Virtual particles

  • Thread starter byron178
  • Start date
157
0
ive been reading on this forum that virtual particles flat out dont exist?then why is it said they exist for a certain amount of time?
 

Bill_K

Science Advisor
Insights Author
4,155
194
On the contrary one could argue that nonvirtual particles do not exist. Every particle is virtual since it is always en route from one interaction to the next.
 
696
147
ive been reading on this forum that virtual particles flat out dont exist?then why is it said they exist for a certain amount of time?
Existence is a difficult concept. Virtual particles are a component of a mathematical model. Some models like Lattice QFT don't have virtual particles. Virtual particles are a mathematical term in the perturbation model of QFT, they are internal lines in a Feynman diagram.

Bill is right, it is difficult to see where real takes over from virtual. Virtual photons are the squiggly lines in a Feynman diagram they always terminate on a charged particle, but so do real photons, they just live longer.
 
351
4
ive been reading on this forum that virtual particles flat out dont exist?then why is it said they exist for a certain amount of time?
My understanding of Hawking's model of black-hole evaporation is that it can be explained by virtual particle/antiparticle pairs separated by the event horizon. The discussion doesn't sound like the particles are purely mathematical constructs.
 
868
3
As I said in another thread, both existence and nonexistence claims have nothing to do with theory. They are interpretations pure and simple. QM does not need a single interpretation, including Copenhagen, to work just fine. Existence claims may be conceptually useful for both comprehension and developing extensions, but theoretically pointless to a given theories validity.

"Shut up and calculate" does not mean something does or does not exist, it means "shut up and calculate".
 
1,675
3
This is true but it TOTALLY doesn't answer the question.

None of it may be real but gets the right answers anyway? This no way to conduct physics.
 
868
3
This is true but it TOTALLY doesn't answer the question.

None of it may be real but gets the right answers anyway? This no way to conduct physics.
I would agree, I love working my way through ontological interpretations. My main objection was to those who claim categorically that "virtual particles flat out dont exist". Not because they are right or wrong, but because such a claim is simply not theory dependent. By making such a claim as if it was strictly factual it opens the doors to others claiming the opposite is strictly factual based on some alternate and equally valid interpretation. Not where the stated purpose of this forum was intended to take us.

Personally I am partial to ontological realness, even if only in the sense of a verb at the level being considered. Yet either claim of real or not real is a prejudice given what we have to work with, not a scientific claim.
 
157
0
I would agree, I love working my way through ontological interpretations. My main objection was to those who claim categorically that "virtual particles flat out dont exist". Not because they are right or wrong, but because such a claim is simply not theory dependent. By making such a claim as if it was strictly factual it opens the doors to others claiming the opposite is strictly factual based on some alternate and equally valid interpretation. Not where the stated purpose of this forum was intended to take us.

Personally I am partial to ontological realness, even if only in the sense of a verb at the level being considered. Yet either claim of real or not real is a prejudice given what we have to work with, not a scientific claim.
so they are real for a fraction of a second and some think they dont exist at all?
 
868
3
so they are real for a fraction of a second and some think they dont exist at all?
IMO: That is like asking how long a tornado stays real. Only the inability to model exactly what is real about it remains a problem that restricts such statements to mere opinion.
 
157
0
IMO: That is like asking how long a tornado stays real. Only the inability to model exactly what is real about it remains a problem that restricts such statements to mere opinion.
so your saying there is no way to test out virtual particles? will a future theory test them?and your saying in your own opinion they are real.
 
157
0
My understanding of Hawking's model of black-hole evaporation is that it can be explained by virtual particle/antiparticle pairs separated by the event horizon. The discussion doesn't sound like the particles are purely mathematical constructs.
but hawking radiation has never been observed.
 
Yes, it is problem.Until and unless the suggested entity is experimentally found to be plausible its existence is doubtful.
I haven't heard of any the "Virtual particles" getting detected anywhere also never heard of an experiment which experimentally clarify their "properties".
(Please cite examples if you do think I'm wrong, i'll be happy to be proved wrong:-)
 
868
3
so your saying there is no way to test out virtual particles? will a future theory test them?and your saying in your own opinion they are real.
We can test the effects of virtual particles. We can even supply the energy to make them "real". But the non-realist will simply say that the energy we supplied made them real and they were not real before we did that.

The problem is nobody knows how to construct a model using real things that everybody can agree is real. This is because everything that we can test at a fundamental enough a level comes and goes at random, like the virtual particles. If it is real in a sense everybody can agree on then where is it coming and going from and to? Nobody knows. We just know that the math works telling us how often and how much on average to expect it to come and go. We only know enough stays around to keep us here, but even that tends to not stay put in a way that parts make sense. Like the double slit experiment. Meanwhile we have parts (quanta), but the parts are not things they are properties, and these properties will flow from one to the other. Even fundamental particles can be annihilated, though their energy remains. How much sense does it make to have parts that break up into things that randomly come in and out of existence yet can form new parts?

