Standard Cosmology and Thermodynamics

[coldcreation]

.

 

 

 

In this thread, Standard Cosmology and Thermodynamics, as opposed to a thread entitled Thermodynamics and Cosmology it will be discussed the standard model (or Lambda-CDM) and thermodynamic implications within that framework.

 

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.

 

 

In this work: Evidence for the Big Bang it is written:

 

The simple statement "something can not come out of nothing" is' date=' in itself, not very convincing. From quantum field theory, we know that something does indeed come from nothing: to wit, "vacuum fluctuations". In the simplest case, an electron, a positron and a photon can appear effectively out of nowhere, exist for a brief time and then annihilate, leaving no net creation of mass or energy. Experimental support for this sort of effect has been found from a number of different experiments. See, for instance, the Wikipedia page for the Casimir effect.

 

The common point for all of these effects is that they do not violate any known conservation laws of physics (e.g., the conservation of energy, momentum, and charge). Something can indeed come out of nothing as long as these conservation laws permit this. But people often argue that the Big Bang theory violates the conservation of energy (which is essentially the first law of thermodynamics).[/quote']

 

Does anyone see the problem that emerges here?

 

 

 

Secondly, in the next section related to the second law it is written:

 

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, one could characterize the entire distribution of matter and energy in the universe with a single number (the temperature) to a very good approximation. Compare that to the universe we see now, filled with complicated, disorderly distributions of galaxies, stars and gas. The amount of entropy in these objects is enormous (recall our earlier discussion about the lack of coherent orbits for stars in elliptical galaxies and galaxies in galaxy clusters). Hence, the idea that the entropy of the universe has somehow decreased in violation of the second law of thermodynamics is largely nonsensical.

 

Given that the entropy of the universe has only increased, how did it get such a low entropy when it came into being? At the current time, this is still an open question in cosmology. Obviously, many of the problems we outlined in the previous section regarding time before the Big Bang and the applicability of physical laws at the origin of the universe come into play here, but there is, as of yet, no simple answer.[/quote']

 

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?

 

 

 

 

CC

[LaurieAG]

Hello CC,

 

Does anyone see the problem that emerges here?

 

Firstly, if you monitor a square meter of vacuum over a period of time and a high energy wave passes through the metered area, what type of fluctuation would you expect to see? Could you say that this fluctuation appeared out of nowhere and then went nowhere merely because you ignore everything outside the monitored area?

 

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

 

Most modern cosmological theories exclude the area outside the singularity point of the Big Bang as being part of the 'universe'.

 

The problems lie with using a closed system to model part of an open system.

[Little Bang]

How would we know if it was closed or open, we can't see anything outside the BB which would include us?

[LaurieAG]

How would we know if it was closed or open, we can't see anything outside the BB which would include us?

 

There are currently models and observations of other (close to) singularities called black holes that have a similar set-up to what you call the big bang.

 

If we can occupy a position (i.e. an observation point on Earth) external to a (close to) singularity point called a black hole (as everybody who theorises about black holes does), why cannot there also be external areas to the other (close to) singularity point called the big bang?

 

You cannot have it both ways and the open system is the only model that includes the entire universe (and when it does it can be treated as a closed/isolated system).

[coldcreation]

A closed system can exchange heat and work with its environment and in so doing goes through changes in energy, but does not exchange mass with its environment; its mass remains constant. In another way, a closed system does not exchange mass with the surroundings. Heat and work may be exchanged with the surroundings and thereby induce changes in energy and volume. Other properties may change but the mass remains constant.

 

An open system can exchange mass with its environment, as well as heat, work and energy, i.e., it is a system that communicates with the environment by exchanging energy and matter.

 

I think we can safely assume that the laws of thermodynamics should apply to this universe, whether one condiders the universe an open or closed system.

 

True, the second law is always based on derivations for closed systems. It has been shown that the value of entropy depends on the state of a substance. This state is independent of whether the substance is static (stationary) and constitutes a closed system or is flowing through an open system (Kyle, 1984). It follows that the principle of entropy nondecrease applies to the open-primary-system as well.

