Immigration: The Physics

Next week I will leave for my summer break. This time we are taking a complicated tour, starting in England a week after the Brexit referendum. Next we will spend a few days in Israel before continuing to Poland, Malta, and France; then back to England and home. I am familiar with this terrain; the only place new to me will be Malta, where I will spend about a week. I’ll spend most of the time with friends and family in each country. Even in Malta, I will double my tourism with seeing my Australian family members who wanted to escape their country’s winter.

Aside from visiting family and friends, I will be paying attention to how the influx of refugees is impacting the various countries. The refugee crisis has drastically affected the “safe havens” where they flock. BREXIT is driven in large part by the fear of the refugee incursion. When I discussed the emergence of Donald Trump as a leading (now presumptive) Republican Presidential candidate (March 8, 2016), I wrote:

United States residents are not the only ones alarmed. The European press is fully covering the turmoil with great apprehension. As many US publications have noticed, however, the Europeans shouldn’t be surprised. Donald Trump actually fits in very well within recent political trends in Europe.

Political figures like Italy’s Silvio Berlusconi have many similarities to Donald Trump. Not only was he a candidate for high political office but he actually served as Prime Minister four times. Meanwhile, Victor Orban, the President of Hungary, is very busy building fences to block the refugees that are seeking security in Europe. Jean-Marie Le Pen and his much more media-savvy daughter Marine Le Pen also fit into this category. The memorable French presidential election of 2002 saw the National Front candidate win the first round against the serving socialist Prime Minister Lionel Jospin only to then be defeated by the Conservative Jacques Chirac 82% – 18% because almost everybody in France was truly alarmed by Le Pen’s policies. In fact, just a few days ago, neo-Nazis were elected to the Slovakian parliament for the first time.

Much of this shift, including the shift in the United Stated is emerging because of fear of being swamped by refugees.

Today I’m starting a new series about human migration/emigration/immigration and its global impact on almost every aspect of our lives, including climate change.

To begin with, immigration plays a big part in the evolving physics of the human-dominated Anthropocene (see the previous series of blogs). This is directly linked to the notions of entropy and the Second Law of Thermodynamics. These are not simple concepts and they might sound like gibberish to the uninitiated. Given how integral these ideas are to the themes of this blog, I figured that over the last four years I must have covered them in depth. Apparently I was wrong. Although putting “Second Law of Thermodynamics” in the search box came up with a few related blogs, the term “entropy” provided a single entry, which quotes somebody using the phrase in relation to income inequality. It is time now to rectify this omission.

I devoted two pages in my book, Climate Change: The Fork at the End of Now to the topic:


The law of conservation of energy is a fundamental, universal law (meaning that we believe it to apply throughout the universe) that puts limits on our ability to create “something from nothing” at least as far as energy is concerned. It tells us that we cannot drive a car or operate an electrical power station without feeding it with some sort of fuel. We cannot create a perpetual motion machine that will move constantly without supplying it with energy. This sort of limitation offends some of us, but for most of us it is not very surprising. It is one of the pillars of the work ethic that we were exposed to since early childhood and try to pass on to our children and grandchildren.

What about the following scenario? Imagine that we are cruising on a vast ocean. The ocean contains a very large number (around 1045) of molecules of water. Each molecule moves randomly in all directions and interacts with other water molecules. All this energy is the internal energy of the ocean. Can we create an engine that will use a very small fraction of this energy to propel the ship? We are not violating any conservation law— we are not even depleting any reservoir because the sun will continue to hit the water, and our energy withdrawal will hardly cause any temperature change in the ocean. In practical terms, for us as passengers on that ship, we would be able to cruise the oceans forever without using any fuel (indirectly we are using solar energy)—we would enjoy a perpetual motion machine without violating the energy conservation law. Well, not surprisingly, we cannot do that. If it is too good to be true it probably is, but why?

The reason is that there is another fundamental law, as basic as the energy conservation law (some even think more basic) that states that left on its own, a system tends to evolve in such a way as to increase disorder. To paraphrase it: left on its own, the universe tends to evolve to a state of maximum mess (just like my grandchildren do to a room full of toys). You will notice that the statements start with “left  on its own,” which means that my grandchildren can still fix up their room—but they will have to put energy into the effort; if they are not willing to exert the energy, the room will get messier and messier. This law is known as the second law of thermodynamics; thermodynamics is the scientific discipline that deals in processes involving the flow of heat. The first law of thermodynamics deals with the application of the law of conservation of energy to thermal processes. This all sounds a bit philosophical—why do we need it here? How can we use it to show that we cannot have our dream cruise? We need it because, as I will show in Chapter 6 when I discuss the solar energy cycle, the only commodity we get from outer space in a constant supply is “order” for us to dissipate. This “order” is carried by the solar radiation. In a sense, the greenhouse effect is a perturbation on this “order in” and “disorder out” balance that we engage in with the sun. We should get serious about the concept and try to quantify it in a way that will allow us to do some calculations and predict or explain some important observations in a quantitative way.

