Summer School 2010.6: Quantum Physics

We are at the two thirds mark of our summer school. This week’s lesson: Quanta, Quanta Everywhere.

4 replies on “Summer School 2010.6: Quantum Physics”

  1. pythor says:

    I’m a bit unclear on one thing. It seems from the explanation that a virtual particle from the moon will only have to travel far enough to interact with a virtual particle from the earth. Is that right? So it’s really 1/2 r in the bottom of each piece of the last equation, not r. Of course, the 1/4 part would get calculated into the constant and be meaningless, but it should mean (if I understand) that the force actually works at twice the distance you would expect it to from the virtual particle energy.

    Or am I completely wrong, and if so, can you explain why?

    • Okay, I need to clarify that. The virtual particles don’t interact with other virtual particles.

      Imagine an electron interacts with a proton by emitting a virtual photon. That photon only interacts with particles that have electric charge, and will not interact with other photons (as a particle; there’s still wavelike interference.) The virtual photon continues until it reaches the proton, and not a virtual photon emitted by the proton. That’s why the distance travelled is r. Does that make more sense now?

  2. pythor says:

    Ok, yes. This makes sense, and I think I remember the section where virtual particles were introduced mentioning the difference between charged and uncharged particles interacting. I just forgot.

    Is there any instance where virtual particles are able to interact with each other? Strong force doesn’t require charged particles, right?

    • Strong force does require the strong force’s charge, which is called colour. Gluons have colour, which is why the strong force ultimately ends up with a limited range. They interact with each other. This is what leads to quark confinement. That’s the section Chad asked for clarification about last week.

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