Hindsight is an exact science. Unknown philosopher

A. Some History

Among the environmental conditions that have occupied human attention forever is the matter of heat and cold. We get heat from the sun; we wear clothing to ward off the cold. Pretty basic.

As the scientific tradition took hold in the seventeenth century, thinkers began to speculate on the nature of heat. Were there two substances--heat and cold--as there were two kinds of charge? Or just one? Was heat a fluid called caloric that was released from objects under certain circumstances, such as combustion? Or was heat a mechanical process dealing with molecular motion? The battle over an explanation of heat escalated in the eighteenth and nineteenth centuries and began to take on its modern form with the work of Benjamin Thompson, J.P.Joule, and Rudolf Clausius. It was Thompson who, while overseeing the boring of brass cannons for the Bavarian military, caused to be discarded the caloric theory of heat, installing in its place the notion that heat probably was mechanical and related to friction. Joule, you will find, is responsible for what is known as the law of conservation of energy, coming to this conclusion while looking for improvements in his family's brewing business. Clausius is usually associated with the second law of thermodynamics, a probabilistic rule that governs processes in nature.

http://chemweb.richmond.edu/~rubin/pedagogy/132/132note_14.html

B. The First Law of Thermodynamics

The first law is a formalization of what is commonly known as the law of conservation of energy-energy may take on different forms in some process or event, but the amount of energy present is constant and can be accounted for.

http://chemweb.richmond.edu/~rubin/pedagogy/132/132note_21.html

C. The Second Law of Thermodynamics

This is a rather complicated idea related to something called entropy, a measure of disorder. The second law predicts, for instance, that time only runs from past to future and not the other way around. Events that could happen under the first law are prohibited by the second law. The matter is also clouded by the fact that the second law is based on the PROBABILITY of how nature is likely to behave. (Earlier in the couse, we defined a law as a statement of how nature ALWAYS behaves. Should nature behave differently, we change the law.)

A particularly delightful treatment of this topic can be found at http://www.secondlaw.com

Psst? Wanna buy a perpetual motion machine? cheap?
http://ourworld.compuserve.com/homepages/bob_jenkins/whythere.htm

http://www.phys.virginia.edu/classes/109N/more_stuff/Applets/Piston/jarapplet.html

Go to problems at U Oregon
http://www.zebu.uoregon.edu/~probs/therm.html

On-line - kinetic theory if gases
http://www.geocities.com/CapeCanaveral/Lab/5589/idealGas.html
http://www.arachnoid.com/sky/index.html

http://ericir.syr.edu/Projects/Newton/10/lessons/AirPrss.html

SIDE BAR
Exploratorium
http://www.exploratorium.edu/snacks/snacksbysubject.html

Newton's Apple
Newton’s Apple is a popular offering from PBS featuring applications in science.

LONG TERM ASSIGNMENT

Click on PHYSICS PEOPLE to find a list of people who have made a significant contribution to thermodynamics. A writing assignment awaits you there.

References - For useful references regarding this biography, or any topic in mechanics, go to
REFERENCES.

Last edited 01/01/06

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