Okay, it states that disorder in the universe must always be increasing. This is something I frequently run into when I debate a Christian, and I usually end up having to explain that the energy from the Sun allows complexity to increase on Earth.
But here’s a question that I cannot answer…today’s universe is certainly more orderly than the chaotic conditions of the early universe, shortly after the Big Bang. How did order increase? Doesn’t that violate the 2nd law?
My understanding of physics is rudimentary, but I think the idea is that order requires the expenditure of energy. At the beginning, there was lots of energy but little order; now there is less energy and more order.
The amount of energy in the universe never changes, so that can’t be the answer.
Playwright/screenwriter David Mamet, in his book “On Directing Film”, likens the process of storytelling to the 2nd law and suggests the intriguing idea that the common understanding of entropy is backwards - that the universe, like a good story, moves from disorder to order (unsolved problem to solution).
I suppose the answer depends on what you mean by order. If you ultimately choose to define order as that which entropy increases, then you’ve solved your own riddle. Otherwise we would have to challenge the assumption that there is, in fact, increasing order in the universe.
Entropy refers to the amount of heat that is transferred between two quasi-static equilibrium states. The Kelvin-Planck statement of the 2nd law states that it is impossible to have a heat engine which converts all heat into work (i.e. 100% efficiency). We cannot view the Universe as a reversible process because there are dissipative effects, therefore the system and its surroundings cannot be returned to their original state without producing any changes. Therefor the system (the Universe) must be irreversible. If there is irreversible transfer of heat than there is an increase in entropy.
However, the fluctuation theorem, which refers to changes in irreversible systems far from equilibrium, states that entropy will decrease as the system size increases. This contradicts the 2nd law as it says that entropy decreases, rather than increases. The FT has problems though when you use it to predict earlier states of the system.
Both the second law and the FT rely strongly on experimental data.
So yes, entropy in the Universe is decreasing and it violates the 2nd law.
Why are you assuming a Big Bang?
Entropy refers to the amount of heat that is transferred between two quasi-static equilibrium states. The Kelvin-Planck statement of the 2nd law states that it is impossible to have a heat engine which converts all heat into work (i.e. 100% efficiency). We cannot view the Universe as a reversible process because there are dissipative effects, therefore the system and its surroundings cannot be returned to their original state without producing any changes. Therefor the system (the Universe) must be irreversible. If there is irreversible transfer of heat than there is an increase in entropy.
However, the fluctuation theorem, which refers to changes in irreversible systems far from equilibrium, states that entropy will decrease as the system size increases. This contradicts the 2nd law as it says that entropy decreases, rather than increases. The FT has problems though when you use it to predict earlier states of the system.
Both the second law and the FT rely strongly on experimental data.
So yes, entropy in the Universe is decreasing and it violates the 2nd law.
Entropy is decreasing? I was under the impression that it is constantly increasing. The very expansion of the universe is an increase in entropy, if I’m not mistaken, and then there’s the fact that stars are constantly dying, amongst other things.
But let’s assume that entropy is increasing. If the current understanding of the universe flies in the face of the 2nd law, why do we still use it?
Why are you assuming a Big Bang?
Uh…well, because I’m not a Creationist. What other option is there?
Entropy is decreasing? I was under the impression that it is constantly increasing. The very expansion of the universe is an increase in entropy, if I’m not mistaken, and then there’s the fact that stars are constantly dying, amongst other things.
But let’s assume that entropy is increasing. If the current understanding of the universe flies in the face of the 2nd law, why do we still use it?
From the second law of thermodynamics entropy is always increasing. The second law is a physical law therefore cannot be derived, but relies on the fact that it can be proven true through experimental data. Not everything has already been discover. There are always ways we can improve previous concepts and just because the 2nd Law is accepted doesn’t make it an absolute truth.
Here is a link to the abstract for the article on FT. You’ll have to purchase the article if you want to read it. http://prola.aps.org/abstract/PRL/v71/i15/p2401_1
Why do we still use the 2nd Law? Probably for the same reason we still use Newtonian physics. It works within a certain range.
Uh…well, because I’m not a Creationist. What other option is there?
I thought the Big Bang was a theory meant to explain an alleged origin of the universe. If this is your view (I’m not saying it is) why must there be an origin of the universe?
