Understanding Virtual Particles: Excitations of Quantum Fields

[eightsquare]

I did some research on Wikipedia, and I quote from the write up on Real Particles:
"The term(Virtual Particles) is somewhat loose and vaguely defined, in that it refers to the view that the world is made up of "real particles": it is not; rather, "real particles" are better understood to be excitations of the underlying quantum fields. Virtual particles are also excitations of the underlying fields, but are "temporary" in the sense that they appear in calculations of interactions, but never as asymptotic states or indices to the scattering matrix."

What I wanted to ask was, what is the meaning of "excitation of the underlying fields"? What quantum field are they talking about? I always thought that in quantum mechanics fields were basically made up of particles. But that brings me back in a loop.

 

[eightsquare]

Why do particles move when force is applied?

According to Wikipedia, a particle is nothing but an excitation of the underlying quantum field. So how exactly are forces defined in quantum mechanics and why does the 'excitation' tend to move when we apply a force to it?

 

[wotanub]

Welcome to PF, 8². I'm not sure what level of physics you have, I think a "mid-level" understanding of quantum mechanics is needed to answer this question. At least the quantum harmonic oscillator and some classical field theory.

I know about this in terms of very basic QFT. Do some research on quantizing the EM field. One can write down the Hamiltonian for an EM field, and find it has a form like the harmonic oscillator. The eigenstates of the corresponding number operator are called Fock states. When the raising operator is applied to the Fock state it increases the quanta of the field by one. The quanta is called a photon and the raising operator is re-termed the creation operator since it creates a qunata. Similarly, the lowering operator is called the annihilation operator. I imagine the approach is similar for whatever kind of field you would like to quantize.

Here's a good lecture video that explains it very clearly.
And the Wikipedia article. http://en.wikipedia.org/wiki/Quantization_of_the_electromagnetic_field

In QM, we really don't discuss forces per se, we prefer to talk about energy. Particles experience force because they have potential energy, and they move because they have momentum, and the force can change momentum, just like in classical mechanics. You can always write down the force, equations of motion, or what have you from the Hamiltonian (energy), but equations of motion really take a back seat in quantum mechanics.

 

[Maui]

Particles somewhat in the future.
For a more detailed response see:

https://en.wikipedia.org/wiki/Quantum_field_theory

and any of the books often recommended here.

 

[mattt]

Quantum Fields are some mathematical objects that appear in some mathematical structures used to produce predictions of the outcomes of some experiments.

 

[The_Duck]

According to Wikipedia, a particle is nothing but an excitation of the underlying quantum field. So how exactly are forces defined in quantum mechanics and why does the 'excitation' tend to move when we apply a force to it?

You can think of a field as the surface of a pond and "excitations" as traveling waves on the surface. Forces appear when different parts of the water have different properties (different "potential energy"), which can cause the waves to bend (toward regions of lower potential energy) instead of propagating in straight lines.

 

[No-where-man]

You can think of a field as the surface of a pond and "excitations" as traveling waves on the surface. Forces appear when different parts of the water have different properties (different "potential energy"), which can cause the waves to bend (toward regions of lower potential energy) instead of propagating in straight lines.

This is very interesting. But is entire universe (well at least this visible observable part of the universe) made of one quantum field or more quantum fields that are directly connected and full of interactions?

 

[eightsquare]

@No-where-Man- I'm pretty sure more than one field. Every elementary particle is considered to be a quanta of their respective fields, and as there are many elementary particles, I'd say there are many fields full of interactions.

To everyone- The vacuum fluctuation model of the beginning of the universe imply that these fields exist even in a vacuum, even when there is no real particle affecting the space around it. Maybe this is a fallout of the Heisenberg uncertainty principle, but does it mean that even the existence of fields is uncertain on the most fundamental level and that even nothing can have fluctuations due to uncertainty?

 

[mpv_plate]

... does it mean that even the existence of fields is uncertain on the most fundamental level and that even nothing can have fluctuations due to uncertainty?

Yes. The fields cannot have definite zero value and definite zero conjugate momentum everywhere all the time because of the canonical commutation relations. Even if there are no particles in the fields.

 

[No-where-man]

Yes. The fields cannot have definite zero value and definite zero conjugate momentum everywhere all the time because of the canonical commutation relations. Even if there are no particles in the fields.

