Freethought & Rationalism Archive

HRG · 07-31-2002, 01:55 AM

Quote:

Originally posted by DNAunion:
[QB]

DNAunion: What about an "IDist"?

Zeroth law of thermodynamics: If A is in thermal equlibrium with B, and B is in thermal equilibrium with C, then A will be in thermal equilbrium with C if they come into contact.

First law of thermodynamics: Total energy (well, total mass/energy) of the Universe (or any isolated system) is constant/conserved: energy can neither be created nor destroyed, but can be changed into other forms (including into mass).

Second law of thermodynamics: Entropy tends towards a maximum: the total entropy of the Universe (or any isolated system) increases with every physical change that takes place.

It should be noted that that's not the way physicists formulate the 1. and 2. LoT (at least when they are talking among themselves). It is by no means assured that "the total energy or entropy of the universe" is a meaningful concept; in some cosmological models, they aren't.

Thus a careful formulation of the laws always speaks about a system and the energy/entropy transport through its boundary.

Quote:

Third law of thermodynamics: Can't remember this one off the top of my head...but I think it is derived from studies on different gasses and states that all molecular motion ceases at absolute zero (-273.15 degrees C, or 0 kelvin).

Not quite. It states essentially that you cannot reach absolute zero by a finite process.

Regards,
HRG.

Starboy · 07-31-2002, 05:53 AM

Quote:

Originally posted by seanie:


Isn't it all three?

The "Laws" of nature is a throwback to the pre 1900's. Physicists stopped thinking that way when they realized that they would have to change the so called laws after discovering Quantum Mechanics and General Relativity. At this time there are very good indications that GR may be in for some big changes if not outright replacement in the future. If you are interested look into the negative results of gravity wave experiments and MOND.

Starboy

Lentic Catachresis · 07-31-2002, 06:15 AM

I dont see how entropy can be talked about in reference to any 'living' systems without the mention of enthalpy. These are the two main driving forces in any chemical system, and in many cases they oppose each other.

For instance if water and oil are mixed together they always separate into two distinct layers rather than mixing. Is this a violation of the 2LOT? Well, no. The chemical interactions between water and oil have a greater influence over the system than entropy does.

This reasoning also applies to many areas of how living systems work e.g. in relation to how a polypeptide chain instantly turns into a highly specifically shaped protein.

seanie · 07-31-2002, 06:17 AM

My understanding of what Science means by laws, facts and theories really comes from reading the Talk.Origins Archive. I don't have a scientific background myself.

They have quotes from the NAS;

'Laws are generalizations that describe phenomena, whereas theories explain phenomena. For example, the laws of thermodynamics describe what will happen under certain circumstances; thermodynamics theories explain why these events occur. Laws, like facts and theories, can change with better data. But theories do not develop into laws with the accumulation of evidence. Rather, theories are the goal of science.'

Also;

'Theories are explanations of natural phenomena, and laws are descriptions of natural phenomena.'

So I would have regarded Thermodynamics as both a Theory and a set of Laws.

And since Thermodynamics as a Theory and as a set of Laws appears to be correct I'd also consider it a Fact.

Reasonable?

DNAunion · 07-31-2002, 07:39 AM

Quote:

DNAunion: What about an "IDist"?

Zeroth law of thermodynamics: If A is in thermal equlibrium with B, and B is in thermal equilibrium with C, then A will be in thermal equilbrium with C if they come into contact.

First law of thermodynamics: Total energy (well, total mass/energy) of the Universe (or any isolated system) is constant/conserved: energy can neither be created nor destroyed, but can be changed into other forms (including into mass).

Second law of thermodynamics: Entropy tends towards a maximum: the total entropy of the Universe (or any isolated system) increases with every physical change that takes place.

Quote:

HRG: It should be noted that that's not the way physicists formulate the 1. and 2. LoT (at least when they are talking among themselves).

It is by no means assured that "the total energy or entropy of the universe" is a meaningful concept; in some cosmological models, they aren't.

DNAunion: Well, let me back up a few of my usages (which were off the top of my head).

PS: I just KNEW someone would challenge my statements, no matter how nit picky they had to get. So I brought my college physics book along with me today!

Quote:

”Zeroth law of thermodynamics: If bodies A and B are separately in thermal equilibrium with a third body, C, then A and B will be in thermal equilibrium with each other if placed in thermal contact.” (Raymond A. Serway & Jerry S. Faughn, College Physics: Fifth Edition, Harcourt College Publishers, 1999, p314)

DNAunion: But no one complained about that one (though no one else even mentioned it when listing the laws of thermodynamics).

