Entropy
hideEntropy is a concept applied across physics, information theory, mathematics and other branches of science and engineering. The following definition is shared across all these fields:
where S is the conventional symbol for entropy. The sum runs over all microstates consistent with the given macrostate and is the probability of the ith microstate. The constant of proportionality k depends on what units are chosen to measure S. When SI units are chosen, we have k = kB = Boltzmann's constant = 1.38066×10−23 J K−1. If units of bits are chosen, then k = 1/ln(2) so that .
Entropy is central to the second law of thermodynamics. The second law in conjunction with the fundamental thermodynamic relation places limits on a system's ability to do useful work.
The second law can also be used to predict whether a physical process will proceed spontaneously. Spontaneous changes in isolated systems occur with an increase in entropy.
The word "entropy" is derived from the Greek εντροπία "a turning towards" (εν- "in" + τροπή "a turning").
For more information about Entropy, read the full article at
Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.
News tagged with entropy
Second Law of Thermodynamics May Explain Economic Evolution
Nov 02, 2009 |
4.3 / 5 (34) |
29
(PhysOrg.com) -- Terms such as the "invisible hand," laissez-faire policy, and free-market principles suggest that economic growth and decline in capitalist societies seem to be somehow self-regulated. Now, ...
Cosmic entropy could be 100 times greater than previously thought
Oct 06, 2009 |
4.3 / 5 (20) |
11
(PhysOrg.com) -- A new analysis of supermassive black holes has discovered the entropy of the universe is much greater than previously thought, which means it may also be very slightly closer to ultimate heat death.
Pushing the cold frontier in an orderly fashion
Sep 28, 2009 |
5 / 5 (4) |
0
Physicists are continually reaching new lows as they reduce the temperatures of samples in their laboratories. But even nano-kelvins are not low enough to overcome the entropy (a measure of the disorder in ...
How to Measure What We Don't Know
Sep 10, 2009 |
4.7 / 5 (24) |
11
(PhysOrg.com) -- How do we discover new things? For scientists, observation and measurement are the main ways to extract information from Nature. Based on observations, scientists build models that, in turn, are used to make ...
Physicist Proposes Solution to Arrow-of-Time Paradox
Aug 27, 2009 |
4.2 / 5 (73) |
108
(PhysOrg.com) -- Entropy can decrease, according to a new proposal - but the process would destroy any evidence of its existence, and erase any memory an observer might have of it. It sounds like the plot ...
Could Maxwell's Demon Exist in Nanoscale Systems?
Jun 24, 2009 |
4.4 / 5 (18) |
30
(PhysOrg.com) -- Maxwell’s demon may be making a comeback. Physicists know that the demon, an imaginary creature that decreases the entropy of a system, cannot exist in macroscopic systems due to the energy ...
Researcher finds optimal fix-free codes
Technology / Computer Sciences
Apr 03, 2009 |
4.6 / 5 (21) |
5
(PhysOrg.com) -- More than 50 years after David Huffman developed Huffman coding, an entropy encoding algorithm used for lossless data compression in computer science and information theory, an electrical ...
Entropyman.org Explains Why Pots 'Unbreak' on the Nanoscale (Video)
Feb 16, 2009 |
3 / 5 (4) |
6
(PhysOrg.com) -- A man lifts his hand in the air, and broken pieces of ceramic lying on the sidewalk spring up into his hand, coming together to form a flower pot. He lifts his hands again, and more broken ...
Researchers See Complex Atomic Choreography as Crystals Melt
Feb 02, 2009 |
4.5 / 5 (4) |
0
(PhysOrg.com) -- Conga lines of atoms wend their way through a crystal, their numbers growing as more and more atoms join the migration. The worm-like lines of atoms randomly converge, forming tangles that ...
Physicists investigate how time moves forward
Sep 05, 2008 |
4.2 / 5 (155) |
56
As humans, we have a very intuitive concept of time, and of the differences between the past, present, and future. But, as scientists Edward Feng of the University of California, Berkeley, and Gavin Crooks of the Lawrence ...
