Split Thread Michael Mozina's thread on Dark Matter, Inflation and Cosmology

[DeiRenDopa]

[...]

Oh quite a lot.

I find it interesting to get involved in such discussions (when I have the spare time) as not only does it serve to educate the large amount of lurkers but I genuinely am interested in what makes MM and his ideas tick.

I also like to try to tear apart my dearly held ideas whenever possible.

The fact they keep stitching themselves back together always amazes me.

Thanks.

I too went from taking what MM wrote as serious attacks on what I'd been taught, what I'd learned, and what I in turn had taught (and, early on, learned a fair bit about what is essential/fundamental, what is distracting/superfluous, what is easy to explain and what not, etc), to being interested in what makes MM and his ideas tick.

Have you come across anyone similar to MM, here in the Science section of JREF Forum?

 

[DeiRenDopa]

Really? I would have thought it dates back as far as Gallileo at least? Although this and similar threads are more colourful versions, more suitable to the modern age

Thanks for that.

Yes, I see what you mean ... but that is Galileo speaking with two voices, he has full control over what each actor says, there's no audience feedback, etc (IIRC, one of Lakatos' best works was in a similar, though more complex, form; Proofs and Refutations?).

The way I see it, these sorts of threads have something in common with discovery learning, but there are, obviously, some rather significant differences.

 

[Perpetual Student]

My new favorite word:

Hoy

 

[Michael Mozina]

The lecture starts with decribing Newtonian mechanics. That is what happens in science lectures - introduce the basics and then go onto the advanced stuff.

I'll make you a trade. I'll sit through each and every one of those two hour long videos if you'll read Birkeland's volume, cover to cover, starting on page one.

I personally agree that the actions of gravity and dark energy can be decribed as forces. They however are not forces in the classic sense.

This would appear to put you in a minority position because GR theory generally treats gravity as a 'curvature' of "spacetime', not as a "force" the way Newton treated it. On the other hand QM's theoretical "gravitons' could offer you a "force" oriented theory of gravity that eventually replaces GR. You could even treat light between stars as a "force".

Just out of curiosity, if you're looking for a classic force of nature that causes plasma to "accelerate", why not start with an EM field?

 

[DeiRenDopa]

As a non-participant, I can't answer that.

As a non-physicist lurker, however, I can report that I have learned a number of things by following this thread, and that it has been far more interesting than reading Bjarne's threads. It isn't hard for lurkers to figure out which participants know what they're talking about, and which participant can be ignored.

Will

Now I'll HAVE to go read some of Bjarne's threads!

[...]

I took a quick look, and I agree that this thread is indeed far more interesting that at least the Bjarne threads I skimmed!

 

[Michael Mozina]

I probably have no right to pop my head up in this debate (certainly, out of my depth), but it seems that negative pressure is indeed accepted in standard physics.

Yes, but it typically "accepted" as a "shorthand" that represents a pressure difference, not an absolute representation of real pressure. This effect can be demonstrated at almost any "pressure" in the chamber. It's not a representation of the absolute pressure between the plates, just the "difference" in pressure (usually EM pressure) on the outsides of the plate and the insides of the plates. Most people "understand" this, but evidently some do not.

Keep in mind I provided them with plenty of links and even some pretty little pictures from multiple sources to demonstrate all this and all they did was ignore every little bit of it.

What is the case against its existence exactly?

The best "case" that there is not a "negative pressure" between the plates is that it really doesn't matter what the pressure is inside of the chamber, you will still see a similar effect between the plates. Most people assume it's the EM carrier particle producing more pressure on the outside and less pressure (what they keep calling negative pressure) on the inside of the plates. The absolute pressure in the chamber can be very much greater than zero and therefore there isn't much likelihood that the "absolute pressure" between the plates is anywhere near zero. Furthermore the type of material used in the plates makes a fundamental difference in the way the plates behave with demonstrates that the EM carrier particle is the likely culprit here and it has nothing to do with absolute pressure in the chamber.