Concerning the second law and the Universe…

Quote:

”The concept of entropy reached a position of even more significance when it was found that the entropy of the Universe increases in all natural processes. This is yet another way of stating the second law of thermodynamics.” (bold in original, Raymond A. Serway & Jerry S. Faughn, College Physics: Fifth Edition, Harcourt College Publishers, 1999, p388)

Quote:

”For example, the spacing between trees in a natural forest is quite random; if you were to discover a forest where all the trees were equally spaced, you could conclude that it was a planted forest [ah, a design inference!!!!]. … We can express the results of such observations by saying that a disorderly arrangement is much more probable than an orderly one if the laws of nature are allowed to act without interference. … One of the main products of this approach [statistical mechanics] is the conclusion that isolated systems tend toward greater disorder, and entropy is a measure of that disorder. … The second law of thermodynamics is really a statement of what is most probable rather than what must be. … Even more generally, the second law of thermodynamics defines the direction of time for all events as the direction in which the entropy of the universe increases. Although conservation of energy is not violated if energy spontaneously flows from a cold object … to a hot object …, the even violates the second law because it represents a spontaneous increase in order, and it also violates everyday experience.” (all bold in original, Raymond A. Serway & Jerry S. Faughn, College Physics: Fifth Edition, Harcourt College Publishers, 1999, p390, 391-391)

Quote:

”Finally, note once again that the statement that entropy must increase in all natural processes is true only for isolated systems. There are instances in which the entropy of some system decreases, but with a corresponding net increase in entropy for some other system. When all systems are taken together to form the Universe, the entropy of the Universe always increases.” (italics in original, Raymond A. Serway & Jerry S. Faughn, College Physics: Fifth Edition, Harcourt College Publishers, 1999, p393)

DNAunion: And concerning the first law and conservation of energy…

Quote:

”The first law of thermodynamics is the generalization of the law of conservation of energy that includes heat transfer.” (italics in original, Raymond A. Serway & Jerry S. Faughn, College Physics: Fifth Edition, Harcourt College Publishers, 1999, p394)

Quote:

”When the principle of conservation of energy was first introduced in Chapter 5, it was stated that the mechanical energy of a system is constant in the absence of nonconservative forces, such as friction. That mechanical model did not encompass changes in the internal energy of the system. We now broaden our scope to use the term principle of conservation of energy for a generalization encompassing possible changes in internal energy. This is a universally valid law that can be applied to all kinds of processes. Furthermore, it provides a connection between the microscopic and macroscopic worlds. The result will be the first law of thermodynamics.” (bold and italics in original, Raymond A. Serway & Jerry S. Faughn, College Physics: Fifth Edition, Harcourt College Publishers, 1999, p378)

DNAunion: You then noted the problem with my "Defintion" of the 3rd law.

Quote:

DNAunion:

Third law of thermodynamics: Can't remember this one off the top of my head...but I think it is derived from studies on different gasses and states that all molecular motion ceases at absolute zero (-273.15 degrees C, or 0 kelvin).

Quote:

DRH: Not quite. It states essentially that you cannot reach absolute zero by a finite process.

DNAunion: Well, when I got home after posting, I checked and the definition I found was almost exactly that which someone else posted (darn, I still can’t remember the exact definition but it is along the lines of, “third law of thermodynamics: the entropy of a perfect, pure crystal at 0 kelvin is 0.&#8221

Anyway, the statements I made are fully acceptable (though in rough off-the-top-of-my-head form).

Also, who said we were talking cosmology? We aren't. And technically, we aren't even talking about physics itself. We are talking about bioenergetics.

[ July 31, 2002: Message edited by: DNAunion ]

Starboy · 07-31-2002, 07:56 AM

Quote:

Originally posted by seanie:
My understanding of what Science means by laws, facts and theories really comes from reading the Talk.Origins Archive. I don't have a scientific background myself.

They have quotes from the NAS;

'Laws are generalizations that describe phenomena, whereas theories explain phenomena. For example, the laws of thermodynamics describe what will happen under certain circumstances; thermodynamics theories explain why these events occur. Laws, like facts and theories, can change with better data. But theories do not develop into laws with the accumulation of evidence. Rather, theories are the goal of science.'

Also;

'Theories are explanations of natural phenomena, and laws are descriptions of natural phenomena.'

So I would have regarded Thermodynamics as both a Theory and a set of Laws.

And since Thermodynamics as a Theory and as a set of Laws appears to be correct I'd also consider it a Fact.