I'm still confused with the answer, I read a lot about Heiseneberg's uncertainity principle, and I'm still not sure if I understand it.
Why wouldn't fields have 0 value and definite zero conjugate momentum everywhere all the time (whatever that means), just because you cannot 100% know both position and momentum at the same time?
I don't understand why would this be a case?

I'm not questioning Heisenberg's uncertainty principle at all, I just don't understand it.

 

[The_Duck]

I'm still confused with the answer, I read a lot about Heiseneberg's uncertainity principle, and I'm still not sure if I understand it.
Why wouldn't fields have 0 value and definite zero conjugate momentum everywhere all the time (whatever that means), just because you cannot 100% know both position and momentum at the same time?
I don't understand why would this be a case?

The uncertainty principle is more general than the one between position and momentum of particles. In field theory, we have an uncertainty relation between the value of a field at a point, and its time rate of change at that point. (Partly to make an analogy to the more familiar position-momentum uncertainty relation, we sometimes call the time rate of change of the field its "conjugate momentum." This is jargon: "momentum" here has nothing to do with the momentum of particles or anything like that).

The position-momentum relation for particles implies that if you confine a particle to some region, its momentum becomes uncertain. We might poetically think of this uncertainty as a result of constant unobserved fluctuations in the position and momentum of the particle. The uncertainty relation described above for fields has a similar result. If a field, for example the electromagnetic field, is "naturally" zero in vacuum, it cannot be exactly zero all the time because of the uncertainty relation between the value of the field and its time rate of change: if we know that the field has a value close to zero, then there is some uncertainty in its time rate of change. Again we can poetically think of this as a result of constant unobserved "vacuum flucuations" of the field, which consist of the value of the field fluctuating in some region around zero.

 

[hilbert2]

In field theory, we have an uncertainty relation between the value of a field at a point, and its time rate of change at that point. (Partly to make an analogy to the more familiar position-momentum uncertainty relation, we sometimes call the time rate of change of the field its "conjugate momentum." This is jargon: "momentum" here has nothing to do with the momentum of particles or anything like that).

A question about this... The generalized uncertainty principle relates the combined uncertainty of two observables to their commutator (two commuting observables can be measured accurately at the same time, a noncommuting observable pair can not). Do the field strength and its conjugate momentum of a fermionic field obey a commutation or an anticommutation relation? With the creation and annihilation operators of fermion fields there seem to be anticommutation rules.

 

[No-where-man]

The uncertainty principle is more general than the one between position and momentum of particles. In field theory, we have an uncertainty relation between the value of a field at a point, and its time rate of change at that point. (Partly to make an analogy to the more familiar position-momentum uncertainty relation, we sometimes call the time rate of change of the field its "conjugate momentum." This is jargon: "momentum" here has nothing to do with the momentum of particles or anything like that).

The position-momentum relation for particles implies that if you confine a particle to some region, its momentum becomes uncertain. We might poetically think of this uncertainty as a result of constant unobserved fluctuations in the position and momentum of the particle. The uncertainty relation described above for fields has a similar result. If a field, for example the electromagnetic field, is "naturally" zero in vacuum, it cannot be exactly zero all the time because of the uncertainty relation between the value of the field and its time rate of change: if we know that the field has a value close to zero, then there is some uncertainty in its time rate of change. Again we can poetically think of this as a result of constant unobserved "vacuum flucuations" of the field, which consist of the value of the field fluctuating in some region around zero.

But wouldn't be possible to actually detect energy value of the field, if you know at least one of properties (either position or momentum)?
I mean can the non-zero energy be detected?
And please read this and tell me what you think:
http://www.sciencedaily.com/releases/2013/03/130303154958.htm

Thanks.

 

[mpv_plate]

Why wouldn't fields have 0 value and definite zero conjugate momentum everywhere all the time (whatever that means), just because you cannot 100% know both position and momentum at the same time?

You can actually know both of them simultaneously (technical remark: quentum fields are not observable, so I'm talking here figuratively), but due to the commutation relations there is a non-zero probability that the values of the fields or their momenta will differ from zero when you next "measure" them.

Heisenberg uncertainty is not saying that you cannot know the non-commuting quantities simultaneously. The uncertainty is only defining the statistical features of repeatedly measured values. But during one measurement you can measure both non-commuting quantities to arbitrary precision simultaneously.

