A definition for entropy that doesnt mention thermodynamics
Steve and Lesa
interested in the particulars let me know and I will post all the necessary
information to properly cite the source.
It was the 3rd. definition. Definitions 1 and 1a dealt with the 2nd Law of
Thermodynamics, the 2nd definition had to do with logarithms and message
frequency and the 3rd was the one that caught my eye:
....3 the degradation of the matter and energy in the universe to an ultimate
state of inert uniformity.
Ok before the attacks begin all I am interested in knowing is:
1) Is the 3rd definition an accepted scientific definition for entropy
2) If not, why?
3) Is the 3rd definition another way to state the 2nd Law of Thermodynamics
I am not really interested in hearing anything other than that. I have had
my share of drivel for this evening. I am not denying of defending any
cause, so save the soapbox for another day please.
Wade Hines
Steve and Lesa wrote:
>
> I have a definition of entropy I got out of Webster's, if anyone is really
> interested in the particulars let me know and I will post all the necessary
> information to properly cite the source.
>
> It was the 3rd. definition. Definitions 1 and 1a dealt with the 2nd Law of
> Thermodynamics, the 2nd definition had to do with logarithms and message
> frequency and the 3rd was the one that caught my eye:
>
> ....3 the degradation of the matter and energy in the universe to an ultimate
> state of inert uniformity.
Eck.
> Ok before the attacks begin all I am interested in knowing is:
> 1) Is the 3rd definition an accepted scientific definition for entropy
No. that's what you get when you look at an english dictionary for a
scientific term.
> 2) If not, why?
You've been told the definition of entropy and told to look it up in
chemistry books. Apparently your questions aren't very sincere. If
you look it up you'll find it has a definition there and that entropy
has certain units attached. If you look at your #3 definition, you'll
see it defies units. That gives the same term "entropy", two mutually
exclusive meanings and further gives one of the meanings an overlap
with another. It would be somewhat like having the same word mean
distance and accelloration only worse.
> 3) Is the 3rd definition another way to state the 2nd Law of Thermodynamics
Not a very good way. The real second law of thermodynamics is mathematical.
It provides that you have to do a full accounting. This bumper sticker
version makes one think you can understand things in generalized terms.
For instance, iron turns to rust and this seems to be a degradation of
matter but the oxyidation of iron represents a decrease in entropy!
Tell me how the slobbish definition you've been given would help one
understand that.
> I am not really interested in hearing anything other than that. I have had
> my share of drivel for this evening. I am not denying of defending any
> cause, so save the soapbox for another day please.
Quit pretending not to be a creationist.
Sverker Johansson
>
> I have a definition of entropy I got out of Webster's, if anyone is really
> interested in the particulars let me know and I will post all the necessary
> information to properly cite the source.
>
> It was the 3rd. definition. Definitions 1 and 1a dealt with the 2nd Law of
> Thermodynamics, the 2nd definition had to do with logarithms and message
> frequency and the 3rd was the one that caught my eye:
>
> ....3 the degradation of the matter and energy in the universe to an ultimate
> state of inert uniformity.
>
> Ok before the attacks begin all I am interested in knowing is:
> 1) Is the 3rd definition an accepted scientific definition for entropy
Not really. It is rather a loose statement of the very long term
_consequences_ of the 2nd law.
> 2) If not, why?
Because it is not a statement of the local workings of the
2nd law itself, only its consequences.
Because it is sloppily stated with no quantification and based
on loosely defined terms.
> 3) Is the 3rd definition another way to state the 2nd Law of Thermodynamics
It has its pedagogical uses, but it is not a good rigorous way to
state it.
Why would you expect scientific definitions out of Webster's anyway?
Webster's attempts to define language as used in everyday life,
which is frequently different from how it's used in science.
> I am not really interested in hearing anything other than that. I have had
> my share of drivel for this evening. I am not denying of defending any
> cause, so save the soapbox for another day please.
In this group, we've had much experience with people who come here
telling us they don't have an agenda. Our experience tells us
that a claim not to have an agenda is usually a realible sign of
_having_ an agenda. I hope you belong to the sincere minority.
--
Best regards, HLK, Physics
Sverker Johansson U of Jonkoping
----------------------------------------------
Definitions:
Micro-evolution: evolution for which the evidence is so
overwhelming that even the ICR can't deny it.
Macro-evolution: evolution which is only proven beyond
reasonable doubt, not beyond unreasonable doubt.
John Pieper
Why are you being so defensive? I haven't seen any attacks on you. Several
posters have provided you with good information. I wouldn't characterize
any of it as "drivel".
Anyway, to your questions:
(1) No, it's not a good definition.
(2) What that definition is *trying* to describe is the second law of
thermo, not entropy.
(3) It isn't even a good definition of the second law. There are too many
subtleties involved in thermo for a non-specialized dictionary to do
a good job at it. Much better definitions would be found in a physics
or chemistry text.
--
John Pieper |"Politics and religion are obsolete; the time has come
jbp34 |for science and spirituality."--Jawaharlal Nehru
@home |
Steve Carlip
> Steve and Lesa wrote:
>> I have a definition of entropy I got out of Webster's, if anyone is
>> really interested in the particulars let me know and I will post all
>> the necessary information to properly cite the source.
>> It was the 3rd. definition. Definitions 1 and 1a dealt with the 2nd Law
>> of Thermodynamics, the 2nd definition had to do with logarithms and
>> message frequency and the 3rd was the one that caught my eye:
>> ....3 the degradation of the matter and energy in the universe to an
>> ultimate state of inert uniformity.
> Eck.
Double eck! This is not only not a definition of entropy, it's flat-out
wrong as a statement of physics.
Which has more entropy, an ``inert uniform'' cloud of hydrogen or the
same hydrogen clumped together into stars? The answer is the latter.
In any system in which gravity is an important force, an ``inert uniform''
state has *low* entropy compared to a lumpy, uneven state. The highest
entropy state is typically the one in which the matter is all compacted
together to form a black hole.
In fact, one of the major unsolved problems of cosmology is the problem
of why the Universe seems to have started out so uniform, since that's
a state of such low entropy.
Steve Carlip
Steve and Lesa
"Steve and Lesa" <sl...@home.com> wrote in message
news:GI3K7.23012$Ms4.2...@news1.rdc1.va.home.com...
Thank you very much for the insults. I tried to preface everything I said
so as not to be "labeled" apparently I overestimated so of you. I am trying
to understand that is all. I am genuinely confused and while I don't
possess the intellectual understanding of the subject yet to draw my own
conclusions, does that mean I can not look for that understanding. Not
being a trained sciencetist I have only my experience to draw conclusions
upon, most of my experience has either been through a inaccurate definition
of entropy and some of the flawed arguments that a couple of the sincere
repliers have pointed out. If this makes me a creationist according to this
forum then I am a creationist. I belief the term ad hominem is used when
attacking the person rather than the idea, and while only a few people have
I belief attacked me, insignificant or not, I try to remain open minded.
All I was asking for was some clarification from the people who claim to
have the understanding of the subject. While I have read many post from
other people and have seen the "creationist" who under the guise of a
curious person would try to back door you into in one of what I say to be
repetitive flaws in their logic. I understand that what I am doing can be
construed as such, but again being somewhat of an active thinker, and a
person who possess free will, I am going to question something if it either
is vague or goes against what my previous understanding is. I think some of
you are conditioned to such a irresponsible act trying to stifle those of us
who are just confused. No agenda just a search for the ultimate truth,
whether that be evolution, creation or something else that non of us have
the cognizance to understand. While I again thank those of you who
genuinely answered my post, I suggest that those who jump to hasty
conclusions, to step back take a breath and don't assume every post that
mentions entropy is a conspiracy against your beliefs. I just wanted a
straight answer not a sermon. I am trying to form a basis so I can defend
it in a paper. It is not a dissertation, thesis, or anything like that it
is just for a class. It is something that has been on my mind but until now
either through laziness, apathy or some other power I didn't explore the
possibilities. Thanks again, anyone that would like to add their opinion
please do, but save the soapbox, I am not looking to have my character
assassinated by those who ignore or don't understand that I just need some
clarification.
J Forbes
I suggest you *ignore* what you consider to be
attacks (there weren't very many, as replies on t.o.
go) and just read what the informative replies say.
If you want an accurate definition of entropy, which
is a scientific term, you need to look to scientific
sources! Webster's won't do it.
I think you've been given the info you need...so you
don't need to be defensive, just take the info and
do what you need to with it.
But if you have more questions, we'll be glad to
answer them. The straightforward approach seems to
be best--don't bother with the disclaimers, just ask
the questions. :)
Jim
TomS
<GI3K7.23012$Ms4.2...@news1.rdc1.va.home.com>, "Steve stated..."
>
>I have a definition of entropy I got out of Webster's, if anyone is really
>interested in the particulars let me know and I will post all the necessary
>information to properly cite the source.
May I ask, when you refer to "Webster's", which dictionary you
mean? The name "Webster's" can be used by anyone, and not all of
these are of the highest quality.
Tom S.
Bob Pease
> interested in the particulars let me know and I will post all the
necessary
> information to properly cite the source.
>
> It was the 3rd. definition. Definitions 1 and 1a dealt with the 2nd Law
of
> Thermodynamics, the 2nd definition had to do with logarithms and message
> frequency and the 3rd was the one that caught my eye:
>
> ....3 the degradation of the matter and energy in the universe to an
ultimate
> state of inert uniformity.
>
> Ok before the attacks begin all I am interested in knowing is:
> 1) Is the 3rd definition an accepted scientific definition for entropy
NO.
Entropy is defined Scientifically in any College Physics book.
The definition given is a commonly believed CONSEQUENCE of the 2LT
> 2) If not, why?
I think you mean "Why did not the original theorists use THIS as a principal
definition?"
Such a definition would have been speculative, vague, and not useful
mathematically .
Scientists do not define things this loosely. The definition given is a
popularized
version of a theory applying the 2LT to a theoretical model of the Universe.
Even so, the definition given lacks precision in English. Being in a
dictionary as #3, it deserves inclusion , but not all dictionary inclusions
of any word are suitable as Scientific Definitions.
Take, for example, WORK, POWER, FORCE, to name a few.
> 3) Is the 3rd definition another way to state the 2nd Law of
Thermodynamics
Absolutely not.
The 2LT is a statement declaring that under certain conditions, Entropy
always increases. Entropy is Defined separately from the 2LT without any
speculation or theories about the Universe.
As stated, Def#3 is only a vague representation of theoretical consequences
of the 2LT.
Taken in this context it's not really that bad.
> I am not really interested in hearing anything other than that. I have
had
> my share of drivel for this evening. I am not denying of defending any
> cause, so save the soapbox for another day please.
I have tried to remain neutral about this.
RJ Pease
Noelie S. Alito
news:9tbqj...@drn.newsguy.com...
Even a high-quality general language dictionary is not appropriate
for scientific, engineering or other technical jargon. (Is there a
"Webster's Dictionary of Scientific Terms", perhaps?)
Noelie
--
"You keep using that word. I do not think it means what
you think it means." --Inigo Montoya, _TPB_
Wade Hines
Steve and Lesa wrote:
>
> "Steve and Lesa" <sl...@home.com> wrote in message
> news:GI3K7.23012$Ms4.2...@news1.rdc1.va.home.com...
> > I have a definition of entropy I got out of Webster's, if anyone is really
> > interested in the particulars let me know and I will post all the
> necessary
> > information to properly cite the source.
> >
> > It was the 3rd. definition. Definitions 1 and 1a dealt with the 2nd Law
> of
> > Thermodynamics, the 2nd definition had to do with logarithms and message
> > frequency and the 3rd was the one that caught my eye:
> >
> > ....3 the degradation of the matter and energy in the universe to an
> ultimate
> > state of inert uniformity.
> >
> > Ok before the attacks begin all I am interested in knowing is:
> > 1) Is the 3rd definition an accepted scientific definition for entropy
> > 2) If not, why?
> > 3) Is the 3rd definition another way to state the 2nd Law of
> Thermodynamics
> >
> > I am not really interested in hearing anything other than that. I have
> had
> > my share of drivel for this evening. I am not denying of defending any
> > cause, so save the soapbox for another day please.
I will only note that these broad brush claims of having been insulted
are displaced from any of these supposed insults making it impossible
for someone to judge the accuracy of these accusations.
Buckler
wrote:
>
>"Steve and Lesa" <sl...@home.com> wrote in message
>news:GI3K7.23012$Ms4.2...@news1.rdc1.va.home.com...
>> I have a definition of entropy I got out of Webster's, if anyone is really
>> interested in the particulars let me know and I will post all the
>necessary
>> information to properly cite the source.
<snip>
>Thank you very much for the insults. I tried to preface everything I said
>so as not to be "labeled" apparently I overestimated so of you. I am trying
>to understand that is all. I am genuinely confused and while I don't
>possess the intellectual understanding of the subject yet to draw my own
>conclusions, does that mean I can not look for that understanding. Not
>being a trained sciencetist I have only my experience to draw conclusions
>upon, most of my experience has either been through a inaccurate definition
>of entropy and some of the flawed arguments that a couple of the sincere
>repliers have pointed out. If this makes me a creationist according to this
>forum then I am a creationist.
<snip>
Forgive me, but I can't see how you've been abused in any way. Given
your initial statement that you are not well-versed in science, I
think folks here have tried very hard to present the information you
requested in a manner that accommodates your request. Most of the
regulars in this group respect and admire anyone who's looking for
knowledge, and who is as polite in requesting it as you have been.
Having been ignorant of several topics of interest here myself, I have
found that T.O. has been a veritable font of knowledge, with nary an
insult. If you are a creationist, then so be it. If you are a
creationist looking for scientific information, you are doubly welcome
here.
Now, if you take offense at the scientific information presented,
there is little that anyone here can do about that. This is the
information that science has, and is what you asked for.
Perhaps you feel slighted by the offhand dismissals of misunderstood
references to the 2nd Law of Thermodynamics. Note that any such
references are not personal, they are the result of the deliberate
twisting and manipulation of the 2nd Law by the ultra-conservative
creationists, to their own ends. I would ask your forbearance to such
attitudes, and only continue to ask honest questions, as you have
done. If you continue to present yourself as someone honestly seeking
to learn new things, you will be treated as such; I only ask you to
keep in mind that the history of this newsgroup is rife with people
asking precisely the questions you have, but with the ulterior motive
of attempting to undermine its precepts. I don't believe you have that
intent.
Please don't be so defensive. Listen, learn, and contribute. You are
welcome here.
My two cents' worth...
Buckler
Bobby D. Bryant
Lesa" <sl...@home.com> wrote:
> I have a definition of entropy I got out of Webster's, if anyone is
> really interested in the particulars let me know and I will post all the
> necessary information to properly cite the source.
Re your subject line, entropy is a thermodynamic concept, so it's not
clear that a definition that doesn't mention thermodynamics is going to be
good for very much.
[Actually, Shannon used the same mathematical form for his analysis of
"information", and still called the concept "entropy" by analogy, as per
your Webster's definition #2 and the explanations in other recent
threads.]
> It was the 3rd. definition. Definitions 1 and 1a dealt with the 2nd Law
> of Thermodynamics, the 2nd definition had to do with logarithms and
> message frequency and the 3rd was the one that caught my eye:
>
> ....3 the degradation of the matter and energy in the universe to an
> ultimate state of inert uniformity.
Though the word "thermodynamics" doesn't appear here, it's still a
thermodynamic concept. The idea is that as time approaches infinity the
amount of heat in the universe that can be exploited for work approaches
zero -- the so-called "heat death" of the universe.
I'm not sure that #3 has the details of the ultimate state of the universe
correct, and I certainly wouldn't offer that phrase as a definition of
entropy, but it's clearly referring to a thermodynamic concept.
So Webster gives you two concepts of entropy: #1 and #3 from
thermodynamics, and #2 from information theory.
And as others have pointed out, the concepts have specific, mathematically
defined properties in their respective theories.
> Ok before the attacks begin ...
> I am not really interested in hearing anything other than that. I have
> had my share of drivel for this evening. I am not denying of defending
> any cause, so save the soapbox for another day please.
Whatever set you off, we're not interested in *your* soapbox either. So
save it for another day, please.
Bobby Bryant
Austin, Texas
Steve and Lesa
Thanks for the reply. I appreciate your kind words, and let me say that
mostly my experience has been a pleasant one, regarding this forum. While I
am perhaps misunderstood by a few people, mostly I have received not only
excellent information, but have been directed to outside sources that I have
found most helpful.
Thanks
Steve
"Buckler" <buck...@yahoo.com> wrote in message
news:3tijvtkk7gbvl6ldn...@4ax.com...
Buckler
wrote:
>Buckler,
>
>Thanks for the reply. I appreciate your kind words, and let me say that
>mostly my experience has been a pleasant one, regarding this forum. While I
>am perhaps misunderstood by a few people, mostly I have received not only
>excellent information, but have been directed to outside sources that I have
>found most helpful.
>
>Thanks
>
>Steve
I hope your experience here is a pleasant and productive one.
Buckler
Steve and Lesa
Thanks for the reply. Where I was confused was if entropy could be seen as
independent from thermodynamics. I understand the relationship between the
ratio and heat transfer, but it was explained in a different light, by an
educator, who at the time I had no reason to doubt. Having researched it
further and with the help of all that replied I see where the
misinterpretation lied. That is why I went to the dictionary in first
place. It was the only place I could find any information to agree from
what I heard. Thanks for the additional clarification.
Steve
"Bobby D. Bryant" <bdbr...@surya.csres.utexas.edu> wrote in message
news:9tc8t3$q31$1...@geraldo.cc.utexas.edu...
Charles Wagner
Steve Carlip wrote:
> Wade Hines <wade....@rcn.com> wrote:
>
> > Steve and Lesa wrote:
>
> >> I have a definition of entropy I got out of Webster's, if anyone is
> >> really interested in the particulars let me know and I will post all
> >> the necessary information to properly cite the source.
>
> >> It was the 3rd. definition. Definitions 1 and 1a dealt with the 2nd Law
> >> of Thermodynamics, the 2nd definition had to do with logarithms and
> >> message frequency and the 3rd was the one that caught my eye:
>
> >> ....3 the degradation of the matter and energy in the universe to an
> >> ultimate state of inert uniformity.
>
> > Eck.
>
> Double eck! This is not only not a definition of entropy, it's flat-out
> wrong as a statement of physics.
>
> Which has more entropy, an ``inert uniform'' cloud of hydrogen or the
> same hydrogen clumped together into stars? The answer is the latter.
> In any system in which gravity is an important force, an ``inert uniform''
> state has *low* entropy compared to a lumpy, uneven state. The highest
> entropy state is typically the one in which the matter is all compacted
> together to form a black hole.
I swore I wasn't going to get involved in this again, but this is such a
glaring error that I must point it out. Perhaps somewhere down the thread this
has happened, but I'm not going through it all. You have it exactly backwards.
The highest entropy state is the one in which matter is most disorderly.
Entropy is the measure of the degree of disorder. The greater the disorder, the
higher the entropy. An inert cloud of hydrogen has far more entropy than a
star.
>
>
> In fact, one of the major unsolved problems of cosmology is the problem
> of why the Universe seems to have started out so uniform, since that's
> a state of such low entropy.
The "major unsolved question of cosmology" is where the low entropy of the
stars came from. If the universe started out so uniform, how did this high
entropy change into the low entropy that we now find in stars.
Regards, Charlie Wagner
http://www.charliewagner.com
>
>
> Steve Carlip
>
>
Charles Wagner
1. Yes
2. N/A
3. Yes
If you want to stop there, fine, but I'll include an explanation below:
Entropy is the measurement of the disorder of a system. Highly ordered systems
have low entropy, highly disordered systems have high entropy. A gas has greater
entropy than the same substance in liquid or solid form. We have observed that if
the laws of nature are allowed to act without interference, a disorderly system
is more probable.
This is a perfectly valid way of stating the 2nd law of thermodynamics. Boltzmann
added a constant to the definition to allow it to be expressed mathematically,
but it is an equivalent statement of the 2nd law and they can be shown to be
equivalent.
The mathematical statement of entropy is S = k ln W where S is the entropy, k is
Boltzmann's constant and ln W (ln is natural log) is a number proportional to the
probability of the occurrence of a particular event.
This is probably more than you needed, but entropy is a slippery term that
many people confuse and misuse.