 

 

Note: the concept of a closed system is not to be confused with a closed universe: A cosmological model in which space has a finite dimension, with positive spherical spacetime curvature. This concept leads to a ‘big crunch’ (and has been ruled out by observations).

 

It should be noted, too, that after having realized the fact that black holes were incompatible with the laws of thermodynamics, Bardeen, Carter and Hawking co-borrowed or appropriated a concept that was much more than suggestive. The result would be called the ‘four laws of black hole mechanics.’ These laws are stated almost precisely in the same manner as the laws of thermodynamics, but with surface gravity in the place of temperature, and entropy replaced by ‘area.’ Aside from switching the words around, there is a fundamental difference between the two sets of laws: The laws of thermodynamics are based on empirical facts, while the ‘laws of BH dynamics’ are based on extrapolations, conjecture, mathematical aberrations.

 

And so black holes are beyond the scope of this thread.

 

 

 

CC

[Pluto]

Hello CC

 

I take my hat off for you.

 

Re:

 

Evidence for the Big Bang

 

The information on that link is very limited and mixed up thoughts.

[Little Bang]

CC, have you ever considered the possibility that your view of the BB may by some astronomically small amount be wrong? Let's look at a hypothetical murder. The detective assigned examines all the clues and decides the identity of the killer. A second detective examines the clues and proves beyond doubt that the first detective was wrong. If the first detective never looks at the clues again he will go to his death believing he was right the first time. The point is that we are all a lot like the first detective. We hate having to re-examine things that we have already decided to be a truth. If all of our conclusions about the data we have collected over the years were true we would already have a GUT. So it is pretty obvious that there are some errors in our conclusions. I don't have a solid opinion about the BB but I fell the evidence supports some type of beginning.

[coldcreation]

CC, have you ever considered the possibility that your view of the BB may by some astronomically small amount be wrong? ...[snip]... If all of our conclusions about the data we have collected over the years were true we would already have a GUT. So it is pretty obvious that there are some errors in our conclusions. I don't have a solid opinion about the BB but I fell the evidence supports some type of beginning.

 

Hi Little Bang,

 

I know you dislike when I respond with a full page disertation, so I will keep it short.

 

This thread is not about my view of the BBT. The aim is to see if the laws of thermodynamics are embraced within the BBT (or lambda-CDM as the new post-1998 standard model is called), i.e., if they hold valid for all times t within the model. And/or, to determine if the laws of thermodynamics are violated at some time t within the standard model.

 

Basically, the beginning, the big bang itself—at which time not just thermodynamics, but all of physics brakes down—has been removed from the BBT. So starting from the Plank time/scale it would be interesting to here argument for or against the validity of the laws intrinsic to the model.

 

Ultimately, empirical evidence should determine the outcome of the investigation, not my opinion.

 

 

Notwithstanding, regarding your phrase: "evidence supports some type of beginning," the old vision offered by modern cosmology (big bang event included) makes it inevitable now (that it has been removed) to see an enormous question mark suspended around the vacuous concept of “origin” (where physics breaks down) and the vital responsibility it might assume in our conception of both the underpinning of physical science (thermodynamics included) and the nature of the universe in its entirety.

 

 

 

 

 

CC

[LaurieAG]

Hello CC,

 

And so black holes are beyond the scope of this thread.

 

So, all singularities are excluded from the BBT. Excellent.

 

BTW, the closed and open system definitions got me thinking about Einsteins old Cosmological Constant idea. If the empty vacuum surrounding the close to singularity point of the BB imparts some type of pressure on the border between the mass and the vacuum, the vacuum pressure would vary as the density of the mass contained in the BB reduced as the volume expanded. This doesn't appear to be reflected in the strict definitions used in astrophysics (where energy but not mass can be transferred), a grey area perhaps?

 

I also think that, due to scaling problems, a change in the rate of expansion would be perceived when the SI units of meters distance from the BB 'point' reaches the Planck scale when inverted. To me this seems more like a phase change point that is created because of the units being used going from macroscopic to microscopic. i.e. very large and very small, real and measurable but an illusion due to scaling, either way.

