Disorder: Is it really increasing?

[Deepak Kapur]

Scientists say disorder is increasing?

How come that we have well-orderd galaxies (from randomness) with the passage of time (many are in the process of evolution)?

How come elememts have combined together to form cells and eventually living beings.

How come humanbeings have started to live in an orderd state (cities, countries, etc.) from the disorderd/less ordered state of hunters?

 

[SpectraCat]

Scientists say disorder is increasing?

How come that we have well-orderd galaxies (from randomness) with the passage of time (many are in the process of evolution)?

How come elememts have combined together to form cells and eventually living beings.

How come humanbeings have started to live in an orderd state (cities, countries, etc.) from the disorderd/less ordered state of hunters?

When scientists say that the disorder is increasing, we are talking about the net entropy of the entire universe, which must increase according to the second law of thermodynamics. All of your examples represent *local* increases of order ... the second law tells us that the driving forces that allowed each of these cases to come about must have caused increases in entropy in the surrounding universe that were greater than the decrease in entropy represented in the local systems.

The first statement seems incorrect ... galaxies did not form out of randomness. They formed from clouds of interstellar atoms and molecules which represented a system with higher potential energy than a galaxy. The process of galaxy formation releases some of this energy back into the surrounding universe in such a way that the overall entropy is increased.

The second two statements reflect processes which required the input of significant amounts of energy, all of which ultimately derived from our sun. The nuclear processes that cause the sun to emit energy also increase its entropy, so that the net entropy changes of the universe from these processes are positive.

I realize that these answers may seem a bit solipsistic if you don't have a background in thermodynamics, so I will be happy to clarify as best I can if you have specific questions.

 

[Deepak Kapur]

When scientists say that the disorder is increasing, we are talking about the net entropy of the entire universe, which must increase according to the second law of thermodynamics. All of your examples represent *local* increases of order ... the second law tells us that the driving forces that allowed each of these cases to come about must have caused increases in entropy in the surrounding universe that were greater than the decrease in entropy represented in the local systems.

The first statement seems incorrect ... galaxies did not form out of randomness. They formed from clouds of interstellar atoms and molecules which represented a system with higher potential energy than a galaxy. The process of galaxy formation releases some of this energy back into the surrounding universe in such a way that the overall entropy is increased.

The second two statements reflect processes which required the input of significant amounts of energy, all of which ultimately derived from our sun. The nuclear processes that cause the sun to emit energy also increase its entropy, so that the net entropy changes of the universe from these processes are positive.

I realize that these answers may seem a bit solipsistic if you don't have a background in thermodynamics, so I will be happy to clarify as best I can if you have specific questions.

1. Is there any proof of the second law of thermodnamics other than the mathematical one?

2. Suppose, the entropy of the universe becomes maximum. I think that would be the state of the bigbang or just after it. So, if entropy was already maximum, why it decreased to increase again.

 

[Gerenuk]

Scientists say disorder is increasing?

How come that we have well-orderd galaxies (from randomness) with the passage of time (many are in the process of evolution)?

How come elememts have combined together to form cells and eventually living beings.

How come humanbeings have started to live in an orderd state (cities, countries, etc.) from the disorderd/less ordered state of hunters?

There is a probability derivation of the second law which shows that the increase in entropy is nothing else than saying for coin flips the most likely outcome is a ratio 1:1 between head and tails.
In order to use thermodynamics for galaxy or biology you need to indentify a correct notion of entropy which is basically based on $S=\ln\Omega$. This won't be what you think is disorder.
The point is that high entropy is something completely different from what you think when it comes to more complex system rather than bouncing molecules. So thermodynamics doesn't apply the way you might think.
Look at the list
http://www.math.utk.edu/~vasili/refs/darpa07.MathChallenges.html
There is a reason why there are so many problems which related to thermodynamics like problem, but can't be solved with it. It's just not useable there.

In my view SpectraCat has a too much specialized picture of thermodynamics, but I'm not in the mood to explain to him again. So I advice you to think about what $S=\ln\Omega$ means and how the second law derives from it. I've had a discussion with someone recently and I can post the results in a moment. Don't trust SpectraCat or even me. Make up your own thoughts!

 

[DaveC426913]

1. Is there any proof of the second law of thermodnamics other than the mathematical one?

Um. There are no proofs except mathematical ones. If you're looking for physicality, you only get evidence.

2. Suppose, the entropy of the universe becomes maximum. I think that would be the state of the bigbang or just after it.

No. That is when it was at its minimum. When it is maximized is at its death, called The Big Freeze.