Regards, Charlie Wagner
http://www.charliewagner.com
Wade Hines
Nope. The star is hotter. In general, the same thing hotter has more entropy.
Gravitational collapse is complicated and involves some twists but it is
spontaneous and overall a positive entropy change.
Wade Hines
Charles Wagner wrote:
>
> The simple answers to your questions (despite what others may say) are:
> 1. Yes
> 2. N/A
> 3. Yes
>
> If you want to stop there, fine, but I'll include an explanation below:
>
> Entropy is the measurement of the disorder of a system. Highly ordered systems
> have low entropy, highly disordered systems have high entropy. A gas has greater
> entropy than the same substance in liquid or solid form. We have observed that if
> the laws of nature are allowed to act without interference, a disorderly system
> is more probable.
> This is a perfectly valid way of stating the 2nd law of thermodynamics.
It isn't wrong but it misses out on the exacting quantitative nature
of entropy. Further, there are times that intuition of "order" and "disorder"
utterly fail. The first of these is the obvious one of two metal plates.
If we order their energies so that each are the same temperature is that
a higher or lower entropy than when the two plates had their energy
disorganized so that they have different temperatures. Most semieducated
amatures know that the state where they have the same T is the higher entropy
and that in fact that provides for greater randomization of energy and
can use the English terms "order" and "disorder" in ways that make it all
seem to be obvious. The reality is that "order" and "disorder" are
innept classifications for working backwards to entropy. They seem useful
for pedological characterization in situations where the entropy changes
are known but that's a different thing.
> Boltzmann
> added a constant to the definition to allow it to be expressed mathematically,
> but it is an equivalent statement of the 2nd law and they can be shown to be
> equivalent.
> The mathematical statement of entropy is S = k ln W where S is the entropy, k is
> Boltzmann's constant and ln W (ln is natural log) is a number proportional to the
> probability of the occurrence of a particular event.
> This is probably more than you needed, but entropy is a slippery term that
> many people confuse and misuse.
I wholeheartedly agree with your final clause. You've made that case well.
Charles Wagner
Wade Hines wrote:
> Charles Wagner wrote:
> >
> > Steve Carlip wrote:
> >
> > > Wade Hines <wade....@rcn.com> wrote:
> > >
> > > > Steve and Lesa wrote:
> > >
> > > >> I have a definition of entropy I got out of Webster's, if anyone is
> > > >> really interested in the particulars let me know and I will post all
> > > >> the necessary information to properly cite the source.
> > >
> > > >> It was the 3rd. definition. Definitions 1 and 1a dealt with the 2nd Law
> > > >> of Thermodynamics, the 2nd definition had to do with logarithms and
> > > >> message frequency and the 3rd was the one that caught my eye:
> > >
> > > >> ....3 the degradation of the matter and energy in the universe to an
> > > >> ultimate state of inert uniformity.
> > >
> > > > Eck.
> > >
> > > Double eck! This is not only not a definition of entropy, it's flat-out
> > > wrong as a statement of physics.
> > >
> > > Which has more entropy, an ``inert uniform'' cloud of hydrogen or the
> > > same hydrogen clumped together into stars? The answer is the latter.
> > > In any system in which gravity is an important force, an ``inert uniform''
> > > state has *low* entropy compared to a lumpy, uneven state. The highest
> > > entropy state is typically the one in which the matter is all compacted
> > > together to form a black hole.
> >
> > I swore I wasn't going to get involved in this again, but this is such a
> > glaring error that I must point it out. Perhaps somewhere down the thread this
> > has happened, but I'm not going through it all. You have it exactly backwards.
> > The highest entropy state is the one in which matter is most disorderly.
> > Entropy is the measure of the degree of disorder. The greater the disorder, the
> > higher the entropy. An inert cloud of hydrogen has far more entropy than a
> > star.
>
> Nope. The star is hotter. In general, the same thing hotter has more entropy.
> Gravitational collapse is complicated and involves some twists but it is
> spontaneous and overall a positive entropy change.
With all due respect, you are absolutely and completely wrong.
Regards, Charlie Wagner
http://www.charliewagner.com
>
>
> > > In fact, one of the major unsolved problems of cosmology is the problem
> > > of why the Universe seems to have started out so uniform, since that's
> > > a state of such low entropy.
> >
R. Tang
>Charles Wagner wrote:
>>
>> The simple answers to your questions (despite what others may say) are:
>> 1. Yes
>> 2. N/A
>> 3. Yes
>>
>> If you want to stop there, fine, but I'll include an explanation below:
>>
>> Entropy is the measurement of the disorder of a system. Highly ordered systems
>> have low entropy, highly disordered systems have high entropy. A gas has greater
>> entropy than the same substance in liquid or solid form. We have observed that if
>> the laws of nature are allowed to act without interference, a disorderly system
>> is more probable.
>> This is a perfectly valid way of stating the 2nd law of thermodynamics.
>
>It isn't wrong but it misses out on the exacting quantitative nature
>of entropy.
Remember, you're talking to a person who thinks equations are
not necessary when talking about thermodynamics.
Although, given that he talks about "measures", you would think
that implies equations....
Hrmmm. Dictionary definitions are fine for everyday languages, but
if you ARE talking about measurement (and you can with entropy), you
really have to go beyond the dictionary, go to the equations and work them
out....
--
-
-Roger Tang, gwan...@u.washington.edu, Artistic Director PC Theatre
- Editor, Asian American Theatre Revue [NEW URL][Yes, it IS new]
- http://www.aatrevue.com
Charles Wagner
Wade Hines wrote:
> Charles Wagner wrote:
> >
> > Steve Carlip wrote:
> >
> > > Wade Hines <wade....@rcn.com> wrote:
> > >
> > > > Steve and Lesa wrote:
> > >
> > > >> I have a definition of entropy I got out of Webster's, if anyone is
> > > >> really interested in the particulars let me know and I will post all
> > > >> the necessary information to properly cite the source.
> > >
> > > >> It was the 3rd. definition. Definitions 1 and 1a dealt with the 2nd Law
> > > >> of Thermodynamics, the 2nd definition had to do with logarithms and
> > > >> message frequency and the 3rd was the one that caught my eye:
> > >
> > > >> ....3 the degradation of the matter and energy in the universe to an
> > > >> ultimate state of inert uniformity.
> > >
> > > > Eck.
> > >
> > > Double eck! This is not only not a definition of entropy, it's flat-out
> > > wrong as a statement of physics.
> > >
> > > Which has more entropy, an ``inert uniform'' cloud of hydrogen or the
> > > same hydrogen clumped together into stars? The answer is the latter.
> > > In any system in which gravity is an important force, an ``inert uniform''
> > > state has *low* entropy compared to a lumpy, uneven state. The highest
> > > entropy state is typically the one in which the matter is all compacted
> > > together to form a black hole.
> >
> > I swore I wasn't going to get involved in this again, but this is such a
> > glaring error that I must point it out. Perhaps somewhere down the thread this
> > has happened, but I'm not going through it all. You have it exactly backwards.
> > The highest entropy state is the one in which matter is most disorderly.
> > Entropy is the measure of the degree of disorder. The greater the disorder, the
> > higher the entropy. An inert cloud of hydrogen has far more entropy than a
> > star.
>
> Nope. The star is hotter. In general, the same thing hotter has more entropy.
Water vapor at room temperature still has more entropy than an equal amount of water
at 372K , despite its lower temperature. Entropy measures disorder. Gases are more
disorderly than liquids and solids and when the universe reaches it's "heat death",
when no energy will be available to do work, the universe will be at maximum entropy.
>
> Gravitational collapse is complicated and involves some twists but it is
> spontaneous and overall a positive entropy change.
It is not spontaneous, which is the main reason why certain cosmological theories
that have the gases contracting under gravity are pure baloney. And it is definitely
a negative entropy change.
Regards, Charlie Wagner
http://www.charliewagner.com
>
>
> > > In fact, one of the major unsolved problems of cosmology is the problem
> > > of why the Universe seems to have started out so uniform, since that's
> > > a state of such low entropy.
> >
Derek Stevenson
news:3BFA9959...@charliewagner.com...
> Wade Hines wrote:
> > Nope. The star is hotter. In general, the same thing hotter has more
entropy.
> > Gravitational collapse is complicated and involves some twists but it is
> > spontaneous and overall a positive entropy change.
>
> With all due respect, you are absolutely and completely wrong.
>
> Regards, Charlie Wagner
> http://www.charliewagner.com
I've always maintained that if your sanity is questioned by Ed Conrad,
that's as clear and unequivocal an indication of your sound mental health as
it is possible to have.
Should the same apply to being told you're wrong by Charlie Wagner?
Chris Ho-Stuart
>> > I swore I wasn't going to get involved in this again, but
>> > this is such a glaring error that I must point it out. Perhaps
>> > somewhere down the thread this has happened, but I'm not going
>> > entropy state is the one in which matter is most disorderly.
>> > Entropy is the measure of the degree of disorder. The greater
>> > the disorder, the higher the entropy. An inert cloud of hydrogen
>> > has far more entropy than a star.
>>
>> has more entropy. Gravitational collapse is complicated and
>> involves some twists but it is spontaneous and overall a positive
>> entropy change.
>
> With all due respect, you are absolutely and completely wrong.
An inert cloud of gas will spontaneously collapse and heat up,
and this can form a star. Like any other spontaneous process,
gravitational collapse involves an increase in entropy. The
collapse reduces the potential energy of the cloud, and increases
its heat energy. This is a conversion of "usable" energy into
heat -- a classic irrevesible (entropy increasing) process.
In short, Wade is quite correct.
Speaking of entropy as "disorder" without applying the appropriate
actual definitions used in thermodynamics is invariably misleading.
Thermodymically, the hot dense gas of a star is more disordered
than the cooler diffuse gas of a cloud, if we are using "disorder"
to mean "higher entropy".
Cheers -- Chris
Charles Wagner
Derek Stevenson wrote:
> "Charles Wagner" <cha...@charliewagner.com> wrote in message
> news:3BFA9959...@charliewagner.com...
> > Wade Hines wrote:
>
> > > Nope. The star is hotter. In general, the same thing hotter has more
> entropy.
> > > Gravitational collapse is complicated and involves some twists but it is
> > > spontaneous and overall a positive entropy change.
> >
> > With all due respect, you are absolutely and completely wrong.
> >
> > Regards, Charlie Wagner
> > http://www.charliewagner.com
>
> I've always maintained that if your sanity is questioned by Ed Conrad,
> that's as clear and unequivocal an indication of your sound mental health as
> it is possible to have.
>
> Should the same apply to being told you're wrong by Charlie Wagner?
Whether something is correct or not is independent of the speaker. The biggest
moron in the world can say that the earth is round.
Charles Wagner
Chris Ho-Stuart wrote:
> Charles Wagner <cha...@charliewagner.com> wrote:
> > Wade Hines wrote:
> >> Charles Wagner wrote:
> [snip]
> >> > I swore I wasn't going to get involved in this again, but
> >> > this is such a glaring error that I must point it out. Perhaps
> >> > somewhere down the thread this has happened, but I'm not going
> >> > through it all. You have it exactly backwards. The highest
> >> > entropy state is the one in which matter is most disorderly.
> >> > Entropy is the measure of the degree of disorder. The greater
> >> > the disorder, the higher the entropy. An inert cloud of hydrogen
> >> > has far more entropy than a star.
> >>
> >> Nope. The star is hotter. In general, the same thing hotter
> >> has more entropy. Gravitational collapse is complicated and
> >> involves some twists but it is spontaneous and overall a positive
> >> entropy change.
> >
> > With all due respect, you are absolutely and completely wrong.
>
> An inert cloud of gas will spontaneously collapse and heat up,
> and this can form a star.
Baloney.
> Like any other spontaneous process,
> gravitational collapse involves an increase in entropy.
More baloney. It's a decrease in entropy.
> The
> collapse reduces the potential energy of the cloud,
> and increases
> its heat energy. This is a conversion of "usable" energy into
> heat -- a classic irrevesible (entropy increasing) process.
Baloney. If it happens like you say (it doesn't) then it's a conversion
of unusable energy into usable energy.
>
>
> In short, Wade is quite correct.
Baloney. He's wrong and so are you.
You know, it's OK to play with my head, but there are innocents reading
this who may believe you.
>
>
> Speaking of entropy as "disorder" without applying the appropriate
> actual definitions used in thermodynamics is invariably misleading.
> Thermodymically, the hot dense gas of a star is more disordered
> than the cooler diffuse gas of a cloud, if we are using "disorder"
> to mean "higher entropy".
Horse manure.
Regards, Charlie wagner
http://www.charliewagner.com
>
>
> Cheers -- Chris
Ferrous Patella
[...]
>
>Baloney.
>
[...]
>
>More baloney. It's a decrease in entropy.
>
>
>
>Baloney. If it happens like you say (it doesn't) then it's a conversion
>of unusable energy into usable energy.
>
>Baloney. He's wrong and so are you.
>You know, it's OK to play with my head, but there are innocents reading
>this who may believe you.
>
>>
>>
[...]
>Horse manure.
>
[...]
Charlie,
Thank you. These are very convincing arguments. They remind me of the ones you
used to convince your mathematician friend he was wrong about lotteries.
--
Ferrous Patella
SI HOC LEGERE SCIS NIMIUM ERUDITIONIS HABES
Bill Hudson
>
> Chris Ho-Stuart wrote:
>
> > Charles Wagner <cha...@charliewagner.com> wrote:
> > > Wade Hines wrote:
> > >> Charles Wagner wrote:
> > [snip]
> > >> > I swore I wasn't going to get involved in this again, but
> > >> > this is such a glaring error that I must point it out. Perhaps
> > >> > somewhere down the thread this has happened, but I'm not going
> > >> > through it all. You have it exactly backwards. The highest
> > >> > entropy state is the one in which matter is most disorderly.
> > >> > Entropy is the measure of the degree of disorder. The greater
> > >> > the disorder, the higher the entropy. An inert cloud of hydrogen
> > >> > has far more entropy than a star.
> > >>
> > >> Nope. The star is hotter. In general, the same thing hotter
> > >> has more entropy. Gravitational collapse is complicated and
> > >> involves some twists but it is spontaneous and overall a positive
> > >> entropy change.
> > >
> > > With all due respect, you are absolutely and completely wrong.
> >
> > An inert cloud of gas will spontaneously collapse and heat up,
> > and this can form a star.
>
> Baloney.
??
He is absolutly right. An 'inert' cloud of gas (hydrogen) which
contains enough mass (as much as a star) will collapse under its own
gravity, heat up, and begin the fusion process. The initial energy
(Ea) comes from the heat generated as the molecules bump into each
other. Once the H-burn starts, it is spontaneous, and loses a *lot* of
heat to the environment. That is an *increase* in entropy.
from http://www.2ndlaw.com/entropy.html; "...every single time something
spontaneous happens via energy spreading out
to the surroundings - like the old example of the hot pan cooling down -
entropy is +, positive."
> > Like any other spontaneous process,
> > gravitational collapse involves an increase in entropy.
>
> More baloney. It's a decrease in entropy.
>
> > The
> > collapse reduces the potential energy of the cloud,
>
> > and increases
> > its heat energy. This is a conversion of "usable" energy into
> > heat -- a classic irrevesible (entropy increasing) process.
>
> Baloney. If it happens like you say (it doesn't) then it's a conversion
> of unusable energy into usable energy.
>
> >
> >
> > In short, Wade is quite correct.
>
> Baloney. He's wrong and so are you.
> You know, it's OK to play with my head, but there are innocents reading
> this who may believe you.
Why don't you go read http://www.secondlaw.com and
http://www.2ndlaw.com? I'm no scientist, and I can't do the math, but
apparently I understand entropy and the SLOT better than you do...
>
> >
> >
> > Speaking of entropy as "disorder" without applying the appropriate
> > actual definitions used in thermodynamics is invariably misleading.
> > Thermodymically, the hot dense gas of a star is more disordered
> > than the cooler diffuse gas of a cloud, if we are using "disorder"
> > to mean "higher entropy".
>
> Horse manure.
>
> Regards, Charlie wagner
> http://www.charliewagner.com
>
> >
> >
> > Cheers -- Chris
--
Bill
"Let every nation know, whether it wishes us well or ill,
that we shall pay any price, bear any burden, meet any hardship,
support any friend, oppose any foe to assure the survival and
the success of liberty." - President John F. Kennedy, Inaugural Address,
January 20, 1961
Charles Wagner
Bill Hudson wrote:
Total nonsense. That's the story, but unfortunately, it's not true.
> The initial energy
> (Ea) comes from the heat generated as the molecules bump into each
> other. Once the H-burn starts, it is spontaneous, and loses a *lot* of
> heat to the environment. That is an *increase* in entropy.
When stars burn, they lose heat and the low entropy of the star increases as
the heat and other forms of energy radiate off into space. When all the stars
burn out (if that in fact, occurs) then the universe will be at maximum
entropy. No energy will be available for work and all of the heat will be
spread out uniformly throughout the universe. In nature, entropy increases in
all natural processes. But we're talking about the formation of stars. How do
the diffuse gases (high entropy) change into compact stars (low entropy). The
claim is that gravity causes this. But anyone can easily see that this is
impossible. But it's the story passed along from generation to generation and
everyone believes it. I'm here to tell you it's not true. No one can explain
where the original low entropy of the universe came from.
>
>
> from http://www.2ndlaw.com/entropy.html; "...every single time something
> spontaneous happens via energy spreading out
> to the surroundings - like the old example of the hot pan cooling down -
> entropy is +, positive."
>
> > > Like any other spontaneous process,
> > > gravitational collapse involves an increase in entropy.
> >
> > More baloney. It's a decrease in entropy.
> >
> > > The
> > > collapse reduces the potential energy of the cloud,
> >
> > > and increases
> > > its heat energy. This is a conversion of "usable" energy into
> > > heat -- a classic irrevesible (entropy increasing) process.
> >
> > Baloney. If it happens like you say (it doesn't) then it's a conversion
> > of unusable energy into usable energy.
> >
> > >
> > >
> > > In short, Wade is quite correct.
> >
> > Baloney. He's wrong and so are you.
> > You know, it's OK to play with my head, but there are innocents reading
> > this who may believe you.
>
> Why don't you go read http://www.secondlaw.com and
> http://www.2ndlaw.com? I'm no scientist, and I can't do the math, but
> apparently I understand entropy and the SLOT better than you do...
I'm afraid that's not true. Wade is wrong, Chris is wrong, and if you believe
them, then you're wrong too.
Ryan, where are you when I need you?? I feel like Alice in Wonderland!
Regards, Charlie Wagner
http://www.charliewagner.com
>
>
> >
> > >
> > >
John Pieper
wrote:
The definition of usable energy is that which can be converted to
mechanical work. Gravitational potential energy can in principle be
completely converted to mechanical work. Once a cloud of gas has collapsed,
its gravitational potential energy has been mostly converted to heat
instead. The only way to get mechanical work out of a source of heat is to
let the heat flow to a lower temperature, and then Carnot's limit on the
efficiency of work extraction applies: there will always be some minimum
amount of energy "lost" in the process that can not be converted to
work. Therefore the energy of a star is *less* usable that that of the
original gas cloud; therefore, the entropy is greater.
[snip rest]
--
John Pieper |"Politics and religion are obsolete; the time has come
jbp34 |for science and spirituality."--Jawaharlal Nehru
@home |
Bill Hudson
entropy <> "disorder", and since you used Shannon's information theory
the *last* time you got your butt walloped on this issue...
"Another major source of confusion about entropy change as the
result of simply rearranging macro objects comes from information
theory "entropy".(2) Claude E. Shannon's 1948 paper began the
era of quantification of information and in it he adopted the word
"entropy" to name the quantity that his equation defined (2). This
occurred because a friend, the brilliant mathematician John von
Neumann, told him "call it entropy no one knows what entropy
really is, so in a debate you will always have the advantage" (3).
Wryly funny for that moment, Shannon's unwise acquiescence
has produced enormous scientific confusion due to the
increasingly widespread usefulness of his equation and its fertile
mathematical variations in many fields other than communications
(4, 5). Certainly most non-experts hearing of the widely touted
information "entropy" would assume its overlap with
thermodynamic entropy. However, the great success of
information "entropy" has been in areas totally divorced from
experimental chemistry, whose objective macro results are
dependent on the behavior of energetic microparticles.
Nevertheless, many instructors in chemistry have the impression
that information "entropy" is not only relevant to the calculations
and conclusions of thermodynamic entropy but may change them.
