where did the nuggets come from?

[Shiraz (Ray)]

Thanks guys. Sounds like we are all agreed that scale is important and that you really cannot find a consistent link between entropy and order when you consider order at large scales - that was where my original thinking was so fundamentally wrong. Since we are ultimately considering heat, I guess that we need to use the microstates idea (thanks Steven) to describe order at molecular levels (where it can be properly defined) and then, in any isolated system (or system where energy transfers in/out are accounted for), the entropy will never decrease. This applies to the ultimate system, the universe, as well. Happy with this and now understand why this explanation works.

But... is entropy a driver - ie does the universe run because it is trying to get to a state of maximum entropy, or is increasing entropy just an ultimately meaningless construct (which is what Craig was getting at) that does nothing more than tidy up the thermodynamics maths and formalise the idea that change is ultimately irreversible.... or is this even a sensible question? Regards Ray

[CraigS]

Not much wonder finding a gold nugget is so difficult, eh ?

If the aim of a scientific theory is to make predictions to certain degrees of accuracy, then it would seem that breaking components down and quantifying their state of 'measurables', such as entropy, in the case of gold ore formation, seems to not get us very far.

The idea of using entropy as a measure inside a given discrete system, where both reversibility and irreversibility are occurring, would seem to only push the problem onto defining the boundaries of where that system starts and finishes .. (eg in this case: is it within the dominion of the atoms, the nuggets, the ore deposit, the mountain, the region, the continent, the earth, the solar system, the galaxy ….).

Deciding upon which of the measurables within a system has the greatest sensitivity on the overall deposit outcomes, boils down to a bunch of decisions between the random and non-random ones. The number to choose from, could be enormous in a very complex system. When time is considered, the outcome seems to become even less certain.

Quantification of those variables if/when they change over time would seem to call for direct measurement of a given system, as opposed to models based on entropy/thermodynamics. But this approach would only lead to information about a given system, and would not necessarily be able to be extrapolated to another system even having the same critical measurables.

Cheers

[Shiraz (Ray)]

thanks Craig. Will now go and look for a nugget in my garden now that I am sure that the second law of thermodynamics does not say that it cannot be there. Suspect that I may need to raise a thread on probability at some later date. Regards Ray

[CraigS]

Yeah Ray .. let us know if you find one!

What gets me is that the second law only applies to the progress over time of a closed system. If heat is leaving one system, it represents irreversible processes that must have consequences elsewhere. Ok, so if the fundamental laws of physics are time reversible, and yet we've just identified an irreversible process, so something's gotta give. I think this then forces us to look at what the lost heat from our system has done to all adjoining systems.
Also, from the adjoining systems' perspectives, the source of the irreversibility, has to be the processes we have just discarded because of the exclusions implicit in the second law!

Its like a dog chasing its tail, but it all leads to a break-down in the effectiveness of using the 2nd Law as a basis for making predictions.

Cheers

[renormalised (Carl)]

Originally Posted by Shiraz

thanks Craig. Will now go and look for a nugget in my garden now that I am sure that the second law of thermodynamics does not say that it cannot be there. Suspect that I may need to raise a thread on probability at some later date. Regards Ray

Grab a metal detector and then we can open that thread on probability and work out what the probability is of finding that nugget

[adman (Adam)]

Can I float an idea on entropy that I read somewhere that seemed to make sense....

There is no 'requirement' or law that says entropy should always increase (move towards less order). It is simply a statistical near-certainty that it will.

Take an example of mixing two gases. If you mix two gases of different temperatures, their temperatures will equilibrate with the entropy rising to a maximum. In principle, there is nothing to stop the gases from spontaneously separating again and resuming their original temperature and decreasing the entropy - it is just incredibly unlikely. The number of possible states where the gases are evenly mixed vastly outweigh (putting it mildly) the states where they are separated, so, in this system it is simply a matter of probabilities. If you sat and waited long enough - you may be lucky enough to observe a spontaneous decrease in the gases entropy - but I wouldn't hold your breath.

Entropy doesn't have to always increase - it just almost always does.

Another thing I often read is that certain groups of people (you know who...) say that life itself violates the 2nd law of thermodynamics as it represents a decrease in entropy - but you can do work on something to decrease its entropy - you just have to expend energy to do it with any degree of predictability. If a living organism ceases to be able to expend energy (ie: it dies) - the 2nd law takes over pretty quickly. We usually bury them before the increasing entropy starts to cause a smell...

Adam

[CraigS]

G'Day Adam;

Yep .. agree with all that ...

The first law really leads us to the recognition that to get energy conservation, heat must be a form of energy. Heat is a complex thing to track .. it ends up being measured in terms of probability. Thermodynamics is really the study of the likelihood of various outcomes, however they occur, (as you point out). So heat is energy that we more or less give up trying to track (in nitty-gritty detail). The second law (entropy) then is about what we can track, and what we can treat as random.

I need to qualify a comment I made in my last post, also. I kind of insinuated that entropy wasn't a good basis for making predictions .. well, we need a theory to do that. Thermodynamics is structured as scientific 'Laws', so I was probably out of line for expecting it to do so. Still, it sets the priorities for what to look for, in order to make those predictions.

Cheers

[xelasnave]

We start in a dust and gas cloud presumably the remains of a previous system, so at that end of the observation it seems the reverse is true...our complexity came from disorder.
alex

[sjastro]

Originally Posted by adman

Take an example of mixing two gases. If you mix two gases of different temperatures, their temperatures will equilibrate with the entropy rising to a maximum. In principle, there is nothing to stop the gases from spontaneously separating again and resuming their original temperature and decreasing the entropy - it is just incredibly unlikely. The number of possible states where the gases are evenly mixed vastly outweigh (putting it mildly) the states where they are separated, so, in this system it is simply a matter of probabilities. If you sat and waited long enough - you may be lucky enough to observe a spontaneous decrease in the gases entropy - but I wouldn't hold your breath.

Entropy can possibly "decrease" for a closed system when based on a statistical mechanics description at a molecular level.
However separating out two gases, with each gas at it's original temperature, simply can't happen unless external work is applied to the system, which would mean the system was never closed to start with.

Regards

Steven

[CraigS]

Originally Posted by xelasnave

We start in a dust and gas cloud presumably the remains of a previous system, so at that end of the observation it seems the reverse is true...our complexity came from disorder.
alex

G'Day Alex;
The thing is that order can arise from the midst of complexity !
And as you peel back the onion, you can find consecutive layers of order and disorder co-existing but interdependent !
Amazing stuff !

Cheers

[xelasnave]

AND G'Day Craig.....

Is entropy part of wider cycle...mmm that will depend finally on the curvature of space time wont it?..curved either way would suggest different outcomes..anyways I am sure I read that rather than dreamed it up. sorry carry on with what you were doing.
alex

[avandonk]

Ray we have a major source of energy in our local system that drives everything uphill as far as entropy is concerned. It is called the Sun.

All geological processes on Earth are driven by plate tectonics. It has a a sorting effect to separate minerals depending on their density and solubility.

There is nothing mysterious about it.

There is some evidence for bacteria that concentrated gold in the past into nuggets.

Bert

[Shiraz (Ray)]

Hi Bert. Thanks for the interesting insights.
I did not expect that there was any mystery, but my vaguely thought through understanding that the universe was generally heading towards a low order state did not match with what I was seeing - lots of things (minerals, solar system, galaxy) seemed to have developed high order all by themselves. I clearly needed a revised understanding of entropy. regards Ray