Lambda-CDM theory - Woo or not?

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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.
 
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.
 
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 :D!
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?
 
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?
 
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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.
 
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.
 
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.
 
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.
 
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.
 
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?
 
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".
 
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.
 
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?
 
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.
 
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? :)
 

... 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).
 
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!

300px-Casimir_plates.svg.png


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"?
 
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.
 
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!
You need to learn to read: I was consistent in stating NET force and NET pressure. Net = the result of the force and pressure from both sides.

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

Hoy. You folks are a really stubborn lot. Even with graphic evidence that blows away your beliefs, you ignore the little blue arrows entirely.
No one has ignored the little blue arrows or for that matter the wavy green lines (vacuum fluctuations).
The little blue arrows show exactly what every other poster has stated: vacuum fluctuations cause an unqual force on the plates and so a net force is exerted on the plates. When this net force is repulsive (pushes the plates apart), the convention is that it is positive. When this net force is attractive (pulls the plates together), the convention is that it is the opposite of positive. This is known as negative.

It does not blow our beliefs away. It is that image that illustrates the derivation that the pressure is actually negative. Since you are having trouble with reading and comprehension here is the derived formula for pressure (force per area) from the rest of the Wikipeda page that you are ignoring:
The Casimir force per unit area Fc / A for idealized, perfectly conducting plates with vacuum between them is
aaed68a46efadd36a85b5265890fe2a6.png
where
9dfd055ef1683b053f1b5bf9ed6dbbb4.png
(hbar, ħ) is the reduced Planck constant, c is the speed of light, a is the distance between the two plates. WP

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?
I better make it explicit then: you are the one being stupid (or just unable to read). See above for the negative pressure that the physicists that you have no beef with quote from Casimir's work.

Which of the quantities on the right hand side is negative so that F/A is positive.


Your choices are:
  • hbar (reduced Planck constant)
  • c (speed of light)
  • pi (the ratio of any circle's circumference to its diameter)
  • 240 (a number)
  • a (the distance between the 2 plates)
  • a to the fourth power
What is your answer?

...snip...
Yes or no, does that "attractiveness" depend on "geometry" in any way? If so, why and how does that "attractiveness" turn into "repulsiveness"?
No. It depends on the geometry and the material involved. Repulsive Casimir forces are most commonly found when the vacuum is replaced by a fluid. This means that measuring it is much harder than the attractive Casimir effect and scientists are just starting to get results, e.g. Measurements of the Casimir-Lifshitz force in fluids: the effect of electrostatic forces and Debye screening (13 Aug 2008)).
 
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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.
That just sends us round in circles. You're simply stating that dark energy doesn't exist with no evidence to back that up.

Nothing like that exists in nature or has any effect on nature. If you believe you observe "acceleration", just call it "acceleration".
The simple problem with this is that "acceleration" doesn't give you a physical mechanism for it. Dark energy does - gravity. It also gives you a range of models for that acceleration expressing how it changes over time and how it affects other fundamental properties of the universe such as its geometry, how it affects the growth of structure within the universe and so on. By suggesting that it is dark energy behind the acceleration we make it easier to prove that it isn't dark energy thus giving us a stronger scientific theory until such time, if ever, that it is proven incorrect. It provides predictions about the results of future observations. Merely stating the fact of current observations does not do this.

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.
It is a fundamental problem with astronomy and especially cosmology that controlled experiments cannot be conducted upon universes or indeed on scales even vaguely approaching the cosmological. Observational sciences where controlled experiments cannot be performed are still sciences, but naturally are more constrained in their approach. They're patently not religion - they're founded deeply upon evidence even if the evidence does not come from "controlled experiment".

All you haveis evidence of "acceleration". You have no evidence that "dark energy did it".
Actually that is evidence for dark energy. Not conclusive evidence, but it is evidence nonetheless. Evidence for a hypothesis can be remarkably weak while still constituting evidence - http://en.wikipedia.org/wiki/Raven_paradox . The evidence for dark energy is vastly stronger than the evidence for black ravens that a green apple constitutes, but the fundamental point presented by that is that evidence for an idea need not be entirely conclusive.
To give a more relevant example, the fact that I am held firmly in my chair and that the moon is orbiting above constitutes evidence for Newton's theory of gravity. It's clearly not conclusive evidence that that theory is correct, since the theory is actually wrong.
Likewise current cosmological observations provide evidence to support the idea of dark energy, but it may turn out to be incorrect despite this.

