The science of thermodynamics is the science that studies energy, it’s ability to transform into different forms, and the difference between energy that is useful from energy that is useless. Indeed energy comes in a variety of forms such as gravitational energy, kinetic energy or energy of movement, and the energy of light as examples of the forms of energy but what exactly is energy, anyways? Energy, basically, is nothing more but the ability to do work such as in the case of gravitational energy, of causing a rock to fall from a cliff, or when throwing a baseball, you exert energy in the form of directed movement to the ball which then flies along a given trajectory, or in the case of light, the ability to power the biochemical process of photosynthesis which is universal through the terrestrial biosphere.
If you have read my blogs, most of them are about the connection between life and thermodynamics and how life is made possible because of thermodynamics so this will be a simplified version of these previous related blogs on the subject of life and energy.
There are two well established laws of thermodynamics, both of which have been supported by observations and experiment, and to which no exceptions have ever been found, disproving them, and they are the first law of thermodynamics or simply the law of energy conservation and the second law or the law of increasing entropy.
Before talking about these laws in details, I will first simply summarize these two laws before explaining them in detail for both laws talk about energy but there is a difference; the first law talks about the quantity of energy while the second law is about the quality of energy.
The first law of thermodynamics states that energy comes in many forms, each can be converted into one form or another but the total amount of energy is constant. No energy can disappear completely nor can extra energy come from nothing. In short, it is really a conservation law which says that the total energy or E as it is called in physics literature is constant.
Here is an example to illustrate the first law; imagine you are in a room and you have a basketball. You throw the basketball as high up in the air as you can, and as the basketball goes up, it will then come down and bounce several times before coming to rest.
Let’s see this in detail from using the first law. To throw the basketball up in the air, it takes a certain amount of energy to have the basketball at a given height above you. Where did the energy come from in order to bring the ball up at that height? That energy came from the food that you have eaten which is then powering the muscles needed to throw the ball upward. The energy of metabolism or the set of biochemical processes that converts food into energy such as muscular movement for example, has been converted into the kinetic energy of the ball.
The kinetic energy of the ball is then converted into another form of energy and that is the potential energy which is the energy of position where kinetic energy is the energy of motion. The potential energy depends only on the mass of the object such as the mass or the amount of matter present making up the basketball and the height above the floor.
The basketball will eventually come down because the force of gravity pulls down on the ball at the height and the potential energy changes back into kinetic energy and so the ball falls, as it hits the ground, the balls rises above the floor, and the kinetic energy it received from impact then converts into potential energy and back into kinetic energy and the ball keeps doing this until the ball is now at rest on the floor.
From this example, you can now see that energy changes into many forms but if you calculate the kinetic energy which is simply the mass of the ball multiplied by the square of the velocity or the velocity multiplied by itself two times divided by two for each up and down movement, along with the potential energy which is the mass of the ball multiplied by the height and multiplied by a constant called g or gravitational constant of the earth’s surface, you will find that for each conversion of kinetic and potential energy, the total energy E is constant. It will be constant, if you repeat the experiment many times and find that E never changes. That is what the first law predicts, the energy may change into different forms but the total amount is always the same.
So much for the first law but what about the second law and how is it different from the second law? Recall that the first law is about the quantity of energy and from this imaginary example, you can see how the first laws deals with the quanity of energy which is constant. I have said that the second law is about the quality of the energy and the quality of energy is expressed as the increase of the entropy or S as it also called. What is the entropy?
Let’s return to our room with you throwing the basketball. As you have played basketball, you know that everytime you throw the ball, it bounces on the floor and will eventually stop bouncing.
Why would the ball stop bouncing? Well, energy is converted into two forms, potential and kinetic. Let’s assume that the wall, which is assumed to be perfectly flat or that on the microscopic level, there are no bumps or crevasses, just flatness. Also, let us assume that the inside of the room is a vacuum or that there is no air and you then throw the ball and the ball will bounce. With a perfectly smooth floor, also assume that the surface of the ball, like the floor, is also perfectly smooth. If all assumptions are true, then the ball will bounce up and down, with kinetic energy changing into potential energy and back to kinetic, the ball will be doing this again and again and it will never come to rest and will end up bouncing up and down forever!
Of course, we know that never happens and for one things both the surface and ball are imperfectly shaped and on a microscopic level, the floor does have tiny bumps and crevasses and the ball of course is covered with bumps and crevasses also so the energy of movement will eventually decrease until the ball stops bouncing.
What has happened to the kinetic energy? It turns out that the kinetic energy after the ball bounces before finally coming to rest is converted into a completely different form and that form of energy is heat. Heat is a form of energy or rather a form of kinetic energy that is really random and it turns out this randomness is the reason why movement of objects comes to a stop.
To understand is to know the difference between energy that does work such as lifting up the basketball to the same ball coming to rest and to understand is to see matter at the molecular level.
