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The three laws of thermodynamics |
According to the first law of thermodynamics, energy can be neither created nor destroyed, but only changed form one form to another. The second law of thermodynamics states that in any energy transformation, not all energy is transferred. Some of the energy will be lost because no transformations are 100 percent efficient. As a result of the second law, we obtain the third law, which states that all processes tend toward increased entropy or dissorder. As the avialable energy decreases in a system, the system becomes highly disorganized. And these are the judicial decisions that god has set before us. |
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The End of Days |
Every culture has its myth for describing the beginning of human life on earth; as well as predictions for what the end of days will be like. Modern science has allowed human kind to consider human life on earth from a scientific, thermodynamic point of view, and our quest for those secrets has drained the very life out of us. Too late we realize that the meaning of life is beyond our reach and we can only examine its components. Indeed, modern science provides more believable although highly simplistic explanations for the nature of human life on earth and eons of its evolution. However, neither mythology nor science guarantees that life on earth will exist forever. In order to visualize the end of human life on earth one must first become familiar with the various processes that keep the machinery of life going. From a thermodynamic point of view that machinery has being found to possess not only a high level of complexity but at the same time a high degree of simplicity in terms of the variables that describe it. When making a thermodynamic analysis it is hard to believe that the earth is nothing but a tiny dot in a gigantic galaxy. But the earth is one of the few or probably the only planet in the galaxy that can support human life and that makes the earth more important than other larger planets. Why the earth? At the atomic level that question is hard to answer. All elements found on earth exist anywhere else in the universe and only a few of them are required to create life. Living matter consists of a relatively small number of elements; in fact, C, N, O, Ca, P, K, and S account for nearly 98% of the dry weight of most living things (about 70% of the mass of the human body is water). Life is though to have originated with the formation of complex biological macromolecules from simple molecules found on the early stages of the formation of our planet. The simple molecules that could serve as starting material for the formation of macromolecules can be made from its elements by providing energy in the form of lightning. This long process could have occurred in any other planet, or couldn't it? Indeed it could. In theory any planet in the universe the same mass and size is a potential life generator provided that it is located near a star at a distance comparable to our sun to earth distance. The nature of the atmosphere of such a planet depends on what elements or molecules can attain speeds that equal or exceed the escape speed of the the planet. Compare the average molecular speed of hydrogen or hellium with that of the escape speed of the earth (7900 m/s) and you will know why hydrogen and hellium are so scarce in in the earth's atmosphere. The remaining molecules and elements could, at least in theory generate life. The earliest known fossil evidence of life on earth is about 3.5 billion years old. All life forms that exist today are said to have evolved from that first inferior organism by the process of evolution. That statement clearly disagrees with the third law of thermodynamics, which requires the entropy of a system to increase with time. Evolution is a process that goes towards order. That statement can be better understood by dividing the earth into subsystems. If those subsystems are small enough and the interaction between the subsystem and its surroundings is assumed to be very weak, then the total entropy of the subsystem can be defined as: Where Ns is the total equilibrium entropy of the subsystem and I the decrease in the total entropy resulting from self-organization. If we evaluate the process using thermodynamics we can clearly see that the equation makes the process energetically unfavorable since the term (-TdS ) becomes positive. If we neglect the enthalpy factor (dH) of the equation, then the change in free energy (dG) becomes positive. Notice that negative free energy change is a criterion for spontaneity, that is, a process occurs spontaneously if the change in free energy is a negative quantity. Then a positive (dG) value indicates that a process such as evolution is not spontaneous and life has to spend energy in order to remain organized. As more advanced life forms have come to exist so has the need to store greater amounts of genetic information. The human genome consists of 46 chromosomes packed to fit in an extremely small space. The entropy of genetic material has decreased over time! Evolution is not as spontaneous as it might seem just by looking at nature's tendency to go towards increasing complexity. It then becomes clear that life requires energy; and since the human body and the earth are clearly not closed systems (a human cannot keep 5 liters of beer in its body; the earth receives and releases energy). The sun is the source of energy that sustains life on earth. Plants use that energy to convert inorganic, high entropy raw materials (CO2, H2O) into lower entropy/high free energy organic compounds (glucose) that the human body can use. According to the second law of thermodynamics the conversion of low entropy foods such as glucose into higher entropy components is a spontaneous process that provides free energy. A chemical reaction that supports life and would not occur spontaneously (such as ATP synthesis) can be made to go with the free energy provided by low entropy foods. As a result, life cannot exist without a source of energy and an energy gradient that causes it to flow. Could such apparent