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A. Neumaier submitted a new PF Insights post
Misconceptions about Virtual Particles
Continue reading the Original PF Insights Post.
Misconceptions about Virtual Particles
Continue reading the Original PF Insights Post.
Nothing virtual happens. The dry facts are that two real particles are created from gravitational energy (from two gravitons or from an external gravitational field), not from the vacuum. One particle escapes, the other is absorbed. A valid description is given on p.645 of the bookBuzz Bloom said:misconceptions related to Hawking radiation and virtual particles?
Take a look at page 4 of http://www.itp.uni-hannover.de/~giulini/papers/BlackHoleSeminar/Hawking_CMP_1975.pdf; what you heard was the "heuristic" explanation for non-specialists although the rest of the paper will give you the whole story. Also try this link: http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/hawking.htmlBuzz Bloom said:As I recall, it was in the 1970s
when I attended a presentation at MIT by Hawking describing his concept of black hole radiation based on the creation of particle pairs which due to great tidal forces of the black hole would separate, one particle falling towards the black hole, and the other escaping and somehow becoming transformed by this into a real particle.
"They cannot be said to exist in space and time, have no position, no meaningful probabilities to be created or destroyed anywhere, no life-time, cannot cause anything, interact with anything or affect anything."
The Casimir force per unit areafor idealized, perfectly conducting plates with vacuum between them is
where
(hbar, ħ) is the reduced Planck constant,
is the speed of light,
is the distance between the two plates
The pushing is done by the Casimir force caused by the two surfaces - not by the space in between. Note that this space between the surfaces - what is informally called a vacuum - is not truly empty, it is still filled with the quantum fields emanating from the surfaces. Just like the space between the sun and the planets is not empty but filled with the gravitational field.Jeronimus said:If this is the case, then can you explain what is pushing two highly polished surfaces/mirrors together in a vacuum(absent of gravity i assume as well) with a force which increases greatly when reducing the distance?
[5] is a famous paper by Jaffe 2005 where the physically sound explanation is discussed in detail without any virtual magic.wikipedia said:Casimir's original goal was to compute the van der Waals force between polarizable molecules" of the conductive plates. Thus it can be interpreted without any reference to the zero-point energy (vacuum energy) of quantum fields.[5]
Unfortunately the policy of wikipedia that in case of controversy all points of view must be discussed in a neutral way implies that wikipedia necessarily spreads an amount of nonsense proportional to that held in the general public. What counts in the eyes of wikipedia is not the correctness of a view but whether the view exists and how frequent it is.Jeronimus said:From wikipedia
wikipedia said:People of all ages, cultures and backgrounds can add or edit article prose, references, images and other media here. What is contributed is more important than the expertise or qualifications of the contributor. What will remain depends upon whether the content is free of copyright restrictions and contentious material about living people, and whether it fits within Wikipedia's policies, including being verifiable against a published reliable source, thereby excluding editors' opinions and beliefs and unreviewed research. [wikipedia source]
There is no clear definition of what a ''reliable source'' is, but sources from the popular science literature (which are full of misinformation about virtual particles) are definitely not excluded.wikipedia said:All encyclopedic content on Wikipedia must be written from a neutral point of view (NPOV), which means representing fairly, proportionately, and, as far as possible, without editorial bias, all of the significant views that have been published by reliable sources on a topic. [wikipedia source]
A. Neumaier said:The pushing is done by the Casimir force caused by the two surfaces - not by the space in between. Note that this space between the surfaces - what is informally called a vacuum - is not truly empty, it is still filled with the quantum fields emanating from the surfaces. Just like the space between the sun and the planets is not empty but filled with the gravitational field.
They cannot have any causal effect since they don't exist in a spatial-temporal sense, as explained in the Insight article. They affect something only in the same platonic sense as each contribution ##x^n/n!## in the power series expansion of ##e^x## has an effect on the value of the exponential function at ##x##, although the value of the latter is independent of the way it is computed. (No sensible computer program computes ##e^{-10}## from the power series.)Jeronimus said:if virtual particles have an effect
As the paper by Jaffe shows, the Casimir effect is independent of the notion of a virtual particle. Thus nothing changes whether you add or don't add empty talk about the latter.Jeronimus said:What should be the case but is not, because those virtual particles do not exist or if they do, have no effect whatsoever.