You are again simply "assuming" something "new" exists in nature when nothing "new" is required to explain a simple observation of acceleration of plasma.
Please go ahead and provide a mathematical model of how the plasma accelerates the universe in a way that can be competitively tested against other cosmological models. Unless you do you have not explained observations by use of plasma.

If you wish to state that things do not exist unless they are amenable to controlled experiment then fine. I would however expect most people would see that it's crazy to limit physical reality to what is accessible in experiment by human technology.
 
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)?

Take the example of a closed universe for simplicity. Then total energy is exactly conserved and always equal to zero. As you go back in time, matter and radiation get hotter and denser - so the energy in them increases. At the same time the gravitational potential energy gets more and more negative. This happens in much the same way as would occur for a cloud of gas collapsing under its own gravitational pull (or just two particles falling together, to make it even simpler). The collapse accelerates as it continues, leading to a singularity a finite time in the past.

Why didn't the early universe collapse into a black hole? The premise of the question is nonsensical. A black hole is by definition a localized object, something surrounded by space. So the universe as a whole cannot become a black hole. The closest analog is that it universe becomes singular everywhere, which is precisely what happened at the big bang. So very roughly speaking the evolution of the universe is analogous to the time-reverse of the collapse of matter into a black hole.
 
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The closest analog is that it universe becomes singular everywhere, which is precisely what happened at the big bang. So very roughly speaking the evolution of the universe is analogous to the time-reverse of the collapse of matter into a black hole.
(my bold)

Something of a derail here, but shouldn't that be anti-matter if I remember my physics correctly?

Not that it matters in this informal treatment, just wanted to check if I had it right.
 
Something of a derail here, but shouldn't that be anti-matter if I remember my physics correctly?

The symmetry of the laws of physics is not really T (time reversal), it's CPT (time reversal and charge conjugation and parity flip). That does turn matter into anti-matter - so you're right, you remember correctly.

But matter and anti-matter interact in precisely the same way gravitationally. Moreover, T is an almost exact symmetry - CP is violated at such a tiny level that it wasn't detected until quite recently. And anyway our universe contains both matter and anti-matter - just a lot more matter.
 
But matter and anti-matter interact in precisely the same way gravitationally.
I was about to post much the same thing :) I will just add that this hasn't actually been measured experimentally yet (at least not that I'm aware of or to comfortably high standards). In a Dirac-Milne universe antimatter acts like it has the opposite gravitational 'sign'. http://arxiv.org/abs/0903.2446 for a recent paper on it. Also http://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter

However, if the universe did work that way I think most physicists would be really rather surprised.
 
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I was about to post much the same thing :) I will just add that this hasn't actually been measured experimentally yet (at least not that I'm aware of or to comfortably high standards). In a Dirac-Milne universe antimatter acts like it has the opposite gravitational 'sign'. http://arxiv.org/abs/0903.2446 for a recent paper on it. Also http://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter

However, if the universe did work that way I think most physicists would be really rather surprised.

Indeed.

Let me make two comments: first, in order for anti-matter to have the opposite gravitational sign, much of what we know about physics would have to be wrong. Gravity couples universally to all forms of energy - that's the equivalence principle. Granted that hasn't been tested for anti-matter (since it's very hard to make enough anti-matter to measure its gravitational interactions), but it has been tested for just about all the other forms of energy we have around, and it works perfectly. And anti-matter certainly has positive energy - that at least we know beyond any doubt from particle accelerator data.