[modest]

Where would I go wrong if I assumed the following:

• The universe obeys the combined law of thermodynamics:

 

[math] dU - TdS + pdV \leq 0 [/math]

where dU is change in energy, T is temp, S is entropy, p is pressure, and V is volume

 

• The change in energy is 0 as to obey conservation of mass/energy

 

[math] pdV - TdS \leq 0 [/math]

or…

[math] pdV \leq TdS [/math]

 

• We assume (as standard cosmology) that T decreases, V increases, and p decreases then:

 

change in S would have to be an increase as to keep the equation proper and balanced.

 

I honestly think I am making some fundamental error in reasoning here - I just don’t know what it is.

 

-modest

[Pluto]

Hello All

 

 

CC said

 

Notwithstanding, regarding your phrase: "evidence supports some type of beginning," the old vision offered by modern cosmology (big bang event included) makes it inevitable now (that it has been removed) to see an enormous question mark suspended around the vacuous concept of “origin” (where physics breaks down) and the vital responsibility it might assume in our conception of both the underpinning of physical science (thermodynamics included) and the nature of the universe in its entirety.

 

Why not some type of recycling. Every time matter recycles, the dating process starts again. This would explain the different stages and forms of stars and galaxies.

[modest]

Why not some type of recycling. Every time matter recycles, the dating process starts again. This would explain the different stages and forms of stars and galaxies.

 

Am I going to be recycled back to hydrogen?

 

 

 

Is it going to hurt? :)

 

 

 

-modest

[coldcreation]

Where would I go wrong if I assumed the following:

• The universe obeys the combined law of thermodynamics:

 

[math] dU - TdS + pdV leq 0 [/math]

where dU is change in energy, T is temp, S is entropy, p is pressure, and V is volume

 

• The change in energy is 0 as to obey conservation of mass/energy

 

[math] pdV - TdS leq 0 [/math]

or…

[math] pdV leq TdS [/math]

 

• We assume (as standard cosmology) that T decreases, V increases, and p decreases then:

 

change in S would have to be an increase as to keep the equation proper and balanced.

 

I honestly think I am making some fundamental error in reasoning here - I just don’t know what it is.

 

-modest

 

 

Good question modest, let's see (putting aside for now the questions regarding the very early universe and the future of an accelerated expanding universe, as time t tends to infinity and temperature T approaches 0 kelvins) where would you have gone wrong, i.e., let's see if you made "some fundamental error in reasoning."

 

 

Standard cosmology (viz Lambda-CDM model) assumes that 74% of the energy density of the universe is composed of dark energy. Where does that figure into your equations (i.e., where would you write your, say, negative pressure term)?

 

 

Furthermore, the new standard model has 22% of the energy density of the present universe made up of non-baryonic, dissipationless and collisionless dark matter. Where does that figure in the above equations?

 

 

I realize that according to the second law of thermodynamics entropy is a property that generally increases with time. My question is, how the standard model (lambda-CDM) incorporates the laws of thermodynamics into its framework when 94% of its constituents remain elusive, dark.

 

Finally, you write, "The universe obeys the combined law of thermodynamics:" Where does the third law of thermodynamics (of which I beleive you are aware, from previous discussions) appear above?

 

 

 

CC

[modest]

Good question modest, let's see (putting aside for now the questions regarding the very early universe and the future of an accelerated expanding universe, as time t tends to infinity and temperature T approaches 0 kelvins) where would you have gone wrong, i.e., let's see if you made "some fundamental error in reasoning."

 

Standard cosmology (viz Lambda-CDM model) assumes that 74% of the energy density of the universe is composed of dark energy. Where does that figure into your equations (i.e., where would you write your, say, negative pressure term)?

 

Furthermore, the new standard model has 22% of the energy density of the present universe made up of non-baryonic, dissipationless and collisionless dark matter. Where does that figure in the above equations?