This is not true."
- 'Shuffled Cards, Messy Desks, and Disorderly Dorm Rooms - Examples
of Entropy Increase? Nonsense!'; Frank L. Lambert, "Journal of Chemical
Education", October 1999, Vol. 76, No. 10, p. 1385
>
> >
> > Gravitational collapse is complicated and involves some twists but it is
> > spontaneous and overall a positive entropy change.
>
> It is not spontaneous, which is the main reason why certain cosmological theories
> that have the gases contracting under gravity are pure baloney. And it is definitely
> a negative entropy change.
Where does the 'energy' in gravity come from? The system of collapsing
gas forming a star and burning converts potential energy into kinetic
energy, then kinetic energy into heat, which is then used as Ea in the
fusion reaction, which is then spontaneous.
Are you saying that gas clouds do *not* contract due to gravity? Are
you really saying that?
>
> Regards, Charlie Wagner
> http://www.charliewagner.com
>
> >
> >
> > > > In fact, one of the major unsolved problems of cosmology is the problem
> > > > of why the Universe seems to have started out so uniform, since that's
> > > > a state of such low entropy.
> > >
> > > The "major unsolved question of cosmology" is where the low entropy of the
> > > stars came from. If the universe started out so uniform, how did this high
> > > entropy change into the low entropy that we now find in stars.
--
Bob Pease
>
> Whether something is correct or not is independent of the speaker. The
biggest
> moron in the world can say that the earth is round.
>
> Regards, Charlie Wagner
> http://www.charliewagner.com
>
That's true, of course.
It also is
conversely related to the more interesting question..
Is a person with a reputation of uttering falsehoods as trustworthy as a
person with the reputation of uttering truth??
Rhetorical question..
RJP
Charles Wagner
John Pieper wrote:
> On 20 Nov 2001 16:01:39 -0500, Charles Wagner <cha...@charliewagner.com>
> wrote:
>
> >
> >
> >Chris Ho-Stuart wrote:
> >
> >> Charles Wagner <cha...@charliewagner.com> wrote:
> >> > Wade Hines wrote:
> >> >> Charles Wagner wrote:
> >> [snip]
> >> >> > I swore I wasn't going to get involved in this again, but
> >> >> > this is such a glaring error that I must point it out. Perhaps
> >> >> > somewhere down the thread this has happened, but I'm not going
> >> >> > through it all. You have it exactly backwards. The highest
> >> >> > entropy state is the one in which matter is most disorderly.
> >> >> > Entropy is the measure of the degree of disorder. The greater
> >> >> > the disorder, the higher the entropy. An inert cloud of hydrogen
> >> >> > has far more entropy than a star.
> >> >>
> >> >> Nope. The star is hotter. In general, the same thing hotter
> >> >> has more entropy. Gravitational collapse is complicated and
> >> >> involves some twists but it is spontaneous and overall a positive
> >> >> entropy change.
> >> >
> >> > With all due respect, you are absolutely and completely wrong.
> >>
> >> An inert cloud of gas will spontaneously collapse and heat up,
> >> and this can form a star.
> >
> >Baloney.
> >
> >> Like any other spontaneous process,
> >> gravitational collapse involves an increase in entropy.
> >
> >More baloney. It's a decrease in entropy.
> >
> >
> >> The
> >> collapse reduces the potential energy of the cloud,
> >
> >> and increases
> >> its heat energy. This is a conversion of "usable" energy into
> >> heat -- a classic irrevesible (entropy increasing) process.
> >
> >Baloney. If it happens like you say (it doesn't) then it's a conversion
> >of unusable energy into usable energy.
>
> The definition of usable energy is that which can be converted to
> mechanical work. Gravitational potential energy can in principle be
> completely converted to mechanical work. Once a cloud of gas has collapsed,
> its gravitational potential energy has been mostly converted to heat
> instead. The only way to get mechanical work out of a source of heat is to
> let the heat flow to a lower temperature, and then Carnot's limit on the
> efficiency of work extraction applies: there will always be some minimum
> amount of energy "lost" in the process that can not be converted to
> work. Therefore the energy of a star is *less* usable that that of the
> original gas cloud; therefore, the entropy is greater.
Absolutely false. The energy of a star is more usable than it would have been
in the original gas cloud. In the original diffuse gas cloud, with the gas
spread out over many degrees of freedom in an essentially umlimited volume
space, there is no energy available to do work. This is envisioned as the "heat
death" of the universe, when all forms of energy have been converted to heat
and spread out through the universe. Think of a gas in a box. If the gas is
spread throughout the box and the temperature is constant, the gas has maximum
entropy. If we cool the gas and it condenses into a liquid, its entropy
decreases. The same is true of a star. When the gas is spread out, it's at
maximum entropy. If it condenses into stars, it's entropy decreases and the
energy available to do work increases. The heat in a star does not come from
the process of condensation, it's a whole different reaction, nuclear fusion.
I went around to a few websites, including the ones suggested and I was
alarmed and shocked at what people are printing on the internet and passing off
as truth. In newsgroups and personal websites, people are free to write
whatever they like irregardless of it's truth. Innocent people go to these
"sources" and repeat what they see there, thinking that it's correct. This is
an alarming phenomenon. I fear that the internet simply cannot be trusted as a
source of facts unless one is absolutely certain, as in the case of a reputable
university or laboratory, that what they're reading is true. I for one, only
use the books and articles written by reputable scientists that I can usually
trust.
Regards, Charlie Wagner
http://www.charliewagner.com
>
>
Wade Hines
You have to be careful about the water vapor because one actually
needs to specify a pressure as well. As is easily knowable, you
can't have water vapor stable at room T and 1 atmosphere. Even in
a metastable state and 1 atmosphere pressure though, the water vapor
would, I guess here, still have a higher entropy. Such are phase changes.
But we weren't considering a phase change but the more complex issue
of gravitational collapse. Until recently, I misunderstood some of
gravitational collapse respective to entropy. My understanding at
the moment isn't adequate to a proper didactic but I do know that
gravitational collapse is sponteneous and entropically positive.
It isn't necessarily positive if you just focus on the gas though.
One has to include the effect on space itself.
An easier example is a phase separation of oil and water.
The intuitively most disordered state would seem to be with the
oil and water completely mixed but if you shake up your italian
dressing you'll eventually have it separate back out. It's
spontaneous, a positive change in entropy despite common sensical
notions of order/disorder, and less difficult to understand than
gravitational collapse.
>> Gravitational collapse is complicated and involves some twists but it
>> is spontaneous and overall a positive entropy change.
> It is not spontaneous, which is the main reason why certain
> cosmological theories that have the gases contracting under gravity are
> pure baloney. And it is definitely a negative entropy change.
That is certainly not the standard interpretation of physics.
At the same time, what was my conviction about the simple conversion
of potential energy to kinetic energy seems to have been wrong.
Regardless, the issue of "order" and "disorder" and entropy is
that one can't use simple intuition or common sense with great
reliability. The oil/water example is more tractable than gravitational
collapse.
Wade Hines
No. Charles has some misplaced convictions but they generally
involve things that do in fact have roots in a sort of common
sense. He can be reasoned with successfully by someone with
adequate patience and skill though I tend to fall short one
at least one and sometimes two of those. Ed is a different
sort of animal.
Wade Hines
> Charles Wagner <cha...@charliewagner.com> wrote:
>> Wade Hines wrote:
>>> Charles Wagner wrote:
> [snip]
>>> > I swore I wasn't going to get involved in this again, but
>>> > this is such a glaring error that I must point it out. Perhaps
>>> > somewhere down the thread this has happened, but I'm not going
>>> > through it all. You have it exactly backwards. The highest
>>> > entropy state is the one in which matter is most disorderly.
>>> > Entropy is the measure of the degree of disorder. The greater
>>> > the disorder, the higher the entropy. An inert cloud of hydrogen
>>> > has far more entropy than a star.
>>>
>>> Nope. The star is hotter. In general, the same thing hotter
>>> has more entropy. Gravitational collapse is complicated and
>>> involves some twists but it is spontaneous and overall a positive
>>> entropy change.
>>
>> With all due respect, you are absolutely and completely wrong.
>
> An inert cloud of gas will spontaneously collapse and heat up,
> and this can form a star. Like any other spontaneous process,
> gravitational collapse involves an increase in entropy. The
> collapse reduces the potential energy of the cloud, and increases
> its heat energy. This is a conversion of "usable" energy into
> heat -- a classic irrevesible (entropy increasing) process.
>
> In short, Wade is quite correct.
Not to be a pest, but I was sort of incorrect or at least overly
glib. The gas heating up isn't enough. There is this odd feature
which I barely understand involving negative specific heats of
gravitational systems.
As I expect you care, here's some deeper stuff.
http://www.ifa.hawaii.edu/~kaiser/lectures/astro635/notes/notes.pdf
I don't claim to really understand it but expect you might get
more out of it than I do.
Chris Ho-Stuart
which are oversimplified, misleading, or just plain wrong. Myself
included.
Some responses have been, shall we say, "terse", which has not
helped.
I am not actually the best informed contributor here, but I think
I might be able to help clarify the matter by pointing out where
all of us have been making mistakes. If *I* have made further
mistakes in this article, specific corrections are very welcome.
I am tracking a series of comments by Steve Carlip, Charlie Wagner,
Wade Hines, Chris Ho-Stuart (that's me) and finally Bill Hudson.
In each case, I comment on an extract in what I hope is a useful
bit of criticism.
Extract 1: Steve Carlip
-----------------------
From sjca...@ucdavis.edu Wed Nov 21 09:52:48 2001
> Which has more entropy, an ``inert uniform'' cloud of hydrogen or the
> same hydrogen clumped together into stars? The answer is the latter.
> In any system in which gravity is an important force, an ``inert uniform''
> state has *low* entropy compared to a lumpy, uneven state. The highest
> entropy state is typically the one in which the matter is all compacted
> together to form a black hole.
Actually, I think the first sentence here is wrong: the star
does in fact have less entropy than the cloud of gas from which
it was formed. The major increase in entropy during formation of
a star is not due to increased entropy of the star, but to the
radiated energy sent into space during the collapse and heating.
Extract 2: Charlie Wager responding to Steve
--------------------------------------------
From cha...@charliewagner.com Wed Nov 21 09:52:48 2001
> I swore I wasn't going to get involved in this again, but this is
> such a glaring error that I must point it out. Perhaps somewhere
> down the thread this has happened, but I'm not going through it
> all. You have it exactly backwards. The highest entropy state is
> the one in which matter is most disorderly. Entropy is the measure
> of the degree of disorder. The greater the disorder, the higher
> the entropy. An inert cloud of hydrogen has far more entropy than a
> star.
Charlie here is (I think) pretty much correct. The inert cloud does
have more entropy than the corresponding star.
Extract 3: Wade Hines responding to Charlie
-------------------------------------------
From: Wade Hines <wade....@rcn.com>
> Nope. The star is hotter. In general, the same thing hotter has
> more entropy. Gravitational collapse is complicated and involves
> some twists but it is spontaneous and overall a positive entropy change.
Wade's response is off the mark. He is correct that the collapse is
complicated, and spontaneous, and overall involves a positive entropy
change; and he is also correct that adding heat to something will
increase its entropy. However, that star is also compressed and in
a smaller volume, and this actually outweighs the matter of being
hotter, I think. The star is at lower entropy than the diffuse
cloud of gas prior to collapse.
Extract 4: Charlie Wagner responding to Wade
--------------------------------------------
From cha...@charliewagner.com Wed Nov 21 09:52:48 2001
> With all due respect, you are absolutely and completely wrong.
No explanation here for where Wade is wrong: which is a worry
because much of Wade's comment was actually correct. I tried
to give a better description of where Wade was wrong above.
Extract 5: Charlis Wagner giving a more detailed response to Wade
-----------------------------------------------------------------
From cha...@charliewagner.com Wed Nov 21 09:52:49 2001
>> Nope. The star is hotter. In general, the same thing hotter has
>> more entropy.
>
>Water vapor at room temperature still has more entropy than an equal
>amount of water at 372K , despite its lower temperature. Entropy
>measures disorder. Gases are more disorderly than liquids and
>solids and when the universe reaches it's "heat death", when
>no energy will be available to do work, the universe will be at
>maximum entropy.
This is correct.
>> Gravitational collapse is complicated and involves some twists
>> but it is spontaneous and overall a positive entropy change.
>
>It is not spontaneous, which is the main reason why certain
>cosmological theories that have the gases contracting under gravity
>are pure baloney. And it is definitely a negative entropy change.
But this is incorrect. The particular sentence of Wade's to
which Charlie is here responding is one that is entirely correct.
Previously (and correctly) Charlie had observed that a star is at
lower entropy than the cloud of gas, but this is not a refutation
of the observation that gravitational collapse is a spontaneous
process, because the collape involves radiation from the heated
gases generated during collapse: and this more than compensates
for the local decrease in entropy in the gases themselves.
Extract 6. Chris Ho-Stuart responds to Charlie (in extract 4)
-------------------------------------------------------------
From host...@sky.fit.qut.edu.au Wed Nov 21 09:52:49 2001
>> With all due respect, you are absolutely and completely wrong.
>
>An inert cloud of gas will spontaneously collapse and heat up,
>and this can form a star. Like any other spontaneous process,
>gravitational collapse involves an increase in entropy. The
>collapse reduces the potential energy of the cloud, and increases
>its heat energy. This is a conversion of "usable" energy into
>heat -- a classic irrevesible (entropy increasing) process.
My comment here is misleading: because I omit to note that
the increase in entropy is primarily due to radiation (which
in a sense heats up the rest of the universe). Above, I implied
that the heating of the star itself involves a sufficient
increase in entropy to satisfy the second law, and this is wrong.
The star does in fact decrease in entropy, and we need to take
radiation and space into account to find the corresponding
increase in entropy for the entire process.
>In short, Wade is quite correct.
I make the opposite mistake to Charles. Wade is neither "quite
correct" (as I put it) nor "absolutely wrong" (as Charlie put it).
> Speaking of entropy as "disorder" without applying the appropriate
> actual definitions used in thermodynamics is invariably misleading.
> Thermodymically, the hot dense gas of a star is more disordered
> than the cooler diffuse gas of a cloud, if we are using "disorder"
> to mean "higher entropy".
And here I am definitely wrong: repeating Wade's error.
Thermodynamically, the hot and compresses gas of the
star is at lower entropy, not higher.
Extract 7. Chrlier Wagner responds to Chris
-------------------------------------------
From cha...@charliewagner.com Wed Nov 21 09:52:49 2001
>> > With all due respect, you are absolutely and completely wrong.
>>
>> An inert cloud of gas will spontaneously collapse and heat up,
>> and this can form a star.
>
>Baloney.
Not baloney at all. This part of my comment was correct.
>> Like any other spontaneous process,
>> gravitational collapse involves an increase in entropy.
>
>More baloney. It's a decrease in entropy.
This part of my comment was also correct. Just bear in mind that the
increase is only found when you take into account entropy transferred
from the local cloud/star system out into space by radiation.
>> The
>> collapse reduces the potential energy of the cloud,
>> and increases
>> its heat energy. This is a conversion of "usable" energy into
>> heat -- a classic irrevesible (entropy increasing) process.
>
>Baloney. If it happens like you say (it doesn't) then it's a conversion
>of unusable energy into usable energy.
My comments are actually correct, but incomplete. Gravitational
collapse is surprisingly complicated, and the thermodynamics are
not captured by looking only at potential energy and heat.
>> In short, Wade is quite correct.
>
>Baloney. He's wrong and so are you.
>You know, it's OK to play with my head, but there are innocents reading
>this who may believe you.
I'm not playing with your head. I am trying to make a constructive
exchange. There *are* errors being made, by nearly every contributor,
both you and I included. I trust anyone reading this takes no one
writer as gospel.
>> Speaking of entropy as "disorder" without applying the appropriate
>> actual definitions used in thermodynamics is invariably misleading.
>> Thermodymically, the hot dense gas of a star is more disordered
>> than the cooler diffuse gas of a cloud, if we are using "disorder"
>> to mean "higher entropy".
>
>Horse manure.
This is a fair cop. I was indeed incorrect here.
Extract 8. Bill Hudson responds to Charlie
------------------------------------------
From bi...@rmp.com Wed Nov 21 09:52:49 2001
> > > An inert cloud of gas will spontaneously collapse and heat up,
> > > and this can form a star.
> >
> > Baloney.
>
> ??
>
> He is absolutly right. An 'inert' cloud of gas (hydrogen) which
> contains enough mass (as much as a star) will collapse under its own
> gravity, heat up, and begin the fusion process. The initial energy
> (Ea) comes from the heat generated as the molecules bump into each
> other. Once the H-burn starts, it is spontaneous, and loses a *lot* of
> heat to the environment. That is an *increase* in entropy.
Bill here (at last!) manages to make one essential point missed by
all previous writers. He explicitly mentions the loss of heat into the
environment, which is crucial to the thermodynamics of the system.
However, the comment is still misleading. The H-burn, and fusion,
is not criticial; radiation will occur from simple heating, and
this is actually the major way in which entropy is transferred to
the environment during the initial stages of collapse. Even if the
gas never began fusion (due to an unusual element composition,
perhaps) the process would still be spontaeous and would involve
a loss of heat to the environment, sufficient to balance the local
decrease in entropy from compression of the gases.
If I am incorrect in any of this, I would welcome further
correction, as long as it is specific about what is wrong.
Merely stating that collapse is impossible because it
involves a net loss of entropy is not an adequate response;
because I have stated why collapse involves a net gain in
entropy. If I am wrong, a bit more detail, hopefully
quantified, of the changes in entropy in various parts of
the total system, would be more useful to me.
A reference which helped me in this post is an article from
the "Mad Scientist Network"
<http://www.madsci.org/>
an educational site at which professional scientists
will answer questions. In 1999, the question was asked
"how is entropy effected during the formation of a star?"
and the answer by William Wheaton at
<http://128.252.223.112:80/posts/archives/sep99/937295445.As.r.html>
gives a lot of very helpful detail. He provides some calculations,
which demonstrate that the change in volume of gases as they are
compressed constitutes a huge decrease in entropy, which is not
balanced by the local entropy increase due to heating of those
gases. He does not, unfortunately, similarly quantify the entropy
associated with radiation generated during collapse, but he points
out that this is the major entropy sink of the system.
Best wishes all -- Chris
dkomo
>
> Wade Hines <wade....@rcn.com> wrote:
>
> > Steve and Lesa wrote:
>
> >> I have a definition of entropy I got out of Webster's, if anyone is
> >> really interested in the particulars let me know and I will post all
> >> the necessary information to properly cite the source.
>
> >> It was the 3rd. definition. Definitions 1 and 1a dealt with the 2nd Law
> >> of Thermodynamics, the 2nd definition had to do with logarithms and
> >> message frequency and the 3rd was the one that caught my eye:
>
> >> ....3 the degradation of the matter and energy in the universe to an
> >> ultimate state of inert uniformity.
>
> > Eck.
>
> Double eck! This is not only not a definition of entropy, it's flat-out
> wrong as a statement of physics.
>
> same hydrogen clumped together into stars? The answer is the latter.
> In any system in which gravity is an important force, an ``inert uniform''
> state has *low* entropy compared to a lumpy, uneven state.
Actually, the answer is that you're wrong. The entropy of a
collapsing cloud of instellar matter *decreases*, but the 2Lot is not
violated because the overall entropy of the universe increases to
compensate. See the derivation of this result by John Baez at
http://math.ucr.edu/home/baez/entropy.html
This derivation is by someone who knows more about the subject than
anyone on TO. In fact, probably knows more about it than most of the
TO readership put together.
The claims here on TO about the entropy of self-gravitating objects
has an interesting history for me. Back in July I tentatively
expressed an opinion that I thought that:
"Planets, and star clusters, and black holes, and comets are more
structured, occcupy less volume, and are less homogenuous [than the
gas cloud they condensed from]. There was a decrease in entropy in
their formation."
I was then browbeaten for this observation by another TO member, whose
name I won't reveal (but he's in this thread). This member vehemently
asserted that entropy *increases* during star formation.
Ok, not being all that sure, I went along with that. About three
weeks later, I was correcting someone else about the same mistake I
thought I had made, when Jack Sullivan replied with the link to the
Baez page.