When our ball has kinetic energy, let us see the atoms making up the ball as the ball flies upward. What will we see if we could look at the atoms and how will they behave when the entire object has kinetic energy? If we could see all the atoms, we would notice that the atoms are all flying in the same direction as the ball. What would happen when the ball hits the floor? At the moment of impact, as the atoms of the ball collide with the atoms of the floor both the atoms will move in various directions and speed. Suppose you can take the temperature of the impact; you will find that the temperature will increase a tiny bit. That increase in temperature is the heat and at the molecular , heat is nothing but the random movement of atoms. Also go back to the definition of energy which as you know is the ability to do work.
Work, in physics, is the distance an object moves multiplied by the force exerted on the object. Energy can alter the work such as the basketball falling down because of gravity since gravity is a force acting on the falling ball and the balls does fall down at a given distance ( this is of course different from the everyday use of the word “work” but it is more subtle and precise than the everyday use of the word).
What we notice that when doing work, all the atoms move in the same direction but when the kinetic energy of the ball allows it to fall to the floor, the atoms begin to move randomly in all directions and we found that this represents the heat being given off. The ball hits the floor several times followed by an increase in the amount of heat until the ball is at rest and at that point, no more heat is given off.
From this example, we can then understand the difference between the two laws. In the first law, energy changes form which defines the total energy but as energy is converted, there is another form of energy, heat, which is really a disorganized form of energy which increases but up to a point and everything comes to a complete standstill called equilibrium. At equilibrium, no more changes can occur. All useful energy such as the directed motion of the bouncing ball will end at equilibrium.
For the second law, the processes that convert energy into useless heat, there is a name for this one way direction towards equilibrium and if you have read my blogs, or for that matter had physics courses in high school and/or college or like me, reading books about physics and biology, you will notice know the name where everything comes to a stand still, and that is entropy.
The second law states that for every form of energy, which is something that is organized, there is a corresponding increase of entropy which roughly measures the amount of disorganized energy or in other words, entropy is the amount of disorder of which there can be no further changes once entropy has reached a maximum amount. This is what I meant by the quality of the energy. The quality of usable energy decreases until equilibrium is reached such as the ball coming to rest because at each bounce as well as at each height above the floor, the energy of movement is causing random motion on the floor as well as the random motion of all the atoms making up the air.
The conclusion for the second law is that as the entropy S increases, the amount of usable energy to do something organized decreases until equilibrium is reached and no more changes can occur.
This is basically the essence of the second law which is really a law of decreasing order. This was the conclusion reached when the second law was formulated during the latter part of the nineteenth century. Originally the law had it origin in the study of steam engines and the question was whether it was possible to design a steam engine that can be the most efficient in doing useful work from turning a large wheel to generating electricity, another form of energy, and it was found you can but in order to do so, you have to create waste such as heat from the engine or rather creating disorder somewhere else for it was found that there could be no useful order without disorder being created in the external environment.
The conclusion that was then reach is that if everything in the universe depends on energy, then for every process that uses energy, entropy is being created and as the entropy increases, then eventually the whole universe will become more and more disordered. This was the pessimistic conclusion that was reached when the second law was first formulated.
But, if the physical universe is presumed to be running into disorder, then there was a part of the universe, such as the earth, that seemed to be doing the opposite and this came from a different field of science, biology.
As the laws were being derived in the final form, and in 1859, Charles Darwin published On the Origin of Species which states that because of a mechanism called natural selection which was something that was found by Darwin, all of life are evolving into various forms, most of which are becoming more and more complex than their predecessors.
The observation that entropy increases while complexity increases in biological evolution results in a paradox, a paradox that cannot be avoided. Basically, if the universe is increasing in disorder, then how or why life is increasing in complexity more or less? Is there something “magical” about life? If it is can we find out what this magic is?
Before biology became a legitimate science, it was indeed believed that there is something magical about life or that life has some inner “spark” that makes it go and at first life a life form such as butterfly or earthworm is indeed different from a rock for both butterfly and earthworm move about, change in form and behavior from fertilized egg into adult and actively seek out food and mates which is completely different from a rock that can only move in response to external forces such as gravity.
Ever since the discovery in 1828, that organic compounds, which were assumed to by made only by life forms, could easily be synthesized by inorganic compounds and as the science of biochemistry or the study of the chemical basis of life revealed that the same atoms found in the inorganic world are the same as that found in life forms and plus there is no evidence at all of a “spark of life” in all life forms. Both life and nonlife are subject to the same laws of physics and chemistry and to date, there is nothing found in life form that contradicts what is observed in the physical universe such as the first law of thermodynamics for it is applicable in biology as it is in physics.
We now then return to paradox I mentioned is how can the evolution of life be compatible with the second law of thermodynamics. The paradox begins to fade when we consider how the science of thermodynamics was originally formulated.
