Lambda-CDM theory - Woo or not?

[Michael Mozina]

You really don't know, do you? The volume in question is the volume of space between the plates, and it rather obviously changes with separation distance. Yet again, you reveal that you don't understand even basic aspects of what's under discussion.

But the *total* volume and *total physical process* is not related to the volume between the plates to begin with, nor is the "pressure". You wish to ignore the physical process that is actually occurring by ignoring the volume in the rest of the chamber. That is where your mathematical model led you astray to the actual "physics" going on, and why you still "believe" in "negative pressure". The *whole* volume of the *entire chamber* is relevant to this discussion because even the geometry of the chamber in relationship to the plates plays a critical role in which direction the plates move! You can't ignore the actual *physics* of what is occurring inside the chamber, but that is exactly what you are trying to do by ignoring the rest of the volume in the rest of the chamber.

Well, you got one thing right.

More personal insults, how unexpected.........Yawn.

 

[Michael Mozina]

You're absolutely correct, but Michael just doesn't understand how to deal with something in a generalized fashion.

We aren't discussing a "general" scenario, we are discussing the "pressure" of a "vacuum".

Which is why he never understood what I meant by
[latex]$P=-\frac{\partial E}{\partial V}$[/latex]
but instead kept trying to apply the ideal gas law as if it defined pressure.

I understood it well enough to give you an (actually two) alternative definition(s) that works just fine to describe the "pressure" in a "vacuum". You just didn't like that fact that the lower limit of the functions of pressure were zero, not negative infinity.

 

[Reality Check]

I'm still noting that even the best vacuums on Earth and in space have "air pressure" in them. They have QM "pressure" too I suppose if you wish to call a "FORCE" (kinetic energy of photons, neutrinos, etc). At no point does a vacuum contain even "zero" pressure, let alone "negative pressure".

And the physicists know this. And they cater for this.

Where do you guys get off making such wild accusations, particularly after I "praised" the folks that described the Casimir effect on WIKI, right down to the images they used? They obviously knew what they were talking about when they called it a "force" and you ignored it. They obviously know what they were talking about when they described the "force" as it affected *both sides* of *both plates*, and you ignored that too. They aren't stupid.

See above. You are babbling on about an effect (air pressure) that is known and catered for. An implication is that you think that the physicists stupid enough not do not know this.

Alternately you are stupid enough to think that the diagram in Wikipedia includes air pressure. It does not. It has plates, vacuum fluctuations and forces (or pressures).

That leaves unknown forces to be measured. This turns out to be the Casimir effect which is a negative (attractive) net force and so a negative net pressure or is a positive (repulsive) net force and so a positive net pressure. This depends on the materials being used in the experiment.
Notice the word net - this includes the forces and pressures on both sides of the plates. Of course the experiments are most often done with a plate and a sphere.

You may have missed this in high school physics so:
If you have an attractive force and an equally repulsive force then they act in opposite ways, e.g. the attractive force between an electron and a positron is opposite to the repulsive force between an electron an an electron. Thus if one is considered to be "positive" then the other is considered to be "negative". By convention repulsive forces are labeled as positive.
Therefore a surface that has a repulsive force acting on it (e.g. gas molecules bouncing off it) has a positive pressure measured. Try to guess what scientists call the the pressure exerted on a surface by an attractive force.

No, it is NOT! It is an example of *force* being applied to *both sides* of *both plates* where where the force is "greater" on one side than the other. It's all done inside a "positively pressurized" chamber!

I can I do this too !
No: It is negative pressure!

You are still ignoring my really simple general physics question on pressure.
Is it too complex for you? Shall I dumb it down even further?

 

[temporalillusion]

There was lots of radiation, and lots of very fast moving elementary particles (which you might want to call "matter" - it's a matter of taste ). If you were to stick a chunk of, say, iron in there, it would vaporize almost instantaneously into a cloud of very energetic photons, quarks, electrons, gluons, etc.

Ah ok, I had thought that it was purely radiation, that makes more sense to talk about heat then.

And yes, all that energy couples to gravity (gravity acts on all forms of energy, democratically).

I was trying to get MM to acknowledge that for his bomb thought experiment, which he's abandoned now I guess

As for this issue of net zero energy:

...

