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

[schrodingasdawg]

I can elaborate on that if you tell me what types of terms you're wondering about (in the action? in the stress tensor itself? in Einstein's equations?).

I meant in Einstein's equations.

It's supposed to be constant over all space and time, yes. In the stress tensor, that means that its pressure is minus its energy.

Whether you think that means it's "intrinsic to the geometry of spacetime" is more or less up to you. Quantum vacuum energies have those features, but the magnitude and sign of the resulting cosmological constant depends on the spectrum of fields as well as the background geometry. To me, that doesn't sound very intrinsic.

I think this clarifies things a bit, though. Thanks.

 

[sol invictus]

I meant in Einstein's equations.

OK. While it's often written as a separate term in Einstein's equations, there's no need to do so. Just consider the CC to be one of the contributions to the stress-energy tensor (which in my opinion is the only sensible option), and then it's just part of T_\mu \nu with no extra term necessary.

For example, suppose (as is the case in the theory of inflation) the primary source of stress energy in the universe is a scalar field with a potential energy functional. Then by a standard procedure one can work out the stress-energy due to that scalar. Some of it comes from derivatives of the scalar, both temporal and spatial, and some of it comes from its potential energy. If the potential energy has a constant piece in it, that piece enters Einstein's equations exactly like a CC. It's not an analogy, it's literally identical in every respect. Similarly if the potential has a nearly constant piece, one gets something that behaves almost like a CC. Similarly quantum vacuum energy, which is certainly a contribution to the stress tensor, acts just a CC. Etc.

 

[schrodingasdawg]

Ah, okay. I get it now. Thanks.

 

[DazzaD]

And what is that security blanket? "Empirical tests", as in "done in a lab, here on Earth". That this prop is riddled with internal inconsistencies is not a problem for MM, because they can be transformed away by waving the 'qualitative' wand over them (no lab experiment has shown that two atoms attract each other gravitationally? no worries! two atoms, 10^23 atoms, they're all just atoms!).
.

Thank you... exactly where I was going with my posts that MM seems to have neglected of late.

That is exactly what I was going to point out, the limitations on experimental verification of Newton's Law of Gravitation on the 'everyday' scale.

I was hoping that hitting at something he would obviously hold as 'true' might make him question all this "empirical evidence" requirement of his for any theory in physics.

 

[GeeMack]

I was hoping that hitting at something he would obviously hold as 'true' might make him question all this "empirical evidence" requirement of his for any theory in physics.

You've heard the one about the snowball in Hell?

 

[ben m]

I was hoping that hitting at something he would obviously hold as 'true' might make him question all this "empirical evidence" requirement of his for any theory in physics.

Nope, we've been down that road N times. GR, gravity, top quarks, neutrinos, CP violation, I forget what all else. If you want to go for N+1, brace yourself for some more special pleading.

 

[edd]

What known type of "energy" possesses "negative pressure"?

Why is "negative pressure" necessary for expansion of matter if the sun manages to do it everyday with known forces of nature?

Look, this is getting beyond ridiculous Michael. I've been trying to lead you to water, but you just won't drink. Others have been doing the same.

The Casimir Effect is utterly unambiguously negative pressure. Your claims about pressure differences are a complete canard. Negative pressures are physical, but you insist on denying them on baseless grounds, and won't accept the cosmologies that come about that fit the data better than anything else you can offer by a mile and a half.

Lets talk about *springs*. Springs are bits of metal, things we can agree on. Springs exert forces, and if we put a certain number of consistently made springs per unit area, we have a force per unit area, or a pressure. We can make systems that exert pressure from springs. Things we can't argue about.

A spring can exert a force under tension or compression. Under compression, like a gas in compression, they exert a positive force, or, when we have springs per unit area, a positive pressure. Under tension, they exert a negative force, or a negative force per unit area - a negative pressure.

If we have some plate stuck between two springs (or sets of springs) in compression, we have something like a system of positive pressure gases. If we move the plate one way, we compress one side, do work on it, and the springs being compressed further store energy. In a positive pressure system, the thing being compressed stores energy.