And then I replied to Jack's post with:
"LOL! I love it! This is what I initially said way back in another
thread -- that the formation of galaxies and stars *decreases*
entropy, but that there was no violation of the 2LoT because the
entropy of the overall universe increases to compensate. The Baez
page has it all worked out in minute detail.
This whole discussion on TO illustrates the quotation that when it
comes to entropy, hardly anybody knows what they're talking about. I
think some well known physicist said that."
Ok, people, can we now get it straight once and for all about the
entropy of self-gravitating systems? As of right now I'm serving
notice that I will accept no more hand-waving bullshit on this topic.
Chris Ho-Stuart
>> In short, Wade is quite correct.
>
> Not to be a pest, but I was sort of incorrect or at least overly
> glib. The gas heating up isn't enough. There is this odd feature
> which I barely understand involving negative specific heats of
> gravitational systems.
>
> As I expect you care, here's some deeper stuff.
> http://www.ifa.hawaii.edu/~kaiser/lectures/astro635/notes/notes.pdf
Thanks muchly!
Admitting error is never being a pest: it is very helpful
and constructive indeed. I also have made some blunders. I
have just now posted a longer summary attempting to document
some of the various errors made by you, me, Steve Carlip,
and Charlie. I was a bit concerned about pointing out
errors made by some of these folks, and am immensely relieved
to see you have already seen some of the same yourself.
Your reference (a 400 page book in pdf!) looks completely
overwhelming but very interesting. I have relied on a much
simpler one page exposition aimed at advanced school age
students, it seems.
<http://128.252.223.112:80/posts/archives/sep99/937295445.As.q.html>
> I don't claim to really understand it but expect you might get
> more out of it than I do.
>
>> Speaking of entropy as "disorder" without applying the appropriate
>> actual definitions used in thermodynamics is invariably misleading.
>> Thermodymically, the hot dense gas of a star is more disordered
>> than the cooler diffuse gas of a cloud, if we are using "disorder"
>> to mean "higher entropy".
Here, by the way, I was also incorrect.
Except that my first sentence remains true, and a constant
source of difficulty for people who think that thermodynamics
can be followed using simple intuitive notions of order and
disorder.
I am of the view that a much better intuition for "entropy" is
gained by thinking of it not so much as a measure of "disorder",
but as a measure of how evenly distributed energy is throughout
a system. Using this intuition, the second law is seen as a
statement that energy always becomes more dissipated in any
process.
But still: ultimately the full mathematical definitions are
the most reliable guide, and not any intuitive analogue.
Cheers -- Chris
Charles Wagner
Bob Pease wrote:
> Charles Wagner <cha...@charliewagner.com> wrote in message
> news:3BFAC21B...@charliewagner.com...
> >
> > Whether something is correct or not is independent of the speaker. The
> biggest
> > moron in the world can say that the earth is round.
> >
> > Regards, Charlie Wagner
> > http://www.charliewagner.com
> >
>
> That's true, of course.
> It also is
> conversely related to the more interesting question..
>
> Is a person with a reputation of uttering falsehoods as trustworthy as a
> person with the reputation of uttering truth??
>
> Rhetorical question..
Did you have anyone particular in mind?
Regards, Charlie Wagner
http://www.charliewagner.com
>
>
> RJP
Chris Ho-Stuart
[snip]
> The definition of usable energy is that which can be converted to
> mechanical work. Gravitational potential energy can in principle be
> completely converted to mechanical work. Once a cloud of gas has collapsed,
> its gravitational potential energy has been mostly converted to heat
> instead. The only way to get mechanical work out of a source of heat is to
> let the heat flow to a lower temperature, and then Carnot's limit on the
> efficiency of work extraction applies: there will always be some minimum
> amount of energy "lost" in the process that can not be converted to
> work. Therefore the energy of a star is *less* usable that that of the
> original gas cloud; therefore, the entropy is greater.
Actually, the star has less energy than the cloud; and this is
rather more significant. The star also has less entropy than the
gas cloud, and this is compensated for by radiation of the lost energy
out into space, which has the effect of transferring entropy into
the environment of the collapsing cloud. Locally, the cloud/star
system has decreased in energy, and also in entropy. But it is not
an isolated system.
I am fairly confident about this, at present; but would welcome
any further clarifications, if they are specific and/or quantified.
Cheers -- Chris
Charles Wagner
Bill Hudson wrote:
> Charles Wagner wrote:
> >
> > Wade Hines wrote:
> >
> > > Charles Wagner wrote:
> > > >
> > > > Steve Carlip wrote:
> > > >
> > > > > Wade Hines <wade....@rcn.com> wrote:
> > > > >
> > > > > > Steve and Lesa wrote:
> > > > >
> > > > > >> I have a definition of entropy I got out of Webster's, if anyone is
> > > > > >> really interested in the particulars let me know and I will post all
> > > > > >> the necessary information to properly cite the source.
> > > > >
> > > > > >> It was the 3rd. definition. Definitions 1 and 1a dealt with the 2nd Law
> > > > > >> of Thermodynamics, the 2nd definition had to do with logarithms and
> > > > > >> message frequency and the 3rd was the one that caught my eye:
> > > > >
> > > > > >> ....3 the degradation of the matter and energy in the universe to an
> > > > > >> ultimate state of inert uniformity.
> > > > >
> > > > > > Eck.
> > > > >
> > > > > Double eck! This is not only not a definition of entropy, it's flat-out
> > > > > wrong as a statement of physics.
> > > > >
> > > > > Which has more entropy, an ``inert uniform'' cloud of hydrogen or the
> > > > > same hydrogen clumped together into stars? The answer is the latter.
> > > > > In any system in which gravity is an important force, an ``inert uniform''
> > > > > state has *low* entropy compared to a lumpy, uneven state. The highest
> > > > > entropy state is typically the one in which the matter is all compacted
> > > > > together to form a black hole.
> > > >
> > > > I swore I wasn't going to get involved in this again, but this is such a
> > > > glaring error that I must point it out. Perhaps somewhere down the thread this
> > > > has happened, but I'm not going through it all. You have it exactly backwards.
> > > > The highest entropy state is the one in which matter is most disorderly.
> > > > Entropy is the measure of the degree of disorder. The greater the disorder, the
> > > > higher the entropy. An inert cloud of hydrogen has far more entropy than a
> > > > star.
> > >
> > > Nope. The star is hotter. In general, the same thing hotter has more entropy.
> >
> > Water vapor at room temperature still has more entropy than an equal amount of water
> > at 372K , despite its lower temperature. Entropy measures disorder. Gases are more
> > disorderly than liquids and solids and when the universe reaches it's "heat death",
> > when no energy will be available to do work, the universe will be at maximum entropy.
>
> entropy <> "disorder", and since you used Shannon's information theory
> the *last* time you got your butt walloped on this issue...
In your dreams...
I prefer Feynman's definition.
>
>
> >
> > >
> > > Gravitational collapse is complicated and involves some twists but it is
> > > spontaneous and overall a positive entropy change.
> >
> > It is not spontaneous, which is the main reason why certain cosmological theories
> > that have the gases contracting under gravity are pure baloney. And it is definitely
> > a negative entropy change.
>
> Where does the 'energy' in gravity come from? The system of collapsing
> gas forming a star and burning converts potential energy into kinetic
> energy, then kinetic energy into heat, which is then used as Ea in the
> fusion reaction, which is then spontaneous.
No one knows where the "energy" of gravity comes from. An object further from a
gravitational field has more potential energy with respect to that field than an object
that is closer. Standing on the ground, if the ground is used as the reference point, one
has zero gravitational potential energy. Likewise, as gases condense into stars, (if indeed
that happens) then as the gravitational potential energy decreases as the star forms. Of
course, there's no reason whatsoever why a mass of diffuse gas should suddenly begin to
condense and form into stars. It's like saying that the gas in a box suddenly begins to
condense under it's own gravity into a smaller volume. It's ridiculous. Insofar as fusion
is concerned, there's no explanation as to why this condensing gas should suddenly begin to
undergo a fusion reaction. Can the temperature get hot enough? These are troubling
questions.
The nuclear fusion is an entirely different process. Potential energy is present in the
nuclei of the atoms and this energy is released as mass changes into energy. The heat
produced when the star contracts is the result of a different mechanism.
>
>
> Are you saying that gas clouds do *not* contract due to gravity? Are
> you really saying that?
Yep, that's exactly what I'm saying. Kind of blows your mind, huh?
I'm telling you that the basic premises that you hold true and dear are assumptions that in
most liklihood have little or no validity or meaning in the real world.
Regards, Charlie Wagner
http://www.charliewagner.com
>
>
> >
> > Regards, Charlie Wagner
> > http://www.charliewagner.com
> >
> > >
> > >
> > > > > In fact, one of the major unsolved problems of cosmology is the problem
> > > > > of why the Universe seems to have started out so uniform, since that's
> > > > > a state of such low entropy.
> > > >
> > > > The "major unsolved question of cosmology" is where the low entropy of the
> > > > stars came from. If the universe started out so uniform, how did this high
> > > > entropy change into the low entropy that we now find in stars.
>
Wade Hines
> Wade Hines <wade....@rcn.com> wrote:
>> Chris Ho-Stuart <host...@sky.fit.qut.edu.au> allegedly typed
> [snip]
>>> In short, Wade is quite correct.
>>
>> Not to be a pest, but I was sort of incorrect or at least overly
>> glib. The gas heating up isn't enough. There is this odd feature
>> which I barely understand involving negative specific heats of
>> gravitational systems.
>>
>> As I expect you care, here's some deeper stuff.
>> http://www.ifa.hawaii.edu/~kaiser/lectures/astro635/notes/notes.pdf
>
> Thanks muchly!
>
> Admitting error is never being a pest: it is very helpful
> and constructive indeed. I also have made some blunders. I
> have just now posted a longer summary attempting to document
> some of the various errors made by you, me, Steve Carlip,
> and Charlie. I was a bit concerned about pointing out
> errors made by some of these folks, and am immensely relieved
> to see you have already seen some of the same yourself.
>
> Your reference (a 400 page book in pdf!) looks completely
> overwhelming but very interesting.
It's well outlined so you can go to the parts that matter.
>I have relied on a much
> simpler one page exposition aimed at advanced school age
> students, it seems.
Then it's probably more my speed.
> <http://128.252.223.112:80/posts/archives/sep99/937295445.As.q.html>
>
John Pieper
wrote:
>
>
>John Pieper wrote:
>
>> On 20 Nov 2001 16:01:39 -0500, Charles Wagner <cha...@charliewagner.com>
>> wrote:
>>
>> >
>> >
>> >Chris Ho-Stuart wrote:
[snip to the point]
That is not what "degrees of freedom" means. A hydrogen atom has the same
three degrees of freedom--one for each space dimension through which it can
move--whether it happens to be in a star or a diffuse gas cloud.
>space, there is no energy available to do work.
Have you never heard of gravity? Gravity is a conservative force--one that
can be described by a potential function. A mass in a gravitational
potential field has potential energy associated with its position relative
to the masses that create the field. If a mass is free to move in a
potential, it will move in the direction of decreasing potential energy,
picking up kinetic energy so that the sum of potential and kinetic energy
is constant. In a collapsing gas cloud, the kinetic energies of the atoms
are associated with motion in a predictable direction--the direction of
the center of mass of the cloud. I could, in principle, put something like
a springy ball (negligible mass) at the center of mass and have it
compressed by the collapsing cloud. This is work.
This is also very basic physics.
>This is envisioned as the "heat
>death" of the universe, when all forms of energy have been converted to heat
>and spread out through the universe.
It can hardly be heat death if the energy of the gas has not even been
converted to heat yet.
>Think of a gas in a box. If the gas is
>spread throughout the box and the temperature is constant, the gas has maximum
>entropy. If we cool the gas and it condenses into a liquid, its entropy
>decreases.
Yes, because the liquid state has a lower specific entropy than the gas
state.
>The same is true of a star. When the gas is spread out, it's at
>maximum entropy. If it condenses into stars, it's entropy decreases and the
>energy available to do work increases.
The gas does *not* condense into a liquid state, though. This is where your
error is. The temperature is far too high for it to become a liquid, even
at the high pressures inside a star. The gas does not cool down, it heats
up! As a cloud begins to collapse and becomes denser, the atoms collide and
their velocities become somewhat randomized in direction. The random
component of the velocity distribution is heat.
>The heat in a star does not come from
>the process of condensation, it's a whole different reaction, nuclear fusion.
How did fusion get started in the first place? It requires extremely high
temperatures to give nuclei enough kinetic energy to overcome the
electrostatic repulsion of other nuclei and get close enough to them for
the attractive but very short range nuclear force to take over. The gas
had to be hot already for fusion to begin.
Once fusion does begin, it converts another form of potential energy--
associated with the nuclear force--to heat. Another thermodynamic downgrade
producing a decrease in usability of energy, and an increase in entropy.
> I went around to a few websites, including the ones suggested and I was
>alarmed and shocked at what people are printing on the internet and passing off
>as truth. In newsgroups and personal websites, people are free to write
>whatever they like irregardless of it's truth. Innocent people go to these
>"sources" and repeat what they see there, thinking that it's correct. This is
>an alarming phenomenon. I fear that the internet simply cannot be trusted as a
>source of facts unless one is absolutely certain, as in the case of a reputable
>university or laboratory, that what they're reading is true. I for one, only
>use the books and articles written by reputable scientists that I can usually
>trust.
Got a sporting proposition for you, Charles. What say you check out some of
those books and articles by reputable scientists and see what they have to
say on this topic. Report back with your references and we'll compare
notes.
Charles Wagner
Wade Hines wrote:
> Charles Wagner <cha...@charliewagner.com> allegedly typed
> You have to be careful about the water vapor because one actually
> needs to specify a pressure as well. As is easily knowable, you
> can't have water vapor stable at room T and 1 atmosphere. Even in
> a metastable state and 1 atmosphere pressure though, the water vapor
> would, I guess here, still have a higher entropy. Such are phase changes.
>
> But we weren't considering a phase change but the more complex issue
> of gravitational collapse. Until recently, I misunderstood some of
> gravitational collapse respective to entropy. My understanding at
> the moment isn't adequate to a proper didactic but I do know that
> gravitational collapse is sponteneous and entropically positive.
> It isn't necessarily positive if you just focus on the gas though.
> One has to include the effect on space itself.
>
> An easier example is a phase separation of oil and water.
>
> The intuitively most disordered state would seem to be with the
> oil and water completely mixed but if you shake up your italian
> dressing you'll eventually have it separate back out. It's
> spontaneous, a positive change in entropy despite common sensical
> notions of order/disorder, and less difficult to understand than
> gravitational collapse.
We measure disorder by the number of ways that the "insides" of a system can
be arranged and still look the same from the outside. Take a box with 2
gases. How many ways can you arrange the molecules so that all of the one
kind are on the left side and all of the other kind are on the right side?
Now think about how many ways you can arrange the molecules with no
restrictions on their placement. Clearly, the latter case presents more
options. The logarithm of that number is the entropy. In the separated case,
(as in your oil and vinegar example) the number of ways is less, and
therefore the entropy is less. Despite the fact that they separate out by
density, that's not what we care about. The mixed state has lower entropy.
>
>
> >> Gravitational collapse is complicated and involves some twists but it
> >> is spontaneous and overall a positive entropy change.
>
> > It is not spontaneous, which is the main reason why certain
> > cosmological theories that have the gases contracting under gravity are
> > pure baloney. And it is definitely a negative entropy change.
>
> That is certainly not the standard interpretation of physics.
Standard interpretations are not always correct.
>
> At the same time, what was my conviction about the simple conversion
> of potential energy to kinetic energy seems to have been wrong.
> Regardless, the issue of "order" and "disorder" and entropy is
> that one can't use simple intuition or common sense with great
> reliability. The oil/water example is more tractable than gravitational
> collapse.
In the oil and water example, your intuition is perfectly correct. But I will
agree that often we can be mislead by a false idea of what "order" is.
Feynman's definition clears it up nicely.
Charles Wagner
Chris Ho-Stuart wrote:
> Almost every contributor to this thread so far has made statements
> which are oversimplified, misleading, or just plain wrong. Myself
> included.
>
> Some responses have been, shall we say, "terse", which has not
> helped.
>
> I am not actually the best informed contributor here, but I think
> I might be able to help clarify the matter by pointing out where
> all of us have been making mistakes. If *I* have made further
> mistakes in this article, specific corrections are very welcome.
>
> I am tracking a series of comments by Steve Carlip, Charlie Wagner,
> Wade Hines, Chris Ho-Stuart (that's me) and finally Bill Hudson.
> In each case, I comment on an extract in what I hope is a useful
> bit of criticism.
>
> Extract 1: Steve Carlip
> -----------------------
>
> From sjca...@ucdavis.edu Wed Nov 21 09:52:48 2001
> > Which has more entropy, an ``inert uniform'' cloud of hydrogen or the
> > same hydrogen clumped together into stars? The answer is the latter.
> > In any system in which gravity is an important force, an ``inert uniform''
> > state has *low* entropy compared to a lumpy, uneven state. The highest
> > entropy state is typically the one in which the matter is all compacted
> > together to form a black hole.
>
> Actually, I think the first sentence here is wrong: the star
> does in fact have less entropy than the cloud of gas from which
> it was formed. The major increase in entropy during formation of
> a star is not due to increased entropy of the star, but to the
> radiated energy sent into space during the collapse and heating.
>
> Extract 2: Charlie Wager responding to Steve
> --------------------------------------------
>
> From cha...@charliewagner.com Wed Nov 21 09:52:48 2001
> > I swore I wasn't going to get involved in this again, but this is
> > such a glaring error that I must point it out. Perhaps somewhere
> > down the thread this has happened, but I'm not going through it
> > all. You have it exactly backwards. The highest entropy state is
> > the one in which matter is most disorderly. Entropy is the measure
> > of the degree of disorder. The greater the disorder, the higher
> > the entropy. An inert cloud of hydrogen has far more entropy than a
> > star.
>
> Charlie here is (I think) pretty much correct. The inert cloud does
> have more entropy than the corresponding star.
>
> Extract 3: Wade Hines responding to Charlie
> -------------------------------------------
>
> From: Wade Hines <wade....@rcn.com>
> > Nope. The star is hotter. In general, the same thing hotter has
> > more entropy. Gravitational collapse is complicated and involves
> > some twists but it is spontaneous and overall a positive entropy change.
>
> Wade's response is off the mark. He is correct that the collapse is
> complicated, and spontaneous, and overall involves a positive entropy
> change; and he is also correct that adding heat to something will
> increase its entropy. However, that star is also compressed and in
> a smaller volume, and this actually outweighs the matter of being
> hotter, I think. The star is at lower entropy than the diffuse
> cloud of gas prior to collapse.
>
> Extract 4: Charlie Wagner responding to Wade
> --------------------------------------------
>
> From cha...@charliewagner.com Wed Nov 21 09:52:48 2001
> > With all due respect, you are absolutely and completely wrong.
>
> No explanation here for where Wade is wrong: which is a worry
> because much of Wade's comment was actually correct. I tried
> to give a better description of where Wade was wrong above.
>
> Extract 5: Charlis Wagner giving a more detailed response to Wade
> -----------------------------------------------------------------
>
> From cha...@charliewagner.com Wed Nov 21 09:52:49 2001
> >> Nope. The star is hotter. In general, the same thing hotter has
> >> more entropy.
> >
> >Water vapor at room temperature still has more entropy than an equal
> >amount of water at 372K , despite its lower temperature. Entropy
> >measures disorder. Gases are more disorderly than liquids and
> >solids and when the universe reaches it's "heat death", when
> >no energy will be available to do work, the universe will be at
> >maximum entropy.
>
> This is correct.
>
> >> Gravitational collapse is complicated and involves some twists
> >> but it is spontaneous and overall a positive entropy change.
> >
> >It is not spontaneous, which is the main reason why certain
> >cosmological theories that have the gases contracting under gravity
> >are pure baloney. And it is definitely a negative entropy change.
>
> But this is incorrect. The particular sentence of Wade's to
> which Charlie is here responding is one that is entirely correct.
> Previously (and correctly) Charlie had observed that a star is at
> lower entropy than the cloud of gas, but this is not a refutation
> of the observation that gravitational collapse is a spontaneous
> process, because the collape involves radiation from the heated
> gases generated during collapse: and this more than compensates
> for the local decrease in entropy in the gases themselves.
