Posted: Oct 19, 2011 2:17 pm
by twistor59
zaybu wrote:
twistor59 wrote:On subject of the "are virtual particles actually physical entities" discussion that was taking place a few pages back, Matt Strassler has just posted a beautifully clear exposition of what virtual particles are/are not. I urge anyone who things that real paticles interact by tossing virtual thingies back and forth to read it.

Okay, so he has an aversion for the word "particle" and calls it a "ripple". Big deal.

Well it’s a little more than that:
Matt Strassler wrote:
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.

Matt Strassler wrote:
Physicists often say, and laypersons’ books repeat, that the two electrons exchange virtual photons. But those are just words, and they lead to many confusions if you start imagining this word “exchange” as meaning that the electrons are tossing photons back and forth as two children might toss a ball.

Hmm yeah like this animation.

They do indeed lead to many confusions, as evidenced by this physicsforums question:

I am told that the space surrounding me is filled with virtual particles, popping into and out of existence. I could believe that they exist for such short times and at such low energies that sophisticated equipment is needed to detect them. However, a collision between even 1 virtual electron and a starship going 0.99999999999999999999999999 c would have a significant effect on the ship because in the ships frame of reference the electron would have a large kinetic energy. Since all reference frames have equal claim to be "at rest", why are we not constantly bombarded by virtual particles that may be at rest relative to the afore mentioned starship, but would tear us apart?

Virtual particles popping in and out of existence :o
The poster there was quite right to ask that question given the horseshit pictures that are promulgated by the use of this sloppy terminology. Had he known how the theory is really formulated though, the question might have rather included the phrase "a collision between even 1 momentum integral and a starship going 0.99999999999999999999999999 c" :lol: