Million degree gas and "clumps" of matter

[Sun88]

Jeff Root has it completely correct.
A plasma is a gas with some extra qualities.
It still adheres to the gas law, albeit that sometimes the adiabatic constant is slightly different, but that does not make it not a gas.
(naturally we can make it even more confusing by claiming that plasma is a fluid, see Alfven and his magnetoHYDROdynamics.)

Apart from that, most of the general population has got no idea what it means when a newspaper says there is a blob of plasma, they may think that the local blood bank has exploded or something. Therefore saying that there is a superhot cloud of gas coming towards the Earth is better to visualise for the general publick and there is actually nothing wrong with the claim.

(netx to that, there are some questions for you that you nicely left unanswered in the UT thread, now in post #9)

Which ones, Tusenfem?


Are there people here that are still confused between the states of matter? Plasma, Gas, Liquid and Solids, they are all very different states of matter.

[Sun88]

Jeff Root has it completely correct.
A plasma is a gas with some extra qualities.
It still adheres to the gas law, albeit that sometimes the adiabatic constant is slightly different, but that does not make it not a gas.
(naturally we can make it even more confusing by claiming that plasma is a fluid, see Alfven and his magnetoHYDROdynamics.)

Apart from that, most of the general population has got no idea what it means when a newspaper says there is a blob of plasma, they may think that the local blood bank has exploded or something. Therefore saying that there is a superhot cloud of gas coming towards the Earth is better to visualise for the general publick and there is actually nothing wrong with the claim.

(netx to that, there are some questions for you that you nicely left unanswered in the UT thread, now in post #9)

To the extent that the writers of these PR's are simplifing the technical terms so as not to confuse or alarm or even just to sensationalize them there are limits.

For instance lets take this PR

It’s called a Type Ia supernovae and it shines with the luminosity of a billion suns. For all intents and purposes, once they explode they’re dead… But it ain’t so. They might have a core of ash, but they come back to life by sucking matter from a companion star. Zombies? You bet. Zombie stars… And they can be used to measure dark energy.

Now to most of the general population Zombie stars would sound pretty scary especially those dark matter life sucking ones!! So thats ok for "Stuff" we don't really no what it is e.g Dark Matter and Zombie stars! But...

Plasma we know of and if the Authors were to include the correct terminolgy in there press realease's then the general population would not be so scared/confused. Let's try rerwiting the original PR for Neutron Star Burps up Stellar Gas.

[Nereid]

To the extent that the writers of these PR's are simplifing the technical terms so as not to confuse or alarm or even just to sensationalize them there are limits.

For instance lets take this PR

Now to most of the general population Zombie stars would sound pretty scary especially those dark matter life sucking ones!! So thats ok for "Stuff" we don't really no what it is e.g Dark Matter and Zombie stars! But...

Plasma we know of and if the Authors were to include the correct terminolgy in there press realease's then the general population would not be so scared/confused. Let's try rerwiting the original PR for Neutron Star Burps up Stellar Gas.

Forget scariness (or otherwise; does a significant number of people who read ESA (etc) PRs genuinely believe in the existence of zombies? Do we berate economics/business writers for describing certain Japanese companies as zombies?).

Confusion over gas/plasma is utterly trivial compared with that over redshift/light travel time distance (you did click the links, and read the articles, didn't you?).

Have you considered a career in science writing Sun88? In the section of the PR you quote from, "ash" is clearly no more than an analogy (and however you look at it, not "the correct terminolgy"!); yet that analogy is relatively easy follow. Consider some hot topics in contemporary cosmology; how would you describe, for the general audience who reads such, "non-gaussianity", or "running spectral index"?

Why the fixation with gas/plasma?

[Sun88]

Forget scariness (or otherwise; does a significant number of people who read ESA (etc) PRs genuinely believe in the existence of zombies? Do we berate economics/business writers for describing certain Japanese companies as zombies?).

Confusion over gas/plasma is utterly trivial compared with that over redshift/light travel time distance (you did click the links, and read the articles, didn't you?).

Have you considered a career in science writing Sun88? In the section of the PR you quote from, "ash" is clearly no more than an analogy (and however you look at it, not "the correct terminolgy"!); yet that analogy is relatively easy follow. Consider some hot topics in contemporary cosmology; how would you describe, for the general audience who reads such, "non-gaussianity", or "running spectral index"?

Why the fixation with gas/plasma?

