Entropy can be reset to a previous or to an initial state

Reply to god must be atheist Quoting god must be atheist

then entropy is such that it can be reset to a previous state

It can, but it won’t. That’s sort of the whole point. Statistically speaking, it is almost impossible for entropy to decrease in a complicated system

Reply to god must be atheist
If time is a closed circle, then we can get to a stage where the entropy reaches the maximum value possible and suddenly it becomes ordered. The question deals with the arrow of time. Is time a linear line or a circular path

Reply to khaled
Entropy increases with time but if time is a circular path, does that cause entropy to decrease at the starting point.

Reply to Wittgenstein Quoting Wittgenstein

but if time is a circular path

This is almost impossible. It will mean the world has to keep returning to an initial state over and over again. That makes you think our world works this way?

Reply to khaled
I won't talk about possibility as that is clearly beyond our scope here. We are nor physicists. Time being a circular path is possible

'Entropy' is a human concept linked to their other concepts 'time', and 'events'. Without considering human requirements in defining 'order of events' relative to their reference frames, all talk of 'the world' tends to be meaningless.
NB 'What works' equates to 'what is predictable for humans', nothing more more and nothing less.

Reply to Wittgenstein or it isn't.

When we say something is possible, in these kinds of situations, it can have two meanings which often get conflated.

One is a factual understanding: It is possible to have the light switch on 'on' or on 'off'. Those are real possibilities, which we can in fact test. There can be all sorts of this type of possibility.

The other possibility has to do with our limited knowledge: it means, more of less, for all we know X is possible. Or 'we cannot rule out X' given our limited knowledge.

I think saying Time being a circular path is possible is of the latter kind of assertion. IOW it may not be possible, in the first sense at all. But perhaps, for all we know it might be the case. The nature of reality might utterly rule out this 'possibility'. And some might be able to make a case we already know that.

If the universe existed eternally, and if all events have a finite duration, then everything that could have happened, would have finished already.

Reply to Wayfarer Can you expand on this? I'm not sure it follows. Could it not be that there are infinitely many finite events.

Reply to fresco I would say entropy is a physical event recognized by humans as such. Not merely a human concept divorced entirely from reality.

Reply to Wayfarer Quoting Wayfarer

If the universe existed eternally, and if all events have a finite duration, then everything that could have happened, would have finished already.

Yes, and then the events would repeat again and again and again.

Everything possible not only has happened, but has happened an infinite number of times.

And that would be impossible if entropy was not something that could be reset to an earlier state.

Reply to khaled Quoting khaled

It can, but it won’t. That’s sort of the whole point. Statistically speaking, it is almost impossible for entropy to decrease in a complicated system

I thought that it couldn't. It turns out that it not only can, but it does. Much smarter men and women figured this out. I researched the topic because I wanted to publish my idea, and it turns out the physicists have already figured out the time span at the end of which entropy resets. Don't ask me, I forgot the value, it's some huge number of picaseconds. And I have no clue why, how, and in what process entropy gets reset.

Quoting edicts fiori gilt

Can you expand on this? I'm not sure it follows. Could it not be that there are infinitely many finite events.

I think Wayfarer meant that there are two cosmic clocks: one gets reset every so often, and that is the clock, so to speak to the time that it shows the world's events are tied to, on a one-to-one bases, accountably to every infinitely small or finitely large moment or span of time; and there is another clock, that keeps on ticking and not getting reset every time the circular clock does. The clock that keeps on ticking conceptually can measure the time elapsed between many circular time-universes.

Think of it as years. In each year we have the months repeating from january to december inclusive. Then this repeats. But we have years, also. The repeating months would be the circular modus operandi, and the years, the straight-line counter. The entropy would be tied to the circular time, and on the straight scale, it would appear to reset itself, while on the circular clock it would not be noticable how and when it resets itself.

Only closed systems are statistically required to increase in entropy. According to our current understanding, our universe is not a closed system: there is a continuous (but not constant; currently it is accelerating) influx of dark energy. The theory of eternal inflation holds that it was a runaway acceleration of this energy of space itself, or rather a local sudden stopping of such a runaway acceleration that is otherwise continuously ongoing everywhere, that gave rise to the "initial" energy-dense state of the universe as we know it; and the currently accelerating expansion is our local universe gradually returning to the eternally-inflating state of the rest of it.

I have hopes that some day we will figure out a way to harness that energy of the expansion of space itself as a way of providing unlimited energy with which to maintain life forever. There's something like 2000% as much dark energy as there is energy of ordinary matter as we know it, so if we could manage to capture even around 5% of that, we could literally recreate the entire universe of ordinary matter that we know, over and over and over again, as long as we wanted. No need to worry about even protons decaying over unfathomably long periods of time, if we can always make more.

Quoting Pfhorrest

Only closed systems are statistically required to increase in entropy

It's not a statistical reality. Energy levels equalize, via heat transfer. They can't unequalize. This leads to the depletion of useful energy, as work (change) can only be attained by using the energy between two unequal energy states.

I think your concept of entropy is way different from mine. I don't know what yours is; I just described mine. It would be helpful for me to know what you mean by entropy.

Reply to Pfhorrest The expanding universe model has many, many theoretical explanations, and none defy the continuing event of entropy.

The second law of thermodynamics happens as a result of statistical mechanics: more-entropic states are definitionally more likely than less-entropic ones, so over time dynamical systems will tend to evolve toward more-entropic states. See here for further explanation. It's the same law you're talking about, just understood at a deeper level.

That's not the point though; "statistically" was just me being pedantic, because in principle it is possible for entropy to randomly decrease, it's just unbelievably unlikely, so it felt wrong to just write "required" without the "statistically" qualifier.

The point is that the second law of thermodynamics doesn't require that an open system with more energy pouring into it eventually wind down to maximal entropy. The Earth, for example, doesn't wind down to maximal entropy because we have the sun pumping new energy into our ecosystem all the time. The second law still applies on Earth, things do wind down, but so long as there is a constant influx of new energy they can keep winding down without ever hitting bottom.

Dark energy is precisely such a new influx into the universe as a whole. The second law still applies, things do keep winding down, but with a constant influx of new energy they don't have to ever hit bottom.

Quoting Pfhorrest

Dark energy is precisely such a new influx into the universe as a whole.

Okay, I get it. Thanks.

The problem with this is that the entire universe, in its infinite expanse, whether it contains finite or infinite amount of matter, is a closed system. You restrict your observation to the observable universe, the universe we call known or seen or observed universe. But space is infinitely large, and together it is a closed system.

To take your analogy of Earth and Sun: sure nuff, Earth gets an influx of useful energy from the sun, but the sun has its own process of entropy, so the closed system of Earth, will deplete the open system too, which includes (in this example) only the sun as the 'outside' part of the closed system.

The entire infinite space with infinite matter, the whole system is a closed system.