In a system where the pressures are negative, the roles are reversed. The thing being compressed loses energy - a stretched spring gives energy up as it is relaxed into a more compressed state. In a negative pressure system, the thing being compressed releases energy. It is simply and directly related, completely unambiguously, in a mathematically watertight sense, to the energy stored on one side or another.

It has nothing to do with pressure differences. I might have springs in tension or compression differing on one side or another, but the direction the plate moves in - the pressure difference, has no impact on the energy storage of the spring - the absolute pressure.

You are consistently wrong about this, and it needs no exotic energy to make it clear that you don't understand what you are talking about. A set of flipping springs is enough.

 

[Reality Check]

I prefer a simpler explanation that Michael Mozina is either ignoring or cannot understand.
Consider a surface with two equal and opposite normal forces acting on it. The net force is zero and thus by definition the pressure is zero (p= F/A).

• Take away the force directed away from the surface. You now have a non-zero pressure X.
• Take away the force directed toward from the surface. You now have a non-zero pressure Y.

How do you get 2 non-zero pressures to add to zero pressure?
The answer is that pressure X or pressure Y is the negative value of the other pressure. The convention is that repulsive forces produce positive pressure and attractive forces produce negative pressure.

 

[Perpetual Student]

Look, this is getting beyond ridiculous Michael. I've been trying to lead you to water, but you just won't drink. Others have been doing the same.

The Casimir Effect is utterly unambiguously negative pressure. Your claims about pressure differences are a complete canard. Negative pressures are physical, but you insist on denying them on baseless grounds, and won't accept the cosmologies that come about that fit the data better than anything else you can offer by a mile and a half.

Lets talk about *springs*. Springs are bits of metal, things we can agree on. Springs exert forces, and if we put a certain number of consistently made springs per unit area, we have a force per unit area, or a pressure. We can make systems that exert pressure from springs. Things we can't argue about.

A spring can exert a force under tension or compression. Under compression, like a gas in compression, they exert a positive force, or, when we have springs per unit area, a positive pressure. Under tension, they exert a negative force, or a negative force per unit area - a negative pressure.

If we have some plate stuck between two springs (or sets of springs) in compression, we have something like a system of positive pressure gases. If we move the plate one way, we compress one side, do work on it, and the springs being compressed further store energy. In a positive pressure system, the thing being compressed stores energy.

In a system where the pressures are negative, the roles are reversed. The thing being compressed loses energy - a stretched spring gives energy up as it is relaxed into a more compressed state. In a negative pressure system, the thing being compressed releases energy. It is simply and directly related, completely unambiguously, in a mathematically watertight sense, to the energy stored on one side or another.

It has nothing to do with pressure differences. I might have springs in tension or compression differing on one side or another, but the direction the plate moves in - the pressure difference, has no impact on the energy storage of the spring - the absolute pressure.

You are consistently wrong about this, and it needs no exotic energy to make it clear that you don't understand what you are talking about. A set of flipping springs is enough.

Well done! What could be more obvious? Put a set of springs under compression by two parallel plates to which they are attached and we have positive pressure "pushing" the plates apart. Pull the plates apart until the springs are tense and we have negative pressure "pulling" the plates together. OK, MM what next?

 

[ben m]

I prefer a simpler explanation that Michael Mozina is either ignoring or cannot understand.
Consider a surface with two equal and opposite normal forces acting on it. The net force is zero and thus by definition the pressure is zero (p= F/A).

• Take away the force directed away from the surface. You now have a non-zero pressure X.
• Take away the force directed toward from the surface. You now have a non-zero pressure Y.

How do you get 2 non-zero pressures to add to zero pressure?
The answer is that pressure X or pressure Y is the negative value of the other pressure. The convention is that repulsive forces produce positive pressure and attractive forces produce negative pressure.

Sorry RC, this is basically wrong. You're mixing up force (a vector) and pressure (a scalar) in a way that's not going to go anywhere useful.

 

[Michael Mozina]

Look, this is getting beyond ridiculous Michael. I've been trying to lead you to water, but you just won't drink. Others have been doing the same.

