Standard Cosmology and Thermodynamics

[Erasmus00]

As time t tends to infinity, in an expanding model, temperature T approaches 0 kelvins), so what happens to entropy S?

 

You could ask the same question for any gas/fluid expanding. I.e. as a gas undergoes adiabatic expansion, as t gets large T gets small. Does this mean entropy is decreasing?

-Will

[coldcreation]

You could ask the same question for any gas/fluid expanding. I.e. as a gas undergoes adiabatic expansion, as t gets large T gets small. Does this mean entropy is decreasing?

-Will

 

Certainly.

 

It means that entropy is decreasing. I can only conclude that the second law is violated within the context of the Lambda-CDM model (note: two of the Friedmann models had the same problem, the open and critical models).

 

Will entropy in an expanding universe ever reach zero? Probably not. Entropy will tend to zero with time t. But either way, the second law still seems to be violated.

 

 

Is there something I'm missing? How could this be?

 

 

 

 

CC

[coldcreation]

I’m unsure if I see the problem CC is hinting at, but I do see a problem.

 

Good call. This is one of the problems. The other related problem (upon which I must expand in a later post) is the author(s) attempt to use the Casimir effect to justify the "something can not come out of nothing" claim, and the non-violation of conservation laws, when in actual fact, the Casimir effect (or Casimir-Polder force) is simply "a physical force exerted between separate objects due to resonance of all-pervasive energy fields in the intervening space between the objects."

 

Essentially, Casimir force is due to ground-state energy fluctuations (zero-point energy, ZPE and zero-point fluctuations). This effect (or force) is exceedingly small.

 

In sum, the author(s) are guilty of twisting the evidence to support an argument that really has little, if anything at all, to do with the first law of thermodynamics, and certainly nothing to do with the creation of the universe.

 

I can see a problem with this text, from Evidence for the Big Bang:Assuming it is referencing pair production followed promptly by pair annihilation, I see a glaring problem with this statement: an electron, s positron, and s photon do not appear, then annihilate, rather a photon produces an electron and a positron, the electron and positron annihilate, producing a photon with the energy and momentum of the original, diagrammatically (without the traditional pretty wavy lines, which I haven’t worked out how to quickly enter in LaTeX :hihi: ):

 

Is that a Feynman drawing?

 

 

I assume this is just a proofreading mishap by the authors, not an assertion of a strange claim.

 

I would have assumed the same, except that there are many examples in the link above of assertions that are founded on spurious interpretations and chimerical extensions of known physics. If any one doubts the latter, I can provide the full list.

 

 

More profoundly, the paragraph following this,contradicts my understanding of “the universe is a vacuum fluctuation, one of those things that just happens from time to time” hypotheses such as those of Edward Tryon, which has been discussed in these forums, such as these posts in the “Origin of Universe…” thread.

 

Thanks for providing that link. Interesting exchange.

 

 

The essence of these “free lunch” origin hypotheses is that the classical conservation laws arise from underlying quantum physical “reality” only because they are very likely – but not inevitable.

 

 

It seems to me, judging from empirical evidence and statement of the divers laws of thermodynamics, that at absolute zero the universe would have been in the lowest energy state with zero entropy (or very nearly zero).

 

Recall that it is commonly assumed (though the big bang has been removed from the BBT) the universe began with the annihilation of matter with antimatter. Both made contributions that enter the energy density with different signs, on one hand positive and on the other negative, so that the total magnitude of the energy of the universe (or the physical vacuum) is very small or zero, hence the free lunch.

 

The author’s satisfaction associated with this quasi-mutual compensation has been voiced throughout his manuscript, even though there is no observational support, no evidence, verification, confirmation, or proof possible (even in principle).

 

[Edited to ask:] So the question is, if the state of lowest entropy occurs only at or near zero kelvins (see the third law of thermodynamics), how is it possible for entropy to have been very low following a big bang event, a state, by definition, of highest energy and temperature?

 

 

 

Though so speculative as to be, IMHO, more in the philosophical magisterium than the scientific, and not part of or well-integrated with the Big Bang model, such hypotheses, particularly their lack of outright rejection by the mainstream physics community, illustrate the non-absolute nature of classical conservation laws under current best theory.