In a closed universe, the energy is strictly zero, because the "sphere at infinity" actually has zero size, and so there's nowhere for the flux to escape. But closed universes can have plenty of matter and energy in them, can be hot, etc. Ergo, the gravitational contribution to the total energy is negative definite - which is no surprise at all, as the same thing is true in Newtonian gravity.

In a flat or open universe I don't know a good way to define a conserved, non-zero energy (because no matter how big the sphere is there is always energy flowing in or out).

And we don't know if the universe is open or closed.

As usual the real answer is "it depends" and "it's more complicated than that" lol.. thanks!

-----

So MM, you didn't respond to anything but the first part of my post, so I'll post it again so you don't have to scroll back.

If I have an electron and a proton (or whatever you want), and the closer I bring them together, the attractive force between them increases right?

Do you agree with Coulomb's law?

[latex]$$ F=k_e\frac{q_1q_2}{r^2} $$[/latex]

As r approaches zero, what's going to happen to the force? What's the upper limit of that attraction? You can't produce one for the Casimir effect, but you should be able to do so for this since this is your home turf so to speak.

Hypothetically it approaches infinity, do you agree?

How is this any different than the formula for pressure? What do you think happens to the pressure as the distance between the plates goes to zero, if the distance is in the denominator? In an ideal situation with impossibly flat and impossibly parallel and impossibly close plates?

Nah. The folks that wrote the WIKI article and created the images on the Casimir effect got it right. This negative pressure in a vacuum is almost exclusive limited to your group. Most scientists I meet seem to have a better grasp of QM than this crew.

Here again you agree with the wiki article for the Casimir effect.

Let me ask again, for the dozenth time or something, what is the sign for pressure in this forumula?

[latex]$$ \frac{F_c}{A}=-\frac{\hbar c \pi^2}{240a^4} $$[/latex]

If you disagree with the derived formula, at which point does the derivation go wrong in your opinion?

What textbook *besides on related to Lambda-CDM theory* claims that a vacuum contains "negative pressure".

Well the wiki article you say is written by people that got it right claims it. What's the sign on the formula above?

Actually, in the case of the Casimir article, the WIKI presentation was correct. Only your crew seems to be incapable of distinguishing between a QM "force" and pressure and not being able to recognize that there is *force* on both sides of the plates.

And according to the crew that wrote the wiki article, what's the sign on the formula above?

 

[Reality Check]

We aren't discussing a "general" scenario, we are discussing the "pressure" of a "vacuum".

I understood it well enough to give you an (actually two) alternative definition(s) that works just fine to describe the "pressure" in a "vacuum". You just didn't like that fact that the lower limit of the functions of pressure were zero, not negative infinity.

We are discussing the general scenerio. This happens to include the pressure of a vacuum from QM fluctuations.

You seem to be obsessed with discussing the air pressure of the gas inside a vacuum chamber. This is not vacuum pressure.
Air pressure
Vacuum pressure.
Notice the difference?

Could you give these 2 alternative definitions of pressure that work in all situations (like the one Ziggurat gave you)?

Citations to the textbooks that use these defintions as general definitions of pressure would be good.

If one is the ideal gas law then you are wrong since that only applied to an ideal gas. That leaves the other.

 

[Ziggurat]

We aren't discussing a "general" scenario, we are discussing the "pressure" of a "vacuum".

Before we can discuss it meaningfully, we need a definition of pressure. And definitions are by nature general, or else they aren't definitions.

I understood it well enough to give you an (actually two) alternative definition(s) that works just fine to describe the "pressure" in a "vacuum".

Once again: the definition of pressure has nothing to do with whether or not it's in a vacuum. But evidently, not only do you not understand pressure, you don't understand "definition".

But let's see if you understand the definition I gave you. Let's say I have three black boxes, with unknown contents inside. The volume of the boxes can be adjusted, and by fiddling with the volume we can determine how the energy of the contents varies with volume. These are the energy functions for each box (with a, b and c being some constants):

#1: E = aV
#2: E = -bV
#3: E = c/V

According to the definition of pressure that I gave you, which of those boxes has positive pressure inside, and which has negative pressure? If you actually understood the definition of pressure I gave, this should be easy to figure out.

 

[DeiRenDopa]

What's the definition of "definition"?

Haven't we been here before?

 

[Ziggurat]

What's the definition of "definition"?

Haven't we been here before?

Multiple times.