Well, believe me edd, I appreciate your efforts. There's no one here who's understanding of GR theory I respect more, and no one here who's pure scientific curiosity and demeanor I respect more than you. IMO you and PS typify what I believe a good mixture of scientific curiosity and skepticism is all about. I admire and respect both of you and your efforts in this forum.

I feel the same sort of frustration from the other side of the aisle and I'll do my best to clarify my beliefs here so you understand them as I do. I ask you to "walk a mile in my shoes" here for a moment.

The Casimir Effect is utterly unambiguously negative pressure.

Absolute or relative pressure?

Your claims about pressure differences are a complete canard. Negative pressures are physical, but you insist on denying them on baseless grounds, and won't accept the cosmologies that come about that fit the data better than anything else you can offer by a mile and a half.

Wait a minute. The concept of relative and absolute pressure is not a "complete canard", it's an important issue, and the crux or our differences.

FYI, it is not that I do not accept "negative pressure". I'm sure you could produce "negative pressure" on the surface of a negatively charged surface by surrounding it with a positively charged case. I'm sure you could create "negative pressure" on the surface of a solid using a plunger scenario and a good liquid. What I do not accept is the notion of "negative pressure" in a "vacuum" that somehow pulls Guth's mass thing apart. Any residual QM energy in the 'vacuum' will attempt to push "into", not "away from" his mass thing.

Let's be clear, it's not the concept of "negative pressure' I object to, it's the concept of claiming a "vacuum" holds "negative pressure" without something external going on, like charge, gravity, etc.

Lets talk about *springs*. Springs are bits of metal, things we can agree on. Springs exert forces, and if we put a certain number of consistently made springs per unit area, we have a force per unit area, or a pressure. We can make systems that exert pressure from springs. Things we can't argue about.

Something tells me we'll figure out a way to argue about it, but I'm reading this and responding as I'm going, so I'm not sure exactly how that's going to happen yet. Big suspense.

A spring can exert a force under tension or compression. Under compression, like a gas in compression, they exert a positive force, or, when we have springs per unit area, a positive pressure. Under tension, they exert a negative force, or a negative force per unit area - a negative pressure.

Hmm. The plot thickens. Let's try too to look at the springs EVERYWHERE in the chamber, shall we?

If we have some plate stuck between two springs (or sets of springs) in compression, we have something like a system of positive pressure gases. If we move the plate one way, we compress one side, do work on it, and the springs being compressed further store energy. In a positive pressure system, the thing being compressed stores energy.

In a system where the pressures are negative, the roles are reversed. The thing being compressed loses energy - a stretched spring gives energy up as it is relaxed into a more compressed state. In a negative pressure system, the thing being compressed releases energy. It is simply and directly related, completely unambiguously, in a mathematically watertight sense, to the energy stored on one side or another.

Well, this seems like a "one sided", and "relative" (to one side of the plate) explanation. In QM the whole vacuum has has "springs". They come in various shapes and sizes, some large springs, some small springs. At large distances, many sized springs push against everything, all sides of the chamber, all sides of the plates, everything, and pretty much evenly. As the space between the plates decreases, only the smaller springs, the ones with tighter curls can fit between the plates, while the larger springs can no longer fit between the plates. The small springs between the plates become compressed. As the gap between the plates is reduced even further, only the smallest possible springs can fit between the plates. Meanwhile the outside of the plates has ever imaginable sized spring pressing the plates together.

There's still a relative/absolute pressure issue going on here. Your "perspective" of pressure if you will is "relative to' the inside of the plate without respect to the pressure on the other surfaces of the plate. It's just like that wing analogy. There's nothing wrong with your perspective as long as you realize it's a 'relative pressure', in this case purely relative to the inside surfaces, and purely relative to the outside "pressure" *if* it were zero, which it can never actually be.

It has nothing to do with pressure differences. I might have springs in tension or compression differing on one side or another, but the direction the plate moves in - the pressure difference, has no impact on the energy storage of the spring - the absolute pressure.