 

[jack action]

2. Suppose, the entropy of the universe becomes maximum. I think that would be the state of the bigbang or just after it. So, if entropy was already maximum, why it decreased to increase again.

http://en.wikipedia.org/wiki/Entropy#Entropy_and_cosmology"

How come elememts have combined together to form cells and eventually living beings.

How come humanbeings have started to live in an orderd state (cities, countries, etc.) from the disorderd/less ordered state of hunters?

Like SpectraCat said before, you have to look at it on a universe scale. Form wikipedia about http://en.wikipedia.org/wiki/Entropy#Entropy_and_life":

In short, according to Lehninger, "living organisms preserve their internal order by taking from their surroundings free energy, in the form of nutrients or sunlight, and returning to their surroundings an equal amount of energy as heat and entropy."

 

[silentbob14]

Yeah the entire universe is a closed system, whereas Earth is not, so entropy in our planet can increase and decrease as well. Though, when I think about it, both the lowest state of entropy and the highest state of entropy of the universe have some similarities.

 

[DaveC426913]

Yeah the entire universe is a closed system, whereas Earth is not, so entropy in our planet can increase and decrease as well. Though, when I think about it, both the lowest state of entropy and the highest state of entropy of the universe have some similarities.

Such as?

The lowest entropic state is just after the BB, the highest is when all matter and energy (including heat) are distributed uniformly across the universe.

 

[bapowell]

1. Is there any proof of the second law of thermodnamics other than the mathematical one?

Sure. Have you ever seen heat spontaneously flow from a cold body to a hot body to which it is in thermal contact?

Of course this isn't proof as DaveC points out, but should be sufficient to convince you that the 2nd law is physically manifest.

 

[Gerenuk]

Sure. Have you ever seen heat spontaneously flow from a cold body to a hot body to which it is in thermal contact?
Of course this isn't proof as DaveC points out, but should be sufficient to convince you that the 2nd law is physically manifest.

This would only "proof" that heat doesn't flow between gases in particular. I think people here mean any process and not just gas dynamics.

Also you know the microscopic physics behind gases. So you cannot make a second law on top of it and claim both never fail. You better proof consistency between these two laws.

It's not hard, but only the people who know how to do it, can judge better what entropy means.

 

[DaveC426913]

This would only "proof" that heat doesn't flow between gases in particular. I think people here mean any process and not just gas dynamics.

He was not suggesting one test would prove anything. Make up any tests you want. Feel free.

In the history of scientific study, the law has always held. That is as close as you're going to get to proof.

 

[Andy Resnick]

<snip>
How come that we have well-orderd galaxies (from randomness) with the passage of time?

<snip>

I think this question deserves more attention, because it's not at all obvious (to me) how best to answer. On the face of it, you are right: a dust cloud seems to have a high entropy, but a spiral galaxy seems to have a low entropy- how can this occur?

Calculating the entropy of a self-gravitating dust cloud may be more interesting than it first seems, I didn't find a clear reference:

http://adsabs.harvard.edu/full/1981SvA...25..127D

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V3S-4DGW31W-3&_user=10&_coverDate=01%2F01%2F2004&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1292667338&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=c3624c6a814d392e02234796efadde6f

Does anyone have a good reference?

Edit: section 2.2 of this has some references-
http://kipac-prod.stanford.edu/collab/research/ac/galaxies/classical-and-modern-galaxy-formation

 

[bjacoby]

Yeah the entire universe is a closed system, whereas Earth is not, so entropy in our planet can increase and decrease as well. Though, when I think about it, both the lowest state of entropy and the highest state of entropy of the universe have some similarities.

And the way you know the universe is a closed system is?

 

[silentbob14]

And the way you know the universe is a closed system is?

Well nobody is 100% sure, but maybe the laws of conservation of mass and energy suggest this.

 

[silentbob14]

Such as?

The lowest entropic state is just after the BB, the highest is when all matter and energy (including heat) are distributed uniformly across the universe.

Well yes your right. However, theoretically, in case of a big crunch both the state after BB and the end of the universe would look similar. And yeah I know big freeze is a more possible end of the universe.

 

[SpectraCat]

And the way you know the universe is a closed system is?

That is taken as a postulate, and has never been shown to be incorrect. Perhaps a cosmologist could provide a more refined answer, but from what I have read, most speculations to the contrary belong to the realm of philosophy.

 

[jrlaguna]

The entropy of the universe as a whole is quite independent of the galaxies, nonetheless, it is mostly at the cosmic background radiation. The decrease because of the order created by the structures is negligible with respect to the total.

