Lambda-CDM theory - Woo or not?

[temporalillusion]

Tell him about negative temperature. Maybe he'll explode from rage and leave the forum in peace.

Lol awesome, consider my mind blown!

 

[The Man]

No, there is no area in the experiment that experiences ''negative pressure"! The whole thing can be done in virtually *any* positive pressure environment and we can't even make a "pure vacuum" with *no pressure", let alone "negative pressure".



Now your just confusing force with pressure. The "force" is actually coming from the *outside* of the plates. Anything inside the plates is due to molecular attraction. There is no "negative pressure" involved.



Hoy. No. We are left with *subatomic pressure* in the form of EM carrier fields. I botched my explanation to Derek by using the term "magnetic plates" when I meant "metallic plates", but the rest is valid. The whole reason that the type of material is relevant is because EM fields have unique effects on many metallic objects like steel. This tells us the carrier particles involved, but it has nothing whatsoever to do with "negative pressure".



Why do they report "magnetic reconnection"? Beats me. Pressure and force are not the same. I have have positive pressure in the chamber and "directional force" that pushes the plates together. That's all that is happening here.



I was only trying to use the idea as an *analogy* and all that did is create pure confusion. As I noted earlier on several occasions, the WIKI explanation is quite valid. Where does it say "negative pressure" exactly in that article by the way?

Those arrows are in fact "pressure". There is "more pressure" on the outside of the plates, and 'less pressure" between them, but even the subatomic process is based on "more kinetic energy on the outside and less of it on the inside". It's all positive kinetic pressure, even at the subatomic level. There is simply "more force" outside the places than inside the plates due to "positive kinetic pressure".

Well you were almost starting to get it there with “directional force”. A force, as a vector, has direction. For any direction that we ascribe as positive the opposite direction would be negative and so would a force applied through that direction. You seem to be focusing on absolutes or negative values as only less then zero. In geometry negative also denotes direction and not simply a location to the left or right of some absolute zero point. It is in fact the vector additions of these + and - directions of force that demonstrate Newton’s third law (equal and opposite reaction), as well as the conservation of energy. As has been explained to you before the repulsive forces are generally considered positive or a positive vector (along a positive radial or planar direction) making attractive forces negative.

 

[Ziggurat]

The term "negative pressure" is a misleading idea, since all you are doing is "stressing' the bonds of the atoms in the liquid, much like you could also do with a solid.

What in the world do you think the term "pressure" actually means? I've asked you this directly, because I think it's absolutely at the heart of your miscomprehension, but you didn't answer. I gave my definition. In fact, I gave two definitions that work. You have not said you agree with them, but you haven't objected to them either. Until we settle that, we will not get any further.

It's pure stress!

So what? It still produces negative pressure, according to the definitions of pressure I gave you. If you want to propose your own definition of pressure, feel free to do so. Until then, I'm using my definition, and stress can produce pressure. No surprise there.

It's would be like putting solid gelatin in the container and doing the same thing.

Well, yes. Except that solids can sustain non-symmetric stress as well (meaning different stresses in different directions), whereas liquids cannot. In mathematical terms, stress is a 3x3 symmetric tensor, which means 6 independent parameters, all of which can be different for a solid. But for a liquid (and a gas), the stress tensor is necessarily diagonal, with those diagonal elements equal to the pressure.

You could do that with virtually any solid too if you attached the piston to the solid.

Not quite. The stresses would not be symmetric in that case, but uniaxial, so categorizing the resulting stress tensor with a single number would not make sense.

Come on. You're changing terms as go.

Not at all. I have from the beginning used a very basic and very common definition of pressure. And everything I have said has been consistent with that definition. You, on the other hand, have never given any definition. Do you even have one? I cannot even tell if you've been consistent, because I still don't know what on earth you mean by the term.

First we were talking about negative pressure in a vacuum. Now you're trying to compare that to stress on bonds in a liquid. These are not the same concepts

Sure they are, because the details of the mechanism are irrelevant for the definition I'm using, which (once again) is
[latex]$P=-\frac{\partial E}{\partial V}$[/latex]

These are two *entirely* different circumstances in the first place.

