1 hour ago, julius2 said:

Ok, entropy is probably about the degree of randomness. Ie. It doesn't necessarily have to increase.

Wherever you feel the urge to use the word 'randomness' in relation to entropy, try replacing it with 'diversity': diversity of position; diversity of momentum; diversity of type; and you will be much closer.

The 'diversity of type' (or 'entropy of mixing') is a much underappreciated aspect as it permits the creation of novel structures due to the low entropy ordering of the structure being offset by its high entropy contribution to diversity.

Hence stars can ultimately produce the heavier elements; which beget life; which begets the broken transistor radios and other miscellaneous items of space junk that continue to populate a cold universe at the end of time.

@MigL can possibly explain how all this structure can be eroded away in the apparent absence of the necessary activation energy - though I can't see it.

2 hours ago, julius2 said:

We are aware of time right now.....

So how can be that it “was never known”?

2 hours ago, julius2 said:

Like I said...."bizarre states"

E.g. all registered entities on the planet will have forgotten that time was existing

What, pray tell, is a registered entity?

You may see entropy from a Chemistry viewpoint @sethoflagos , I see it from a Physics viewpoint ( subtle difference ).
Entropy is a measure of the number of ways, or degrees of freedom, that energy/particles can be arranged in.
Maximal entropy is when all possible states are occupied and there are no further paths to other independent states.
I don't see the relevance of 'structures'.

I believe the Equipartition Theorem is a valid example

12 minutes ago, MigL said:

You may see entropy from a Chemistry viewpoint @sethoflagos , I see it from a Physics viewpoint ( subtle difference ).
Entropy is a measure of the number of ways, or degrees of freedom, that energy/particles can be arranged in.
Maximal entropy is when all possible states are occupied and there are no further paths to other independent states.
I don't see the relevance of 'structures'.

I believe the Equipartition Theorem is a valid example

How would a Physicist view the entropy of this isolated system ?

A small body m1 orbits a larger body m2 but remains under the influence of a third body m3 so the energy varies throughout the orbit of m1.

If the energy of the system has a path to another state ( an independent degree of freedom ) then that 'dilutes' the energy available, and entropy increases.
If there is no path to another state, then the system is in equilibrium at maximum entropy.

The example I previously used was proton decay, as we are not sure it can happen.
If it does decay ( no sooner than 10³⁴ years ), then it provides a path to another state, and proton decay may well provide the 'last' useable energy of the universe, before 'heat death'.

Since the orbit of m1 is continuous, there must be an infinite count of energy states, all different, ie a continuum of energy states.

1 hour ago, MigL said:

You may see entropy from a Chemistry viewpoint @sethoflagos , I see it from a Physics viewpoint ( subtle difference ).
Entropy is a measure of the number of ways, or degrees of freedom, that energy/particles can be arranged in.
Maximal entropy is when all possible states are occupied and there are no further paths to other independent states.
I don't see the relevance of 'structures'.

A 'maximal entropy' planet Earth would have no atmosphere-ocean-crust-mantle-core structure. It would be all mixed up into a homogenous blob (which is roughly how it started out).

Clearly, this was unstable as the denser components had way too much gravitational potential energy for underlying lower density material to support and they sank towards the centre despite the long-term reduction in (ISOTHERMAL) entropy that implied. The 2nd Law wasn't broken:: the large negative dU component of Free Energy was released as more than sufficient entropy increasing heat to offset the entropy reducing TdS drop in thermodynamically available states. But ultimately that heat, and its associated entropy, would be radiated off into space.

Far from evolving into an unstructured body of maximal entropy, it evolves toward a highly structured body of minimal free energy. (Since you're a physicist, I'm using Helmholtz Free Energy here 😉)

Similarly, life uses the surplus free energy of other 1st Law energy sources (sunlight, chemical energy) to convert high entropy water and carbon dioxide into highly structured lower entropy cells and multicellular bodies.

I use the word 'structure' here as a preferred alternative to 'negentropy' or 'complexity', both of which I think are easily misunderstood. But they are effectively synonyms for reservoirs of APPARENTLY negative entropy. I say 'apparently' since the negative residue is more than balanced by a corresponding radiation of heat from the system. Clearly these must be accounted for in any discussion of cosmological entropy budgets.