Some details about the vacuum state of quantum fields are http://www.quantumfieldtheory.info/website_Chap03.pdf. Go to page 55, paragraph 3.4.3 Zero Point (Vacuum) Energy.

 

[No-where-man]

You can actually know both of them simultaneously (technical remark: quentum fields are not observable, so I'm talking here figuratively), but due to the commutation relations there is a non-zero probability that the values of the fields or their momenta will differ from zero when you next "measure" them.

Heisenberg uncertainty is not saying that you cannot know the non-commuting quantities simultaneously. The uncertainty is only defining the statistical features of repeatedly measured values. But during one measurement you can measure both non-commuting quantities to arbitrary precision simultaneously.

Some details about the vacuum state of quantum fields are http://www.quantumfieldtheory.info/website_Chap03.pdf. Go to page 55, paragraph 3.4.3 Zero Point (Vacuum) Energy.

Ok, thanks, I thought about zero-point energy but I actually thought this was a crackpot hypothesis not made by true physics, I was wrong:
Can you just comment this link I found:
http://www.sciencedaily.com/releases/2013/03/130303154958.htm

 

[The_Duck]

Do the field strength and its conjugate momentum of a fermionic field obey a commutation or an anticommutation relation?

An anticommutation relation. Also my statement above that the conjugate momentum is the time rate of change of the field isn't true for fermionic fields.

can the non-zero energy be detected?

Yes. One way of thinking about the Casimir effect is in terms of the "zero-point energy" due to these "vacuum fluctuations."

There's a caveat, though: we can't detect the *absolute* energy density due to vacuum fluctuations. In the Casimir effect, for instance, we can only detect the *change* in vacuum energy density produced by the presence of a pair of conducting plates.

 

[Maui]

Can you just comment this link I found:
http://www.sciencedaily.com/releases/2013/03/130303154958.htm

Their experiment highlights a property of quantum systems - that their behavior is dependent on what can be known. You still need a 'strong' measurement for any real reading, the weak measurements are only revealing what the system is doing mostly(this would be classically impossible so interpret as you deem fit). The bottom line is this - they are not really getting aroung the Heisenberg uncertainty principle. They are getting more data than 'usual'(about the first property) but it's as ambiguous as Heisenberg postulated close to a century ago.

 

[eightsquare]

Why are there only a finite number of fields? And do we know why they interact with each other the way they do?

 

[No-where-man]

Why are there only a finite number of fields? And do we know why they interact with each other the way they do?

I will bet that there is a truly infinite number of fields.

 

[ZapperZ]

Why are there only a finite number of fields?

Where do you get such a thing?

Zz.

 

[eightsquare]

@ZapperZ: So is it that only some fields can be quantized and most of them don't interact with each other? Otherwise we'd keep seeing new particles every day.

 

[Bill_K]

Why are there only a finite number of fields? And do we know why they interact with each other the way they do?

There is one field for each type of elementary particle, no more, no less. In the Standard Model, there are (depending on how you count them) 29 different particles. So: 29 fields. (EDIT:Sorry, 36.)

 

[eightsquare]

There is one field for each type of elementary particle, no more, no less. In the Standard Model, there are (depending on how you count them) 29 different particles. So: 29 fields.

So what does Zapper's message mean?

 

[ZapperZ]

@ZapperZ: So is it that only some fields can be quantized and most of them don't interact with each other? Otherwise we'd keep seeing new particles every day.

So what does Zapper's message mean?

You seem to think that when I asked where you get such things, that my question implies such-and-such. I'm trying to figure out WHERE you got the information that allows you to make such a conclusion, so that I know in what context you are asking. I have to know what you know before I actually understand the origin of the question! After all, this thread started with you asking what "quantum fields" are! I have no idea if you've understood what it is and whether you have any understanding of how they relate to the elementary particles.

Zz.

 

[eightsquare]

From what I've read, all fields in quantum mechanics can be quantized. And since we have only a finite number of elementary particles, I concluded that there are only a finite number of fields.

 

[Naty1]

eightsquare...

And since we have only a finite number of elementary particles, I concluded that there are only a finite number of fields.