Quoting edicts fiori gilt

Can you expand on this? I'm not sure it follows. Could it not be that there are infinitely many finite events.

Not sure that I can. It’s a one-sentence paraphrase of an argument I read about but I don’t have enough information to elaborate on it. But it makes intuitive sense to me.

Quoting Pfhorrest

According to our current understanding, our universe is not a closed system:

Do you think that has any bearing on the ‘causal closure’ principle beloved by materialist philosophers? (Which is that every physical event has a physical cause.) Science doesn’t know what ‘dark energy’ (or dark matter) are, so how can they say they’re physical, when they’re not even described by current physics?

Quoting Wayfarer

Science doesn’t know what ‘dark energy’ (or dark matter) are, so how can they say they’re physical, when they’re not even described by current physics?

I think this is a misunderstanding. Current physics do describe "dark matter" and "dark energy". These names describe physical phenomena that have been observed. The name implies that these phenomena are different from other phenomena in that they interact only in very specific ways, not that they're outside of physics.

Quoting god must be atheist

The entire infinite space with infinite matter, the whole system is a closed system.

Well we don't really know that, do we? It seems logical on its face, but we can only establish the laws of physics for the observable universe. In a way the observable universe is just a visualisation of the laws of physics. Beyond the observable, all bets are off.

Quoting Echarmion

Current physics do describe "dark matter" and "dark energy". These names describe physical phenomena that have been observed.

They have *never* been observed. There's an inference that they must exist because of their effect, but nobody has a clue about their nature. Dark matter is said to be non-baryonic, that is, doesn't consist of the same types of particles that regular matter does, but nobody knows what it might be.

Can it be a too difficult process though? Perhaps entropy cannot.

Will it all just fade away some day? Is this permenant?

Quoting god must be atheist

The problem with this is that the entire universe, in its infinite expanse, whether it contains finite or infinite amount of matter, is a closed system.

Not according to current theories of physics. "Closed system" means no energy enters the system or leaves it. But according to current physics, new energy is constantly being created everywhere; and if eternal inflation is correct, then in most places it is being created far faster than it is in our observable universe, and it's only a temporary pause in it that allowed the structure we see in that observable universe to form.

Quoting Wayfarer

Do you think that has any bearing on the ‘causal closure’ principle beloved by materialist philosophers? (Which is that every physical event has a physical cause.) Science doesn’t know what ‘dark energy’ (or dark matter) are, so how can they say they’re physical, when they’re not even described by current physics?

The principle of causal closure is about what counts as physical. Anything that has a physical effect counts as a physical thing. We observe physical effects (galaxies rotating faster than we would otherwise expect should be possible without flying apart, and galaxies accelerating away from each other faster that we would otherwise expect), and we don't yet know what is causing them, so we give whatever those things are placeholder names, "dark matter" and "dark energy". But since they have physical effects, whatever those things turn out to be count as physical things.

Quoting Wayfarer

They have *never* been observed. There's an inference that they must exist because of their effect

Almost everything we have learned about the universe in the past few hundred years has been learned through indirect observation. We see effects on things we can directly observe, posit something we can't directly observe as the cause of those effects, and then check if other effects we would expect from such a thing are also observed or not. That's how basically all of science works.

Quoting Pfhorrest

new energy is constantly being created everywhere

Coming into existence, then. Hard to imagine how this could be observed, isn't it? Or what kind of physical theory could account for that?

Quoting Pfhorrest

They [dark matter/energy] have *never* been observed. There's an inference that they must exist because of their effect
— Wayfarer

Almost everything we have learned about the universe in the past few hundred years has been learned through indirect observation

I think that's too broad a generalization. There's been an enormous amount of direct observation in astronomy. I understand where the dark matter conjecture comes from - that according to current physics, galaxies ought to fly apart, something must be preventing that from happening. As physics is basically physicalist, then the placeholder for that 'something' is named 'dark matter', but we ought to make it clear, that nobody knows what 'dark matter' is or even if it is real.

Quoting Wayfarer

Coming into existence, then. Hard to imagine how this could be observed, isn't it? Or what kind of physical theory could account for that?

No? We observe it happening. We just don’t have an account of why yet.

Quoting Wayfarer

As physics is basically physicalist, then the placeholder for that 'something' is named 'dark matter', but we ought to make it clear, that nobody knows what 'dark matter' is or even if it is real.

We know it is real, we just don’t have much of account of what it’s like besides the basic stuff we observe about it (weakly interacting, massive, about how much there is and how it’s distributed in the universe).

Also, looking through a telescope is an indirect observation. Especially a non-visible-light telescope.

Quoting Pfhorrest

Also, looking through a telescope is an indirect observation. Especially a non-visible-light telescope.

Data collected from radio-telescopes of distant stellar objects is direct - you're seeing the light waves or radio waves emitted by the object. It's no less direct than looking at anything. But if you see the effects of something about which you have no concept, that's inferential - you're inferring that some unknown substance - dark matter, say - is exerting gravitational pull on galaxies.

And 'we' don't know it's real at all. There are astronomers who believe that physics is inaccurate or problematical at those scales, for example. Other physicists say they're wrong, but nobody has direct empirical evidence of the existence of dark matter. As of now, it's metaphysics.

Reply to Wayfarer We can’t see radio waves. We can build machines that interact with those radio waves and do things in response that we can see, and so infer what kind of radio waves are coming from where indirectly that way.

We can’t see wind, but we can see leaves moving and infer the existence of wind from that. (Disregarding other senses for this example).

We can’t see asteroids in the asteroid belt, or single-celled organisms, but we can build arrangements of lenses and mirrors that project images of them that we can see.

I’m surprised you didn’t comment on this in my thread Against Transcendentalism as it’s a pretty important part of establishing a what “natural” means. Without it, germs are as “metaphysical” as you say dark matter is.

Quoting Pfhorrest

I’m surprised you didn’t comment on this in my thread Against Transcendentalism as it’s a pretty important part of establishing a what “natural” means. Without it, germs are as “metaphysical” as you say dark matter is.

Mistaken. In the case of radio waves, wind, and germs, we have a precise physical description of these, even if they're not visible to the naked eye. They're certainly visible to the eye augmented by radio telescopes, wind-socks and microscopes, respectively. But these aren't indirect means of detection; we can see and measure the phenomenon that is the cause of the observed effect.

Whereas there is no theory of what dark matter is at all. Something not being detectable by unaided vision doesn't make it metaphysical. What makes dark matter a metaphysical conjecture, is precisely that it is beyond - "meta" - known physics. Likewise, questions about whether there are parallel universes or the multiverses predicted by string theory.