In the sense that our function for E is different, yes. In the sense that the definition I gave for pressure still applies, no, it's exactly the same.

So once again: do you understand the definition of pressure I gave? Do you accept that definition of pressure? There is no point in proceeding further if we cannot even agree on what the term "pressure" means.

 

[Ziggurat]

Were you intending to use a Kelvin scale or some other scale?

Oh, so you don't know about negative temperatures. Not that I'm surprised. But yes, negative temperatures on absolute temperature scales do exist. They are actually what you would conventionally think of as hot, they only occur in certain sorts of systems, and they are unstable configurations, but they are quite real. And yes, you can even make them in a lab.

 

[sol invictus]

Lol awesome, consider my mind blown!

It pretty simple, actually. If you want your definition of temperature to be consistent with the laws of thermodynamics, dE = T dS, where E is the energy and S the entropy. So 1/T = dS/dE. Therefore if we can find a system in which the entropy decreases as the energy increases, it will have negative temperature.

But that's easy: consider a system of N quantum 1/2 spins in a magnetic field. The ground state is all spins aligned with the field. The total number of states is 2^N, so the maximum entropy is N log 2, and that maximum entropy state consists of the spins aligned randomly (N/2 pointed up, N/2 pointed down). But that state is plainly not the maximum energy state (all spins anti-aligned with the field is). Therefore S(E) reaches a maximum somewhere between the ground state and the maximum - and so T goes to +infinity, wraps around to -infinity, and increases from there as you increase E .

 

[Michael Mozina]

Well you were almost starting to get it there with “directional force”. A force, as a vector, has direction. For any direction that we ascribe as positive the opposite direction would be negative and so would a force applied through that direction. You seem to be focusing on absolutes or negative values as only less then zero. In geometry negative also denotes direction and not simply a location to the left or right of some absolute zero point. It is in fact the vector additions of these + and - directions of force that demonstrate Newton’s third law (equal and opposite reaction), as well as the conservation of energy. As has been explained to you before the repulsive forces are generally considered positive or a positive vector (along a positive radial or planar direction) making attractive forces negative.

IMO, this seems to be the problem in a nutshell. Guth (and the mainstream) is confusing "pressure" with "force". Guth's theory specifically requires "negative pressure" from a "vacuum", not an "external force". These are horses of an entirely different color.

 

[The Man]

IMO, this seems to be the problem in a nutshell. Guth (and the mainstream) is confusing "pressure" with "force". Guth's theory specifically requires "negative pressure" from a "vacuum", not an "external force". These are horses of an entirely different color.

Not at all, as has already been pointed out to you, pressure is just force over area; with a negative force you have negative pressure. Once again this is required by Newton’s third law and the conservation of energy. Without the negatives those laws just don’t add up.

 

[Ziggurat]

IMO, this seems to be the problem in a nutshell. Guth (and the mainstream) is confusing "pressure" with "force".

He's using exactly the same definition I've been giving to you:
[latex]$P=-\frac{\partial E}{\partial V}$[/latex]
Do you understand this definition of pressure? Do you accept it? Or do you want to use a different definition? If so, tell us what definition of pressure you want to work with. But without knowing what definition you are using (and given your denial that liquids can be at negative pressures, you're obviously not using that one), there's no chance for any common ground.

 

[Michael Mozina]

What in the world do you think the term "pressure" actually means?

Evidently it means something very different to you than what it means in ordinary physics and vacuums. You're confusing pressure and force. While it is entirely possible that there is some 'external force' pulling on the process (like your piston example), there is no such thing as a "negative pressure" in a "vacuum". These are entirely *different* ideas and concepts. I'm not even going to worry about the rest of your post until you recognize this distinction.

There is no "negative pressure" in a Casimir experiment, just "force" being applied to the plates from the quantum realm. There is no "negative pressure" involved, just "force". The idea that "force" can be looked at in a similar manner as "pressure", does not give Guth the right to interchange these terms. They are not one and the same concept. "Pressure" in a "vacuum" could theoretically reach a "zero", but it can never achieve "negative pressure". There certainly could be some "external force" tugging on the near singularity thingy he has going, but there is no such thing as "negative pressure" in a vacuum, and that is what Guth's theory specifically requires and needs in order to function. It's dead in the water because he confused "pressure" with "force'.