 

 

Though, astutely, there is no mentioning from where originated the energy (the universe, like a virgin giving birth, sprang from nothing). This form of creation ex nihilo has been dubbed the ultimate “free lunch.” But it loses its flavor somehow.

 

 

“Grilling, broiling, barbecuing - whatever you want to call it - is an art, not just a matter of building a pyre and throwing on a piece of meat as a sacrifice to the gods of the stomach.” James Beard. (1974)

 

 

 

 

CC

[Erasmus00]

You could ask the same question for any gas/fluid expanding. I.e. as a gas undergoes adiabatic expansion, as t gets large T gets small. Does this mean entropy is decreasing?

 

Certainly.

 

Not at all. By definition, the adiabatic nature of the expansion means entropy is a constant, even as the temperature falls. How is this possible? Entropy ALSO depends on volume.

 

Hence, even though an object is cooling quickly, if the volume is very large (and growing) entropy can increase. Even very close to absolute zero, a very, very large volume could lead to a huge entropy.

-Will

[Little Bang]

CC, you made this statement above, "

Recall that it is commonly assumed (though the big bang has been removed from the BBT) the universe began with the annihilation of matter with antimatter. " Where did the matter and anti-matter come from that started the universe?

[Erasmus00]

It seems to me, judging from empirical evidence and statement of the divers laws of thermodynamics, that at absolute zero the universe would have been in the lowest energy state with zero entropy (or very nearly zero).

 

Please recall that if EVERYTHING is at the same temperature, the entropy of a system is at its (current) maximum. I.e. if a system is at an entirely uniform temperature, everything is in thermal equilibrium, and entropy is at a maximum (or else things can't change). As long as the temperature is not EXACTLY 0, entropy can be very high in a very large system.

 

Recall that it is commonly assumed (though the big bang has been removed from the BBT) the universe began with the annihilation of matter with antimatter. Both made contributions that enter the energy density with different signs, on one hand positive and on the other negative, so that the total magnitude of the energy of the universe (or the physical vacuum) is very small or zero, hence the free lunch.

 

I don't think this is, at all, a common assumption. BOTH matter and antimatter carry energy. Anti-matter does NOT have a negative energy density.

 

So the question is, if the state of lowest entropy occurs only at or near zero kelvins (see the third law of thermodynamics), how is it possible for entropy to have been very low following a big bang event, a state, by definition, of highest energy and temperature?

 

I think you are making the mistake of assuming both energy and entropy are directly proportional to temperature. This is not true. Temperature is defined (thermodynamically at least) so that [math] \frac{1}{T} = \frac{dS}{dU}[/math] where S is entropy and U is the energy. These strict equivalences you are making aren't true. Now, if volume is very small, then even if temperature is quite high, entropy can still be low.

-Will

[coldcreation]

...By definition, the adiabatic nature of the expansion means entropy is a constant, even as the temperature falls. How is this possible? Entropy ALSO depends on volume.

 

This special case you mention is like balancing a pencil on its point. Another fine-tuning problem (like a free lunch) emerges.

 

Hence, even though an object is cooling quickly, if the volume is very large (and growing) entropy can increase. Even very close to absolute zero, a very, very large volume could lead to a huge entropy.

 

We were discussing gas/fluids, now you refer to an "object." I would be interested in seeing your source. According to all of mine, entropy tends to zero as temperature tends to zero K.

 

You write "even very close to absolute zero:" how close? Reference?

 

 

The third law of thermodynamics can be stated: The entropy of all systems and of all states of a system is zero at absolute zero.

 

In this post there are a variety of statements of the third law. This law is absolutely beautiful.

 

 

 

The problem I see now is basic. If in an expanding universe entropy increases, as time tends to infinity and temperature tends to zero, then in principle there will come a time when temperature reaches zero kelvins and entropy reaches a maximum.

 

So either the third law of thermodynamics is in error, or the concept of entropy increase in an expanding universe is untenable. If I had to discard one option it would certainly not be the third law.

 

 

CC

[coldcreation]

Please recall that if EVERYTHING is at the same temperature, the entropy of a system is at its (current) maximum. I.e. if a system is at an entirely uniform temperature, everything is in thermal equilibrium, and entropy is at a maximum (or else things can't change). As long as the temperature is not EXACTLY 0, entropy can be very high in a very large system.

