Open Letter 3-3

The Scientific Revolution by Galileo

Galileo Galilei appears on Italian soil. He conducted an experiment in which he rolled a sphere of the same size but different weights down a slope and found that the speed at which the sphere rolled was the same regardless of the difference in the weight of the objects. This discovery cracked Aristotle’s authority, since it had been widely believed that the heavier the object, the faster it fell, according to Aristotle’s laws of motion.

The goal of modern science was to formulate natural phenomena into mathematical formulas, and there was no room for the significance of existence and purpose of things, which are important elements that constitute Energeia. Rather, by thoroughly eliminating such elements, modern science attempted to clarify the providence of nature. Thus, Aristotle’s Energeia disappeared from the world of science, and a new journey began in search of who energy is.

From Newton (mechanics) to Joule and Lord Kelvin (thermodynamics)

In the beginning, modern science only observed mechanical kinetic energy, as exemplified by Galileo’s experiments. The greatest achievements of this approach are the three laws of motion established by Isaac Newton and the “Law of Universal Gravitation,” the pinnacle of classical mechanics. The left-hand side of all these physical equations is “F”. “F” for force. In other words, in the 17th century, when Newton was active, the term energy had not yet been established as a term in physics. It was not until the 19th century that the term energy was first used. It was used by the English physicist Thomas Young, famous for his experiments on the interference of light. It was recorded in his Lectures to the Royal Society, published in 1807. However, his usage was still limited to the explanation of mechanical phenomena.

It was not until the mid-19th century that the term energy came to be used as a description of something beyond mechanical phenomena. This was the era of James Prescott Joule, famous for Joule’s law, and Lord Kelvin, who left his name on the absolute temperature K (Kelvin temperature), which is based on the temperature at which atoms and molecules stop moving (-273°C). It was during this period that the debate over energy finally expanded from the mechanical world to include heat. The first law of thermodynamics, the so-called “law of conservation of energy,” established during this period finally brought the term energy to the forefront of history in the modern sense.

Joule repeatedly conducted experiments in which he passed an electric current through a conductor immersed in water and measured the change in water temperature. He discovered that the amount of heat Q per unit time generated by the current is proportional to the square of the current I and the electrical resistance R of the conductor. This is what is known as Joule’s law. Once the relationship between current and heat quantity was proven, Joule’s attention then turned to where heat comes from. At the time, the understanding of heat was not settled, and there were two theories: the “caloric theory,” which held that it was a massless fluid, and the “kinetic theory of thermal,” which held that it was motion. Historically, the “caloric theory” was the dominant theory, but Joule thought that the “kinetic theory of thermal” was more correct. To verify this, Joule conducted an experiment in which he turned an impeller in water with the weight of a weight and precisely measured the temperature rise of the water due to the impeller’s motion.

Thus, Joule concluded that heat is not matter but motion and asserted the equivalence of heat and motion. Joule’s theory was based on the idea that heat and kinetic energy are forms of energy and can be converted into each other. In this way, the framework of the “law of conservation of energy” was formed, and the groundwork was laid for the use of the term “energy” beyond its mechanical usage. The new academic field thus established, in which heat is a form of energy, was named “thermodynamics” by William Thomson, later Lord Kelvin, a British physicist who was the first to recognize the value of Joule’s experimental results.

From Maxwell (electromagnetic force) to Einstein (nuclear power)

In the same period, the work of Michael Faraday led to the discovery of the law of electromagnetic induction, which confirmed that kinetic energy can be converted into electrical energy. Thus it became clear that electricity is also a form of energy. Maxwell, who was good at mathematics, gave mathematical support to Faraday’s theory by formulating the basic theory of electromagnetic waves based on Faraday’s experiments into mathematical equations. He showed that the circulation of magnetic fields generating electric fields and electric fields generating magnetic fields causes space itself to vibrate, resulting in electromagnetic waves and the transmission of energy.

Furthermore, the speed of electromagnetic waves obtained from his calculations was almost identical to the speed of light, leading him to predict that light is a type of electromagnetic wave. This was later verified in an experiment by German physicist Heinrich Hertz, whose name would remain on the unit of frequency, confirming that light is also a form of energy.

At the beginning of the 20th century, when Einstein was active, the greatest challenge in physics was how to reconcile Newtonian mechanics, which described the behavior of objects, with Maxwell’s equations, which described the behavior of electromagnetic waves. According to Maxwell’s equations, the speed of all electromagnetic waves, including light, is constant at 300,000 km/s in a vacuum. However, based on Newtonian mechanics, there is no limit to the speed of an object. It was Einstein’s mind that provided the solution to this contradiction.

Einstein concludes that time and space can change in order to keep the speed of light constant. Thus was published the Special Theory of Relativity in 1905. In fact, this theory had a very important byproduct. He discovered that (\(E = mc^{2}\)) (E : energy, m : mass, c : light speed). He conducted a thought experiment in which he incident light on a stationary object from the left and right and observed it from a stationary state and from a moving state, respectively. He realized that when an object absorbs energy, its mass must increase. This great discovery surprisingly revealed that even mass is a form of energy.