Recall that thermodynamics , which had its beginnings in trying to improve steam engines, was originally formulated by considering the study of systems or a part of the universe being studied. The law of increasing entropy was discovered through the study of isolated systems and these are systems that are completely isolated from matter and energy coming and also going out.
From the study of isolated systems, came the conclusion that energy decreases while entropy increases until no changes occur. We now know that although useful, isolated systems are really artificial and nature is anything but an isolated system.
In biology, every living thing is dependent on other living things; organisms depend on food for metabolism and other organisms for reproduction, in the case of sexual reproduction, but even organisms that carry out asexual reproduction still depend on their environment for survival much like those that use sex for reproduction. Also an organism is adapted to its local environment which consists of other species of organisms along with its abiotic components such as water and temperature. Each species present is the result of a long evolution of species that have adapted to each change in its environment and every species makes up an ecosystem which may or may not overlap with other varying kinds of ecosystems. Any waste produced will end up either being food for other organisms such as the fungi that thrives on wood from dead trees as well as the oxygen released from every green plant is used by animals whether it is in the same place or from another part of the content while the carbon dioxide exhaled from every animal goes back to every green leaf to begin photosynthesis wherever there is sunlight.
Let us suppose we can place an earthworm and butterfly in an isolated system and what will happen? Being in a isolated system, both the worm and butterfly will die simply because it will be unable to access food, oxygen, and another worm and butterfly of the opposite sex. Entropy has increased and from this experiment, the second law is applicable to the biological world.
However, it is different when the worm and the butterfly, or every other life form is in its ecosystem, although individuals complete a life cycle from birth to death, the species on the whole survives, and evolves because of natural selection as well as other evolutionary mechanisms and that presence of one species can affect the survival or death of other species. In biology, there is a degree of relationships where one is dependent on the other and in ecoystems, these are the complete opposite of isolated systems for they are open systems where matter and energy flows in and flows out.
It is with open systems where the paradox disappears for order can increase but only at the expense of disorder somewhere else so in addition to the total entropy increasing, there can be an increase in organization which corresponds to a decrease in entropy. This can only happen only if matter in the form of nutrients is allowed to flow into an organism’s environment and energy which begins as sunlight streaming down on green plants and starting with plants, the energy of sunlight is turned into carbohydrates , which includes sugars and starch, and in an indirect way the synthesis of proteins and DNA and through photosynthesis the creation of an energy rich molecule called ATP , found in all plants, fungi, animals, and microorgansims, where the breakdown of ATP releases energy for a variety of biological functions. Plants are then food for animals adapted to the process of breaking down carbohydrates whether in the form of cellulose and/or starch and these animals become food for other animals such as birds that prey on caterpillars up to tigers stalking bigger prey. Energy is passed from plant to caterpillar up to bird to hawk while the elements are also passed up to the biggest predator. As energy is being passed, it is also used in organizing the structure and function of each organism such as for the caterpillar preying on the leaf, the energy is used in preparation for turning into a butterfly. The energy that is used in the tissues of the caterpillar is also used as food for a hungry bird who uses some of that energy for flight, while the bird, being captured by the hawk, is also passed on to the hawk for flight as well as for reproduction.
For every amount of available energy or free energy as it is called, it is then converted into heat, in accordance with the first law and second law. While the total entropy increases, which is something that happens on a larger level, at the smaller level, it can increase but also decrease so not only entropy can increase but it can decrease and this is only possible if we are dealing with open systems for life is an example of an open systems. Energy is converted into heat while some of it allows life to grow, reproduce, and evolve. The atoms such as carbon and nitrogen also flow but sooner or later they have to be recycled for the next generation of life forms and that is accomplished whenever each organism dies where the atoms it had in order to give it life, will be used by other life forms but each life form from hawk to bacteria needs these atoms so the fact that each atom is being passed in between atoms reveals that life is part of a network, made possible by the second law for in every biochemical reaction, heat is generated to the environment.
Ultimately, all of this is because the earth is at a distance from the sun and because of nuclear fusion where four hydrogen atoms are fused into one helium atom releasing a tremendous amount of energy and from core to surface, results in sunlight which is generated at the hot surface and radiates in all direction and earth, in its orbit around the sun, only intercepts a tiny amount of the sunlight where it is used to power photosynthesis while starting at photosynthesis and also for every organisms that depends on either plants or on organisms that have eaten plants, respiration where carbohydrates as well as proteins and fats are combined with oxygen generating energy in the form of ATP, and in doing, a total amount of heat in the form of infrared is released whether from life forms along from the ground, mountains, and clouds, into the cold of outer space, never to be use again and for 3.8 billions of years, it is this flow of useful energy, in the form of sunlight along with the flow of infrared heat into space that has allowed life to evolve and complexify.
The paradox is then resolved only by considering the open systems that is nature can we then understand the power of the second law not just to create disorder but it is because of the amount of disorder that is the reason for why life can coexist in a universe that is dominated by the second law so the second law not only can take life but creates it as well.
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