So far that fits what we know. All electrons are supposedly identical because they are all excitations of same electromagnetic vacuum field [wave] . Nobody knows exactly what an electron 'really' is. All we know is that when it interacts its seems to do so at a point ...like an infinitesimally small particle... but exactly how small that 'point' is remains for the time being smaller than we can detect...but likely bigger than Planck size...


After numerous discussions in these forums, [a couple links to discussions are listed below] the best [relatively non computational] descriptions I have seen include these:

If you are familiar with complex imaginary numbers, like a +bi, this is one way to approach 'particles':

[ The "operators" referred to are mathematical entities [expressions] that make others appear [creation operators] and disappear [annihilation operators. They create and destroy 'particles mathematically.]

...complex imaginary numbers and their operators are associated with virtual particles, which cannot be detected, while complex real numbers and their operators are associated with real [detectable] particles.

There is not a definite line differentiating virtual particles from real particles — the equations of physics just describe particles (which includes both equally). The amplitude that a virtual particle exists interferes with the amplitude for its non-existence; whereas for a real particle the cases of existence and non-existence cease to be coherent with each other and do not interfere any more. In the quantum field theory view, "real particles" are viewed as being detectable excitations of underlying quantum fields. ...

Two other descriptions I like:

Tomstoer

Particles appear in rare situations, namely when they are registered.

Marcus:

The trouble with the particle concept is that one cannot attribute a permanent existence; It only exists at the moment it is detected. The rest of the time there is a kind of spread out thing---a cloud---a wave---a field---something that is less "particular", something that cannot be detected.

Lots more here:

What is a particle:
https://www.physicsforums.com/showthread.php?t=386051

 

[eightsquare]

Thanks.

 

[No-where-man]

eightsquare...So far that fits what we know. All electrons are supposedly identical because they are all excitations of same electromagnetic vacuum field [wave] . Nobody knows exactly what an electron 'really' is. All we know is that when it interacts its seems to do so at a point ...like an infinitesimally small particle... but exactly how small that 'point' is remains for the time being smaller than we can detect...but likely bigger than Planck size...After numerous discussions in these forums, [a couple links to discussions are listed below] the best [relatively non computational] descriptions I have seen include these:

If you are familiar with complex imaginary numbers, like a +bi, this is one way to approach 'particles':

[ The "operators" referred to are mathematical entities [expressions] that make others appear [creation operators] and disappear [annihilation operators. They create and destroy 'particles mathematically.]

Two other descriptions I like:

TomstoerMarcus: Lots more here:

What is a particle:
https://www.physicsforums.com/showthread.php?t=386051

I disagree with Marcus and you, if there were no fields all the phenomena that physics have "seen" so far in the experiments would never be possible in the first place.
If you talk about interaction, no interaction would be possible if these quantum fields did not exist in the first place, because can't interact with the empty void/nothingness.

Interaction would never be possible if fields, regardless if we're watching them or not, did not exist in the first place!
Quantum fields are more than just pure models, they are experimentally, irrefutably proven.

 

[Maui]

Interaction would never be possible if fields, regardless if we're watching them or not, did not exist in the first place!
Quantum fields are more than just pure models, they are experimentally, irrefutably proven.

I agree, I think this is entirely correct and I am willing to take it a step further and say that obviously the MWI can not be entirely wrong and neither can the orthodox CI. The CI needs the MWI for the real wavefunctions and the MWI needs the CI for the preferred basis problem. The preferred basis problem can be 'solved' if we accept that brains cannot observe quantumness (the hup and some experiments link knowledge and behavior of quantum particles) and probably brains single out the single reality that we observe because that is the only possible way to make sense of reality(and brains are about making sense of things). When brains go wrong due to schizophrenia or LSD or even in dreams during sleep, their neurons probably could not get the right pattern for making complete sense of the reality of fields/possibilities. This(the idea that brains could be interface between the fields and single classical-like reality) allows the world to be completely quantum and yet experienced as completely classical and comprehensible with the utilization of quantum computing while providing some clues into the nature of human experience, the nature of dreams and sheds some light on what is out there (quantum fields).

I can see no contradiction or conflict with known experiments and it's compatible with locality, realism and known science that rests on them both while both the mwi and the ci when taken separately struggle to explain adequately the outside world of observations. Even decoherence makes sense as the classical world happens at the time of information becoming available about quantum systems and in this framework the role of decoherence appears natural.