Mass is the degree to which an object is difficult to move. In everyday life, mass is a concept often spoken of as “weight” (strictly speaking, the two are different). Although it may seem counterintuitive, weight and energy are the same. But the scientific fact is that energy can take the form of static mass as well as dynamic forms such as motion and heat. At this point, the debate over energy has completely transcended the framework of conventional mechanics.

Energy Characteristics

The world of science has revealed that everything in this world is made of energy. Objects, light, heat, and everything else is a form of energy. Energy is all around us. In fact, it is thought that the solar energy that falls to the earth alone is equivalent to more than 10,000 times the total amount of energy used by mankind. When you think about it, it seems unlikely that we will ever have a problem securing energy. With our smart minds, it is only a matter of time before the problem is solved. However, excessive optimism about such technological innovations will only lead people to stop thinking. In order to tackle the energy problem squarely and seriously, we need to understand the physics of energy and its limitations. This is what the study of thermodynamics has taught us.

First law of thermodynamics (Energy neither decreases nor increases)

The first law of thermodynamics is also known as the conservation law of energy. The fact that energy can be exchanged with each other indicates that energy does not disappear, but neither does it increase. The first law of thermodynamics reveals that nothing can be created out of nothing. All that mankind can do through technological innovation is to extract energy from that which holds it in a form that is usable by mankind. Thus, it was theoretically proven that a perpetual engine that creates energy from nothing is not feasible.

However, a question arises here. In a world where the law of conservation of energy works, new energy cannot be created from nothing. However, once energy is used, the energy itself should be stored somewhere or in some other form and never disappear. Thus, the question is whether it is possible to reuse it. This seemed like a possible realization of a perpetual engine.

Second law of thermodynamics (energy dissipates spontaneously)

The second law of thermodynamics is a law that describes a phenomenon that everyone knows empirically. It is the phenomenon that hot water eventually cools down, but cold water does not naturally get hotter. It should be obvious. It was Clausius who first realized the importance of this obvious fact. He focused on the fact that thermal energy has an irreversible direction, going in only one direction.

We live in a world where friction and resistance exist. There the conversion to thermal energy cannot be stopped. This means that in the world we live in, the energy at our disposal is destined to dissipate naturally. The second law of thermodynamics represents that universal fact. With the establishment of the second law of thermodynamics, mankind has come to understand, as a scientific knowledge, that the energy sources available to us are finite. Everything eventually dissipates as heat. The energy input is eventually transformed into low-quality energy, which is then widely dissipated. We are doomed to never be free from the second law of thermodynamics.

This understanding of the second law of thermodynamics is very important when considering energy issues. What the second law of thermodynamics teaches us does not stop there. The second law of thermodynamics extends to every corner of our lives.

Emergence of Entropy

The second law of thermodynamics, which was created to explain the peculiarities of thermodynamics, would eventually give birth to a new term. That is entropy. When you hear the word entropy, you may be under the impression that it is a scientific concept that is even more obscure than energy. In reality, however, entropy is much more familiar to us than energy.

Entropy is a concept conceived by Clausius in 1865 to describe the energy loss that occurs in the conversion of thermal energy to kinetic energy. With the quantification of the irreversibility of thermal energy, the second law of thermodynamics, which deals with the question of the quality of energy, was completed.

The new physical quantity was named entropy, inspired by the Greek word (trope) for “conversion”, since it is concerned with the conversion of kinetic energy to thermal energy.

It is no use crying over spilt milk. (What entropy represents)

Entropy was born in the mind of Clausius as a means of expressing the irreversibility of thermal energy. Although the invention of entropy was helpful in explaining irreversibility, it still could not explain why thermal energy had the direction of irreversibility in the first place. What entropy, a physical quantity, meant remained a mystery.

It was the Austrian physicist Ludwig Boltzmann, born in 1844, who elucidated what entropy truly means. Boltzmann, who studied the relationship between the motion of gas molecules and thermal energy, believed that thermal energy is the aggregate of random motions by tiny particles, atoms and molecules. He interpreted this as the higher the temperature, the more intense the motion of atoms and molecules, and the more heat they generate.

Eventually, he saw the need to integrate the relationship between the microscopic phenomenon, the motion of gas molecules, and the macroscopic phenomenon, thermal energy, and adopted a probability and statistical perspective. In 1877, he wrote a paper in which he argued that entropy is a measure of the “messiness” caused by the random motion of atoms and molecules. This paper was groundbreaking in that it showed that if all atoms and molecules were in random motion, the overall state could be predicted with a high statistical probability, even though the individual motions were too detailed and complex to analyze.

His theory, built on his knowledge of probability and statistics, a new discipline, was a paper written on the premise of the existence of atoms and molecules, which at the time had not yet been confirmed to exist. The paper was so novel that it was thoroughly criticized, and Boltzmann gradually became mentally ill and finally committed suicide. Not long after his death, however, the existence of atoms and molecules was proven, and the correctness of his theories, which made full use of probability and statistics, was also proven. The discipline he pioneered was later called “statistical mechanics.”