It seems MM is implying it's just common sense that absolute pressure can't be negative.

It's not just "common sense" it is a physical fact. There isn't a single vacuum chamber on Earth that can create even a "zero pressure" chamber, let alone a "negative" one.

I think you need to make a much stronger case than that, MM. Your language, and that argument in particular, makes you come across more like a layman than a physicist.

So ask them a simple physics question. Ask them what they intend to physically add or subtract from a perfect vacuum (no atoms or subatomic particles of any sort) that would create "negative pressure" in a vacuum?

 

[Michael Mozina]

I took a quick look, and I agree that this thread is indeed far more interesting that at least the Bjarne threads I skimmed!

Well, it's good to know that I at least have a little entertainment value.

 

[Perpetual Student]

OK, for this non-physicist is seems that pressure must be relative -- i. e., there is no such thing as absolute pressure. Is that not true?

 

[W.D.Clinger]

I've come across comments in a similar vein several times before (not just wrt MM), and I'm beginning to think that there might be a powerful pedagogical technique here somewhere, one that I don't recall having seen in any teacher training materials.

If there are any educators reading this, would you mind commenting? Specifically, do you know if the sort of exchange that is common in this (and other MM) thread(s) is used in a known teaching methodology (and if so, what)? Lurkers (students) certainly do seem to enjoy reading along, and they also certainly do seem to learn stuff that might otherwise be very hard to learn ...

There's a loose connection with the Moore_method^WP, a participatory pedagogy from which I learned point set topology (as taught by Carl Pixley and RH_Bing^WP) and still use to teach theory of computation. Learning to criticize and to accept criticism from peers is an important part of the Moore method, as is paying close attention to the back-and-forth even when lurking. (If we're going to discuss this topic further, we should probably take it to the Education forum.)

 

[Pythonic]

So ask them a simple physics question. Ask them what they intend to physically add or subtract from a perfect vacuum (no atoms or subatomic particles of any sort) that would create "negative pressure" in a vacuum?

I believe I understand what you're getting at, but I don't know if I see the value of taking it out of its context (i.e., a vacuum on its own). That is, the effect is negative relative to the effect of ambient pressure. It behaves in reverse by comparison. Yeah, I guess something can considered not in reverse if there's nothing to compare it to, but what is the significance of that? Isn't its comparative effect the whole point?

 

[Tubbythin]

The "pressure" of those "modes" on the inside of the plates is "less than" (not negative) the "pressure" from those same modes on the *OUTSIDE* of the plates. Hoy.

Michael, which of the following do you not agree with:
a) Increasing the gap between the plates increased the number of allowed modes.
b) Increasing the number of allowed modes increase the vacuum energy in the gap.
c) Increasing the gap increase the volume in the space between the plates.
d) If dE/dV is positive then -dE/dV must be negative.
e) -dE/dV is a definition of pressure.

 

[Michael Mozina]

Michael, which of the following do you not agree with:
a) Increasing the gap between the plates increased the number of allowed modes.

Yes, and increasing the gap between the outside of the plate and any walls also increases the number of allowed modes. Agreed?

b) Increasing the number of allowed modes increase the vacuum energy in the gap.

IMO, you're mixing terms in a confusing way. The vacuum itself has no energy. The EM field passing through the vacuum puts energy into even a "futurely fabulous" vacuum, one that that might be capable of removing every atom in a chamber. The energy is in those EM "modes" as you call them. I'd just call them the carrier particles of the EM field.

c) Increasing the gap increase the volume in the space between the plates.

Sure.

d) If dE/dV is positive then -dE/dV must be negative.

Ok, but what does that mean to you in terms of physics and physical particles? Why is the effect replicable at almost any "pressure" in the chamber, and only with metallic plates in your opinion?

e) -dE/dV is a definition of pressure.

