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Battling Entropy

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Re: Battling Entropy

#41

Post by rocqua »

bocklund wrote: post #29

The definition of the second law of thermodynamics at the top is not right. A closed system can have energy put in from the surroundings to decrease entropy. Only isolated systems that cannot exchange energy with the surroundings follow the second law. Only the universe is truly isolated (see the common definition of the second law), You decrease the entropy (disorder if you like, or not) of things by putting energy…

> A closed system can have energy put in from the surroundings to decrease entropy.

Then it wouldn't be a closed system anymore.

What you call an isolated system is the same as a closed system. At least, in the common parlance of thermodynamics.

Re: Battling Entropy

#42

Post by have_faith »

dougk16 wrote: post #39
crimsonalucard wrote: post #38

People think that entropy increasing is basically atoms going from a state of organization to a state of random distribution. All you need to do is look at the universe to see how off this definition is. The universe started as a big bang: a soup of randomly distributed particles. Then the atoms proceeded to self organize into perfect spheres called planets and stars which in turn organized themselves into flat order…

I've always considered the "increasing disorder" definition of entropy to be a simple analogy that most people can relate to in their everyday lives, not necessarily a formal definition. Indeed I would be interested to know if you can even formally define order vs. disorder since it seems to require a subjective observer. For example the universe doesn't consider a glass sitting on the table to be "more ordered" than…

> Anyway I like to consider entropy as the amount of usable energy in a system. A whole glass has more energy to release (e.g. by shattering) than a shattered one does. Maybe this is the formal definition of order vs. disorder?

I think this is correct. Like the sand castle example: there are very few ways the grains can be arranged in order to be a sand castle, but orders of magnitude more ways of being re-arranged into a pile of sand. It could then be said that the sand castle has less entropy, and left to nature, will slowly but surely move towards the predictable high entropy state of being a pile of sand. The reverse is not true. Without work the low entropy state will struggle to reach the orderly state of the sand castle.

Someone else mentioned the big bang, which I guess would be the work that created the orderly universe as we see it. But that work was expressed a long time ago and without more work matter will just move to an un-orderly state again.

Re: Battling Entropy

#43

Post by rocqua »

crimsonalucard wrote: post #37
lovemenot wrote: post #32

Earlier quoted context omitted.

>> a perfectly uniformly distributed of zero temperature mass ... is the perfect order At max entropy, things would not be uniformly distributed: equal distance between each atom. Rather they would be randomly distributed. There'd be some clumping but without much pattern. If such a system were of near infinte size, the number of variations of its alignments would far exceed the much smaller near-infinity of slightly…

This is entirely incorrect. Our solar system started out as a gas cloud of randomly distributed atoms which then proceeded to become atoms organized into spheres called planets. This happened spontaneously and is not the result of energy entering or exiting the system. Almost all atoms started out in a state of random distribution before transforming themselves into almost perfect spheres orbiting in an almost perfec…

Wait, what happens if we look into the collapsing of the galaxy from an informational-theoretic view of entropy?

As far as I know, thermodynamic and informational-theoretic entropy are the same except for the Boltzmann constant. It certainly seems to me that the informational entropy of the galaxy is lower than the original gas cloud.

That is, if I wanted to describe the state of a single atom in the gas cloud (lets presume the number of atoms is constant) using a perfectly tuned compression algorithm, I'd need more bits to do it than if I wanted to do the same for an atom in the current galaxy (again using a compression algorithm perfectly tuned to that situation).

Perhaps, because the gas cloud was cold, but the galaxy is 'hot' we actually need more bits because the individual particles can go faster, and thus have a larger range of possible speeds? Is this indeed enough to compensate for the much easier to describe location? Do I need to take more than just location and speed into account?

Re: Battling Entropy

#44

Post by bocklund »

rocqua wrote: post #41
bocklund wrote: post #29

The definition of the second law of thermodynamics at the top is not right. A closed system can have energy put in from the surroundings to decrease entropy. Only isolated systems that cannot exchange energy with the surroundings follow the second law. Only the universe is truly isolated (see the common definition of the second law), You decrease the entropy (disorder if you like, or not) of things by putting energy…

> A closed system can have energy put in from the surroundings to decrease entropy. Then it wouldn't be a closed system anymore. What you call an isolated system is the same as a closed system. At least, in the common parlance of thermodynamics.

Closed means mass cannot go in or out. Heat and work can still be exchanged.

See https://en.m.wikipedia.org/wiki/Isolated_system

Re: Battling Entropy

#45

Post by rocqua »

drekembemutombo wrote: post #30
Rainymood wrote: post #6

>The second law of thermodynamics states that “as one goes forward in time, the net entropy (degree of disorder) of any isolated or closed system will always increase (or at least stay the same).”[1] That is a long way of saying that all things tend towards disorder. This is one of the basic laws of the universe and is something we can observe in our lives. Entropy is simply a measure of disorder. You can think of it…

Entropy is more accurately defined as hidden information, or the number of possible microstates that a system in a certain macrostate could have. Here's a great lecture by Leonard Susskind on the topic: https://www.youtube.com/watch?v=n7eW-xPEvoQ

What distinguished macrostates from each other? What distinguishes a macrostate from a microstate?