 

[No-where-man]

I agree, I think this is entirely correct and I am willing to take it a step further and say that obviously the MWI can not be entirely wrong and neither can the orthodox CI. The CI needs the MWI for the real wavefunctions and the MWI needs the CI for the preferred basis problem. The preferred basis problem can be 'solved' if we accept that brains cannot observe quantumness (the hup and some experiments link knowledge and behavior of quantum particles) and probably brains single out the single reality that we observe because that is the only possible way to make sense of reality(and brains are about making sense of things). When brains go wrong due to schizophrenia or LSD or even in dreams during sleep, their neurons probably could not get the right pattern for making complete sense of the reality of fields/possibilities. This(the idea that brains could be interface between the fields and single classical-like reality) allows the world to be completely quantum and yet experienced as completely classical and comprehensible with the utilization of quantum computing while providing some clues into the nature of human experience, the nature of dreams and sheds some light on what is out there (quantum fields).

I can see no contradiction or conflict with known experiments and it's compatible with locality, realism and known science that rests on them both while both the mwi and the ci when taken separately struggle to explain adequately the outside world of observations. Even decoherence makes sense as the classical world happens at the time of information becoming available about quantum systems and in this framework the role of decoherence appears natural.

Finally someone sees what I'm saying, thanks for the support.
Yes, if fields do not exist, how do you make interaction with something that does not exist (regardless, if you don't observe/watch or have any effect on these fields)?
Answer is: you don't, because it does not exist, so yes, fields do definitely 100% exist independently outside of all of our interactions with fields (energy fields, force fields, quantum fields and similar), otherwise there would never be any interaction with anything ever.

 

[Naty1]

I disagree with Marcus and you, if there were no fields all the phenomena that physics have "seen" so far in the experiments would never be possible in the first place.

Two things wrong with this statement: First, Neither Marcus nor I said 'fields don't exist'. Second, there is no proof that 'fields' are the only way to construct theoretical models. As an example, general relativity is not a field theory, but rather rather a geometrical theory. We use field theory because it provides really good predictions...see below.

In QM the Schrodinger wave equation describes the continuous time evolution of a system's wave function and is deterministic. However, the relationship between a system's wave function and the observable properties of the system appear to be non-deterministic. An early viewed detection involved 'collapse of the wavefunction' upon detection, a more modern perspective newer view is 'decoherence'. There are subtleties between the two that have been at least partially dissected in these forums.

I'm guessing you did not read the link I posted previously to WHAT IS A PARTICLE. If you read that extensive discussion, you will begin to understand how complex and subtle the definition and detection of quantum fields is...in fact one can not directly detect them. One detects 'particles', the local observable quanta.

How that compares with the magazine article mentioned in this discussion, "Getting Around the Uncertainty Principle..", will be difficult to tell because even the title of the article is silly. The language seems pop science rather than science, but maybe there IS something unique and different in their work. If so, it should appear in peer reviewed scientific journals.

MPV's post is correct:

Heisenberg uncertainty is not saying that you cannot know the non-commuting quantities simultaneously. The uncertainty is only defining the statistical features of repeatedly measured values. But during one measurement you can measure both non-commuting quantities to arbitrary precision simultaneously.

HUP says nothing about making two concurrent measurements, it addresses similarly prepared systems and the statistical distribution of the resulting measurements.


Here are two other posts from the WHAT IS A PARTICLE discussion which I believe are accurate: [slightly edited by me]


Meopemuk:

According to scientific method we are not allowed to speculate about things that cannot be registered/observed/verified. If we do use such unobservable things (e.g., wave functions, quantum fields, etc) in our formalism we should keep in mind that these are mathematical tools unrelated to the physical world……

Stoer:

But with the concept of particles alone you are not able to calculate anything beyond classical physics: No quantum mechanics, no atoms, no spectra, no nuclei, no nucleons, no quarks, ... they all rely on unmeasurable concepts like wave functions, field operators, Hilbert spaces, etc. You can't register them, but have to live with them if you want to do physics. And these formalisms (which you can't measure) produce results in nearly perfect agreement with measurements. So you can't avoid the conclusion that this ‘unrealistic’ formalism describes nature.

 

[No-where-man]

Two things wrong with this statement: First, Neither Marcus nor I said 'fields don't exist'. Second, there is no proof that 'fields' are the only way to construct theoretical models. As an example, general relativity is not a field theory, but rather rather a geometrical theory. We use field theory because it provides really good predictions...see below.

