Lambda-CDM theory - Woo or not?

[Michael Mozina]

There are no "arrows of force". When you say crazy things like that you can't possibly wonder why people think you're a crackpot without a clue.

If I call them pressure, you whine. If I call them force, you whine. What you won't do is explain those squiggly green lines and blue arrows yourself from the WIKI diagram, nor explain why it matches the last one I posted as well. You're a scientific coward.

 

[Michael Mozina]

Ie. the more we move the plates apart, the more waves we can fit in.

Er, why are you ignoring the fact that some waves fit between the plates and provide pressure on the plates? Why do all the inside arrows point into and not away from the inside of the plates?

 

[Tubbythin]

Er, why are you ignoring the fact that some waves fit between the plates and provide pressure on the plates?

I'm not. The point is, the bigger the separation of the plates, the more waves we can fit between the plates as your article says. The more waves we can fit between the plates the greater the energy between the plates. But since the plates have a constant cross-sectional area, the volume between the plates increases as we move the plates apart. Ie the vacuum energy in the space between the plates increases as the volume increases. Ie dE/dV is positive. Hence -dE/dV is negative. Hence, since pressure = -dE/dV, the pressure is also negative.

Why do all the inside arrows point into and not away from the inside of the plates?

Why do you care? Its clear from the article you just linked and the fact that P=-dE/dV that the pressure is negative.

 

[Vorpal]

Forgive me if I jump in without really understanding how the argument got here... but if we take a pressure vessule and take positive pressure as expansive and negative as contractive, all we have to do is consider surface tension. The fact that we can take a drop of water is due to surface tension in the first place, providing negative pressure. We could lower the external pressure, superheating the water, but compare it with a vacuum.

[Note: I assume it is unproblematic that vacuum is taken as P = 0. This is in part because MM had previously ridiculed taking things "out" of the vacuum to provide negative pressure, implicitly taking the vacuum as the standard to measure against.]

Consider a simple barometer a la Torricelli in a standard-atmosphere environment. Thus, we have a long half-closed glass cylinder filled with mercury up-ended in a pool of mercury. The mercury level drops, forming a vacuum. Normally, the level falls to 760mm, but not always--sometimes, the mercury enters a metastable state (i.e., jarring with sufficient force it destroys it) and settles above 760mm. So we have a vacuum above, 1 atm below (so we can't ascribe it to a difference with the environment!), more than 760mm of mercury inbetween; conclusion: at the top of the mercury column, the pressure must be negative. Unambiguously so, being less than a vacuum.

And in general, it isn't just some rare, exotic effect--it's just a consequence of the fact that liquids can adhere to surfaces (to various degrees). But the effect is not just real, but very common--e.g., it is demonstrated by any very tall tree, as the pressure difference needs to be an order of magnitude more than 1 atm in the xylem in order to draw the column of sap.

---
Fun detour: heat some coffee in a microwave. If it's homogeneous enough (without grounds, etc.--water is better) and the container is very smooth, it will be superheated, thus forming a "false liquid"--as soon as you disturb it, it will experience bubble nucleation and undergo a phase transition (i.e., boil), spewing crap all over the place. That's coffee inflation.

 

[Tim Thompson]

Casimir Force

Why do all the inside arrows point into and not away from the inside of the plates?

Because the diagram is at best deceptive, and at worst simply wrong, which is what you get for relying on Wikipedia of all things for your sine qua non of theoretical physics & quantum field theory. Go look in a physics book for a change. As the plates move closer together an attractive force appears (the Casimir force) which pulls the plates together, so the little arrows are pointing backwards. They are wrong and the diagram does not properly represent the Casimir force.

Positive pressure pushes the plates together from the outside. Negative pressure pulls the plates together from the inside. The Casimir force pulls the plates together from the inside. Therefore the Casimir force is a negative pressure. Mind numbingly complicated, isn't it?

 

[The Man]

Notice how you ignored the direction of force to focus on a "detail"?

Just details you blatantly ignore, like the fact that invariably your references, well, refer to what you claim is ‘physically impossible‘.