Well, I knew we'd have to figure out a way to disagree, and it's still related to this concept of absolute/relative. Your perspective of "pressure" is related to a relative pressure compared to an ambient pressure of all the springs on the outside of the plates.

You are consistently wrong about this, and it needs no exotic energy to make it clear that you don't understand what you are talking about. A set of flipping springs is enough.

You still have to put springs outside as well as inside the plates edd.

I ask you again, what kind of "energy density' has "negative pressure" on a surface of a sphere? Do you mean like if we charged the sphere relative to the chamber walls? How does that relate to Guth's concept of getting "negative pressure" out of a vacuum? Any connection?

 

[Michael Mozina]

Well done! What could be more obvious? Put a set of springs under compression by two parallel plates to which they are attached and we have positive pressure "pushing" the plates apart. Pull the plates apart until the springs are tense and we have negative pressure "pulling" the plates together. OK, MM what next?

I'm sure edd will think of something.

FYI, I recall you asked a question about my mathematical understanding of physics. I would best describe my calculus skills as somewhat rusty, but I still grasp the basic concepts, and I stay a little 'active' by reading various papers. I realize we can take derivatives of equations to find tangents, and integrate equations to find areas, etc.

As it relates to the finer points of GR, edd and sol would have far better math skills, and probably teaching skills related specifically to GR than I do if all you're interested in is the pure math "explanation".

Sometimes however more than math alone constitutes "knowledge", like in our debate about Einstein's original intent of adding the constant to GR. Virtually everything that sol said about the original formula was technically true, including the fact the formula was unstable in it's original incarnation. Unfortunately however, sol's explanation didn't provide a complete "understanding" of history, in terms of Einstein's original intent and use of that constant. There's more to 'knowledge' than math alone.

It would be utterly foolish for me to believe that I have the skills to teach sol math, or teach edd math, or teach a lot of folks here about math. Math however is not the 'be-all-end-all" of human knowledge and human understanding. Sometimes a good conceptual understanding is 'better than" understanding the math.

 

[Michael Mozina]

MMs' cognitive disconnect is much, much deeper than that.

You and GM are one trick ponies. You always attack the individual and ignore the actual argument entirely.

You see, tens of thousands of posts, by MM, make it abundantly clear that he has no grasp of what "quantitative" means, with respect to physics.

What's abundantly clear is the fact you lack any grasp of what "qualitative" means. When did "inflation" ever show up in a lab? When did "dark energy" ever accelerate a single atom?

The problem with your theory has nothing to do with math or your qualitative presentation. The glaring problem in your theory is that you literally "made up' invisible friends to stuff into your math formulas.

Do you think nobody else noticed?

 

[Michael Mozina]

Sorry RC, this is basically wrong. You're mixing up force (a vector) and pressure (a scalar) in a way that's not going to go anywhere useful.

Now, do you really think you guys/gals would be as "forgiving" of any mistake in my mathematical or physical explanation of something? Why in the world would I bark math on command in this forum for a bunch of math Parana that are looking to start a feeding frenzy at my expense?

 

[Michael Mozina]

Thank you... exactly where I was going with my posts that MM seems to have neglected of late.

That is exactly what I was going to point out, the limitations on experimental verification of Newton's Law of Gravitation on the 'everyday' scale.

I was hoping that hitting at something he would obviously hold as 'true' might make him question all this "empirical evidence" requirement of his for any theory in physics.

Don't you think philosophically speaking that there should be some hope of someday empirically verifying your theory? If not, now is that different from "faith" in the "supernatural"?

Inflation seems about a hokey as any metaphysical theory because it obviously came from on human being's imagination. It's made even more hokey by the fact it's now 'dead and buried' and is beyond the ability to even effect anything in any physics experiment. That's a little too much like a dead deity theory for my tastes, but you mileage may vary.

Where do I get "dark energy" to play with? Will it ever show up here on Earth or somewhere a human being might actually "control" a recognized source in my human lifetime? If not, isn't belief in such a thing an act of faith on my part?

When does the ability to falsify and/or empirically verify a theory matter in terms of what separates "science" from "religion"? What if I lack belief in the Guthflation cult thing? Will I burn in hell or something?