The greatest realization that can be gained from studying entropy is the finite nature of resources. Why is energy considered finite when it is supposed to be conserved by the first law of thermodynamics? It is because energy is a matter of quality, and what we really need is a low-entropy resource among energy resources. Hence, the resource is finite.

Time was created by mankind

Among the many laws discovered by the development of modern science, none is more suggestive than the second law of thermodynamics, the law of increasing entropy. This cannot be emphasized enough. The core case that touches on this is the relationship between “time” and entropy, which has taken root in our daily lives. Time, as we think of it, is a unidirectional, irreversible process that proceeds from the past to the present and into the future. The British astronomer Arthur Eddington, active in the first half of the 20th century, called this the “arrow of time.”

We are able to sense the flow of time because of the existence of the second law of thermodynamics, which states that the world flows in one direction as things dissipate. However, such an irreversible flow can be recognized with certainty only in the macroscopic world, and its existence in the microscopic world at the atomic level is immediately questionable. Let us consider this by delving into the reality of thermal energy.

What determines the dissipation and degradation of energy is the presence of thermal energy. Thermal energy is the aggregate of kinetic energy produced by the random movement of large groups of atoms and molecules. So what would happen if this motion were to consist of only one atom? Regardless of which direction it moves, an atom can only go in one direction. The motion of only one atom is kinetic energy, not thermal energy. In other words, there is no thermal energy in the microscopic world of a single atom or molecule.

In fact, the physical formulas of Newtonian mechanics and relativity, which describe kinetic energy, do not bind that time moves only in one direction. This is because the formulas are valid even when time is reversed. In other words, in the microscopic world, we don’t really know if there is an “arrow of time” that travels past, present, and into the future. The reality is that even with the most advanced knowledge of modern physics, we still have not been able to derive an answer to the question of time. Surprisingly, the “time” that we are familiar with is in fact only something that appears for the first time in the macroscopic world.

To go a little further into this issue, and to put a bold spin on it, it can be said that the flow of time is something uniquely created by us living in the macroscopic world, especially by humankind. We, as living organisms, receive stimuli from the outside, make decisions and react to them within the range of freedom we are allowed. The existence of a sequence of events from receiving a stimulus to reacting to it is the reason why we are able to sense the existence of time.

It can be said that because humans were able to record the flow of time and create “time” using the exceptional brain power that evolved with the acquisition of fire, we are now able to believe in our own existence. Descartes’ statement, “I think, therefore I am,” may be a true statement of this.

Furthermore, by recognizing the flow of time – past, present, and future – people have come to know that they can create their own future at will. By creating time, mankind also gained the power to create the future. In this way, we can see that “time” is an existence that is familiar to us, but at the same time, it is something truly profound. It is also supported by the second law of thermodynamics, or the law of increasing entropy.

Global Environment and Thermal Energy

Indeed, as a result of humanity’s massive use of energy, the amount of anthropogenic waste heat energy exhaled into the atmosphere is increasing at an accelerating rate. In fact, the effects of this phenomenon are becoming more apparent in urban areas where populations are concentrated, and the effects of man-made structures are also contributing to the high temperature phenomenon commonly known as the “heat island effect.

However, global warming is a different story. The sun beams down on the earth more than 10,000 times more energy than is used by humans. Therefore, the impact of waste heat energy itself released by human activities on the global environment as a whole is considered to be extremely small.

By far the largest impact on climate change and global warming is the greenhouse effect associated with the increase in the greenhouse gases carbon dioxide and methane. This is because the presence of greenhouse gases clogs the great flow of energy that the earth receives from the sun and eventually releases into space.

There are three ways heat can be transported. They are conduction, radiation, and convection. The greenhouse effect is tied to thermal radiation. Thermal radiation is the transfer of heat when an electromagnetic wave emitted from one object is absorbed by another object. Since heat is transferred by electromagnetic waves, heat can be transmitted even in a vacuum, and we living organisms on the earth are the greatest beneficiaries of this phenomenon. What would happen if the Earth did not have a greenhouse atmosphere?

The heat that warms the ground and oceans during the day will quickly leave the extreme cold of space at night due to thermal radiation from the Earth’s surface. This is the reason why the temperature difference between day and night on the Moon, where there is almost no atmosphere, is well over 200°C.

However, the Earth has an atmosphere that contains enough water vapor, carbon dioxide, methane, and other gases that are greenhouse gases. Since the atmosphere retains a certain amount of heat, the earth’s environment is stable at a temperature range that is conducive to the survival of living organisms.

Thus, greenhouse gases are indispensable for our living organisms, but the amount of solar energy that falls on us is so enormous that even a slight imbalance can clog the flow of energy released from the earth into space and accelerate global warming. That is why there is concern that carbon dioxide, one of the greenhouse gases, is increasing due to anthropogenic activities.す。

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