Second, the justifications they give in the introduction for considering this are very weak. In particular, this claim that Kerr-Newman has negative mass on the opposite side of the Kruskal extension is, in a word, wrong. It's true that the sign of all charges flips when one passes through; but the local physics is totally unaffected by that (because everything changes sign there, and the two regions are completely disconnected - they're on opposite "sides" on an event horizon). It's actually closely related to the net zero energy thing we've been discussing - precisely the same thing happens in many geometries, and it's just a reflection the symmetries of GR.
 
Quite. I nearly used the phrase "utterly gobsmacked" rather than "really rather surprised".
 
Michael Mozina said:
DeiRenDopa said:
If I may, these need some editing, in order for them to be reasonably free of ambiguity and also phased more appropriately for this section of the JREF Forum.

A) Are there experimental results consistent with "negative pressure in a vacuum"?
The answer is no! The Casimir effect has *nothing* whatsoever to do with "negative pressure in a vacuum". There is a Casimir QM "force" that is related to the EM field, that pushes on *both* sides of the plates!

http://upload.wikimedia.org/wikipedi...plates.svg.png

B) Are there observations and experimental results consistent with "the observable universe has a net energy of zero"?
No.

The answer to both questions would be yes, IMHO.
Start with the first one then. What experimental results suggest that a vacuum can contain negative pressure? Be specific.
Not so fast!

You omitted the rest of my post; here it is again (in bold):
If I may, these need some editing, in order for them to be reasonably free of ambiguity and also phased more appropriately for this section of the JREF Forum.

A) Are there experimental results consistent with "negative pressure in a vacuum"?

B) Are there observations and experimental results consistent with "the observable universe has a net energy of zero"?

The answer to both questions would be yes, IMHO.

It is important to note several features of my edited version:

1) the statements are objectively, and independently, verifiable (it matters not one jot what MM, DRD, si, ... believes, supports, thinks, feels, ...)

2) the parts in quotation marks are only unambiguous wrt standard, contemporary, textbook definitions of the key terms "pressure", "vacuum", and "energy" (change the definition of any term and the statements will be different, and - very likely - ambiguous)

3) both statements assume full acceptance of the aspects of theories in modern physics consistent with every facet of every relevant observation and experiment (so, for example, take QED off the table and every modern experiment and astronomical observation needs to be re-analysed).

The last one (3) is a biggie, and probably has wide ramifications for much of what you have posted in this thread MM.

(there's also an error in your transcription; "Are there experimental results consistent with" is what I said; do you understand the difference, cf what you wrote?)

Here's what I'll do: this thread already contains many posts on this topic, including direct answers provided by others. More importantly, this thread also contains definitions of the key terms ("negative pressure" and "vacuum" in this case), definitions that are just what my point 2) is about. I'll go dig up the relevant posts, and copy them That way you'll see exactly how you missed the key things at least once before.
Well, it turned to be not necessary at all to do that ... many of the posts since I posted this dealt with the topic at least as well as older posts in this thread did.

The wiki article (unless it's been edited in the meantime) quite nicely illustrates the point I was making in 2) ("the parts in quotation marks are only unambiguous wrt standard, contemporary, textbook definitions of the key terms "pressure", "vacuum", and "energy" (change the definition of any term and the statements will be different, and - very likely - ambiguous)") - the experimental results are consistent with "negative pressure in a vacuum", provided you use the standard, contemporary, textbook definitions of the key terms "pressure", and "vacuum".

As seems quite clear, you (MM) choose to use a non-standard definition.

So that one is now closed, right?

On to B) then?
 
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Well, it turned to be not necessary at all to do that ... many of the posts since I posted this dealt with the topic at least as well as older posts in this thread did.

The wiki article (unless it's been edited in the meantime) quite nicely illustrates the point I was making in 2) ("the parts in quotation marks are only unambiguous wrt standard, contemporary, textbook definitions of the key terms "pressure", "vacuum", and "energy" (change the definition of any term and the statements will be different, and - very likely - ambiguous)") - the experimental results are consistent with "negative pressure in a vacuum", provided you use the standard, contemporary, textbook definitions of the key terms "pressure", and "vacuum".

As seems quite clear, you (MM) choose to use a non-standard definition.

