sun's entropy

When someone claims "life reduces entropy", the
usual retort is that the energy derives from the
sun (photosynthesis), and the sun is pouring energy
into space at a massive rate, with concomitant
increase in entropy.

My question is: how does one compute this solar
rate of entropy increase? Boltzmann's k log W
formula doesn't seem to apply -

--
Rich

Dear RichD:

On Nov 30, 6:59 pm, RichD wrote:
When someone claims "life reduces entropy", the
usual retort is that the energy derives from the
sun (photosynthesis), and the sun is pouring
energy into space at a massive rate, with
concomitant increase in entropy.

Life does not reduce entropy. Life increases entropy for its
environment. Particularly animal life.

My question is: how does one compute this solar
rate of entropy increase? Boltzmann's k log W
formula doesn't seem to apply -

David A. Smith

On Fri, 30 Nov 2007 17:59:58 -0800 (PST), RichD wrote:

When someone claims "life reduces entropy", the
usual retort is that the energy derives from the
sun (photosynthesis), and the sun is pouring energy
into space at a massive rate, with concomitant
increase in entropy.

My question is: how does one compute this solar
rate of entropy increase? Boltzmann's k log W
formula doesn't seem to apply -

That explanation is not quite correct. The reason living organisms can
decrease their own internal entropy is that when they use energy (which
usually comes from the sun, possibly indirectly), they create heat, which
increases the entropy of their environment. This heat is eventually
radiated away into space, of course. Boltzmann's k log W does apply; when
there are more photons flying around, there are more ways they could be
distributed.

--
Jim E. Black

[ Oops ! I'm reposting to include those in Sci.Chem, Sci.Astro ]

Hello there Sam, Dwib, Mr. Back, RichD and Bert,

Quoting WikiPedia.ORG:

“ The [ earth's ] original atmosphere was primarily helium and hydrogen.
Heat from the still-molten crust, and the sun,
plus a probably enhanced solar wind, dissipated this atmosphere. �.

The cosmic-wide, eternal, second law of thermodynamics
means everything spews... non stop.

The Sun spews, Venus spews, even the earth spews.
Were it not so, the great engine of life would lie motionless.
The arrow of time is a meause of what has been, or will be, consumed.

Intrinsically ( i.e. irregardless of what is or isn't known )
time is a spatial dimension, i.e. the hypervolume ( a.k.a. spacetime )
is motionless. For Sam and Dwib, here are some quotes on this:

From Einstein's, “ Ether and the Theory of Relativity � ( 1920 ):

“ But this ether [ i.e. Relativity ] may not be thought of as
endowed with the quality characteristic of ponderable media,
as consisting of parts which may be tracked through time.

The idea of motion may not be applied to it. �.
[ http://TUHH.DE/rzt/rzt/it/Ether.html ]

From Einstein's " The World As I See It " ( 1949 ):

“ But the scientist is possessed by
the sense of -- universal causation -- . The future, to him,
is every whit as necessary and determined as the past. �.
[ http://EinsteinAndReligion.COM/sciencereligious.html ]

Einstein, on the loss of his old friend, wrote:

“ People like us, who believe in physics, know that
the distinction between past, present, and future is
only a stubbornly persistent illusion. �.

http://SpeakingOfFaith.PublicRadio.O...eardcuts.shtml

Quoting Scientific American's “ That Mysterious Flow � ( Sep 2002 ):

“ From the fixed past to the tangible present to the undecided future,
it feels as though time flows inexorably on.
But that is an illusion. �.

http://Urgrue.ORG/lib/mysterious-flow.html

Quoting Petkov's,
“ Is There an Alternative to the Block Universe View ? �:

“ This paper pursues two aims.

First, to show that the block universe view, regarding the universe as
a timelessly existing four-dimensional world,
is the only one that is consistent with special relativity.

Second, to argue that special relativity alone can resolve
the debate on whether the world is
three-dimensional or four-dimensional.

The argument advanced in the paper is that
if the world were three-dimensional

the kinematic consequences of special relativity and more importantly
the experiments confirming them would be impossible. �.
[ http://Philsci-Archive.Pitt.EDU/archive/00002408/ ]

On Dec 1, Jim Black wrote:
When someone claims "life reduces entropy", the
usual retort is that the energy derives from the
sun (photosynthesis), and the sun is pouring energy
into space at a massive rate, with concomitant
increase in entropy.