I'm surprised by your apparent naivety in this matter ;-)

Quoting Wayfarer

we have a precise physical description of these

There is a difference between not having a complete explanation of a pheonomenon, and that phenomenon being "metaphysical" or somehow not physical. And that has nothing to do with direct vs indirect detection. Radio waves, wind, germs, etc, are things that we have done enough indirect observation of and enough theorizing about to come up with thorough explanations of them in the same terms as the things we have direct observation of.

But, for example, we had such detection of radio waves long before we had physical theories that framed them as the same kind of thing as light. Dark matter is currently in that stage: we have observed that it is, even though we don't yet have a complete theoretical explanation of what it is. We can "see" dark matter in exactly the same way you can "see" a transparent glass orb: by the distortion of light from behind it, via gravitational lensing in the case of dark matter. We know for sure that there is a certain amount of mass in a certain place and that it doesn't interact strongly with certain forces, and we don't yet know a lot more about what is there, but we know for sure that there is something there.

You have this weird thing where you don't differentiate between things that we don't currently have a full explanation of and things that are beyond explanation, like when you conflate the paranormal with the supernatural. Supernatural things have no physical effects to be observed at all. Paranormal things supposedly do, but the occurrence of the claimed phenomena has not yet been confirmed. Something like dark matter is a step further still away from that: we know that a phenomenon is for sure occurring, we just can't completely explain it yet. And then there are the familiar well-known topics that we can explain. But lack of an explanation doesn't mean it's unexplainable, just that it's unexplained. Being physical isn't the same thing as being fully explained by current theories of physics, it's just being the kind of thing that we can learn about through the methods of physics.

Quoting Pfhorrest

Dark matter is currently in that stage: we have observed that it is, even though we don't yet have a complete theoretical explanation of what it is.

Science has no idea what 'it' is, or even if 'it' exists, and it's never observed any such thing. That would be a huge headline! Dark matter is used to explain why the motion of galaxies varies from what is predicted. But it's possible there's something wrong with the prediction - that's what Mordehai Milgrom thinks. Not everyone agrees that there must be dark matter. But radio waves, germs, and wind are not a matter of conjecture

Metaphysics, anyway, is not 'beyond explanation'. Strictly speaking it concerns 'first philosophy', what the nature of reality must be to account for the experiences we have and the observations we make; what is beyond observation but suggested by it. And in this case it concerns a conjecture which currently has no physical basis, but which is suggested by observation, which is completely in keeping with both the meaning of the term and the reality of the situation.

Quoting Pfhorrest

Supernatural things have no physical effects to be observed at all. Paranormal things supposedly do, but the occurrence of the claimed phenomena has not yet been confirmed.

You don't know this, it's a supposition. There's a lot of controversy in the field of PSI, but there's also a lot of goalpost shifting and arguments about statistical significance and the like. Our notion of reality has exceedingly porous boundaries.

Quoting Wayfarer

Science has no idea what 'it' is, or even if 'it' exists, and it's never observed any such thing. That would be a huge headline!

You're behind the times. MOND is dead. There was a huge headline, about the Bullet Cluster observation. We looked at two galaxies that had collided, both the direct starlight and the gravitational lensing. The luminous matter clumped as expected normally, but the gravitational lensing showed that significant mass of the galaxies had passed right through them exactly as expected by a WIMP model, and in a way unexplainable by MOND.

Prior to that you'd have been right, we weren't sure if there was some stuff there or just if our model of gravity was wrong. Now we know there's definitely some kind of stuff there, we just don't know much about it yet.

Quoting Wayfarer

Metaphysics, anyway, is not 'beyond explanation'. Strictly speaking it concerns 'first philosophy',

That's not the way you seemed to be using it. You seemed to be using it to mean "supernatural", outside the domain of physics. Empirical phenomena that just don't yet have an explanation in terms of other better-known phenomena are not "metaphysical", they're just as-yet-unexplained.

Quoting Wayfarer

You don't know this, it's a supposition.

It's definitional. If something is supposed to have empirical, physical effects, then it's a supposed natural phenomenon, not supernatural. If the supposed phenomenon were conclusively confirmed to occur, even if it lacked an explanation, it would just be normal science (not in the Kuhnian sense, just) not paranormal.

Quoting Wayfarer

There's a lot of controversy in the field of PSI, but there's also a lot of goalpost shifting and arguments about statistical significance and the like.

If there's some evidence for something, but not undeniable evidence, leaving room for doubt about whether the phenomenon actually occurs, then it's not "confirmed" yet. That doesn't mean it's definitely not happening, it just means there is as yet conclusive consensus that it's definitely happening.

Reply to Wayfarer Reply to Pfhorrest

What the hell are "direkt observations" anyways? It's not like the photons hitting your retina are a cat, a rock etc. Neither are the vibrations carried to your eardrums a guitar.

Quoting Wayfarer

Dark matter is used to explain why the motion of galaxies varies from what is predicted. But it's possible there's something wrong with the prediction

It's possible there's something wrong with any prediction. It's possible cats are entirely an illusion. The only difference is the likelihood of it being the case.

Quoting Pfhorrest

Now we know there's definitely some kind of stuff there, we just don't know much about it yet.

I just can't help being reminded of epicycles and crystal spheres.

Quoting Pfhorrest

It's definitional. If something is supposed to have empirical, physical effects, then it's a supposed natural phenomenon, not supernatural.

The placebo effect doesn't have a naturalistic explanation, or at least a physical explanation.

Just remember the meaning of 'phenomenon' - it's 'what appears'. And empiricism is always going to seek for explanations on the level of 'what appears', or extrapolations from 'what appears' on the basis of mathematical extrapolation. Empiricism excludes some kinds of explanatory models purely as a matter of principle, but then forgets that it's done so.

Quoting Echarmion

What the hell are "direkt observations" anyways? It's not like the photons hitting your retina are a cat, a rock etc. Neither are the vibrations carried to your eardrums a guitar.

You're confusing two kinds of explanation here. Of course one can question the nature of observation itself - that is the task of philosophical analysis. But when it comes to dark matter, it's proposing a natural explanation which consists of some kind of 'matter' the likes of which is completely unknown, to explain observational anomalies in cosmology.

The key point, and where you entered the argument, is that nothing corresponding to dark matter has been directly observed, despite large and elaborate experimental apparatus having been set up for that purpose. We might agree or disagree on what it means, but the absence of direct observation is not a matter of opinion.

Quoting Echarmion

What the hell are "direkt observations" anyways? It's not like the photons hitting your retina are a cat, a rock etc. Neither are the vibrations carried to your eardrums a guitar.

Yeah, and that's kind of my point. Indirect observations aren't really fundamentally different from direct ones. Everything is to some degree indirect, it's just a question of how much. All we directly see is patterns of light (if we can even take for granted that we actually have eyes attached to actual optical nerves attached to our brains... in an even more skeptical sense all we see is impressions of color in our minds, that we indirectly infer arise due to the impingement of colored light on the eyes we seem to have). The existence of permanent objects in three-dimensional space is indirectly inferred from those patterns of light. The specifics of what objects there are where and what they do is indirectly inferred by the behavior of other objects.