That's because plasma has some special properties, as Ian Tresman has said, that make plasmas distinct from gas, do you know of these special properties?

If you do you may be able to see the error in there oversimplistic PR or indeed in their paper!

[HenrikOlsen]

Do we berate economics/business writers for describing certain Japanese companies as zombies?).

Or for calling a certain bank a giant vampire squid?

[HenrikOlsen]

That's because plasma has some special properties, as Ian Tresman has said, that make plasmas distinct from gas, do you know of these special properties?

Yes, what's your point?

Those properties are irrelevant when it's getting eaten by a neutron star, as it reacts the same way to gravity as any matter.

And when the properties aren't relevant for the thing that happened, it becomes far less relevant to distinguish.

[Sun88]

Or for calling a certain bank a giant vampire squid?

But it's still a bank, is it not??? You could call that bank a blood sucking leach, but it's still a bank. Same as Neried's Japanese companies zombies, there still companies.

But Plasma is not a gas and gas is not a plasma!! And when that gas is superheated to millions of degrees then it is no longer a gas but a plasma. If it started out as a "stellar wind" as the PR said, then it was not even a gas in the first place but a PLASMA.

Now assuming all things being equal, then would could assume this stars "stellar wind" would be analogous to our Solar wind and that the "clump" of matter would be analogous to a CME (may even be able to call it a Plasmoid!) and we have spacecraft monitoring the Sun 24/7 and the Earth magnetic field is a dipole though much lower in strength than a "Neutron Star", so in essence what would the difference be between the two? We have seen and measured these events here in our solar system we have the data.

[korjik]

Plasma is a gas. A superhot gas. It isnt all that big a deal.

Your assumption that all things are equal is a very bad one tho. First, the stellar wind from a blue giant may be a very different sort of thing than the Sun's wind. Second, there is no evidence that the mass ejections is coronal. That would make it a very different thing than a CME. Third, the environment around a neutron star is very different than that of the Earth. To a large degree, gravity can be left out of the Earth's magnetosphere. Its effects are generally small next to the electromagnetic ones. This is very much not true in a neutron star. To the point of needing to do General Relativistic effects on the EM fields in addition to the falling gas. It is very possible, to the point of very probable, that there are alot of things that happen in a neutron stars magnetic field that simply cannot happen in the Earth's field. Heck, it may be that the neutron star has a much more powerful field and that the field configuration in that system may look nothing like the Earth's

[HenrikOlsen]

But it's still a bank, is it not??? You could call that bank a blood sucking leach, but it's still a bank. Same as Neried's Japanese companies zombies, there still companies.

But Plasma is not a gas and gas is not a plasma!!

That comment was not about gas vs. plasma, but about your rant against the name zombie stars. Please try to keep track of your ideas.

BTW, from what I can read, plasmoids are the brainchild of a seriously fringie guy who actually postulated that an electron is composed of helical plasmoids forming vortex "loops" around a "ring". Are your repeated talk about plasma an attempt at getting a discussion of this wedged in here?

[tusenfem]

Sun88 it might benifit if you would read through the thread "plasma physics for dummies" that I once wrote.
You can keep on claiming that a plasma is not a gas, but that is not going to make it correct. Plasma is gas+, it has all the properties of a gas (unbound particles, filling up spaces, compressionability, ....) and then it happens to have some extra properties too which belong to the plasma state (group behaviour, charged particles, conducting, ...).

Say I have a plasma in the solar wind with a density N=4 cm^-3 and a temperarture T = 1.E5 K and a velocity of v = 400 km/s, I can calculate the "plasma" pressure which would be:

P_pl = 1.5 N k T = P_gas

and the ram pressure with which it will hit the Earth is

P_{ram, pl} = m_p N v² = P_{ram, gas}

and so we can go through the whole shenaningans, and we find that the plasma adheres to all gas laws.

And then often there is the case that there is a magnetic field in the plasma (you know that thing you think is "majik", see post #9 for a question about that), which can lead to more complicated behaviour of the plasma, the temperature for example can be different along and perpedicular to the field, which makes that the pressure is no longer a scalar as in a gas but can become a tensor, however, both components of this pressure again behave according to the gas pressure laws.

So, for the last time and then I am going to stop it, it is perfectly okay to call a plasma a gas.

[tusenfem]

But Plasma is not a gas and gas is not a plasma!! And when that gas is superheated to millions of degrees then it is no longer a gas but a plasma. If it started out as a "stellar wind" as the PR said, then it was not even a gas in the first place but a PLASMA.

yah yah yah, see post above.