 

[Michael Mozina]

OK. While it's often written as a separate term in Einstein's equations, there's no need to do so. Just consider the CC to be one of the contributions to the stress-energy tensor (which in my opinion is the only sensible option), and then it's just part of T_\mu \nu with no extra term necessary.

So if the surface of a mass object is charged negative relative to an ambient outer layer of plasma (like a heliosphere), what does that do the stress-energy tensor, and why doesn't that work to explain "expansion/acceleration" of plasma?

 

[Tubbythin]

Sometimes however more than math alone constitutes "knowledge", like in our debate about Einstein's original intent of adding the constant to GR. Virtually everything that sol said about the original formula was technically true, including the fact the formula was unstable in it's original incarnation. Unfortunately however, sol's explanation didn't provide a complete "understanding" of history, in terms of Einstein's original intent and use of that constant. There's more to 'knowledge' than math alone.

Even supposing you were right, it could not possibly be more irrelevant. Sol was discussing the laws of physics, you are discussing human history. Now, which do you think controls the Universe, the laws of physics or human history?

 

[Reality Check]

Sorry RC, this is basically wrong. You're mixing up force (a vector) and pressure (a scalar) in a way that's not going to go anywhere useful.

The "2 non-zero pressures to add to zero pressure" bit was an attempt to cater for MM's attempt to subtract pressures. I really sould not have tried to dumb it down to his level since that makes the explanation physically wrong.
I know that you cannot really do this with pressures. But if I do something too complicated for MM (like vectors ) it will confuse him.


My original explanation had force vectors and MM never understood it.

• A force F pushes on a surface of area A. The pressure p = F/A.
  This is positive (e.g. atmospheric pressure).
• A force F pulls on a surface of area A. The pressure p = -F/A.
  This is negative (e.g. the Casimir effect).

(F is the force vector, F is the magnitude of F)

Why is the force that pulls have a negative magnitude?

Consider if both forces were present and equal, e.g. the Casimir effect in a low pressure environment. Then the forces add up to zero. That means that the magnitude of one force must be the negative of the other force. It is convenient to have a pushing force positive so that the pressure is positive and we do not have to deal with negative signs in everyday situations, e.g. weather maps.

 

[edd]

Well, believe me edd, I appreciate your efforts. There's no one here who's understanding of GR theory I respect more, and no one here who's pure scientific curiosity and demeanor I respect more than you. IMO you and PS typify what I believe a good mixture of scientific curiosity and skepticism is all about. I admire and respect both of you and your efforts in this forum.

For someone in my line of work I have a pretty dismal understanding of GR to be honest. There's certainly others here with a better technical knowledge, just to make that clear.

Absolute or relative pressure?

Absolute

Wait a minute. The concept of relative and absolute pressure is not a "complete canard", it's an important issue, and the crux or our differences.

Fundamentally I don't think it is. I'm totally happy to discuss what the relative pressure on a plate is at any time. But it doesn't change what the pressure on each plate from each side is.

And it's good that you accept the negative pressure in fairly mundane circumstances, as drawing the analogy between the two is what I'm trying to do to demonstrate that the Casimir effect shows negative pressure.

What I do not accept is the notion of "negative pressure" in a "vacuum" that somehow pulls Guth's mass thing apart. Any residual QM energy in the 'vacuum' will attempt to push "into", not "away from" his mass thing.

Now we're really back to the problem of trying to explain that pressure has a gravitational effect as well as the force it applies that is related to the pressure with P=F/A. You never see this gravitational effect in everyday life - the reason is that for a classical gas or something the total kinetic energy of the gas molecules is utterly dwarfed by the mass energy itself - clearly mc^2 is much greater than .5mv^2 until v approaches c (technically, .5mv^2 is an approximation, but it makes the general point of why the gravitational force is basically all down to the mass). And that's on top of it being hard enough to pick out the gravity from gas as it is (the Sun being a notable exception).

Hmm. The plot thickens. Let's try too to look at the springs EVERYWHERE in the chamber, shall we?