Quoting Wayfarer

The placebo effect doesn't have a naturalistic explanation, or at least a physical explanation.

We know that the brain controls many aspects of the body, and that mental states correlate to brain states. It's not at all spooky or paranormal or supernatural that someone's mental states would affect things about their body. We don't know the specific details involved, but that's a far cry from "naturalism and physicalism can't account for this!"

Quoting Wayfarer

Just remember the meaning of 'phenomenon' - it's 'what appears'. And empiricism is always going to seek for explanations on the level of 'what appears', or extrapolations from 'what appears' on the basis of mathematical extrapolation. Empiricism excludes some kinds of explanatory models purely as a matter of principle, but then forgets that it's done so.

What would a supernatural explanation even look like? A natural explanation is an account of one kind of phenomenon in terms of another kind of phenomenon: when you see this kind of thing happen you should expect to also see this kind of thing happening. But supernatural things aren't phenomena by definition; they're non-empirical. So "when you see this kind of thing happening you should expect to, er... well you can't see this other kind of thing at all, but it's why that kind of thing is happening, I swear".

Things that have no experiential impact whatsoever to anyone ever are of no consequence to anyone ever, and are rightly disregarded as literal nonsense. Things that do have experiential impact are by definition empirical, natural, physical things.

@StreetlightX This conversation seems to have veered way off the original topic, any chance you can do another thread split for us?

Quoting Wayfarer

You're confusing two kinds of explanation here. Of course one can question the nature of observation itself - that is the task of philosophical analysis.

No. If I were questioning the nature of observation itself, I'd be asking whether and how what's in your mind is actually related to anything outside of it.

What I am saying is that, according to physics, everything we observe is indirect, an effect. If I "look" at a rock, all I am perceiving is the effect that photons reflected from the rock have on my retina, nerves and brain. How is that a "direct" observation of the rock?

Quoting Wayfarer

But when it comes to dark matter, it's proposing a natural explanation which consists of some kind of 'matter' the likes of which is completely unknown, to explain observational anomalies in cosmology.

That sentence doesn't make any sense to me. What does "the kind of which is completely unknown" mean? You could say the same of "normal matter" or "antimatter".

Quoting Wayfarer

The key point, and where you entered the argument, is that nothing corresponding to dark matter has been directly observed, despite large and elaborate experimental apparatus having been set up for that purpose.

What do you mean by "corresponding to"? Why would something have to correspond to something else?

Quoting Wayfarer

We might agree or disagree on what it means, but the absence of direct observation is not a matter of opinion.

It's even less than an opinion if you can't explain what "direct observation" even is.

Quoting Pfhorrest

This conversation seems to have veered way off the original topic, any chance you can do another thread split for us?

We're only two pages in and the OP this thread was zombiefied from 6 months ago, so I think it's fine to simply let conversation continue as is here.

Quoting Pfhorrest

Everything is to some degree indirect, it's just a question of how much.

Yes, there's the question of 'the nature of perception and observation' but that is not what is at issue in the discussion of dark matter.

Quoting Pfhorrest

The existence of permanent objects in three-dimensional space is indirectly inferred from those patterns of light.

That sounds more like Kant than scientific realism. Again, I don't think it's mistaken but I also don't think it's relevant to the point at issue.

Quoting Pfhorrest

We know that the brain controls many aspects of the body, and that mental states correlate to brain states

The latter is certainly not known at all. That is simply brain-mind identity theory, but as you say, that is totally off topic here. Let's simply observe the physicalist assumptions that underlie this confidence.

Quoting Pfhorrest

What would a supernatural explanation even look like?

There are many subject areas that are out of the scope of naturalism. Of course, 'supernatural' is a loaded word, but then I didn't introduce it. I said that questions like the existence of dark matter/energy are in a sense metaphysical questions - something that is suggested by observation, but is now and possibly forever beyond the scope of observation.

Quoting Echarmion

What I am saying is that, according to physics, everything we observe is indirect, an effect.

I don't know a lot of physics, I studied it formally up to high school level, and I've read quite a few books on physics, but that was never stated as part of physics. It might have been stated because of 'philosophical reflections on the nature of physics' but it's not something taught in physics per se.

Quoting Echarmion

It's even less than an opinion if you can't explain what "direct observation" even is.

Direct observation = observing directly. Observing that movement of masses of air causes trees to bend, that germs cause disease, that radio waves can be detected with the appropriate instruments. Abductive inference = reasoning from effect to cause i.e. 'because this happened, then the cause must be X'. But in this case, 'X' stands for something that not only hasn't been observed, but may possibly never be observable in principle.

Quoting Wayfarer

I don't know a lot of physics, I studied it formally up to high school level, and I've read quite a few books on physics, but that was never stated as part of physics. It might have been stated because of 'philosophical reflections on the nature of physics' but it's not something taught in physics per se.

Obviously anything referencing the terms "direct" or "indirect observation" is philosophy and not physics. My point is that your distinction between direct and indirect has no basis in physics as we currently understand it.

Quoting Wayfarer

Direct observation = observing directly.

is this supposed to be a joke?

Quoting Wayfarer

Observing that movement of masses of air causes trees to bend, that germs cause disease, that radio waves can be detected with the appropriate instruments. Abductive inference = reasoning from effect to cause i.e. 'because this happened, then the cause must be X'. But in this case, 'X' stands for something that not only hasn't been observed, but may possibly never be observable in principle.

How is "germs cause disease" not an abductive inference? You even reference instruments. "The instrument beeps, therefore it has detected a radiowave" is very clearly reasoning from effect to cause.

Quoting Echarmion

is this supposed to be a joke?

Ask a stupid question.....

Quoting Echarmion

How is "germs cause disease" not an abductive inference? You even reference instruments. "The instrument beeps, therefore it has detected a radiowave" is very clearly reasoning from effect to cause.

:clap: :up:

I'll let you take things from here, you've clearly got this and I'm tired of this shit.

Yeah Wayfarer has, uh, issues understanding what 'observation' entails in scientific contexts. As long as it relates to science you can be sure he will lie and obscuate in order to peddle whatever supernatural trash he's into.

Reply to StreetlightX Reply to Pfhorrest Reply to Echarmion In the paradigm cases that have been brought up - radio waves, wind, and germs - there is a clear correlation in theory and observation between cause and effect. The cause of the associated phenomena is understood clearly and can be explained directly. I don't think the statements that germs cause disease, that masses of moving air constitute wind, and that radio waves are an invisible form of radiation that exists on the electromagnetic spectrum, are metaphysical statements. But the statement that 'some unknown form of matter causes the discrepancy that is observed in the motion of galaxies' clearly is a metaphysical statement, because it posits the existence of some form of matter that can't even be detected by current physics, hence is beyond or above, 'meta', current physics.

