Virtual Particles: How can they be responsible for attractive forces?

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I don't really understand quantum physics, but I would really like to know because I'm going to study it next year. Can someone explain it to me in laymens terms, thanks.
 

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  • #3
naima
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Look http://math.ucr.edu/home/baez/physics/Quantum/virtual_particles.html" [Broken]
 
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I don't really understand quantum physics, but I would really like to know because I'm going to study it next year. Can someone explain it to me in laymens terms, thanks.
It's easy. In QM instead of Newton equations for ri(t) you write a wave (Schroedinger) equation for Ψ(ri,t).

Wave equations have proper frequencies (and thus, proper solutions). QM classifies them and calculates possible transitions from one solution to another.

In addition, there may be superpositions of proper solutions in which no certain frequency exists but everything evolves.

No virtual particles exist. In fact, it is the usual Coulomb and magnetic forces that attract/repell (or better, make interact) de Broglie waves in QM.

EDIT:
They say virtual particles are propagators, so they are not particles but solutions of equations with singular sources (Green's functions). The simplest such an equation is ∆φ(r) = δ(r). Its solution is just a Coulomb potential 1/r. So, instead of speaking of "virtual particles" I speak of electrostatic and magnetic interactions of charges and currents involved.
 
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Fredrik
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Can someone explain it to me in laymens terms, thanks.
Unfortunately no. It's pretty difficult actually, and it's certainly not explained by wave mechanics (the kind of quantum mechanics that you will study in your first QM class). If you want to see an explanation even though you won't understand it, you can look inside https://www.amazon.com/dp/0691010196/?tag=pfamazon01-20 at Amazon. Search for the word "repel", and choose the link that takes you to page 30.

I should also add that there's no reason to think of virtual particles as describing what "really happens" during an interaction. That's certainly not the most popular view around here. This is an answer I wrote to the question "What experiments have verified that virtual particles exist?":
I could answer this with "none of them" as well as "all of them". Virtual particles show up in the mathematics when you expand a certain function in a series and consider each term separately. To say that virtual particles "exist" is equivalent to saying that the individual terms of that series describe what's "really happening", while the sum doesn't. I don't think there's any justification for that. Hence "none of them" is a reasonable answer to your question. However, they are a part of a method to calculate the probabilities of each possible result of any experiment, and these methods work extremely well. Every experiment that involves quantum mechanics in any way is evidence of that. Even the existence of stable atoms is evidence of that. Hence "all of them" is also a reasonable answer to your question.

Personally, I don't think of virtual particles as a description of what's really happening. I think of them as a part of the easiest way to do calculations.
 
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