Well, this seems like a "one sided", and "relative" (to one side of the plate) explanation. In QM the whole vacuum has has "springs". They come in various shapes and sizes, some large springs, some small springs. At large distances, many sized springs push against everything, all sides of the chamber, all sides of the plates, everything, and pretty much evenly. As the space between the plates decreases, only the smaller springs, the ones with tighter curls can fit between the plates, while the larger springs can no longer fit between the plates. The small springs between the plates become compressed. As the gap between the plates is reduced even further, only the smallest possible springs can fit between the plates. Meanwhile the outside of the plates has ever imaginable sized spring pressing the plates together.

That's fair to say - we're not considering a set of uniform well-machined springs. But its still fair to ask what the net force is on the plate, just as it is fair to ask what the force on a plate from a gas is without considering in detail every particle's specific velocity. When you do that, you still end up having to conclude it's negative pressure.

Also when you say 'Meanwhile the outside of the plates has ever imaginable sized spring pressing the plates together.' you have assumed that these springs are 'in compression' - that they want to push outwards, rather than pull inwards. I chose springs for the analogy as they can, depending on their extension, exert a force in either direction. You've snuck in an incorrect assumption that they exert force only in one particular direction. Similarly when you say 'The small springs between the plates become compressed.' you're mistakenly taking the analogy too far, and assuming that the vacuum really is made up of springs that become compressed and push out to return to their equilibrium. This is also not the case.

My point with the analogy was not to say that the vacuum is made of springs. I was pointing out that in other cases where one might not know if a (absolute) pressure is positive or negative, you can tell by looking at whether energy has been stored or released by the thing exerting that pressure.

There's still a relative/absolute pressure issue going on here. Your "perspective" of pressure if you will is "relative to' the inside of the plate without respect to the pressure on the other surfaces of the plate. It's just like that wing analogy. There's nothing wrong with your perspective as long as you realize it's a 'relative pressure', in this case purely relative to the inside surfaces, and purely relative to the outside "pressure" *if* it were zero, which it can never actually be.

If I want to consider the direction the plate will move in in a given circumstance, I'll use the relative pressure. That doesn't mean I don't understand what the pressure from each side is - just as I can calculate the pressure on the sides of a box of a gas without having to look at whether the box is going to fall apart.

You can put anything you want on the other side of the plate as far as I'm concerned, completely remove external vacuum energy leaving nothing outside at all, fix the plate in place and exert a force on it that way or stick a big spring on it, whatever you like - I will still calculate a negative pressure for the stuff between the plates.

You still have to put springs outside as well as inside the plates edd.

No, really I don't. The way I'm using pressure I can have anything outside the plates you like and I will absolutely get the same result for the pressure inside. I will get a different result for the relative pressure and the net force on the plate.

From another post of yours

When did "inflation" ever show up in a lab? When did "dark energy" ever accelerate a single atom?

As a means of explanation, why would you expect dark energy to accelerate an atom in a lab? Laboratories are very different from the average universe. Most are on planet Earth. We live on a small cosmic inhomogeneity, with densities far higher than the average universe. My point is that the mass of the Earth, the mass of most objects in the laboratory, are much greater than the total amount of dark energy within the entire planet - it's pretty obvious as the amount of dark energy in the planet is about the same amount as you'd find hydrogen in a sphere the size of the Earth out in the deepest voids of space.

It's an unfortunate fact that it isn't easily testable in laboratory conditions - it's drowned out utterly.

Just because something has no observable effect in the lab does not mean it has no observable effect outside it, however.

 

[GeeMack]

Now, do you really think you guys/gals would be as "forgiving" of any mistake in my mathematical or physical explanation of something? Why in the world would I bark math on command in this forum for a bunch of math Parana that are looking to start a feeding frenzy at my expense?

So you haven't ever, in millions of words you've written on the Internet, and throughout tens of thousands of postings, the bulk of which were comprised of special pleading, arguments from incredulity, and arguments from ignorance, you've never ever once tried to support your crackpot conjecture mathematically because you're scared other people might find a mistake in it?

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