Happy to be corrected, but other than stupid questions and hostile invective, nothing has been close.

Except it can be observed. See the Bullet Cluster again.

All working physicists informally appeal to "directness" whenever they make an inference, even though Physics possess no theory of directness. For otherwise a physicist could not claim to learn anything from an experiment, nor for that matter could he find the sentences of physics intelligible. So although directness/indirectness aren't themselves defined in terms of physical criteria, the converse is true.

Exactly the same issue applies to language in general, for we are taught the meaning of words either through ostensive definition, or by verbal definitions that implicitly appeal to earlier ostensive definitions for their intelligibility. And yet we have no linguistic criteria for translating verbal definitions into ostensive definitions and vice-versa, for languages are only publicly defined up until verbal criteria.
.
In line with language in general, the semantics of Physics is both under-determined and redundant; one Physicist's "natural" object is another Physicist's "metaphysical garbage", because they might each understand physics using different semantic foundations that are rooted in different ostensive definitions.

Quoting Pfhorrest

Except it can be observed.

The purported EFFECTS can be observed. But dark matter itself cannot be and hasn’t been observed. This is fact.

Quoting sime

In line with language in general, the semantics of Physics is both under-determined and redundant; one Physicist's "natural" object is another Physicist's "metaphysical garbage", because they might each understand physics using different semantic foundations that are rooted in different ostensive definitions.

:up: And the reason for that is not a matter for physics.

Quoting Wayfarer

The purported EFFECTS can be observed.

This is an oxymoron. All scientific observation is observation of effect.

We discovered that atoms have nuclei because of the effects of particle scattering. But of course only a scientifically illiterate moron would argue that we 'didn't really observe' atomic nuceli in the Geiger-Marsden experiments, for instance. Only the same moron would say that the experiment only proved the 'metaphysical' notion of a nuceli. This same moron would have a surprise in store for him when he realizes how particle accelerators work to observe things too.

Quoting Echarmion

How is "germs cause disease" not an abductive inference?

‘Abductive reasoning (also called abduction,[1] abductive inference,[1] or retroduction[2]) is a form of logical inference which starts with an observation or set of observations and then seeks to find the simplest and most likely explanation for the observations. This process, unlike deductive reasoning, yields a plausible conclusion but does not positively verify it.’

I believe the germ theory of disease has been verified. You don’t?

Reply to StreetlightX The ontology of the probability wave and so also the atom is still one of the outstanding problems of physics, and the particle accelerator has still not resolved that issue, philosophically, Although I realise philosophy may not be of particular interest to you.

Reply to Wayfarer Except the experiments I mentioned have nothing to do with any of that so maybe come back when you're done parading your utter, shameless ignorance of science about.

Reply to StreetlightX This is a ‘philosophy forum’. I think it’s interesting that all of this grew out of my suggestion that the nature and existence of dark matter might be a metaphysical question. Look at the reaction. It’s a sane and sober point. If ‘dark matter’ is real, it means that either our notion of what constitutes ‘matter’ is radically insufficient’, or alternatively, that our understanding of current physics is. How is this *not* a metaphysical issue?

Reply to Wayfarer Nope, not getting distracted by your usual attempts to change the subject. You have a terrible, horrible, no good, very bad understanding of scientific observation. That's all I came to say. It doesn't help that you regularly peddle pseduo-scientifc sake oil.

Quoting Wayfarer

In the paradigm cases that have been brought up - radio waves, wind, and germs - there is a clear correlation in theory and observation between cause and effect.

Cause and effect is itself a theory based on correlation, so I'm not sure what this sentence means.

Quoting Wayfarer

The cause of the associated phenomena is understood clearly and can be explained directly.

Really? Can we understand clearly the nature of wave function that ultimately "causes" all the examples you named? Can we directly explain gravity? The clear and direct explanations you posit are based on popular simplifications. In fact, the nature of "normal" matter is hardly less mysterious than that of dark matter.

Quoting Wayfarer

But the statement that 'some unknown form of matter causes the discrepancy that is observed in the motion of galaxies' clearly is a metaphysical statement, because it posits the existence of some form of matter that can't even be detected by current physics, hence is beyond or above, 'meta', current physics.

But it isn't unknown. We know a whole lot of it's properties.

Quoting Wayfarer

‘Abductive reasoning (also called abduction,[1] abductive inference,[1] or retroduction[2]) is a form of logical inference which starts with an observation or set of observations and then seeks to find the simplest and most likely explanation for the observations. This process, unlike deductive reasoning, yields a plausible conclusion but does not positively verify it.’

I believe the germ theory of disease has been verified. You don’t?

This reads like you're saying that, once a theory arrived at via abductive reasoning is verified, the abduction part it's based on vanishes. That seems nonsensical.

Quoting Wayfarer

If ‘dark matter’ is real, it means that either our notion of what constitutes ‘matter’ is radically insufficient’, or alternatively, that our understanding of current physics is. How is this *not* a metaphysical issue?

Both of these options seem evidently within physics. There's nothing "meta" about them.

Quoting sime

All working physicists informally appeal to "directness" whenever they make an inference, even though Physics possess no theory of directness. For otherwise a physicist could not claim to learn anything from an experiment, nor for that matter could he find the sentences of physics intelligible.

How does any of this follow?

Reply to StreetlightX Your concern is touching, but I get by.

Quoting Echarmion

In fact, the nature of "normal" matter is hardly less mysterious than that of dark matter.

I rest my case.

Reply to Wayfarer I just like helping the disabled, physically or otherwise.

[deleted]

Quoting Wayfarer

The purported EFFECTS can be observed. But dark matter itself cannot be and hasn’t been observed. This is fact.

Do you think black holes have never been observed too? Because we've observed them with the exact same methods as we've observed dark matter.



Anyway, how did we get stuck on this topic of dark matter, when the only thing even vaguely relevant to the OP is dark energy (as a possible source of continuous energy to combat the heat death of the universe, and an explanation for how that heat death hasn't already happened). And dark matter and dark energy, besides having "dark" in the name, have nothing to do with each other.

This user has been deleted and all their posts removed.

Reply to god must be atheist Reply to tim wood Excellent point, Tim; and that should be an end to it. But doubtless these appallingly bad physics and maths threads will continue.

They are an embarrassment, really. Any curious scientist who passes by the forums would quickly and quietly move on.

Quoting Banno

doubtless these appallingly bad physics and maths threads will continue.

The comment that provoked the firestorm was that dark matter is a metaphysical conjecture. Terrible thing to say.