My take here is that the concept of “order” is highly generalized beyond the actual meaning of the law.
It always amazes me when a Creationist presents this world as “highly ordered” as compared with the post big bang universe.
a. It’s pretty tough to measure entropy by looking at something
b. they weren’t there
c. “order” is not entropy
d. they are only looking at a localized systems
If I arrange a set of pennys on my desk in the shape of a star, is that “more ordered” than if they are in any random shape? It has nothing to do with the 2nd law.
Another way to think about it is based upon what the law actually says.
The 2nd law says that certain processes are irreversible, without work being added to the system. If you take any discreet system, the 2nd law doesn’t say that this system cannot proceed toward more “order”. It says that in order to do so, you have to add energy. If you take the earth as a very localized system where large amount of energy can be imparted to it such as by the sun, then there is nothing that says that the system can’t actually become more ordered. Or another example, 2nd law says heat flows from hotter to colder. Does that make an airconditioner a violator of the 2nd law? No, A/C adds work into the system to pump heat from colder to hotter.
Doesn’t entropy apply only to closed systems? That is, systems where there is no input of energy.
As for the Big Bang, it does not explain the origin of the Universe. If all matter and energy was concentrated in a super dense dimensionless point, then that’s what the Universe was like until the Big Bang ocurrred. Where it all came from, or whether it all came from anywhere, is unanswered by any of the Big Bang theories.
Doesn’t entropy apply only to closed systems? That is, systems where there is no input of energy.
As for the Big Bang, it does not explain the origin of the Universe. If all matter and energy was concentrated in a super dense dimensionless point, then that’s what the Universe was like until the Big Bang ocurrred. Where it all came from, or whether it all came from anywhere, is unanswered by any of the Big Bang theories.
The change in entropy is the amount of heat transferred (the inexact differential of QR) at a certain temperature (T). From the 1st Law of thermodynamics, the inexact differential of Q is the change of internal energy plus the inexact differential of work done in the system. So only internal energy is used to calculate entropy.
The thing about entropy is it doesn’t just apply to the system, you also have to take into account the entropy change of the local surroundings and the universe due to the process. All natural processes are irreversible and have an entropy change on the universe.
For those of you discussing the Big Bang - a professor at my university has proposed a cosmological model that seems to make much more sense to me (and which states that the universe has no beginning or end). You can read a newspaper article about it here.
I think we are getting confused about entropy. Some people are taking it to mean “disorder” or “randomness”, while some are taking it to have something to do directly with heat and energy. Dictionary.com includes both takes. My college-level chemistry class used the first sense for entropy, and for the second sense used “enthalpy.” This is probably a simplification, and I’m sure there is an alternative use of “enthalpy” for people who like to use the second take on “entropy,” but this simplification is a college-level one, so it’s good enough for me as a non-scientist.
To answer Moose’s question, there is no reason to believe entropy (disorder) is decreasing, i.e. the universe seems to me to be becoming more chaotic. That makes sense, since it’s expanding, and more particle interactions have historically taken place, so the state of the universe is farther removed from its original state; it would be more difficult to model; if there can be random interactions, more of them have taken place. This also applies to Earth, though you could use the energy coming from the sun argument to dissuade people who consider the Earth system to be decreasing in entropy (becoming more orderly).
For those of you discussing the Big Bang - a professor at my university has proposed a cosmological model that seems to make much more sense to me (and which states that the universe has no beginning or end). You can read a newspaper article about it here.
It seems like his own version of the Cyclical Universe. That’s a long-standing hypothesis that, as far as I know, ha neither been confirmed nor refuted as yet.
Let’s review (what i know):
The Universe has always existed pretty much as it is now and will always exist pretty much that way forever. That’s the Steady-State Universe theory. I’d say the known and proven expansion neatly refutes it.
The Universe existed for an inmeasurable time as a super dense point or sphere containing all the matter and energy currenlty existent in the Universe; it might ahve always existed in such a way. Then for reasons unkown it blew up and evolved to the universe we see today. Eventually the expansion, created by the Big Bang, and the increase in entropy, will mark an “end” to the Universe. It will still exist, but all energy will be in the form of dissipated heat which is unusable. In other words, something will exist forever, but without life or intelligence.
