Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: katieHaylor on 15/09/2017 09:46:58

Title: Do virtual photons exist?
Post by: katieHaylor on 15/09/2017 09:46:58

Donald says:

Virtual photons mediate both the electrical and magnetic forces. Here are my problems with the concept:
1. Neutral atoms have no net electrical charge, but if the nucleus is giving off these virtual photons, every single one has to be absorbed by one of its orbiting electrons which is possible, but every electron has to have its virtual photons absorbed by the nucleus, given that just one excess electron would give it a charge that extends to infinity via the inverse square law. How is that coordinated?
2. Magnetic lines of force must suggest that these virtual photons must be able to be focused, or create an interference pattern. How is that done? And how does this photon make either just electrical force or just magnetic force in different situations being the undifferentiated thing it is?

Can you help?

Title: Re: Do virtual photons exist?
Post by: jeffreyH on 15/09/2017 12:57:50

The answer involves a variety of subjects. Including the uncertainty principle, Feynman diagrams, perturbation theory and quantum field theory. In Feynman diagrams virtual particles are exchanged between real particles as a means to account for observed behavior. The uncertainty principle limits the lifetime of the virtual particles due to the value of the energy they have 'borrowed' from the vacuum. As for perturbation theory and quantum field theory, I will leave those to others to explain.

Title: Re: Do virtual photons exist?
Post by: jeffreyH on 15/09/2017 18:03:50

An interesting page on a background to perturbation theory is on dummies.com. This is for a book on string theory. It is well worth just reading this excerpt.
http://www.dummies.com/education/science/physics/perturbation-theory-string-theorys-method-of-approximation/

Title: Re: Do virtual photons exist?
Post by: Bill S on 15/09/2017 18:39:59

Matt Strassler says this of virtual particles at:

https://profmattstrassler.com/articles-and-posts/particle-physics-basics/virtual-particles-what-are-they/ 

“The best way to approach this concept, I believe, is to forget you ever saw the word “particle” in the term. A virtual particle is not a particle at all. It refers precisely to a disturbance in a field that is not a particle”.

The whole thing is worth reading.

Title: Re: Do virtual photons exist?
Post by: yor_on on 20/09/2017 02:46:22

Call it indeterminacy instead of 'virtual photons'. It's easier on the mind. It's a mathematical concept that loses its meaning when thought of as 'real'.

Although...

It depends on what one mean by virtual too.
https://www.scientificamerican.com/article/are-virtual-particles-rea/

It's that time/energy relation again. Though, if it exist, it exist, and by that definition it's not really 'virtual', is it?
==

And this paper may shred some light on why I prefer to think of it as 'indeterminacy' instead of 'virtual particles'. http://math.ucr.edu/home/baez/physics/Quantum/virtual_particles.html