Reasonable?

Yes that is the current redefinition but I prefer to not use the word all together. Just like the word truth, I think it just confuses the issues. Science is much more than a collection of facts and theory it is a way to understand how the universe works. Spouting science as law or truth makes it easy for a Christian to change the subject to truth against truth rather than addressing the very real problem that science has very good explanations whereas religion does not.

Starboy

[ July 31, 2002: Message edited by: Starboy ]

Principia · 07-31-2002, 08:09 AM

Quote:

DNAunion: Well, when I got home after posting, I checked and the definition I found was almost exactly that which someone else posted (darn, I still can�t remember the exact definition but it is along the lines of, �third law of thermodynamics: the entropy of a perfect, pure crystal at 0 kelvin is 0.�

Hmm... well let me refresh your memory, little doggie.

Nernst (1905): As T -> 0K, dS -> 0 J/K for all isothermal processes in condensed states.

Planck (1911): As T -> 0K, S -> 0 for every chemically homogeneous substance in perfect crystalline state.

[Note the -> limit signs, because they imply:]

Corollary: It is impossible to decrease the temperature of any system to T = 0K in any finite number of steps.

Quote:

Anyway, the statements I made are fully acceptable (though in rough off-the-top-of-my-head form).

Aww... so defensive. Who honestly cares? In any case, here's a good explanation of why your original conception of 3rd Law is <a href="http://newton.dep.anl.gov/askasci/phy99/phy99194.htm" target="_blank">incomplete</a>.

Quote:

Also, who said we were talking cosmology? We aren't. And technically, we aren't even talking about physics itself. We are talking about bioenergetics.

ROFLMAO. Try again.

[ July 31, 2002: Message edited by: Scientiae ]

scigirl · 07-31-2002, 08:32 AM

Quote:

Originally posted by Scientiae:
Hmm... well let me refresh your memory, little doggie.

Heh, I hope you are referring to 'Creation's Terrier' here! Let's keep the insults to a minimum if we can (unless we are talking about Kent Hovind, in which case insults are required! )

Thanks guys,

scigirl

Principia · 07-31-2002, 08:35 AM

Quote:

Originally posted by scigirl:

Heh, I hope you are referring to 'Creation's Terrier' here! Let's keep the insults to a minimum if we can (unless we are talking about Kent Hovind, in which case insults are required! )

Thanks guys,

scigirl

Oh come on, scigirl. It all depends on how you read it... I thought it sounded endearing.

Anybody gotta bone?

Undercurrent · 07-31-2002, 12:37 PM

Quote:

Originally posted by DNAunion:

Second, as correctly stated originally, when death does occur, entropy does increase. (Yes, total entropy does increase in all natural processes, but here I am limiting the scope to just the entity that died. Its entropy has increased.)

I don't know about you, but I've never seen it proved that any process that causes the death of an organism also increases in entropy of that organism. I imagine that an organism that died by being flash-frozen would become a corpse with lower entropy than the original living organism.

m.

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07-31-2002, 06:15 AM	#23
Lentic Catachresis Junior Member Join Date: Aug 2001 Location: UK Posts: 26	I dont see how entropy can be talked about in reference to any 'living' systems without the mention of enthalpy. These are the two main driving forces in any chemical system, and in many cases they oppose each other. For instance if water and oil are mixed together they always separate into two distinct layers rather than mixing. Is this a violation of the 2LOT? Well, no. The chemical interactions between water and oil have a greater influence over the system than entropy does. This reasoning also applies to many areas of how living systems work e.g. in relation to how a polypeptide chain instantly turns into a highly specifically shaped protein.

07-31-2002, 06:17 AM	#24
seanie Veteran Member Join Date: Jul 2002 Location: Edinburgh. Scotland Posts: 2,532	My understanding of what Science means by laws, facts and theories really comes from reading the Talk.Origins Archive. I don't have a scientific background myself. They have quotes from the NAS; 'Laws are generalizations that describe phenomena, whereas theories explain phenomena. For example, the laws of thermodynamics describe what will happen under certain circumstances; thermodynamics theories explain why these events occur. Laws, like facts and theories, can change with better data. But theories do not develop into laws with the accumulation of evidence. Rather, theories are the goal of science.' Also; 'Theories are explanations of natural phenomena, and laws are descriptions of natural phenomena.' So I would have regarded Thermodynamics as both a Theory and a set of Laws. And since Thermodynamics as a Theory and as a set of Laws appears to be correct I'd also consider it a Fact. Reasonable?

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