That is absolutely false. The WIKI article clearly describes a *FORCE* (the carrier particles of the EM field) that pushes against *both* sides of *both* plates. Now of course you could attempt to *oversimplify* the physics of what is actually occurring in the chamber and *only* consider the volume *between* the plates and come up with some rationale for putting a minus sign in there. That does not however justify the idea of "negative pressure in a vacuum". There is no such physical thing going on between those two plates. I did *not* use a "non-standard" definition, you did. The blue arrows in the WIKI image tell the entire story, whereas an *oversimplified* mathematical representation of this process does not. Like I've said all along, you folks understand math, but almost *nothing whatsoever* about the physical processes that your math attempts to describe, particularly at the subatomic level.

All that is occurring in the chamber is 'positive pressure' on *all* sides of *all* plates. An oversimplified math formula related to only the volume between the plates will *not* accurately describe the *pressure* in the chamber, or on the outside of the plates.

So that one is now closed, right?

Not unless you're ready to admit you're wrong and admit that the authors of the WIKI article got it right when they described this as a "force" that pushes on all sides of the plates.

On to B) then?

Sure. What is 'heat' if not "positive net energy"?
 
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"Known forces of nature"

Here's an idea, wrt MM's "known forces of nature".

Start with gravity, which is, per his own statements, one such.

IIRC, MM proposed a very simple test which demonstrates that gravity, as a force of nature, exists*; something like this: hold your Tesco plasma ball in one hand, hand facing down; with your other hand underneath it, palm up, let go of the ball ... the ball will drop into your (lower) hand; ergo, gravity exists.

As was pointed out, and as is clear anyway, all this test shows is that the plasma ball falls when released from one's hand; to call that 'gravity' is rather underwhelming.

However, we can proceed empirically - being very careful to define just what we mean by this word - and do lots of tests with lots of different objects, in lots of different places, at lots of different times.

We will find - empirically - that there are plenty of cases where objects do not drop, or fall, when released; for example, a leaf on a windy day, a piece of wood released under water. And we need to confront the problem of induction too.

By being careful, and using induction, we can gradually build more and more powerful summaries of the results of hundreds, thousands, millions, ... of tests, and in the best of these summaries the word 'gravity' will be used, as will the word 'nature'.

In that sense the word 'gravity' may be said to have great explanatory (and predictive) power.

In parallel, and to some extent overlapping, we may develop other summaries of empirical tests (of 'nature') which include another word with great explanatory (and predictive) power, 'force'.

Historically, with some anachronisms and a bit of revisionism, this gets us up to somewhere in the 1500s, maybe a bit earlier, maybe a bit later.

Now we add a true revolution, which I shall term the quantitative revolution ... we can move on from nice word summaries to adding first numbers and then equations, and 'gravity as a force of nature' becomes something whose explanatory and predictive powers expand enormously ... but only if the equations and numbers are understood! We are now in the time of Galileo (more or less).

At that time the heavens and Earth were separate - nature consisted of two almost totally independent parts, each with its own 'forces'; how the planets moved across the sky, for example, had nothing to do with how cannon balls (and feathers) fell when let go.

Then, in the myth, an apple fell on Newton's head while he was gazing at the Moon (it was daytime) ... and nature became unified, and the universal law of gravitation was published.

It was quickly tested, by 'curve fitting' - applying math to points in the sky** - and found to work.

And a century or so later - well after Newton had died - a key part of Newton's law was tested in the lab.

So what does all this have to do with MM's ideas? A great deal actually.

First, 'known forces of nature' are so known via equations and numbers only; if you work at the 'qualitative' level, you cannot have 'known forces of nature'.

Second, a century (or more) may well pass between the first publication of the equations and numbers describing a 'known force of nature' and its testing in the lab.

Third, the application of math to points on the sky can lead to acceptance of a new 'force of nature'.

And so on.

Now we know, from a great many of MM's posts, that he rejects all three of the above points, especially the third one. This alone makes his approach to science very different than that of scientists - or at least physicists - over the past four+ centuries ... and it means that the discussion we should be having is not about Birkeland, the solar wind, inflation, Einstein's EFE, negative pressure, etc; rather it should be about what constitutes science (or at least physics).