In QM the Schrodinger wave equation describes the continuous time evolution of a system's wave function and is deterministic. However, the relationship between a system's wave function and the observable properties of the system appear to be non-deterministic. An early viewed detection involved 'collapse of the wavefunction' upon detection, a more modern perspective newer view is 'decoherence'. There are subtleties between the two that have been at least partially dissected in these forums.

I'm guessing you did not read the link I posted previously to WHAT IS A PARTICLE. If you read that extensive discussion, you will begin to understand how complex and subtle the definition and detection of quantum fields is...in fact one can not directly detect them. One detects 'particles', the local observable quanta.

Than going by your critics, gravity does not exist either because none can detect it, only its effects on surrounding environment/space, Earth electromagnetic field does not exist because none can actually detect it, because you only see/detect its effects, not the electromagnetic field/energy itself!
There is obviously something wrong with this reasoning, because there no doubt there is gravity there, there is no doubt that there are electromagnetic fields including Earth's own EM field (EM=electromagnetic).
Even when you have electrically neutral atoms, there is still energy and electromagnetic energy (and force).
Even our bodies have EM fields, everything basically, and gravity is the reason

Let's have one example: Gravity affects space-that alone directly 100% proves that space alone is not truly empty, something that is truly empty cannot be affected by anything, let alone gravity.
Which means every point of space is full of energy of course, this is only visible/detectable/measurable from sub-atomic level to below that level, the point here there is no such thing a s absolute nothingness (there is always something) and the fact you have space-space itself is something, not nothing, nothing means nothing!
Completely empty space would not be able to create/destroy anything in the first place, because it is completely empty-no energy no nothing, there would be no fuel/energy to start the process and to start activity and to start doing any kind of work in the first place-so no there is no such thing as completely empty space as well as there is no such thing as absolute nothingness!
You always have to have space and energy to start with in the first place.

I'm actually sure that when Lawrence Krauss said that universe came from nothing, he meant universe came from quantum fluctuations (again this is not nothing), and quantum fluctuations did not come from nothing as shown in popular books from Hawking, Greene and similar physicists, the very fact quantum fluctuations (includes virtual particles/anti-particles) are created and annihilated proves they did not come from nothing/nothingness, but from some energy or energy field (even if the quantum field theory is somehow wrong).

The same reason why the Big Bang did not come from nothing:
I took this from another forum:
"It's important to distinguish the philosophical definition of nothing from the scientific definition of nothing. Empirically, nothing means you are talking about non-existence. The quantum vacuum/quantum void is devoid of particles but is a physical object that still has energy, pressure, and also exist in different energy states. The philosophical definition of nothing is a universal negation. This negation includes logic, universal laws, and ideas as well. This means that nothing (philosophically) would include the negation of even the ontology of a quantum vacuum/quantum void.
When Krauss talks about nothing he is speaking empirically about very specific objects non-existence in a space and is not truly talking about nothing.

We don't know and we can't know. There essentially was no "before" the Big Bang as far as we are concerned. Obviously we are concerned about it, because we can speculate and imagine, but that is about all we can do.

As for the universe coming from "nothing" that isn't true in a literal sense. There is absolutely no such thing as "nothing" to begin with. The "the universe came from nothing" stuff is glossing over the details to convey that the time and space we know began with the Big Bang, and other time and other space that existed before the Big Bang that created our universe, that is not part of our universe and is not really operable from within it. Meaning time and space before the Big Bang, it is classified as nothing to us, but it's not literally nothing, because this time and space before the Big Bang is simply, just unknown to us forever.

How that compares with the magazine article mentioned in this discussion, "Getting Around the Uncertainty Principle..", will be difficult to tell because even the title of the article is silly. The language seems pop science rather than science, but maybe there IS something unique and different in their work. If so, it should appear in peer reviewed scientific journals.

As far as I know, Scientific American is serious, scientific magazine, and you do know that every time an article is published in any scientific magazine is peer-reviewed, so Scientific American is trustworthy, however, everyone need to read deep every word in it I bet you'll see that's not what they are saying (the same thing with the temperature with absolute zero thing-which was not really below absolute zero at all).