It's ultimately just a 'pressure difference'. There is "less pressure" on the insde of the plates and "more pressure" on the outside of the plates. While you can refer to this pressure difference as a "negative number" is has nothing whatsoever to do with the absolute pressure in the chamber as demonstrated by the fact that works at almost any pressure.

 

[Michael Mozina]

I believe I understand what you're getting at, but I don't know if I see the value of taking it out of its context (i.e., a vacuum on its own). That is, the effect is negative relative to the effect of ambient pressure.

Yes, but you personally qualified your statement in a scientifically correct manner. They do not and will not do so. What can I say?

Keep in mind that the "ambient pressure" is being applied to the outside of the plates by the carrier particle of the EM field. There is simply "more" of it on the outside of the plates and "less" of it on the inside of the plates. Even at the level of EM fields, there is no place inside the chamber where the "absolute pressure" is negative. That is actually physically impossible since our best vacuums just are not that good and even space is not a "perfect' vacuum. It has all kinds of energies flowing through it.

 

[Reality Check]

This would appear to put you in a minority position because GR theory generally treats gravity as a 'curvature' of "spacetime', not as a "force" the way Newton treated it.

That is right: GR theory generally treats gravity as a curvature of spacetime, not as a "force" the way Newton treated it.
That is why I said: "I personally agree that the actions of gravity and dark energy can be decribed as forces."

On the other hand QM's theoretical "gravitons' could offer you a "force" oriented theory of gravity that eventually replaces GR. You could even treat light between stars as a "force".

Replaces GR but does not change its predictions except on QM scales such as the Planck length.

Just out of curiosity, if you're looking for a classic force of nature that causes plasma to "accelerate", why not start with an EM field?

Why am I looking for a classic force of nature that accelerates plasma?
What is the situation?

 

[Michael Mozina]

OK, for this non-physicist is seems that pressure must be relative -- i. e., there is no such thing as absolute pressure. Is that not true?

I'm not quite sure what you mean, but yes, "pressure" is almost always though of as a relative thing.

Keep in mind however that we can theoretically at least think of a 'pure' vacuum as one that contains no atoms of any sort, no subatomic particles of any kind inside the chamber, no photons, no neutrinos, nothing. Of course that isn't possible in real life, but we can at least in theory say there could be a logical way to describe the "absolute" pressure of a "vacuum" as one where no objects are present to pass on kinetic energy to anything inside the vacuum.

 

[Tubbythin]

Thanks.

No doubt MM sees it differently ... have you come across anyone else, here in this part of the JREF forum, who has similar views to MM's (in this respect)?

All the PC proponents seem to be adept at hand-wavy explanations and a complete failure to understand that physics is quantitative subject. If seen them talk about the importance of lab-based experiments. But I don't recall any of them ranting quite so much about "empirical physics", "control mechanisms" and "Occam's razor" whilst not seeming to have a clue what any of these nice phrases actually mean.

What would you say is the most concise, telling example of this self-defeating approach of MM's?

His ranting about control mechanisms have been particularly telling. Apologies while I go into Vicky Pollard mode:
First he says that dark matter detectors don't have control mechanisms. Then I point out the blatantly obvious control mechanisms. Then he says yes but there is no on/off switch and controlled experiments have to have on/off switches. So I say that there's no on/off switch for gravity. But he says we don't need an on/off switch. So I tell him that he just said we did. So he asks me why I'm so obsessed with control mechanisms. Pure genius.

 

[Reality Check]

I'm not quite sure what you mean, but yes, "pressure" is almost always though of as a relative thing.

Keep in mind however that we can theoretically at least think of a 'pure' vacuum as one that contains no atoms of any sort, no subatomic particles of any kind inside the chamber, no photons, no neutrinos, nothing. Of course that isn't possible in real life, but we can at least in theory say there could be a logical way to describe the "absolute" pressure of a "vacuum" as one where no objects are present to pass on kinetic energy to anything inside the vacuum.