2 hours ago, MigL said:

The example I previously used was proton decay, as we are not sure it can happen.
If it does decay ( no sooner than 10³⁴ years ), then it provides a path to another state, and proton decay may well provide the 'last' useable energy of the universe, before 'heat death'.

Proton decay with a 10³⁴ year half-life would clearly obliterate all familiar structures within 10³⁵ years. I half suspect that the concept was invented by some physicist who couldn't be bothered to account for cosmological structures in his calculations. Let him demonstrate an unambiguous and spontaneous proton decay, and I might begin to take the possibility seriously. Until then, I shall remain commitedly atheist about it.

2 hours ago, studiot said:

How would a Physicist view the entropy of this isolated system ?

A small body m1 orbits a larger body m2 but remains under the influence of a third body m3 so the energy varies throughout the orbit of m1.

How would the energy vary at all? It’s a conserved quantity. The KE or PE individually would vary, but not the sum.

Thanks Swansont.
Was just about to reply that the energy states @studiot talks about

2 hours ago, studiot said:

Since the orbit of m1 is continuous, there must be an infinite count of energy states

are already occupied, and in equilibrium with gravity ( a conservative force ).
To access any other independent states, or degrees of freedom, you would need to add useable energy.

The same can be said for @sethoflagos planet and atmosphere example.
They are in equilibrium with gravity; where are the other independent states, or degrees of freedom, that are available ?

33 minutes ago, MigL said:

To access any other independent states, or degrees of freedom, you would need to add useable energy.

The same can be said for @sethoflagos planet and atmosphere example.
They are in equilibrium with gravity; where are the other independent states, or degrees of freedom, that are available ?

Yup, currently inaccessible states need a free energy boost to access them. No disagreement here.

Now how about properly addressing my comments on structure? Or am I just wasting my time?

59 minutes ago, sethoflagos said:

Now how about properly addressing my comments on structure?

I didn't think I had to ...

2 hours ago, sethoflagos said:

A 'maximal entropy' planet Earth would have no atmosphere-ocean-crust-mantle-core structure. It would be all mixed up into a homogenous blob (which is roughly how it started out).

Really ?
Is that the lowest energy state ?

2 hours ago, sethoflagos said:

this was unstable as the denser components had way too much gravitational potential energy for underlying lower density material to support and they sank towards the centre

Or is this ???

1 hour ago, sethoflagos said:

Or am I just wasting my time?

Not if we both learn something 🙂 .

7 hours ago, swansont said:

How would the energy vary at all? It’s a conserved quantity. The KE or PE individually would vary, but not the sum.

10 hours ago, studiot said:

How would a Physicist view the entropy of this isolated system ?

That is indeed the definition of an isolated system.

But that energy is distributed between KE and PE (partitioned) as you say so both must continually vary to preserve the sum.

This is exactly where consideration of the system, along with the system boundary, is necessary, as I also pointed out.

1 hour ago, studiot said:

That is indeed the definition of an isolated system.

But that energy is distributed between KE and PE (partitioned) as you say so both must continually vary to preserve the sum.

This is exactly where consideration of the system, along with the system boundary, is necessary, as I also pointed out.

But trading KE and PE is true in a two-body system as well.

8 hours ago, MigL said:

  10 hours ago, sethoflagos said:

A 'maximal entropy' planet Earth would have no atmosphere-ocean-crust-mantle-core structure. It would be all mixed up into a homogenous blob (which is roughly how it started out).

Really ?
Is that the lowest energy state ?

Really. All particles would be free to diffuse to any location within a planet of uniform composition.

And no. The lowest energy state would see the planet in an onion structure of concentric shells of pure components sorted by density. But this doesn't happen either.

(Glossing over issues rnvolving chemical potential: reaction, phase change, etc.)

The direction of planetary evolution is towards a state of lowest free energy, which is a hybrid of these two forces (H = U - TS) The U component drives differentiation of the planetary interior into shells of differing densities; the S component ensures that some degree of mixing always remains, especially among components of similar density.

9 hours ago, MigL said:

Not if we both learn something 🙂 .

Well, you've obliged me to think through in detail something that I'd only a vague hand-wavy picture of before, so thanks for that.

2 hours ago, swansont said:

But trading KE and PE is true in a two-body system as well.

...where TdS again characterises the minimum heat shed by the system due to tidal forces as the two bodies exchange angular momentum on their journey to becoming a fully tidally locked single structure.

Wouldn't this now become effectively a single isolated body?