IMO, the "VP" orientation of QM seems rather "dated" to me at this point. When early experiments were first performed we did not understand the notion of EM fluctuations very well, or the implications of having billions of neutrinos flowing through the "vacuum", etc. Since that time, more "contemporary" explanations like the first one I provided note that this is simply fluctuation in the carrier particles of the EM field. Even in the VP world, there is an *UNDERSTANDING* that there is *energy in the system* and it too calls this "radiant pressure" that pushes *INTO ALL SURFACES IN THE CHAMBER*.

Well that seems to be your downfall, specifically your opinion. Again it should be no problem for you to calculate that "radiant pressure" that pushes *INTO ALL SURFACES IN THE CHAMBER*.” based on your very opinionated “*UNDERSTANDING* “.

As I have stated before, I think the term "vacuum energy" is a more accurate description only because a "zero" implies none, and there is no point in any vacuum that contains "zero" energy. There is no "zero point", only "positive pressure and kinetic energy in the vacuum".

Again as I have stated before the zero refers to the energy potential or specifically the amount of energy that can be extracted from that system. "positive pressure and kinetic energy in the vacuum" would in fact be energy that could be extracted from that system. Again you are accepting a term like "vacuum energy" without understanding what it means or its implications and that is just your blind faith in your own opinions.

Why are you ignoring the fact that his arrows point into the plates just like the WIKI diagram? Why did he draw it that way, with the arrows pointed into the plates? Did they both screw up, or did you just screw up?

If you knew anything at all a about force diagrams you would know that the force of consideration is the resulting force and on a solid body (when not considering mechanics of materials under constrained conditions) it does not matter which side you put that force vector on. So you are interpreting a force diagram without understanding how to interpret force diagrams. The net forces between the plates pulling them together is the result of that diagram.

Virtual photons can result in attraction as well as repulsion (hence electromagnetism being both attractive and repulsive) so the large arrows outside of the plates pushing in at one moment would be replaced by similar arrows on the outside of the plates pulling them apart the next. That is the nature of virtual fluctuations, that they, well, remain virtual or balance out over time. Same for the smaller arrows inside the plates fluctuating one way one instance and another the next. The magnitude of those fluctuations (size of the arrows) would also vary with time but again averaging to zero. The key point being that the zero point energy between the plates is less then that outside the plates. In fact the zero point or vacuum energy between the plates is a false vacuum (by excluding some vacuum fluctuations) and thus degenerative (by drawing the plates in) an aspect also related to cosmology and inflation in that false vacuums are degenerative.

 

[temporalillusion]

FYI Zig,

I don't really have any problems with anyone's "style" with the exception of GeeMack. He's made no attempt here at honest dialog, nor are his points focused on science. His whole "kill the messenger" style is simply a dishonest debate tactic from start to finish.

And the whole "ignore the inconvenient questions" you employ is so much better eh?

EDIT: I would really like MM to re-draw his little diagrams to illustrate cases where the plates are forced apart.

 

[Ziggurat]

What you won't do is explain those squiggly green lines and blue arrows yourself from the WIKI diagram, nor explain why it matches the last one I posted as well.

Funny thing about those squiggly green lines in the Wikipedia drawing: they're supposed to represent "vacuum fluctuations", but they're wrong. They show the plate surface being at an anti-node of those fluctuations, not at a node.

Argument from pictures doesn't cut it, Michael. The authors of drawings do screw up sometimes, and even if they don't, drawings are not quantified. As Dei said before, you're stuck in a pre-Newtonian mindset about what physics is.

 

[Tubbythin]

IMO, the "VP" orientation of QM seems rather "dated" to me at this point. [/ When early experiments were first performed we did not understand the notion of EM fluctuations very well,

Erm. The experiments were performed to see whether they agreed with the theory. They did. As shown in the wiki page, Casimir's calculation quite clearly gives a negative pressure. So this was tested for and found. If Casimir's calculation had predicted negative pressure (which quite clearly you can see from the wiki page it did) and the pressure had been positive then quite clearly Casimir would be wrong and this phenomenon wouldn't be reffered to as the Casimir effect.

or the implications of having billions of neutrinos flowing through the "vacuum", etc.