That is not quit right.
It is true that we can think of a pure classical vacuum that contains no atoms, subatomic particles, photons, neutrinos, etc.
But add in quantum mechanics and there is no such thing as a pure vacuum because at any point in time it contains virtual particles. They lead to the well known Casimir effect that predicts negative pressures which have been actually measured.

Neat picture time: A Force from Empty Space: The Casimir Effect

ETA
The picture shows an experimental setup for meeasuring the Casimir effect. I think that it goes like this:
The apparatus is in a good vacuum. That means that the force and so the pressure on the sphere should be constant (zero?).
Put the sphere over a hole on the surface and measure its position. That calibrates the apparatus.
Put the sphere over a flat bit of the surface. According to classical physics (and you MM) it's position should not change. There would be no detectable pressure just from proximity to a surface in a good vacuum. But the sphere moves closer to the surface - there is an atractive force between it and the surface. That is the Casimir effect. By changing the distance from the surface the variation of the force can be measured and agrees with calculations of the Casimir effect.

If there is only positive pressure in the universe then something (the remaining atoms in the vacuum?) has decided to impact the far hemisphere of the sphere more than the near hemisphere of the sphere. You could argue that the remaining atoms are less likely to hit the near hemisphere because the surface shields the sphere somehow. But I cannot see the surface shielding the sphere. In fact it may be the other way around since atoms will be bouncing off the surface and the sphere will intercept some.

 

[Tubbythin]

Yes, and increasing the gap between the outside of the plate and any walls also increases the number of allowed modes. Agreed?

Which walls?

IMO, you're mixing terms in a confusing way. The vacuum itself has no energy.

Yes it does. The wikipedia article you kept telling us agreed with you even explicitly says it does.

The EM field passing through the vacuum puts energy into even a "futurely fabulous" vacuum,

It has nothing to do with external fields. Only fluctuations in the vacuum.

one that that might be capable of removing every atom in a chamber. The energy is in those EM "modes" as you call them. I'd just call them the carrier particles of the EM field.

You do know what I mean by the modes of a standing wave don't you?

Ok, but what does that mean to you in terms of physics and physical particles?

It isn't something that works in the sense of physical particles. Its an inherently quantum effect that comes about because of the uncertainty principle.

Why is the effect replicable at almost any "pressure" in the chamber,

Vacuum fluctuations exist at any and every pressure.

and only with metallic plates in your opinion?

The metallic plates define the boundary conditions. Ie the allowed modes must have nodes at these boundaries. Thus you can't "fit" modes with a wavelength greater than twice the plate separation.

It's ultimately just a 'pressure difference'. There is "less pressure" on the insde of the plates and "more pressure" on the outside of the plates. While you can refer to this pressure difference as a "negative number" is has nothing whatsoever to do with the absolute pressure in the chamber as demonstrated by the fact that works at almost any pressure.

Take some empty space. Stick in two plates close together. Congratulations! The pressure between the plates is negative.

 

[Michael Mozina]

Take some empty space. Stick in two plates close together. Congratulations! The pressure between the plates is negative.

No. If there are no carrier particles of the EM field hitting the inside or the outside of the plates, there will simply be no "pressure" difference between the outside or the inside of the plates. Even with carrier particles flowing through the process, it's still a "pressure difference" between the outside and inside of the plates, not "negative pressure". You're still confusing the concept of "ABSOLUTE" pressure with relative pressure.

 

[Reality Check]

Outstanding questions for Michael Mozina

1. Can you give a citation to "Birkeland's very first rough calculation..."
   First asked 7 January 2010
2. Do you understand that there is an upper limit on the baryonic mass of 6%?
   First asked 7 January 2010
   Note that baryonic mass includes all the things you have mentioned, e.g. rocks, planets, electron, ions, plasma, black holes, etc.
3. Do you know that Alfven-Klein cosmology is invalid?
   First asked 8 January 2010
4. A couple of really simple physics questions for Michael Mozina on pressure.
   First asked 8 January 2010
   (but a continuation of the various displays of your inability to grasp the concept of negative pressure in other threads since April 2009)