Quoting Pfhorrest

The principle of causal closure is about what counts as physical. Anything that has a physical effect counts as a physical thing. We observe physical effects (galaxies rotating faster than we would otherwise expect should be possible without flying apart, and galaxies accelerating away from each other faster that we would otherwise expect), and we don't yet know what is causing them, so we give whatever those things are placeholder names, "dark matter" and "dark energy". But since they have physical effects, whatever those things turn out to be count as physical things.

Which is the subject of Hempel’s dilemma.

Quoting Pfhorrest

Anyway, how did we get stuck on this topic of dark matter...?

From this remark:

Quoting Echarmion

Current physics do describe "dark matter" and "dark energy". These names describe physical phenomena that have been observed.

That's what the subsequent debate was about, culminating in me being repeatedly called a 'moron' by one of the Forum Moderators who has a history of abusive posts towards me. Anyway, I maintain that dark matter has not been observed, and from everything I've read about it, this is a fact.

I'm logging out for several weeks - I need to say this, otherwise I just tend to gravitate back here by force of habit, and I have some projects that need single-minded attention. So long for now.

Wayfarer.
Re-read my comment. There are no 'events' and there is no 'physicality' except with respect to the evolving perceptual needs of humans who consensually segment and re-segment what they call 'the world'. Ultimately all definition becomes subject to an infinite regress in which axioms like 'entropy' have ephemeral utility. Such is the basis of pragmatism versus naive realism.

Quoting Echarmion

The entire infinite space with infinite matter, the whole system is a closed system.
— god must be atheist

Well we don't really know that, do we?

Yes, there is a lot of assumptions thrown behind that claim of mine, among others, that there are no supernatural powers. Another assumption is that there are even more supernatural powers. And there are more assumptions, like there are even more supernatural powers than that.

However, if the laws of physics are different beyond a certain region, it still is a closed system. It would only be an open system if it received or lost some energy to the outside of the system, but since it encompasses the entire space, there is no "outside" room to lose to or to gain from any energy.

00000000000

Of course my claim assumes that energy can't be created or destroyed in ANY part of the universe. This is an invalid assumption in a philosophical sense, but not invalid in a physics sense. Physics never claimed this tenet (the indestructibility of energy) to be a universal truth. But it assumes it is true until disproved. This assumption we can carry over to any region of space, including the entire expanse of space.

"All bets are off" does not exclude assumptions. It excludes knowledge. Assumptions are not knowledge; they are presuppositions. In this sense, we can't know (and this is compatible with current knowledge of physics) whether energy is indestructible in our observed space. We assume it is.

So we don't know if the second law of thermodynamics applies to our observed world.
We don't know if the second law of thermodynamics applies to beyond our observed world.
We assume that the second law of thermodynamics applies to our observed world.
We assume that the second law of thermodynamics applies to beyond our observed world.

The only difference between the two sets of assumptions is the word "beyond". Since everything else is the same, we can conclude that the world beyond our observed world can be assumed to behave like our world. (A different assumption is just as valid to the world beyond our observed one. But the assumption I advocate is not invalid. That's my point.)

Quoting Banno

They are an embarrassment, really. Any curious scientist who passes by the forums would quickly and quietly move on.

As you are an embarrassment to logical thinking, @Banno. Your style and behaviour pattern has chased away at least one really smart and useful contributor, and I daresay he may not have been the only one.

I admit you are not the only one to blame for the quitting of the ex-member, but you display the flagship behaviour that made the smart contributor quit consistently and over and over again.

Your contributions, @Banno, are distasteful, meaningless and never backed up by reasoning. You seem to appeal to a select group of other users, and together you form a clique.

Unfortunately for you and your forum friends, logic and reason is not established on consensus. They are established on their own terms. This is your downfall: your bs and your negative judgement do not go beyond approval by your so-called friends in this forum. And perhaps beyond those users, who by default value style over content.

This user has been deleted and all their posts removed.

This user has been deleted and all their posts removed.

Entropy is a concept that is useful on a microscopic scale, but has trouble applying itself to the macroscopic one. As such, there is no such thing as "the entropy of the world, or of the universe", or even heat death of the universe owing to entropy. Entropy is even problematic in the microcosm, as studies show.

Quoting Pussycat

Entropy is a concept that is useful on a microscopic scale, but has trouble applying itself to the macroscopic one. As such, there is no such thing as "the entropy of the world, or of the universe", or even heat death of the universe owing to entropy. Entropy is even problematic in the microcosm, as studies show.

Dear Pussycat, entropy is not present in the quantum level of existence (if that's what you mean by microscopic scale), but it is very much present in the macrophysical scale. This is very elementary physics. If you like to check for validity, please check Wiki, or the nearest high school's physics textbooks.

Reply to god must be atheist From wikipedia:

https://en.wikipedia.org/wiki/Heat_death_of_the_universe#Controversies

Max Planck wrote that the phrase "entropy of the universe" has no meaning because it admits of no accurate definition. More recently, Walter Grandy writes: "It is rather presumptuous to speak of the entropy of a universe about which we still understand so little, and we wonder how one might define thermodynamic entropy for a universe and its major constituents that have never been in equilibrium in their entire existence." According to Tisza: "If an isolated system is not in equilibrium, we cannot associate an entropy with it." Buchdahl writes of "the entirely unjustifiable assumption that the universe can be treated as a closed thermodynamic system". According to Gallavotti: "... there is no universally accepted notion of entropy for systems out of equilibrium, even when in a stationary state." Discussing the question of entropy for non-equilibrium states in general, Lieb and Yngvason express their opinion as follows: "Despite the fact that most physicists believe in such a nonequilibrium entropy, it has so far proved impossible to define it in a clearly satisfactory way." In Landsberg's opinion: "The third misconception is that thermodynamics, and in particular, the concept of entropy, can without further enquiry be applied to the whole universe. ... These questions have a certain fascination, but the answers are speculations, and lie beyond the scope of this book."

A recent analysis of entropy states, "The entropy of a general gravitational field is still not known", and, "gravitational entropy is difficult to quantify". The analysis considers several possible assumptions that would be needed for estimates and suggests that the observable universe has more entropy than previously thought. This is because the analysis concludes that supermassive black holes are the largest contributor. Lee Smolin goes further: "It has long been known that gravity is important for keeping the universe out of thermal equilibrium. Gravitationally bound systems have negative specific heat—that is, the velocities of their components increase when energy is removed. ... Such a system does not evolve toward a homogeneous equilibrium state. Instead it becomes increasingly structured and heterogeneous as it fragments into subsystems."

Also:

https://en.wikipedia.org/wiki/Non-equilibrium_thermodynamics

Another fundamental and very important difference is the difficulty or impossibility, in general, in defining entropy at an instant of time in macroscopic terms for systems not in thermodynamic equilibrium; it can be done, to useful approximation, only in carefully chosen special cases, namely those that are throughout in local thermodynamic equilibrium.

So, entropy cannot be defined for:

a) systems that are not in this thing called "thermodynamic equilibrium", the vast majority of systems in nature are like that.
b) the universe as a whole.