Did you miss the post where I estimated how utterly irrelevant neutrinos were? What was it? Something like one interaction per year? Would you like me to find it again. Suggest where I went wrong?

Since that time, more "contemporary" explanations like the first one I provided note that this is simply fluctuation in the carrier particles of the EM field.

You really haven't read the wiki article at all have you?

Even in the VP world, there is an *UNDERSTANDING* that there is *energy in the system* and it too calls this "radiant pressure" that pushes *INTO ALL SURFACES IN THE CHAMBER*.

There is an understanding that there is a vacuum energy and that this vacuum energy increases between the plates as the plates are separated. And hence dE/dV is positive and hence P =-dE/dV is negative. Ie there is an understanding that the Cassimir pressure is negative in the case of the two conducting plates. Hey, it even says that in a link at the bottom of the wiki article you love so much:

Because Casimir force between conductors is attractive then the Casimir pressure in space between the conductors is negative.

and on the Casimir research school webpage

Casimir discovered this universal attraction while he was studying some 19th-century physics: the effect of the Van der Waals forces on the stability of colloids. He understood that the attraction arises because the 19th-century concept of vacuum as empty space is wrong. According to quantum electrodynamics, vacuum is not empty at all but filled with particle-antiparticle pairs that emerge out of nothing and vanish back into nothing an instant later. In between the two plates these virtual particles have a lower density than outside. The resulting negative pressure pulls the plates together.

As I have stated before, I think the term "vacuum energy" is a more accurate description only because a "zero" implies none, and there is no point in any vacuum that contains "zero" energy. There is no "zero point", only "positive pressure and kinetic energy in the vacuum".

Zero-point just refers to the ground state of a quantum system therefore your arguments are nothing more than pointless semantics and utterly irrelevant.

Why are you ignoring the fact that his arrows point into the plates just like the WIKI diagram? Why did he draw it that way, with the arrows pointed into the plates? Did they both screw up, or did you just screw up?

Why are you ignoring the fact that its an unlabelled diagram from wikipedia. Its very amusing that someone with essentially no understanding of quantum mechanics whatsoever thinks they can bring down the current paradigm in cosmology with reference only to an uncaptioned diagram from wikipedia about the Casimir effect, an effect they have tried to attribute to neutrinos.

 

[DeiRenDopa]

My current fave (pithy, witty, and insightful, all in one)

[...]

It's very amusing that someone with essentially no understanding of quantum mechanics whatsoever thinks they can bring down the current paradigm in cosmology with reference only to an uncaptioned diagram from wikipedia about the Casimir effect, an effect they have tried to attribute to neutrinos.

There are many pithy statements in this thread, some of which are witty.

There are also many insightful statements (and posts) in this this thread, some of which are (relatively) pithy.

I haven't been keeping track - maybe I, or someone else?, should start? - but this recent one by Tubbythin must surely be one of the best!

Any other nominations? Please be sure that the content is also directly applicable to the topic of this thread ...

 

[edd]

Well I thought I'd done quite well with that jab about not being able to do quantum mechanics with cartoons unless you were Richard Feynman ;-)

 

[DeiRenDopa]

Pithy, witty, and insightful (another nomination)

Well I thought I'd done quite well with that jab about not being able to do quantum mechanics with cartoons unless you were Richard Feynman ;-)

This one?

That image is little more than a cartoon. Those blue arrows are not really a good representation of the pressure.

You cannot do quantum mechanics with cartoons.






Unless you're Richard Feynman.

I agree, it is very good ...

... and I'm sorry to say that I somehow missed it (as in, I didn't even read it )

Any more nominations?

 

[The Man]

Any more nominations?

Well, I’ll have to give edd the highest marks for pith and relevance, but understandably I would like to include my own remarks in this exchange.

Do you have some fixation on astronomers specifically? Were you scared by an astronomer as a child?

No, actually I was highly impressed with them prior to Guth's introduction of metaphysics into the mix. By then I was in my early 20's and they certainly didn't scare me and the still do not scare me. J

So they just broke your heart by utilizing the known aspects of quantum physics that you believe are “physically impossible”, how sad.