 

[edd]

Ah, but nature is not "agnostic" when it comes to the operation of it's low level physical mechanisms. GR is just a mathematical model that may or may not accurately describe the physical functions of the universe. Perhaps GR theory will one day be replaced with a quantum description of gravity. The physical processes that drive gravity will determine whether or not GR is ultimately replaced with a new mathematical model. There is a "physical reality" that these mathematical models attempt to accurately model.

OK, if you want to say "perhaps dark energy doesn't really exist" that's fine, but you seem to want to present a physical argument why it cannot exist, and you have not yet presented one.

I'm not sure how to even treat "dark energy" since it seems to be nothing more than a "new fancy label" to describe "acceleration". I don't see why "acceleration" needs a "fancy new placeholder label' to begin with. As it relates however to "negative pressure", nothing like that is possible in a vacuum due to the existing kinetic energy inside the vacuum.

It provides a starting point at least for testing physical theories and providing questions and means for designing experiments to learn more.

 

[Tubbythin]

You do not. You have "subjective personal faith" in the notion based on a little redshift.

No.

Only if we *assume* inflation has some effect on nature.

But we don't need to assume. We can compare prediction with observation.

All we know is that we are here and the universe is as we observe it to be. Even on a gamma ray spectrum the universe can be observed to be relatively uniformly distributed. That's all we really "know".

Well no. We have a theory of gravity from which we can make testable predictions and these predictions have always been met. We have copious amounts of astronomical and, more importantly, cosmological data.

 

[Tubbythin]

I understood it well enough to give you an (actually two) alternative definition(s) that works just fine to describe the "pressure" in a "vacuum". You just didn't like that fact that the lower limit of the functions of pressure were zero, not negative infinity.

You're not still thinking that your application of the ideal gas equation was either:
a) a definition
and/or
b) a sensible equation for describing vacuum pressure
are you?
I couldn't comprehend the level of complete failure of comprehension of anyone who believed either a or b.

 

[Michael Mozina]

OK, if you want to say "perhaps dark energy doesn't really exist" that's fine, but you seem to want to present a physical argument why it cannot exist, and you have not yet presented one.

That's not my job. I'm not required to demonstrate a negative. In fact it's impossible to do so. You have yet to present any evidence that dark energy exists or has any effect on nature. A pattern of acceleration in distant objects in not evidence that "dark energy did it.".

It provides a starting point at least for testing physical theories and providing questions and means for designing experiments to learn more.

Where does "dark energy" come from so I can "experiment" with it?

 

[Michael Mozina]

Ah ok, I had thought that it was purely radiation, that makes more sense to talk about heat then.

Well, if you're going to talk "heat", you need to know what *holds* that heat, and note that you began with "net positive' amounts of energy in that "heat".

How does "stuff" hold heat? What exactly is 'hot" prior to the formation of subatomic particles? In the case of the atomic realm we have particles that vibrate and bounce around and create pressure. At the subatomic level we observe heat being emitted in terms of photons. If there are actual particles and real photons being emitted from these real subatomic particles then there is real mass too, and real gravitational attraction between particles of mass. Why doesn't this heat thingy implode from the gravitational attraction of these real subatomic particles?

I was trying to get MM to acknowledge that for his bomb thought experiment, which he's abandoned now I guess

I actually think that the lump of matter and antimatter analogy is a better analogy at this point. There is energy contained in the matter and the antimatter than can be released by touching them together. Mass itself is a from of energy. There is no way that "gravity' is going to take away or remove the energy in the explosion if we slam them together. Even when the pieces that are left are move through space they contain energy that can be released by further contact with it's antimatter/matter counterpart. The universe is a "net positive" energy state and it has been that way since it started with all that "heat" that sol is talking about. It was never a "net zero" energy state, it always had a "net positive amount of heat".

 

[edd]

That's not my job. I'm not required to demonstrate a negative. In fact it's impossible to do so. You have yet to present any evidence that dark energy exists or has any effect on nature. A pattern of acceleration in distant objects in not evidence that "dark energy did it.".

Previously you have said:

How can anyone here still be defending the idea that a vacuum can have negative pressure? It's physically *impossible* for that to happen.

By doing so you put it upon yourself to prove that negative. You have said many things like that throughout this thread.

In contrast, I have said

The majority of my comments are aimed at dealing with what I see as unfair and unfounded criticism against certain theories, not in pushing those theories as being any more favoured than they already are.