 

[temporalillusion]

It pretty simple, actually. If you want your definition of temperature to be consistent with the laws of thermodynamics, dE = T dS, where E is the energy and S the entropy. So 1/T = dS/dE. Therefore if we can find a system in which the entropy decreases as the energy increases, it will have negative temperature.

But that's easy: consider a system of N quantum 1/2 spins in a magnetic field. The ground state is all spins aligned with the field. The total number of states is 2^N, so the maximum entropy is N log 2, and that maximum entropy state consists of the spins aligned randomly (N/2 pointed up, N/2 pointed down). But that state is plainly not the maximum energy state (all spins anti-aligned with the field is). Therefore S(E) reaches a maximum somewhere between the ground state and the maximum - and so T goes to +infinity, wraps around to -infinity, and increases from there as you increase E .

Thanks! Yeah the example I was reading had them on a 1 dimensional wire, but the same thing.

 

[Michael Mozina]

He's using exactly the same definition I've been giving to you:
[latex]$P=-\frac{\partial E}{\partial V}$[/latex]
Do you understand this definition of pressure? Do you accept it? Or do you want to use a different definition? If so, tell us what definition of pressure you want to work with. But without knowing what definition you are using (and given your denial that liquids can be at negative pressures, you're obviously not using that one), there's no chance for any common ground.

It is not even reasonable for you to be comparing a "liquid" to a "vacuum". Guth specifically states that there is "negative pressure" in a "vacuum". He did not state anything about a liquid. This is ultimately a red herring unrelated to his claim, and another excellent example of your confusion between "force" and 'pressure'.

 

[GeeMack]

Mathematics can indeed correctly describe the physical processes of nature, but physics is a physical process that can often be very difficult if not impossible to correctly mathematically model.

Impossible for you because you can't do math.

 

[Michael Mozina]

Impossible for you because you can't do math.

No, this is another really excellent example of the idea that your side cannot distinguish between a math formula and physical reality. In physical reality a "vacuum" can achieve a zero energy state, at least in theory. It could *never* achieve a 'negative pressure' because such a concept is physically impossible. It's a mathematical mythos that Guth created because he didn't pay attention to the realm of actual "physics". There's no point in comparing "liquids", to "vacuums", but of course you'd love to simply ignore the *physical differences* between the two environments. You folks may be able to do math, but your understanding of physics is severely lacking. In the language of "physics", liquids != vacuums, and "pressure != force".

 

[Ziggurat]

It is not even reasonable for you to be comparing a "liquid" to a "vacuum".

Once again, you are ignoring the question of the definition of pressure. Do you or do you not accept the definition of pressure I gave? If so, then we can apply it to liquids, we can apply it to gasses, and we can apply it to vacuums, and see what we get each time. But until you either accept the definition I gave you or suggest your own, there's not going to be any progress.

Is your hesitation to respond because you don't understand what that equation means? I actually hope you can, but you're so unfamiliar with so many things in physics, and you've yet to show that you can do any math at all, so at this point I'm actually not optimistic.

 

[Michael Mozina]

He's using exactly the same definition I've been giving to you:
[latex]$P=-\frac{\partial E}{\partial V}$[/latex]
Do you understand this definition of pressure? Do you accept it? Or do you want to use a different definition? If so, tell us what definition of pressure you want to work with.

Ok, let's say we try....

[latex]$P=-\frac{\partial (MC^2)}{\partial V}$[/latex]

 

[The Man]

No, this is another really excellent example of the idea that your side cannot distinguish between a math formula and physical reality. In physical reality a "vacuum" can achieve a zero energy state, at least in theory. It could *never* achieve a 'negative pressure' because such a concept is physically impossible. It's a mathematical mythos that Guth created because he didn't pay attention to the realm of actual "physics". There's no point in comparing "liquids", to "vacuums", but of course you'd love to simply ignore the *physical differences* between the two environments. You folks may be able to do math, but your understanding of physics is severely lacking. In the language of "physics", liquids != vacuums, and "pressure != force".