 

[The Man]

Since MM seems unable to argue his point about the Casimir force and zero point fluctuations in any consistent manor. Constantly using references that describe the Casimir force as arising from the fluctuations of the zero point field that he claims is ‘physically impossible’. I present the following paper for review and comment.



http://cua.mit.edu/8.422_S07/Jaffe2005_Casimir.pdf

It should be noted that the paper does not assert negative pressure or vacuum field fluctuations as a ‘physical impossibility’, but simply asserts that those fluctuations may not be responsible for the Casimir Force. In fact the author remarks to his own doubts that there could be “a consistent formulation of relativistic quantum mechanics in which zero-point energies never appear”. It should also be noted that the explanation given relates to the properties of the materials of the plates and as such the resulting forces act between the plates only. So any thoughts MM, Casimir force resulting from quantum fluctuations in the zero point field that you claim is a ‘physical impossibility’ yet continue to provide references that explain it as such or perhaps, as noted in the paper linked, the interactions of material properties that act solely between the plates? I should caution you that the paper is replete with math and although some of the ‘pictures’ have arrows and squiggly lines, they may not be representations you are accustom to seeing. Unless you’re accustom to Feynman diagrams.

 

[Tim Thompson]

Feynman on Diagrams

Well I thought I'd done quite well with that jab about not being able to do quantum mechanics with cartoons unless you were Richard Feynman ;-)

I found this in one of my quantum field theory text books, but I can't remember where. It's Feynman talking about Feynman diagrams.

I was sort of half-dreaming, like a kid would … that it would be funny if these funny pictures turned out to be useful, because the damned Physical Review would be full of these odd-looking things. And that turned out to be true.

 

[edd]

I certainly can't nominate myself...
It's difficult to pull a soundbite out of http://www.internationalskeptics.com/forums/showpost.php?p=4638737&postcount=2076 but it's a great post by ben m.
http://www.internationalskeptics.com/forums/showpost.php?p=4602543&postcount=1996 presents a great trichotomy.

There have been some excellent posts in this thread which have prompted considerable thought on my part and which have led me to a much better understanding of this whole business, and a greater clarity of many aspects of this in my own head. For that I'm grateful, and at the end of the day it's definitely worth the exasperation I have frequently felt.

 

[ben m]

Since MM seems unable to argue his point about the Casimir force and zero point fluctuations in any consistent manor. Constantly using references that describe the Casimir force as arising from the fluctuations of the zero point field that he claims is ‘physically impossible’. I present the following paper for review and comment.

http://cua.mit.edu/8.422_S07/Jaffe2005_Casimir.pdf

I've been to one of Jaffe's seminars on this topic, and asked him a few questions afterwards, and in consequence I think understand his technique reasonably well. (Famous last words!) In order to calculate the energy of any system---be it (a) the vacuum or (b) the vacuum plus two conducting plates---you start writing down all of these standard field-theory loop diagrams. It turns out that the list of such diagrams is infinite, which has been well-known since Feynman. In order to calculate any measurable quantity, though, like a scattering amplitude or a mass or a force, there's a way to reorganize the equations that makes it clear that the measurable quantity will be finite.

For the Casimir force, there are two ways to approach the infinite list. Casimir started by taking the full infinite list of QED terms for the vacuum, then showing that a handful of them are removed if there are conductors present. That handful of terms represent the component of the energy density which is affected by the plates, which gives you the force (via, I might add, p = -dE/dV) and you don't care that the remaining terms are infinite. Jaffe points out that you can do it the other way---start with the QED representation of the plates, then *start* writing the list of fields which are affected by them, which he did with some nifty scattering theory. This gets you to Casimir's same finite list, and to the same force, but by treating it this way, you can stop writing the list of terms before you get to the infinite (but force-free) part. (This "know when to stop computing" has been built into scattering theory for a long time, and it's basically where the whole renormalization thing got started.)