>
> Extract 6. Chris Ho-Stuart responds to Charlie (in extract 4)
> -------------------------------------------------------------
>
> From host...@sky.fit.qut.edu.au Wed Nov 21 09:52:49 2001
> >> With all due respect, you are absolutely and completely wrong.
> >
> >An inert cloud of gas will spontaneously collapse and heat up,
> >and this can form a star. Like any other spontaneous process,
> >gravitational collapse involves an increase in entropy. The
> >collapse reduces the potential energy of the cloud, and increases
> >its heat energy. This is a conversion of "usable" energy into
> >heat -- a classic irrevesible (entropy increasing) process.
>
> My comment here is misleading: because I omit to note that
> the increase in entropy is primarily due to radiation (which
> in a sense heats up the rest of the universe). Above, I implied
> that the heating of the star itself involves a sufficient
> increase in entropy to satisfy the second law, and this is wrong.
> The star does in fact decrease in entropy, and we need to take
> radiation and space into account to find the corresponding
> increase in entropy for the entire process.
>
> >In short, Wade is quite correct.
>
> I make the opposite mistake to Charles. Wade is neither "quite
> correct" (as I put it) nor "absolutely wrong" (as Charlie put it).
>
> > Speaking of entropy as "disorder" without applying the appropriate
> > actual definitions used in thermodynamics is invariably misleading.
> > Thermodymically, the hot dense gas of a star is more disordered
> > than the cooler diffuse gas of a cloud, if we are using "disorder"
> > to mean "higher entropy".
>
> And here I am definitely wrong: repeating Wade's error.
> Thermodynamically, the hot and compresses gas of the
> star is at lower entropy, not higher.
>
> Extract 7. Chrlier Wagner responds to Chris
> -------------------------------------------
>
> From cha...@charliewagner.com Wed Nov 21 09:52:49 2001
> >> > With all due respect, you are absolutely and completely wrong.
> >>
> >> An inert cloud of gas will spontaneously collapse and heat up,
> >> and this can form a star.
> >
> >Baloney.
>
> Not baloney at all. This part of my comment was correct.
>
> >> Like any other spontaneous process,
> >> gravitational collapse involves an increase in entropy.
> >
> >More baloney. It's a decrease in entropy.
>
> This part of my comment was also correct. Just bear in mind that the
> increase is only found when you take into account entropy transferred
> from the local cloud/star system out into space by radiation.
>
> >> The
> >> collapse reduces the potential energy of the cloud,
> >> and increases
> >> its heat energy. This is a conversion of "usable" energy into
> >> heat -- a classic irrevesible (entropy increasing) process.
> >
> >Baloney. If it happens like you say (it doesn't) then it's a conversion
> >of unusable energy into usable energy.
>
> My comments are actually correct, but incomplete. Gravitational
> collapse is surprisingly complicated, and the thermodynamics are
> not captured by looking only at potential energy and heat.
>
> >> In short, Wade is quite correct.
> >
> >Baloney. He's wrong and so are you.
> >You know, it's OK to play with my head, but there are innocents reading
> >this who may believe you.
>
> I'm not playing with your head. I am trying to make a constructive
> exchange. There *are* errors being made, by nearly every contributor,
> both you and I included. I trust anyone reading this takes no one
> writer as gospel.
>
> >> Speaking of entropy as "disorder" without applying the appropriate
> >> actual definitions used in thermodynamics is invariably misleading.
> >> Thermodymically, the hot dense gas of a star is more disordered
> >> than the cooler diffuse gas of a cloud, if we are using "disorder"
> >> to mean "higher entropy".
> >
> >Horse manure.
>
> This is a fair cop. I was indeed incorrect here.
>
> Extract 8. Bill Hudson responds to Charlie
> ------------------------------------------
>
> From bi...@rmp.com Wed Nov 21 09:52:49 2001
> > > > An inert cloud of gas will spontaneously collapse and heat up,
> > > > and this can form a star.
> > >
> > > Baloney.
> >
Thank you for the very fair and even-handed analysis. I will add that it was
presumptuopus of me to declare that stars cannot form by gravitational force
acting on a large mass of diffuse gas.
Bob Pease
dkomo <dkomo...@cris.com> wrote in message
news:3BFAFF4A...@cris.com...
> This whole discussion on TO illustrates the quotation that when it
> comes to entropy, hardly anybody knows what they're talking about. I
> think some well known physicist said that."
>
> Ok, people, can we now get it straight once and for all about the
> entropy of self-gravitating systems? As of right now I'm serving
> notice that I will accept no more hand-waving bullshit on this topic.
>
>
> --dk...@cris.com
Thank you for linking to John's page.
I have only the most basic preparation in this subject ( Graduate credits in
Astrophysics, including Intro to Astrophysics, Celestial dynamics, ( Special
student Status, Dept of Astrophysics, University of Colorado, 1960..Not any
mail order joint, this..) yet I don't care to postulate bullshit by
conjecture or memory from 40 years ago.
I too, tire of High School conjecture on subjects which have already been
studied to exhaustion
Chris Ho-Stuart
[snip]
> Thank you for the very fair and even-handed analysis. I will add that it was
> presumptuopus of me to declare that stars cannot form by gravitational force
> acting on a large mass of diffuse gas.
No problem.
By the way, you may be interested to read further on the subject
from a mutual hero: Richard Feynman. I believe his lectures
published as "The Character of Physical Law" discuss various
aspects of (Newtonian) gravity, including the collapse of a
diffuse cloud to a star.
He is more famous scientifically for his interest in quantum
gravity, an as yet incomplete theory of gravitation needed to
show what goes on after a collapse to a singularity. His
extremely difficult and technical "Feynman Lectures on Gravitation"
goes into this subject.
Best wishes -- Chris
Bob Pease
Chris Ho-Stuart <host...@sky.fit.qut.edu.au> wrote in message
news:3bfa...@news.qut.edu.au...
> Wade Hines <wade....@rcn.com> wrote:
> > Chris Ho-Stuart <host...@sky.fit.qut.edu.au> allegedly typed
> [snip]
> >> In short, Wade is quite correct.
> >
> > Not to be a pest, but I was sort of incorrect or at least overly
> > glib. The gas heating up isn't enough. There is this odd feature
> > which I barely understand involving negative specific heats of
> > gravitational systems.
> >
> > As I expect you care, here's some deeper stuff.
> > http://www.ifa.hawaii.edu/~kaiser/lectures/astro635/notes/notes.pdf
>
> Thanks muchly!
>
>
> overwhelming but very interesting. I have relied on a much
> simpler one page exposition aimed at advanced school age
> students, it seems.
> <http://128.252.223.112:80/posts/archives/sep99/937295445.As.q.html>
I downloaded the book, and intend to have a little fun with it ( precious
little, as I don't have time or inclination to re-sharpen my skills from
Grad School daze!)
Thanks also for the Mad Sci link.
The best thing about TO next to the pun cascades is the exposure to sources
like this.
RJ Pease
Bob Pease
Actually, Kent Hovind comes to mind.
If you are asking about yourself. I don't have enough information about your
writings to make any such ominous comparisons.
good luck
RJP
Buckler
wrote:
>Buckler,
>
>Thanks for the reply. I appreciate your kind words, and let me say that
>mostly my experience has been a pleasant one, regarding this forum. While I
>am perhaps misunderstood by a few people, mostly I have received not only
>excellent information, but have been directed to outside sources that I have
>found most helpful.
>
>Thanks
>
>Steve
And thank YOU. I don't claim to be anything like the sort of experts
in the field you'll meet here, but if I can help you at all, I'd like
to. Just listen to the experts first (Wilkins, to begin with).
Cheers,
Buckler
John Pieper
<host...@sky.fit.qut.edu.au> wrote:
OK, this makes sense. I neglected the radiation in my treatment. Have
to consider system plus environment, as I said myself a few posts
up in this thread (I believe).
Wish I had the time to be as thorough and rigorous as you and many
of the regulars are; unfortunately, since I don't get paid to do this
stuff any more...
Thanks for the correction.
Wade Hines
<<< snip >>>
> No one knows where the "energy" of gravity comes from. An object
> further from a gravitational field has more potential energy with
> respect to that field than an object that is closer. Standing on the
> ground, if the ground is used as the reference point, one has zero
> gravitational potential energy. Likewise, as gases condense into stars,
> (if indeed that happens) then as the gravitational potential energy
> decreases as the star forms. Of course, there's no reason whatsoever
> why a mass of diffuse gas should suddenly begin to condense and form
> into stars. It's like saying that the gas in a box suddenly begins to
> condense under it's own gravity into a smaller volume. It's ridiculous.
Unless you've got something more sophisticated to say, I think we
can trivially refute your intuition here. Consider our own atmosphere.
Simplify this to a very tall column. Now if you take a small section
you have a familiar example from an education in chemistry where
we teach that a gas expands to fill a volume. We use this in describing
entropy and I presume you and others are familiar with descriptions
of how there are more ways to have the gas evenly distributed between
the top half and the bottom half of our cutout of this gas column
than there are to have an excess in the bottom half.
I want to avoid the math right now but if we wanted to we could look
at the difference in potential energy of gas in the top half of some
cutout section of our column and the bottom half. If that cutout
exists in some classroom we can show that the potential energy
difference, though real, is very small compared with thermal energy.
Still, if we look far enough up that column we eventually find
there is a difference in pressure. If the cutout is 2 miles high
we find that there are more gas molecules in the bottom half than
in the top half despite our elementary lesson in entropy. We can
show if needed that the potential energy differences in a slice
high up account for the decrease in pressure. Now if we get extra
real we have to deal with meteorological fluxuations like pressure
waves and fronts but I think we can avoid that.
Now I wonder if you want to reply to the observation that there
is a pressure gradient moving upwards into the atmosphere. This
is counterintuitive to trivialized notions of entropy and gas
expanding to fill a void. If those trivialized notions hold we
wouldn't have an atmosphere after all. So where is the extra
bits you must be thinking of when you say what you do given that
our atmosphere seems to contradict at least my reading of your
claims.
> Insofar as fusion is concerned, there's no explanation as to why this
> condensing gas should suddenly begin to undergo a fusion reaction. Can
> the temperature get hot enough? These are troubling questions.
The fusion bit is a red herring as the claims of gravitational collapse
would still be there for a system that only reached a jupiter sized
"star" that lacks the mass to ignite.
> The nuclear fusion is an entirely different process. Potential
> energy is present in the
> nuclei of the atoms and this energy is released as mass changes into
> energy. The heat produced when the star contracts is the result of a
> different mechanism.
No comment.
Wade Hines
> Wade Hines wrote:
>
>> Charles Wagner <cha...@charliewagner.com> allegedly typed
>>
>> An easier example is a phase separation of oil and water.
>>
>> The intuitively most disordered state would seem to be with the
>> oil and water completely mixed but if you shake up your italian
>> dressing you'll eventually have it separate back out. It's
>> spontaneous, a positive change in entropy despite common sensical
>> notions of order/disorder, and less difficult to understand than
>> gravitational collapse.
Measuring is good. You strongly define what is measured here and
that's a generally correct defintion. My objections are to
the transition of using more commonplace notions of "disorder"
that don't necessarily map to the numbers of thermally connected
states.
> We measure disorder by the number of ways that the "insides" of a
> system can be arranged and still look the same from the outside. Take
> a box with 2 gases. How many ways can you arrange the molecules so that
> all of the one kind are on the left side and all of the other kind are
> on the right side? Now think about how many ways you can arrange the
> molecules with no restrictions on their placement. Clearly, the latter
> case presents more options. The logarithm of that number is the
> entropy.
Close. The boltzmann constant is not an insignificant factor.
> In the separated case, (as in your oil and vinegar example)
> the number of ways is less, and therefore the entropy is less. Despite
> the fact that they separate out by density, that's not what we care
> about. The mixed state has lower entropy.
It isn't density. We can get layers that differ between two liquids
with very similar densities. The oil and water example drives off
reducing the contacts between water and oil. Water has more ways
to form a hydrogen bond network with water than it has oil. That's
oversimplifying to some degree but it mates with your understanding
of miscible gases so I expect you'll easily see its truth. There
are simple more ways to arrange the water (in a similarly low
internal energy configuration with lots of hydrogen bonds formed)
if the water and oil are separated. Density matters very little
to this process under Earth gravity. You can change these equilibria
of partially miscible solutions by centrifugation even to the
extent of creating density gradients of otherwise homogenious
solutions. Familar examples are sucrose gradients and Cs gradients.
Bill Hudson
>
> Bill Hudson wrote:
>
> > Charles Wagner wrote:
> > >
> > > > [snip]
> > > > >> > I swore I wasn't going to get involved in this again, but
> > > > >> > this is such a glaring error that I must point it out. Perhaps
> > > > >> > somewhere down the thread this has happened, but I'm not going
> > > > >> > through it all. You have it exactly backwards. The highest
> > > > >> > entropy state is the one in which matter is most disorderly.
> > > > >> > Entropy is the measure of the degree of disorder. The greater
> > > > >> > the disorder, the higher the entropy. An inert cloud of hydrogen
> > > > >> > has far more entropy than a star.
> > > > >>
> > > > >> has more entropy. Gravitational collapse is complicated and
> > > > >> involves some twists but it is spontaneous and overall a positive
> > > > >> entropy change.
> > > > >
> > > >
> > > > An inert cloud of gas will spontaneously collapse and heat up,
> > > > and this can form a star.
> > >
> > > Baloney.
> >
> >
> > He is absolutly right. An 'inert' cloud of gas (hydrogen) which
> > contains enough mass (as much as a star) will collapse under its own
> > gravity, heat up, and begin the fusion process.
>
>
> > The initial energy
> > (Ea) comes from the heat generated as the molecules bump into each
> > other. Once the H-burn starts, it is spontaneous, and loses a *lot* of
> > heat to the environment. That is an *increase* in entropy.
>
> the heat and other forms of energy radiate off into space. When all the stars
> burn out (if that in fact, occurs) then the universe will be at maximum
> entropy. No energy will be available for work and all of the heat will be
> spread out uniformly throughout the universe. In nature, entropy increases in
> all natural processes. But we're talking about the formation of stars. How do
> the diffuse gases (high entropy) change into compact stars (low entropy). The
> claim is that gravity causes this. But anyone can easily see that this is
> impossible.
If 'anyone can easily see it is impossible' perhaps you can explain
*why* it is impossible; other than your mixed-up notions of entropy and
disorder. You must not only consider the system, but the surroundings.
You're neglecting the surroundings.
Do you deny gas has mass? Do you deny gravity exists? What mechanism
would prevent the collapse of a gas cloud given no other forces
present?
>... But it's the story passed along from generation to generation and
> everyone believes it. I'm here to tell you it's not true. No one can explain
> where the original low entropy of the universe came from.
>
> >
> >
> > from http://www.2ndlaw.com/entropy.html; "...every single time something
> > spontaneous happens via energy spreading out
> > to the surroundings - like the old example of the hot pan cooling down -
> > entropy is +, positive."
> >
> > > > Like any other spontaneous process,
> > > > gravitational collapse involves an increase in entropy.
> > >
> > > More baloney. It's a decrease in entropy.
> > >
> > > > The
> > > > collapse reduces the potential energy of the cloud,
> > >
> > > > and increases
> > > > its heat energy. This is a conversion of "usable" energy into
> > > > heat -- a classic irrevesible (entropy increasing) process.
> > >
> > > Baloney. If it happens like you say (it doesn't) then it's a conversion
> > > of unusable energy into usable energy.
> > >
> > > >
> > > >
> > > > In short, Wade is quite correct.
> > >
> > > Baloney. He's wrong and so are you.
> > > You know, it's OK to play with my head, but there are innocents reading
> > > this who may believe you.
> >
> > Why don't you go read http://www.secondlaw.com and
> > http://www.2ndlaw.com? I'm no scientist, and I can't do the math, but
> > apparently I understand entropy and the SLOT better than you do...
>
> I'm afraid that's not true. Wade is wrong, Chris is wrong, and if you believe
> them, then you're wrong too.
> Ryan, where are you when I need you?? I feel like Alice in Wonderland!
>
> Regards, Charlie Wagner
> http://www.charliewagner.com
>
> >
> >
> > >
> > > >
> > > >
> > > > Speaking of entropy as "disorder" without applying the appropriate
> > > > actual definitions used in thermodynamics is invariably misleading.
> > > > Thermodymically, the hot dense gas of a star is more disordered
> > > > than the cooler diffuse gas of a cloud, if we are using "disorder"
> > > > to mean "higher entropy".
> > >
> > > Horse manure.
> > >
> > > Regards, Charlie wagner
> > > http://www.charliewagner.com
> > >
> > > >
> > > >
> > > > Cheers -- Chris
Bill Hudson
>
[snipped other commentary]
> Extract 8. Bill Hudson responds to Charlie
> ------------------------------------------
>
> From bi...@rmp.com Wed Nov 21 09:52:49 2001
> > > > An inert cloud of gas will spontaneously collapse and heat up,
> > > > and this can form a star.
> > >
> > > Baloney.
> >
> > ??
> >
> > He is absolutly right. An 'inert' cloud of gas (hydrogen) which
> > contains enough mass (as much as a star) will collapse under its own
> > gravity, heat up, and begin the fusion process. The initial energy
> > (Ea) comes from the heat generated as the molecules bump into each
> > other. Once the H-burn starts, it is spontaneous, and loses a *lot* of
> > heat to the environment. That is an *increase* in entropy.
>
> Bill here (at last!) manages to make one essential point missed by
> all previous writers. He explicitly mentions the loss of heat into the
> environment, which is crucial to the thermodynamics of the system.
>
In the words of the writer of <http://www.2ndlaw.com>; "System plus
surroundings. System plus surroundings. Never forget to look at both."
He makes the point clear; it is impossible to talk about the 'entropy'
of a system without also examining the surroundings. If the system
loses energy to the surroundings, it has a positive entropy. If a
system receives energy from the surroundings, it has a negative
entropy. If the energy inflow - energy outflow is zero, then the system
is in equilibrium.
Charlie's mistake is that he is just looking at the 'entropy' of the gas
cloud compared to the 'entropy' of the star, and ignoring the
surroundings. You can't measure entropy without measuring the energy
flow across the system boundary, which is why 'order' and 'disorder'
don't cut it as analogies.
> However, the comment is still misleading. The H-burn, and fusion,
> is not criticial; radiation will occur from simple heating, and
> this is actually the major way in which entropy is transferred to
> the environment during the initial stages of collapse. Even if the
> gas never began fusion (due to an unusual element composition,
> perhaps) the process would still be spontaeous and would involve
> a loss of heat to the environment, sufficient to balance the local
> decrease in entropy from compression of the gases.
Yes, you are correct, of course; The way I stated it implies that the
fusion reaction is critical to the transfer of energy, which is
incorrect. The fusion reaction is unnecessary to make the system (a
collapsing gas cloud) spontaneous and have positive entropy. Gas clouds
that are not massive enough, or don't contain the right elements, form
other structures, such as gas giants. I seem to recall that Jupiter
radiates more heat into space than it receives from the Sun.
To pick a nit, the discussion was about the formation of a star, which
is why I had the fusion reaction in there.
Thanks for the links, Chris!
Derek Stevenson
> I'm afraid that's not true. Wade is wrong, Chris is wrong, and if you
believe
> them, then you're wrong too.
> Ryan, where are you when I need you?? I feel like Alice in Wonderland!
You find yourself in a universe that behaves in a fashion at odds from the
way you think it ought to behave?
We've noticed.
Derek Stevenson
news:3bfafb6b....@news1.elmhst1.il.home.com...
> > I went around to a few websites, including the ones suggested and I
was
> >alarmed and shocked at what people are printing
"printing"?
> >on the internet and passing off
> >as truth. In newsgroups and personal websites, people are free to write
> >whatever they like irregardless of it's truth.
Or grammatical or orthographical correctness.
> >Innocent people go to these
> >"sources" and repeat what they see there, thinking that it's correct.
This is
> >an alarming phenomenon. I fear that the internet simply cannot be trusted
as a
> >source of facts unless one is absolutely certain, as in the case of a
reputable
> >university or laboratory, that what they're reading is true. I for one,
only
> >use the books and articles written by reputable scientists that I can
usually
> >trust.
>
> Got a sporting proposition for you, Charles. What say you check out some
of
> those books and articles by reputable scientists and see what they have to
> say on this topic. Report back with your references and we'll compare
> notes.