Quoting Pussycat

Max Planck wrote that the phrase "entropy of the universe" has no meaning because it admits of no accurate definition. More recently, Walter Grandy writes: "It is rather presumptuous to speak of the entropy of a universe about which we still understand so little, and we wonder how one might define thermodynamic entropy for a universe and its major constituents that have never been in equilibrium in their entire existence1This is an assumption they can't substantiate.." According to Tisza: "If an isolated system is not in equilibrium, we cannot associate an entropy with it."2. Assumes the entire universe is not an isolated system. Buchdahl writes of "the entirely unjustifiable assumption that the universe can be treated as a closed thermodynamic system". According to Gallavotti: "... there is no universally accepted notion of entropy for systems out of equilibrium, even when in a stationary state." Discussing the question of entropy for non-equilibrium states in general, Lieb and Yngvason express their opinion as follows:"Despite the fact that most physicists believe in such a nonequilibrium entropy, it has so far proved impossible to define it in a clearly satisfactory way."3. READ THE WORDS: DESPITE THAT FACT THAT MOST PHYSICISTS BELEIVE IN SUCH A NON-EQUILIBRIUM THEORY In Landsberg's opinion: "The third misconception is that thermodynamics, and in particular, the concept of entropy, can without further enquiry be applied to the whole universe. ... These questions have a certain fascination, but the answers are speculations, and lie beyond the scope of this book."4. MY OPINION IS NOT, REPEAT, NOT LANDSBERG'S BOOK.
A recent analysis of entropy states, "The entropy of a general gravitational field is still not known", and, "gravitational entropy is difficult to quantify". 5. i AM NOT TALKING GRAVITATIONAL ENTROPY. The analysis considers several possible assumptions that would be needed for estimates and suggests that the observable universe has more entropy than previously thought. This is because the analysis concludes that supermassive black holes are the largest contributor. Lee Smolin goes further: "It has long been known that gravity is important for keeping the universe out of thermal equilibrium. Gravitationally bound systems have negative specific heat—that is, the velocities of their components increase when energy is removed. ... Such a system does not evolve toward a homogeneous equilibrium state. Instead it becomes increasingly structured and heterogeneous as it fragments into subsystems."6 THIS HAS PATENTLY NOTHING TO DO WITH THE POINT.

I love it when a dilettante searches the Internet to disprove a point. They come up with pearls of wisdom that they can't fathom, and they actually help disprove their criticism with their quotes.

Thank you, Pussycat. Prrrr.Quoting Pussycat

Another fundamental and very important difference is the difficulty or impossibility, in general, in defining entropy at an instant of time in macroscopic terms for systems not in thermodynamic equilibrium; it can be done, to useful approximation, only in carefully chosen special cases, namely those that are throughout in local thermodynamic equilibrium.7 READ: AT AN INSTANT OF TIME. OUTSIDE OF AN INSTANT OF TIME IT IS NOT DIFFICULT, IT IS NOT IMPOSSIBLE.

Again: the dilettante does not know how to read carefully, because it's above his or her head. So to speak. But they have a very strong opinion, and they will stick by it tooth and nail.

And claws. Prrr.

Reply to god must be atheist I don't need to do much searching, as I studied physics. And sorry man, I don't have time for guys like you, I used to have, but now it seems that I have run out of time. So believe what you like, no one cares anyway, it makes no difference.

Reply to Pussycat , the search you have done proved you wrong in parts, and did not prove you right in other parts. If you studied physics, you should demand a refund of your tuition fees.

I am not battling with you, I'm battling with your ideas. The quotes you supplied prove beyond any reasonable doubt that you not only don't know physics, but don't know how to read text, either.

I am sorry. I really did not enjoy this either. Most likely even less than you have. I just refuse to give in to nonsubstantial, ill-gotten, unreasonable arguments. I wish I was doing something else instead, too, man, please don't feel it was only bad for you.

Reply to Pussycat thanks for the summary. All I remember from high school was doing tests in chemistry that reduced local entropy at the cost of a shit load of energy.

Quoting tim wood

My contribution here is to refer to "Poincare recurrence." Easy enough to google. Very broad strokes: the idea is that in any system, wait long enough and some configuration of it will recur

Too broad, IMO. This is a result that requires a function that takes points in the space under consideration back into that space. However, with regard to a measure defined on the space, the function must preserve that measure. This is quite restrictive. If I examine systems in the complex plane, using the normal Euclidean measure, the function seems to be a simple linear translation. Extremely restrictive.

This user has been deleted and all their posts removed.

Reply to god must be atheist "Battling with my ideas" is your inline comments numbered 1-7, which is perfectly allright.

But I fail to see how the rest of your comments is "battling with my ideas" and not "battling with me": "I love it when a dilettante searches the Internet to disprove a point. They come up with pearls of wisdom that they can't fathom, and they actually help disprove their criticism with their quotes", "Again: the dilettante does not know how to read carefully, because it's above his or her head. So to speak. But they have a very strong opinion, and they will stick by it tooth and nail".

dante, dante, diledante

dilettante kse-dilettante, I won't trouble myself with such bad attitudes ever again, I had my share. I'm done. After all, there are other fish in the sea, other fish to fry. :naughty:

Quoting tim wood

My understanding was akin to shuffling a deck of cards a lot of times.

Yes, I'm not sure what further if any conditions would be placed on that experiment. Combinatoric calculations in probability. Here is a comment from Geology Wiki:

"The Poincaré recurrence time of certain systems is the time for them to revert to a state almost identical to their current state. The system should satisfy the following properties:

1. All the particles in the system are bound to a finite volume.
2. The system has a finite number of possible states.

The universe might not satisfy these properties."

Mathematical theory of PR is pretty strict. :cool:

This user has been deleted and all their posts removed.

Assuming equal probability, the finite number of states simply means that the fewer the states the higher probability one re-occurs over a lengthy series of experiments. And as the number of states increases without bound ("goes to infinity"), the probability of a particular state shrinks toward zero. Roughly speaking.

The function has to do with the mixing of the particles, say, from moment to moment. Without preservation of "area" the distance between two points might shrink each iteration, and the configuration one would like to see re-emerge would not be possible. Roughly speaking.

Quoting god must be atheist

If matter has existed from infinite past, then entropy is such that it can be reset to a previous state.

If this was not true, the world would be approaching much closer to a fully entropic state than what we experience right now. Or else perhaps we'd be in a fully entropic state.

Entropy is a spectrum ofcourse. To say which stage of entropy we should be in right now would be hard for any scientist to claim considering the tremendous amount of unknown variables that modern science has to figure out. The user Devans99 would agree with you on this and I would have to say you are very much right in the first part of this OP.

The conversation has drifted into ergodic theory rather than entropy. :roll:

Reply to jgill They are closely related topics.

