A Thought Experiment

[magicjava]

Hi again everyone. I have a thought experiment I was hoping the folks here could help me with.

1) We have an imaginary empty box. The box itself has not properties that would affect the experiment.
2) We place enough plasma in the middle of the box to fill it up 1/4 of the way.
3) We leave the box alone for some amount of time, T.

My question is what state will the plasma be in at time T compared to when we first put it in the box?

As an example answer, if instead of plasma we used gas, the gas in the box would expand.

[earls]

Plasma would expand to fill the container as well considering it is an "ionized gas."

Can heat/energy escape from the box? If so, the plasma would of course cool, become a gas, and possibly a liquid or solid depending on the system.

[magicjava]

Plasma would expand to fill the container as well considering it is an "ionized gas."

Would this be true of a Birkeland current?

[junglelord]

Non-sequitar, Birkeland Currents do not exist inside an empty box.

[magicjava]

Non-sequitar, Birkeland Currents do not exist inside an empty box.

Fair enough. But I guess the "it acts like a gas" answer surprised me for a couple of reasons:

*) From Wikipedia's discussion comparing Gas and Plasma:
____*) (GAS) All gas particles behave in a similar way, influenced by gravity, and collisions with one another.
____*) (PLASMA) Electrons, ions, and neutrals can be distinguished by the sign of their charge so that they behave independently in many circumstances, with different bulk velocities and temperatures, allowing phenomena such as new types of waves and instabilities.

____*) (GAS) Collisions usually lead to a Maxwellian velocity distribution of all gas particles, with very few relatively fast particles.
____*) (PLASMA) Collisional interactions are often weak in hot plasmas, and external forcing can drive the plasma far from local equilibrium, and lead to a significant population of unusually fast particles.

Given these two sets of comparisons, I was expecting plasma would act differently than gas.

[allynh]

If you get the chance buy a plasma ball, and study it. Many of the EU concepts become much clearer when you can watch an actual "sun in a bottle."

Go to Amazon.com and search for "plasma ball" to see what's available.

[magicjava]

If you get the chance buy a plasma ball, and study it. Many of the EU concepts become much clearer when you can watch an actual "sun in a bottle."

I've been reading Thunderbolts for about 2 years now, so I feel I have at least a general idea of what the EU concept is about. The problem is, as my comments on this thread show, I'm so unfamiliar with plasma physics I have no way of telling good ideas from bad, even at a very general and broad level. This differs from standard cosmology, where I'm at least familiar enough with it to spot bad Redshift data when I see it.

So what I really need to do right now is strengthen my understanding of plasma physics.

The original thought experiment I posted is basically asking how I can tell a low entropy plasma configuration from a high entropy plasma configuration.

As we all know, in a closed system entropy increases as you move forward in time. This means it decreases as you move backwards in time. If you want to get rid of the Big Bang, this means entropy decreases forever. As the minimal entropy configuration for gas is having all the gas in the same spot, getting rid of the Big Bang will cause the entropy of the gas to decrease forever, eventually taking you to...... a Big Bang configuration that has all the gas in the same spot.

What I was searching for is a way for using plasma (as opposed to gas) to avoid this conclusion.

[junglelord]

The universe is an Open System, it is not a Closed System.

[magicjava]

The universe is an Open System, it is not a Closed System.

I think there are a lot of smart folks who would agree with you on that. But not all of them.

The reason I'm taking the assumption of a closed system is not because I believe it to be true or false, but because I believe it to be the most difficult situation for a non-Big Bang cosmology to handle.

There _are_ solutions to the problem even if plasma has a low entropy configuration similar to gas. For example, Alfvén proposed the universe could have matter and anti-matter regions. As the universe contracted going back in time, the anti-matter and matter regions would eventually come in contact creating explosions that would fling the matter apart. So, going back in time, you'd expect to see contraction, you'd expect to see an explosion, but not a Big Bang.

But at this point I'm not trying evaluate Alfvén's proposal, or anyone else's. I'm just trying to get a feel for the entropy configurations for plasma.

[allynh]

The problem with any thought experiment is that it has nothing to do with reality, thus you start from the beginning with no way to answer real questions.

- How big is your empty box.

A foot across or a hundred thousand light years across. The starting conditions do matter.

- What do you mean by "empty".

You say fill up the box 1/4 full of plasma, what is in the rest of the box. There is no such thing as "empty" or "nothing", so what else is in your box.

See, that's why I suggest buying a plasma ball. You can see all aspects of plasma described in the various essays. You have to study what is actually physically happening in the world, not in some thought experiment.

[magicjava]

The problem with any thought experiment is that it has nothing to do with reality, thus you start from the beginning with no way to answer real questions.