I made no such assumptions in my post. You will see my assumptions are that volume is increasing pressure is decreasing and temperature is decreasing, also that there is no net change in energy. I am evaluating entropy from that standpoint regardless of how many types, versions, or states of energy there are. I guess if you know of a type of energy that doesn't follow the conservation of mass/energy then I have a problem - but this would also create a problem for the foundation of many disciplines of physics.

 

I realize that according to the second law of thermodynamics entropy is a property that generally increases with time. My question is, how the standard model (lambda-CDM) incorporates the laws of thermodynamics into its framework when 94% of its constituents remain elusive, dark.

 

Finally, you write, "The universe obeys the combined law of thermodynamics:" Where does the third law of thermodynamics (of which I beleive you are aware, from previous discussions) appear above?

CC

 

The third law of thermodynamics is included in the combined law of thermodynamics. So where is it? I guess you would say it is a function of T being a product of S when T approaches 0. If you need more specifics than that, you should wiki the combined law of thermodynamics.

 

I really am looking for an error in my solution inside the scope of this equation. I don't doubt the math, but if someone with a stronger physics background could give me some criticism - it would be much appreciated. Also, I think this goes to the heart of this thread. Does an expanding and cooling universe violate the laws of thermodynamics? Can the combined law of thermodynamics give us any clue?

 

-modest

[modest]

coldcreation,

you do make a good point about T approaching infinity… Would that make S infinitely small? We would have to account for volume and pressure being infinites as well - I don't know.

 

-modest

[CraigD]

Does anyone see the problem that emerges here?

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

 

I can see a problem with this text, from Evidence for the Big Bang:

From quantum field theory, we know that something does indeed come from nothing: to wit, "vacuum fluctuations". In the simplest case, an electron, a positron and a photon can appear effectively out of nowhere, exist for a brief time and then annihilate, leaving no net creation of mass or energy. …

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 :( ):

[math]

\setlength{\unitlength}{1mm}

\begin{picture}(0, 0)

\put(10, 20){ \makebox(3,0)[cc]{$\gamma$} \vector(1,0){10} }

\put(24, 20){ \vector(2,1){10} }

\put(24, 20){ \vector(2,-1){10} }

\put(35, 25){ \makebox(3,0)[cc]{$e^-$} \vector(2,-1){10} }

\put(35, 15){ \makebox(3,0)[cc]{$e^+$} \vector(2,1){10} }

\put(50, 20){ \makebox(3,0)[cc]{$\gamma$} \vector(1,0){10} }

\end{picture}

[/math]

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

 

More profoundly, the paragraph following this,

The common point for all of these effects is that they do not violate any known conservation laws of physics (e.g., the conservation of energy, momentum, and charge). Something can indeed come out of nothing as long as these conservation laws permit 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.

 

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.

 

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.

[coldcreation]

I made no such assumptions in my post. You will see my assumptions are that volume is increasing pressure is decreasing and temperature is decreasing, also that there is no net change in energy. I am evaluating entropy from that standpoint regardless of how many types, versions, or states of energy there are. I guess if you know of a type of energy that doesn't follow the conservation of mass/energy then I have a problem - but this would also create a problem for the foundation of many disciplines of physics.

 

 

Ok, but I was hoping the discussion would revolve around the concordance model of cosmology, Lambda-CDM, the new satndard model, not the pre-1998 standard hot big bang model, which was based on the Friedmann models. How does thermodynamics fit into this model (if indeed it does at all)?

 

 

 

The third law of thermodynamics is included in the combined law of thermodynamics. So where is it? I guess you would say it is a function of T being a product of S when T approaches 0...

 

 

Nice try.

 

 

I really am looking for an error in my solution inside the scope of this equation. I don't doubt the math, but if someone with a stronger physics background could give me some criticism - it would be much appreciated. Also, I think this goes to the heart of this thread. Does an expanding and cooling universe violate the laws of thermodynamics? Can the combined law of thermodynamics give us any clue?

 

 

Good questions.

 

 

coldcreation,

you do make a good point about T approaching infinity… Would that make S infinitely small? We would have to account for volume and pressure being infinites as well - I don't know.

 

 

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

 

 

 

CC