Now assuming all things being equal, then would could assume this stars "stellar wind" would be analogous to our Solar wind and that the "clump" of matter would be analogous to a CME (may even be able to call it a Plasmoid!)

Nah, let's not call it a plasmoid, that is rather different from a CME.

and we have spacecraft monitoring the Sun 24/7 and the Earth magnetic field is a dipole though much lower in strength than a "Neutron Star", so in essence what would the difference be between the two? We have seen and measured these events here in our solar system we have the data.

Like Korjik said above, the difference is that a neutronstar has a bezillion times stronger gravity field and a much much stronger magnetic field too, the situation between CME and Earth and Burp and neutronstar is only possible to be discussed in a rather imprecise analogy that you so dispise, regarding your abhorrence of calling a plasma a gas.

And the situation at Earth is completely different as most of the aurora that is produced at Earth is created by magnetospheric particles and not by solar wind particles. A little fact that lots of people don't know or forget about.

[tusenfem]

BTW, from what I can read, plasmoids are the brainchild of a seriously fringie guy who actually postulated that an electron is composed of helical plasmoids forming vortex "loops" around a "ring". Are your repeated talk about plasma an attempt at getting a discussion of this wedged in here?

Plasmoids are "blobs" of plasma in the Earth's magnetotail, they are observed quite often and are produced by magnetic reconnection in the tail.

[Sun88]

Plasma is a gas. A superhot gas. It isnt all that big a deal.

A plasma can be considered as a gas of highly ionized particles, but the powerful interionic forces lead to distinctly different properties, so that it is usually considered as a different phase or state of matter.

LINK

Those distinctly different properties include

Plasma, like gas, is a state of matter that does not have definite shape or volume. Unlike gases, plasmas may self-generate magnetic fields and electric currents, and respond strongly and collectively to electromagnetic forces. The particles that make up plasmas have electric charges, so plasma can conduct electricity

Super hot gas will not do this because it's a gas and not a plasma. LINK

[tusenfem]

I believe that x-rays have been detected in the aurora. See:

• W. L. Imhof et al, "The Polar Ionospheric X-ray Imaging Experiment (PIXIE)", Space Science Reviews, Volume 71, Numbers 1-4, 385-408

The X-rays in the auroral region are created by bremsstrahlung of highly energetic electrons, not by excited ions (see e.g. http://esoads.eso.org/abs/2004JGRA.....e et al. 2004) because the excitation levels of atoms do not reach into the X-ray part of the spectrum.

[Swift]

Sun88,

I am starting to seriously wonder what the point of this thread is. Are you asking a question, and if you are what exactly is your question? Are you asking a question about the nature of plasma, or the nature of popular science writing?

If you are not asking a question, but trying to have a discussion, exactly what is the topic of that discussion?

I will tell you flat out that BAUT has a very bad history with advocates of the Electric Universe ideas, and it looks a lot like you are trying to advocate this ATM (Against the Mainstream) idea.

You're to clarify all this on your very next post, or this thread will be closed.

[Nereid]

Personally I believe that scientists should strive toward accuracy.

A sentiment I think few BAUTians would disagree with.

Astronomers and science writers certainly have no problems introducing new terms all the time, so I don't see the use of "plasma" as a big deal.

Convention, marginal improvement in accuracy (as tusenfem and others have said, many times, in most contexts the difference between gas and plasma is essentially zero), time constraints (if you're writing a news story, you have very little time for careful reflection), and focus (if the main points of the story have to do with things other than a gas/plasma distinction, why add potential confusion?), none of these may be big deals ... but they all add up to explanations of why the term plasma may not be used as often as you (or Sun88) would like.

I'm not sure that the ease to introducing new terms (or not) has any relevance here; would you care to say more please?

In terms of science writing, wouldn't our limited resources (time, especially) be better devoted to a campaign of using redshift instead of light-years (light travel time distance), in material on cosmology (to take just one example)?

Obviously it depends on the subject being written about, and the context. But of course the space available to writers is not always available for lengthy explanations.

Indeed.

[iantresman]

.. as tusenfem and others have said, many times, in most contexts the difference between gas and plasma is essentially zero

That's not quite how I read it. For example, in tusenfem's post #40, he demonstrates that a certain property of the solar wind plasma adheres to gas laws. There is no dispute that plasmas and gases share similar properties. But that doesn't make all properties of the solar wind gas-like, and that the solar wind has many plasma properties, that differentiates it from a gas.