Before doing that, you and Charles will need to come to some kind of
agreement on what constitutes a "reputable scientist".
Good luck.
(I claim the popcorn concession!)
Bill Hudson
Would you mind quoting it for me? I found some discussion of Feynman's
CalTech lectures, but it seems to be about 'topological entropy', which
is miniscule when compared to thermal entropy.
> >
> >
> > >
> > > >
> > > > Gravitational collapse is complicated and involves some twists but it is
> > > > spontaneous and overall a positive entropy change.
> > >
> > > It is not spontaneous, which is the main reason why certain cosmological theories
> > > that have the gases contracting under gravity are pure baloney. And it is definitely
> > > a negative entropy change.
> >
> > Where does the 'energy' in gravity come from? The system of collapsing
> > gas forming a star and burning converts potential energy into kinetic
> > energy, then kinetic energy into heat, which is then used as Ea in the
> > fusion reaction, which is then spontaneous.
>
> No one knows where the "energy" of gravity comes from. An object further from a
> gravitational field has more potential energy with respect to that field than an object
> that is closer. Standing on the ground, if the ground is used as the reference point, one
> has zero gravitational potential energy.
Yes, and where has that energy gone?
>... Likewise, as gases condense into stars, (if indeed
> that happens) then as the gravitational potential energy decreases as the star forms.
Same question
>..Of
> course, there's no reason whatsoever why a mass of diffuse gas should suddenly begin to
> condense and form into stars.
Lets just deal with the 'condense' part for now. Do you agree that
gravity exists (even though we don't understand it completely)? Do you
agree that it is calculated based on the masses of, and distance between
two objects?
Now, given a cloud of gas, absent any other forces such as light from
other stars, or other large masses in the region, what would prevent the
cloud of gas from collapsing?
If it is a small cloud, it will dissapate because the net gravity of the
gas cloud is insufficient to overcome the motion of the atoms. The
exact mass of the gas cloud necessary to begin collapsing spontaneously
will vary depending on the initial temperature of the gas. Hotter gas
would need a larger mass.
If it is large enough, the gas cloud will condense into a rotating disk,
and eventually into a spheroid.
Even this simple example is entropically positive in *both* thermal
entropy and 'topological entropy'. If you think about it, and the fact
that gravity is defined by the two masses and the distance between them,
you'll see why.
>... It's like saying that the gas in a box suddenly begins to
> condense under it's own gravity into a smaller volume. It's ridiculous.
If the box and the enclosed gas cloud were big enough, not it is not
ridiculous. Gravity is the weakest of the four basic forces. It takes a
lot of mass to form a gravity field steep enough to overcome the atomic
motion imparted by the temperature of the atoms (assuming the atoms are
not near 0K)
>... Insofar as fusion
> is concerned, there's no explanation as to why this condensing gas should suddenly begin to
> undergo a fusion reaction. Can the temperature get hot enough? These are troubling
> questions.
Yes, it can. Hydrogen clouds which are not too much larger (in terms of
mass) will generate enough heat to overcome the basic forces and
initiate fusion. Fusion generates a lot of heat. The heat dissapates
into the surroundings (the rest of the atoms) and causes *them* to begin
fusion. It doesn't happen in a box, or in a house, or even on Jupiter,
because there is not enough mass to generate the temperatures necessary.
> The nuclear fusion is an entirely different process. Potential energy is present in the
> nuclei of the atoms and this energy is released as mass changes into energy. The heat
> produced when the star contracts is the result of a different mechanism.
>
The heat produced when a gas cloud collapses is what *triggers* fusion.
Fusion doesn't create all the heat.
> >
> >
> > Are you saying that gas clouds do *not* contract due to gravity? Are
> > you really saying that?
>
> Yep, that's exactly what I'm saying. Kind of blows your mind, huh?
> I'm telling you that the basic premises that you hold true and dear are assumptions that in
> most liklihood have little or no validity or meaning in the real world.
>
Why? Because you don't see a box of gas collapse?
> Regards, Charlie Wagner
> http://www.charliewagner.com
>
> >
> >
> > >
> > > Regards, Charlie Wagner
> > > http://www.charliewagner.com
> > >
> > > >
> > > >
> > > > > > In fact, one of the major unsolved problems of cosmology is the problem
> > > > > > of why the Universe seems to have started out so uniform, since that's
> > > > > > a state of such low entropy.
> > > > >
> > > > > The "major unsolved question of cosmology" is where the low entropy of the
> > > > > stars came from. If the universe started out so uniform, how did this high
> > > > > entropy change into the low entropy that we now find in stars.
> >
> > --
> > Bill
> >
> > "Let every nation know, whether it wishes us well or ill,
> > that we shall pay any price, bear any burden, meet any hardship,
> > support any friend, oppose any foe to assure the survival and
> > the success of liberty." - President John F. Kennedy, Inaugural Address,
> > January 20, 1961
--
Bill
Bill Hudson
>
> Chris Ho-Stuart wrote:
>
> > Almost every contributor to this thread so far has made statements
> > which are oversimplified, misleading, or just plain wrong. Myself
> > included.
[snipped]
> > A reference which helped me in this post is an article from
> > the "Mad Scientist Network"
> > <http://www.madsci.org/>
> > an educational site at which professional scientists
> > will answer questions. In 1999, the question was asked
> > "how is entropy effected during the formation of a star?"
> > and the answer by William Wheaton at
> > <http://128.252.223.112:80/posts/archives/sep99/937295445.As.r.html>
> > gives a lot of very helpful detail. He provides some calculations,
> > which demonstrate that the change in volume of gases as they are
> > compressed constitutes a huge decrease in entropy, which is not
> > balanced by the local entropy increase due to heating of those
> > gases. He does not, unfortunately, similarly quantify the entropy
> > associated with radiation generated during collapse, but he points
> > out that this is the major entropy sink of the system.
> >
> > Best wishes all -- Chris
>
> Thank you for the very fair and even-handed analysis. I will add that it was
> presumptuopus of me to declare that stars cannot form by gravitational force
> acting on a large mass of diffuse gas.
>
> Regards, Charlie Wagner
> http://www.charliewagner.com
Thank you Charlie. Being as this is the case, there is no real need to
followup to my other posts I have made this morning, unless you feel so
inclined.
Ferrous Patella
[...]
>
>Thank you for the very fair and even-handed analysis. I will add that it was
>presumptuopus of me to declare that stars cannot form by gravitational force
>acting on a large mass of diffuse gas.
>
>Regards, Charlie Wagner
This makes twice that I have seen Charlie admit to being in error and he
should be commended for it.
Charlie, I think the key word here is "presumptuous". You strike me as a smart
guy guilty of science by sound bites. (You are not alone in this here in TO).
This would not be so bad if it wasn't for your arguments from "baloney".
(Again, you are not alone here and if I were to be really even-handed, I would
go and find some others' argument from "crap".) The thermo thread clearly
demonstrates that, in science, the devil is in the details.
--
Ferrous Patella
SI HOC LEGERE SCIS NIMIUM ERUDITIONIS HABES
Matt Silberstein
[snip]
> If we cool the gas and it condenses into a liquid, its entropy
> decreases.
Are you really saying this? That cooling a gas increases its entropy?
Do you really want to say that a given volume of gaseous material is
at lower entropy when cool than when hot?
> The same is true of a star. When the gas is spread out, it's at
> maximum entropy. If it condenses into stars, it's entropy decreases and the
> energy available to do work increases.
If you take the negative energy of the gravitational potential into
account then you have an entroy increase with the collapse. Perhaps
instead of saying "wrong" you can show your work.
> The heat in a star does not come from
> the process of condensation, it's a whole different reaction, nuclear fusion.
The nuclear fusion gets ignited by the heat of the collapse.
[snip]
Charles Wagner
Matt Silberstein wrote:
> Charles Wagner <cha...@charliewagner.com> wrote in message news:<3BFAF298...@charliewagner.com>...
> [snip]
>
> > If we cool the gas and it condenses into a liquid, its entropy
> > decreases.
>
> Are you really saying this? That cooling a gas increases its entropy?
Put your glasses on Mark. It clearly says "decreases".
>
> Do you really want to say that a given volume of gaseous material is
> at lower entropy when cool than when hot?
Put on your glasses Mark, it clearly says "liquid"
>
>
> > The same is true of a star. When the gas is spread out, it's at
> > maximum entropy. If it condenses into stars, it's entropy decreases and the
> > energy available to do work increases.
>
> If you take the negative energy of the gravitational potential into
> account then you have an entroy increase with the collapse.
No you don't.
> Perhaps
> instead of saying "wrong" you can show your work.
>
> > The heat in a star does not come from
> > the process of condensation, it's a whole different reaction, nuclear fusion.
>
> The nuclear fusion gets ignited by the heat of the collapse.
I don't think "ignited" is the word you want.
Regards, Charlie Wagner
http://www.charliewagner.com
>
>
> [snip]
Tim Tyler
: Wade Hines <wade....@rcn.com> wrote:
:> Steve and Lesa wrote:
:>> I have a definition of entropy I got out of Webster's, if anyone is
:>> really interested in the particulars let me know and I will post all
:>> the necessary information to properly cite the source.
:
:>> It was the 3rd. definition. Definitions 1 and 1a dealt with the 2nd Law
:>> of Thermodynamics, the 2nd definition had to do with logarithms and
:>> message frequency and the 3rd was the one that caught my eye:
:
:>> ....3 the degradation of the matter and energy in the universe to an
:>> ultimate state of inert uniformity.
:> Eck.
: Double eck! This is not only not a definition of entropy, it's flat-out
: wrong as a statement of physics.
: Which has more entropy, an ``inert uniform'' cloud of hydrogen or the
: same hydrogen clumped together into stars? The answer is the latter.
: In any system in which gravity is an important force, an ``inert uniform''
: state has *low* entropy compared to a lumpy, uneven state. The highest
: entropy state is typically the one in which the matter is all compacted
: together to form a black hole.
Since - as far as physicists can tell - the universe is open - and black
holes evaporate - the highest entropy state will not look like a lot of
black holes - and might look rather a lot like a state of inert
uniformity.
However that "definition" of entropy was wrong. Even my pocket dictonary
does better:
``Entropy: n, unavalability of the heat energy of a system for mechanical
work; measurement of this.''
[Collins gem]
--
__________
|im |yler Index of my domains: http://timtyler.org/ t...@iname.com
Chris Ho-Stuart
> Charles Wagner <cha...@charliewagner.com> wrote in message news:<3BFAF298...@charliewagner.com>...
> [snip]
>
>> If we cool the gas and it condenses into a liquid, its entropy
>> decreases.
>
> Are you really saying this? That cooling a gas increases its entropy?
> at lower entropy when cool than when hot?
No: he is saying that CONDENSING a gas decreases its entropy.
Read the sentence a bit more carefully. He's right.
>> The same is true of a star. When the gas is spread out, it's at
>> maximum entropy. If it condenses into stars, it's entropy decreases and the
>> energy available to do work increases.
>
> If you take the negative energy of the gravitational potential into
> account then you have an entroy increase with the collapse. Perhaps
> instead of saying "wrong" you can show your work.
And if you do show the work, you will actually find that taking
gravitational potential into effect still leaves you with an
entropy decrease in the collapse.
The decrease is local, of course; and there is a greater increase
elsewhere to compensate: but you will need to look beyond
gravitations potential to find it.
Thermodynamics is one of those areas where almost everyone will
make mistakes, because almost everyone is continuing to work
intutively without a solid grounding in the actual definitions.
Me included.
Cheers -- Chris
Steve Carlip
> Steve Carlip wrote:
>> Which has more entropy, an ``inert uniform'' cloud of hydrogen
>> or the same hydrogen clumped together into stars? The answer
>> is the latter. In any system in which gravity is an important force,
>> an ``inert uniform'' state has *low* entropy compared to a lumpy,
>> uneven state.
> Actually, the answer is that you're wrong. The entropy of a
> collapsing cloud of instellar matter *decreases*, but the 2Lot is not
> violated because the overall entropy of the universe increases to
> compensate.
Actually, I am right, though my phrasing may have been misleading.
So are you. It depends, of course, on what you mean by ``the overall
entropy of the universe,'' and where you make the split between the
``system'' and the ``universe.''
Start with a uniform gas in an otherwise empty region. If the gas is
big enough or dense enough---if its volume is larger than roughly
the cube of the Jeans length---it will begin to collapse into lumps.
This dynamical instability has been known since Jeans' work in 1902.
These days it can be watched quite carefully in many-body computer
simulations.
What happens to entropy during this process? The modern work on
this apparently began with a 1962 paper by Antonov, but it's in an
obscure Russian journal, and I confess I haven't read it. The usual
reference is a paper by Lynden-Bell and Wood, Mon. Not. R. Astr. Soc.
138 (1968) 495. As you say, the entropy of each individual clump
decreases. As I say, the entropy of the system as a whole increases.
This is not a contradiction. It possible because during the process
of gravitational collapse, individual particles and small clumps get
flung out of the collapsing regions at very high speeds. The ``extra''
entropy ends up in a hot, thin ``interstellar'' gas.
You can, if you like, call this an increase in the entropy of the ``rest
of the Universe.'' But the ``rest of the Universe'' here need not be
some separate system; it can be a portion of the gas you started out
with. In particular, you don't need to have something else to carry
off the energy, although the clumping will happen faster if you do.
In fact, you can imagine putting the whole system inside a perfectly
reflecting box, so the ``interstellar gas'' can't escape. If the box is big
enough, you will still get a ``gravothermal catastrophe''---the gas
will segregate into a contracting central core and a surrounding halo.
So I stand by my statement that an ``inert uniform'' state has low
entropy compared to a lumpy, uneven state, provided that it's the
right lumpy, uneven state---the one produced by the dynamical
evolution. The key point is that the ``inert uniform'' state has a
low entropy, and that dynamical processes increase that entropy
while making the state much clumpier.
Steve Carlip
dkomo
I too did some graduate work in physics although quite a bit later
than this. I left it because it wasn't a practical career, but it did
provide an excellent background for pursuit of further technical
subjects. After physics, other technical careers are pretty easy.
I found that physics "concentrates the mind wonderfully." I believe
it was Samuel Johnson who said this, refering to the effect an
impending execution has on a prisoner being wheeled off to meet his
fate on a cheery sunny morning.
--dk...@cris.com
Chris Ho-Stuart
I am not familiar with the complex analysis of Lynden-Bell and Wood;
but a quick glance suggests to me that the outflow of energy from the
negative specific heat of the collapsing system is more significant
that the ejection of matter particles. At least, this is my current
understanding, and it seems consistent with a quick glance at simple
descriptions of the kinds of theory developed by Lynden-Bell and Wood at
<http://w3-phystheo.ups-tlse.fr/~chavanis/2Dturbulence.html>
That is, the entropy increase is found mostly in the emitted
radiation, rather than ejected particles. The clumping is a
localised decrease in entropy, compensated for by entropy
bound up with radiant energy (photons).
Radiation will, of course, lead to some heating of the interstellar
medium: but most will remain as photons, I think. That is, I would
guess the last sentence above should be replaced with:
The ``extra'' entropy ends up in radiated energy from
the system.
and the preceding paragraph should take more account of this
radiation: the temperature and density distribution of the matter
involved will (I think) not be enough to locate the entropy
increase in the case of a collapsing star, even taking ejection
and heating of the interstellar gas into account.
I'm a rank amateur at this: take everything with a grain of salt.
But I hope I am at least pointing in roughly the right direction.
Cheers -- Chris
Wade Hines
I agree about the radiation. One has think about the symmetry of
conversion of potential energy to kinetic energy via the
collapse. We need something more than billiard ball type
models of the changes and from what I can see, radiation
of energy into background radiation (energy that can't be recouped)
is exactly what the Dr. ordered. At least I want that to
be how it makes sense. I don't claim to understand any
of this in an adequate manner.
Steve Carlip
>> big enough or dense enough---if its volume is larger than roughly
>> the cube of the Jeans length---it will begin to collapse into lumps.
>> What happens to entropy during this process? [...]
>> As you say, the entropy of each individual clump
>> decreases. As I say, the entropy of the system as a whole increases.
>> This is not a contradiction. It possible because during the process
>> of gravitational collapse, individual particles and small clumps get
>> flung out of the collapsing regions at very high speeds. The ``extra''
>> entropy ends up in a hot, thin ``interstellar'' gas.
> I am not familiar with the complex analysis of Lynden-Bell and Wood;
> but a quick glance suggests to me that the outflow of energy from the
> negative specific heat of the collapsing system is more significant
> that the ejection of matter particles.
> That is, the entropy increase is found mostly in the emitted
> radiation, rather than ejected particles. The clumping is a
> localised decrease in entropy, compensated for by entropy
> bound up with radiant energy (photons).
This depends on the details of the system. If you're looking at a cloud
of hydrogen gas collapsing to form stars, I believe you're right---most
of the energy is carried off by radiation. This is certainly true for a
thin plasma; I don't know the details of what happens when the density
gets high and the gas gets optically thick.
If you're looking at a cloud of stars in a globular cluster, it's the loss
of high-energy ``hot'' stars that dominates, though again things get
complicated when the core density gets large enough and three-
body interactions become important. There's a nice description at
<http://grape.astron.s.u-tokyo.ac.jp/~makino/papers/lscrev2_preprint/node1.html>
If you're looking at ``dark matter,'' which presumably dominated the
early stages of structure formation, the answer depends on the details
of the interactions (if any) of dark matter with everything else. Photons
would presumably be unimportant, since dark matter doesn't couple to
electromagnetism.
In each of these cases, the underlying thermodynamics is the same. A
self-gravitating system is unstable against gravitational collapse, which
leads to spontaneous ``clumping'' with excess energy carried off by
something. The ``something'' can be external to your original system
(e.g., photons), or it can be part of your original system (e.g., stars in
a surrounding halo). The details are absolutely necessary, of course,
in determining rates. But the qualitative features are determined by
fairly general properties of gravity---in particular, its long-range and
strictly attractive nature, and the consequent negative specific heat of
self-gravitating systems---and don't depend on those details.
> I'm a rank amateur at this: take everything with a grain of salt.
Well, I'm a half-amateur, I guess. My field is gravity, and I know a
lot about things like black hole thermodynamics. But ``structure
formation'' is a pretty specialized field, and while I try to keep up
with the broad outlines, I'm certainly no expert at the details.
Steve Carlip
dkomo
Admittedly the John Baez link makes no mention of all these
complications in a collapsing gas cloud. He merely talks about the
collapse of a homogeneous cloud of gas to a central core. As it
collapses, it loses total energy even as it grows hotter. Although
Baez doesn't explicitly say it, I assume this energy loss is due to
radiation -- thermal at first, then shifted to higher frequencies as
the temperature rises. It's this radiation that increases the entropy
of "the rest of the universe" and saves the 2Lot.
But even after you described all the complications that can occur in a
*real* collapsing gas cloud, I honestly am not convinced that the
total gas cloud after some period of collapse, including the central
core, surrounding halo, and any material crap it has thrown off, has,
in toto, increased its entropy. It seems to me that Baez's arguments
still hold for all the individual components of the fragmented cloud,
and when you add all the entropies together, you see a decrease of
total entropy.
Kim G. S. OEyhus
>> spontaneous and overall a positive entropy change.
>
No, he is right.
Kim, M.Sc. Physics
Charles Wagner
No, he is absolutely wrong.
Perhaps you can offer a plausible explanation of why you think he is right.
First of all, there is not a shred of evidence that I'm aware of that stars
form when the denser parts of the core of a cloud of interstellar dust
collapses under the force of gravity. This is a well repeated assumption, but I
see no evidence of any kind to justify such a claim. I can see no mechanism
that would explain why an otherwise diffuse cloud of gas would begin to shrink
and condense. Perhaps you can offer further insight.
Secondly, when the cloud of gas begins to contract and condense (assuming
that it does), the entropy of the gas cloud decreases. A dense, tightly packed
cloud of gas has less entropy that a diffuse, spread out cloud. Clearly, the
2nd law of thermodynamics cannot have held true at the beginning of the
universe. Something had to "wind the clock" in the opposite direction from the
normal "arrow of time". At some point, the entropy of the entire universe had
to decrease, so that we could avail ourselves of the low entropy present in
today's stars.
Regards, Charlie Wagner
http://www.charliewagner.com
>
>
> Kim, M.Sc. Physics
Wade Hines
I thought you had admitted to you error but now you repeat it.
