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Posted: Thu Aug 31, 2006 1:07 pm
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Energy is subject to the law of conservation of energy (which is a mathematical restatement of shift symmetry of time). Thus, energy cannot be made or destroyed, it can only be converted from one form to another, that is, transformed. In practice, during any energy transformation in (macroscopic) system, some energy is converted into incoherent microscopic motion of parts of the system (which is usually called heat or thermal motion), and the entropy of the system increases. Due to mathematical impossibility to invert this process (see statistical mechanics), the efficiency of energy conversion in a macroscopic system is always less than 100%.
The first law of thermodynamics states that the total inflow of energy into a system must equal the total outflow of energy from the system, plus the change in the energy contained within the system. In other words, energy is neither created nor destroyed, only converted between forms. This law is used in all branches of physics, but frequently violated for short enough periods of time during which energy can not be mathematically defined yet (see quantum electrodynamics and off shell concept). Noether's theorem relates the conservation of energy to the time invariance of physical laws.
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Posted: Thu Aug 31, 2006 1:23 pm
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Posted: Fri Sep 01, 2006 6:18 am
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Posted: Fri Sep 01, 2006 6:18 am
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Posted: Fri Sep 01, 2006 6:19 am
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Posted: Fri Sep 01, 2006 6:23 am
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Posted: Fri Sep 01, 2006 6:24 am
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Posted: Fri Sep 01, 2006 6:30 am
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Posted: Fri Sep 01, 2006 10:23 pm
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Posted: Fri Sep 01, 2006 10:23 pm
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Posted: Fri Sep 01, 2006 10:24 pm
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Posted: Fri Sep 01, 2006 10:25 pm
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Posted: Fri Sep 01, 2006 10:26 pm
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Posted: Sat Sep 02, 2006 7:34 am
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Posted: Sat Sep 02, 2006 11:50 am
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