contradictions of the laws of thermodynamics have originated in a place of the universe other than planet earth? The chances of that happening become smaller if one considers the most important requirement for life on earth to exist. Namely that one of the reasons why the earth and no other planet of the solar system is able to support human life is due to the abundance of water on its surface. The thermodynamic properties of water are a key factor for the survival of human life. Biological macromolecules that make up the human body assume their shape and function in response to their component's hydrophilic or hydrophobic character. Water is the medium for biochemical reactions within the body; in fact, water itself acts as product or reactant in many chemical reactions that support life. The unusually high heat capacity of liquid water is responsible for the regulation of temperature within the human body and the environment. For life to exist in another planet, water would first have to be formed. All living systems generate heat from the biochemical reactions in their metabolism. Vaporizing water is an effective way of dissipating the heat generated by metabolism, which could cause a temperature raise of about 40 degrees per day on an average weight person if the human body were adiabatic. The regulating effect of water on the temperature environment can be easily seen in the difference of climate between cities that are near large bodies of water and cities that are located in the middle of deserts. During the day, the high heat capacity of water allows it to absorb large amounts of energy from the sun without a substantial increase in temperature. At night, the same thermodynamic property allows the water to release energy into the environment. Deserts are hot during daytime and cold at night because there are no large bodies of water to regulate the environmental temperature. The winter and the summer are colder and hotter respectively. Another property that makes water into the source of life is its low thermal conduction. Water could be boiled at its surface and the bottom part would not get hot. That property and water's decrease in density with temperature makes life in the oceans possible. Ice stays at the surface of the water and even provides insulation for the fish below. An entire lake may freeze and the bottom will still be at a temperature at which living organisms can survive. As we have already seen, life on earth is less complex when evaluated from a thermodynamic point of view. However, there are questions that cannot be answered by the laws of thermodynamics alone. The evolution process is one of those aspects of human life that do not follow the simple patterns we can envision based on a thermodynamic model. The complexity of planet earth can be made less complex by looking at each individual component that makes life possible. The water content of the planet's surface, the gasses that compose the atmosphere, the process of photosynthesis, and the sun's energy are the main reasons why earth can support life. With our newly obtained knowledge of the thermodynamic properties of human life on earth we are ready to predict the end of days. Let's first consider a theory that is based more on philosophy than science: The Circle of Life. Until now humankind and all living systems that exist on earth have managed to violate the laws of thermodynamics by becoming more advanced. However, the process of evolution cannot possibly lead to perfection. Some people believe that the process of evolution is actually an infinite loop. Once humankind reaches a given peak on the evolutionary process it is dammed to restart the loop all over again. That place on the loop could be a nuclear war on which most of human life and the technology that humankind has created would be destroyed. The remaining survivors would have to use their animal instincts in order to survive in this new harsh environment. That is analogous to going back to the Stone Age and starting the development of human civilization all over again. A more realistic possibility is human kind's self destruction along with all the thermodynamic aspects that make planet earth suitable for supporting human life. It is clear that the earth cannot possibly last forever. Humankind has turned its back on the preservation of the environment. As a result, the composition of our otherwise perfect atmosphere is changing for the worse. Global warming might even be causing some of the vital gases to exceed the earth's escape speed. The water, vital for the chemical reactions that support the very existence of human life has been polluted beyond recovery. And in our quest for domination over one another we have built weapons of mass destruction powerful enough to vaporize the entire planet. Even if we evolve to a point where we learn to let our hearth control our mind and thus avoid a final conflict which would mean the end of all life on earth, the third law thermodynamics predicts an end. This takes us to the theory of a death by entropy. Life depends on energy gradients for it to continue, that is, living system is not an equilibrium system. It is a known fact that when an organism dies those gradients disappear. I believe the reverse statement best explains reality. It is the disappearance of those gradients that causes death. Our universe is no different from any other system in terms of thermodynamic stability. And since the energy of the universe is a constant so must be the space that encloses it. The end of days will come when the entropy of the universe becomes homogeneous. Without regions of low and high potential the energy that supports life on earth will stop flowing. Without energy the earth will no longer be able to support any kind of life. It is hard to accept that kind of an end for such a beautiful planet. However, since the beginning of time, the third law of thermodynamics has been known to be a heartless entity, and with time we have all learned to accept its predictions, and this is no different from any other. Those are the predictions for the end of days. Have a nice day. | |||||||||||||
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