Indeed. The latter is only what popular science says.Jeronimus said:the vacuum IS truly empty when there are no objects around. According to you, no virtual particles pop in and out of existence for a short period of time supposedly allowed by the Heisenberg uncertainty principle as some claim.
“This paper describes the test campaigns designed to investigate and demonstrate viability of using classical magnetoplasmadynamics to obtain a propulsive momentum transfer via the quantum vacuum virtual plasma. This paper will not address the physics of the quantum vacuum plasma thruster (QVPT)…”
-Anomalous[/PLAIN] Thrust Production from an RF Test Device Measured on a
Low-Thrust Torsion Pendulum. 2014.More recently, on April 5, 2015, NASA Eagleworks reported a new computational simulation that models the EmDrive’s thrust as a three-dimensional magnetohydrodynamic flow of electron-positron pairs of the quantum vacuum – the polarizable structure of the vacuum.
http://resonance.is/wp-content/uploads/2015/06/thruster.jpg
In effect, the NASA team believes that the engine produces thrust via a momentum transfer with polarizable structure of the quantum vacuum. The central idea is that space is not empty, it is filled with energetic oscillations and as well, means that there is no truly isolated system, and hence no violation of the conservation of momentum if an equal force is being transferred to the quantum vacuum opposite to the forward thrust of the engine.
This is a typical popular science article (count the ratio of formulas to text to get a first idea about this), and fits perfectly what I am discussing in the Insight article.Jeronimus said:Here is one more article which seems to undermine the theory of vacuum fluctuations/virtual particles having a real effect.
One cannot falsify unscientific stuff - precisely this makes it unscientific, and is sufficient ground to dismiss it.Jeronimus said:it is also a good thing to not dismiss any theory unless you can falsify it by an experiment.
A. Neumaier said:The Casimir force is explained correctly as a van der Waals force - the same force that holds an argon cluster together. Van der Waals forces are residual forces due to partial cancellation of the electromagnetic quantum field of the nuclei and elecrons making up the surfaces.
A. Neumaier said:Since virtual particles are objects in diagrams drawn on paper without any state that would give them properties in space and time, one cannot do any experiments to test their properties.
"Hawking" not "Hawkins". No, he is not a pop scientist, but you are mistaken about the relationship between virtual particles and Hawking radiation. It's a very common misunderstanding (and one that Hawking himself is partly responsible for), but it's a misunderstanding. Take a look at post #6 of this thread for more.Jeronimus said:Hawkins radiation is supposed to be 1 virtual particle falling into the black hole while the other is accelerated away of it, becoming a "real" particle.
Is Hawkins just a pop scientist?
Jeronimus said:Well, sure, if you define virtual particles to have no state or properties, of course you can not test for them. But that is certainly not the theory you are supposed to falsify and test for.
Obviously, the theory in which virtual particles are responsible for pushing two highly polished conducting plates together in a vacuum, is based on virtual particles which do have properties and affect "stuff". Hawkins radiation is supposed to be 1 virtual particle falling into the black hole while the other is accelerated away of it, becoming a "real" particle.
Is Hawkins just a pop scientist?
Now maybe he is, but your reply to my post seemed rather unscientific in my opinion. You simply defined virtual particles to have no properties and therefore we cannot test for them.
That would be similar to saying "Your theory about quarks is wrong, because in my theory, protons and neutrons are indivisible, therefore quarks cannot exist and one cannot test for them"
Jeronimus said:Well, sure, if you define virtual particles to have no state or properties,
Jeronimus said:Obviously, the theory in which virtual particles are responsible for pushing two highly polished conducting plates together in a vacuum,
No, Hawking is doing both science and trying to explain science to laymen. If you check his publications, you won't find any "virtual particle is falling into a black hole", because there is no such thing. You will find calculations that do not involve virtual particles at all. But those calculations are impossible to describe to laymen accurately, so the description with the virtual particles was invented. It is not true, but it sounds nice - if you don't understand the actual physics.Jeronimus said:Is Hawkins just a pop scientist?
friend said:There are such things as real particles, right? And there was a time before there were these real particles, during inflation, for example, right? It does seem that real particles do pop into existence from the vacuum when acceleration is involved such as in Hawking radiation, or the Unruh effect, or during reheating after inflation. If the vacuum does not consist of virtual particles, then how did these real particles come into being from the vacuum during these effects that I mentioned?