So I would argue that describing the solar wind as a (hot ionized) gas, is to diminish its plasma properties, and perhaps make some people think that the solar wind acts only like a gas, when it does so much more.

[Nereid]

.. as tusenfem and others have said, many times, in most contexts the difference between gas and plasma is essentially zero

That's not quite how I read it. For example, in tusenfem's post #40, he demonstrates that a certain property of the solar wind plasma adheres to gas laws. There is no dispute that plasmas and gases share similar properties. But that doesn't make all properties of the solar wind gas-like, and that the solar wind has many plasma properties, that differentiates it from a gas.

Sounds like you just agreed with me (note the "most" in what you quoted).

In some contexts, the distinction between hydrogen predominantly in the form of protium with a dash of deuterium and pure protium is essentially irrelevant; in others, it is central. In some contexts, the relative abundance of Li-6 vs Li-7 is irrelevant; in others, vital. In some contexts the temperature of a fully ionised gas is irrelevant ("hot" will do as a descriptor); in others 50,000 K and 3 million K are utterly different (fully ionised gases of either temperature are "hot" though).

So I would argue that describing the solar wind as a (hot ionized) gas, is to diminish its plasma properties, and perhaps make some people think that the solar wind acts only like a gas, when it does so much more.

But surely you agree that it's the context which plays the main role, don't you?

And that context includes not only the aspects being modelled or observed, but also the intended audience.

[iantresman]

But surely you agree that it's the context which plays the main role, don't you?

Regardless of the context, you can't go wrong if you describe plasma as plasma (which may share similarities with gases), but you may inadvertently limit its context by describing it as a gas.

[quotation]

uh, if plasma = gas+ why is it considered a separate state of matter? Also, has gas+ ever produced filaments that twist, pinch and occasionally ignite? I think the public would be fascinated by plasma

[Nereid]

Regardless of the context, you can't go wrong if you describe plasma as plasma (which may share similarities with gases)

Of course you can, and badly so too.

If your intended audience is familiar with "plasma" as something to do with blood, and has never encountered it to mean "ionised gas" (or something even more complex), then you'll go very wrong by using the term "plasma" in writing on astrophysics topics, in contexts where the distinction is essentially irrelevant.

And that's just one example.

, but you may inadvertently limit its context by describing it as a gas.

Indeed.

That's the sort of challenge science writers face every time they put fingers to keyboard, with regard to almost every term in astrophysics textbooks (one of my pet hates is "weigh", as in "weighing in at about 24 solar masses" - example - and "weight", as in "the approximate weight of a neutron star" - example).

If you're going to get riled up every time you read this sort of word use, perhaps it'd be best to simply stick with reading published papers, and scifi novels.

[Nereid]

uh, if plasma = gas+ why is it considered a separate state of matter?

Um, have you read the posts earlier in this thread?

What's being discussed (mostly) is the appropriateness of the use of the term "plasma" vs "gas", in the context of science writing for the general public (e.g. PRs, Universe Today stories, your local paper's Science section).

Also, has gas+ ever produced filaments that twist, pinch and occasionally ignite?

Huh?!?

What's that got to do with the price of eggs? More pertinent to this thread, did Tammy Plotner's Universe Today article refer to "filaments that twist, pinch and occasionally ignite"? I don't think so.

I think the public would be fascinated by plasma

Then by all means, quotation, become a science journalist, apply to be a staff writer on Universe Today, and start writing about the topic!

[quotation]

lol...Yes i did read the thread and as I was doing so I couldn't help but think about all the smart people over at UCLA, Cornell, Princeton et al. who might take exception to statements that plasma is just a hot hot gas and no big deal. Plasma is a big deal and I don't understand the resistance here, but I'm just a newbie with a lot to learn about this culture. What's really strange to me is the people here already have the mathematical acumen necessary to describe the very complex behaviors of plasma, which could go a long way to helping the public understand it, but perhaps I'll take your advice and start writing myself (if no one else will ;-)

[Swift]

Sun88,

I am starting to seriously wonder what the point of this thread is. Are you asking a question, and if you are what exactly is your question? Are you asking a question about the nature of plasma, or the nature of popular science writing?

If you are not asking a question, but trying to have a discussion, exactly what is the topic of that discussion?

I will tell you flat out that BAUT has a very bad history with advocates of the Electric Universe ideas, and it looks a lot like you are trying to advocate this ATM (Against the Mainstream) idea.