In a certain sense I agree with you. For example, a few posts up I noted how entropy causes gas to collect at the same location when going backwards in time, and how this seems incompatible with _any_ "No Big Bang" cosmology. But I _didn't_ claim that plasma having entropy characteristics similar to gas invalidates EU or any other "No Big Bang" cosmology. To do that would be a huge oversimplification of the process because, as you rightfully point out, there are conditions in reality that are not present in the thought experiment. An example of that is the proposal by Alfvén I mentioned. Another example is that gravity has the _reverse_ entropy characteristics of gas, that is, the minimal entropy configuration for gravity is when all the objects are spread out, not when they are all collected like a gas. And gravity obviously plays a big part in the universe and can't be ignored.

But I disagree that you learn nothing from a thought experiment. For example, I've already learned that plasma has entropy configurations similar to gas. That isn't the answer I was expecting when I first presented the thought experiment. I understand that this answer is based on the conditions of the experiment and that changing those conditions may change the answer. But I've still learned something.

If one wants to study a cosmology, one _must_ take entropy into consideration. There's no escaping it. Here's a quote from Sir Arthur Eddington (somewhat paraphrased) that illustrates this:

If your theory is not liked by esteemed colleagues, sometimes those colleagues can be wrong.
If your theory does not match observation, sometimes observations are wrong.
If your theory does not follow the 2nd law of thermodynamics, there's nothing you can do.

So the point to this thread is to give me the beginnings of an understanding in how plasma should operate when it follows the 2nd law. I understand it's not the full story, but it's a start.

That said, I certainly have nothing against buying a plasma ball.

[magicjava]

I just wanted to wrap this up and give a short summary of what I think I've learned.

First, the thought experiment was not designed to prove or disprove any cosmology. It makes no statement on the validity or invalidity of EU, PC, Big Bang, or any other cosmology, and it wasn't meant to.

But what I did learn is that on very large time scales, where it's convenient to measure time in billions of years, there's very little difference between swapping out gas for plasma from the point of view of entropy and its effects on the very broad structure of the universe over time.

The thought experiment has no direct relationship to smaller time scales and smaller areas of space. For scales smaller than universal there can be (and, as we all know, are) differences in having a gas and having a plasma in a given situation.

Finally, I'd like to thank everyone for helping me out with this. It's very much appreciated.

[junglelord]

If plasma exhibits entrophy on the universal scale....how do stars form? How do galaxies form?
Entrophy is a closed system result, the universe is an open system.

[mharratsc]

Here's my two (layman) cents on this matter-

From http://www.dictionary.com

en⋅tro⋅py  /ˈɛntrəpi/ [en-truh-pee]

–noun 1. Thermodynamics. a. (on a macroscopic scale) a function of thermodynamic variables, as temperature, pressure, or composition, that is a measure of the energy that is not available for work during a thermodynamic process. A closed system evolves toward a state of maximum entropy.
b. (in statistical mechanics) a measure of the randomness of the microscopic constituents of a thermodynamic system. Symbol: S

2. (in data transmission and information theory) a measure of the loss of information in a transmitted signal or message.
3. (in cosmology) a hypothetical tendency for the universe to attain a state of maximum homogeneity in which all matter is at a uniform temperature (heat death).

Entropy is important in the 'Standard' Cosmological Model because everything in it is viewed from a thermokinetic perspective. 'Everyone' knows that the energy for the Universe was supplied in one stupendous Big Bang, but the mystery of the model is- how/why did the Big Bang happen??

Entropy is not important to the Electric Universe Model because the energy of the Universe is electrical-a perpectual state of charge imbalance that extends from the macro to the micro (or should that be reversed? ) across the Universe and is only broken occasionally by pockets where charges are balanced. Simply- there can't be entropy in a system of constantly supplied energy.
The Big Mystery of the EU Model of course is- where/how/why does the current come from??

But that's another story.

Anyway, now you see why there was some difficulty grasping the validity of a thought experiment about entropy, when (from the EU/PC perspective) it doesn't even exist. :\

Mike H.

[bboyer]

Perhaps this site (Max Planck Institute for Extraterrestrial Physics - Theory & Complex Plasmas) may be of some use to you, MJ. They have been running real-world experiments with plasma chambers, probably the closest we can get to your hypothetical closed-box system. Their next scheduled run of experiments aboard the ISS is for 2010:

At MPE also the next-generation complex plasma experiment is under construction: PK-4. In contrast to PKE-Nefedov and PK-3 Plus, PK-4 uses a DC glow discharge to generate the plasma. Whereas the former experiments are optimized for plasma crystals, PK-4 will be ideal to study fluid dynamics on the kinetic level. It will be sent to the Space Station in 2010.

The site has some impressive video clips and still shots but you'll have to explore to find them. Anyways, for what it's worth.

http://www.mpe.mpg.de/PKE/PKE/Hintergrund_e.html

http://www.mpe.mpg.de/PKE/index_e.html