Here's an excercise: reverse the process. What does it take to overcome
the gravitational attraction and raise the potential energy of particles?
You've also ignored my examples of the density gradient in an
atmosphere. It's one thing to be mistaken, it's anther to be
persistent in the face of multiple corrections.
By the way, you changed what I wrote to a focus on just the gas.
It has been explained that background radiation is released upon
collapse. What you can think of is a gas cloud with a background
T of 2 degrees K vs. a condensed cloud with a background T of 4
degrees K. To reverse the process, you need to convert the 4
degree background into a 2 degree background. Think about it.
Charles Wagner
Wade Hines wrote:
I said that it was presumptuous of me to declare that it was not possible for this to
happen. Similarly, it would be presumptuous of me to declare that there is no god. I
lack sufficient observational and/or experimental evidence to confirm or deny it. You
didn't answer my objections. What mechanism could be envisioned that would cause a
cloud of diffuse gas to begin to contract under the influence of gravity? If the
universe started out uniform and homogeneous, what would precipitate the formation of
stars, galaxies, etc. Smoot thinks he has the answer in his anisotropies, little
wrinkles in the universe that act as seeds around which the stars and galaxies can
form. Nice idea, but it unfortunately falls short of a complete explanation. Your
example of the density layers in the atmosphere is also interesting, but I think that
the presence of an envelope of gas around a massive body, such as the earth is a lot
different than a diffuse cloud of gas in interstellar space. On the earth, the
massive gravitational pull of the earth attracts the gaseous molecules and draws them
toward the surface. In a diffuse cloud in space, all of the particles are exerting
essentially the same gravitational effect on all of the other particles. These
effects would seem to cancel each other out, just like the magnetic domains in a
non-magnetic piece of iron. How is it possible to get most of the gravitational force
acting in one direction, so as to cause it to shrink?
The formation of the universe from a uniform, homogeneous state to a "clumpy"
state in which there are huge differences in density among stars, nebula and
interstellar space required that the entropy of the universe decreases. We must
address the question of where this low entropy that is present in the universe came
from. All current explanations (apologies to Smoot, et.al.) fall short of a complete
explanation. The second law shoulkd be more carefully stated to say that entropy
increases in all natural processes, starting from a time after the formation of stars
and galaxies. Before that time, the opposite would have had to occur.
Bigdakine
>From: Charles Wagner cha...@charliewagner.com
>Date: 11/24/01 1:38 PM Hawaiian Standard Time
>Message-id: <3C002FB0...@charliewagner.com>
Density waves for one. Shocks from a supernova are another.
If
>the
>universe started out uniform and homogeneous, what would precipitate the
>formation of
>stars, galaxies, etc. Smoot thinks he has the answer in his anisotropies,
>little
>wrinkles in the universe that act as seeds around which the stars and
>galaxies can
>form. Nice idea, but it unfortunately falls short of a complete explanation.
What, in your opinion, is it lacking?
Stuart
Dr. Stuart A. Weinstein
Ewa Beach Institute of Tectonics
"To err is human, but to really foul things up
requires a creationist"
Wade Hines
Charles Wagner wrote:
> Wade Hines wrote:
> > Charles Wagner wrote:
> > > "Kim G. S. OEyhus" wrote:
> > > > Charles Wagner <cha...@charliewagner.com> wrote:
> > > > >Wade Hines wrote:
> > > > >> Gravitational collapse is complicated and involves some twists but it is
> > > > >> spontaneous and overall a positive entropy change.
> > > > >With all due respect, you are absolutely and completely wrong.
> > > > No, he is right.
> > > No, he is absolutely wrong.
> > > Perhaps you can offer a plausible explanation of why you think he is right.
> > > First of all, there is not a shred of evidence that I'm aware of that stars
> > > form when the denser parts of the core of a cloud of interstellar dust
> > > collapses under the force of gravity.
People have cited simulations. Perhaps you want to critique the simulations.
> > > This is a well repeated assumption, but I
> > > see no evidence of any kind to justify such a claim. I can see no mechanism
> > > that would explain why an otherwise diffuse cloud of gas would begin to shrink
> > > and condense. Perhaps you can offer further insight.
Gravity. Now if you suppose a very sparse cloud that is entirely homogeneous you
do generally have balanced forces in all directions. Still, we know that such
systems are metastable because once an inhomogenety exits, the effect ripples.
Simple thermal motion basically demands that some temporary inhomogenety
will occur. What objections can anyone have up to this point?
> > > Secondly, when the cloud of gas begins to contract and condense (assuming
> > > that it does), the entropy of the gas cloud decreases. A dense, tightly packed
> > > cloud of gas has less entropy that a diffuse, spread out cloud.
Yes, this is the system. What of the surroundings? You have been offered multiple
web sites that do variable jobs of explaining this. Did you read through them
and if so do you have some specific objections?
> > > Clearly, the
> > > 2nd law of thermodynamics cannot have held true at the beginning of the
> > > universe. Something had to "wind the clock" in the opposite direction from the
> > > normal "arrow of time". At some point, the entropy of the entire universe had
> > > to decrease, so that we could avail ourselves of the low entropy present in
> > > today's stars.
I don't know what else you have in mind other than your presumption that
gravitational collapse is __overall__ negative with respect to entropy.
It has been stipulated that it is negative with respect to the gas cloud.
It has been further noted that space itself heats up.
> > I thought you had admitted to you error but now you repeat it.
> >
> > Here's an excercise: reverse the process. What does it take to overcome
> > the gravitational attraction and raise the potential energy of particles?
> >
> > You've also ignored my examples of the density gradient in an
> > atmosphere. It's one thing to be mistaken, it's anther to be
> > persistent in the face of multiple corrections.
> >
> > By the way, you changed what I wrote to a focus on just the gas.
> > It has been explained that background radiation is released upon
> > collapse. What you can think of is a gas cloud with a background
> > T of 2 degrees K vs. a condensed cloud with a background T of 4
> > degrees K. To reverse the process, you need to convert the 4
> > degree background into a 2 degree background. Think about it.
> I said that it was presumptuous of me to declare that it was not possible for this to
> happen. Similarly, it would be presumptuous of me to declare that there is no god. I
> lack sufficient observational and/or experimental evidence to confirm or deny it. You
> didn't answer my objections. What mechanism could be envisioned that would cause a
> cloud of diffuse gas to begin to contract under the influence of gravity? If the
> universe started out uniform and homogeneous, what would precipitate the formation of
> stars, galaxies, etc. Smoot thinks he has the answer in his anisotropies, little
> wrinkles in the universe that act as seeds around which the stars and galaxies can
> form. Nice idea, but it unfortunately falls short of a complete explanation.
It is born out by rather straightforward simulations. A full characterization
of the the distribution of galaxies or stars is a separate issue but simply
finding that perturbations from perfect homogeneity precipitate collapse
is non controversial.
> Your
> example of the density layers in the atmosphere is also interesting, but I think that
> the presence of an envelope of gas around a massive body, such as the earth is a lot
> different than a diffuse cloud of gas in interstellar space.
What is not different is that the difference in potential energy via gravity
acts against the entropy based tendency for a gas to expand. This is as true
within small containers of laboratory scale as it is of the atmosphere only
the difference is too small to notice. This has to be true given the changes
in a column of air: If the air at 30,000 feet is 40% as dense as it is at
sea level, the gradient is roughly continuous. (reality brings in weather
and temperature gradients that make this ugly but I expect you have no
problem with the example). The significance here is that there is a balance
between the density of the gas and its potential energy. What changes in
the model of a gravitationally collapsing gas cloud?
> On the earth, the
> massive gravitational pull of the earth attracts the gaseous molecules and draws them
> toward the surface. In a diffuse cloud in space, all of the particles are exerting
> essentially the same gravitational effect on all of the other particles. These
> effects would seem to cancel each other out, just like the magnetic domains in a
> non-magnetic piece of iron. How is it possible to get most of the gravitational force
> acting in one direction, so as to cause it to shrink?
It is a metastable situtation. _If_ random fluxuations generate a locally
denser zone, it will exert an unbalancing force locally. If these random
fluxuations generate forces less than thermal forces, these local
gravitational wells can be escaped. If the gas if too cool, it cannot
escape the transient gravitational wells and the wells deepen. Once homogeneity
is broken anywhere, the effects ripple in ways that you can probably
imagine for yourself.
> The formation of the universe from a uniform, homogeneous state to a "clumpy"
> state in which there are huge differences in density among stars, nebula and
> interstellar space required that the entropy of the universe decreases.
No, not the universe. It requires the entropy of the gas decrease. Do not
confuse this with the entropy of the universe.
> We must
> address the question of where this low entropy that is present in the universe came
> from.
Again, your presumption is in error.
> All current explanations (apologies to Smoot, et.al.) fall short of a complete
> explanation. The second law shoulkd be more carefully stated to say that entropy
> increases in all natural processes, starting from a time after the formation of stars
> and galaxies. Before that time, the opposite would have had to occur.
You really need to address standard works of physics on this before
presuming to rewrite the 2nd law.
Charles Wagner
Bigdakine wrote:
A mechanism that would explain why a diffuse cloud of gas would suddenly begin to
collapse and shrink.
Regards, Charlie Wagner
Charles Wagner
Wade Hines wrote:
> Charles Wagner wrote:
> > Wade Hines wrote:
> > > Charles Wagner wrote:
> > > > "Kim G. S. OEyhus" wrote:
> > > > > Charles Wagner <cha...@charliewagner.com> wrote:
> > > > > >Wade Hines wrote:
>
> > > > > >> Gravitational collapse is complicated and involves some twists but it is
> > > > > >> spontaneous and overall a positive entropy change.
>
> > > > > >With all due respect, you are absolutely and completely wrong.
>
> > > > > No, he is right.
>
> > > > No, he is absolutely wrong.
>
> > > > Perhaps you can offer a plausible explanation of why you think he is right.
>
> > > > First of all, there is not a shred of evidence that I'm aware of that stars
> > > > form when the denser parts of the core of a cloud of interstellar dust
> > > > collapses under the force of gravity.
>
> People have cited simulations. Perhaps you want to critique the simulations.
I have very little use for simulations. It was predicted that the oil fires started by
Saddam would wreak havoc with the atmospheric stability causing all kinds of bad effects.
Almost nothing happened. The simulations were wrong. Other simulations have been shown to
be equally incorrect (alaska oil spill, global warming, among others). There is no
logical proof that a simulation model is true. The real world is not a closed system like
in the simulation. There is also scaling up of non-additive properties, assumption
ladenness of data and underdetermination. The primary value of simulation models is
heuristic.
>
>
> > > > This is a well repeated assumption, but I
> > > > see no evidence of any kind to justify such a claim. I can see no mechanism
> > > > that would explain why an otherwise diffuse cloud of gas would begin to shrink
> > > > and condense. Perhaps you can offer further insight.
>
> Gravity. Now if you suppose a very sparse cloud that is entirely homogeneous you
> do generally have balanced forces in all directions. Still, we know that such
> systems are metastable because once an inhomogenety exits, the effect ripples.
Perhaps. but it's equally possible that the effect dissipates.
>
> Simple thermal motion basically demands that some temporary inhomogenety
> will occur. What objections can anyone have up to this point?
>
> > > > Secondly, when the cloud of gas begins to contract and condense (assuming
> > > > that it does), the entropy of the gas cloud decreases. A dense, tightly packed
> > > > cloud of gas has less entropy that a diffuse, spread out cloud.
>
> Yes, this is the system. What of the surroundings? You have been offered multiple
> web sites that do variable jobs of explaining this. Did you read through them
> and if so do you have some specific objections?
Yes, and I found a large amount of incorrect information being passed on as truth. It was a
most disconcerting experience. The arrow of time must go backwards before it goes fowards.
You have to produce low entropy before the 2nd law kicks in.
>
>
> > > > Clearly, the
> > > > 2nd law of thermodynamics cannot have held true at the beginning of the
> > > > universe. Something had to "wind the clock" in the opposite direction from the
> > > > normal "arrow of time". At some point, the entropy of the entire universe had
> > > > to decrease, so that we could avail ourselves of the low entropy present in
> > > > today's stars.
>
> I don't know what else you have in mind other than your presumption that
> gravitational collapse is __overall__ negative with respect to entropy.
> It has been stipulated that it is negative with respect to the gas cloud.
> It has been further noted that space itself heats up.
The diffuse cloud of gas is already at near maximum entropy. The formation of the star is a
lowering of entropy, followed by the release of energy, bringing the universe back to it's
initial state. It doesn't really increase the entropy of the universe, only brings it back
to wher it was. The question is, where did the low entropy come from?
>
> > > I thought you had admitted to you error but now you repeat it.
> > >
> > > Here's an excercise: reverse the process. What does it take to overcome
> > > the gravitational attraction and raise the potential energy of particles?
> > >
> > > You've also ignored my examples of the density gradient in an
> > > atmosphere. It's one thing to be mistaken, it's anther to be
> > > persistent in the face of multiple corrections.
> > >
> > > By the way, you changed what I wrote to a focus on just the gas.
> > > It has been explained that background radiation is released upon
> > > collapse. What you can think of is a gas cloud with a background
> > > T of 2 degrees K vs. a condensed cloud with a background T of 4
> > > degrees K. To reverse the process, you need to convert the 4
> > > degree background into a 2 degree background. Think about it.
>
> > I said that it was presumptuous of me to declare that it was not possible for this to
> > happen. Similarly, it would be presumptuous of me to declare that there is no god. I
> > lack sufficient observational and/or experimental evidence to confirm or deny it. You
> > didn't answer my objections. What mechanism could be envisioned that would cause a
> > cloud of diffuse gas to begin to contract under the influence of gravity? If the
> > universe started out uniform and homogeneous, what would precipitate the formation of
> > stars, galaxies, etc. Smoot thinks he has the answer in his anisotropies, little
> > wrinkles in the universe that act as seeds around which the stars and galaxies can
> > form. Nice idea, but it unfortunately falls short of a complete explanation.
>
> It is born out by rather straightforward simulations. A full characterization
> of the the distribution of galaxies or stars is a separate issue but simply
> finding that perturbations from perfect homogeneity precipitate collapse
> is non controversial.
Again we must ask ourselves whether we can really trust the simulations. I don't give them
as much credence as others might.
>
>
> > Your
> > example of the density layers in the atmosphere is also interesting, but I think that
> > the presence of an envelope of gas around a massive body, such as the earth is a lot
> > different than a diffuse cloud of gas in interstellar space.
>
> What is not different is that the difference in potential energy via gravity
> acts against the entropy based tendency for a gas to expand. This is as true
> within small containers of laboratory scale as it is of the atmosphere only
> the difference is too small to notice. This has to be true given the changes
> in a column of air: If the air at 30,000 feet is 40% as dense as it is at
> sea level, the gradient is roughly continuous. (reality brings in weather
> and temperature gradients that make this ugly but I expect you have no
> problem with the example). The significance here is that there is a balance
> between the density of the gas and its potential energy. What changes in
> the model of a gravitationally collapsing gas cloud?
There is no huge mass at the center which could explain the collapse.
>
>
> > On the earth, the
> > massive gravitational pull of the earth attracts the gaseous molecules and draws them
> > toward the surface. In a diffuse cloud in space, all of the particles are exerting
> > essentially the same gravitational effect on all of the other particles. These
> > effects would seem to cancel each other out, just like the magnetic domains in a
> > non-magnetic piece of iron. How is it possible to get most of the gravitational force
> > acting in one direction, so as to cause it to shrink?
>
> It is a metastable situtation. _If_ random fluxuations generate a locally
> denser zone, it will exert an unbalancing force locally. If these random
> fluxuations generate forces less than thermal forces, these local
> gravitational wells can be escaped. If the gas if too cool, it cannot
> escape the transient gravitational wells and the wells deepen. Once homogeneity
> is broken anywhere, the effects ripple in ways that you can probably
> imagine for yourself.
Perhaps...but I wouldn't bet the ranch on it.
>
>
> > The formation of the universe from a uniform, homogeneous state to a "clumpy"
> > state in which there are huge differences in density among stars, nebula and
> > interstellar space required that the entropy of the universe decreases.
>
> No, not the universe. It requires the entropy of the gas decrease. Do not
> confuse this with the entropy of the universe.
>
> > We must
> > address the question of where this low entropy that is present in the universe came
> > from.
>
> Again, your presumption is in error.
>
> > All current explanations (apologies to Smoot, et.al.) fall short of a complete
> > explanation. The second law shoulkd be more carefully stated to say that entropy
> > increases in all natural processes, starting from a time after the formation of stars
> > and galaxies. Before that time, the opposite would have had to occur.
>
> You really need to address standard works of physics on this before
> presuming to rewrite the 2nd law.
These comments are based on standard physics, of which I am well aware.
Richard Clayton
Charles Wagner wrote:
It's called "gravity."
--
Richard Clayton (for...@earthlink.net)
"Facts do not cease to exist because they are ignored."
-- Aldous Huxley
John Wilkins
> Wade Hines wrote:
>
....
> > between the density of the gas and its potential energy. What changes in
> > the model of a gravitationally collapsing gas cloud?
>
> There is no huge mass at the center which could explain the collapse.
>
I can't believe you said that. The cloud must have a centre of gravity,
however, so if its angular momentum is not enough to prevent it, or
there are perturbing influences nearby, of course the gas is going to
collapse.
--
John Wilkins
Occasionally making sense for over 46 years
Wade Hines
How convenient!
> > > > > This is a well repeated assumption, but I
> > > > > see no evidence of any kind to justify such a claim. I can see no mechanism
> > > > > that would explain why an otherwise diffuse cloud of gas would begin to shrink
> > > > > and condense. Perhaps you can offer further insight.
> >
> > Gravity. Now if you suppose a very sparse cloud that is entirely homogeneous you
> > do generally have balanced forces in all directions. Still, we know that such
> > systems are metastable because once an inhomogenety exits, the effect ripples.
>
> Perhaps. but it's equally possible that the effect dissipates.
There is a thermal trigger. This is very akin to escape velocity. As
thy physics isn't that hard I presume you haven't bothered with
this in any significant way. A key presumption is that the universe
was expanding. Expansion necessitates cooling and upon cooling
local concentrations develope gravitational wells that are deep
enough to prohibit thermal escape. There are many variables that
could result in different results but microwave background radiation
has been measured and is roughly consistent with models that are
predicted by inflationary theories and current galaxy distributions
but I am extending myself beyond my comfort zone.
> > Simple thermal motion basically demands that some temporary inhomogenety
> > will occur. What objections can anyone have up to this point?
> > > > > Secondly, when the cloud of gas begins to contract and condense (assuming
> > > > > that it does), the entropy of the gas cloud decreases. A dense, tightly packed
> > > > > cloud of gas has less entropy that a diffuse, spread out cloud.
> > Yes, this is the system. What of the surroundings? You have been offered multiple
> > web sites that do variable jobs of explaining this. Did you read through them
> > and if so do you have some specific objections?
> Yes, and I found a large amount of incorrect information being passed on as truth. It was a
> most disconcerting experience. The arrow of time must go backwards before it goes fowards.
> You have to produce low entropy before the 2nd law kicks in.
I don't understand this requirement. Is it metaphysical or philosophical?
I know you are a Hoyle fan but where is your data?
> > > > > Clearly, the
> > > > > 2nd law of thermodynamics cannot have held true at the beginning of the
> > > > > universe. Something had to "wind the clock" in the opposite direction from the
> > > > > normal "arrow of time". At some point, the entropy of the entire universe had
> > > > > to decrease, so that we could avail ourselves of the low entropy present in
> > > > > today's stars.
> > I don't know what else you have in mind other than your presumption that
> > gravitational collapse is __overall__ negative with respect to entropy.
> > It has been stipulated that it is negative with respect to the gas cloud.
> > It has been further noted that space itself heats up.
> The diffuse cloud of gas is already at near maximum entropy.
No. This is fundamentally wrong. It seems to be bedrock for you but
it just doesn't bear out. If you take a star and drive a process where
you disperse its contents in an expansion you get a decrease in
entropy. Statistical mechanical models bear this out. Remember that
there is a finite level of energy in the system.
Of course this does depend on the total volume and total energy.
As far as I can tell, our universe is cool enough and sparce
enough that collapsed systems are entropically favored. That
is standard physics. Could you at least cite something that
supports your position?
? The formation of the star is a
> lowering of entropy, followed by the release of energy, bringing the universe back to it's
> initial state.