After a Big Bang the Universe expands. Eventually the expansion stops and some agency, be it gravity, or dark Energy, or the Cosmological Constant, draws all the Universe back into the small volume of a superdense mass, which eventually blows up in a Big Bang. This is the Cyclycal or Oscillating Universe hypothesis.
In all three cases, the Universe has always existed in some form and will always exist in some other form. Ergo, no creation or end of the Universe is known to exist, nor is it known whether such end or creation can exist or have existed.
Personally I favor the Oscillating Universe. It is orderly and makes sense. But science, as I am too fond of saying, is not a popularity contest. In any case, the Universe is eternal (has always existed, will always exist) even though it may or may not be constant.
Then there’s the question: does it matter?
Not immediately, it doesn’t. Not because the Big Bang or, if real, the “end” in dissipated energies are too far away in time, but because there is no ready, direct application of any of these theories to my daily life (except as grand schemes for SF stories, of which Fred Pohl is very fond). There are indirect aplications through scientific discoveries, but these are not necessarily related to any given theory.
It’s too bad we have access to neither the Restaurant At The End Of The Universe nor The Big Bang Burger Bar, isn’t it? :dough:
To answer Moose’s question, there is no reason to believe entropy (disorder) is decreasing, i.e. the universe seems to me to be becoming more chaotic. That makes sense, since it’s expanding, and more particle interactions have historically taken place, so the state of the universe is farther removed from its original state;
I agree completely. Where I’m confused is about how the universe got to it’s present state, without violating the 2nd law. Because surely today’s universe of galaxies and solar systems is more ordered than the early universe which consisted of really, really, really hot gaseous substances.
I agree completely. Where I’m confused is about how the universe got to it’s present state, without violating the 2nd law. Because surely today’s universe of galaxies and solar systems is more ordered than the early universe which consisted of really, really, really hot gaseous substances.
You misunderstand me - I am saying the universe has become continuously more disorderly throughout time (or, alternatively, as it has expanded).
I think you’d be hard-pressed to provide a definition of “order” that justifies calling the present state of the universe, with planets, galaxies, etc. more ordered than a previous, more condensed state.
Wasn’t American civilization more ordered when the only settlement was at Jamestown than it is today?
I agree completely. Where I’m confused is about how the universe got to it’s present state, without violating the 2nd law. Because surely today’s universe of galaxies and solar systems is more ordered than the early universe which consisted of really, really, really hot gaseous substances.
Why are you sure that the second law didn’t get violated?
Entropy refers to the amount of heat that is transferred between two quasi-static equilibrium states. The Kelvin-Planck statement of the 2nd law states that it is impossible to have a heat engine which converts all heat into work (i.e. 100% efficiency). We cannot view the Universe as a reversible process because there are dissipative effects, therefore the system and its surroundings cannot be returned to their original state without producing any changes. Therefor the system (the Universe) must be irreversible. If there is irreversible transfer of heat than there is an increase in entropy.
However, the fluctuation theorem, which refers to changes in irreversible systems far from equilibrium, states that entropy will decrease as the system size increases. This contradicts the 2nd law as it says that entropy decreases, rather than increases. The FT has problems though when you use it to predict earlier states of the system.
Both the second law and the FT rely strongly on experimental data.
So yes, entropy in the Universe is decreasing and it violates the 2nd law.
You made a pretty strong case for entropy increasing in your first paragraph, but then asserted that entropy is decreasing based on “experimental data” from a theory I know nothing about. Why, then, would you assume that entropy is not increasing? Is there a reason to believe that there is less entropy now than at some point in the past, and thus that we need to look for a way around the 2nd law?
I guess I’m responding to your question for Moose in the preceding post. Why are you sure the second law did get violated?
However, the fluctuation theorem, which refers to changes in irreversible systems far from equilibrium , states that entropy will decrease as the system size increases. This contradicts the 2nd law as it says that entropy decreases, rather than increases. The FT has problems though when you use it to predict earlier states of the system.
The emphasis is mine. How do we know that the universe is “far from equilibrium”?
I agree completely. Where I’m confused is about how the universe got to it’s present state, without violating the 2nd law. Because surely today’s universe of galaxies and solar systems is more ordered than the early universe which consisted of really, really, really hot gaseous substances.
Well, that’s just my point. How can you tell by looking at something that it is “more ordered” per the 2nd law?