Unless or until these questions can be answered, if they even can, speculation of real or not real is just that, speculation. If we are made of real stuff nobody has ever figured out what that stuff really is.
 
24
1
i read that they where detected using casimir effect
 
As space expands, isn't the frequency of virtual particles increasing?
 
351
4
but hawking radiation has never been observed.
The opening query of this post is the claim that virtual particles 'flat-out don't exist'. Hawking is a highly imaginative theorist, but his exploitation of flat-out non-existent particles is hardly comparable to that of exploiting the aether, or phlogiston.

The non-observation, incidentally, is not a falsification of Hawking evaporation proper. We need a positive observation of a radiation-signature of some process antithetical to Hawking evaporation: if x is happening, y cannot be happening.
_______

On, the other hand, I may have the cart before the horse: Hawking radiation would be as much evidence of virtual particles as Hawking BH-evaporation.
 
Last edited:
351
4
i read that they where detected using casimir effect
The Casimir effect doesn't require virtual particles, rather some form of vacuum energy. However, given the extremely short wavelengths of energy implied, I would wonder if the spontaneous production of short-lived particle-pairs wouldn't be a necessary consequence, at least once in a while. High-energy photons have some of the characteristics of particles anyway.

________

Here's a link, however, refuting the 'Casimir effect' per se:

https://www.physicsforums.com/showthread.php?t=484739

#3 post.
 
Last edited:
343
0
The existence of virtual particles relies on a certain interpretation of perturbation theory, which is useful, but completely arbitrary. The visualization as Feynman diagrams where particles are exchanged makes calculations simple but shouldn't be taken as a picture of reality. Virtual particles are not needed in order to explain any result of QFT, so why should we introduce them?
 
351
4
The existence of virtual particles relies on a certain interpretation of perturbation theory, which is useful, but completely arbitrary. The visualization as Feynman diagrams where particles are exchanged makes calculations simple but shouldn't be taken as a picture of reality. Virtual particles are not needed in order to explain any result of QFT, so why should we introduce them?
The post queries the idea 'flat-out don't exist'. Parsimony does indeed exclude them if they are nothing more than convenient book-keeping. Are there other lines of evidence suggesting their existence?
 
343
0
The post queries the idea 'flat-out don't exist'. Parsimony does indeed exclude them if they are nothing more than convenient book-keeping. Are there other lines of evidence suggesting their existence?
Not as far as I know. To my knowledge, everything speaks against virtual particles:

-) they were never detected
-) they are not needed for theoretical explanations of actual phenomena
-) they only appear within a certain approach (perturbative quantum field theory), when one choses a certain interpretation (Feynman diagrams)
-) they violate relativistic energy-momentum relations.
 
351
4
Not as far as I know. To my knowledge, everything speaks against virtual particles:

-) they were never detected
-) they are not needed for theoretical explanations of actual phenomena
-) they only appear within a certain approach (perturbative quantum field theory), when one choses a certain interpretation (Feynman diagrams)
-) they violate relativistic energy-momentum relations.
So I guess they were a good investment around the time of Dirac et al, when they seemed to explain things. Your point 4 suggests they are bad, and ought not be. Which is pretty close to flat-out not exist.
 
157
0
So I guess they were a good investment around the time of Dirac et al, when they seemed to explain things. Your point 4 suggests they are bad, and ought not be. Which is pretty close to flat-out not exist.
can't casimir effect be explained without virtual particles?
 
351
4
byron178
Originally Posted by danR
So I guess they were a good investment around the time of Dirac et al, when they seemed to explain things. Your point 4 suggests they are bad, and ought not be. Which is pretty close to flat-out not exist.​
can't casimir effect be explained without virtual particles?

danR:

Apparently. They even seem to clutter up a good explanation. This latter is new to me.
 
157
0
byron178
Originally Posted by danR
So I guess they were a good investment around the time of Dirac et al, when they seemed to explain things. Your point 4 suggests they are bad, and ought not be. Which is pretty close to flat-out not exist.​
can't casimir effect be explained without virtual particles?

danR:

Apparently. They even seem to clutter up a good explanation. This latter is new to me.
what would happen IF virtual particles didnt exist?
 
253
0

Related Threads for: Virtual particles

Replies
7
Views
3K
Replies
14
Views
4K
  • Posted
Replies
8
Views
2K
  • Posted
Replies
3
Views
2K
  • Posted
Replies
6
Views
2K
  • Posted
Replies
8
Views
3K
  • Posted
Replies
1
Views
1K
  • Posted
Replies
6
Views
2K

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving

Hot Threads

Top