Virtual Particles: How They Work

[asimov42]

Folks,

I have a question about virtual particles. I recently read in a Scientific American article which says that "virtual particles are indeed real particles. Quantum theory predicts that every particle spends some time as a combination of other particles in all possible ways. These predictions are very well understood and tested."

I assume, from the above, that by "spending time as a combination of other particles", the author means that every particle is in a superposition, with some chance of appearing as a combination of other (virtual) particles, which can't be observed because they're virtual? E.g. a photon sometimes splits into a virtual electron/positron pair, and then reforms the original photon...

So, assuming the above, my question is: what govern the amount of time / probability distribution for a particle appearing as other types of particles? Is it something intrinsic to the type of particle itself? Or does it have to do with the energy of the particle? For example, if I were to say, accelerate an electron by a significant amount, would that affect the amount of 'time' (for lack of a better word) that it spends as other, heavier particles?

Not sure if the above is very clear, but any suggestions would be helpful. Thanks.

 

[Demystifier]

I recently read in a Scientific American article which says that "virtual particles are indeed real particles. Quantum theory predicts that every particle spends some time as a combination of other particles in all possible ways. These predictions are very well understood and tested."

I think it is simply wrong.

 

[genneth]

I think it is simply wrong.

Seconded. Virtual particles and real particles are very easy to tell apart. You can't ever observe a virtual one...

 

[BryanP]

Maybe they're saying that virtual particles are not literally "fake" particles, but other particles that are actually part of the standard model

 

[malawi_glenn]

Each virtual particle has its real conterpart, which can be detected.

 

[asimov42]

The original article was making the point that virtual particles are not just used for bookkeeping, but do, in fact 'exist' (although they are unobservable).

I was wondering more about the amount of time one particle spends as a combination of other particles. E.g. (again from the article) the measured mass of the Z boson was slightly different that that predicted by the standard model, and this difference was later attributed to the time the Z spends as a virtual top quark. My question is, basically, what governs this relationship? I.e. how do we 'know' how much time the Z should spend as a virtual top quark etc.? (I think the use of the word time here might not be entirely accurate)

Thanks all.