 

[nonequilibrium]

Although parts of the universe are in equilibrium (like a gas in a chamber), the universe in a whole is actually not, continuously expanding. So we can't actually demand it is continuously increasing in entropy, can we? It's still evolving to its equilibrium! Let's assume the big crunch is the destiny of the universe, then the universe is now already trying to reach that "equilibrium" state by slowing down. But that would imply the big bang was actually one big breach of the 2nd law. Then again, the big bang happened before time, and as soon as it happened and as soon the 2nd law came into existence, it started going to the equilibrium state of the big crunch.

Maybe I'm just talking out of my ***, it sure sounds like that reading it myself, but it is a very interesting issue worth its pondering...

 

[SpectraCat]

Although parts of the universe are in equilibrium (like a gas in a chamber), the universe in a whole is actually not, continuously expanding. So we can't actually demand it is continuously increasing in entropy, can we? It's still evolving to its equilibrium! Let's assume the big crunch is the destiny of the universe, then the universe is now already trying to reach that "equilibrium" state by slowing down. But that would imply the big bang was actually one big breach of the 2nd law. Then again, the big bang happened before time, and as soon as it happened and as soon the 2nd law came into existence, it started going to the equilibrium state of the big crunch.

Maybe I'm just talking out of my ***, it sure sounds like that reading it myself, but it is a very interesting issue worth its pondering...

If we consider the universe to be a closed system, then in thermodynamic terms:

"evolving towards equilibrium"="increasing in entropy"

 

[nonequilibrium]

Touché, but I was kind of allowing fluctuations. But anyway I agree, it should decrease generally over time.

But incidentally, in the 2nd part of my post I do continue as if I presume entropy should increase so I still stand by that half of my post. Mainly: is it correct to say that if the big crunch is the end of the universe, (1) the universe is continuously increasing its entropy by slowing down for the crunch, (2) the big bang was a breach of the 2nd law (if the 2nd law can be applied to it...)

The weird thing is, aren't there some sources saying the expansion of the universe is increasing?

 

[bapowell]

The current expansion of the universe is in fact accelerating.

With regards to your big bang comment; are you referring to a big bang following a big crunch as in a cyclic universe? If so, the entropy of the universe in each cycle is always larger than in the preceding cycle.

 

[nonequilibrium]

I wasn't referring to the big bounce and rather stopped thinking at the moment of the big crunch. But your comment truly baffles me. The entropy would be larger each time? But what about our intuitive sense that there's a fresh start each time? People say we can't say ANYTHING about things before the big bang, because the big bang started our universe, but you say somehow entropy transfers? I would disagree, entropy is a statistical quantity, how could that possibly influence new universes...

 

[bapowell]

In a cyclic model, then there is a fully deterministic theory that explains how each phase contracts, big crunches, big bans, expands, contracts, and so on. In a cyclic model, the big bang of the expanding phase is the big crunch of the preceding contraction. So, there's nothing magical going on. One can show that the entropy increases at each new cycle. But, obviously this is getting far off topic, since this is not what you were suggesting ;)

 

[Deepak Kapur]

If we consider the universe to be a closed system, then in thermodynamic terms:

"evolving towards equilibrium"="increasing in entropy"

The primeval energy of the big bang gave rise to subatomic particles, these particles coalesced into simpler atoms, then heavier atoms were created etc. etc...

What kind of a disorder is it? ( a very ordered one , I think)

 

[jrlaguna]

I insist: you're looking at a small fraction of the whole universe: matter. The trend to order of matter is counterbalanced by the much larger increase in the entropy of radiation. Exactly the same as on Earth: yes, order increases continuously here, evolution and all that... but only at the expense of the increase in the entropy of radiation by the Sun.

 

[Deepak Kapur]

... but only at the expense of the increase in the entropy of radiation by the Sun.

Would you like to explain?

 

[SpectraCat]

The primeval energy of the big bang gave rise to subatomic particles, these particles coalesced into simpler atoms, then heavier atoms were created etc. etc...

What kind of a disorder is it? ( a very ordered one , I think)

First of all, you are talking about processes that happened *spontaneously*, and the second law of thermodynamics is quite explicit about such processes, they *must* increase (or keep constant) the overall entropy of the universe. Now, I guess your questions would be something like, "How does that happen, because didn't we go from diffuse sub-atomic particles, to atoms, to molecules and planets? That looks like increasing order to me!" Am I correct?

Jrlaguna's response is essentially correct, but allow me to expand on it a bit.