Particles are created from energy through the process of pair production (Google for it) - this has nothing to do with virtual particles.friend said:There are such things as real particles, right? And there was a time before there were these real particles, during inflation, for example, right? It does seem that real particles do pop into existence from the vacuum when acceleration is involved such as in Hawking radiation, or the Unruh effect, or during reheating after inflation. If the vacuum does not consist of virtual particles, then how did these real particles come into being from the vacuum during these effects that I mentioned?
In every treatment of quantum field theory, the vacuum is defined as the eigenstate of all number operators with corresponding eigenvalue zero. This implies that everywhere and at any time the vacuum contains exactly zero particles (in any interpretation of quantum mechanics), without the slightest uncertainty.friend said:If the vacuum does not consist of virtual particles, then how did these real particles come into being from the vacuum during these effects that I mentioned?
This is not true, and I don't see where you would get such a misconception from. This discussion has nothing to do with accelerations.friend said:Isn't it true that virtual particles are just another name for quantum fluctuations from which these real particle come when there's acceleration?
You can measure an electric field, for example, without problems.friend said:And it seems we aren't able to actually measure the quantum fields but only the particles they produce, right?
mfb said:This is not true, and I don't see where you would get such a misconception from. This discussion has nothing to do with accelerations.
Yes, popular science is full of this, respected physicists promote these fantasies in their popular science books, and wikipedia's neutrality policy forces the article writers to represent the popular science fantasies as facts. Therefore they are widely believed and hard to eradicate.stevendaryl said:I don't think his comments were completely out of the blue.
Even the buckyball field? I doubt it.stevendaryl said:Well, the view of quantum field theory is that the fundamental property is the field (of various types), which exists through all of space. For example, the electromagnetic field. These fields can have fluctuations or waves through them, which propagate according to some wave equation. But these are quantum fields, not classical fields, so these fluctuations are quantized, in the same way that the energy for a harmonic oscillator is quantized. Perturbations in the fields due to inflation or whatever causes fluctuations, and these fluctuations manifest themselves as particles. It's possible that a description in terms of virtual particles acquiring enough energy to become real particles might be a useful heuristic, but it's not fundamentally what's going on. The field-theoretic view says that even in vacuum, these fields are present, it's just that vacuum is the lowest energy state of these fields.
Its density is zero everywhere when no buckyballs are around. In this sense the field is always present.Jilang said:Even the buckyball field? I doubt it.
But (in principle) measurable constructs: One can check whether or not people are in the room, buckyballs are present, or the magnetic field is nonzero. Presence = being significantly nonzero.Jilang said:They are constructs.
Nugatory said:the description of the force as arising from virtual particle interactions is just a heuristic.
mfb said:You will find calculations that do not involve virtual particles at all. But those calculations are impossible to describe to laymen accurately, so the description with the virtual particles was invented. It is not true, but it sounds nice - if you don't understand the actual physics.
A. Neumaier said:Nothing virtual happens. The dry facts are that two real particles are created from gravitational energy (from two gravitons or from an external gravitational field), not from the vacuum. One particle escapes, the other is absorbed.
Then what is the cosmological constant if not the vacuum energy that is doing something - accelerating the universe? This is not the result of real particle interaction. So there must be something going on in the world of the virtual that is having a real effect, right?A. Neumaier said:Nothing virtual happens.
Maybe it is just a term in general relativity. This is by far the easiest option.friend said:Then what is the cosmological constant if not the vacuum energy that is doing something - accelerating the universe?
friend said:There are such things as real particles, right?
friend said:And there was a time before there were these real particles, during inflation, for example, right?
friend said:It does seem that real particles do pop into existence from the vacuum when acceleration is involved