MPV's post is correct:
HUP says nothing about making two concurrent measurements, it addresses similarly prepared systems and the statistical distribution of the resulting measurements. Here are two other posts from the WHAT IS A PARTICLE discussion which I believe are accurate: [slightly edited by me]Meopemuk:

Stoer:

Ok, big thanks for this, but all I'm saying you can't have nothing, you'll always have some kind of undetectable energy or energy field (and that requires space to exist in the first place because, everything requires and actually has diameter, size and volume to exist/that exists in the first place, no matter how big and how small/tiny something is) as described above, that's all.

However, Casimir's effect irrefutably proved there is no such thing as completely empty space no matter what size does it have.
Cheers and big thanks for this explanation and for the posts that Meopemuk and Stoer posted and explained regarding fields and other hypothetical terms in physics.
That's all, big thanks again.

 

[Drakkith]

I disagree with Marcus and you, if there were no fields all the phenomena that physics have "seen" so far in the experiments would never be possible in the first place.
If you talk about interaction, no interaction would be possible if these quantum fields did not exist in the first place, because can't interact with the empty void/nothingness.

Interaction would never be possible if fields, regardless if we're watching them or not, did not exist in the first place!
Quantum fields are more than just pure models, they are experimentally, irrefutably proven.

The concept of the field is just a way to predict and explain how our universe works. It's possible I could come up with a way to explain all observable effects using invisible fairies. How would you know which theory is right? The fairies, or the fields?

You don't. You can't. It isn't possible if both explain observations equally well.
So no, you don't know if fields exist or not. You can't know. It isn't possible.

Nothing is 100% proven. Nothing is irrefutable. Ever. Remember that.

 

[Naty1]

no where man...

a good portion of your post #32 is incorrect and strays from the OP's question.
If you'd like to discuss all those issues, try a separate post.

 

[Maui]

The concept of the field is just a way to predict and explain how our universe works. It's possible I could come up with a way to explain all observable effects using invisible fairies. How would you know which theory is right? The fairies, or the fields?

For obvious reasons, your 'model' can not make a correct prediction and this is kind of important in physics

Otherwise, I agree with your philosophical considerations, be it that they are somewhat too strong for my taste.

 

[Drakkith]

For obvious reasons, your 'model' can not make a correct prediction and this is kind of important in physics

But you haven't even seen all the nifty graphs I made!

 

[No-where-man]

The concept of the field is just a way to predict and explain how our universe works. It's possible I could come up with a way to explain all observable effects using invisible fairies. How would you know which theory is right? The fairies, or the fields?

You don't. You can't. It isn't possible if both explain observations equally well.
So no, you don't know if fields exist or not. You can't know. It isn't possible.

Nothing is 100% proven. Nothing is irrefutable. Ever. Remember that.

Like I said, all I'm saying that you can't have nothing, there is always something some energy.
Well, you can't say nothing is ever proven, energy is proven for example.
Earth's electromagnetic field does exist, and it is 100% proven, for example. So fields do exist (you can make your own electromagnetic field as well, entropy is proven, there are plenty of things in science 100% proven, however there are a lot of things and concepts in science that could never be 100% proven.
Gravity is 100% proven as well.
However, when it comes to quantum fields, than things get harder to understand, but like physicists always there is no such thing as absolute nothingness and you can't have anything without energy and work (which is a form of energy).

 

[No-where-man]

no where man...

a good portion of your post #32 is incorrect and strays from the OP's question.
If you'd like to discuss all those issues, try a separate post.

I don't see, how is it false, if it's based on facts.

 

[Drakkith]

Like I said, all I'm saying that you can't have nothing, there is always something some energy.

As far as we know. This is not guaranteed.

Well, you can't say nothing is ever proven, energy is proven for example.

Is it? What exactly do you mean by "energy is proven"?

Earth's electromagnetic field does exist, and it is 100% proven, for example.

Again, what do you mean by saying it is 100% proven? All we know is that our measuring instruments act in certain ways that we attribute to something we call an electromagnetic field. What if in the future a new theory comes about that completely does away the concept of the traditional EM field? You can't claim that it's 100% proven if that happens.

Gravity is 100% proven as well.