 

This state is hypothetical. It can easily be shown that this state could never exist (even near infinity in an expanding universe). There will always be change, always a collision, always ZPE and ZPF, always Casimir force, etc.

 

 

 

I don't think this is, at all, a common assumption. BOTH matter and antimatter carry energy. Anti-matter does NOT have a negative energy density.

 

It was for several decades. Now the encounter between matter and anti-matter has been removed from the theory.

 

 

 

I think you are making the mistake of assuming both energy and entropy are directly proportional to temperature. This is not true.

 

Actually no, I did not assume that.

 

Look what is written here though:

"Indeed' date=' as shown by Kolb & Turner, the entropy of the early universe was extremely low. This makes sense if one remembers that, in the very early stages of the universe, the distribution of matter and energy was very, very ordered, as demonstrated by the uniformity of the CMBR. As such, [b']one could characterize the entire distribution of matter and energy in the universe with a single number (the temperature[/b]) to a very good approximation."

[My bold]

 

What gives?

 

 

 

CC

[Erasmus00]

This special case you mention is like balancing a pencil on its point. Another fine-tuning problem (like a free lunch) emerges.

 

This is a special case-entropy stays the same. Much more general, for spontaneous gas/fluid expansion, entropy goes up and temperature goes down. See Reif, Sethna, Landau and Lifshitz, or pretty much any thermo book. Again, entropy up, temperature down.

 

We were discussing gas/fluids, now you refer to an "object." I would be interested in seeing your source. According to all of mine, entropy tends to zero as temperature tends to zero K.

 

I meant object in an extremely general sense. Entropy is 0 at absolute 0, but how fast it approaches 0 depends on many, many factors. To see that entropy depends on volume, look up (for instance) the entropy of an ideal gas.

 

[math] S \propto ln \left(VT^{\alpha}\right) [/math]

 

where $\alpha$ is the specific heat at constant volume (ideally 3/2 for a monoatomic gas). So for very small temperatures, we can have very large entropies.

 

The reasoning is this: temperature determines (in a loose sense) the number of available states. I.e., lower temperature means your confined to less and less energy states, and as such the entropy is lower (less available states).

 

However, by increasing the volume, we can increase the number of states available at low energies (hence, increasing the entropy).

 

You write "even very close to absolute zero:" how close? Reference?

 

Arbitrarily close for many systems. See Landau and Lifschitz thermodynamics book.

 

The third law of thermodynamics can be stated: The entropy of all systems and of all states of a system is zero at absolute zero.

 

This is nice, as it allows a solid reference for entropy. However, its not actually always true. Glasses, for instance, can violate the third law. Also consider that the law says nothing about how fast it moves away from 0 at a given temperature. Now, if you hold EVERYTHING ELSE constant and lower temperature, of course entropy would go down. However, we are considering a volume expansion as well as a temperature reduction. Entropy increases with increasing volume.

 

The problem I see now is basic. If in an expanding universe entropy increases, as time tends to infinity and temperature tends to zero, then in principle there will come a time when temperature reaches zero kelvins and entropy reaches a maximum.

 

Not true. Temperature can get arbitrarily close to 0 as volume gets arbitrarily close to infinity. Depending on how temperature and volume scale you could have entropy staying constants, decreasing, or increasing.

 

So either the third law of thermodynamics is in error, or the concept of entropy increase in an expanding universe is untenable. If I had to discard one option it would certainly not be the third law.

 

First, there are already exceptions to the third law (glasses). Also, again, in a general gas/fluid expansion, entropy goes up.

 

This state is hypothetical. It can easily be shown that this state could never exist (even near infinity in an expanding universe). There will always be change, always a collision, always ZPE and ZPF, always Casimir force, etc.

 

If everything is at the same temperature, by definition, entropy is maximized. Hence, macroscopically, the system doesn't change. This is not hypothetical. Collisions still occur, but things move forward as often as they move back.

 

It was for several decades. Now the encounter between matter and anti-matter has been removed from the theory.

 

If anything, what would be assumed is that both matter and antimatter COME OUT from the big bang (in equal quantities via pair creation events). This is NOT the same as matter and antimatter collision CAUSING the big bang. Your starting premise (matter has positive, antimatter negative energy density) is incorrect and was never believed to be correct.

 

As to your quote about temperature defining the early universe. This is because most of the other state variables are extremal (either small or large). It is not true in general that temperature is the only important variable.