Part of the answer is that those more complex (or more ordered) systems above represent systems with lower potential energy than the ones preceding them. Therefore by conservation of energy, energy must have been released during their formation from the higher energy configurations. A useful (but incomplete) definition of entropy is configurational freedom ... systems with more available configurations have higher entropy than systems with fewer available configurations.

So you are correct that the more complex groupings of matter have lower entropy, because particles that were free to move in any direction before are now constrained to move collectively. Now consider the energy released during the formation of the complex systems ... that energy can be released in many different forms .. such as particles being cast off to carry away kinetic energy, but most likely it is released by different forms of radiation. As Jrlaguna said, because there are so many ways that this radiation can be released, the entropy corresponding to the many configurations of the released energy is more than enough to compensate the decrease in entropy from from the formation of the complex systems.

 

[Deepak Kapur]

First of all, you are talking about processes that happened *spontaneously*, and the second law of thermodynamics is quite explicit about such processes, they *must* increase (or keep constant) the overall entropy of the universe. Now, I guess your questions would be something like, "How does that happen, because didn't we go from diffuse sub-atomic particles, to atoms, to molecules and planets? That looks like increasing order to me!" Am I correct?

Jrlaguna's response is essentially correct, but allow me to expand on it a bit.

Part of the answer is that those more complex (or more ordered) systems above represent systems with lower potential energy than the ones preceding them. Therefore by conservation of energy, energy must have been released during their formation from the higher energy configurations. A useful (but incomplete) definition of entropy is configurational freedom ... systems with more available configurations have higher entropy than systems with fewer available configurations.


So you are correct that the more complex groupings of matter have lower entropy, because particles that were free to move in any direction before are now constrained to move collectively. Now consider the energy released during the formation of the complex systems ... that energy can be released in many different forms .. such as particles being cast off to carry away kinetic energy, but most likely it is released by different forms of radiation. As Jrlaguna said, because there are so many ways that this radiation can be released, the entropy corresponding to the many configurations of the released energy is more than enough to compensate the decrease in entropy from from the formation of the complex systems.

Thanks for your explanation.

Two questions arise in my mind.

1. Does it mean that entropy of radiation can never decrease as opposed to matter. What is pair production then?

2. It seems to me that the 'state' that we are discusing when particles/different kinds of raditiaon were free to move before the formation of atoms/molecules (complex systems) is the same as that would be before the 'Big Freeze'. The first one is usually given as an example of 'low entropy' and the latter one as that of 'high entropy'. Why this similarity?

Do correct, if I am in the wrong.

 

[SpectraCat]

Thanks for your explanation.

Two questions arise in my mind.

1. Does it mean that entropy of radiation can never decrease as opposed to matter. What is pair production then?

Certainly not ... simple absorption, where the energy of a photon is converted into internal excitations of matter, certainly decreases radiation entropy. However in that process, the photon is (usually) randomized over many internal degrees of freedom of the molecule within a short time after the absorption, in which case the overall entropy is increased. If it is an atom that absorbs the photon, then it will exist for some short time in the excited state, until which point it undergoes spontaneous emission, returning the system to its original state, with no net change in entropy.

2. It seems to me that the 'state' that we are discusing when particles/different kinds of raditiaon were free to move before the formation of atoms/molecules (complex systems) is the same as that would be before the 'Big Freeze'. The first one is usually given as an example of 'low entropy' and the latter one as that of 'high entropy'. Why this similarity?

Well, as you obviously realize, this cannot be correct. I am approaching the limit of my understanding of the cosmology here, as I understand it, the Big Freeze corresponds to a completely homogeneous distribution of matter and energy throughout the universe ... since it is completely homogeneous, there is no potential energy, so there are no longer any driving forces to make processes occur. This is completely different from the situation after the big bang ... as you say, the sub-atomic particles were distributed throughout space, but the distribution was far from homogeneous. Those inhomogeneities, which were confirmed recently by the observation of the Cosmic Microwave Background (or CMB), mean that there were regions of high and low potential energy, and thus ample driving forces existed to start the formation of matter. I have heard some theories that there was a very short time following the big bang where the 2nd law of thermodynamics did not apply, but I understand that those are unconfirmed and fairly controversial. As I said, cosmology is not really my field, but I am reasonably sure that the explanation I have given is at least qualitatively correct.

 

[Deepak Kapur]

SpectraCat;2676032]

As I said, cosmology is not really my field, but I am reasonably sure that the explanation I have given is at least qualitatively correct.

Yes indeed it is.

It would be highly appreciable, if you can rope in the services of some 'subject expert' on this forum in this regard. I am totally new here.