Reply to Benkei You're welcome, although what I posted had to do with entropy in its broadest sense, and not as it is used in laboratory experiments.

Anyways, a good book on entropy is "Understanding Non-Equilibrium Thermodynamics" by Georgy Lebon, David Jou and Jose Casas-Vazquez.

https://b-ok.cc/book/508021/aad3be

From the preface:

Besides being an introductory text, our objective is to present an overview, as general as possible, of the more recent developments in non-equilibrium thermodynamics, especially beyond the local equilibrium description. This is partially a terra incognita, an unknown land, because basic concepts as temperature, entropy, and the validity of the second law become problematic beyond the local equilibrium hypothesis. The answers provided up to now must be considered as partial and provisional, but are nevertheless worth to be examined.

Right, so non-equilibrium thermodynamics is a terra incognita, a no man's land, well a no woman's land as well, to be politically correct, and not to be accused of sexism.

From chapter 2:

An important question is whether a precise definition can be attached to the notion of entropy when the system is driven far from equilibrium. In equilibrium thermodynamics, entropy is a well-defined function of state only in equilibrium states or during reversible processes. However, thanks to the local equilibrium hypothesis, entropy remains a valuable state function even in non-equilibrium situations. The problem of the definition of entropy and corollary of intensive variables as temperature will be raised as soon as the local equilibrium hypothesis is given up.

By material body (or system) is meant a continuum medium of total mass m and volume V bounded by a surface ?. Consider an arbitrary body, outside equilibrium, whose total entropy at time t is S. The rate of variation of this extensive quantity may be written as the sum of the rate of exchange with the exterior d[sup]e[/sup]S/dt and the rate of internal production, d[sup]i[/sup]S/dt:

dS/dt = d[sup]e[/sup]S/dt + d[sup]i[/sup]S/dt (2.7)

So, the total entropy of the system under consideration is the sum of its internal entropy production, plus the entropy that it exchanges with/due to its surroundings.

Once entropy is defined, it is necessary to formulate the second law, i.e. to specify which kinds of behaviours are admissible in terms of the entropy behaviour. The classical formulation of the second law due to Clausius states that, in isolated systems, the possible processes are those in which the entropy of the final equilibrium state is higher or equal (but not lower) than the entropy of the initial equilibrium state. In the classical theory of irreversible processes, one introduces an even stronger restriction by requiring that the entropy of an isolated system must increase everywhere and at any time, i.e. dS/dt ? 0. In non-isolated systems, the second law will take the more general form

d[sup]i[/sup]S/dt > 0 (for irreversible processes) (2.10a)
d[sup]i[/sup]S/dt = 0 (for reversible processes or at equilibrium) (2.10b)

It is important to realize that inequality (2.10a) does nor prevent that open or closed systems driven out of equilibrium may be characterized by dS/dt < 0; this occurs for processes for which d[sup]e[/sup]S/dt < 0 and larger in absolute value than d[sup]i[/sup]S/dt. Several examples are discussed in Chap. 6.

Therefore, equations 2.10a and 2.10b, which, as the text says, is the 2nd law of thermodynamics in a more general form, refer to the internal entropy of the system: the internal entropy of a system will always increase or remain constant. If the system is isolated, which means that there is no exchange whatsoever with the surroundings, then the term d[sup]e[/sup]S/dt of equation 2.7 is zero and therefore, dS/dt = d[sup]e[/sup]S/dt + d[sup]i[/sup]S/dt = 0 + d[sup]i[/sup]S/dt = d[sup]i[/sup]S/dt >= 0. So, dS/dt = d[sup]i[/sup]S/dt >= 0. This is the form of the 2nd law of thermodynamics for isolated systems: its entropy equals its internal entropy, and remains constant (at equilibrium) or increases with time (when not in equilibrium).

For systems, however, whether open or closed, that are nonetheless driven out of equilibrium, their total entropy may as well decrease with time, the 2nd law has no say in this, if the rate of external entropy exchange d[sup]e[/sup]S/dt is negative and larger in absolute value than the internal entropy production. In other words, the entropy of a non-isolated system can do whatever it pleases, when not in equilibrium.

It is also important to note that all of the above can be said for systems where the local equilibrium hypothesis holds, so what does this hypothesis state? Again from the text:

According to it, the local and instantaneous relations between thermodynamic quantities in a system out of equilibrium are the same as for a uniform system in equilibrium. To be more explicit, consider a system split mentally in a series of cells, which are sufficiently large for microscopic fluctuations to be negligible but sufficiently small so that equilibrium is realized to a good approximation in each individual cell. The size of such cells has been a subject of debate, on which a good analysis can be found in Kreuzer (1981) and Hafskjold and Kjelstrup (1995). The local equilibrium hypothesis states that at a given instant of time, equilibrium is achieved in each individual cell or, using the vocabulary of continuum physics, at each material point.

And then they go on to give a more technical description of the hypothesis, as well a justification for doing so. The local equilibrium hypothesis is therefore a rather good approximation for describing, thermodynamically and in terms of entropy, a system which is out/known to be out of thermodynamic equilibrium, by assuming that at each instant of time the system behaves like it is in fact in equilibrium.

But it just so happens that there are systems where this hypothesis has to be given up, due to the fact that fluctuations from equilibrium are just too great, as well as the time scales where anything takes place are too small for even definining a local entropy per unit time. By giving it up, the 2nd law of thermodynamics becomes highly problematic, up to the point that we are not even able to ascribe a temperature, or say that heat flows from hot to cold anymore, a fundamental tenet of this law. And so physicists have to devise new concepts, and to reformulate this 2nd law in terms of a more general "transport law":

chapter 7:...As a consequence, when working at short timescales or high frequencies, and correspondingly at short length scales or short wavelengths, the generalized transport laws must include memory and non-local effects. The analysis of these generalized transport laws is one of the main topics in modern non-equilibrium thermodynamics, statistical mechanics, and engineering. Such transport laws are generally not compatible with the local equilibrium hypothesis and a more general thermodynamic framework must be looked for.

And all this happens in the laboratory, for well known chemical and biological processes that exhibit such out-of-equilibrium behavior. What is there is to say for the thermodynamics of the universe, where gravitational phenomena kick in, comprising of hypothetical dark matter and dark energy, of which we know absolutely nothing with regards to entropy? I mean, how on earth do you extrapolate ignorance that you have, that you know that you have, on a local level to a global one, to be able to produce certain and definite conclusions, beyond a reasonable doubt, about the fate or the state of the universe?? That's .. that's just mad! Why do that thing? Why put yourself in such a position? Oh, I guess it's just the need to mythologize, like the mythical beings that we are, to tell you the truth, I have the same urge. But I think it's better to be more practical and fight the 2nd law instead, this "law" of decay and decadence, rather to embrace it.