-Will

[modest]

You could say that a closed system of ideal gas expanding must do pressure-volume work, or that it is becoming more homogeneous over time and thus entropy is increasing to a maximum as time approaches infinity.

 

Or, you could say that such a system is approaching 0K as time approaches infinity and its entropy is lost.

 

Or, you could consider both aspects and say that no certain statement can be made about such a system as it approaches infinites.

 

I guess there are prominent people like penrose that think they can use entropy to say what came before the big bang and other such far-reaching things. I think to do so is probably a mistake. For instance: who on earth can say if the universe is an isolated system? If such a simple thermodynamic principle cannot be stated with any certainty on a universal scale then IMHO we error in making such turgid conclusions on its principles alone.

 

On the other hand: I do think it could be useful to ask a question of less scale and scope: Does an expanding and cooling universe violate the laws of thermodynamics over any finite period of time given our observations? Maybe this could be answered with more credence and consensus. But, no - probably not.

 

-modest

[LaurieAG]

Hi modest,

 

You could say that a closed system of ideal gas expanding must do pressure-volume work, or that it is becoming more homogeneous over time and thus entropy is increasing to a maximum as time approaches infinity.

 

Or, you could say that such a system is approaching 0K as time approaches infinity and its entropy is lost.

 

Or, you could consider both aspects and say that no certain statement can be made about such a system as it approaches infinites.

 

I guess there are prominent people like penrose that think they can use entropy to say what came before the big bang and other such far-reaching things. I think to do so is probably a mistake.

 

If, like Roger Penrose and Stephen Hawking in 'The Nature of Time and Space', your modelling techniques don't preclude infinity, you can have a theoretical model where infinity is wholly included within the model, with plenty of room to spare (because infinity isn't the border of your model).

[Little Bang]

Modest, you said"For instance: who on earth can say if the universe is an isolated system?" I like this better, who on earth can say if the universe is NOT an isolated system?

[Mike C]

.

To begin the discussion, the objective of which is to pinpoint the problems and to highlight some of the possible solutions associated with modern cosmology and thermodynamics.

Does anyone see the problem that emerges here?

 

I did not read your URLs but decided to answer anyway.

 

Yes. In todays physics, we have had Laws of Conservation formulated and numerous experiments and observations done in the field of astronomy.

 

The problem here is that 'power' science (Latin church) has established itself as the teacher of science in general because of its dominance in the religious sector as well. Therefore, it has established restrictions of free opinions of same while ignoring the truth as they did back in the 15th century of Galileos observations and experiments.

 

Here the problem is more evident. Can anyone pinpoint it?

Note: in the entire manifesto linked above, there is no mention of the third law of thermodynamics. Does anyone know why?

 

The 2nd Law simply can be summed up to ...'Heat cannot flow from cold to hot but only from hot to cold'. So in a closed system, it will reach a temperature of 'equalibrium'.

 

The 3rd Law , I do not understand myself but my explanation is that equalibrium can only be achieved at 'absolute zero'.

 

Since the CMBR temperature has a slight deviation of 7/100,000 of a Kelvin, it has not yet achieved complete equalibrium, but it is very close to AZ.

 

Mike C

 

 

 

CC

[Little Bang]

CC, I honestly don't know but if it is true that an electron and positron can spontaneously appear from vacuum fluctuations, annihilate, and create a photon wouldn't that be adding energy to the total system from nothing?

[coldcreation]

CC, I honestly don't know but if it is true that an electron and positron can spontaneously appear from vacuum fluctuations, annihilate, and create a photon wouldn't that be adding energy to the total system from nothing?

 

Good question Little Bang.

 

I would say that there is simply a conversion from potential energy (stored in the ground-state vacuum reservoir in the form of zero-point energy and zero-point fluctuations, ZPE, ZPF) to available energy. In that way the conservation of energy, or first law of thermodynamics is not violated.

 

So there would be no spontaneous creation of energy out of nothing, just as there would be no destruction of energy, just a trasformation. The total energy of the system remains the same.

 

 

CC

[Little Bang]

CC your answer sure seems like an attempt at a snow job to me.

[Mike C]

CC your answer sure seems like an attempt at a snow job to me.

 

Ha ha.

That kind of stuff originates with mathematical creations.

 

Mike C