The physical property associated with this trend to “disorder” is called entropy. We connect it to thermal processes through a very simple equation:

Change in entropy = Q/T

Q in this equation is the amount of heat coming in to heat the system (when Q is positive) or going out to cool the system (when Q is negative). T is the absolute temperature (in the Kelvin scale). The rationale behind this definition is that the absolute temperature, T, is associated with the average energy per molecule. So the ratio Q/T represents the average number of molecules that share the given amount of heat Q. Because all these molecules move in all possible directions, the disorder will increase with the number of possible, equally probable movements. This is analogous to a room with many drawers that have items randomly distributed, as compared to a single drawer stuffed with items. The disorder in the first case is considered to be much higher than in the second case.

Let us restate the second law of thermodynamics in terms of entropy: Left on its own, a system will evolve in a way that will increase its entropy. So what happens with our wonderful cruise? The only thermal process involved is the extraction of heat from the ocean. We are decreasing the heat contents of the ocean (negative Q in equation 5.4) without any compensating increase in entropy because the heat energy is converted to work that represents a very low-entropy (high-order) process, hence the net result of the process is decrease in entropy— which is forbidden by the second law.

Let us apply the principle to another issue: we take a hot object and put it in contact with a cold object—what happens? Our everyday experience tells us that heat will move from the hot object to the cold object and that, as a result, the temperature of the hot object will decrease and that of the cold object will increase until the two objects equal the same temperature. From a perspective of energy conservation, heat can move either way without violating the law. T(H), the temperature of the hot object, is larger than T(C), the temperature of the cold object. So Q/T(H) will be smaller (due to the bigger number in the denominator) than Q/ T(C) . If we extract heat from the hot object (Q negative) and put it in the cold object (Q positive), the entropy of the hot object will decrease, but the entropy of the cold object will increase by larger amount, so the change in entropy is positive and in agreement with the second law.

As a final example, let us construct an abstract power station and try to see if the second law imposes any limit on our ability to generate power. This will be useful later when I discuss possible alternatives to current energy sources. The most common power stations generate electrical power by rotating a coil inside a magnet. Usually the rotation of the coil is performed by a steam turbine; hot steam at around 400°C enters the turbine to rotate the coil that generates the electricity. We get the steam by heating water with whatever energy source we choose— nuclear, coal, natural gas, and so forth. Whatever energy source we use, the energy of the hot steam is converted into the mechanical energy in the rotation of the coil that results in the production of electrical power. The internal combustion engine, which is mostly responsible for the propulsion of our cars, works on a similar principle: we inject a mixture of gasoline and air into a cylinder, the mixture gets compressed, and a spark ignites the mixture to a temperature higher than 1000°C. The fuel gets “burned,” meaning that the hydrocarbons get oxidized by oxygen to produce carbon dioxide and water. The oxidation releases energy that heats the gas. The hot gas expands to push a piston that rotates the crankshaft that, in turn, rotates the wheels. We are converting the chemical energy in the fuel (by burning it) into heat energy and converting this heat into the mechanical energy of the car. In both cases an exhaust of cooler steam or exhaust gases exits the engine. The second law imposes an absolute limit on to the efficiency of converting the heat energy. The limit depends on the operating temperature of the engine (approximately 400°C for the electric generator and 1000°C for the car engine). This limiting efficiency is called the Carnot efficiency after the French physicist Sadi Carnot (1796– 1832). It states that

Maximum efficiency (as a percentage) = (1 – T(C)/T(H) ) × 100.

The temperatures here are in Kelvin— for the electric generator the hot source (hot steam) reaches the temperature of 400°C = 400 + 273 = 673 K. The cold sink is the exhaust gas that at ambient temperature will be 25°C = 25 + 273 = 298 K.

So the maximum efficiency of the generator will be = (1 – 298/673) × 100 = 56%.

The concepts of entropy and the Second Law of Thermodynamics have expanded from describing the physical world to the workings of society as well. Within the focus on human migration, the emphasis lies with “left on its own, a system tends to evolve in such a way as to increase disorder,” Under this logic, immigration acts as an interrupter – the sovereign states are no longer left on their own. It’s an important step; while there are often disparities between the states, their cross-mixing can help with stability. In contrast, actively fighting against immigration negates that interruption.

Thermodynamics doesn’t have much to say about rate of the processes; it only describes the delicate equilibrium that so many states strive towards. If Donald Trump succeeds in building his high wall on the Mexican border, it will inevitably slow down immigration between the two countries. European countries, meanwhile, are themselves scrambling to construct barriers. This has an impact. What Physics has to say about the situation is actually rather self-evident: on a global scale, countries are competing to optimize their conditions and catch up with more developed states, but they face obstacles along the way.

I will continue this discussion in the next few blogs to try to highlight the consequences of this push-pull mechanism.

About climatechangefork

Micha Tomkiewicz, Ph.D., is a professor of physics in the Department of Physics, Brooklyn College, the City University of New York. He is also a professor of physics and chemistry in the School for Graduate Studies of the City University of New York. In addition, he is the founding-director of the Environmental Studies Program at Brooklyn College as well as director of the Electrochemistry Institute at that same institution.
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