If we were to have such a discussion, I think we'd find that a key aspect of MM's approach is an unstated, and possibly unrecognised, misunderstanding of equations and numbers; in short, a world where the quantitative revolution didn't happen.

* I think I've got it right; if not, would someone please point me to his post(s) which say otherwise?
** That's not exactly what MM said, in another context, but it's close, I think.
 
That is absolutely false. The WIKI article clearly describes a *FORCE*

Which is proportional to the area. And if you divide out the area to find that constant of proportionality, what do you get? Why, you get a pressure! Who'da thunk?

Well, anyone who knows the definition of pressure. But you've had problems with that step.

I did *not* use a "non-standard" definition

True: you've never used any definition.

Sure. What is 'heat' if not "positive net energy"?

Well, heat isn't "net energy". Net energy is the sum of all forms of energy, and heat energy isn't the only form. There's gravity too. So even if you want to (wrongly) insist that gravitational energy is positive, heat energy is still not "positive net energy" because it's not net energy at all.

Epic fail.
 
Now we know, from a great many of MM's posts, that he rejects all three of the above points, especially the third one. This alone makes his approach to science very different than that of scientists - or at least physicists - over the past four+ centuries ... and it means that the discussion we should be having is not about Birkeland, the solar wind, inflation, Einstein's EFE, negative pressure, etc; rather it should be about what constitutes science (or at least physics).

Indeed. But such a discussion wouldn't be necessary with anyone other than MM, and with him it would be excruciatingly tedious.

If we were to have such a discussion, I think we'd find that a key aspect of MM's approach is an unstated, and possibly unrecognised, misunderstanding of equations and numbers; in short, a world where the quantitative revolution didn't happen.

One relatively interesting question related to that is why math works so well (whether being long since settled in everyone's mind but MM's). I think the answer is that math is science in the sense that it is discovered rather than invented. That is, it might appear that we invented math - we made up some arbitrary rules and played with them. But if that were the case one wouldn't expect it to work as a description of physics any better than English words do. Instead, we are capable of making incredibly precise predictions and checking them.

How can that be? Only if math is simply a symbolic expression of a deep set of truth about the world - that it operates according to the rules of logic.
 
That is absolutely false. The WIKI article clearly describes a *FORCE* (the carrier particles of the EM field) that pushes against *both* sides of *both* plates. Now of course you could attempt to *oversimplify* the physics of what is actually occurring in the chamber and *only* consider the volume *between* the plates and come up with some rationale for putting a minus sign in there. That does not however justify the idea of "negative pressure in a vacuum". There is no such physical thing going on between those two plates. I did *not* use a "non-standard" definition, you did. The blue arrows in the WIKI image tell the entire story, whereas an *oversimplified* mathematical representation of this process does not. Like I've said all along, you folks understand math, but almost *nothing whatsoever* about the physical processes that your math attempts to describe, particularly at the subatomic level.

All that is occurring in the chamber is 'positive pressure' on *all* sides of *all* plates. An oversimplified math formula related to only the volume between the plates will *not* accurately describe the *pressure* in the chamber, or on the outside of the plates.



Not unless you're ready to admit you're wrong and admit that the authors of the WIKI article got it right when they described this as a "force" that pushes on all sides of the plates.

[...]
Huh?

Are we reading the same wiki article?

Did you miss RC's post (#1861)?

In a way it's kinda ironic that I was writing my last post as you were posting this one of yours; rather good empirical, objective, independently verifiable evidence of "a world where the quantitative revolution didn't happen", don't you think?
 
Indeed. But such a discussion wouldn't be necessary with anyone other than MM, and with him it would be excruciatingly tedious.
I think you're right about the particular, but a general discussion might not be so ... I suspect that a great deal of the discussion on 'alternatives' would be much shorter if we could get, much more quickly, to unrecognised mismatches wrt approaches to science (or at least physics and closely related branches of science).