My question is: how does one compute this solar
rate of entropy increase? Boltzmann's k log W
formula doesn't seem to apply -

That explanation is not quite correct. The reason
living organisms can decrease their own internal entropy
is that when they use energy, they create heat, which
increases the entropy of their environment. This heat is eventually
radiated away into space, of course.
Boltzmann's k log W does apply; when there are
more photons flying around, there are more ways they could be
distributed.

OK, that would be a statistical description, involving
quantum mechanics. However...

Using that approach, how would one compute the
state space of the photons?

If we assume pre-quantum theory physics (set h=0),
given the sun radiates at X Watts into a vacuum,
how would we compute the rate of entropy increase?


If we summon the shade of Maxwell, what
answer would he give?

I can't believe this is an unsolved problem in physics.

--
Rich

On Wed, 5 Dec 2007 18:21:16 -0800 (PST), RichD wrote:

On Dec 1, Jim Black wrote:
Boltzmann's k log W does apply; when there are
more photons flying around, there are more ways they could be
distributed.

OK, that would be a statistical description, involving
quantum mechanics. However...

Using that approach, how would one compute the
state space of the photons?

You can break the EM field up into orthogonal modes and assign each mode an
integer number of photons. That gives you a set of possible microstates.
Then you'd need to figure out the distribution of microstates.

If we assume pre-quantum theory physics (set h=0),
given the sun radiates at X Watts into a vacuum,
how would we compute the rate of entropy increase?

Classical physics will give you severely wrong answers. Remember that
Planck came up with his constant when studying the blackbody distribution!

Just using basic thermodynamics, though, the sun's entropy should decrease
by Q/T, and the electromagnetic field's entropy should increase by Q/T,
where Q is the energy of the light emitted, and T is the surface
temperature of the sun.

I'm not convinced there is a net entropy increase. If you surrounded the
sun by a perfectly reflecting spherical mirror, then wouldn't the light be
reflected back to the sun, where it would be absorbed? Of course, there's
diffraction and incomplete absorption to worry about, which might lead to a
nonzero entropy increase, but surely it would be small compared to Q/T.

Then again, we can't build a mirror around the sun, at least not with our
current resources, so for all practical purposes, the light's never coming
back. You could potentially argue that there's an effective entropy
increase.

If the world were classical, all entropy increase would be of an
effective/subjective kind, since volume in phase space would be conserved.
But even if phase space volume is conserved, it's still possible for
chaotic processes to stretch and fold the region, increasing its volume for
practical purposes. Quantum mechanics allows for entropy increase through
wavefunction collapse, but no one agrees whether wavefunction collapse (or
something else that increases entropy) exists objectively. It's possible
that light leaving a star undergoes wavefunction collapse, but I can't
think of a test that could prove it doesn't happen without making
unwarranted assumptions.

--
Jim E. Black

Jim Black wrote:

Then again, we can't build a mirror around the sun, at least not with our
current resources, so for all practical purposes, the light's never coming
back. You could potentially argue that there's an effective entropy
increase.

If the world were classical, all entropy increase would be of an
effective/subjective kind, since volume in phase space would be conserved.
But even if phase space volume is conserved, it's still possible for
chaotic processes to stretch and fold the region, increasing its volume for
practical purposes. Quantum mechanics allows for entropy increase through
wavefunction collapse, but no one agrees whether wavefunction collapse (or
something else that increases entropy) exists objectively. It's possible
that light leaving a star undergoes wavefunction collapse, but I can't
think of a test that could prove it doesn't happen without making
unwarranted assumptions.


Entropy increases whenever thermal conduction occurs, for instance. The
Sun's energy is generated at very high temperature near its core, then
transported through the bulk of the Sun by convection, which is nearly
but not quite adiabatic. The outer layers of the Sun are dominated by
radiation and some conduction. There's no way to get the heat to flow
spontaneously from the 6000 K surface of the photosphere back to the ~
10 MK edge of the convective zone, so there is a significant entropy
increase involved.

Cheers,

Phil Hobbs