Statements such as "X is 100% proven" mean very little. If you mean that it is 100% proven that something appears to hold us to the Earth and cause matter to attract all other matter, then sure. But that's not science. That's just observing that something's going on without trying to figure out how it works. The explanation, which is what we are talking about when we talk about science, is never 100% proven. And that's what a field is. It's a way of explaining and figuring out how our universe works. We believe it exists because we have no better way of explaining our observations.

 

[No-where-man]

As far as we know. This is not guaranteed.

Yes, it is. Because nothing means nothing, fro example; what is your debt nothing-nothing in this case means non-existence of your debt, meaning in general nothing is non-existence, you can't create something that exists from something that does not exist-this is the basic rule.

Is it? What exactly do you mean by "energy is proven"?

I'm not sure it's smart to continue, especially for me, since when exactly the post is becoming trolling?
I will answer you this question, for example you eat food, you will have energy when you eat food, energy is tangible and physical, if it wasn't, you'd die from the food, if food does not contain energy, actually for every single process, universe or not, you need energy.
Sure we call this energy, but it's crucial for the existence of the universe and it's crucial for our own existence and survival, as well.

Again, what do you mean by saying it is 100% proven? All we know is that our measuring instruments act in certain ways that we attribute to something we call an electromagnetic field. What if in the future a new theory comes about that completely does away the concept of the traditional EM field? You can't claim that it's 100% proven if that happens.

So, if there is no such EM field around the Earth, it means radiation will kill we like it or not, the fact this field protects us, Aurora borealis and Aurora australis prove this.

Statements such as "X is 100% proven" mean very little. If you mean that it is 100% proven that something appears to hold us to the Earth and cause matter to attract all other matter, then sure. But that's not science. That's just observing that something's going on without trying to figure out how it works. The explanation, which is what we are talking about when we talk about science, is never 100% proven. And that's what a field is. It's a way of explaining and figuring out how our universe works. We believe it exists because we have no better way of explaining our observations.

Fair enough, but you call it gravity and gravitational field and its effects here on Earth are real.
But I can't pass that everything that is explained in science is not 100% proven, there is a lost of things/phenomenons in science 100% proven, the way they work and their effects on their surrounding environments/space, as well as proven, however there are many more things/phenomenons in science that are never proven 100%.

If at least one part of the hypothesis or theory works (and it's scientifically proven every single moment/time) in reality exactly in the way reality works, than there is nothing else to prove, than this part of hypothesis or theory is 100% proven.
That's what I'm trying to say, and I think that's a fair statement.
Cheers.

 

[Drakkith]

Yes, it is. Because nothing means nothing, fro example; what is your debt nothing-nothing in this case means non-existence of your debt, meaning in general nothing is non-existence, you can't create something that exists from something that does not exist-this is the basic rule.

Again, as far as we know this is true. We only believe this to be true because we have never observed a contradiction to the rule. We can never be absolutely sure.

So, if there is no such EM field around the Earth, it means radiation will kill we like it or not, the fact this field protects us, Aurora borealis and Aurora australis prove this.

Nonsense. Just because a new theory is developed does not mean that somehow the real effects of the EM field suddenly go away.

Fair enough, but you call it gravity and gravitational field and its effects here on Earth are real.

That's what I'm getting at. If I develop another theory for gravity that works and doesn't use geometry or fields, it in no way changes the fact that gravity still works exactly as it always has.

If at least one part of the hypothesis or theory works (and it's scientifically proven every single moment/time) in reality exactly in the way reality works, than there is nothing else to prove, than this part of hypothesis or theory is 100% proven.
That's what I'm trying to say, and I think that's a fair statement.
Cheers.

I disagree completely.

 

[Maui]

Drakkith, you are taking your initially reasonable argument way too far into scepticism, almost into Heyerabend's Epistemological anarchism territory(and I am not sure that even philosophers agree with his views)

There is obviously a difference between empirically confirmed scientific models which get falsified but remain true in some domains and mysticism/religious beliefs.
There is no better theory of the interaction of matter in spacetime than QFT and its predictions hold up every time. This usually means that we have a very good map of the territory. Even if the theory is one day disproved in experiment, it will remain approximately valid, so the concept that reality is composed entirely and solely of fields will remain. What will surely not remain intact is the human concept of reality as that concept is based on assumptions and as long as experiments do not agree with it, it will be prone to modifications.

 

[jtbell]

This thread has moved from physics to philosophy. Since we do not have a philosophy forum, this thread is now closed.