, the entropy is zero, meaning the system has reached its lowest possible energy state. The Third Law emphasizes the unattainability of absolute zero and the limits of our ability to extract energy from a system, reflecting on the fundamental constraints of the physical world.
The laws of thermodynamics are essential in understanding how energy flows and interacts with matter, guiding the design of engines, refrigerators, and other systems that involve energy conversion and transfer. They also provide a framework for understanding natural phenomena, such as climate change and the formation of stars and planets. From a philosophical standpoint, the laws of thermodynamics have profound implications for our understanding of the nature of the universe, the progression of time, and the limits of what is physically possible.
Commentaries and Quotes
Scientists appreciate that the Second Law is far more than an explanation of everyday nuisances. It is a foundation of our understanding of the universe and our place in it.
In 1928 the physicist Arthur Eddington wrote: "The law that entropy always increases . . . holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell’s equations—then so much the worse for Maxwell’s equations. If it is found to be contradicted by observation—well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation."
In his famous 1959 Rede lectures, published as The Two Cultures and the Scientific Revolution, the scientist and novelist C. P. Snow commented on the disdain for science among educated Britons in his day: "A good many times I have been present at gatherings of people who, by the standards of the traditional culture, are thought highly educated and who have with considerable gusto been expressing their incredulity at the illiteracy of scientists. Once or twice I have been provoked and have asked the company how many of them could describe the Second Law of Thermodynamics. The response was cold: it was also negative. Yet I was asking something which is about the scientific equivalent of: Have you read a work of Shakespeare’s?"
Steven Pinker: "One reason the cosmos is filled with so much interesting stuff is a set of processes called self-organization, which allow circumscribed zones of order to emerge. When energy is poured into a system, and the system dissipates that energy in its slide toward entropy, it can become poised in an orderly, indeed beautiful, configuration—a sphere, spiral, starburst, whirlpool, ripple, crystal, or fractal. The fact that we find these configurations beautiful, incidentally, suggests that beauty may not just be in the eye of the beholder. The brain’s aesthetic response may be a receptiveness to the counter-entropic patterns that can spring forth from nature. But there is another kind of orderliness in nature that also must be explained: not the elegant symmetries and rhythms in the physical world, but the functional design in the living world. Living things are made of organs that have heterogeneous parts which are uncannily shaped and arranged to do things that keep the organism alive (that is, continuing to absorb energy to resist entropy). From: Pinker, Steven. Enlightenment Now (pp. 17-18). Penguin Publishing Group. Kindle Edition.
Entropy
Entropy is a measure of the disorder in molecules. Warm objects, by their shaking, have more disorder, and therefore higher entropy. Whenever heat flows, the entropy of the Universe increases, although the entropy of an object (such as your brain) can decrease. Indeed it does, when you learn something. Entropy is based on the four laws of thermodynamics: (0) objects in contact tend to reach the same temperature, (1) energy is conserved, (2) extracting useful energy from heat requires a temperature difference, and (3) the entropy of the Universe is always increasing.
Energy can be used to extract heat from an object. That is the basic principle of the refrigerators, the air conditioner, and the heat pump.
Entropy is a fundamental concept in physics and thermodynamics, which quantifies the degree of disorder or randomness in a system. In classical thermodynamics, it is related to the dispersal of energy, while in statistical mechanics, it is associated with the number of microstates (configurations) that correspond to a given macrostate (observable properties). The concept of entropy has far-reaching implications not only in science but also in philosophy, as it touches upon the nature of order, disorder, and the arrow of time.
Historical development of entropy
Early 19th century: French engineer Sadi Carnot laid the groundwork for understanding heat engines' efficiency, which would later influence the development of the Second Law of Thermodynamics.
1850: German physicist Rudolf Clausius introduced the concept of entropy in the context of heat and energy transfer in thermodynamic systems. He formulated the Second Law of Thermodynamics, stating that the entropy of an isolated system never decreases, and it increases for irreversible processes.
Late 19th century: Austrian physicist Ludwig Boltzmann developed the statistical mechanics approach to entropy, relating it to the number of microstates corresponding to a macrostate. His famous equation, S = k * log(W), connects entropy (S) with the Boltzmann constant (k) and the number of microstates (W).
20th century onwards: Entropy has been applied to various fields, including information theory, where Claude Shannon introduced a concept analogous to entropy in 1948, known as Shannon entropy, which measures the information content or uncertainty in a message or data set.
Importance in physics
Entropy is essential in understanding various physical phenomena, including:
Energy transfer: Entropy helps explain why heat flows from hot to cold regions, as it represents the natural tendency for energy to disperse and spread out.
Phase transitions: Entropy plays a critical role in phase transitions, such as melting and vaporization, as changes in entropy can be used to predict the behavior of matter under different conditions.
Thermodynamic cycles: Entropy is vital in designing and analyzing engines, refrigerators, and heat pumps, as it helps assess the efficiency and performance of these systems.
Importance in philosophy:
Entropy has profound implications for philosophical discussions, including:
Arrow of time: Entropy introduces an inherent directionality in time, as the overall entropy of an isolated system increases over time, highlighting the irreversible nature of many processes and providing a framework to understand the progression of the universe.
Order and disorder: Entropy serves as a quantitative measure of order and disorder in physical systems, offering insights into the emergence of structure and complexity in the universe.
Limits of knowledge: Entropy, particularly in the context of information theory, highlights the fundamental limits of knowledge and our ability to predict or control complex systems, as it sets constraints on the amount of information that can be extracted or compressed.
Entropy is a crucial concept in both physics and philosophy, as it provides a quantitative framework to understand energy dispersal, the progression of time, and the nature of order and disorder. With its historical development spanning from the early 19th century to modern times, entropy continues to be a vital concept that shapes our understanding of the physical world and the limits of our knowledge.