I do not push for the idea of dark energy as definitely being the truth. I merely support it as currently the strongest explanation given the evidence available. The evidence for dark energy is widely available (and has been explained here before) but I do not contend that dark energy is the only possible explanation for the evidence we have. I do contend that it is a perfectly respectable, and indeed amongst the best, explanation we have at the moment.

You however, have been stating categorically that dark energy does not exist, stating that it is impossible for it to exist, while not providing a good argument for either.

If you keep stating the negative that it does not exist then it is your job to prove that, because you are implying that it is possible to prove this negative.

Or do you retract your previous statements that dark energy is physically impossible? If you do so, I will have substantially fewer grounds for complaint.

 

[temporalillusion]

Well, if you're going to talk "heat", you need to know what *holds* that heat, and note that you began with "net positive' amounts of energy in that "heat".

Sol explained what holds the heat. And you don't need net positive amounts of energy in that heat, you need positive energy in the stuff that's holding the heat.

Why doesn't this heat thingy implode from the gravitational attraction of these real subatomic particles?

Why don't you implode from the gravitational attraction of your real subatomic particles?

I actually think that the lump of matter and antimatter analogy is a better analogy at this point. There is energy contained in the matter and the antimatter than can be released by touching them together. Mass itself is a from of energy. There is no way that "gravity' is going to take away or remove the energy in the explosion if we slam them together.

I never claimed it would. If that's what you think I've been saying, then you need to learn the definition of the word "net".

Even when the pieces that are left are move through space they contain energy that can be released by further contact with it's antimatter/matter counterpart. The universe is a "net positive" energy state and it has been that way since it started with all that "heat" that sol is talking about. It was never a "net zero" energy state, it always had a "net positive amount of heat".

What does "net" mean?

May I ask a simple question? Why did you ignore the rest of my post?

 

[Michael Mozina]

Sol explained what holds the heat.

Since I'm still waiting for his response to my last post, about all I can say is his "answer" leads to some other very important unanswered questions. If we begin with "heat", we begin with a "net positive' energy state. If we have elementary particles, we have gravity which would work to make the whole thing "implode", not "inflate".

And you don't need net positive amounts of energy in that heat, you need positive energy in the stuff that's holding the heat.

Er, you need "positive energy" in something from the very start. There was never a zero energy state. The "heat" is itself a form of energy. You're beginning *with* positive quantities of energy in the form of "heat"!

Why don't you implode from the gravitational attraction of your real subatomic particles?

Well, for one thing I don't contain all the mass/energy of a whole universe.

I never claimed it would. If that's what you think I've been saying, then you need to learn the definition of the word "net".

The only "net" here is a "positive energy state". Heat is a net positive amount of energy. Energy can "change forms", but it cannot be created or destroyed. It's a "net energy conservation" event. E=MC^2 and E has *always* existed.

What does "net" mean?

I guess that depends on whether you ask a fisherman, a fan of tennis, or a statistician. There is no "net" anything about the BB event except a "net conservation of preexisting energy'.

May I ask a simple question? Why did you ignore the rest of my post?

I was out of time and rather hungry. There's a lot going on my life, and I figure you and I need to focus on one aspect at a time.

The *HEAT* you keep describing *is a form of energy*. Guth's theory *begins with energy* in the form of "heat". He describes a "supercooling" process, where this "heat" it ultimately transformed into matter. It's a net conservation of energy event. It's a net positive energy event. It's a net change of forms of energy, but there is nothing "zero energy" about it.

 

[Michael Mozina]

Previously you have said:

By doing so you put it upon yourself to prove that negative. You have said many things like that throughout this thread.

It is physically impossible for "dark energy" to do anything to anything because it does not exist. It is likewise physically impossible for invisible unicorns to have any effect on anything for exactly the same reason. Nothing like that exists in nature or has any effect on nature. If you believe you observe "acceleration", just call it "acceleration". Dark energy does not exist so it cannot be the cause of that acceleration. If you believe otherwise, it is your job to demonstrate that dark energy exists and can cause something to accelerate in a controlled experiment. If you cannot do that, they you are engaging in religion, not science.

In contrast, I have said

I do not push for the idea of dark energy as definitely being the truth. I merely support it as currently the strongest explanation given the evidence available.