This is also the same as saying that the Casimir effect only probes the modes that couple to the plates. If you fill the vacuum with virtual neutrinos-antineutrino pairs, the plates do not remove these energies from Casimir's list, nor add them to Jaffe's list, no matter what their total energy is, and so they do not appear in the force.

You could also say something like "The Casimir effect is just a test of cavity QED", or that "The Casimir force is just a probe of the plate-plate coupling via virtual particles", and I think those would be fair statements. But a similar statement is true of every measurement in quantum mechanics---you only ever measure the diagrams that you couple to, never the ones you don't. In the Casimir effect, by moving the plates closer together you are coupling to more and more diagrams, and I think in the limit of d = 0 you're coupling to "all of them" in some sense. (Or maybe it's just (1/137)^2 of them?) The diagrams which were "decoupled" and invisible at d = 1um will go ahead and couple in at d=0.5um, and so on; in a sense, this correctly-predicted d-dependence shows that these diagrams were there all along. (I could give a list of similar "it was there all along" effects from experimental particle physics.) But it doesn't tell you whether or not your computations for d=0.1nm are wrong or not---the measurement at plate separation d doesn't tell you what is (or is not) waiting to couple in at plate separation d/2, and in that sense it doesn't probe the full vacuum energy.

But it does probe part of the vacuum energy. And you don't need the full vacuum energy to see that P < 0 for the components we do see.

It's all very interesting, though, since scattering theory gives you the tools to calculate the Casimir forces on arbitrarily-shaped objects, which were impossible to do with other approaches. If you include enough detail about the electromagnetic properties of the plates, Jaffe's approach also makes explicit the transition between the Casimir force and the van der Waals force---which, being electromagnetic in nature, can of course be written as a bunch of QED diagrams which show up in your big list.

 

[sol invictus]

The formula is only a gross approximation of the pressure *difference* and it is an oversimplification of the actual physical process.

So you think it's wrong.

There's nothing wrong with the WIKI article, although I could nitpick a word or two.

And in the next sentence, you think it's right.

I give up. The old saying holds perfectly here: "Never argue with a fool, they will lower you to their level and beat you with experience."

But, Michael, you don't even have the math skills necessary to balance your check book.

Precisely. And Michael - you do realize that's completely obvious to everyone, more and more so with every one of your posts, right?

 

[The Man]

..<snip>
It's all very interesting, though, since scattering theory gives you the tools to calculate the Casimir forces on arbitrarily-shaped objects, which were impossible to do with other approaches. If you include enough detail about the electromagnetic properties of the plates, Jaffe's approach also makes explicit the transition between the Casimir force and the van der Waals force---which, being electromagnetic in nature, can of course be written as a bunch of QED diagrams which show up in your big list.

Thanks Ben, a fine analysis. I am glad to hear that you attended one of the seminars and were able to ask some questions. I am also glad to learn that my amateurish assessment was correct that in both cases it is still just “the plate-plate coupling via virtual particles”. Although I was a bit fuzzy on exactly how the two approaches related. I found it interesting as well, which is why I posted it and I was also curious as to how it does influence the calculation of Casimir forces for different configurations. So thanks again, Ben, it is always helpful to get so input from someone with some first hand or second quantization experience.

 

[Reality Check]

Then all you have to do is take that "positive force" (arrows point in) and divide it by the *positive area* and you end up with a *POSITIVE PRESSURE* everywhere, on every surface! Even your tank analogy demonstrates your own ignorance of "pressure". You have "positive pressure" on the inside of the tank that is "greater than" the outside pressure, and no region experiences "negative pressure". You really are clueless when it comes to actual physics. Evidently a "minus sign" in a math formula is all that you actually "understand". The physical processes are evidently a complete and total mystery to you.

You really are clueless when it comes to actual physics.

• You do not know that you can add up forces to get a net force.
• You do not know that the force on an object is not each individual force but the total of the forces (the net force).
• You do not know that pressure is the total force per unit area.

If we wanted the pressure on each surface according to the diagram that you are obsessed with then you are right - there is a positive pressure (note the absense of quotes) on each side of the plate. But as any high school student knows we can draw an equivalent diagram where the forces are added and then there is a naegative pressure between the plates. This is the actual physics.