You to clarify all this on your very next post, or this thread will be closed.

OK, as we now have three people (Sun88, iantresman, and quotation) "asking questions", this thread no longer seems appropriate to Q&A, so I've moved it to Astronomy (at least for the moment). I would still like some clarification from Sun88 (or others) about what the topic of this thread is, because it seems like there are two or three conversations going on at once.

[iantresman]

If your intended audience is familiar with "plasma" as something to do with blood, and has never encountered it to mean "ionised gas" (or something even more complex), then you'll go very wrong by using the term "plasma" in writing on astrophysics topics, in contexts where the distinction is essentially irrelevant.

All you have to do, is use your term once and define it. eg. the solar wind plasma (ionized gas) has many amazing properties, because it is not just a gas.

Next we'll be defining "black holes", for people who think they are dark holes, "Big Bang" for those who it was very loud, and "gas" for people who have indigestion

[iantresman]

OK, as we now have three people (Sun88, iantresman, and quotation) "asking questions",

I have asked no questions, but merely contributed to the discussion. On the one hand we do seem to have deviated slightly from the original post, on the other hand, we have various interesting contributions on all sides, on the nature of plasmas (which was mentioned in the original post).

[tusenfem]

lol...Yes i did read the thread and as I was doing so I couldn't help but think about all the smart people over at UCLA, Cornell, Princeton et al. who might take exception to statements that plasma is just a hot hot gas and no big deal. Plasma is a big deal and I don't understand the resistance here, but I'm just a newbie with a lot to learn about this culture. What's really strange to me is the people here already have the mathematical acumen necessary to describe the very complex behaviors of plasma, which could go a long way to helping the public understand it, but perhaps I'll take your advice and start writing myself (if no one else will ;-)

No, I don't take exception calling plasma a gas, and I worked at UCLA (Institute for Geophysics and Planetary Physics) and now work at the Space Research Institute of the Austrian Academy of Science.

For the general public, IMHO (and maybe I am an arrogant plasma physicist) the word plasma has no meaning at all. Usually the solar wind and CMEs etc. are described as "a hot gas" and often the extra "with a magnetic field". And then the whole popular description can be made. Often, as an aside it will be said that that is a plasma and in magazines then there will be a box with further explanations about plasmas.

And yes, I could do a lot of math etc. to describe the complex behaviour of a plasma, and I do so in the papers I publish. However, if I go and give a general talk, I have to leave the math behind and then I have to go things peeps know. As an example, I studied Kelvin-Helmholtz waves in the Earth's magnetotail, but in the presentation I will go to the sea, and the wind driving waves of the surface of the water, etc. etc.

However, I am glad that you want to understand the really captivating topic of plasma physics. There is a "plasma physics for dummies" thread, giving an introduction for the physics/math apt members of this board. I hope you can enjoy it,

[Nereid]

All you have to do, is use your term once and define it. eg. the solar wind plasma (ionized gas) has many amazing properties, because it is not just a gas.

Yes, I expect that many of the readers of this thread - but certainly not all! - are quite familiar with this technique (and others which achieve the same end).

But the fact is that, for whatever combination of reasons, folk continue to write things like a certain object "weighs in at about 24 solar masses", or is "more than 13 billion light years away" (source - CBS News - not the same object!), and many other things that are - I'm sure you'd agree - far worse as sources of confusion (not to mention really messing with the underlying physics). In comparison, getting worked up over using "gas" instead of "plasma" is extremely pedantic, wouldn't you say?

Next we'll be defining "black holes", for people who think they are dark holes, "Big Bang" for those who it was very loud, and "gas" for people who have indigestion

The history of the usage of terms (the study of which is part of linguistics?) is a fascinating one. However, I doubt that there's anything so futile as to try to dictate usage to a speech community numbering in the hundreds of millions; goodness, if l'Académie française can't do it for French, within just France, even blind Freddy can see that the combined membership of BAUT has as much chance as a wax cat in hell (or is it a snowflake? ).

[Nereid]

No one has yet (not that I have noticed anyway) provided a link to the Plasma Physics for Dummies thread tusenfem has mentioned several times. Here it is: Plasma Physics for Dummies.

[Swift]

For the general public, IMHO (and maybe I am an arrogant plasma physicist) the word plasma has no meaning at all.

Actually, I suspect if you asked the general public what "plasma" was, that would say it is some component of blood, if they had any idea at all.