One relatively interesting question related to that is why math works so well (whether being long since settled in everyone's mind but MM's). I think the answer is that math is science in the sense that it is discovered rather than invented. That is, it might appear that we invented math - we made up some arbitrary rules and played with them. But if that were the case one wouldn't expect it to work as a description of physics any better than English words do. Instead, we are capable of making incredibly precise predictions and checking them.

How can that be? Only if math is simply a symbolic expression of a deep set of truth about the world - that it operates according to the rules of logic.

Have you heard of "The Math Instinct", by Keith Devlin? It's a popular level book that makes a related point.

Another way to look at this: by their evolutionary success, animals with largish brains develop 'math' capabilities, because such capabilities enable them to survive and reproduce more efficiently; in this sense, 'math' is a general characteristic of the world in which such animals live (and reproduce, or die).
 
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?

Why do you base your comprehension on a single illustration?

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?
 
You need to learn to read: I was consistent in stating NET force and NET pressure. Net = the result of the force and pressure from both sides.

Gah! I don't know what to do with you. You make a statement like this, and then further down in your post you used a formula that intentionally *oversimplifies* the process and pays *no attention whatsoever* to the chamber *geometry*, or the pressure on the outside of the plates. What the heck am I supposed to do with you?

No one has ignored the little blue arrows or for that matter the wavy green lines (vacuum fluctuations).

Yes, you are still ignoring them in your math formula. Your math formula of personal choice explicitly does *not* (not, not, not!) pay attention to the "pressure" on the outside of the plates! It explicitly *oversimplifies* the physical process!
 
Take the example of a closed universe for simplicity. Then total energy is exactly conserved and always equal to zero. As you go back in time, matter and radiation get hotter and denser - so the energy in them increases. At the same time the gravitational potential energy gets more and more negative. This happens in much the same way as would occur for a cloud of gas collapsing under its own gravitational pull (or just two particles falling together, to make it even simpler). The collapse accelerates as it continues, leading to a singularity a finite time in the past.

Makes sense thanks.

When MM says something like "There is no way that "gravity' is going to take away or remove the energy in the explosion if we slam them together.", or waaay back when MM said that gravity isn't going to take away the heat of the sun, I don't think he understands what is meant by "net".
 
Gah! I don't know what to do with you. You make a statement like this, and then further down in your post you used a formula that intentionally *oversimplifies* the process and pays *no attention whatsoever* to the chamber *geometry*, or the pressure on the outside of the plates. What the heck am I supposed to do with you?

The geometry of the chamber does not matter, the effect is between the two plates. The pressure on the outside of the plates is the same everywhere in the universe. (ETA Well maybe not everywhere, not sure if a gravity well would have an impact, everywhere that's flat then)

Yes, you are still ignoring them in your math formula. Your math formula of personal choice explicitly does *not* (not, not, not!) pay attention to the "pressure" on the outside of the plates! It explicitly *oversimplifies* the physical process!

You can't change the pressure on the outside of the plates. The volume between the plates is the only factor that matters when calculating the pressure between the plates.

You don't like his "formula of personal choice", could you provide another one? I've posted the forumula, could you point out where it goes wrong in the derivation?
 
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Here's an idea, wrt MM's "known forces of nature".

Start with gravity, which is, per his own statements, one such.

IIRC, MM proposed a very simple test which demonstrates that gravity, as a force of nature, exists*; something like this: hold your Tesco plasma ball in one hand, hand facing down; with your other hand underneath it, palm up, let go of the ball ... the ball will drop into your (lower) hand; ergo, gravity exists.

As was pointed out, and as is clear anyway, all this test shows is that the plasma ball falls when released from one's hand; to call that 'gravity' is rather underwhelming.

Call it whatever you want, but it is possible to repeat this process again and again and again, and setup control mechanisms to study the process, etc.

However, we can proceed empirically - being very careful to define just what we mean by this word - and do lots of tests with lots of different objects, in lots of different places, at lots of different times.

This is the part that *cannot* ever be done with DE or inflation. We can't "experiment" at all with Lambda's bag of metaphysical friends. They are not in any way similar to gravity in the sense that we cannot and never will be able to experiment with them in controlled conditions.
 
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