Re: Battling Entropy

#46

Post by crimsonalucard »

dougk16 wrote: post #39
crimsonalucard wrote: post #38

People think that entropy increasing is basically atoms going from a state of organization to a state of random distribution. All you need to do is look at the universe to see how off this definition is. The universe started as a big bang: a soup of randomly distributed particles. Then the atoms proceeded to self organize into perfect spheres called planets and stars which in turn organized themselves into flat order…

I've always considered the "increasing disorder" definition of entropy to be a simple analogy that most people can relate to in their everyday lives, not necessarily a formal definition. Indeed I would be interested to know if you can even formally define order vs. disorder since it seems to require a subjective observer. For example the universe doesn't consider a glass sitting on the table to be "more ordered" than…

"Useable energy" is vague word and thus not a good description.

There is a quantitative definition of entropy but it is based in a way off of "opinion". Given a system and its laws look at all possible final states. Then group the states according to an arbitrary "rule"

For example: the state of white marbles and black marbles in a jar.

What is the number of possible arrangements of all black marbles to be arranged on the left side of the jar and all white marbles to be arranged on the right? This is an arbitrary "rule." It's a big number but that number is much lower than every other possible arrangement.

From these quantities you can derive an entropy value.

However you will note that it depends on that "rule" you define. I could point to the state of marbles in the jar after I shake it and call that my "rule" and it makes that arbitrary state one of low entropy. I could point to any arbitrary state and do this and thus any specific state is one of low entropy. It's a complex definition and it encompasses "opinion" and "choice." The definition of entropy allows for an numerical value to be derived based off of your "opinion."

In Boltzmann's definition, entropy is a measure of the number of possible microscopic states (or microstates) of a system in thermodynamic equilibrium, consistent with its macroscopic thermodynamic properties (or macrostate).

The macrostate is basically what I defined above as "rules" and what you defined as "opinion."

Re: Battling Entropy

#47

Post by cygx »

kgwgk wrote: post #18
dr_dshiv wrote: post #8

Entropy has been increasing since the big bang, when it was at minimum value. While the total energy didn't change since then, there has been a vast increase in the potential locations of that energy and a vast increase in the number of different interactions possible within that energy. This increases entropy because the possibility space has increased. Boltzman entropy is defined as the number of potential microsco…

Thermodynamical entropy is not a physical property of a system. It’s a property of our description of the system as a macroscopic state. Quantum (von Neumann) entropy is a related but different concept. It’s worth noting that it is constant for a closed system. Cosmological entropy can be defined in different ways. In summary, entropy means many things and not all “entropies” behave in the same way.

Thermodynamical entropy is not a physical property of a system.

From a thermodynamic point of view, it is: As ΔS = ΔU/T and assuming one holds temperature and inner energy to be physical properties, then so is entropy.

Re: Battling Entropy

#48

Post by crimsonalucard »

rocqua wrote: post #43
crimsonalucard wrote: post #37

Earlier quoted context omitted.

This is entirely incorrect. Our solar system started out as a gas cloud of randomly distributed atoms which then proceeded to become atoms organized into spheres called planets. This happened spontaneously and is not the result of energy entering or exiting the system. Almost all atoms started out in a state of random distribution before transforming themselves into almost perfect spheres orbiting in an almost perfec…

Wait, what happens if we look into the collapsing of the galaxy from an informational-theoretic view of entropy? As far as I know, thermodynamic and informational-theoretic entropy are the same except for the Boltzmann constant. It certainly seems to me that the informational entropy of the galaxy is lower than the original gas cloud. That is, if I wanted to describe the state of a single atom in the gas cloud (lets…

I'm less familiar with the information perspective of this topic.

Why would you need more bits to describe a single atom in a galaxy vs a single atom in a gas cloud?

If a set amount of bits are required to describe an atom then that amount will not change whether or not the atom is in a galaxy or a gas cloud.

Re: Battling Entropy

#49

Post by kgwgk »

cygx wrote: post #47
kgwgk wrote: post #18

Earlier quoted context omitted.

Thermodynamical entropy is not a physical property of a system. It’s a property of our description of the system as a macroscopic state. Quantum (von Neumann) entropy is a related but different concept. It’s worth noting that it is constant for a closed system. Cosmological entropy can be defined in different ways. In summary, entropy means many things and not all “entropies” behave in the same way.

Thermodynamical entropy is not a physical property of a system. From a thermodynamic point of view, it is: As ΔS = ΔU/T and assuming one holds temperature and inner energy to be physical properties, then so is entropy.

The thermodynamic point of view is a description of the system as a macroscopic state.

Re: Battling Entropy

#50

Post by cygx »

kgwgk wrote: post #49
cygx wrote: post #47

Earlier quoted context omitted.

Thermodynamical entropy is not a physical property of a system. From a thermodynamic point of view, it is: As ΔS = ΔU/T and assuming one holds temperature and inner energy to be physical properties, then so is entropy.

The thermodynamic point of view is a description of the system as a macroscopic state.

And properties of macroscopic states are 'unphysical'?
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