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Laws of Thermodynamics
       Thermal refers to heat and dynamics deals with the motion of objects. Thermodynamics is the branch of physical science that deals with the relations between heat and other forms of energy (such as mechanical, electrical, or chemical energy), and, by extension, of the relationships between all forms of energy. In 1824, Sadi Carnot established the principle of thermodynamics, which eventually became the second law. The first law was developed by 1860. Three laws of thermodynamics are now accepted.
       The first law states that energy can neither be created nor destroyed. It can be changed from one form to another, but it is not possible to end up with more energy than originally existed. The second law says that, for a spontaneous process, the entropy of the universe increases. Entropy is a measure of disorder or randomness. That means that some energy is lost to entropy in any reaction. A simple way to picture this is in seeing how a moving ball eventually comes to rest. The third law states that, at zero Kelvin temperature, a perfect crystal has zero entropy. An easier way of picturing this is recognizing that there are no exceptions to the first two laws. When I was at MIT, we had a simplified way to express these three laws: You canít win; you canít break even; and you canít get out of the game.
       In quite a few science fiction stories, a central aspect of the plot is the development of a perpetual motion machine. This is a machine that operates forever without any external energy source. This would not be possible, as it would conflict with either the first or second law, or both. The U.S. Patent Office often receives applications for patents for perpetual motion machines. However, they have the simple policy of turning down any applications unless they are shown an actual working prototype.
       Some people raise questions regarding these laws, as plants generate food and energy, or how energy can be extracted from sources such as oil, gas or coal. The critical factor is that you must look at an entire closed system when applying these laws. The sunís energy is taken in by plants. Similarly, such energy was taken in eons ago when the components of oil, gas and coal were first created, thanks to photosynthesis. Earth absorbs the sunís radiation, and this is converted to chemical bonds. While this occurs, some energy is lost due to radiation leaving Earth. The net result is that some energy has always been lost due to entropy.
       As an example, hold a ball and let it drop. It does not return to the original height. This is showing how some energy has been lost in this simple reaction. I often asked my students to close their eyes while I repeated the experiment. I then asked them how many times the ball had bounced before I chose to catch it. They invariably were able to answer this question, even though they had had their eyes closed. When asked why this was possible, they replied that they heard the ball bouncing. I then pointed out that the sound produced was an example of energy lost to entropy.
       However, a greater portion of energy was lost as heat, especially when the ball bounced on the floor. Nonetheless, one is unable to physically discern the increased temperature of the ball or the floor. This makes it harder to accept this example of the second law. I therefore obtained a pair of metal balls. I would have numerous students hold up a sheet of paper, grasping it by a central point of the upper edge. I then went around the room, quickly hitting the metal balls together three times from opposite sides of each sheet of paper. In addition to hearing the noise, the students saw that holes had been burnt in the paper by the released heat, and they were likewise able to smell the burnt paper. This simple demonstration made it much easier for the students to understand and accept these basic laws.
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