Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Duan Gauche on 04/06/2009 20:30:02
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Duan Gauche asked the Naked Scientists:
Hello Chris,
Thanks for all your wonderful podcasts (http://www.thenakedscientists.com/HTML/podcasts/) on 702 I really enjoy them and the simple way in which you explain complex science to simple beings :-)
Could you please explain what is meant by: moving from high entropy to low entropy
Thanks you,
Duan Gauche
What do you think?
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Entropy according to Websters:
A measure of the energy unavailable for useful work in a system, the tendency of an energy system to run down.
Therefore; High Entropy would indicate less energy available for useful work in a system. Low Entropy would suggest greater energy availability.
In our Universe, The Law of Entropy suggests that as time passes, less and less energy will become available for use. In some respects, Entropy is equivalent to the arrow of time................Ethos
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If the universe is eternal and steady state there must be some mechanism that reverses entropy. I suspect that ours might be such a universe. If so, the entropy reversing mechanism would be within galaxies.
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If the universe is eternal and steady state there must be some mechanism that reverses entropy. I suspect that ours might be such a universe. If so, the entropy reversing mechanism would be within galaxies.
I agree Vern, someday the evidence for this may become clear. Right now, we can only wonder about the various possibilities.
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One example of moving from high entropy to low entropy is tidying up your desk drawer. Entropy is a measure of disorder. To decrease entropy requires energy. Clearing up certainly knackers me!
To decrease the entropy, locally involved increasing the entropy of the Universe by more than the local decrease you obtained. That's, in effect, another statement of Thermodynamic Law.
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I'm afraid that I can't go along with the idea of entropy being a measure of order or information - it's too subjective; would you describe some of Jackson Pollack's artworks as increasing or decreasing entropy? If I were to spill a bag of rice on the floor it would normally be described as a reduction of entropy, but if I were to then gather up the rice and then deliberately arrange the grains on the floor in exactly the same pattern it would be regarded as an increase in entropy.
In purely energy terms though it is quite clear, and in line with the Webster definition of the term; entropy is the flow of energy down the gradient between two different energy levels.
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Does entropy working also inside nucleus of atoms all a time?
If not, WHY not?
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I'm afraid that I can't go along with the idea of entropy being a measure of order or information - it's too subjective; would you describe some of Jackson Pollack's artworks as increasing or decreasing entropy? If I were to spill a bag of rice on the floor it would normally be described as a reduction of entropy, but if I were to then gather up the rice and then deliberately arrange the grains on the floor in exactly the same pattern it would be regarded as an increase in entropy.
(Statistics isn't subjective and entropy applies to information).
Actually, that's precisely what's going on. When molecules of a hot gas mix with molecules of a cold gas, the overall entropy has increased; you've mixed things up..
Spilling rice is, essentially, increasing entropy because getting them back in the jar would involve energy being put in.
Separating the fast molecules from the slow molecules (go on - try) would be the equivalent of re-sorting out your grains. The reconstructed pattern would have just as much information introduced (order) to it as if you lined them up into regular rows. Both actions would require energy to achieve, and wouldn't occur by chance (V. unlikely).
Look at a book on statistical thermodynamics; it's part of the explanation of these things.
p.s. I think you're getting defensive about the tidiness of you desk drawer.
Dunno whether thermodynamics can be applied to nuclear situations. I guess it would, only with different statistics.
If JP's painting turned out exactly as he had planned in his mind, then the entropy could be said to be minimal.
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...you've mixed things up..
Oops! [:I]
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That's entropy for you! :)
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Lol [:D]
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If the universe is eternal and steady state there must be some mechanism that reverses entropy. I suspect that ours might be such a universe. If so, the entropy reversing mechanism would be within galaxies.
This new theory may be suggesting something akin to what you're saying Vern. Time will only tell whether this theory finds support amongst those in the know. I find it a very interesting proposal myself. Nevertheless, those with a better understanding than I will judge how far this idea goes, and I will be waiting to hear our members views and or criticisms.
http://news.yahoo.com/big-bang-deflated-universe-may-have-no-beginning-140017504.html
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there must be some mechanism that reverses entropy. If so, the entropy reversing mechanism would be within galaxies.
It is possible to reverse entropy on a local scale (like a bag of dropped rice, or life on the planet Earth) by applying additional energy from outside the system. However, this energy must come from some source; considered as a whole system, the entropy increases over a long time, even though some parts of it decrease (temporarily and locally).
In the case of the Earth, you could say the life is in the business of decreasing its own entropy. But it does this by consuming energy from external source - usually light from the Sun, if you trace it back far enough.
The Sun gets its energy from nuclear fusion - turning hydrogen into helium, producing energy. But in the process, access to that energy is lost - some is lost in the form of neutrinos, which fly away into space. Other energy is lost in that if you try to fuse two Helium nuclei into a Beryllium nucleus, you don't release nearly as much energy. By the time you have iron nuclei, you can't get any more energy out of them by fusion.
So the local decrease in entropy of life on Earth (or sorting a bag of rice) is far exceeded by the increase in entropy of the Sun. So yes, entropy can occur at the nuclear scale, in a star.
Since the galaxy is made of stars, I guess you could say "the entropy reversing mechanism would be within galaxies".
(How this plays out at the scale of the entire universe is beyond my experience...)