All you have is evidence of "acceleration". You have no evidence that "dark energy did it".

The evidence for dark energy is widely available (and has been explained here before)

Even if I accept the evidence of acceleration, that is not evidence that dark energy was involved in that acceleration.

but I do not contend that dark energy is the only possible explanation for the evidence we have. I do contend that it is a perfectly respectable, and indeed amongst the best, explanation we have at the moment.

Physically define "best" in some way that is objectively qualified in some tangible way. At "best" you have evidence of accelerated expansion. In no way do you have any evidence that "dark energy" is the "cause" of that process. You are again simply "assuming" something "new" exists in nature when nothing "new" is required to explain a simple observation of acceleration of plasma.

You however, have been stating categorically that dark energy does not exist,

It does not exist. It has no effect on me, or on anything in a controlled experiment. Whatever the actual "cause" of acceleration, it is not related to invisible gremlins, dark evil energy, or Zeus.

stating that it is impossible for it to exist, while not providing a good argument for either.

Let's try it this way then: It is *impossible* to establish any cause/effect relationship between and type of 'acceleration', of even one single particle of plasma, and "dark energy" in a controlled experiment. Does that make you happier?

 

[Ziggurat]

E=MC^2

... is from special relativity. And special relativity explicitly ignores gravity.

He describes a "supercooling" process, where this "heat" it ultimately transformed into matter.

Well, no. When space expands, electromagnetic radiation loses energy without creating matter. Guess where that energy goes (hint: I referenced the answer in this post).

 

[Michael Mozina]

And the physicists know this. And they cater for this.

Sure, but evidently you don't read their work or understand it very well. The quantum *force* that they write about effects *both* sides of *both* plates!

Hoy. You folks are a really stubborn lot. Even with graphic evidence that blows away your beliefs, you ignore the little blue arrows entirely.

See above. You are babbling on about an effect (air pressure) that is known and catered for. An implication is that you think that the physicists stupid enough not do not know this.

I don't know who you figure I think is stupid here except those claiming there is negative pressure in a vacuum and the BB was a "net zero" energy event. The guys/gals that wrote the WIKI article on the Casimir effect got it right, so I have no beef with *those* physicists. Are you even a physicist by trade?

Alternately you are stupid enough to think that the diagram in Wikipedia includes air pressure. It does not. It has plates, vacuum fluctuations and forces (or pressures).

Another strawman. I have *carefully* explained this now a number of times. Those blue arrows are the "force" carried by the EM carrier particles in the vacuum, and they "push" on all sides of all the plates, just like molecules might do. Your need to use the word "stupid" in every sentence is getting boring by the way.

That leaves unknown forces to be measured. This turns out to be the Casimir effect which is a negative (attractive)

Yes or no, does that "attractiveness" depend on "geometry" in any way? If so, why and how does that "attractiveness" turn into "repulsiveness"?

 

[temporalillusion]

Well, for one thing I don't contain all the mass/energy of a whole universe.

Well neither do black holes yet they do collapse in on themselves. I don't think the amount of matter/energy is as important as the density and the other forces at work.

Plus I'm not sure that the amount of matter and positive energy running around pre-inflation was the same as is now, but that's just a gut feeling, someone want to comment on that from a current cosmology point of view? Has all the matter/energy currently existing in the universe always existed up to the point of singularity anyway (or is the question even meaningful)?

The only "net" here is a "positive energy state". Heat is a net positive amount of energy. Energy can "change forms", but it cannot be created or destroyed. It's a "net energy conservation" event. E=MC^2 and E has *always* existed.

You said that "There is no way that "gravity' is going to take away or remove the energy in the explosion if we slam them together.". That's not what "net" means, that's an actual interaction.

I guess that depends on whether you ask a fisherman, a fan of tennis, or a statistician. There is no "net" anything about the BB event except a "net conservation of preexisting energy'.

You didn't answer the question.

Net means this..

If I have 1 unit of energy (either tied up in matter, in pressure, momentum, whatever) somewhere, and I have -1 unit of energy in a gravitational field, the net energy is zero. Both things happily exist, the negative gravitational energy doesn't "remove" the energy of the other thing. But the net of the whole system is zero.

So if you add up all the positive energy for all the matter and energy, and then all the negative energy from gravity, you end up with a zero at the end of the spreadsheet.