Lambda-CDM theory - Woo or not?

[Reality Check]

http://physicsworld.com/cws/article/news/32380

Don't like an EM oriented explanation? Here, let's try one based on "VP's". The diagram arrows point exactly the same way, namely *into* the plates. Why?

http://www.casimir.rl.ac.uk/

http://www.casimir.rl.ac.uk/casimir-plates.gif

Notice how all the arrows point towards and not away from the plates just like the WIKI diagram?

http://upload.wikimedia.org/wikiped...simir_plates.svg/300px-Casimir_plates.svg.png

Why do all these arrows in both of these diagrams point into the surfaces of every plate? Did both of these guys "screw up" when they created their diagrams of the direction of force?

Because the authors are showing that the force on each side of each plate (the arrows) is different.

Every physicist (and most high school students) knows that the disgrams are the same as ones in which there are no forces on the outside and forces directed away from the plates between the plates.

 

[Reality Check]

No you don't. You understand how to mechanically run through the math, but you don't understand the physical process at all. You seem to believe that a minus sign in your math formula demonstrates "negative pressure in a vacuum", but all it demonstrates is a "pressure difference" between the inside and outside of the plates, much like RC's pressurized tank analogy.

It is not an analogy. It is your reasoning applied to another situation.

You have stated that the pressure on the plate = outside pressure - inside pressure. This results in a positive pressure in the Casimir effect. It results in a negative pressure for a pressurized tank. It results in a positive pressure for a vacuum chamber.

But in order to get your reasoning physically correct then we need to have pressure = inside pressure - outside pressure to give positive pressure for a pressurized tank. The pressure difference in the Casimir case is then negative (subtract a big number from a smaller number and you get a negative number). Then the "MM pressure" for a vacuum chamber is negative!

The fact is that pressure is not the difference in prressure on the sides of the container or plates.

Pressure (symbol: p or sometimes P) is the force per unit area applied to an object in a direction perpendicular to the surface. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.

You have pressure confused with gauge pressure.


Then you went on a rant about the pressure on each surface in the diagram being positive. That just happens to be correct for the diagram as drawn. But:

1. It also has nothing to do with the pressure on each plate.
2. Every physicist (and most high school students) knows that the diagram are the same as one in which there are no forces on the outside and forces directed away from the plates between the plates.

 

[sol invictus]

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.

Hmmm... let's see about that. Suppose we model the plate itself as a solid slab of nearly ideal conductor (zero EM field inside, at least up to some cutoff frequency). Forget about the other plate for now.

Question: if the plate is a little springy, so it can slightly increase or decrease its volume without loosing its conductivity, which will it do? In other words, will it be squeezed or stretched? You can assume it's in a vacuum, with no external forces acting on it.

Maybe we should let MM answer, since he understands physics so thoroughly.

 

[Reality Check]

FYI, I tend agree with you on this topic. Most "black hole" critics are fixated on the term "singularity" due to the divide by zero problem whereas the density of a mass object may not need not need to achieve "infinite" density to form an event horizon.

I will be pedantic about one thing here: If the density of an object is high enough General Relativity (and even Newton's theory of gravitition) tells us that an event horison will form. You imply that it is optional.

 

[Tubbythin]

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 ...

Why thank you DRD.

My personal fave:

That is not what I'm trying to suggest. I don't really have a problem with the idea that the universe isn't controllable. I have a problem with attempting to claim inflation or DE has some influence on the universe if you can't even make them show up in a laboratory experiment here on Earth. If they don't show up here, why should I believe they have some influence somewhere "out there" in space?

And when you find that simple-Earth-experiments can't exactly reproduce something you see in space---what are you going to do? Give up? File a complaint with God? "I expected you to make the Big Bang using only forces that appear below the TeV scale. You did it wrong."

 

[Perpetual Student]

Has the question about this equation been answered? Perhaps I missed it.

 

[Tim Thompson]

Everybody - No Math! No Math! No math!

Has the question about this equation been answered? Perhaps I missed it.

But that's just mathematics, not physics, so of course it must be wrong, don't you know?

 

[The Man]

Well, like most of us, I doubt PS has seen the physics picture that MM keeps tucked away in his wallet and uses to determine what is and is not physically possible. Unfortunately it must be a very old picture and physics has grown up a lot since then, apparently as MM does not seem to recognize that it is still physics.

 

[derekmcd]

Michael,

You have referred to the pressures equivalent to 1 atm on several occasions (a measurement we all agree on). In order for your notion of both pressures being positive, you need to explain how the pressure outside the plates, in a vacuum, is greater than 1 atm (to compensate for a positive pressure between the plates).

 

[Michael Mozina]

Because the authors are showing that the force on each side of each plate (the arrows) is different.