Cannot distinguish? That is kind of the whole point, to model physical events so accurately that the mathematical results are ‘indistinguishable’ from the observed results. Just what do you think physics is anyway? Now feeling the sun on your face, a nine volt battery on your tongue or whatever you can find at Wall-mart may be what you consider physics but that is not going to get you very far at the Large Hadron Collider. Even if you do want to volunteer to stick your face in the detector array with your tongue sticking out and whatever you found at Wall-mart to see what you can detect in the collision? Most of us however, would prefer to just stick with the installed detectors and the applicable mathematics.

 

[Michael Mozina]

Cannot distinguish?

Nope. The Lambda proponents do not seem to respect or acknowledge the physical differences between "pressure" and "force", nor will they distinguish between liquids and vacuums. That's a serious problem at the level of physics.

That is kind of the whole point, to model physical events so accurately that the mathematical results are ‘indistinguishable’ from the observed results. Just what do you think physics is anyway?

As long as you're doing that with known and physically possible entities, I have no problem with that idea. When these mathematical models are based upon physical impossibilities and "ad hoc" forces of nature, then it's an entirely different issue.

Now feeling the sun on your face, a nine volt battery on your tongue or whatever you can find at Wall-mart may be what you consider physics but that is not going to get you very far at the Large Hadron Collider.

While the LHC is a perfect exactly of a real "science experiment" that has some hope of finding a Higgs, no hardware on Earth could ever be useful in finding a now nonexistent entity. I can appreciate the value of LHC as it relates to particle physics theory, but no such hardware could ever be useful in verifying inflation.

Even if you do want to volunteer to stick your face in the detector array with your tongue sticking out and whatever you found at Wall-mart to see what you can detect in the collision? Most of us however, would prefer to just stick with the installed detectors and the applicable mathematics.

Well, me too. Then again, this is a perfect example of "empirical physics" and "empirical experimentation". LHC is "by the book" physics. If you had such a "controlled experiment" underway to find and verify inflation, I wouldn't be squealing like a pig. Since that is a physical impossibility, what else is left but a giant leap of faith? Why should I hold belief in a dead and useless entity that was originally postdicted and predicated upon a physical impossibility, specifically a "negative pressure vacuum"?

 

[Ziggurat]

Ok, let's say we try....

[latex]$P=-\frac{\partial (MC^2)}{\partial V}$[/latex]

Let's not. Among other things, it's a poor way to try to calculate the pressure inside a black body cavity due to radiation, since photons are massless. Relativistic mass is an outdated and superfluous concept, one that pretty much no practicing physicist still uses. I'm in that group.

But do you even understand the equation I gave for pressure, or did you just try sticking in the one physics equation you ever wrote down into what I gave you?

 

[Michael Mozina]

Let's not.

Translation: No Michael, don't convert energy to mass because then my confusion between pressure and force becomes damn obvious!

 

[Ziggurat]

Translation: No Michael, don't convert energy to mass because then my confusion between pressure and force becomes damn obvious!

E=mc² works fine for masses at rest. If you want to apply it to masses in motion, then this equation is in effect defining what you mean by mass, namely what is termed "relativistic mass". But there's simply no need to ever do so. You can relate mass and energy perfectly well using invariant mass, using
E²=m²c⁴+p²c²Now, you could in principle substitute this equation (or, more specifically, the square root of this equation) into my definition of pressure, but since calculating the various components for all the constituent elements of the system is frequently much more difficult than calculating an overall energy function in terms of your macroscopic parameters, there's no bloody point. Which is why I said "let's not". Deriving the idea gas law from that equation would be a serious pain, because the calculations would become far more complex than they need to be if you just consider energy directly. Which is why nobody does that. But you can find a derivation of the ideal gas law directly from [latex]$P=-\partial E/\partial V$[/latex] rather easily in basically any thermodynamics textbook.

Besides which, it's an absurdity to think that my definition confuses pressure and force, or that the version you wanted clarifies that in any way. Just look at the units.