It is not required that a star ignite and start fusion. If I were to
require this, my arguments would be logically untenable. Repeating
yet again, the background T of space is key.
? It doesn't really increase the entropy of the universe, only brings it back
> to wher it was. The question is, where did the low entropy come from?
You keep asserting a bogus model of entropy. It is trivially refuted
by my example of an atmosphere.
They predict phase transitions and this is rather hard to refute. Likewise, so is
the metastability. Near as I can tell, your objections are based completely on
a myopic focus on a system (gas collapse) coupled with ignoring the surroundings
(background radiant T of space).
> > > Your
> > > example of the density layers in the atmosphere is also interesting, but I think that
> > > the presence of an envelope of gas around a massive body, such as the earth is a lot
> > > different than a diffuse cloud of gas in interstellar space.
> > What is not different is that the difference in potential energy via gravity
> > acts against the entropy based tendency for a gas to expand. This is as true
> > within small containers of laboratory scale as it is of the atmosphere only
> > the difference is too small to notice. This has to be true given the changes
> > in a column of air: If the air at 30,000 feet is 40% as dense as it is at
> > sea level, the gradient is roughly continuous. (reality brings in weather
> > and temperature gradients that make this ugly but I expect you have no
> > problem with the example). The significance here is that there is a balance
> > between the density of the gas and its potential energy. What changes in
> > the model of a gravitationally collapsing gas cloud?
> There is no huge mass at the center which could explain the collapse.
The gravitational potential need not be huge, just greater than the
thermal energy. Again, think escape velocity. Mercury has no atmosphere
because it is too hot. Standard models of galaxy formation, nebula
formation, star and planet formation pay attention to both T and mass.
I don't see a coherent objection on you part other than a misguided
notion of entropy of the system ignoring the surroundings.
> > > On the earth, the
> > > massive gravitational pull of the earth attracts the gaseous molecules and draws them
> > > toward the surface. In a diffuse cloud in space, all of the particles are exerting
> > > essentially the same gravitational effect on all of the other particles. These
> > > effects would seem to cancel each other out, just like the magnetic domains in a
> > > non-magnetic piece of iron. How is it possible to get most of the gravitational force
> > > acting in one direction, so as to cause it to shrink?
> > It is a metastable situtation. _If_ random fluxuations generate a locally
> > denser zone, it will exert an unbalancing force locally. If these random
> > fluxuations generate forces less than thermal forces, these local
> > gravitational wells can be escaped. If the gas if too cool, it cannot
> > escape the transient gravitational wells and the wells deepen. Once homogeneity
> > is broken anywhere, the effects ripple in ways that you can probably
> > imagine for yourself.
> Perhaps...but I wouldn't bet the ranch on it.
Not perhaps but necessary. You need to invent a means to overcome this
result or assert a high enough T to overcome stocastically produced
inhomogeneties. The system is simply metastable.
> > > The formation of the universe from a uniform, homogeneous state to a "clumpy"
> > > state in which there are huge differences in density among stars, nebula and
> > > interstellar space required that the entropy of the universe decreases.
> > No, not the universe. It requires the entropy of the gas decrease. Do not
> > confuse this with the entropy of the universe.
> > > We must
> > > address the question of where this low entropy that is present in the universe came
> > > from.
> > Again, your presumption is in error.
> > > All current explanations (apologies to Smoot, et.al.) fall short of a complete
> > > explanation. The second law shoulkd be more carefully stated to say that entropy
> > > increases in all natural processes, starting from a time after the formation of stars
> > > and galaxies. Before that time, the opposite would have had to occur.
> > You really need to address standard works of physics on this before
> > presuming to rewrite the 2nd law.
> These comments are based on standard physics, of which I am well aware.
Please cite your sources.
H,R.Gruemm
They would if gravity was mediated by vector (spin-1) particles, like
electromagnetism is; those lead to both attractive and repulsive
forces. Gravity is a purely attractive long-range force (1/r^2), its
effects all add up. It is
well-known that the thermodynamic limit of a system under attractive
1/r^2 forces does not exist.
How is it possible to get most of the gravitational force
> acting in one direction, so as to cause it to shrink?
The direction is "towards the center of mass".
Regards,
HRG.
<snip>
Wade Hines
John Wilkins wrote:
>
> Charles Wagner <cha...@charliewagner.com> wrote:
>
> > Wade Hines wrote:
> >
> ....
> > > between the density of the gas and its potential energy. What changes in
> > > the model of a gravitationally collapsing gas cloud?
> >
> > There is no huge mass at the center which could explain the collapse.
> >
>
> I can't believe you said that. The cloud must have a centre of gravity,
> however, so if its angular momentum is not enough to prevent it, or
> there are perturbing influences nearby, of course the gas is going to
> collapse.
Only for a finite universe or one that doesn't wrap unto itself.
Think a circle except run a few more dimensions and take some
acid or chew a few peyote buttons. They key is still that the gas
has to have enough thermal energy to escape transient wells
produced by stocastic density variations.
Chris Ho-Stuart
> "Kim G. S. OEyhus" wrote:
>
>> In article <3BFA9959...@charliewagner.com>,
>> >> spontaneous and overall a positive entropy change.
>> >
>> >With all due respect, you are absolutely and completely wrong.
>>
>> No, he is right.
>
> No, he is absolutely wrong.
>
> Perhaps you can offer a plausible explanation of why you think he is right.
Huh? I though you had agreed that on this point, there is an overall
a positive entropy change. The process is complicated, but the end
result is unambiguous: the collapse overall involves an increase
in entropy because the system radiates heat energy as it collapses,
and the associated entropy increase with that radiation more than
balances the local entropy decrease in compression of the collapsing
cloud.
Cheers -- Chris
Charles Wagner
Richard Clayton wrote:
> Charles Wagner wrote:
>
> > Bigdakine wrote:
> >
> > A mechanism that would explain why a diffuse cloud of gas would suddenly begin to
> > collapse and shrink.
>
> It's called "gravity."
Since the various particles are distributed randomly in a diffuse cloud, it seems to me
that the vector sum of all of these forces would be zero.
Regards, Charlie Wagner
http://www.charliewagner.com
>
Charles Wagner
John Wilkins wrote:
> Charles Wagner <cha...@charliewagner.com> wrote:
>
> > Wade Hines wrote:
> >
> ....
> > > between the density of the gas and its potential energy. What changes in
> > > the model of a gravitationally collapsing gas cloud?
> >
> > There is no huge mass at the center which could explain the collapse.
> >
>
> I can't believe you said that. The cloud must have a centre of gravity,
> however, so if its angular momentum is not enough to prevent it, or
> there are perturbing influences nearby, of course the gas is going to
> collapse.
The concept of "center of gravity" is used to describe the force on a body being
acted on by a gravitational attraction from another source. For example, the
center of gravity of the Leaning Tower of Pisa can be calculated with respect to
the earth's gravitational attraction. If the LToP was beamed into space, outside
of the earth's gravitational influence, I don't believe it would have any
particular center of gravity.
Anyway, it seems much more likely to me that a mass of diffuse gas in space
would tend to spread out further to fill the volume available to it.
Regards, Charlie Wagner
http://www.charliewagner.com
>
>
> --
pz
Charles Wagner <cha...@charliewagner.com> wrote:
> Richard Clayton wrote:
>
> > Charles Wagner wrote:
> >
> > > Bigdakine wrote:
> > >
[snip]
> > > > What, in your opinion, is it lacking?
> > >
> > > A mechanism that would explain why a diffuse cloud of gas would
> > > suddenly begin to collapse and shrink.
> >
> > It's called "gravity."
>
> Since the various particles are distributed randomly in a diffuse
> cloud, it seems to me that the vector sum of all of these forces would be zero.
Well, yes, I would guess that the vector sum might very well be zero, as
long as the center of the cloud wasn't moving anywhere. That doesn't say
anything about whether the cloud will shrink.
Here's a simple example, a cloud with two particles:
O --> <-- O
The vector sum is zero, but the only forces acting on the two are their
mutual attraction, and they will collapse on each other.
--
pz
pz
Charles Wagner <cha...@charliewagner.com> wrote:
> John Wilkins wrote:
>
> > Charles Wagner <cha...@charliewagner.com> wrote:
> >
> > > Wade Hines wrote:
> > >
> > ....
> > > > between the density of the gas and its potential energy. What
> > > > changes in the model of a gravitationally collapsing gas cloud?
> > >
> > > There is no huge mass at the center which could explain the
> > > collapse.
> > >
> >
> > I can't believe you said that. The cloud must have a centre of
> > gravity, however, so if its angular momentum is not enough to
> > prevent it, or there are perturbing influences nearby, of course
> > the gas is going to collapse.
>
> The concept of "center of gravity" is used to describe the force on a
> body being acted on by a gravitational attraction from another
> source. For example, the center of gravity of the Leaning Tower of
> Pisa can be calculated with respect to the earth's gravitational
> attraction. If the LToP was beamed into space, outside of the earth's
> gravitational influence, I don't believe it would have any particular
> center of gravity.
You've lost me. Way back when I took college physics, we learned that
you can calculate the gravitational force between *any* two objects with
that ol' formula, G*m1*m2/R^^2. Do you mean that once we launch the
leaning tower, we can't calculate the attraction between a brick in the
basement and one on the roof anymore?
And where is that place where it would be outside the earth's
gravitational influence?
> Anyway, it seems much more likely to me that a
> mass of diffuse gas in space would tend to spread out further to fill
> the volume available to it.
It seems to me that that would depend on the density, mass of the
particles, and temperature of the cloud, don't you think? I mean, I'm
just a lowly biologist who doesn't fuss over that physics stuff much
anymore, but there sure seems to be something fundamentally wrong with
the way you are thinking about this subject.
You aren't going to start telling us about "heavy boots" soon, are you?
--
pz
Richard Clayton
If the cloud were completely homogenous and infinite in volume, yes, the net
gravitational effect would be zero. However, in a FINITE cloud, there is a center of
gravity, toward which the cloud will tend to collapse.
This is pretty elementary stuff. I suggest you acquire a basic understanding of a
scientific theory before you start decrying it as fraudulent.
Richard Clayton
Gravity isn't just for planets, Mr. Wagner. Transport the Leaning Tower of Pisa
into space and it has its own center of gravity. Even single atoms have their own
gravitational fields. If you've got mass, you've got gravity. End of story.
Yes, gas in an open space does tend to expand; but this is not the same as
saying it will ALWAYS expand. The superheated plasma found at the core of Sol would
also tend to expand outward- but gravity prevents this from happening. A star is, in
essence, a hydrogen cloud dense enough and hot enough to fuse. Do you doubt the
existence of our Sun?
Bigdakine
>From: Charles Wagner cha...@charliewagner.com
>Message-id: <3C006B8D...@charliewagner.com>
The simulations were correct. What was wrong was that the values for the
character of the *soot* used in the simulations was wrong. The *soot* from oil
fires has different properties than the stuff kicked up by a nuclear holocaust.
When the appropriate parameters for oil fire soot are used, the simulations
work just fine.
Bigdakine
>From: Charles Wagner cha...@charliewagner.com
>Message-id: <3C00FD98...@charliewagner.com>
Charles,
That does not preclude the cloud from collapsing. For example, the cloud can
collapse in such away that the center of mass is fixed.
Stuart
Bigdakine
>From: Charles Wagner cha...@charliewagner.com
>Message-id: <3C00FF47...@charliewagner.com>
>
>
>
>John Wilkins wrote:
>
>> Charles Wagner <cha...@charliewagner.com> wrote:
>>
>> > Wade Hines wrote:
>> >
>> ....
>> > > between the density of the gas and its potential energy. What changes
>in
>> > > the model of a gravitationally collapsing gas cloud?
>> >
>> > There is no huge mass at the center which could explain the collapse.
>> >
>>
>> I can't believe you said that. The cloud must have a centre of gravity,
>> however, so if its angular momentum is not enough to prevent it, or
>> there are perturbing influences nearby, of course the gas is going to
>> collapse.
>
>The concept of "center of gravity" is used to describe the force on a body
>being
>acted on by a gravitational attraction from another source. For example, the
>center of gravity of the Leaning Tower of Pisa can be calculated with respect
>to
>the earth's gravitational attraction.
Actually the COM has nothing to do with an external gravitational field and can
be calculated independently of such.
I suggest you find a physics 101 text and start reading. For your benefit, I've
included a physics 101 type explantion below.
http://encarta.msn.com/index/conciseindex/07/00702000.htm?z=1&pg=2&br=1
If the LToP was beamed into space,
>outside
>of the earth's gravitational influence, I don't believe it would have any
>particular center of gravity.
Wrong.
At this point, One has to wonder if there is a basic concept Charles can't
mangle.
Richard Clayton
"I don't understand the basic concepts of science- AND I VOTE!"
Eric J. Korpela
Charles Wagner <cha...@charliewagner.com> wrote:
>First of all, there is not a shred of evidence that I'm aware of that stars
>form when the denser parts of the core of a cloud of interstellar dust
>collapses under the force of gravity. This is a well repeated assumption, but I
>see no evidence of any kind to justify such a claim. I can see no mechanism
>that would explain why an otherwise diffuse cloud of gas would begin to shrink
>and condense. Perhaps you can offer further insight.
Some basic evidence:
1. New stars are seen to be forming in dense areas of interstellar gas.
Do a web search on "Bok globule", "Herig-Haro object", "T-Tauri stars"
2. Basic physics indicates dense areas of interstellar gas should collapse
to form stars. The diffuse neutral interstellar medium exists in
essentially two phases in which heating essentially balances cooling.
Both the heating and cooling mechanisms have dependencies on temperature,
density. Over a range of temperatures there are two stable equilibruim
points representing the two phases. Perterbations in any of the parameters
can drive gas out of one phase and into the other. They can also drive
the gas out of equilibrium entirely.
For example, a density perterbation with scale length above the Jean's
length (look up "Jean's instability" online) can cause a start of a self
gravitational collapse of a cold cloud of about 10^4 solar masses.
The density increase causes increased radiative cooling in dense parts
of the cloud resulting in local temperature and pressure decreases resulting
in further density increases. Increased density also results in increased
molecule formation. Molecules increase the cooling rate by providing
optically thin radiative transitions. Energy released by the collapse
is radiated away. Molucules also locally decrease the pressure (by
decreasing particle number density). The end result is formation of
dense cores in the cloud that contine to cool and collapse. The end
result is somewhere between a few hundred and a few thousand stars.
To make a long story short, like evolution, star formation is an inevitable
consequence of reality.
> Secondly, when the cloud of gas begins to contract and condense (assuming
>that it does), the entropy of the gas cloud decreases.
Yes, at the expense of increasing the entropy of the interstellar radiation
field by a larger amount.
> Something had to "wind the clock" in the opposite direction from the
>normal "arrow of time". At some point, the entropy of the entire universe had
>to decrease, so that we could avail ourselves of the low entropy present in
>today's stars.
The "low" entropy state of current stars was acheived by increasing the entropy
of the rest of the universe. No magic necessary.
Eric
--
Eric Korpela | An object at rest can never be
kor...@ssl.berkeley.edu | stopped.
<a href="http://setiathome.ssl.berkeley.edu/~korpela">Click for home page.</a>
Charles Wagner
Richard Clayton wrote:
There was a time when I might have been intimidated by such remarks, but now I just
mostly ignore them.
The center of gravity considers the weight of an object being analyzed. Weight, of
course, is the force of gravity on an object. All of the weight is considered to be
acting at a single point, referred to as the center of gravity. I fail to understand
how an object can have a "center of gravity" in a weightless condition, such as in
interstellar space. Of course, all objects attract all other no matter what the
distance, but for reasonable analysis, an object in interstellar space, light years
from any other object, is essentially free from gravitational influence.
Of course, there is another reference point, called the center of mass and some
people confuse the two occassionally. Mass is a measurement of the amount of matter
an object contains, irrespective of any gravitational influences. There is a
theoretical difference between the two if the acceleration due to gravity is constant
over the mass distribution. In our space example, however, the acceleration due to
gravity for the object is zero. So it is more reasonable to use the term "center of
mass"
Now of course, there will be gravitational attraction between the various
particles in a cloud of gas. The prevailing theory says that star formation occurs
when the denser parts of the cloud core collapse under their own weight (gravity).
These cores then fragment into clumps which then form into protostars. An important
aspect of the prevailing theory is that gravity is the only force responsible for the
formation of the stars and the universe itself after the big bang. I don't feel that
there is sufficient evidence to state this unequivocally. There is some evidence that
other forces or processes might be involved, such as electromagnetism. One would also
wonder why, after 10-15 billion years since the big bang, star formation is still
apparently occurring and why there are large numbers of relatively young stars. If
star formation is an ongoing process, might this not suggest that there might be
other processes at work of which we are blisssfully unaware?
Regards, Charlie Wagner
http://www.charliewagner.com
>
Wade Hines
Charles Wagner wrote:
<<< snip >>
> There was a time when I might have been intimidated by such remarks, but now I just
> mostly ignore them.
Or even snip them.
> The center of gravity considers the weight of an object being analyzed.
Not really. The center of mass is, I believe, the same thing. This
is just as valid for inertial references as for gravitational ones.
If an object gains angular momentum, this relates to the axis upon
which it will spin. You don't need gravity to be a significant
factor for that to matter.
> Weight, of
> course, is the force of gravity on an object. All of the weight is considered to be
> acting at a single point, referred to as the center of gravity. I fail to understand
> how an object can have a "center of gravity" in a weightless condition, such as in
> interstellar space.
I believe others are rooting their understanding as the center of mass which
I believe is the same thing.
> Of course, all objects attract all other no matter what the
> distance, but for reasonable analysis, an object in interstellar space, light years
> from any other object, is essentially free from gravitational influence.
Isn't it better to deal directly with the magnitude than to dismiss it? The
point of significance is perhaps the magnitude of gravitational forces compared
with thermal energy.
> Of course, there is another reference point, called the center of mass and some
> people confuse the two occassionally. Mass is a measurement of the amount of matter
> an object contains, irrespective of any gravitational influences. There is a
> theoretical difference between the two if the acceleration due to gravity is constant
> over the mass distribution. In our space example, however, the acceleration due to
> gravity for the object is zero. So it is more reasonable to use the term "center of
> mass"
Now tell me the difference between the center of mass and the center of gravity?
There is a slight one based on gradations in the field but for most practical
senses, you couldn't tell a difference.
> Now of course, there will be gravitational attraction between the various
> particles in a cloud of gas. The prevailing theory says that star formation occurs
> when the denser parts of the cloud core collapse under their own weight (gravity).
> These cores then fragment into clumps which then form into protostars. An important
> aspect of the prevailing theory is that gravity is the only force responsible for the
> formation of the stars and the universe itself after the big bang. I don't feel that
> there is sufficient evidence to state this unequivocally.
But calculations bear it out. What weight do you give feelings over math?
> There is some evidence that
> other forces or processes might be involved, such as electromagnetism. One would also
> wonder why, after 10-15 billion years since the big bang, star formation is still
> apparently occurring and why there are large numbers of relatively young stars. If
> star formation is an ongoing process, might this not suggest that there might be
> other processes at work of which we are blisssfully unaware?
You might want to read up on things before going on like that. The answers
are rather well known.
Robin Levett
If you want to treat it in these terms:-
Take a particle on the edge of the cloud. Excluding forces from the
surroundings, the vector sum of the gravitational forces on that particle is
wholly toward the centre of mass of the cloud. The same is true of all
particles around the edge of the cloud. The particles one particle in from
the edge are acted upon by force whose vector sum is almost entirely toward
the centre of the cloud, since the only counteracting forces will be those
from the very few particles "outside" it, on the edge of the cloud.
The same is true, to a lesser extent, of all particles other than those at
the exact centre of mass of the cloud.
The only issue is whether the forces arising from gravity are sufficient to
overcome the "gas pressure". If the cloud has enough mass and is dense
enough, and hence the gravity due to the cloud great enough, they will be.
As has been pointed out elswhere on this thread, the Sun is simply a cloud
mostly of hydrogen in which the gas pressure and gravity are roughly equal.
--
________________________________________________________________
Robin Levett
rle...@ibmrlevett.uklinux.net
(address munged by addition of Big Blue)
Atheist = knows of and uses Occam's Razor
Agnostic = knows of but isn't sure whether to use Occam's Razor
Fundy = what's Ockam's erasure?
___________________________________________________