That's the whole point! No area experiences "negative" force or pressure, just "less" on one side than another! Grrr. Arguing with creationists is *sooooooo* frustrating!

FYI, I'm swamped at work at the moment and this conversation is not a 'priority' to me at this point. I'll continue to check in from time to time, but my basic question has been answered to at least my personal satisfaction. It's painfully clear to me that all you folks 'understand' is a math formula. If there is a minus sign in the formula it *must* be an "absolute negative" number evidently. You can't even conceive of the idea of "less pressure" and "more pressure" and the notion of an *OVERSIMPLIFIED* math formula. In your mind it a "negative pressure" even though both sides of both plates experience positive force and positive pressure. Gah.

Like I said, this conversation has gone about the way I figured. You can't justify *any* of your statements or beliefs in terms of actual 'physics'. If it looks good on paper, it *must* be true, and anything is acceptable as long as there is a math formula associated with the idea. Invisible elves are fine as long as there is a "point at the sky" math formula to describe it. Put a minus sign in front of the invisible elves and you've just demonstrated "negative elves in a vacuum". Sheesh.

FYI, it is physically *impossible* to achieve even "zero pressure" in any vacuum anywhere. It's is therefore physically *impossible* to achieve negative pressure in a vacuum. There are only two possibilities here, the one I mentioned, and wiki mentioned and the VP explanation mentioned, and the PHYSICS reference mentioned. The other possibility is that there is a physical exchange of particles between the plates. None of this demonstrates "negative pressure in a vacuum". All the blue arrows point *into* the plates, not away from any surface of any plate.

There is simply a "pressure difference" or a "force difference" between the outside surface of the plates and the inside surface of the plates. The little blue arrows between the plates point *into* each of the plates.

 

[ben m]

FYI, it is physically *impossible* to achieve even "zero pressure" in any vacuum anywhere. It's is therefore physically *impossible* to achieve negative pressure in a vacuum.

You're back to thinking about the ideal gas law, aren't you? Please stop. Just stop. It hurts. It is practically impossible to achieve zero kinetic pressure in a molecular gas and nonsensical to achieve negative kinetic pressure in a molecular gas.

The Casimir effect has nothing whatsoever to do with kinetic pressure.

 

[Ziggurat]

You're back to thinking about the ideal gas law, aren't you? Please stop. Just stop. It hurts. It is practically impossible to achieve zero kinetic pressure in a molecular gas and nonsensical to achieve negative kinetic pressure in a molecular gas.

Actually, that's not even quite true. Because of inter-molecular attractions, you can in principle have negative pressures in a molecular gas. And the Van der Waals equation (which is much more accurate than the ideal gas law for real gasses) does have solutions with negative pressure.

 

[Ziggurat]

The little blue arrows between the plates point *into* each of the plates.

Back to argument by picture, which is the best you can ever do. Slight problem: the picture is wrong. Notice the green wavy lines. Tell me, Michael, what are those wavy lines supposed to represent? And whould the surface of the plates be at a node or an anti-node of those wavy lines? And which way is it drawn?

 

[Michael Mozina]

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

In quantum field theory as usually formulated, the zeropoint fluctuations of the fields contribute to the energy of the vacuum. However this energy does not seem to be observable in any laboratory experiment.

Any "scientific" paper that begins with this sort of obviously *false* assertion is hard to take seriously. Give me a break. *Almost *EVERY* lab experiment on absolute zero demonstrates the influence of the energy from the vacuum.

http://en.wikipedia.org/wiki/Absolute_zero

Absolute zero is a temperature marked by a 0 entropy configuration. It is the coldest temperature theoretically possible and cannot be reached by artificial or natural means. Temperature is an entropically defined quantity that effectively determines the number of thermodynamically accessible states of a system within an energy range. Absolute zero physically possesses quantum mechanical zero-point energy. Having a limited temperature has several thermodynamic consequences; for example, at absolute zero all molecular motion does not cease but does not have enough energy for transference to other systems, it is therefore correct to say that at 0 kelvin molecular energy is minimal.

 

[Michael Mozina]

Back to argument by picture, which is the best you can ever do. Slight problem: the picture is wrong.

So the second picture is 'wrong' too? Both authors are wrong and so is the physics reference I cited?

Notice the green wavy lines. Tell me, Michael, what are those wavy lines supposed to represent?

Well, lets see what that author 'said' about them.
http://physicsworld.com/cws/article/news/32380

The quantum Casimir effect comes about because a vacuum always contains fluctuating electromagnetic fields. Normally these fluctuations are roughly the same everywhere, but two close conducting surfaces set “boundary conditions” that limit the number of allowed field frequencies between them. Only waves that can fit multiples of half a wavelength between the surfaces resonate, leaving non-resonating frequencies suppressed.

The green wavy lines are the fluctuations in the electromagnetic fields. Normally they are the same everywhere, but in this case they are "greater" on the outside of the plates and "less" between the plates. What is the result of that configuration?

The result is that the total field inside a gap between conductors cannot produce enough pressure to match that from outside, so the surfaces are pushed together.

Notice it doesn't say "pulled" together? Why is that? He's wrong too?

 

[Skwinty]

See note 1:http://cua.mit.edu/8.422_S07/Jaffe2005_Casimir.pdf

[1] I use the conventions of Ref. [2] and, in particular, take​

g​

​

​

​

 ​

 diagf1; 1; 1; 1g, so E > 0 corresponds to a positive​

energy density and a negative pressure.

 

[Michael Mozina]

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.

I didn't rely *only* on Wiki Tim. I provided you with two verbal descriptions of this process from two different authors, and I cited two different drawings both of which I am to presume are "wrong" as well?

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.

So sayeth Tim? It certainly does jive with the physics explanation of this process too Tim. Was he "wrong" too?

http://physicsworld.com/cws/article/news/32380

The quantum Casimir effect comes about because a vacuum always contains fluctuating electromagnetic fields. Normally these fluctuations are roughly the same everywhere, but two close conducting surfaces set “boundary conditions” that limit the number of allowed field frequencies between them. Only waves that can fit multiples of half a wavelength between the surfaces resonate, leaving non-resonating frequencies suppressed. The result is that the total field inside a gap between conductors cannot produce enough pressure to match that from outside, so the surfaces are pushed together.

It says the plates are "pushed" together. Why?

Positive pressure pushes the plates together from the outside.

Yep. Blue arrows point into the plates on the outside. So far, so good.

Negative pressure pulls the plates together from the inside.

Bzzt. Blue arrows point *INTO* the plates Tim. No arrows point *away from* the plates.

The Casimir force pulls the plates together from the inside.

No, it says they are "pushed together" Tim,not "pulled together from the inside.". Notice which direction the inside arrows point Tim. So you wish me to believe all three of these explanations and diagrams are "wrong"?

http://www.casimir.rl.ac.uk/

 

[Ziggurat]

So the second picture is 'wrong' too?

The wikipedia picture you keep using is wrong. I don't know which second picture you're referring to, nor do I care.

Well, lets see what that author 'said' about them.

So a dumbed-down description with no calculations is all you're willing to cite, and no actual calculations should ever be considered, because that might contradict your favorite story.

The green wavy lines are the fluctuations in the electromagnetic fields.

OK, so what about my other question: should the surface be a node or an anti-node? And which way are they drawn in the picture? Do you even know?

What is the result of that configuration?

I keep offering to walk you through figuring that out, and you've ignored it every time. What happens is that E(V) doesn't change much at all outside the plates because plate motion hardly changes the external modes. So the derivative with respect to volume is close to zero, and so is the pressure. But inside the plates, expanding the volume permits more modes between the plates, increases the energy significantly with increasing volume. We then have a positive derivative or energy with respect to volume, and hence a negative pressure. But of course, that requires understanding how to define pressure, as well as being able to then use that definition to do an actual calculation. And you've demonstrated repeatedly that you're not up to either task.

Notice it doesn't say "pulled" together? Why is that? He's wrong too?

Wow, who'da thunk that an article written for a general audience might use descriptive language a little loosely.

 

[Reality Check]

That's the whole point! No area experiences "negative" force or pressure, just "less" on one side than another! Grrr. Arguing with creationists is *sooooooo* frustrating!
...snipped usual rant....

That is the whole point.
The authors want to illustrate in their diagram that the separate forces on each side of the plates are different - for the purposes of illustration only. Your delusion is that the diagram is the basis of the Casimir calculations. It is not. Casimir never saw this diagram.

Any compentent scientist knows about that to calculate the pressure between the plates, the first step is to calculate the force between the plates, i.e. the net force. To do this they add the forces and find that there is an attractive force (pointing away from the plates). By definition this is a negative pressure. Acompentent scientist actually does the mathematics and experiments to confirm this. Casimir did the mathematics, many others did the experiments.

Grrr. Arguing with an delusional person is *sooooooo* frustrating !

 

[GeeMack]

Michael...

The wikipedia picture you keep using is wrong.

Go look in a physics book for a change.

Any compentent scientist knows about that to calculate the pressure between the plates, the first step is to calculate the force between the plates, i.e. the net force. To do this they add the forces and find that there is an attractive force (pointing away from the plates). By definition this is a negative pressure. Acompentent scientist actually does the mathematics and experiments to confirm this. Casimir did the mathematics, many others did the experiments.

Oh, there's the problem right there. Mathematics and calculations and all that messy stuff. That's not for Michael and his non-existent math skills. No way. Obviously he'd prefer to just stick with the pretty little pictures, thank you very much.